Fig. 4: Absorbance spectrum of Metilox (green) and light spectrum of the pond illumination (water surface) with and without additional UV A/B-fluorescent tubes (red, black, resp.). Wave length classifi-cation acc. DIN 5031 T7) (below)

®

®l Metilox hydrolyses rapidly under semi-natural conditions.The hydrolysis

rate is in the range of the laboratory study (Tab.1).

l Metilox and Metilox acid were not persistent at room temperature.

l Negligible concentrations of Metilox + Metilox acid were detected in

sediment and macrophytes (<0,5 % of initial concentration).

l Low concentrations of Metilox occurred in periphyton (<2% of initial

concentration).

l Besides Metilox acid most probably further smaller, polar metabolites

were formed, but not quantified for the mesocosm systems until now.

l Under additional UV-light the dissipation of Metilox acid in water was

accelerated.

l The calculated k (Fig. 5) is higher in comparison to the photodeg

laboratory test result, if converted to natural sunlight irradiation.

l The mathematical model describes the measured data very well (Fig 6).

l Metilox behaved like a water soluble substance. Thus, the model can

be simplified accordingly Fig.5 (red marked).

® ®

® ®

®

®

®

Experimental and modeled degradation ®

and distribution of Metilox in pond mesocosm a a a a b c

Meinecke. S. , Feibicke, M. , Mailahn, W. , Berghahn, R. , Hennecke, D. , Focks, A.

Introduction

Materials & MethodsPond designSize: length 690 x width 325 x height 250 cm

3Water volume: 20-21 m

Artificial light: mean 13,000 lx, in one pond additional

UV-fluorescent tubes (see Fig. 2)

Ground: sand covered with natural fine sediment

Macrophytes: e.g. Myriophyllum verticillatum,

Potamogeton nodosus

Identified and assumed PBT (Persistent, Bioaccumulative, and Toxic) substances are in general highly lipo-philic and may rapidly adsorp at organic particels and surface areas in aquatic systems. Hence, only a very small part of the corresponding chemical is dissolved in the water phase. Moreover, a sub-group of PBTs is instable in water due to abiotic hydrolysis and photodegradation as demonstrated in laboratory standard tests. Metilox® (methyl 3-(3,5-di-tert.-butyl 4 hydroxyphenyl) propionic acid) seems a suitable model sub-stance of this sub-group. Metilox® is a synthesis intermediate, but by now it is also used as an antioxidant in plastics and oils. Metilox® is poorly soluble, has been classified by the manufacturer as persistent and was therefore temporarily suspected to be a PBT-candidate. However, it hydrolyses in water to 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid (Metilox® acid) and probably undergoes photodegradation in the air (DT :19 h calculated by AOPWIN). 50

The crucial question arises whether the adsorption at particles may slow down or hinder the abiotic degra-dation under semi-natural conditions. For that reason, fate of Metilox® was investigated in large pond mesocosm systems with and without particle-bound application and with and without UV-light. The kinetic rate constants were calculated using a mathematical fate model, which had been designed for typical PB-substances (see also Poster TU 162). These rates were then compared to rate constants of photodegradation and hydrolysis data, which had been generated in laboratory studies of the IME.

Results

Fig. 8: Fate of Metilox and metabolites in the whole system (water, sediment, biofilm, and macrophytes)

®

Fig. 3: Application: Liquid dosing of solved Metilox (above), dosing of suspensed Metilox (below)

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®

Literature: [1] PBT-Working Group des ECB:

http://ecb.jrc.ec.europa.eu/DOCUMENTS/PBT_EVALUATON/PBT_sum065_CAS_6386-38-5.pdf[2] OECD SIDS: Metilox 2001 UNIEP Publications

http://www.inchem.org/documents/sids/sids/Metilox.pdf

Fig. 2: Scheme of the artificial lighting and macrophyte planting (UV A/B tubes only in selected ponds)

Fig. 5: Scheme of the fate model used for the calculation of kinetic rate constants. The red marked flows are the main processes of dissi-

pation of Metilox®

Discussion l No influence of mode of application on hydrolysis of Metilox was found.

l In comparison to the laboratory results no inhibiton of direct photolysis

by particles could be observed. However, the inhibition may have been

superimposed by other processes (e.g. indirect photolysis) and may be

differ with the trophic status of the corresponding surface water.

l Abiotic degradation of Metilox may be a relevant process in the

environment.

l Only low concentrations of Metilox and Metilox acid were detected in

sediment and biota.

l Further metabolites have to be quantified.

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l In contrast to the literature, Metilox was degradable in this study.

l Mathematical kinetic models may provide useful indications for kinetic

processes in fate studies even without the use of radiolabelling (no full

mass balance feasible).

