Mo hinh hoa MT

8/7/2019 Mo hinh hoa MT

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http://www.ebook.edu.vn


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Knh mong sng gp kin ca tt c bn c.

Nhngng gp qu bu ca bn c sgip cc tc ginng cao cht lng gio trnh ny.

Gio trnh ny trnh by c s l lun v thctin xy dng, ng dng m hnh ton phc v chocng tc bo v mi trng. Cc khi nim c bnnh m hnh, m hnh mi trng, m hnh ha biton bo v mi trng khng kh, mi trng ncmt, nc di t c trnh by. Trong gio trnh

cng dnh s lu c bit cho nhng ng dng cth trong bi ton bo v mi trng trn t ncchng ta.

Gio trnh hng ti i tng l sinh vin, hcvin cao hc chuyn ngnh mi trng v mt sngnh lin quan, cng nh ging vin, nghin cuvin ti cc trng i hc v vin nghin cu.



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Bn quyn @ 2008 - Bi T Long, tin skhoa hc,

Li cam n

Gio trnh ny ra i c l nhsng vin v h trca qu thy cng nghip m tc gi c dp lm vic v cng tc.

Tc gi xin chn thnh cm n Lnh o Vin Mi trng v Ti nguyn,i hc Bch khoa, i hc quc gia TP. H Ch Minh, i hc nng lmTP. H Ch Minh, i hc Khoa hc Hu, i hc bn cng Tn cThng TP. H Ch Minh, i hc K thut Cng ngh TP. H Ch Minh,i hc Yersin TP. Lt mi tc gi tham gia ging dy cho sinhvin, hc vin cao hc chuyn ngnh mi trng.

Tc gi cng gi li cm n chn thnh n cc thnh vin Phng Tin hcMi trng, Vin Mi trng v Ti nguyn, i hc Quc gia Tp. HCh Minh, cc thnh vin khc ca nhm ENVIM tham gia thc hincc phn mm gn vi m hnh.

Tc gi by t li cm n chn thnh n cc thy phn bin dnh

nhiu thi gian c v ng gp kin nhm nng cao cht lng cati liu ny.

Cui cng tc gi xin cm n cc hc tr ca mnh tham gia rt nhittnh phn x l s liu, nhp s liu cng nh kim tra phn mm, cngnhiu h trkhc nng cao gi tr v mt thc tin cho gio trnh ny.



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Li noi auM hnh ha vi s trgip ca cng ngh thng tin trong thi i ngynay tr thnh mt nhnh quan trng ca khoa hc hin i v l mt

cng c rt mnh nhn thc th gii xung quanh. Nghin cu m hnhha v ng dng trn my tnh mra nhng chn tri mi nhn din s

ph thuc ca tin hc vi ton hc v cc ngnh khoa hc khc c tnhin ln x hi.

Khi nim m hnh chng ta lm quen t thi thu. chi t,my bay hay chic tu l nhng tr chi yu thch ca con trai; bp b,con gu bng l nhng tr chi khng th thiu ca b gi. Trong nhn

thc ca tr em, trong qu trnh nhn bit th gii bn ngoi, nhng chi nh vy v thc cht l cc m hnh ca th gii thc. tui thiunin i vi nhiu em th cc tr chi lego, cc m hnh lp rp t, my

bay, tu thy gn ging vi thc t trnn quyt nh trong vic lachn ngh trong tng lai.

Nh vy m hnh l g ? Ci g chung gia mt bn l chic tu tr chivi hnh vc th hin trn mn hnh my vi tnh, th hin mt m hnhton hc tru tng ? C mt iu l ging nhau: trong c hai trng hpchng ta c hnh nh ca mt i tng thc, thay th bn gc no c thc hin vi tin cy v c th no . Ni mt cch khc, mhnh l biu din i tng di mt dng no , khc vi dng thc can.

Trong hu ht cc ngnh khoa hc v thin nhin, v th gii sinh vt hayv c, v x hi, vic xy dng v s dng m hnh l mt th v kh rtmnh nhn thc x hi. Cc i tng v qu trnh thc thng rt a

dng v phc tp cho nn cch tt nht nghin cu chng l xy dngm hnh. M hnh c xy dng ch gi li mt s mt ca hin thc v



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v th n n gin hn. Kinh nghim pht trin khoa hc trong nhiu thk khng nh tnh ng n ca phng php tip cn nh vy.

Gio trnh ny hng ti i tng sinh vin chuyn ngnh mi trng,cng nh mt s ngnh c lin quan. Bn cnh gio trnh ny cng c

ch cho hc vin trn i hc cng nh ging vin, nghin cu vin thuccc cso to v nghin cu trong nc.

Gio trnh ny c bin son da trn ti liu ging dy mn hc ny vocc nm 2005 - 2008 cho sinh vin v hc vin cao hc ti Vin Mitrng v Ti nguyn, mt s trng i hc khc. Trong gio trnh nytc gi c gng bm st thc tin ca t nc cng nh chng trnho to ngnh mi trng. D c nhiu c gng nhng chc chn gio

trnh ny vn khng th trnh khi nhng tn ti v hn ch. Tc gi rtmong nhn c sng gp kin ca qu ng nghip cng nh bnc gn xa c quan tm ti ng dng m hnh ha trong qun l mitrng cng nh trong nghin cu mi trng. Gp xin gi va [email protected], in thoi 0918017376 hoc theo a ch trntrang Web: www.envim.com.vn.

TP. H Ch Minh, thng 6/2008

Tc gi: TSKH. Bi T Long



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DANH MUC CAC T VIET TATBOD Nhu cu oxy sinh ha

C Cacbon

CAP Computing for Air Pollution Phn mm tnh ton nhim khng kh

CBOD Nhu cu oxy sinh ha cc hp cht cacbon

COD Nhu cu oxy ha hc

DIP Phtpho v cho tan

DO Oxy ha tan

DOM Cht khong ha tan

DON Nithu cha tan

DOP Photpho hu cha tan

EC dn in

ENVIM ENVironmental Information Management software phnmm qun l mi trng

ENVIMAP ENVironmental Information Management and Air

Pollution estimation Phn mm tnh ton m phng nhim khng kh

ENVIMQ2K Phn mm m phng cht lng nc knh sng c ngdng GIS

GIS H thng thng tin a l

GIS Geographic Information System H thng thng tin a

l



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GMS Groundwater Modeling System phn mm m phng

nc di t

IN Nitv c

IP Photpho v v

NBOD Nhu cu oxy sinh ha cc hp cht nit

NH4 Ammonia

P Phtpho

PO4 Phtphat

QUAL2K Phn mm m phng cht lng nc knh sng ca M

SBOD Nhu cu oxy ca bn lng

SS Cht rn llng

TDS Tng cht rn ha tan

TN Tng nit

TN Tng nit

TP Tng photpho

.



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MUC LUCLi cm n ........................................................................................................ iiiLi ni u .........................................................................................................v Danh mc cc t vit tt....................................................................................... viiMc lc ........................................................................................................ix

MU ......................................................................................................... 1Tnh cp thit ca mn hc................................................................................. 1Mc tiu ca mn hc......................................................................................... 2Ni dung mn hc............................................................................................... 2Phng php, cng cc s dng.................................................................. 5Gii hn ca phng php m hnh.................................................................... 5

CHNG 1.TNG QUAN V M HNH HA MI TRNG ..................... 71.1. M hnh vt l v ton hc ..........................................................................71.2.Vai tr ca m hnh...................................................................................... 91.3.M hnh nh l cng c qun l v nghin cu mi trng .....................131.4.S phn loi m hnh v cc nguyn l m hnh ha ................................ 171.5. M hnh ha mi trng v s phn loi chng........................................ 19Cu hi.............................................................................................................. 25Ti liu tham kho ............................................................................................ 25

CH NG 2. NHNG KHI NIM C BN CA M HNH HAMI TRNG ............................................................................. 26

2.1.Cc giai on cbn ca qu trnh xy dng m hnh mi trng..........262.2. Cc thnh phn trong qu trnh m hnh ha mi trng..........................372.3.S phn loi m hnh mi trng ............................................................. 392.4.Cc nguyn l cbn p dng trong xy dng m hnh mi trng........ 45Cu hi.............................................................................................................. 46Ti liu tham kho ............................................................................................ 47

CH NG 3. CC YU T KH TNG NH HNG LN SPHT TN CHT NHIM KHNG KH .............................. 48

3.1. S pht tn ca cht kh trong kh quyn ................................................. 483.2. Cc iu kin nh hng n s pht tn ca kh trong kh quyn ........... 513.3. n nh ca kh quyn.......................................................................... 56Cu hi.............................................................................................................. 69Ti liu tham kho ............................................................................................ 70



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CHNG 4. M HNH HA NHIM KHNG KHI THEOPHNG PHP GAUSS.71

4.1.Phng trnh cbn m t s truyn ti v khuch tn cht nhim .......714.2.M hnh Gauss tnh ton lan truyn cht nhim khng kh ....................754.3.M hnh pht tn nhim khng kh ISC3................................................89

4.4.Bi tp ng dng m hnh Gauss .............................................................103Cu hi............................................................................................................112Ti liu tham kho .......................................................................................... 112

CHNG 5. M HNH HA NHIM KHNG KH THEOPHNG PHP BERLIAND....................................................113

5.1.Cc phng php tip cn chnh trong vic m tkhuch tn kh quyn................................................................................ 113

5.2. M hnh Berliand tnh ton lan truyn cht nhim trong kh quyn.....1185.3. Cc bc tng ho tnh ton theo m hnh pht tn

nhim khng kh....................................................................................1255.4.M hnh pht tn nhim khng kh Sutton............................................1355.5.Phng php tnh ton nng trung bnh..............................................1405.6. M hnh Berliand k thut .......................................................................1445.7.Bi tp ng dng m hnh Berliand .........................................................151Cu hi............................................................................................................ 164Ti liu tham kho .......................................................................................... 165

CHNG 6. MT S KIN THC C BN LIN QUAN TIM HNH HA CHT LNG NC................................... 166

6.1.Hin tng lan truyn cht trong mi trng nc .................................1666.2.Chuyn ti ................................................................................................ 1706.3.Khuch tn / phn tn...............................................................................1736.4.S phn ..................................................................................................1976.5.M hnh ha cht lng nc h ............................................................. 2006.6.Bi tp ng dng ...................................................................................... 214Cu hi............................................................................................................ 219Ti liu tham kho .......................................................................................... 219

CHNG 7. M HNH STREETER PHELPS M PHNG

CHT LNG NC TRN KNH SNG ...........................2207.1.Nhu cu oxy sinh ho (BOD)...................................................................2217.2. S nhim do cc cht hu c................................................................ 2237.3. Cc im lu v nhu cu oxy sinh ha .................................................2257.4.S oxy ha cc hp cht ca nit............................................................. 2277.5. ng cong din tin oxy ha tan (ng cong lm) .............................2307.6. M hnh Streeter Phelps........................................................................2327.7. Bi tp ng dng m hnh Streeter ..........................................................242Cu hi............................................................................................................ 252

Ti liu tham kho .......................................................................................... 253CHNG 8. M HNH DNG CHY V LAN TRUYN CHTCHO KNH SNG.....................................................................253



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8.1. Phng trnh vi phn ca dng chy v lan truyn cht ..........................2538.2. Phng php s gii phng trnh vi phn ca dng chy

v lan truyn cht trong sng...................................................................2628.3.Gii s phng trnh dng chy v lan truyn cht cho knh sng.......... 274Cu hi275

Ti liu tham kho .......................................................................................... 276CHNG 9. M PHNG CHT LNG NC BNGPHN MM QUAL2K............................................................... 276

9.1. Tng quan v m hnh QUAL2K ............................................................ 2769.2. S phn on trong QUAL2K ................................................................. 2779.3 Cn bng lu lng.................................................................................. 2799.4 Cc c tnh thu lc................................................................................ 2819.5 Thi gian di chuyn ................................................................................. 2889.6 Cng thc tnh h s phn tn theo hng dng chy ............................. 288

9.7 M hnh nhit ...................................................................................... 2899.8 M hnh tnh ton cho cc phn t ........................................................... 3049.9 Phn mm ENVIMQ2Kng dng GIS m phng cht lng

nc knh sng ........................................................................................ 3279.10.Bi tp ng dng phn mm ENVIMQ2K m phng cht lng

nc knh sng do nhiu ngun x thi .................................................. 359Cu hi............................................................................................................ 380Ti liu tham kho .......................................................................................... 380

CHNG 10. M HNH HO NC DI T........................................ 381

10.1. Tng quan v cc m hnh nc di t.............................................. 38110.2. iu kin u......................................................................................... 38710.3. iu kin bin........................................................................................ 38810.4. Mt s phn mm c s dng rng ri ..............................................39110.5. ng dng phn mm MODFLOW v MT3DMS tnh ton

m phng lan truyn nittrong nc di t - ly TPHCMlm v d nghin cu ............................................................................. 393

Cu hi............................................................................................................ 427Ti liu tham kho .......................................................................................... 427

B NG .....................................................................................................429HNH .....................................................................................................432 BNG TNH I NVO NNG ...................................................... 444



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TONG QUAN VE MO HNH HOAMOI TRNGHin nay khng c mt lnh vc nhn thc no m ngi ta khng ni nm hnh. Trong ngha rng, m hnh c hiu l mt cu trc c xydng trong t duy hoc thc tin, cu trc ny ti hin li thc tdngn gin hn, cng thc hn v trc quan hn. Phn trnh by di y slm sng t hn v m hnh v m hnh ho mi trng.

