Atmospheric Chemistry at Ole John Nielsen Department of Chemistry, University of Copenhagen.

Atmospheric Chemistry at

Ole John NielsenDepartment of Chemistry, University of Copenhagen

2

Outline1. Who am I?

2. What are the concerns on atmospheric emissions?

3. How do we study atmospheric chemistry?

4. Cases:

1. CFC alternatives

2. Trifluoroacetic acid (TFA) CF3COOH

3. Perfluoro organic acids (PFOAs)

4. Alternatives to the CFC alternatives

5. Conclusions

3

5.5M people43000 km2

1009M people3287000 km2

Why/How did I become interested inAtmospheric Environmental Chemistry?1954 Born1973 Began at UoC (chemistry and physics)1974 Important Atmospheric Year1978 M.Sc. and on to do a PhD at Risø Nat. Lab.1978-95 Risø National Laboratory1995-96 Ford Research Center Aachen, Germany1996-99 Risø National Laboratory1999-? Professor at UoC2007 Nobel Peace Prize together with Al Gore and 2500 scientists

Gas phase kinetics and reaction mechanisms - relevant to the atmosphere

IPCC – Intergovernmental Panel of Climate Change – India?

6

Acknowledgements

• Mr. Jens Sehested• Mrs. Trine Møgelberg• Mrs. Merete Bilde• Mrs. Lene Christensen• Mr. Jesper Platz• Mrs. Anne Toft• Mr. Mads Andersen• Mrs. Meshkat Javadi

• Tim Wallington (Ford)• Mike Hurley (Ford)• Jim Ball (Ford)• John Owens (3M)• Rajiv Singh (Honeywell)• Bob Waterland (Dupont)• Scott Mabury (Toronto)• Brian Scott (CanEnv)

7

What are the Concerns on Atmospheric Emissions ?

1. Radiation Forcing/Global Warming/Climate Change– (global)

2. Stratospheric Ozone Depletion (CFCs)– (global)

3. Tropospheric Oxidant Formation – (local-regional-global)

4. Harmful emissions and/or Harmful Degradation Products– (local-regional-global)– Example: 1984 Bhopal accident, methyl isocyante

• What do we need to know about a compound in order to quantify the environmental impacts ?

• "Guilty - until proven innocent"• We (the people of the Earth) have been extremely lucky (CFCs)

8

NO

CF3

hh

aq

HF+C(O)F2

CF3C(O)O2NO2

CF3C(O)O

CF3COOH

NO2NO

Decomp/h

hh

O2

CF3C(O)O2

CF3C(O)

aqCF3COF

Atmospheric degradation of HFC-134a

HCOF

OH.

CF3CFH.

CF3OH

RRH

NO2NO

CF3O

CF3O2

O2

HO2

O2CF3CFHO

CF3CFHOOH CF3CFHOONO2CF3CFHO2

CF3CFH2

NO2NO

OH

NO2HO2

O2

H2O

FNOFOx

FCOx

FNO2

hNO

h

O3

We need to know theatmospheric chemistry

9

And that is the research that we do:

• Atmospheric Science (Chemistry) Research

Investigations of chemical/physical processes

We use the lab and/or the field and/or modelling to provide a better understanding of atmospheric processes and composition.

• Will lead to better quantification of environmental impact• May not lead to a better environment

10

NO

CF3

hh

aq

HF+C(O)F2

CF3C(O)O2NO2

CF3C(O)O

CF3COOH

NO2NO

Decomp/h

hh

O2

CF3C(O)O2

CF3C(O)

aqCF3COF


HCOF

OH.

CF3CFH.

CF3OH

RRH

NO2NO

CF3O

CF3O2

O2

HO2

O2CF3CFHO


CF3CFH2

NO2NO

OH

NO2HO2

O2

H2O

FNOFOx

FCOx

FNO2

hNO

h

O3

11

ContainerInitiation Detection

How ?

• Laser Photolysis• 1 liter stainless steel• UV/VIS-absorption

– pm or diode array– microsec. resolution

• Kinetics

• Continuous photolysis• 100 liter Quartz• FTIR spectroscopy

– 26 m and 0.25 cm-1– min. resolution

• Kinetics and Products

12

How ?

