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Description of key information

Biodegradation in water:

Two batch assays were conducted to screen the test chemical for their effect on methanogenesis . Assay was performed using helium-flushed, 70-ml glass serum bottles (each containing 50 ml of liquid culture) sealed with thick butyl rubber stoppers and aluminum crimps .All incubations took place in the dark at 22oC, and the bottles were shaken manually each day. For each assay, triplicate serum bottles were prepared in three experimental series as follows:

(1) seed blank control (without any electron donor added)

(2) primary electron donors (either 1,800 mg/L glucose or 1,800 mg/L lactate plus 90 mg/L yeast extract) as reference; and

(3) primary electron donors and test chemical at 200 mg/L (0.33–0.42 g COD/L)

The inoculum used was methanogenic cultures which was obtained from contaminated sediment sample from the Bayou d’Inde, a tributary of the Calcasieu River near Lake Charles, Louisian For decades, this tributary received discharges of industrial pollutants, including chlorinated compounds such as HCB and hexachlorobutadiene

After incubation Gas samples were removed from the culture headspace using a gas-tight syringe and analyzed for methane by gas chromatography.

Methane produced by day 7 as a percentage of the total methane produced in 82 d of incubation was 52% by using methane production as Parameter in 7 days by using methanogenic culture lactate feed culture in anaerobic condition. By considering this value test chemical was considered to be inherently biodegradable.

Biodegradation in water and sediments:

Estimation Programs Interface (EPI Suite, 2018) prediction model was run to predict the half-life in water and sediment for the test chemical. If released in to the environment, 15.1 % of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of test chemical in water is estimated to be37.5 days (900 hrs). The half-life (37.5 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is low whereas the half-life period of test chemical in sediment is estimated to be 337.5 days (8100 hrs). However, as the percentage release of test chemical into sediment is less than 2% (i.e., reported as 1.02%) indicates that test chemical is not persistent in sediments.

Biodegradation in soil:

The half-life period of test chemical in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (EPI suite, 2018). If released into the environment, 83.8 % of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of test chemical in soil is estimated to be 75 days (8640 hrs). Based on this half-life value of test chemical, it is concluded that the chemical is persistent in the soil environment and the exposure risk to soil dwelling animals is low

Additional information

Biodegradation in water:

Experimental studies have been reviewed from different sources for test chemical to determine biodegradability of test chemical and their results are summarized below.

The first experimental study was reviewed from Environmental Toxicology Chemistry Journal (1999) in this study the Two batch assays were conducted to screen the test chemical for their effect on methanogenesis . Assay was performed using helium-flushed, 70-ml glass serum bottles (each containing 50 ml of liquid culture) sealed with thick butyl rubber stoppers and aluminum crimps .All incubations took place in the dark at 22oC, and the bottles were shaken manually each day. For each assay, triplicate serum bottles were prepared in three experimental series as follows: (1) seed blank control (without any electron donor added) (2) primary electron donors (either 1,800 mg/L glucose or 1,800 mg/L lactate plus 90 mg/L yeast extract) as reference; and (3) primary electron donors and test chemical at 200 mg/L (0.33–0.42 g COD/L) The inoculum used was methanogenic cultures which was obtained from contaminated sediment sample from the Bayou d’Inde, a tributary of the Calcasieu River near Lake Charles, Louisian For decades, this tributary received discharges of industrial pollutants, including chlorinated compounds such as HCB and hexachlorobutadiene .After incubation Gas samples were removed from the culture headspace using a gas-tight syringe and analyzed for methane by gas chromatography. Methane produced by day 7 as a percentage of the total methane produced in 82 d of incubation was 52% by using methane production as Parameter in 7 days by using methanogenic culture lactate feed culture in anaerobic condition. By considering this value test chemical was considered to be inherently biodegradable.