Fig. 6: Results of the model calculations (lines) and experimental data; pond with UV-light and particle-bound application of Metilox

a Federal Environment Agency (UBA), email: stefan.meinecke@uba.de b Fraunhofer Institute Molecular Biology and Applied Ecology (IME)c Institute of Environmental Systems Research University of Osnabrück (USF)

Metilox & light spectra®

Application

®

®

Liquid Application: 1 pond (marked as: -Celite), initial concentration 25 µg/L;

Metilox solved in ethanol/acetonitrile as solubilizerParticle-bound application:2 ponds (marked as: +Celite), initial concentration 25 µg/L

and control; Metilox 250 mg/750 g on inorganic carrier

Celite 512 (diatomaceous earth), suspended in 200 L water.

Fig. 1: Indoor pond with UV-lamps (indicated by blue reflexion), pond shown without dust protection

Tab. 1: Results of the mesocosm and laboratory studies in comparison

(DT = DT of Metilox and Metilox -Acid in water, sediment 50 system 50

and biota relative to the start concentration); * DT calculated for 50

annual mean natural sunlight irradiation

® ®

Thanks to: ®

CIBA Chemicals for abandoning of Metilox , my colleagues D. Graßmann, S. Heller, C.

Kohls, S. Loth, N. Mühlenberg, T. Ottenströer, R. Schmiediche, I. Schmiedling for

technical support and B. Alscher, B. Katona, S. Rust, D. Schnee for GC-MS analysis

OH

O O

High pressurewater pump

Pressure-manometer

Flat Jet(stainless steel)

Adjustableinjector(stainless steel)

Laboratory bottle

Glas tube(Duran)

Tube (stainless steel)

Spray gun

Water tank(drinking water

with tracer)

High pressurewater pump

Pressure-manometer

Flat Jet(stainless steel)

Adjustableinjector(stainless steel)

Tube (stainless steel)

Spray gun

Stainless steel water tankwith stirring motor(drinking water,

anorganic tracer, Celite/ substance-mixture)

Myriophyllum

HQI-D 2000W

HQI-D 400W

UV-B 40WUV-A 36W

2 x Biolux 58W 2 x Biolux 58W

UV-B 40WUV-A 36W

AnalysisAnalysis by GC-MS(SIM) after solid phase extraction (ENV) and

derivatisation (PFB-Br).

Fate model

1,7 d System 8 d

Pond 4, 11°C+Celite, - UV

System 38 d

OECD Hydrolysis

System

OECD Photodeg.

System

Pond 3, 21°C+Celite, +UV

Pond 2, 21°C+Celite, -UV

Pond 1, 21°C-Celite, -UV

DT50Hydrolysis

1,3 d

1,1 d

DT50Photodeg.

-

-

-

-

9,7 d

DT50System

2,1 d

14 d

16 d

Pond 4, 11°C+Celite, -UV

OECD 111 25°C,Hydrolysis

OECD 316Photodeg.

1,7 d

5,5 d

2,9 d (pH 9)

8,2 d

38 d

-

15,2 d

2,7 d77 d *

M1 Sink Water(Volatisation, Metabolites)

M1 Water(Metilox® acid in

water)

P Sink Water(Volatisation, Metabolites)

P Water(Metilox ® in

Water)

M1 Sediment (Metilox ® acid in

sediment and biota)

P Sediment (Metilox ® in

sediment and biota)

M1 Sink Sediment(NER, Mineralisation,

Metabolites)

P Sink Sediment(NER, Mineralisation,

Metabolites)

k8 + kPhotodeg.

k1 (here: Hydrolysis)

k6 (Sorption) k5 (Desorption) k3 (Desorption)k2 (Sorption)

k7 ~ 0

k4k7

k9

Degradation

Degradation

System

250 300 350 400 450 5000

2

4

6

8

10

12

14

0.0

0.1

0.2

0.3

0.4

0.5

Spec

tral

irra

dia

nce

[µW

*cm

-2

*nm

-1

]

Wavelength [nm]

Pond -UV Pond +UV Metilox 2 mg/L Metilox acid 2 mg/L

UV-B UV-A

Abso

rban

ce

0 20 40 60 80 100 1200

10

20

30

40

50

60

70

80 Water

Metilox ModelMaker Metilox acid ModelMaker

Quota

inw

ater

rela

tive

toto

tali

nput[%

]

Days after application

0 20 40 60 80 100 1200.0

0.2

0.4

0.6

0.8

1.0 Sediment

Metilox ModelMaker Metilox acid ModelMaker

Quota

inse

dim

entre

lative

toto

talin

put[%

]

Days after application0 20 40 60 80 100 120

0

25

50

75

100

-Celite, -UV 21°C SFO +Celite, -UV 21°C SFO

95 % CL +Celite, +UV 21°C SFO +Celite, -UV 11°C SFO

Met

ilox

+M

etilo

xac

idre

lative

tost

artm

ass

[%]

Days after application

Simulationsanlage

FSA

Fließ- und Stillgewässer-