To LeCroy and PC

Gas cell

Febetron

Xenon lamp

Monochromator

e-

Diode array

Photomultiplier

Shielding wall0 10 20 30 40

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.0

0.3

0.6

0.9

0.0

0.3

0.6

0.9

Wavenumber (cm-1)

800 1000 1200 1400 1600 1800 2000

0.0

0.2

0.4

Abs

orba

nce 10

A : Before UV irradiation

B : After UV irradiation

C : B - (0.49 x A)

laser

13

What problems are we interested in?

• How and why are compounds degraded or transformed in the atmosphere in certain ways?

– CFC alternatives– Trifluoroacetic acid (TFA) CF3COOH– Perfluoro organic acids (PFOAs)– Alternatives to the CFC alternatives

– Biofuels for transportation– Greenhouse gases in general– Formation of cloud condensation nuclei

14

What was the issue in 1974?

• Ask: “What happens with …..?” – and get the Nobel Prize (the real one)

• Rowland and Molina asked themselves

What happens to CFCs in the atmosphere?

CF2Cl2 does not react in the troposphere but is photolyzed in the stratosphere:

CF2Cl2 + hν → CF2Cl + Cl - and so what?

15

CFC-11CFCl3

CFC-12CF2Cl2

What was the problem?1974?1985?

What did the chemists have to do to protect the ozone?

Cl + O3 → ClO + O2

ClO + O → Cl +O2

--------------------------O + O3 → O2 + O2

16

• HCFC: Hydrochlorofluorocarbons: CHClF2

• HFC: Hydrofluorocarbons: CF3CFH2

• HFE:Hydrofluoroethers: CF3OCF2H

What did the chemists have to do to protect the ozone?

Make similar compounds with shorter lifetimes or make similar compounds with no Cl or both CHClF2 + OH → H2O + CClF2 → ……….

17

NO

CF3

hh

aq

HF+C(O)F2

CF3C(O)O2NO2

CF3C(O)O

CF3COOH

NO2NO

Decomp/h

hh

O2

CF3C(O)O2

CF3C(O)

aqCF3COF


HCOF

OH.

CF3CFH.

CF3OH

RRH

NO2NO

CF3O

CF3O2

O2

HO2

O2CF3CFHO


CF3CFH2

NO2NO

OH

NO2HO2

O2

H2O

FNOFOx

FCOx

FNO2

hNO

h

O3

Better in every way –But

18

CFC alternatives - Conclusions• 25 papers with the title ”Atmospheric Chemistry

of……”• last one in 1998 – we thought !

• The new compounds did not destroy ozone• The new compounds did not produce ozone in

the troposphere• The new compounds were more acceptable as

green house gases – good enough?• Some of the new compounds produced TFA

19

TFA (CF3COOH) IN THE ENVIRONMENTWhy are we interested ?

• pKa = 0.23

• Solubility > 10000 g/L

• Henry´s law constant 0.112 atm cm3/mole

• kOH = (1.7±0.5)x10-13 cm3molecule-1s-1 (68d)

• Other Sinks ? Bacteria ? No real sinks!

• Phytotoxic

• Atmospheric sources e.g.:– CF3CFH2, CF3CCl2H, CF3CFClH

• Analysis: Derivatization and GC-MS

20

Objective 1

• Compare the levels of TFA calculated to arise from known sources with those observed in the environment.

21

CF3COOH - KNOWN SOURCESCompound Name Molar yield Lifetime

years

Estimated

Flux (t/yr)

Estimated

Flux (t/yr)

CF3CHClBr Halothane 0.6 1.2 520

CF3CHClOCHF2 Isoflurane 0.6 5 280

CF3CHCl2 HCFC-123 0.6 1.5 < 760

CF3CHFCl HCFC-124 1.0 6.0 < 320

CF3CH2F HFC-134a 0.13 14.6 1200

Fluoropolymers 200

TFA (1000 t/y) Neg

Total 3080

22

CF3COOH - CONCENTRATIONS

• TFA found in oceans, rivers, lakes, fog, snow, rainwater and air samples (U.S., Germany, Israel, Ireland, France, Switzerland, Austria, Russia, South Africa, and Finland)

• TFA in rainwater in Bayreuth 1995 was 100 ng/L– Jordan, A.; Frank, H., Environ. Sci. Tech., 1999, 33, 522.

