Registration Dossier

Administrative data

Endpoint:
field studies
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1980 - 1983
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The study was conducted between 1980 - 1983 at the Woods Hole laboratory which is internationally renowned for the standard of the work it produces. In addition the study is presented in a peer reviewed journal. Unfortunately, at the time this study was conducted there were no official guidelines for work of this type but the standard of reporting is adequate to make the results obtained acceptable.

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1983

Materials and methods

Test guideline
Qualifier:
no guideline available
Principles of method if other than guideline:
The study used MERL (Marine Ecosystems Research Laboratory) mesocosms consisting of fibreglass tanks (5.5m high, diameter 1.8m) filled with 13 cubic metres of Narragansett Bay seawater and associated planktonic and microbial communities. The tanks were mixed for two hours four times per day (tide and current simulation). Experiments were replicated to simulate spring conditions (temperature 8 - 16C), summer conditions (temperature 20 - 22C) and winter conditions (temperature 3 - 7C). In addition the effect of poisoning (mercuric chloride at 2mg/L) to eliminate biological activity was included in the study.

Application rates of materials under investigation ranged from 0.2 - 4.0ug/L equivalent to that expected in a moderately polluted estuary. The concentrations in the test systems were recorded for two months to determine their half life and the method of removal (degradation, volatilisation, precipitation, absorption/adsorption).
GLP compliance:
no
Remarks:
GLP had not been invented at thetime this study was conducted
Type of measurement:
Water samples were taken at intervals from 1 m below the surface in 2.0L glass bottles. Mercuric chloride was used as a preservative. Volatile materials such as 1,1,1-trichloroethane were removed by closed loop stripping followed by GC quantification using internal standards.
Media:
Seawater and associated biological communities.

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
no details available in the report

Results and discussion

Any other information on results incl. tables

Concentrations of volatile organic compounds in mesocosms showed seasonably variable declines which were generally considered the exponential although some compounds showed seasonal breaks associated with increased volatilisation. Compounds showing biodegradation generally disappeared much faster as temperatures rose. The results of the study showed that for chlorinated C2 hydrocarbons the main removal process is by volatilisation. This is demonstrated in the paper by the comparable release rates recorded for F-12 (which is not subject to biodegradation or absorption onto particulate matter) and materials in this group. The author's attribute the higher release rates in the winter period to the effect of bad weather increasing surface water movement whereas losses during the summer period can be attributed to increased temperatures. The authors consider that as surface movement in the mesocosm tanks will be appreciably less than that in the open estuary their estimates of losses may be appreciably less than is the case in practice. These results are at variance with those recorded in the laboratory studies where the effects of water movement are not fully taken into account. The results are shown in tables below.

Compound

8 - 16 C (spring)

20 - 22C (summer)

3 – 7C  (winter)

A

B

C

A

B

C

A

B

C

Benzene

1.4

-0.03

23

2.7

-0.22

3.1

3.0

-0.054

13

1,1,1 -trichloroethane

4.3

-0.029

24

3.5

-0.058

12

2.7

-0.063

11

Trichloroethylene

3.2

-0.025

28

2.4

-0.052

13

3.8

-0.045

15

Chlorobenzene

1.0

-0.033

21

0.6

-0.152

4.6

2.8

-0.053

13

F-12

-0.035

20

-0.035

13

A = concentration (mg/L) in the mesocosm measured by analysis after stripping at the start of the study.

B = removed rate constant (l)

C = DT50 (days) were volatilisation appears to dominate.

F-12 – dichlorodifluoromethane (Freon) - internal standard to confirm closed loop stripping procedure (confirmation of recovery).

Experimental results with non poisoned mesocosms 20 - 22C (summer)

Compound

Tank with HgCl2

Tank without HgCl2

A

B

C

A

B

C

Benzene

3.4

-0.101

6.9

3.6

*

*

1,1,1-trichloroethane

3.6

-0.6

11.5

3.1

-0.072

9.6

Trichloroethylene

3.2

-0.064

10.7

3.6

-0.081

8.6

Chlorobenzene

0.5

-0.08

8.9

0.7

* not possible to calculate.

Results of the study showed that 1,1,1-trichloroethane DT50 in marine estuaries is in the region of 24 days (spring), 11 days (winter) and 9.6 - 12 days in summer.

Applicant's summary and conclusion

Conclusions:
Results of the study showed that 1,1,1-trichloroethane DT50 in marine estuaries is in the region of 24 days (spring), 11 days (winter) and 9.6 - 12 days (summer).
Executive summary:

Although the study was conducted between 1980 - 1983 it is designed to take into account all possible components of removal of organic pollutants from the estuarine environment. As this is a Tier 3 study the results obtained include all possible interactions (volatility, absorption/adsorption, biodegradation etc) that contribute to the removal of these materials from the aquatic environment. For risk assessment purposes this study should be used in preference to laboratory studies where interactions between the various components of removal are not adequately addressed.