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Description of key information

Adsorption/desorption:

The adsorption coefficient Koc in soil and in sewage sludge of test chemical was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals. The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately weighing 4 mg of test item and diluted with Acetonitrile up to 10 ml. Thus, the test solution concentration was 400 mg/l. The pH of test substance was 6.5. Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor. The reference substances were chosen according to functional similarity with the test substance and calibration graph prepared. The reference substances were 4-chloroaniline, Aniline, 2,5 -Dichloroaniline, Naphthalene, 1,2,3-trichlorobenzene, phenanthrene having Koc value ranging from 1.96 to 4.09. The Log Koc value of test chemical was determined to be 3.486 ± 0.004 dimensionless at 25°C.This log Koc value indicates that the substance has a strong sorption to soil and sediment and therefore have negligible to slow migration potential to ground water.

Additional information

Adsorption/desorption:

Various experimental key and supporting studies of the test chemical were reviewed for the adsorption end point which are summarized as below:

 

In an experimental study from study report (2018),the adsorption coefficient Koc in soil and in sewage sludge of test chemical was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals. The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately weighing 4 mg of test item and diluted with Acetonitrile up to 10 ml. Thus, the test solution concentration was 400 mg/l. The pH of test substance was 6.5. Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor. The reference substances were chosen according to functional similarity with the test substance and calibration graph prepared. The reference substances were 4-chloroaniline, Aniline, 2,5 -Dichloroaniline, Naphthalene, 1,2,3-trichlorobenzene, phenanthrene having Koc value ranging from 1.96 to 4.09. The Log Koc value of test chemical was determined to be 3.486 ± 0.004 dimensionless at 25°C.This log Koc value indicates that the substance has a strong sorption to soil and sediment and therefore have negligible to slow migration potential to ground water.

 

Another adsorption study was conducted for evaluating the adsorption capacity of test chemical onto two different soils, i.e, silt clay soil (BC) and sandy loam soil (DL) (CHENXI WU et. al., 2009). The study was performed using the batch equilibrium method in accordance with OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method). Test chemical was purchased from Sigma-Aldrich (St. Louis, MO). Test chemical conc. used for the study were0.1, 0.4, 0.8, 1.4, and 2.0 mg/L, respectively. Two soils were used during the study. One was silt clay soil (BC)and the other was sandy loam soil (DL).A silt clay soil (BC) and a sandy loam soil (DL) were collected from the top layer (0-20 cm) in two fields with no biosolids application history in Lucas county, northwestern Ohio. The soil samples were air-dried, gently disaggregated, and sieved to a particle size of≤2 mm. Biosolids were aerobically digested sludge generated at a local wastewater treatment plant (Oregon, OH), which uses activated sludge treatment techniques. Samples were taken directly from a field at the time of biosolids application. Biosolids contained 37.2 g L-1 total suspended solids and 20.5 g L-1 volatile suspended solids and had a pH of 7.9. locally. The biosolids-amended soils (BCB and DLB) were air-dried and passed through a 2 mm sieve. Soil pH was measured in 0.01 M CaCl2 at a ratio of 1:2 (w/v) and texture was determined using the pipet method. Soil organic matter (SOM) content was measured by loss on ignition at 450°C for 4 h. Total organic carbon (TOC) content and cation exchange capacity (CEC) were determined by Spectrum Analytic Inc. (Washington Court House, OH).All soil samples were stored in plastic bags in dark conditions at room temperature (23± 3°C) for less than a month before use.50 ml glass centrifuge tubes, sealed withTeflon-lined screw caps were used as a test vessel for the study. In a preliminary experiment, sorption kinetics were investigated by determining the liquid phase concentration at 2, 4, 8, 24, 48, 72, and 120 h. After 48 h, concentration varied by <5%; thus, 48 h was chosen as the apparent equilibrium time for the sorption experiments. In a spiked control experiment, sorption on test vessel surfaces was observed for test chemical; therefore, both aqueous phase and sorbed phase concentrations were analysed as recommended in the OECD Guidelines. In the sorption experiment, soil samples (1 g, dry weight) were mixed with 40 mL of 0.01 M CaCl2 solution containing 0.1% NaN3 (w/v) in 50 mL glass centrifuge tubes, sealed with Teflon-lined screw caps, and agitated for 24 h using a reciprocal shaker. NaN3 was used to inhibit the activity of microbes. The soil slurry was then spiked with 0.04 mL of standard solution prepared in acetone (final acetone content=0.1%) to achieve concentrations of 0.1, 0.4, 0.8, 1.4, and 2.0 mg/L. After agitation for 48 h, samples were withdrawn and centrifuged at 1500gfor 20 min. Aliquots of 0.5 mL of supernatant were transferred into 2 mL amber glass vials and diluted with 0.5 mL of methanol to reduce sorption to the vials. The remaining supernatant was decanted, and soil samples were then freeze-dried and extracted using accelerated solvent extraction (ASE) with a Dionex ASE 200 system. Briefly, freeze-dried samples were mixed with Ottawa sand and transferred into 11 mL extraction cells. The cells were sealed at the bottom with glass fiber filters, filled with Ottawa sand to the top, and tightened with screw caps. The prepared cells were extracted with methanol using the following conditions: preheat, 0 min; static, 5 min; flush, 60%; cycles, 2; purge, 120 s; oven temperature, 80°C; pressure, 1500 psi. The extracted samples were collected in 60 mL glass vials. Final volume was about 20 mL. Aliquots of 1 mL extracted samples were transferred into amber glass vials. Extraction recoveries were >80% for both compounds with<10%relative standard deviation. Test vessel was agitated for 24 h using a reciprocal shaker. Blank samples without spiking were also included. All experiments were peformed in duplicate. Prepared samples were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS).The Freundlich Kf values for the test chemical in the two soils were different. For the test chemical, the KF value of test chemical on two soil ,i.e, silt clay soil (BC) and sandy loam soil (DL) was determined to be 799 µg1-nLn/Kg (457-1140) and 2624 µg1-nLn/Kg (1381-3867), respectively. The adsorption coefficient (Koc) value of test chemical onto two different soils, i.e, silt clay soil (BC) and sandy loam soil (DL)were 48865 (logKoc = 4.688) and 64037 (logKoc = 4.8), respectively. This Koc value indicates that the test chemical has a very strong sorption to soil and sediment and therefore have negligible migration potential to ground water.