1.1. MO HNH VAT LY VA TOAN HOC

Trong lch s pht trin con ngi tng s dng m hnh. M hnh l

nhng bc tranh n gin v thc t v l cng c gii quyt nhiu vn .Dnhin, m hnh s khng bao gicha ng tt c cc c tnh ca hthng thc, bi v, chnh n khng phi l h thng tht. Nhng iu quantrng vic m hnh cha ng tt c cc c tnh c trng cn thit trong

phm vi ca vn cn gii quyt hay m t.

ngha thc tin ca vic s dng m hnh c lc minh ha tt nht quanhng v d trong thc t. Trong nhiu nm, ngi ta s dng cc mhnh vt l ca con tu xc nh mt nghing, gip con tu c c s cn

bng trong nc. M hnh vt l nh vy s c hnh dng v mt s thng schnh ging con tu tht s, nhng n khng cha tt c cc chi tit chnghn nh: s trang b my mc, cch b tr ca cabin, v.v Nhng chi titnh vy th khng lin quan n mc ch ca m hnh cn nghin cu.

Nhng m hnh khc ca con tu p ng cc mc ch khc: cch b tr cacc cabin khc nhau, s cc ng dn...

T , chuyn gia hng u v m hnh mi trng ngi an MchJorgensen M.E. /[6]/ cho rng m hnh mi trng phi mang nhng ctnh lu n kha cnh qun l hay vn mang tnh khoa hc, ychnh l iu m cc nh nghin cu mong mun. Mi trng l mt h

Chng

1



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Giao trnh Mo hnh hoa moi trng10

1.M hnh l mt i tng nh, thng c xy dng theo t l, n mt mt vi i tng thc t trong t nhin.

2.M hnh l mt mu th hin mt s vt cn cha c xy dng trn

thc t, c xem nh l k hoch (trn thc t s ln hn mu) v sc xy dng.

3.Thut ng model c th l mt mu c s dng trc nghim vng php hai mu cu c cu trc vn phm tng phn nhau.(Noam Chomsky)

4.Thut ng modelc thc dng nh mt kiu mu thit k camt i tng c th. V d c th ni chic xe ca anh ta l mu xeca nm ngoi.

5.Thut ng model c thc dng cho i tng l ngi tiu biucho mt hay nhiu tiu ch khc nhau.

6.Thut ng model c th l ngi hay vt th phc v cho ha shayngi chp hnh ngh thut.

7. Thut ng model c th dng ch ngi c ngh nghip l trnh din thitrang.

Nhng khi nim theo danh sch trn l cha hon ton y , tc giStehr thm vo mnh sau:

1. M hnh l cng c tt

2. M hnh ton hc cn tt hn.

Cc khi nim trn mt phn no tr li cu hi v vai tr v chc nng cam hnh trong khoa hc. Nu ai c gng a ra mt mu s chung nhtcho cc m hnh, th chnh l chc nng quan trng nht ca chng l s

gim thiu phc tp ca phm vi yu cu. Ty theo bi cnh c th, trongtng lnh vc khoa hc c ng dng m hnh s c nhng phm vi yu cuc thi vi tng m hnh. xc nh phm vi gii hn ca tng m hnhchng ta cn xc nh bt u tu, cc vn quan trng no cn quantm l g, chng ta mong mun tm kim li gii p g v nh gi nhng ligii c th tm thy c nh th no.

din ra s tranh lun gia cc nh khoa hc trn th gii v vai tr chthc ca m hnh trong khoa hc. Theo quan im ca nh vt l ngi PhpPierre Duhem /xem [5], trang 3/ m hnh trong khoa hc ch l mt cng c gii thch v l thuyt v c thc loi b mt khi mt l thuyt khc



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Chng 1 TONG QUAN VE MO HNH HOA MOI TRNG 11

c pht trin. p li nh vt l ngi Anh Campell /xem [5], trang 3/ chorng vai tr ca m hnh vt qu gii hn nh Duhem ch ra, c th l mhnh l mt cng c trgip nghin cu khoa hc m hnh l mt phn thityu (ca l thuyt), khng c n l thuyt shon ton khng c gi tr

Theo quan im ca Stehr khng tn ti phng php chung cho m hnhha. Tuy nhin, c hai thuc tnh sau y thng c quan tm trong qutrnh m hnh ha, l:

- Cht lng m hnh c cng cu trc- Kt qunh lng c to ra t m hnh.

Trong phn minh ha cho lp lun v quan im khoa hc ca mnh Stehr

a ra mt lot cc v d m hnh cng qu trnh m hnh ha din ratrong cc lnh vc khc nhau nh m hnh x hi, m hnh kinh t, mhnh kh hu nh mt m hnh kt ni x hi vi thin nhin /[5]/.

Cc nh khoa hc Nga coi m hnh l cng c gip d bo cng nhtnh ton trc nhng hu qu c th trong thc thi cc d n kinh t v

pht trin x hi. Trong thc t, bi ton c quan tm su sc canhiu d n l a ra c cu tr li cho cu hi : iu g sxy ranu , v do vy bi ton d bo hu qu c th xy ra do vic thc

hin tc ng ny hay tc ng khc l bi ton trung tm ca nhiunghin cu. D bo ny c xy dng trn nhng tri thc vc trngca cc qu trnh xy ra trong thin nhin, qui lut pht trin x hi vsnh hng ln nhau trong mi quan h tng h ny.

Cc giai on cn thit cho nghin cu khoa hc mt qu trnh bt kdin ra trong thin nhin, trong c d bo s pht trin ca n l :

- Xy dng m hnh ca qu trnh cn nghin cu,- Pht biu nhng gii hn c trng cho qu trnh c nghin cu

theo ngn t xy dng m hnh, pht biu mc tiu ca nghin cu.

Vic thc hin cc giai on k trn cng vi nhau dn ti vic xy dngm hnh cho qu trnh c nghin cu. Cn lu rng m hnh c th cdng hnh thc (c cho bi mt s h thc h ton hc), cng nh chodi dng cu trc m t ngha l c cho di dng mt s qui lutchnh quan st c. Thc t ch ra rng nu chng ta c cng nhiu,cng y thng tin v cc qu trnh cn phn tch th vic d bo trong

phm vi thi gian cho cng chnh xc by nhiu cng nh khong thigian d bo cng ln th sai s d bo cng tng theo.



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Tt nhin, vic xy dng m hnh khng th l mt bi ton n gin. utin, cn phi c kh nng v cc phng tin (vt cht v kthut). Thhai cn phi hiu bit cc qui lut bn trong s pht trin x hi, bitc s tin trin cc mc tiu x hi t xc nh dng ny haydng khc tc ng ca con ngi ln mi trng. Thba cn phi hiunh hng ca nhng thay i c th trong mi trngv cc qui lut

pht trin ca x hi. Mi bi ton c pht biu trn u l nhng biton phc tp. Kh nng gii tng bi ton ph thuc vo mc tiu nghincu c t ra cho nghin cu, ngha l ph thuc vo tiu ch nh gicc hu qu ca nhng thay i ca mi trng di tc ng ca cc qutrnh x hi.

Mt h thin nhin hay x hi phc tp bt k c thc m t bng nhiuphng php khc nhau. tng m hnh ha cho php xt cc c trngkhc nhau ca h cng nh tham s ha cc d liu thc nghim bng cc

phng php khc nhau. Ngoi ra, trong bt k mt hin tng thin nhinphc tp no lun c mt mc khng xc nh tng i cao lin quan tikin thc v bn cht ca hin tng, v cc mi quan h nhn-qu, v cctham s ban u ca cc d liu. Trong nhng iu kin nh th ny victhit lp mt m hnh chnh xc trnn v ngha. iu quan trng phihiu rng phc tp ca m hnh phi tng ng vi mc chnh xc cad liu ban u v kh nng tnh ton ca my tnh hin ti (tc my tnh,kh nng ca b nh, tc xut mn hnh, kh nng ca ngi nghin cux l v t duy cc kt qu tnh ton nhn c). Chnh v nhng nguynnhn ny nn ngi nghin cu thng chn m hnh tng i n gin chocng vic tnh ton thc t. Vin sSamarsky A.A. vit: Ngi nghincu m hnh thng xuyn nm gia hai p lc: phc tp ha v chnhxc. Mt mt, m hnh do anh ta xy dng phi n gii tkha cnh tonhc c thnghin cu n bng cc cng cang c, v kt qu do ngii ha mt sgi thit khng b mti tnh xc thc ca vn . Trongpht biu ny ca vin sSamarsky A.A. th hin mt nguyn l m hnh haton hc mt m hnh ton bt k phi c phc tp ti u, cn v gii quyt nhim vc t ra

Tm li, m hnh ha cc qu trnh v hin tng xy ra trong x hi vthin nhin c tha nhn nh mt cng c mnh gip hiu bit su hn

bn cht ca t nhin v gip loi ngi nhn c thng tin qu gi v thgii thc. Thng tin ny tip tc thc y s pht trin cc phng phpmi gii quyt cc bi ton khoa hc cng nh lm c s thng qua ccquyt nh qun l c th.



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1.3. MO HNH NH LA CONG CU QUAN LY VA NGHIEN CU MOITRNG

Tm quan trng ca vic s dng m hnh trong cng tc qun l mi trng

c minh ha trong Hnh 1-1. S th ha v pht trin cng ngh tcng mnh vo mi trng. Nng lng v cc cht nhim c pht thi, xthi vo mi trng sinh thi, v ti y chng gy nn s pht trin nhanhchng ca to hay vi khun, ph hoi cc loi khc dn ti lm thay i cutrc sinh thi. Mt h sinh thi bt ku rt phc tp. Chnh v vy vic tinon cc tc ng ln mi trng l mt nhim v kh nng n. Chnh v l dony bin m hnh trthnh mt cng c c ch bi v m hnh l bc tranh

phn nh thc t. Vi kin thc mi trng sinh thi y v hon chnh, c

th rt ra c nhng c trng ca h sinh thi lin quan n cc vn nhim v qua nghin cu hnh thnh nn nn tng ca m hnh mi trng.

Nhc ch ra Hnh 1-1, kt qu m hnh c thc s dng la chnk thut mi trng ph hp nht cho gii php cc vn mi trng c

bit, hay cho vic xy dng cc b lut khung gip gim thiu hay kim sot nhim.

Hnh 1-1. Mi lin h gia khoa hc mi trng, sinh thi, m hnh hami trng sinh thi, qun l mi trng v cng ngh mi trng



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Hnh 1-2. tng th hin vai tr cc m hnh mi trngtrong qun l mi trng

Hnh 1-1 trnh by nim mu ca m hnh mi trng c s dngnh l cng c qun l trong nm 1970. Qun l mi trng ngy nayphc tp hn v phi p dng cng ngh mi trng, cng ngh sch hnnh l s la chn a ra cng ngh v k thut sinh thi(ecotechnology). Cng ngh sau cng c p dng gii quyt cc vn nhim ngun khng im hay lan truyn c ngun gc chnh t nngnghip. Hnh 1-2 /[6]/ c gng minh ha bc tranh phc tp hn v qunl mi trng ngy nay.

M hnh l nhng cng cc s dng rng ri trong khoa hc. Mt mt,cc nh khoa hc thng dng cc m hnh vt l thc hin th nghim

bn ngoi (situ) hay trong phng th nghim hn ch s xo trn t tintrnh khng lin quan n vic nghin cu.Hemostatsc s dng olng s pht trin ca to nh l chc nng ca nng dinh dng. Vngtrung tm trm tch c kim tra trong phng th nghim iu tra stng tc ln nhau gia mi trng nc v cht trm tch trnh s xotrn cc thnh phn h sinh thi khc. Cc chui phn ng c s dng

tm ra t l ca cc tin trnh ha hc.v.v



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Bn cnh , m hnh ton hc ang c p dng rng ri trong khoahc. nh lut Newton l m hnh ton hc tng i n gin vnhhng ca trng lc trn cth, nhng n khng tnh n lc ma st, nhhng ca gi, v.vV bn cht, m hnh mi trng th khng khc sovi cc m hnh khoa hc khc, thm ch khng phc tp nh nhiu mhnh s dng trong vt l ht nhn trong nhng thp nin qua (nhng mhnh ny c l thm ch phc tp hn cc m hnh mi trng).

ng dng m hnh trong mi trng trnn ph bin, nu chng tamun hiu s vn hnh ca mt h thng phc tp nh h sinh thi. Thtkhng n gin kho st nhiu thnh phn v tc ng trong mt hsinh thi m khng s dng m hnh nh l cng c tng hp. Tc ng

qua li ln nhau ca h thng c l khng nht thit l tng cc tc ngring r; iu ny ng rng cc tnh cht ca mt h sinh thi nh l mth thng khng thc phn nh nu khng s dng m hnh ca hthng hon ton.