To support the results of above mentioned study another study was reviewed from Water Science technology Journal (1998)in this study Serum bottle assays were conducted to screen the test chemical for their ability to enhance or inhibit Methanogenesis to determine biodegradability of test chemical , were performed using He-flushed 70-mL glass serum bottles sealed with thick butyl rubber stoppers and aluminum crimps (Wheaton, Millville, NJ), each containing 50 mL culture. All incubation occurred in the dark at 22°C with the bottles shaken daily. The glucose-fed culture was used in the first serum bottle assay, while the lactate-fed culture was used in the second assay. Experimental series of serum bottles were prepared in triplicates as follows: seed blank (without any electron donor added) for control; primary electron donors (either 1800 mg/L of glucose or lactate, plus 90 mg/L yeast extract, to result in a loading of 1.92 g COD/L) for reference; primary electron donors amended with surfactant at 200 rug/L (0.33042 g COD/L) to assess the effect of test chemical on the methanogenesis rate and extent; and surfactant at 200 mg/L without additional electron donors to assess the degradability of the test chemical when present as the exogenous carbon source. Each bottle contained biomass expressed as organic carbon in the amount of 280 mg C/L for the glucose-fed culture and 230 mg C/L for the lactate-fed culture. The inoculums used in this study was two hexachlorobenzene (HCB) dechlorinating cultures were developed at 22°C us ing anaerobic media and contaminated estuarine sediment as inoculum . These mixed, methanogenic cultures were maintained in 9 L. (6L liquid volume) sealed glass reactors with a 14-day fill-and-draw cycle resulting in an average hydraulic retention time of 84 days. One culture was fed glucose (333 mg/L) while the other was fed lactate (333 mg/L) during each feeding cycle (7-9 days). Total gas production volume was determined by water displacement using a graduated buret and corrected for daily variations in atmospheric pressure. Methane was determined using an HP5890 Series II gas chromatograph (Hewlett Packard, Palo Alto, CA).

The percent degradation (% conversion) of test chemical was determined to be 42 % and 23 % by using Glucose fed culture and lactate feed culture as inoculums respectively by considering methane production as parameter at 22 oC temperature. On the basis of percent degradation value test chemical is considered to be biodegradable.

To further support the results of above mentioned study another study was reviewed from Journal Chemosphere (1994) in this study the Biodegradability of test chemical was determined by using different methods of OECD namely (DOC die away, Manometric respirometric and Closed bottle test) in 28 days. Initial test chemical concentration was 40 mg DOC/L, 100 mg/L and 2-10 mg/L respectively. The percent biodegradation of test chemical was determined to be 40, 45 and 18 % by different methods such as DOC die away , Mano- metric respirometric test and close bottle test. By considering percent degradation value it is concluded test chemical is inherently biodegradable in nature. Biodegradability of test chemical was determined by using different methods of OECD namely (DOC die away, Manometric respirometric and Closed bottle test) in 28 days. Initial test chemical concentration was 40 mg DOC/L, 100 mg/L and 2-10 mg/L respectively. The percent biodegradation of test chemical was determined to be 40, 45 and 18 % by different methods such as DOC die away , Mano- metric respirometric test and close bottle test. By considering percent degradation value it is concluded test chemical is inherently biodegradable in nature.

By considering the results of all the studies mentioned above it is concluded that test chemical is inherently biodegradable in nature.

Biodegradation in water and sediments:

Estimation Programs Interface (EPI Suite, 2018) prediction model was run to predict the half-life in water and sediment for the test chemical. If released in to the environment, 15.1 % of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of test chemical in water is estimated to be37.5 days (900 hrs). The half-life (37.5 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is low whereas the half-life period of test chemical in sediment is estimated to be 337.5 days (8100 hrs). However, as the percentage release of test chemical into sediment is less than 2% (i.e., reported as 1.02%) indicates that test chemical is not persistent in sediments.

Biodegradation in soil:

The half-life period of test chemical in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (EPI suite, 2018). If released into the environment, 83.8 % of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of test chemical in soil is estimated to be 75 days (8640 hrs). Based on this half-life value of test chemical, it is concluded that the chemical is persistent in the soil environment and the exposure risk to soil dwelling animals is low