 

In an supporting study,the adsorption coefficient of test chemical was determined in five different types of soils ray, drummer, Spinks , Lintonia and sediment lake 24 by using batch equilibrium method (secondary source NTRL report, 1980). The initial concentration of test chemical was 5 10, 20, 35 and 50 ppb. The tubes were capped, mixed on a Vortex, and placed on a gyratory shaker in the absence of light at 25oC. Three tubes from each of the five test chemical solution concentrations were removed from the shaker at 24 and 48 hours. The tubes were agitated on a Vortex shaker and centrifuged at 11,000 rpm for 30 minutes. Duplicate 1.0 mL samples of the supernatant were analyzed for 14 C activity by liquid scintillation counting method .Soil/sediment samples were extracted twice using 2 mL Burdick and Jackaon UV grade methanol. Methanol extracts were evaporated under nitrogen at 85 oC. Extracted test chemical was resolubilized in 3 mL methanol and counted by liquid scintillation methods. The adsorption coefficent koc value of test chemical was determined to be 53000,210000, 56000, 88000 and 210000 (log koc = 4.724, 5.322, 4.748, 4.944 and 5.322 respectively)  in different soil samples namely ray, drummer, Spinks , Lintonia and sediment lake 24 respectively by using batch equilibrium method. On the basis of log koc values it is concluded that test chemical very strong sorption to soils and negligible migration potential to ground water.

 

For the test chemical from authoritative databases (2017), adsorption study was conducted for evaluating the adsorption capacity of test chemical onto agricultural soil. Agricultural soil (characteristics 20% clay, 69% silt and 11% sand) was obtained from Corrstown, Co. Dublin, Ireland. The adsorption coefficient (Koc) value of test chemical onto agricultural soil was determined to be 12,000 L/Kg (logKoc = 4.08). This Koc value indicates that the test chemical has a strong sorption to soil and sediment and therefore have negligible to slow migration potential to ground water.

 

In an additional supporting study from peer reviewed journal (W. E. GLEDHILL, 1975), percent adsorption of test chemical was determined by batch equilibration method in this study the test chemical used was radio-labelled at parachloro aniline ring of test chemical. Adsorption experiment was carried out in flasks containing activated sludge and test chemical at concentration 200 µg/L and 20 µg/L and were shaken on a rotary shaker for 2 h at room temperature after which the suspensions were centrifuged and the residual dissolved test chemical in the supernatant assayed by using Scintillation counting. The percent adsorption of test chemical of equilibration at 18-20oC temperature activated sludge was 61-96 in 2 hrs. On the basis of percent adsorption value it is concluded that test chemical has strong sorption to sludge and therefore has negligible to slow migration potential to ground water.

 

On the basis of above results of test chemical (from study report, peer reviewed journals, secondary source and authoritative databases), it can be concluded that the logKoc value of test chemicalwas evaluated to be ranges from 3.486 to 5.32, indicating that the test chemical has a strong to very sorption to soil and sediment and therefore have negligible to slow migration potential to ground water.