Do , khng c g ngc nhin khi cc m hnh mi trng c sdng ngy cng nhiu trong sinh thi hc ni ring v mi trng nichung, nh mt cng c hiu v tnh cht ca h sinh thi. ng dngny phn nh r rng nhng thun li ca m hnh nh l cng c hu

dng trong mi trng mi trng; n c th tm tt theo nhng imdi y:

1) M hnh l nhng cng c hu ch trong kho st cc h thng phc tp.2) M hnh c thc dng phn nh cc c tnh ca h sinh thi.3) M hnh phn nh cc l hng v kin thc v do c thc

dng thit lp nghin cu u tin.

4) M hnh l hu ch trong vic kim tra cc gi thit khoa hc, v mhnh c th m phng cc tc ng bn trong ca h sinh thi, dngn so snh vi cc quan st.

Tuy nhin, iu chc chn l kim tra tnh ng n s dng m hnh mitrng phc tp hn kim tra cc ngnh khoa hc khc. Chng hn, vinhiu ngnh khoa hc khc mi tng quan c tm thy y gia haihay nhiu yu t thay i bng vic s dng thng k l . Sau ny, mitng quan c kim tra trong vi trng hp b sung lm tng tnh

chc chn ca khoa hc. Nu kt quc chp nhn, mi tng quan ddng c s dng a ra nhng tin on v c kim tra liu s



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tin on l ng hay sai. Nu mi tng quan c kim chng, ngi tachp nhn s dng rng ri mi tng quan tm c.

Theo /[6], trang 456/ khng c s khc bit v mt nguyn tc gia hai

nhm m hnh khoa hc v qun l mi trng. Tuy nhin cc m hnhqun l mi trng c mt sc im ring. Thc vy, bi ton qun lc thc pht biu nh sau: nu mt s bin ngoi sinh (hay hm iukhin) thay i th iu ny s gy nh hng th no ti h sinh thi ?M hnh qun l c s dng tr li cho cu hi ny, ni cch khcm hnh qun l c dng d bo, xem khi hm iu khin thay ith h sinh thi (mi trng sinh thi) s thay i th no. Lu rng hmiu khin l mt hm thay i theo khng gian v thi gian.

Thut ng chc nng kim sot c dng ni ti hm iu khin. Trnthc t, c th kim sot c hm ny v d nh lng nhin liu ctiu th, iu chnh mc nc trn sng bng p chn, lu lng ncthi hay chnh sch nh bt c.

Mt s m hnh qun l mi trng c mang tn m hnh kim sot mitrng. Cc m hnh ny khc cc m hnh khc bi hai ni dung chnhsau y:

1.M tnh lng cho cc qu trnh cn kim sot;

2. M t mc tiu thc thng qua cc hm ton hc v bt buc c phnnh gi kt qut c.

S khc nhau gia m hnh qun l v m hnh kim sot c thc minhha bi v d tnh ton pht tn nhim khng kh. Khi chng ta chn cc

phng n tnh ton khc nhau, c ngha l chng ta hnh thnh cc kch bn(cho m hnh chy). Trong s cc kch bn ny ta chn kch bn ph hpvi chnh sch pht trin kinh t - x hi nht. Khi m hnh c s dngnh mt m hnh qun l m khng phi l m hnh kim sot. Chng ta

bin m hnh ny thnh m hnh kim sot khi chng ta mun t c mc nng cho php mt ngng xc nh no .

Cng m hnh nhng l m hnh nghin cu khi ta mun tm s phthuc gia nng cc t vo cc yu t kh tng cng nh cc tham sk thut ca ng khi.

1.4. S PHAN LOAI MO HNH VA CAC NGUYEN LY MO HNH HOA

Trong cc lnh vc ng dng ngi ta phn bit cc dng sau y ca mhnh tru tng:



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1. M hnh ha truyn thng (trc tin l cc m hnh trong vt l lthuyt, trong chc, ha hc, sinh hc v mt s khoa hc khc) khngc mi lin hc bit no vi cc thit b k thut tin hc.

2. Cc m hnh tin hc v php m hnh ha c ng dng trong cc hthng thng tin.

3. Cc m hnh th hin bng li (li ni, ch vit)

4. Cc m hnh my tnh c chia thnh

4.1. Loi m hnh s dng cng c lp trnh (son tho code, csdliu, processor bng, s dng cng c vin thng);

4.2 Loi m hnh my tnh gm

4.2.1 M hnh tnh ton (m phng)

4.2.2 M hnh hin th hin tng v qu trnh (m phng ha)

4.2.3 M hnh s dng cng ngh cao c hiu nh cc chngtrnh ring kt ni vi cc h thng o: cm bin, u d,...(thng trong ch thi gian thc).

Nh vy, c th thng nht phn loi cc m hnh tru tng nh sau:

1)M hnh bng li (ch vit). Cc m hnh ny c trnh by didng mt dy cc xut da trn ngn ng t nhin v dng m tmt lnh vc thc t c th (v d nh lut ng st, bin bn cacng an)

2)M hnh ton - bao hm mt lp rt rng ln cc m hnh quen thuc(da trn ngn ng hnh thc vi cc qui tc hu hn) s dng phng

php ton hc rt a dng. V d c th xem xt m hnh ton gia cchnh tinh. M hnh ny gm mt h cc phng trnh phc tp m tcc qu trnh vt l phc tp din ra trong nhn cc hnh tinh.

3)M hnh thng tin mt l p cc m hnh quen thuc m t cc qutrnh thng tin (s xut hin, truyn, bin i v s dng thng tin)trong cc h c bn cht khc nhau.

S khc bit gia cc m hnh bng li, ton hc v tin hc ch l tngi: hon ton c th coi cc m hnh thng tin l mt l p con ca mhnh ton. Tuy nhin, bi v ngy nay tin hc l mt ngnh khoa hc

c lp tch khi ton hc, vt l v vn hc cng nh cc ngnh khoa



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hc khc cho nn vic xp cc m hnh tin hc thnh mt lp ring bit liu cn thit.

Chng ta xem xt nhng nguyn l cbn m hnh ha phn nh kinh

nghim c c kt trong thi gian qua:1.Nguyn l thng tin. Vi s thiu vng hon ton ca thng tin v

h thng c cn xy dng m hnh l khng th. Bn cnh nu sy thng tin v h thng s khin vic m hnh ha n mt i ngha cn thit. Do vy, tn ti mt mc ti hn cho nhng thng tintin nghim v h thng (mc thng tin), trong trng hp tc mc ny, c th xy dng c m hnh thch hp.

2.Nguyn l kh nng hin thc. M hnh c xy dng phi m bot c mc tiu c t ra cho nghin cu vi xc sut khc khngv sau mt bc thi gian hu hn. Thng th bc thi gian ti hnP0 no ca xc sut t c mc tiu P(t),

cng vi gii hn t0 thigian t mc tiu sc cho trc. M hnh c coi l c th chpnhn c nu iu kin: P(t0) P0c thc hin.

3.Nguyn l a m hnh. Nguyn l ny, mc d xp th tv tr th 3nhng li l nguyn l quan trng nht. Thc vy, m hnh c xy

dng cn phi phn nh nhng tnh cht ca h thc (hay hin tng) vcc tnh cht ny trc tip nh hng ln tnh hiu quc la chn.Tng ng vi nguyn l ny l khi s dng mt m hnh c th bt kch cn cng nhn mt vi kha cnh no ca thc t. c th nhnc hy , cn mt tp hp cc m hnh cho php t cc kha cnhkhc nhau cng nh vi cc mc khc nhau phn nh qu trnh.

4.Nguyn l lin hp. Trong i a s trng hp mt h thng phc tpc th biu din di dng cc b phn lin hp (h con) thch hp cho

vic m t ton hc mt cch ph hp. Vi cc h con ny c th sdng cc s ton hc chun m t. Nguyn l lin hp cn chophp xem xt mt cch mm do h cho t cc kha cnh khc nhauph thuc vo mc tiu nghin cu.

5.Nguyn l tham sha. Trong nhiu trng hp, h thng c m hnhha c mt s h con tng i c lp c trng bi mt tham s xcnh (c th l vect). Cc h con nh vy c thc thay th bi ccgi tr s tng ng m khng cn m t chi tit chc nng ca chng.

Khi cn thit, s ph thuc cc gi tr ca tham s ny vo tnh hung cthc cho di dng bng, th hay biu thc gii tch (cng thc).



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php tin hnh cc th nghim khc nhau vi i tng c nghin cu(bng con ng thay i cc gi tr s cc tham s ca m hnh).

Lch sng dng cc phng php m phng ton hc chng t rng m

hnh ton hc khng ch l phng php m ha cc thng tin bit vi tng c nghin cu m cn l cho php d bo cc yu t chabit. Do vy, mt trong nhng bi ton trung tm ca khoa hc l nghincu m hnh, bit rt ra t m hnh nhng thng tin, nhng kh nng timn trong m hnh.

Nhn xt trn khng ch lin quan ti cc phng php m hnh haton hc. Ton hc- l ngn ng m tnh lng. Cc m hnh l s mt v trn ngn ng t nhin n c kh nng d bo ln (mt v din

hnh ca m hnh nh vy l bng tun hon Meneleev). khai thc trithc t nhng m hnh m t nh vy bn cnh cc phng php tonhc cc phng php khc c p dng nh : lgch, tng t, linhp

Cng vic thit lp m hnh ton hc cc qu trnh mi trng l mt biton rt kh, ngoi ra d bo tt cn phi thu thp cc d liu u vo(cc gi tr tham s m hnh di dng cc h s ca phng trnh v cc

bt ng thc to nn m hnh v cc trng thi ban u ca cc qu trnh

cn m phng ). Ch nh vy m hnh mi sng c. Nu cc gi trca cc h s v ca mt vi hm s (xc nh cu trc ca m hnh) cth xc nh vi chnh xc cn thit bng con ng tham kho kinca cc chuyn gia th xc nh trng thi ban u ca mi trng cn

phi c mt mng li quc t thu thp v x l thng tin ban u v tnhtrng sinh quyn.

Trong cun sch ca gio s Kurkovsky A.P v Pritsker A.A.B /[8] / xemxt bi ton m hnh ha cc qu trnh a vt l v mi trng. T quanim ca cc tc gi ny, cc h thng tng gn vi cc m hnh m

phng cho php nng cao hiu qu ca nghin cu mi trng. Theo cctc gi, vn trung tm trong nghin cu mi trng l khi nim chtlng mi trng. Khi nim ny gn lin vi s thit lp ti trng mitrng cho php ln mi trng. T kha cnh m hnh ha, cn thit phinhn c cc m hnh cho php nh gi thit hi ca cc h sinh thida trn cc tiu chun c thit lp. Vi cc bi ton mi trng, itng thc c thay th bi m t ton hc ca chng. Dng ca m hnhtrong cc trng hp ny ph thuc vo phm vi khng gian thi gianca i tng cn xem xt. V d trong khoa hc kh tng (vt l lp st



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mt t ca kh quyn) cc m hnh thy ng lc hc c s dng ktni mt lot cc bin vt l : t cc bin thun ty kh quyn (nhit , psut, m, cc tham s lin quan ti gi vv); ti cc tham s lin quanti b mt lt ca mt t ( nhm); cc tham s lin quan ti v tr (vntc xoay ca tri t, bc x mt tri ). Mc lu ca cc tham s

ph thuc vo phm vi khng gian thi gian ca qu trnh kh tngc xem xt. Hn th na, cc dng ca m hnh ton cc mc khcnhau u khc nhau. im chung y l yu cu nhn c bc tranh vtrng cc tham s kh tng.

Trong nghin cu mi trng ngi ta chia ra thnh 4 mc khng gian thi gian nh sau /ngun [8]/:

Mc ton cu tin hnh kho st vi kch thc ton cu c lu n cc tc ng tng hp cc yu t m ngi kho st quan tm, dinra trong mt khong thi gian t vi thng ti vi chc nm (v d ccm hnh thay i kh hu,...).

Mc vm - xem xt cc i tng v cc qu trnh trong khnggian c kch thc vi ngn km, kch thc thi gian - t mt vi thngti mt nm (m hnh lan truyn vt tuyn cht bn gia cc quc giahay cc hnh tinh vi nhau, m hnh ny c a vo p dng tiChu u v Bc M,).