• Fog and rain 36 samples in 1994-1996 in California and Nevada contained 31-3779 ng/L TFA

– Wujcik, C. E.; Zehavi, D.; Seiber, J. N., Chemosphere, 1998, 36, 1233.

• TFA in ocean water (Pacific, Atlantic, Arctic) 20-250 ng/L– Wujcik, C. E.; Zehavi, D.; Seiber, J. N., Chemosphere, 1998, 36, 1233. – Scott, B. F. et al. at the Atmospheric Reactive Substances Symposium, April, 1999.

• No variation with depth down to 3000m (300years)– Scott, B. F. et al. at the Atmospheric Reactive Substances Symposium, April, 1999.

Pol

ar M

ixed

Lay

er

Pac

ific

Hal

oclin

e~

10 y

ears

Atla

ntic

Lay

er ~

25 y

ears

Bot

tom

La

yer

~3

00 y

ears

24

CF3COOH - BURDEN

• TFA in ocean water (Pacific, Atlantic, Arctic) 20-250 ng/L– Wujcik, C. E.; Zehavi, D.; Seiber, J. N., Chemosphere, 1998, 36, 1233.

– Scott, B. F. et al. at the Atmospheric Reactive Substances Symposium, April, 1999.

• The oceans: 1.4x1021 L• The oceans contain (0.3-3.5)x108 tonnes of TFA

25

CF3COOH - DILEMMA

• The oceans contain (0.3-3.5)x108 tonnes• TFA flux of 3080 tonnes/yr• 10000-100000 years to give current TFA levels• But – we have only used these compounds for 50 years?• Possible conclusions:

– concentration measurements are all wrong ?– Under-estimated the sources ? Unknow sources ?– Or both ?

26

Objective 2

• Have there been old/natural sources of TFA ?

28

Old Groundwater

Sample 13-4 13-5 13-6TFA (ng/l) 22 7 3remark

Sample D9-3 D9-4 D9-5TFA (ng/l) 3 15 5remark

Sample D10-4 D10-5 79.992TFA (ng/l) N.D. 2 N.D.remark

3000 year old, CFC contaminated

2000 year old, NOT CFC contaminated

* Water Resour. Res., 28 (1992) 2257

3000 year old, CFC contaminated*

30

Old Ice

Sample #1 #1 #2 #2TFA (ng/l) N.D. 0.5 N.D. N.D.remark 1250 meters = 3549 years old

31

Conclusions

• TFA is not a natural component of the freshwater hydrosphere !

• TFA from underwater volcanic activity ?

• Sources of TFA in ocean water need to be determined !

32

Long chain perfluorinated acids (PFCAs/PFAs) observed in fauna in urban and remote locations

PFOA (perfluorooctanoic acid) C7F15C(O)OH

PFNA (perfluorononanoic acid) C8F17C(O)OH

PFDA (perfluorodecanoic acid) C9F19C(O)OH

PFUA (perfluoroundecanoic acid) C10F21C(O)OH

F

F

F

F

F

F

F

F

F

F

F

F

F

FF

CC

FF

FF

FF

FF

FF

FF

PFPeA

OHO

F

F

PERSISTENCE ! – ASK ME ABOUT IT

33

Contamination Profile - Polar Bears (Sanikiluaq Isl.)

Box plots show the outliers, 10th, 25th, median, 75th and 90th centile.

n.d.<0.5

We’re0.0001% PFOS !

Martin et al. 2004

34

C10F21C(O)OH

35

No natural sources.

Water-soluble PFCA salts used in fluoropolymer processing.

Not released in significant quantities.

Presence of PFCAs in remote areas and in foxes suggests atmospheric source.

Where do long chain Perfluorocarboxylicacids

(PFCAs), CnF2n+1COOH come from?

36

PolyfluoroAlcohols are highly volatile!!!

Observed in the atmosphere

5504503502501505050.01

.1

1

10

100

1000

10000

Molecular Mass

Log

P (

Pasc

als

)

Hydrocarbon Alcohols

Fluorotelomer Alcohols

HC data from Daubert & Danner; FTOH data from Lei et al, J Chem Eng Data and Stock et al, ES&T, both in press.