Mc trung bnh (mc vng) - xem xt cc qu trnh trong khnggian c kch thc t vi trm m ti vi trm km v thi gian t vi giti mt vi thng (cc qu trnh nhim bn kh quyn ti cc thnh phcng nghip, cc t hp cng nghip, cc tnh hung tai bin khi c s

pht ta ln ca cc cht bn vo khng kh l thuc mc ny).

Mc vi m (mc a phng) - xem xt cc qu trnh trn mtdintch t vi m ti mt vi trm m v thi gian t vi pht n mt vichc pht (mt bi ton sinh thi tiu biu y l tnh cho mt s t ccngun thi v xem xt chi tit phn b khng gian ca nng ti mta phng no ).

Chnh v vy trc khi xy dng m hnh mi trng cn phi xc nhcc bc theo thi gian v khng gian i vi qu trnh v i tng angxem xt. Cc khong thi gian c phn loi nh sau :

Cc qu trnh lng ng tnh bng pht hoc gi; S thot hi ca thc vt tnh bng gi, ngy;



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S hnh thnh tri cy tnh bng ngy, thng; S thay i trong cc qun x thc vt v ng vt tnh bng

thng, nm;

S hnh thnh t tnh bng nhiu nm hay th k; Cc qu trnh a mo tnh bng nhiu th k, hay thin nin k.

iu u tin trc khi tin hnh xy dng m hnh cn phi phn loi cckhong thi gian i vi cc qu trnh ang xt. Vic lm ny l cn thitnhm xc nh u tin trong la chn m hnh v nh vy xc nh ccu trc phn mm phc v cho tnh ton thc t. Trn Bng 1-1 l s

phn loi theo khng gian v thi gian ca cc m hnh chuyn ng ca

kh quyn. Bn c c th tm hiu thm trn internet.

Bng 1-1. ac trng cac mo hnh chuyen ong cua kh quyen

c trng ca m hnhM HNH CHUYN NG

CA KH QUYN Phm vikhng gian

Phm vithi gian

Ti liutham kho

1 2 3 4IKE (Institut fr Kernenergie undEnergiesystem)

1 x 1 km Gi Muller et al(1989)

LRTAP (Long Range Transportor Airborne Pollutnats)

500x500 km Ngy D.Davies(1989)

ADOM (Acidic Deposition andOxidants Model)

5 x 5 km Ngy A.Venkatram,P.Karamchand

ani (1989)

TADAP (Transport andDeposition of AcidifyingPollutants)

5 x 5 km Hng gi M.Scholtz et.al. (1987)

ECMWF (European Centre forMedium Range WeatherForecast)

150 x 150km

6 gi H.Jetske et. al.(1989)

RNMI (Royal Netherlands for

Medium Range Weather Forecast

400 x 400

km

1 gi H.Jetske et. al.

(1989)



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MLAM (Multi LayerAtmosphere Model)

100 x 100km

Hng gi Draxler,Taylor (1982)

GCTM (Global Chemical

Transport Model)

1 x 1

5 x 5

Hng

ngy

J.Logan

(1983)

MOGUNTA (Model Of theGlobal Universal Tracer transportIn The Atmosphere)

10 x 10 Thng,Ngy,

Gi

A.Oort(1983)

MSC E EMEP LagrangianTrajectory models

150 x 150km

6 gi A.Pressman etal. (1989)

TIBL (Thermal Internal

Boundary Layer)

1 km x 1 km Gi H.Wang, J

Christiansen(1985)

TDH (Technishe HochschuleDarmastadt)

100 x 100km

Gi S.Zwerver,J.Van.Ham

(1985)

ASTRAP (Advanced StatisticalTrajectory Regional Air Pollutionmodel)

100 x 100km

Ngy J. Shanon(1985)

ERT (Environmental ResearchAnd Technology)

50 x 50 km Ngy D.Davies(1989)



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Cau hoi:

1. Trnh by s khc nhau gia m hnh vt l v m hnh ton hc.2. Gii thch v sao ni m hnh nh mt cng c kt ni th gii t

nhin v x hi loi ngi.3. V sao m hnh c xem l cng c qun l v nghin cu mi

trng.4. Lm r khi nim m hnh gim st mi trng.5. Hy trnh by s phn loi m hnh v cc nguyn l m hnh ha.6. Hy trnh by nh ngha m hnh ha mi trng v s phn loi

theo khng gian v thi gian ca chng.

TAI LIEU THAM KHAO1. Bi T Long v CTV.Nghin cu xy dng v hon chnh m hnh cht

lng nc m phng v dbo lan truyn v pht tn cc chtchi trong mi trng nc vng h lu h thng sng Si Gn -ngNai. M s: SDRBEP 02.04.06. ti d n mi trng lu vc sngSi Gn - ng Nai cp nh nc 2002 2003 ( ti nhnh).

2. Bi T Long v CTV.Nghin cu ng dng m hnh ton kt hp GISm phng v d bo xu th bin i mi trng khng kh tivng kinh t trngim pha Nam ( ti nhnh). ti KC.08.08hng Bo v mi trng v phng chng thin tai 2002 2003.

3. Bi T Long v CTV. M hnh ho qu trnh hnh thnh cht lngnc sngng Nai. ti nhnh KH.07.17 1999 2000.

4. Bi T Long, 2006.H thng thng tin mi trng. Nxb i hc Qucgia TP. HCM, 334 trang.

5. Hans Von Storch, Gotz Floser, 2001. Models in EnvironmentalResearch. Springer, 2001,232 p. (in English)

6. Jorgensen S.E., 1994. Fundanmentals of Ecological Modelling(2ndEdition). Elsevier, 628 p. (in English)

7. Khomiakov D.M., Khomiakov P.M., 1996. Csca l thuyt h thng,Moscow, 107 trang. (in Russian).

8. Kurkovsky A.P., Pritsker A.A.B., 1995. Systems of automatization inecology and geophysics. Moscow: Nauka, 1995. 238 p.



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MO HNH HOA NC DI ATTrong cc ngun ti nguyn thin nhin, ti nguyn nc gi vai tr quantrng i vi s pht trin. Tuy nhin hin nay, ngun ti nguyn ny

ang b suy gim rt nhanh chng ti nhiu khu vc trn t nc chng tado b khai thc qu mc, gy ra cc hin tng nh: st ln t, xm nhpmn v c bit nhim ngun nc ngm rt nghim trng.

Ngun ti nguyn nc ny ang ngy cng trnn b nhim ti hu httt c cc thnh ph trong c nc v thng tp trung ti cc v tr nh:knh rch, cc khu cng nghip v ti cc khu xung quanh bi chn lp...

C th thy nhim ti nguyn nc thng b nhim ti cc v tr xung

quanh cc bi chn lp, nguyn nhn ch yu l do nc r r t cc birc. Bn cnh nc mt v nc di t c mi quan h mt thit vinhau, do vy nhim nc mt s dn n nhim nc di t l iukhng th trnh khi.

Hin nay, vic d bo cht lng cng nh tr lng cho loi ti nguyn nyang l mi quan tm ca nhiu cp chnh quyn. V vy, vic nghin cu vnh gi cc ngun gy nhim cho nc di t l cn thit v cp bchhin nay.

10.1. TONG QUAN VE CAC MO HNH NC DI AT

Nc di t l mt loi khong sn lng, v vy cht lng cng nhtr lng lun c s thay i. S thay i ny cn phi nh lng ha vm t chnh xc lm cscho cc bi ton tnh ton lan truyn cht nhim, tr lng, dng chy, quan trng hn c l n trgip cho cngtc qun l v quy hoch ngun ti nguyn nc di t.

Vic qun l ti nguyn nc di t c p dng cho bn loi biton chung sau y: dng nc di t, dng vn chuyn cht ha tan,dng nhit v bin dng tng cha nc.

Chng

10



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Trong vic xy dng m hnh nc di t, Anderson v Woesner(1992) lit k cc bc sau y:

1. Xc nh mc ch ca m hnh?2. Thu thp s liu a cht v thy vn c v xy dng m hnh nhn

thc ca h.

3. Chn chng trnh my tnh s dng. Chng trnh my tnh c sdng rng ri gm MODFLOW, GMS, MOC, . chng trnh mytnh phi c kh nng p ng trn vn cc mc ch ca m hnh v

phi thch hp vi s liu c.

4. Bc ti p theo l thit k m hnh. Cc iu kin li, iu kinbin v iu kin ban u ca m hnh la chn. Chng phi thchhp vi m hnh nhn thc.

5. M hnh phi c hiu chnh. Thc hin cc vn hnh khc nhau vim hnh ri hiu chnh cc thng s m hnh xc nh xem u raca m hnh c th ti hin c cc s liu ngoi tri v ct nc vlu lng hay khng. Vim ny m hnh thng c mc tin cythp nht.

6.

Nhm tng tin cy ca m hnh, phn tch nhy c tin hnhtrn m hnh hiu chnh xem cc bin i trong mi thng stc ng n cc m hnh nh th no.

7. Nu c mt s nhm d liu ngoi tri th hai v d cc bin i ctnc trong mt th nghim bm ht th c th thc hin giai onhiu chnh th hai gi l kim tra. Nu m hnh hiu chnh ckim tra th tin cy ca m hnh s tng ln.

8. Cc m hnh hiu chnh v kim tra c th dng don. Num hnh c hiu chnh nhng cha kim tra m c dng don th phi thy l n c mc tin cy thp trong kt qu.

9. Khi thy c s khng chc chn, ngay c vi mt m hnh hiuchnh v kim tra, th tin hnh phn tch nhy v don. iuny chng t l c mt phm vi khng chc chn trong cc kt quc don.

10. Cui cng nh l p m hnh sn sng trnh by cc kt qunghin cu bng mt bo co vit cng tt.



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Chng 10 MO HNH HOA NC DI AT383

Di y l hai m hnh thng dng ph bin hin nay nh gi trlng v cht lng nc di t.

10.1.1. Mo hnh dong chay nc di at

M hnh dng chy nc di t dng nh gi tc v hng vnchuyn ca nc di t thng qua cc tng cha nc v lp cch ncdi b mt. Nhng tnh ton ny c gi l m phng. S m phngdng chy nc di t i hi phi c hiu bit su sc vc tnh thyvn ca vng nghin cu. Vic kho st a cht thy vn phi m tccc c trng sau:

- Qui m v chiu dy ca cc tng cha nc v cch nc.- Cc bin thy lc (cn gi l iu kin bin) kim sot tc v

hng di chuyn ca nc di t.

- c tnh thy lc cc tng cha nc v cch nc.- M t s phn b theo phng nm ngang v thng ng ca mc

nc trong vng m hnh t lc bt u (iu kin ban u), nnh (iu kin n nh v iu kin khng n nh khi mc ncthay i theo thi gian (iu kin khng n nh).

- S phn b v ln ca lng b cp, lu lng khai thc hocp nc, tnh thm ca hoc t cc khi nc trn mt (cn gi lp lc stresses). Nhng p lc ny c th l hng s (khng thayi theo thi gian hoc c th thay i theo thi gian.

Sn phm t cc m phng l mc nc v lu lng dng chy ncdi t trong cn bng vi cc iu kin a cht thy vn (hnh dng quim tng cha v cch nc, cc bin thy lc, cc iu kin ban u viu kin khng n nh, cc c tnh thy lc v cc p lc) c xcnh trong m hnh.

Thng qua qu trnh hiu chnh v kim chng m hnh, cc gi tr ca cciu kin a cht thy vn khc nhau c thay i gim s khc bitgia cc s liu do m hnh tnh ton v s liu thc a v tng chnhxc ca m hnh. M hnh c thc s dng m phng s thay imc nc v lu lng dng chy trong tng lai do s thay i ca p lctrong cc tng cha nc.



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10.1.2 . Mo hnh lan truyen chat

M hnh lan truyn cht m phng chuyn ng v s thay i ha hcca cc cht nhim bn khi chng di chuyn cng vi nc di t qua

cc tng cha nc. M hnh lan truyn cht phi da trn m hnh dngchy nc di t c hiu chnh da trn s liu thc a. M hnhlan truyn cht m phng cc qu trnh sau:

- Di chuyn ca cc cht nhim bn theo cc qu trnh chuyn ti vkhuch tn,

- S lan truyn v ha tan cc cht nhim bn bi qu trnh chuynti.

- S loi b hoc gii thot cc cht nhim bn vo hoc ra khi cctrm tch v bi qu trnh hp th hoc nh.

- S thay i ha hc ca cc cht nhim bn bi cc phn ng hahc b kim sot bi cc qu trnh sinh hc hoc bi cc phn ngha hc.

Ngoi kho st a cht thu vn nh nu trn, lp m hnh lan truyncht cn c thm cc thng tin sau:

- Phn b vn tc nc di t nm ngang v thng ng (hngv ln) do m hnh dng chy nc di t c hiu chnhtnh ton.

- Cc iu kin bin ca cht tan.- Phn b ban u ca cht tan (iu kin ban u).- V tr, lch s v khi lng ca ngun ha cht.-

l rng hu hiu.- Dung trng t nhin.- T l cc bon hu ctrong t.- T trng ca cht lng.- nht ca cht lng.- H s phn tn dc v ngang.- H s khuch tn (phn tn).- Tc phn r ha hc hay hng s phn hy.



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- Phng trnh m t cc qu trnh bin i ha hc.- S phn b ban u ca cc cht hp thin t.

Sn phm ca m hnh lan truyn cht l nng cc cht nhim bn trng thi cn bng vi h thng dng chy nc di t v iu kinthy ha c xc nh trong m hnh.

10.1.3. Cac khai niem c ban va phng trnh lan truyen chat nghin cu nhim nc di t, s hiu bit l thuyt c bn vchuyn ng cc cht ha tan trong nc di t l iu cn thit. Tuynhin s vn chuyn ca cc cht nhim ny rt phc tp. Chng c thc biu th bng ton hc, mc d trong mt s trng h p chng ta

khng c s liu thc t gii quyt cc bi ton ny.Qu trnh khuch tn.

L qu trnh m ion hay nhng phn t ha tan trong nc dch chuyn tvng c nng (hay hot tnh ha tan) cao hn n vng c nng thphn.

Qu trnh chuyn ti.

L qu trnh nc di t vn ng mang theo cc cht ha tan.

Qu trnh phn tn.

L qu trnh din ra khi cc cht ha tan i qua mi trng l rng. Qutrnh phn tn c tc ng pha long v h thp nng cht ha tan.

Hin tng tr.

L qu trnh vt l v ha hc gy ra hin tng tr ca chuyn ng chtha tan, cht ha tan c th khng chuyn ng nhanh nh tc cun

theo bit.Qu trnh phn ng.

Qu trnh phn ng, l s hng m i khi cng c s dng trong qutrnh hp th khng thun nghch, bao gm: s phn hy sinh hc, s thy

phn, phn ng xi ha kh v qu trnh bc hi. Qu trnh phn nglun lun lm gim nng cht ha tan nhng n cng c th lm tngnng ha tan vo nc ngm.



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10.1.4. Phng phap giai phng trnh lan truyen o nhiem

Phng trnh lan truyn cht tng qut cho bi ton m phng cht lngnc di t c vit di dng sau:

( ) ( ) nk

ss

k

i

ij

k

ij

i

k

RCqCvxx

CD

xt

C++

=

(I) (II) (III) (IV)

Vi:

(I) Nng bin i ca cht nhim ktrong n v thi gian t.

(II) Nng bin i ca cht nhim theo phng i v j do qutrnh khuch tn.

(III) Nng bin i ca cht nhim theo phng i do qu trnhi lu.

(IV) Thnh phn ph v tng cc phn ng ha hc.

Vi:

- : l rng hu hiu, khng th nguyn.- t: thi gian (T).- xij: khong cch tng ng dc theo h trc ta Decac (L).- Dij: h s phn tn thy ng lc (L2T-1).- vi: vn tc thm hay vn tc dng chy qua l rng (LT-1). N lin

quan ti vn tc dng chy trong nh lut Darcy:

i

iii

x

hKqv

==

- qs: t l lu lng th tch cho mi n v dung tch ca tng chanc i din cho Sources (ngun) v Sinks (vng, b) (T-1).

- Csk: nng cht nhim th k chy t ngun t sinh v t hoi(ML

-3).

- Rn: tng cc phn ng ha hc (ML-3T-1).http://www.ebook.edu.vn


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10.1.5. Phng phap giai phng trnh lan truyen o nhiem

Hu ht cc phng php s gii quyt cc phng trnh truyn ti phn tn phn ng c phn loi theo cc phng php chnh nh sau:

phng php sai phn hu hn chun, phng php hn h p Eulerian -Lagrangianv phng php bin phn bc ba.

Trong phng php hn hpEulerian Lagrangian ngi ta chia ra thnhba phng php khc nhau nh sau:

+ Phng php c trng.

+ Phng php c trng ci tin.

+ Phng php c trng lai.

gii quyt bi ton c mt s hng phn tn, lng b c p/tiu hao vphn ng, ngi ta s dng phng php sai phn hu hn trng tm khi(n hoc hin).

Cn i vi s hng truyn ti do c nhiu cch gii khc nhau nhphng php sai phn chun, phng php Euler Lagrange pha trn hayphng php bin phn bc 3.

10.2. IEU KIEN AUPhng trnh tng qut vn chuyn cht nhim m t s thay i tcthi nng cc cht nhim trong nc ngm. Ngoi ra iu kin ucn gp phn gii quyt phng trnh tng qut trn.

iu kin u c vit nh sau:

),,(),,,( 0 zyxCtzyxC = on t = 0

Vi C0(x,y,z) l nng bit trc.

V l ton b vng nghin cu.

Nu trong iu kin hp ph khng cn bng hoc vn chuyn trong vngi ngu th tht cn thit xc nh iu kin u cho pha hp ph v

pha khng di chuyn (immobile).

10.3. IEU KIEN BIEN

gii phng trnh tng qut th iu kin bin cng cn phi xc nh.C ba iu kin bin c c p trong m hnh lan truyn cht trong



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nc di t l: Nng xc nh dc theo bin (iu kin Dirichlet);nng bin i xc nh chy qua bin tnh ton (iu kin Neumenn);v iu kin hn hp (kt hp c hai iu kin trn).

C ba iu kin bin chnh nh sau:10.3.1. ieu kien bien loai I

L iu kin nng c xc nh dc theo bin trong sut thi gianthit lp m hnh (iu kin bin Dirichlet). l nng c xc nhtrc v gi tr ny khng i trong sut thi gian tnh ton. V c xcnh nh sau:

0( , , , ) ( , , , )C x y z t C x y z t = trn , t 0

Vi: l bin xc nh v 0 ( , , , )C x y z t l nng nhim xc nh dc

theo bin .

10.3.2. ieu kien bien loai II

L iu kin bin nng cht ha tan c xc nh trc (cn gi liu kin bin Neumann). l cc m nng cht ha tan chy qua

bin c xc nh trc trong sut bc thi gian tnh ton. V n c

m t qua phng trnh sau:

( , , , )ij ij

CD f x y z t

x

=

, t 0

),,,( tzyxfi l phng trnh c xc nh i din cho dng chy phn

tn ti bin . Trng hp khng c dng chy phn tn th nng cxc nh bng khng, ngha l fi(x,y,z.t) = 0.

10.3.3 . ieu kien bien loai IIIL iu kin bin m gi tr nng dc theo bin v nng bin ichy qua bin c xc nh (iu kin Cauchy). V n c m t qua

phng trnh:

( , , , )ij i ij

CD q C g x y z t

x

=

trn , t 0

Vigi(z,y,z,t) l phng trnh i din cho tng dng chy (phn tn v ilu) ti bin . Vi bin khng thm, th c dng chy phn tn v i lu



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Hnh 10-2.Bin t nhin - a cht ca khu vc lp m hnh

c/ Nhng lu quan trng

- Phi c t nht mt iu kin bin mc nc tham chiu.- Khng chn cc bin nhn to qu gn din tch nghin cu.- Khng phi tt c cc i tng nc mt u c xem l bin

dng chy (v d: nc tng cha nm su di t s chy bndi y sng).

- M hnh nhiu l p c thi hi cc bin khc nhau (v cc iukin bin) cho tng lp ca m hnh (c bit vi vng c nhiu tngcha nc c p).



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10.4. MOT SO PHAN MEM C S DUNG RONG RAI

10.4.1. Mo hnh Visual MODFLOW

MODFLOW c vit tt bi: Modular three-dimensional finite difference ground water model. MODFLOW phin bn u tin ra inm 1984. Trong qu trnh nghin cu v pht trin ngi ta nng cpm hnh MODFLOW thnh cc phin bn mi nh: Visual MODFLOW2.8.2 v gn y nht l Visual MODFLOW 4.1 c giao din v chcnng nhiu hn so vi phin bn gc. MODFLOW 2000 l phin bnu tin c s dng phn bit vi cc phin bn mi hin nay.

Visual MODFLOW l m hnh mi trng y nht v d dng s dng

vo vic ng dng vo thc t trong dng chy nc di t ba chiu v mphng s lan truyn cht nhim trong nc di t. Chng trnh ny thc tch hp y bao gm cc modules nh: MODFLOW,MODFLOWSURFACT, MODPATH, Zone Budget, MT3Dxx/RT3D,

MGO, and WinPEST vi gi tr giao din ha mnh m v trc quan nht.Vi nhng cu trc trnh n logic v d dng s dng, cng c ca VisualMODFLOW cho php thc hin cc chc nng sau:

1. D dng xc nh phm vi ca vng cn nghin cu v chn lacc n v s dng.

2. Gn thuc tnh ca m hnh v iu kin bin thch hp.3. Chy m hnh m phng.4. Hiu chnh hng dn s dng m hnh v k thut kim tra.5. Ti u v tr v lu lng bm ht ca ging.6. Hin th kt qu s dng ha 2D hoc 3D.

10.4.2 Mo hnh GMS

GMS l phn mm m hnh nc di t tinh vi v ton din. M hnhny hin nay c s dng trn 90 quc gia bi cc t chc, c nhn...ang hot ng trong lnh vc v qun l nc di t. GMS cung cpnhng cng cn gin d s dng v chc nng hu ch trong vic thitlp m phng v tr, pht trin m hnh, qu trnh b sung d liu, hiuchnh v trc quan cho ngi s dng.

GMS cha ng nhiu m un tnh ton cho cc loi bi ton ncdi t khc nhau nh: tnh ton kh nng lan truyn cht nhim trong



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thuc vo bi ton, iu kin ban u v iu kin bin m ta p dng choph hp.

Trong MT3D s dng cng thc hin, nhng trong MT3DMS ci tin th

s dng cng thc n, cng thc ny c mt cch gii quyt a nng vhiu qu. Php lp da vo phng php dao ng lin hp tng qut vinhng iu kin chn la phn trc v s dng lc ma trn khngi xng.

10.5 NG DUNG PHAN MEM MODFLOW VA MT3DMS TNH TOANMO PHONG LAN TRUYEN MIT TRONG NC DI AT LAYTP.HCM LAM V DU NGHIEN CU

10.5.1. Mo ta oi tng nghien cu

i tng c chn xem xt l hai bi chn lp trn a bn TP. H ChMinh. Bi chn l p th nht l Khu lin hp x l cht thi rn Ty Bcthnh ph H Ch Minh thuc x Phc Hi p, huyn C Chi, TP. H ChMinh. Khu vc bi chn lp d kin xy dng vi din tch khong 43,3 hanm trong khu vc t knh 15 n knh 17 thuc phn t ca nng trngTam Tn giao khon li.

Bi chn lp th 2 l bi rc G Ct. Bi chn lp ny c xy dng trnl t thuc x Bnh Hng Ha, huyn Bnh Chnh, gip ranh vi huynHc Mn v qun Tn Bnh, c din tch 25 ha. Pha Ty l quc l 1A.Pha Bc l vng hm hoang, mt phn din tch c dn nh c cito lm h nui c. Pha ng v ng Bc l Knh Nc en vi khudn c mi pht trin dc bn kia bknh. Pha Nam l m nc khong6 ha khng canh tc c lc bnh ph kn ton b b mt nc.

10.5.1.1. c im a cht birc Phc Hip

Theo kt qu khoan kho st a cht cng trnh, c th chia a tng khuvc d n thnh ba lp nh sau:

- L p 1: L p bn st hu c mu xm en, xm xanh, trng thichy, kt cu km cht. Lp ny c b dy thay i t 7 14m,lun trng thi chy, h s rng ln trung bnh. Lc dnh v gcma st trong rt nh.

- Lp 2: Lp st mu vng nu, xm nu, hoc hng nht, kt cucht va, trng thi na cng, h s rng ln trung bnh. Lc dnh



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v gc ma st trong trung bnh. Lp ny c chiu dy thay i t 3-1m.

- Lp 3: Hn hp ct ht nh ln sn si thch anh mu xm nht,xm trng hoc vng nht, h s rng ln trung bnh. Lc dnh vgc ma st trong trung bnh. Chiu dy lp xp x 10m, dung trngt nhin ln 1,896 g/cm3.

10.5.1.2. c im thy vn birc Phc Hip

Nc mt: Khu d n c gii hn bi cc knh nc mt: knh ThyCai, knh 15, knh 16, knh 17, knh 18. H thng knh rch ny cungcp nc ti tiu cho ton khu vc.

Nc ngm: Kt qu thm d xc nh tng cha nc th nht nm su t 18 40m, mc nc ngm ca tng cha nc th nht vo makh ti khu vc kho st nm cch mt t rt nng t 0,7 1m.