FF

FFF

F

FFF

F

FF

F

C

FF

COH

F

F H

H

H

H

8:2 FTOH = 212 Pa

37

FTOH based coatings heavily used in consumer products;

*TRP Presentation toUSEPA OPPT. Nov 25, 2002US Public Docket AR226-1141

5x106 kg/yr40% in North America80% are in polymers*

Carpet Treatment

Polymer

Potential Sources?

Degradation

N C

F

F

F

F

F

F

F

F

F

F

F

F

F

FF

CH2

H2COH

F

F

F F

F F

F F

F F

F F

F F

F

FF

C

F FC

OHH H

H H

F

F

F

F

F

F

F

F

F

F

F

F

F

FF

CH2

H2C

F

F

OO

OO

F

F

F

F

F

F

F

F

F

F

F

F

F

FF

CH2

H2C

F

F

O

F

F

F

F

F

F

F

F

F

F

F

F

F

FF

Urethane EtherEster

CH2

H2C

F

F

Residual

38

Three necessary conditions:

(1) FTOH survive long enough for atmospheric transport

(2) FTOH degrade to give PFCAs

(3) Magnitude of PFCA formation must be significant

Use a FTIR Smog chamber

Research Question:

Does atmospheric oxidation of FTOHs contribute significantly to PFCA burden in remote locations?

39

UV irradiation of

FTOH/reference/CH3ONO/NO/air mixtures

FTOH = 4:2 FTOH, 6:2 FTOH, or 8:2 FTOH

reference = C2H2 or C2H4

CH3ONO CH3O + NO

CH3O + O2 HCHO + HO2

HO2 + NO OH + NO2

OH + FTOH products (1)

OH + reference products (2)

40

OH + FTOH products (1)

OH + reference products (2)

][reference[OH]k]reference[

]FTOH[]OH[k]FTOH[

ss2ss1

dt

d

dt

d

Integration gives:

t[OH]k]reference[

]reference[t[OH]k

]FTOH[

]FTOH[ss2ss1

t

toLn

t

toLn

FTOH and reference have equal exposure to OH radicals, hence:

t

to

2

1

t

to

][reference

][reference

k

k

[FTOH]

[FTOH]LnLn

41

Ln ([Reference]to/[Reference]t)0.0 0.5 1.0 1.5

0.0

0.1

0.2

0.3

0.4

0.5

0.6L

n([

F(C

F2C

F2)

n(C

H2)

2OH

] to/[F

(CF

2CF

2)n(

CH

2)2O

H] t)

C2H2

C2H4

OH + CnF2n+1CH2CH2OH → products (10)

OH + C2H2 → products (11)

OH + C2H4 → products (12)

Linear fits give k10/k11 = 1.18±0.15 and k10/k12 = 0.131±0.018.

Using k11 = 8.5 x 10-13 and k12 = 8.66 x 10-12 gives

k10 = (1.00±0.13) x 10-12 and (1.13±0.16) x 10-12 cm3 molecule-1 s-1.

Final value, k10 = (1.07±0.22) x 10-12 cm3 molecule-1 s-1.

No discernable difference in reactivity of OH radicals towards 4:2, 6:2, and 8:2 FTOH

42

Assuming:

atmospheric lifetime* for CH3CCl3 = 5.7 years

k(CH3CCl3 + OH) = 1.0 x 10-14 cm3 molecule-1 s-1

then

atmospheric lifetime* of CF3(CF2)nCH2CH2OH

(1.0x10-14)/(1.1x10-12) x 5.7 x 365 20 days.

* with respect to reaction with OH radicals

FTOH Lifetime Estimate

43

Other loss mechanisms?

Photolysis – is negligible

Rainout – estimated to be negligible

Dry deposition – lifetime estimated to be 8 years

Homogeneous reactions other than with OH - unlikely

Atmospheric lifetime determined by reaction with OH and is approximately 20 days.

44

Assuming 5m/s winds and a 20d lifetime, FTOHs could be transported over 8500 km

20 days… Long Enough for Long Range Transport?

Copenhagen to Detroit = 6500 km

45


(1) Do FTOHs survive atmospheric transport?

YES

(2) Do FTOHs degrade to give PFCAs?