Nhn xt chung vc im a cht a cht thy vn: Khu vc ny cmt sng rch thp, v tr thun li cho vic b tr bi chn lp rc thi.

Va cht cng trnh: Tng t bn di c chiu su bn st dy (10m),cng chu nn yu, i hi phi x l nn m bo kh nng chu ti

tng thch i vi ti trng ln ca bi chn lp trn din tch ln.Va cht thy vn: Mc nc ngm khu vc rt cao i hi phi p stm bo tng cch ly tha mn cc yu cu bo v mi trng khi xydng bi chn lp nhm gim thiu nhim.

10.5.1.3. c im a cht birc G Ct

Ti bi chn lp G Ct, tin hnh khoan 5 l khoan kho st acht, vi su 50m cho mt l. Kt qu khoan a cht nh sau:

- 0,0 0,3 m: lp ct, ct pha mu vng, xm trng- 3,0 3,3 m: lp st ln vi laterit- 3,3 4,0 m: st, mu xm trng, pht vng- 4,0 4,6 m: st pha ct, m xm trng- 4,6 11,5 m: st mu xm trng, pht vng- 11,5 15 m: st mu vng nu- 15 24 m: ct ht nh mu vng



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- 24 31,7 m: st mu nu- 31,7 35 m: st mu vng, trng xm- 35 50 m: ct ht mn, vng

t khu vc ny c l p trm tch pleistocene nn ln khng ng k.Hn na sau khi t c o, rc chn y c t trng thp hn nnkhng nh hng n bn vng ca lp t b mt chn l p. Kt qukho st thm thu ca t cc su khc nhau thuc khu vc bichn l p G Ct cho thy h s thm thu qua cc l p dao ng trongkhong 1,1232-0,23328 cm/ngy m. Vi h s tc thm nh vy, cccht nhim phi mt khong 89-428,6 ngy mi i ht qua lp t dy 1m,

phi mt 623-2996 ngy m mi i qua 7 m t st.

10.5.1.4. c im thy vn birc G Ct

Rch Nc en l ngun tip nhn nc thi t trm x l r r ca bichn lp ny. y l mt con rch ni lin vi h thng knh o 19-5 vknh Tham Lng pha Bc chy ra sng Si Gn, on chy ra phng15 Tn Bnh v pha Nam ni vi con rch ny cng thng vi nhiu hm trong a bn x Bnh Hng Ha. C th thy rch Nc en nm gia hai u ca hai nhnh knh thot nc thi ca thnh ph hay nicch khc c th xem nhy l thng ngun ca hai nhnh knh ThamLng v knh Tn Ha nn dng chy thay i theo thy triu ln xungng thi c hai u rch, do c s tch t cht thi on knh nylm nc b nhim, en kt v c mi hi thi.

Mch nc ngm

Theo s liu bo co ca SGiao thng Cng chnh cho thy trong gii hnchiu su cc l khoan, nc ngm trong khu vc c th tn ti 3 v tr:

- Tng t t 4,0-4,6m: c cu trc st pha ct c kh nng ngmnc, tuy nhin vi v tr v cu trc nh vy s khng cha lngnc di do song nc ngm trong tng ny li lm tng kh nngthm nc ca t nn d b nhim bn t cc ngun nc thihin tn ng trn mt t khu vc bi chn lp.

- Tng ct t 15,0-20,0m: tng t ny nm trong chiu su quy cca tng nc ngm mch nng nhng ngoi gii hn chiu suy bi chn lp, c kh nng tr nc ln v c ngn cch bilp t st tng i dy v c cao n nh, tc thm ncxp x 0,018 cm/h. Tuy nhin trong khu vc bi chn l p trc



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chn lp bi chn lp trc y, tng t ny cng c kh nng bnh hng bqu trnh o t lm bi chn lp trc y thngthc hin ti su khong 14-15m v cc h chn lp trc ykhng h c gia cng lp lt y trc khi chn rc.

- Tng ct cha nc ngm su 35,0-50,0m: tng nc ny c thhon ton cch bit vi cc tng t trong vng nh hng ni trn vc lp t st dy khong 10m ngn cch. y l loi t c tnhkhng thm nc kh cao.

nh gi mt cch tng i chnh xc hin trng cht lng nc trongkhu vc, cc d liu c nh gi theo phng php thng k trn csktqu phn tch nc ngm c thu thp ti cc ging nm trong khu vc bi

chn lp c v ti cc h dn c xung quanh khu vc d n trong vng bnknh 100m i vi ranh gii khu t. Cc ging la chn kho st u c su t 22 n hn 40m.

10.5.2. D lieu au vao cho mo hnh

tnh ton s lan truyn cht nhim trong nc di t bng moduleMT3DMS th vic u tin cn chy MODFLOW. Sau kt qu nyc s dng cho MT3DMS chy. Kt qu sau khi chy MODFLOW

hon ton chnh xc so vi thc t. Sau y l cc d kin lin quan tichy Module MT3DMS.

10.5.2.1. Li v ngng mc nc ca m hnh

Li tnh c chia thnh: 90 hng x 90 ct to thnh mt h thng lihai chiu nh hnh trn. Kch thc mi li ca m hnh l: 1000 (m)x 1000 (m). Cc li khng thuc din tch l p m hnh l nhng khng hot ng.

Li tnh ton hai chiu: Dng ni suy cc d liu t cc im ri rcn tng li v lu d liu thnh tng tp tin phc v cho vic chuynd liu ny vo li ba chiu.



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10.5.2.2. Cc tng cha nc.

Da vo c im cha nc, quan h thy lc ca cc lp a cht cmt trong vng lp m hnh dng chy v nhim bn, chng ta s ha

cc lp cch nc v cc tng cha nc trong vng thnh 6 lp nh sau:

Hnh 10-5. Cc lp a cht ca TP. H Ch Minh c s dngtrong m hnh

L p 1: Bao gm cc trm tch Holocen v l p cch nc ca cc trm tchPleistocen, phn b trn ton vng lp m hnh. Thnh phn ch yu lht mn: bn st, bn ct, st, bt, bt ct, ct bt, i ch xen kp ccthu knh ct ... Nhn chung y l lp thm nc km v c cha nccc b.

Lp 2: Lp cha nc, l cc lp ht th ca cc trm tch Pleistocen, gm ctmn n th c cha sn si. Phn b trn ton vng lp m hnh.

Lp 3: Lp thm nc km, gm cc lp ht mn ca trm tch Pliocen trngm st, bt, bt st... Phn b trn ton vng lp m hnh.

Lp 4: Lp cha nc, l cc lp ht th ca trm tch Pliocen trn gm ct tmn n th c cha sn si. Phn b trn ton vng lp m hnh.

Lp 5: L p thm nc km, gm cc lp ht mn ca trm tch Pliocen

di gm st, bt, bt st... Din phn b hp hn cc lp trn do



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vng mt trm tch Pliocen di pha ng t Bnh Trng ngip sng ng Nai.

Lp 6: Lp cha nc, l cc lp ht th ca tm tch Pliocen di gm ct t

mn n th c cha sn si. Din phn b hp hn cc l p trn dovng mt trm tch Pliocen di pha ng t Bnh Trng n gipsng ng Nai.

10.5.2.3. Dliu vthng sa cht thy vn xung quanh khu vc cc bi rc.

10.5.2.3.1. Hsthm (Hydraulic conductivity).

hiu r c tnh lan truyn quanh khu vc bi rc. Ta cn phi xem xtti c tnh t cc lp khc nhau cc quanh khu vc hai bi rc

Tam tn (Phc hip) v G ct, nghin cu nh hng qu trnh lan ta nhim tng Nitti ba tng a cht layer 1, layer 2, v layer 3.

a) Hsthm thm ngang (Horizontal K) v hsthm dc (VerticalK) ca ba lp a cht ti bi rc Phc Hip (Tam tn) c gntheo nhsau: (hsthm ngang Kh, hsthm ng Kv). Xt

gi trtrong 12 xung quanh bi rc cho 3 lp a cht.

Bng 10-1. H s thm ca cc lp a cht khu vc Phc Hip

H S THM NGANG(KH)

H S THM DC (KV)

0,75 0,75 0,75 0,75 0,75 0,75 0,75 0,75

0,75 0,75 0,75 0,02 0,75 0,75 0,75 0,002

Lp1

0,75 0,75 0,75 0,02 0,75 0,75 0,75 0,002

45 45 45 45 3,5 3,5 3,5 3,5

45 45 35 35 3,5 3,5 3,5 3,5Lp2

45 35 35 40 3,5 3,5 3,5 4,5

0,0025 0,0025 0,0025 0,0025 0,00025 0,00025 0,00025 0,00025

0,0025 0,0025 0,0025 0,0025 0,00025 0,00025 0,00025 0,00025

Lp3

0,0025 0,0025 0,0025 0,0025 0,00025 0,00025 0,00025 0,00025



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Hnh 10-6. Bn cc h s thm lp 1 quanh khu vc bi rc Phc Hip

Hnh 10-7.Bn cc h s thm lp 2 quanh khu vc bi rc Phc Hip



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Tm li:

H s thm ca mi lp a cht tng i ng nht gia cc trong khuvc nghin cu.

Kh nng cha nc v vn chuyn nc trong: lp 2 > lp 1 > lp 3. Nuc ba lp a cht trn b nhim th kh nng lan truyn cht nhim calp 2 l ln nht do h s rng ln v t ch yu l ct nn khng ckh nng hp ph, gi nc tt. Mt khc lp 2 l lp cha nc, phc vnc sinh hot v sn xut cho con ngi, nu tng ny b nhim th khnng vn chuyn cht nhim cng ln khi c nhiu ging khai thc gnngun nhim. V vy, vic qun l cng nh x l vn nhim chotng a cht ny rt kh, i hi phi c cng c qun l ph hp nh

gi kh nng lan truyn ca cht nhim, t ra chin lc qun lchnh xc v hiu qu.

b/ H s thm ngang (Kh ) v h s thm dc (Kv) ca bi rc GCt, xt gi trtrong 9 xung quanh bi.

Bng 10-2. H s thm ca cc lp a cht quanh khu vc bi rc GCt

H S THM NGANG (KH) H S THM DC (KV)

0,5 0,5 0,5 0,5 0,5 0,5

0,5 0,5 0,5 0,5 0,5 0,5

Lp 1

0,5 0,5 0,5 0,5 0,5 0,5

45 45 45 4,5 4,5 4,5

45 45 45 4,5 4,5 4,5Lp 245 10 10 1 1 1

0,00001 0,00001 0,00001 1.e-006

1.e-006

1.e-006

0,00001 0,00001 0,005 1.e-006

1.e-006

0,0005

Lp 3

0,00001 0,005 0,005 1.e-006 0,0005 0,0005



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Hnh 10-10. Bn cc h s thm lp 2 quanh khu vc bi rc G Ct



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Hnh 10-11. Bn cc h s thm lp 3 quanh khu vc bi rc G Ct



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T cc gi tr h s thm (Bng 10-2) v cc hnh minh ha (Hnh 10-9 -Hnh 10-11) ta c nhn xt nh sau:

+ i vi lp 1: H s thm ngang v thm dc tng i ng nht

gia cc li nm pha trn khu vc nghin cu (Kh = 0,5; Kv =0,5). H s thm th p v t trong khu vc ch yu l thnhphn t pha st, ct v cc cht hu c... Do vy, kh nng dichuyn nc v cht l rt kh.

+ i vi lp 2: H s thm ngang v dc trong lp ny ln hn rtnhiu so vi h s thm lp 1, vi Kh2 = 90 Kh1 v Kv2 = 9 Kv1.Thnh phn a cht ch yu l ct mn cho ti si th, do khnng di chuyn nc trong lp ny l rt ln. Nu cht nhim b

nh hng xung tng ny th kh nng di chuyn v phn tn rtln, kh kim sot.

+ i vi lp 3: H s thm ngang v dc rt thp, t tng nych yu l st nn kh nng di chuyn nc rt chm. Do c ngha trong vic ngn cn cc cht nhim thm xung tng ngm.c tnh t ca tng ch yu l st nn c kh nng hp phhp th rt cao.

Tm li:Cc thuc tnh lp a cht ca khu vc bi rc G Ct c tnh cht tngt bi rc Phc Hip, lp 1 v lp 3 l lp cch nc, hai lp ny tuycch nc nhng tnh cht t v kh nng vn chuyn nc khcnhau. Lp 2 l lp cha nc v vn chuyn nc tt nn kh nng lan tacht nhim cng rt tt. i hi phi c bin php qun l tt khi lpny b nhim.

10.5.2.3.2. Dliu vlng bcp (Recharge package)

Lng b cp l lng nc t nhiu nhn t khc nhau i vo h thngnc di t: ma, l, ng ng p... Hin ti khng c cc cng trnhnghin cu chuyn mn nhng vn ny v v rt phc t p nn trongtnh ton a cht thy vn thng ch xt ti lng ma. Theo tnh tonca cc nh chuyn mn th lng b cp khng vt qu 20% lng mav ph thuc vo nhiu yu tc bit l cc yu t sau: dc a hnh,thnh phn t trong tng vng tip nhn nc ma v thm thc vt.