46

0.00

0.05

0.10

0.15

0.20

0.25

IR A

bso

rban

ce

0.00

0.05

0.10

0.15

0.20

0.25

0.00

0.02

0.04

0.06

0.08

Wavenumber (cm-1)

700 900 1100 1300 1500 1700 1900

0.00

0.05

0.10

0.15

(A) before irradiation

(B) 10 sec irradiation

(C) Product

(D) CF3(CF2)3CH2CHO

FTIR study of 4:2 FTOH oxidation

CF3(CF2)3CH2CHO

is the major primary

product from Cl

atom and OH

radical initiated

oxidation of 4:2 FTOH

47

[CF3(CF2)3CH2CH2OH] / [CF3(CF2)3CH2CH2OH]0

0.0 0.2 0.4 0.6 0.8 1.0

[CF

3(C

F2) 3

CH

2C

HO

] /

[CF

3(C

F2) 3

CH

2C

H2O

H] 0

0.0

0.1

0.2

0.3

0.4

0.5

CnF2n+1CH2CHO is

reactive …Gives secondary

products …

CnF2n+1CH2CH2OH + OH CnF2n+1CH2C(•)HOH + H2O

CnF2n+1CH2C(•)HOH + O2 CnF2n+1CH2CHO + HO2

Secondary products:

C4F 9CHO,

C4F9CH2COOH

C4F9C(O)OOH

Secondary products are reactive …

48

0.00

0.02

0.04

0.06

0.08

0.00

0.10

0.20

0.30

0.40

0.50

0.60

IR A

bso

rba

nc

e

0.00

0.20

0.40

0.60

0.80

Wavenumber (cm-1)

1400 1600 1800 3500

0.00

0.10

0.20

0.30

(A) before irradiation

(B) 8.5 minutes irradiation

(C) residual

(D) CF3(CF2)3COOH

Tertiary products include:

COF2, CF3OH

C4F9COOH

Conclusion of FTIR experiments:

simulated atmospheric

oxidation of 4:2 FTOH (in absence

of NOx) gives a small (few %) yield

of C4F9COOH

49

FTIR data shows that in gas phase:

in absence of NOx

4:2 FTOH C4F9CHO C4F9COOH

Likely explanation, presence of HO2 radicals in absence of NOx because: HO2 + NO → OH + NO2 is a very fast reaction

Well established that CH3C(O)O2 + HO2 gives acetic acid and peracetic acid, ,

presumably CxF2x+1C(O)O2 + HO2 reaction gives CxF2x+1COOH and CxF2x+1COOOH.

Product study of CxF2x+1C(O)O2 + HO2 (x=1-4) to test this idea.

in presence of NOx

4:2 FTOH C4F9CHO C4F9COOH

50

IR spectra obtained before (A) and after

(B) 55 s of irradiation of a mixture of 18.8 mTorr C2F5C(O)H,

218 mTorr Cl2 and

2.8 Torr H2 in 700

Torr of air. The consumption of

C2F5C(O)H was 63%.

51

PFCAs are products of

CxF2x+1C(O)O2 + HO2 reaction

Offers reasonable

explanation of observed PFCA formation in 4:2

FTOH expts.

52

CF2

CF3

O

OO HO2+

CF2

CF3

O

OO

OO

H

CF2

CF3

O

OO

O

OH

C2F5C(O)OH + O3

CF2

CF3

O

OO

OO

H

C2F5C(O)OOH + O 2

CF2

CF3

O

OO

OO

H

C2F5C(O)O + O2 + OH

a b c

53


(1) Do FTOHs survive atmospheric transport?

YES

(2) Do FTOHs degrade to give PFCAs?

YES



55

Illinois Model and Michigan Model

Illinois – 2-D chemistry-transport model, zonal-averaged model of the chemistry and physics of the global atmosphere, 75 chemical species, 161 reactions, grid resolution 5 degrees of latitude and 1.5 km altitude, 8:2 FTOH emission assumed 500 tonnes per year, flux uniform in time and space over the

land area between 20 oN and 60oN

Michigan – “IMPACT” global 3-D, chemistry/transport model, 4 latitude by 5 longitude horizontal resolution, 46

vertical layers, 90 chemical species, 300 individual reactions, 8:2 FTOH emission assumed 1000 tons per year, with global

distribution assumed to be equal to that of propane.