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10.5.3. Thiet lap va chay MT3DMS

10.5.3.1.Thit lp m hnh cho phm vi c khu vc TP H Ch Minh

Theo s liu quan trc ca Phng cht thi rn, thuc STi nguyn vMi trng TP.HCM, th nng nittng ca bi rc Phc Hip bini theo ma v nng nit tng bin thin trong khong 900 3000mg/l. Ma ma nng nit gim do b pha long bi nc ma, makh nng tng cao.

Cc thng s nhp cho m hnh c khu vc ln bao gm:

Bng 10-3. Gi tr cc thng su vo ca m hnh ln

c tnh Tham s

rng phn tn theo phng dctheo dng chy

Lp 1

0,3 2


Lp 2

0,3 10


Lp 3

0,3 0,002

Lng b cp Nng ni ttngBi rc

0,000025 m/d 2500 mg/l

Gi phn tn

Lp TRPT TRVT

L p 1 1 0,1

L p 2 1 0,1

L p 3 1 0,1



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Hnh 10-13. Thit lp bi rc

Bc 2: Chuyn file c ui (*shp) cha d liu thng tin a l (GIS) vbi rc ( xc nh v tr v ta ca bi rc) vo m hnh.

Hnh 10-14. a d liu GIS vo m hnh



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Bc 3: Gn gi tr cho cc lp gm rng v h s phn tn theophng dc theo dng chy (porosity and longitudinal dispersion)

Hnh 10-15. Gn gi tr rng v h s phn tn theo phng dctheo dng chy

Bc 4:Thit lp cc d kin cho MT3DMS.

Hnh 10-16. Thit lp d liu cho MT3D



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Bc 5: Gn gi tr thi gian nghin cu (ngy) v bc l p tnh ton(Length v Max transport steps)

Hnh 10-17. Gn gi tr thi gian nghin cu v bc chy

Bc 6: Chn cc d kin tnh ton (ti, phn tn, ngun t sinh/t hoi,theo di lan truyn).

Hnh 10-18. Chn d liu cc qu trnh ti, phn tn, ngun t sinh/t hoi,theo di lan truyn



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Bc 7: Gn tn cht nhim cn nghin cu (tng nit).

Hnh 10-19. Chn cht nhim

Bc 8:La chn bc xut d liu tnh ton nhim theo thi gian.

Hnh 10-20. Chn thng s xut phn mm xut d liu



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Bc 9:La chn phng php tnh ton s hng ti, s dng phngphp bin phn bc 3.

Hnh 10-21. La chn gii thut x l thnh phn ti(trn hnh chn phng php bin phn bc 3)

Bc 10: Gn gi tr cho h s phn tn cho cc lp 1, lp 2 v lp 3.

Hnh 10-22. Gn gi tr cho h s phn tn cho cc lp 1, lp 2 v lp 3.



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Bc 11: Gn gi tr tc b c p v nng b c p cho cc bi rc(recharge rate v recharge conconcentration) cho hai bi rc.

Hnh 10-23. Gn gi tr b cp v nng b cp cho cc bi rc

Bc 12: Chuyn tt c cc d liu thit l p trn bn voMT3DMS.



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Hnh 10-24. Chuyn i d liu trn bn vo MT3DMS

Bc 13:Chy MODFLOW



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Hnh 10-25. Chy chng trnh MODFLOW

Kt qu chy MODFLOW: Cho ra ng ng mc nc c thnh ph.



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Hnh 10-26. Bn ng ng mc nc c Thnh ph



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Bc 14:Run MT3DMS.

Hnh 10-27. Chn thc n chy m hnh MT3DMS

Kt qu chy MT3DMS.

Hnh 10-28. Kt qu chy MT3DMShttp://www.ebook.edu.vn


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nh gi kt qu MT3DMS v qu trnh hiu chnh m hnh ln:

Do cch chia li cho m hnh c thnh ph tng ng vi kch cmi ca m hnh l: 1000 (m) x 1000 (m) = 1 km2. Do vy, khi tnh ton

phng trnh vn chuyn bng module MT3DMS kt qu khng hi t, vbc lp ca bi ton lan truyn cht ph thuc vo s li trong mhnh. Nu li ca m hnh m qu ln th kh nng ni suy bng

phng php sai phn hu hn ti cc tm rt kh hi t. Ngoi ra, mhnh ln c rt nhiu bin khc nhau nh: bin sng, rch, bin mc ncxc nh, bin khng thm...do vy khi tnh ton MT3DMS bng thutton ny my tnh bt buc phi c ht cc iu kin bin ny tnhton nn bc lp v thi gian tnh ton nhiu v i hi b nhmy tnh

phi ln v cng sut my tnh phi mnh.Nhng vn nghim trng ny lm cho cc chuyn gia nghin cuphi c cch gii quyt ph hp khng nhng c thng dng ph binm cn c hiu qu kinh t hn trong vic thit lp m hnh vo qun l.

Do , gii quyt vn ny ngi ta bt buc phi chuyn d liu,thuc tnh cc tng a cht ca m hnh ln sang m hnh a phng(local model) v chia li kch c li cho m hnh a phng (localmodel) ph hp. Kt qu kh thi hn khi thc hin trn m hnh nh, vi

b nhv b x l my tnh thp hn.

10.5.3.2.Thit lp m hnh cho tiu khu vc hai bi rc Phc Hipv G Ct.

Nhng d liu cbn chuyn t m hnh ln sang m hnh a phngbao gm: cao mc nc, d liu cc lp tng a cht ( cao mi cami lp, h s thm, mc nc ban u...). cao mc nc ngm ctnh ton t m hnh ln th c p dng l bin mc nc xc nh cho

m hnh a phng.Qu trnh thit lp m hnh a phng c tm tt tng qut nh sau:

Bc 1: Chuyn cc lp d liu a tng ca MODFLOW (vng ln) sangmt him phn tn 2 D (Scatter Point Set 2 D).

Bc 2: Xy dng m hnh khi nim a phng (Building the LocalConceptual Model).

+ Xy dng lp i tng mi (new coverage).

+ Xy dng vng bin ca m hnh a phng.



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+ Xc nh bin mc nc xc nh (Specified Head Boundary)cn nghin cu.

+ Nhp gi tr vo bin mc nc xc nh (da vo kt qu mc

nc tnh ton ca m hnh ln).Bc 3: To m hnh MODFLOW a phng.

+ To li 3 D cho m hnh a phng.

+ Xc nh li hot ng.

+ Chuyn cc thuc tnh t li sang MODFLOW/Modpath.

Bc 4: Ni suy d liu lp a tng t him phn tn bc trn sang

cc lp d liu MODFLOW a phng.Bc 5: Lu kt qu v chy module MODFLOW cho ra ng ng

mc nc ca m hnh a phng gn ng vi ng ngmc nc ca m hnh ln.

Qu trnh thit lp m hnh a phng gm cc bc nh sau:

1. Chuyn cc d liu a tng qua mt him phn tn.

+ Chn 3D Grid data trongProject Explorer.

+ Chn lnh Grid/MODFLOW Layer2D Scatter Points (gi li3 tng a cht nghin cu l:Layer 1, Layer 2 vLayer 3)

+ Thay i tn Scatter Points thnhRegional Data.

+ Bm Ok kt thc.

2. Xy dng m hnh nim a phng (Local Conceptual Model)

+ Right - click mouse vo HCM_new chnDuplicate.

+ Thay i tn thnh G Ct hoc Phc Hip (Local model).

2.1. To vng nghin cu (New coverage).

+ Right-click vo tn G Ct hoc Phc Hi p trongProjectExplorerv chn lnhNew Coverage.

+ Thay i tnNew Coverage thnh Sources/Sinks.

+ Trong Sources/Sinks/BCs chn Specified Head and LayerRange.

+ Thay iDefault layer range thnh 1 to 3.http://www.ebook.edu.vn


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+ Chn Ok thot giao din.

2.2. To bin cho m hnh a phng (local boundary model).

+ Xc nh vng nghin cu.

+ Nhn vo biu tng Sources/Sinks trongProject Explorer.

+ Chn cng cCreate Arc .

+ To 4 cung xung quanh bi rc G Ct hoc Phc Hi p nh Hnh10-29 (Lu : Bin mc nc xc nh pha trn v pha di phi trngvi ng ng mc nc, 2 cung cn li c to phi vung gc ving ng mc nc)

Hnh 10-29. Xy dng bin cho m hnh

+ Building the Polygon: chnFeature Objects/ Build Polygons.

2.3. Gn cung mc nc xc nh cho 2 cung pha trn v pha di.

+ Chn cng cSelect Arcs nhn Shift chn 2 cung pha trnv pha di ca m hnh v chnProperties .

+ MSpec. headcho c 2 cung, nhn Ok v thot.

+ Chn cng cSelect Points/Nodes .



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+ Chn 2 nt ca cung pha trn nhhnh 4.9, nhn Propertiesv nhp gi tr mc nc vo 2 nt trn vi gi tr (2.5 cho bi rcG Ct) (Lu : Gi tr ny ty thuc vo gi tr ca ng ngmc nc m ngi thit lp chn).

+ Tng t nhp gi trng mc nc cho cung pha di.

3. To m hnh MODFLOW a phng (local MODFLOW model).

+ To khung li cho m hnh: Trong Project Explorerright _ clickvo khong khng gian v chnNew/Grid Frame.

+ Right - clickvo Grid Frame trongProject Explorerv chnFit to Active Coverage.

3.1. To li (Creating the Grid).

+ TrongProject Explorer right - clickvo Grid Frame v chnlch Mapto/ 3D Grid.

+ Nhn Ok v nhp gi tr di (lenght) kch c li mun thitlp v chn s v s lp nghin cu (trong mc number cells).

+ Nhn Ok thc thi lnh.

3.2. To cc hot ng (Activating the Cells)

+ Chn 3D Grid Data trongProject Explorer.

+ Chn MODFLOW / New Simulation/ nhn Ok.

+ Chn Map Data trong Project Explorer/ m FeatureObjects/ActivateCells in Coverage(s).

3.3. Chuyn d liu MODFLOW sang li (Convert the MODFLOW to

the Grid)+Right clicktrnLocal Model(G Ct) trongProject Explorerv

chn Map to/ MODFLOW/MODPATHt menu.

+ Nhn Ok v chnAll applicable coverages.

4. Ni suy d liu lp a tng (Interpolating the Layer Data).

Trong bc ny d liu ca cc lp a tng ca m hnh ln tim phntn (Scatter Points) ti cc lp ca m hnh a phng.

+ Right clickvo Regional Data Scatter Set trong Project



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Explorerv chn lnhInterpolate To/MODFLOW Layers.

+ Nhn Ok thc thi lnh.

5. Lu kt qu v chy MODFLOW.

6. Thit lp MT3DMS tng t trong mc 0.

Bng 10-4. S liu tnh ton cho m hnh nhim bn tiu khu vcbi rc G Ct

c tnh Tham s

Lp 1 rng phn tn theo phng dc theo

dng chy

0,3 2

Lp 2 rng phn tn theo phng dc theodng chy

0,3 10

Lp 3 rng phn tn theo phng dc theodng chy

0,3 0,002

Bi rc Lng b cp Nng ni ttng

0,000025 m/d 2500 mg/l

Gi phn tn

L p TRPT TRVT

L p 1 1 0,1

L p 2 1 0,1

L p 3 1 0,1

Kch thc Chiu rng =200 m Chiu di = 200 m



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S lng Ct = 35 Hng = 30

Thi giannghin cu

20 nm = 7300 ngy

Cc bc nhp d liu vo m hnh a phng tng t nh vic nhp dliu vo m hnh ln.

Kt qu MODFLOW ca khu vc tiu bi rc G Ct:

Hnh 10-30. Kt qu MODFLOW cho ng ng mc nc khu vcbi rc G Ct

Kt qu MT3DMS ca khu vc tiu bi rc G Ct:



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Hnh 10-31. Kt qu MT3DMS cho phm vi lan truyn quanhbi rc G Ct

Bng 10-5. S liu tnh ton cho m hnh nhim bn tiu khu vcbi rc Tam Tn

c tnh Tham s


Lp 1

0,3 2 rng phn tn theo phng dc

theo dng chyLp 2

0,3 10


Lp 3

0,3 0,002



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Lng b cp Nng ni ttngBi rc

0,000025 m/d 2500 mg/l

Gi phn tn

L p TRPT TRVT

L p 1 1 0,1

L p 2 1 0,1

L p 3 1 0,1

Kch thc Chiu rng = 200 m Chiu di = 200 m

S lng Ct = 40 Hng = 35

Thi giannghin cu

20 nm = 7300 ngy



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Kt qu MODFLOW ca khu vc tiu bi rc Phc Hip:

Hnh 10-32. Kt qu MODFLOW cho ng ng mc nc khu vcbi rc Phc Hip

Kt qu chy MT3DMS:

Hnh 10-33. Kt qu MT3DMS cho phm vi lan truyn quanhbi rc Phc Hip



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Cau hoi

1. Trnh by cc khi nim cbn lin quan ti bi ton lan truyn cht nhim trong nc dc t

2. Trnh by cc phng trnh lan truyn cht cbn lin quan ti ncdi t v nu r ngha cc h s tham gia vo phng trnh.

3. Hy trnh by iu kin ban u v iu kin bin. Nu r ngha vtl ca cc iu kin ny.

4. Nu r mt s phng php gii s bi ton lan truyn nhim trongnc di t.

5.

Gii thiu mt s phn mm tng ho tnh ton nc di t.

TAI LIEU THAM KHAO

1. MT3DMS:A Modular Three-Dimensional Multispecies TransportModel for Simulation of Advection, Dispersion, and Chemical

Reactions of Contaminants in Groundwater Systems; Documentation

and Users Guide by Chunmiao Zheng, P. Patrick Wang, University

of Alabama.

2. GMS 6.0 Tutorials_Copyright 2005 Brigham Young UniversityEnvironmental Modeling Research Laboratory.



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NHNG KHAI NIEM C BAN CUA MO HNHHOA MOI TRNGTrong l thuyt h thng ngi ta chia ra ba giai on ln: (1) t vn ;(2) m hnh ha v phn tch; (3) thng qua quyt nh. Ti giai on t biton iu quan trng nht l xc nh: mc tiu nghin cu; cc ni dunglin quan v mi quan h gia cc ni dung. Thng thng, vic t biton c chnh xc ha trong qu trnh nghin cu. Cc bi ton v nhimv xut hin trong giai on m hnh ha v phn tch. Phn di y trnh

by nhng khi nim cbn ca mn hc m hnh ha mi trng.

2.1. CAUC GIAI OAN CO BAUN CUUA QUAU TRINH XAAY DNGMOA HINH MOAI TRONG

c nhiu tc gia ra cc th tc cn thit xy dng m hnh ton ccqu trnh mi trng. Cc giai on cn thit xy dng m hnh mi trnggm: l thuyt, th nghim, tnh th nghim trn my tnh, din gii.

Giai on l thuyt: cn thit hnh thnh mc tiu nghin cu qu trnhmi trng t quan im m ti tng mt cch ngn gn. Giai on

ny gm cc bc sau y: Tm kim nguyn mu m t ngn gn qu trnh mi trng tip

theo c th hnh thnh m hnh ton cho cc nghin cu tip theo;

Phn tch s tng thch gia cc s liu o c thc a m ngixy dng m hnh ang c vi nguyn mu dnh chn;

nh gi gii hn ng dng nguyn mu t c mc tiu nghincu;

Giai on th nghim: ph thuc vo mc tiu nghin cu c th c ccphng n khc nhau trong thu thp thng tin v qu trnh hot ng ca i

Chng

2



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Chng 2 NHNG KHAI NIEM C BAN CUA MO HNH HOA MOI TRNG 27

tng mi trng bng phng php kho st thc a hay tnh ton thnghim. Thu thp s liu thc a c mc tiu nhn c cc d liu cnthiu cho u vo ca m hnh. Thu thp s liu thc a gm cc bc:

- Xy dng mc tiu v yu cu i vi cc d liu.- Xy dng h thng tng ha x l s liu: cho php hin th thng

tin trong ch thi gian thc, tit kim thi gian v tin bc.

- Thu thp s liu vi s trgip ca cc my o khc nhau.Tnh ton th nghimc hiu l qu trnh ng dng cc m hnh tonkhc nhau sn sinh ra cc d liu lin quan ti cc trng thi mitrng. Trong giai on ny i tng thc c thay th hon ton bi

m hnh ton. Giai on ny gm cc bc sau:- Hnh thnh mc tiu th nghim vi s trgip ca m hnh ton- Chun b k hoch tin hnh tnh ton th nghim- Xy dng cc thut ton thc thi m hnh ton- Tin hnh tnh ton th nghim sinh ra cc d liu trng thi i

tng trong khng gian v theo thi gian.

Giaion din giigm cc bc:- Phn tch cc d liu tnh ton th nghim v so snh chng vi mc

tiu ban u;

- Lm sng t mt s trng thi c bit ca i tng mi trng cnghin cu;

- nh gi gii hn ng dng ca m hnh ton hc c s dng;



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Hnh 2-1. Cc giai on cbn ca qu trnh m hnh ha mi trng

C nhiu tc gi a ra cc phng php tip cn khc nhau v ccbc ca qu trnh m hnh ha mi trng. Tuy c mt sim khc bitnhng theo chuyn gia Jorgensen S.E /[3]/: Cc nh khoa hc khc tronglnh vc mi trng cng b nhng quy trnh kh khc nhau, nhng khikim tra chi tit pht hin rng ch c s khc bit nh gia cc quy trnh.Theo cch phn loi ca Jorgensen S.E. /[3]/ qu trnh m hnh ha gmcc bc sau y: xc nh bi ton, m hnh ton v gii s, phn tchnhy cm (sensitivity analysis), hiu chnh (calibration), kim nh

(verification) v xc nhn (validation).



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Bc u tin ca qu trnh m hnh ha l xc nh vn . y l cchduy nht xc nh gii hn nghin cu v tp trung ngun lc vo trngtm ca vn thay v phn tn sc lc vo cc hot ng khng cnthit.

V th bc u tin trong quy trnh m hnh ha l xc nh bi ton vvic xc nh ny s cn phi c gii hn bi cc yu t khng gian,thi gian v h sinh thi c xem xt (mt hay nhiu hn mt). Vic xcnh ranh gii ca bi ton theo khng gian v thi gian thng d hn, vv th r rng hn, so vi vic nhn dng cc h sinh thi c lin quantrong m hnh.

Hnh 2.2 th hin cc bc ca qu trnh m hnh ha mi trng c

Jorgensen S.E p dng /[3]/. Vic thc hin theo s ny khng phi ld dng vi nhng ngi mi bt u hc cch xy dng m hnh (theoJorgensen S.E.) v cn phi c thch nghi t t v c hon chnh theothi gian.

Vic xc nh s lng cc h sinh thi c lin quan tham gia qu trnh mhnh ha t c mc chnh xc c th ch p nhn c so vi

phm vi hay mc tiu ca m hnh l rt kh, t nht l i vi nhngngi mi bt u. Do thiu d liu nn giai on u ch c tha vo

xem xt mt s t h sinh thi. Sau khi c s b sung d liu cng nhcn thit phi lu chi tit hn, cc h sinh thi khc sc b sung,a vo nghin cu.

Trong gii chuyn gia lm m hnh cng thng din ra tranh lun vphc tp ca m hnh. C kin cho rng gii thch cc hin tngphc tp cn phi b sung cc tham s tham gia m hnh v nh vy trongphng trnh s xut hin nhiu thnh phn mi. Tuy nhin, rt tic hinnay cha c phng php ton hc mnh c th gii c cc

phng trnh phc t p. Ngoi ra, m hnh cng phc t p n cng chanhiu thng s, khi mc khng n nh ca m hnh cng tng. Bncnh nhiu thng s phi o c v kim tra hoc bng qu trnh quanst ti hin trng, hoc trong phng th nghim hoc bng qu trnh hiuchnh, qu trnh ny mt ln na li da trn nhng kt quo c ti hintrng. Vic kim tra thng s rt him khi hon chnh. Trong trng hpc sai s th nhng li ny c a vo m hnh v cui cng s dn ntnh khng n nh ca m hnh. Vn kh khn trong vic la chnmc phc tp ph hp ca m hnh sc tho lun trong rt nhiu



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cng trnh. y l vn cn c bit quan tm trong qu trnh m hnhha mi trng sinh thi.

Xc nh vn Xc nh h thng

S nim

a ra cc cng thc tonm t qu trnh

Phn tch nhy

Phn tch nhyln th hai

Hiu chnh

Xc nhn

p dng m hnh nh lmt cng c khoa hc hay

tin hnh don

Xc nhn qu trnh don

Thu thp d liu

nh gicc m hnh con

o lngchuyn su

Hnh 2-2. Mt qu trnh m hnh ha mang tnh th nghim.

V mt l thuyt, nh trnh by trn, cn thit phi thu thp d liuphc v cho m hnh. Hnh 2-2 cho thy rng vic kim tra cc m hnhcon v qu trnh o c chuyn su nn c thc hin sau bc phn tch nhy ln u tin. Tic rng c rt nhiu nh lp m hnh khng c ngun d liu c th thc hin c iu ny, nn h buc phi trnhthc hin hai bc ny v thm ch c bc phn tch nhy ln th hai.Jorgensen S.E. khuyn co rng cn phi thc hin theo th t t qu trnh

phn tch nhy, kim tra m hnh con v o c chuyn su v cuicng l phn tch nhy ln hai. Nn ch cc mi tn phn hi t bc



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phn tch nhy, bc hiu chnh v bc xc nhn n bc a ra cccng thc ton cho cc qu trnh v bc hnh thnh s nim. iuny cho thy qu trnh m hnh ha phi l mt qu trnh c tng tc lnnhau gia cc thnh phn.

D liu lun l mt yu cu bt buc trong m hnh ha (trong hu ht ccbc ca qu trnh m hnh ha u cn d liu). V nguyn tc, d liu chott c cc bin trng thi cn phi c xc nh. Mt cch l tng, ngilm m hnh nn quyt nh xem d liu no cn thit php trin m hnhda trn s nim. Cn lu ti kha cnh kinh t ca vn v ly sliu l mt qu trnh tn km.

Bc k ti p l xy dng cc cng thc ton hc m t cc qu trnh

trong h sinh thi. C nhiu qu trnh c m t bng mt phng trnhton hoc hn, v vic la chn phng trnh thch hp cho m hnh angxem xt l mt vn rt quan trng trong qu trnh m hnh ha.

D BAO

Xc nhbi ton

M hnh ton

v m hnh s

Phn tch

nhy cmHiu chnh

Kim nh

Thng qua

I TNGMI TRNG

datadata

data

data

Hnh 2-3. Cc bc m hnh ha theo Jorgensen S.E.



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Mt khi c h cc phng trnh ton th qu trnh kim nh mi(verification) c th c thc hin. Ti p theo, thc thi bc ny,chuyn gia xy dng m hnh cn phi tr li cc cu hi sau y:

1.Mo hnh co on nh trong mot thi gian dai hay khong?M hnh c chy trong mt khong thi gian di vi chu k l mt nmvi cng hm iu khin theo di xem gi tr ca cc bin trng thi cc duy tr mc tng i n nh hay khng. Trong sut giai onu, bin trng thi ph thuc vo gi tr ban u v m hnh cng nnc chy vi gi tr ban u tng ng vi gi tr di hn ca cc bintrng thi. Quy trnh ny cng c khuyn dng tm ra gi tr ban unu nh khng th bit hoc o c bng cc phng php khc.

2.Mo hnh co hoat ong nh mong i hay khong?V d nh nu i lng u vo l cc c cht, chng ta mong munnng c cht s cao hn trong c th cc loi ng vt cp cao hn.

Nu u ny khng xy ra, cho thy c mt vi cng thc ton b sai vcn phi c sa cha. Cu hi ny chng t rng trn thc t chng ta

bit c t nht mt s phn ng ca h sinh thi, iu ny cng khnglun ng nh th.

Nhn chung, trong giai on ny cn phi lm vic vi m hnh nhiu hnna. Qua nhng ln s dng nh th, nh lp m hnh c th lm quen vim hnh v cc phn ng ca n i vi nhng s xo trn. Cc m hnhni chung nn c xem nh l mt cng c th nghim. Cc th nghimc thc hin so snh kt qu ca m hnh vi kt qu quan st v sthay i cho m hnh c to ra ty theo trc gic v kin thc ca nhlp m hnh i vi cc phn ng ca m hnh. Nu nh m hnh hi lngvi s ha hp gia m hnh v kt qu quan st th h chp nhn m hnh

nh l mt s m t thch hp cho h sinh thi thc, t nht l trong phmvi cng vic quan st ca h.

Phn tch nh y (sensitivity analysis) ti p theo sau bc kim nh.Thng qua phn tch, nh lp m hnh c c cch nhn ng n v ccthnh phn nhy cm trong m hnh. Do , phn tch nhy l s cgng o c nhy ca cc thng s, cc hm iu khin v c cc mhnh con cho n cc bin trng thi cn quan quan tm trong m hnh.Th d, nu nh lp m hnh mun m phng nng cht c trong cth cn trng n tht do s dng thuc tr su, th h s la chn bin



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