56

Concentration of PFOA (in molecule cm-3) at 50 m.

altitude in the University of Michigan model (IMPACT) for (a) January and (b) July. The color scale extends from (a) 0 to 1.2x103 and (b) 0 to 3x103

molecule cm-3.

January

July

Results from Michigan

Integrating over the latitude range 65-90oN provides an estimate of 0.4

tonnes yr-1 for the PFOA

deposition flux to the Arctic.

Results from Illinois are

the same within uncertainties

57

PFCA - Conclusions1. Smog chamber experiments can be used to explain

why polar bears contain PFOA.

2. The results show that atmospheric oxidation of FTOHs makes a significant contribution to the PFCA burden in remote locations.

3. Front page of Environmental Science & Technology 2007

4. Future: Ice-core study on FTOHs and PFCAs (contamination from “teflon” ?)

58

Conclusions – if I am out of time

– CFC alternatives• New ozone friendly alternatives were found – However….

– Trifluoroacetic acid (TFA) CF3COOH• The TFA dilemma still needs to be solved

– Perfluoro organic acids (PFOAs)• PFOAs are formed from FTOH• The mechanism can explain observations

– Alternatives to the CFC alternatives• The is a continued effort finding more global warming

friendly compounds

59

Atm. residence time+ IR Absorbance

EnvironmentalFate

Alternatives to the alternatives (HCFCs and HFCs)

Cl or Br + O3

Ozone Depletion Greenhouse Gas

60

2005 Global Greenhouse Gas Emissions

% Contribution on CO2 Basis

Change since 1990

CO2 +1.6%

CH4 -18%

N2O -20%

FCs +19%

HFCs +154%PFCs -45%SF6 -62%

UNFCCC data for Annex I countries

61

Effect of Ether Oxygen on Atmospheric Lifetime

Atm. GWPCompound Lifetime (yrs) (100 Yr ITH) CH3CF3 (HFC-143a) 52 4,470 alkaneCH3OCF3 (HFE-143a) 4.3 756 ether

CF3CFHCF3 (HFC-227ea) 34.2 3,220CF3CFHOCF3 (HFE-227ea) 11 1,500

CF3CH2CF3 (HFC-236fa) 240 9,810CF3CH2OCF3 (HFE-236fa) 3.7 470

CF3CH2CHF2 (HFC-245fa) 7.6 1,030CF3CH2OCHF2 (HFE-245fa2) 4.9 659

62

Rf - O - Rh k(OH) (cm3molecules-1s-1)

(years)

n-C4F9 - OCH3 1.20 x 10-14 4.7

i-C4F9 - OCH3 1.54 x 10-14 3.7

n-C4F9 - OC2H5 6.4 x 10-14 0.9

i-C4F9 - OC2H5 7.7 x 10-14 0.7

C4F9-O-(CH2)3-O-C4F9 1.44 x 10-13 0.4

5.93 x 10-14 1.0

Atmospheric Lifetimes of Segregated HFEs

O CF

O

CF

F

F FFF

CH2CH3

CF3

CF3CF3CF3

63

Design of New Chemical Technology

Environmentalnon-ozone depletingshort atmospheric lifetimelow global warming potential

Performancestabilitycompatibilityboiling/freezing point

Safety low toxicitynonflammable

64

Potential Reductions in Greenhouse Gas Emissions

(on a CO2 basis)

C4F9OC2H5 HFE-569sfc2 (GWP=59)

HFC-43-10mee (GWP=1640)

C4F9OCH3 HFE-449sc1 (GWP=297)

PFC-5-1-14 (GWP=9300)

82% reduction 97% reduction

96% reduction 99% reduction

65

Conclusions

– CFC alternatives• New ozone friendly alternatives were found – However….

– Trifluoroacetic acid (TFA) CF3COOH• The TFA dilemma still needs to be solved

– Perfluoro organic acids (PFOAs)• PFOAs are formed from FTOH• The mechanism can explain observations

– Alternatives to the CFC alternatives• The is a continued effort finding more global warming

friendly compounds

Atmospheric Chemistry at

The End

Atmospheric Chemistry at Ole John Nielsen Department of Chemistry, University of Copenhagen.

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Transcript of Atmospheric Chemistry at Ole John Nielsen Department of Chemistry, University of Copenhagen.