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Environmental fate & pathways

Adsorption / desorption

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Administrative data

Endpoint:
adsorption / desorption
Type of information:
other: EU Risk Assessment
Adequacy of study:
other information
Reliability:
other: EU Risk Assessment
Rationale for reliability incl. deficiencies:
other: No reliability is given as this is a summary entry for the EU RAR.
Cross-reference
Reason / purpose:
reference to other study

Data source

Referenceopen allclose all

Reference Type:
secondary source
Title:
Unnamed
Year:
2003
Reference Type:
publication
Title:
Transport and fate of selected organic pollutants in a sandy soil.
Author:
Wilson JT, Enfield CO, Dunlap WJ, Cosby RL, Foster DA, Baskin LB
Year:
1981
Bibliographic source:
J. Environ. Qual., 10(4), 501-506.
Reference Type:
study report
Title:
Unnamed
Year:
1984
Reference Type:
publication
Title:
Hydrophobic sorption of polar organics by low organic carbon soils.
Author:
Southworth GR and Keller JL
Year:
1986
Bibliographic source:
Water, Air and Soil Pollution, 28, 239-248.
Reference Type:
publication
Title:
Interactions of halogenated hydrocarbons with soil.
Author:
Friesel P, Milde G, Steiner B
Year:
1984
Bibliographic source:
Fresenius Z. Anal. Chem., 319, 160-164.
Reference Type:
publication
Title:
Partitioning equilibria of nonionic organic compounds between soil organic matter and water.
Author:
Chiou CT, Porter PE, Schmedding DW
Year:
1983
Bibliographic source:
Environ. Sci. Technol., 17, 227.
Reference Type:
publication
Title:
Sorption of organic contaminants to a low carbon subsurface core.
Author:
Banerjee P, Piwoni MD, Ebeid K
Year:
1985
Bibliographic source:
Chemosphere 14(8), 1057-1067.
Reference Type:
publication
Title:
Ambient water quality criteria for chlorinated benzenes. EPA 440/5-80-028, PB81-117-392.
Author:
US EPA
Year:
1980
Bibliographic source:
US-Environmental Protection Agency, Washington DC
Reference Type:
publication
Title:
Handbook of environmental fate and exposure data for organic chemicals. Vol.1: Large production and priority pollutants.
Author:
Howard
Year:
1989
Bibliographic source:
Lewis Publ. Inc. Michigan.
Reference Type:
publication
Title:
Toxicity of selected chlorobenzenes to aquatic organisms.
Author:
Calamari D, Galassi S, Setti F, Vighi M
Year:
1983
Bibliographic source:
Chemosphere, 12(2), 253-262.

Materials and methods

Principles of method if other than guideline:
EU Risk Assessment
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent

Results and discussion

Any other information on results incl. tables

EU Risk Assessment (2003):

Conclusion on mobility and adsorption

1,2,4-TCB has a high adsorption capacity and the mobility in soil is expected to be low. However, because the degradation is slow in soil, 1,2,4-TCB may leach through sandy soils low in organic carbon content and reach groundwater.

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Mobility (Leaching studies)

Mobility was studied in a soil column study on a sandy soil in a 5 cm diameter and 140 cm high soil column. The soil contained 92% sand, 2.1% clay, 0.067% organic carbon and pH was 6.4. The soil column received 14 cm water per day over 45 days with the measured concentrations 3.4 and 0.57 mg/l 1,2,4-TCB. When 3.4 mg/l was applied, 46% was leached and 54% was degraded or not accounted for. When 0.57 mg/l was applied, 39% was found in eluate and 61% was degraded or not accounted for. The amount of volatiles was not determined (Wilson et al., 1981) although other studies indicated volatility to be essential. The study indicates that 1,2,4-TCB may leach into groundwater in sandy soils with low content of organic carbon. The potential for mobility is confirmed by recoveries in groundwater surveys.

 

Adsorption

The adsorption was studied according to OECD TG 106 in three soils; alfisol clay soil (0.76% organic carbon (OC)) using the concentration range 6-25µg/l, spodosol (sandy soil, 3.56% OC) in the concentration range 7 -127µg/l and entisol (clay soil 1.11% OC). The adsorption coefficient K values were 9.7, 82 and 10.7 and the estimated Koc values were 1,300, 2,300 and 970 for alfisol, spodosol and entisol, respectively (Broecker et al., 1984).

 

Three silty clay soils are used in an adsorption study of soils with low organic carbon content (1.2, 0.11 and 0.06% OC, respectively). The initial concentrations were 0.5 -1.0 mg/l. Koc values were estimated to be 885, 2,100 and 1,300, respectively for the three soils. (Southworth and Keller, 1986). The soils were all clay soils with a clay content of 60, 86 and 68%, respectively.

 

The Freundlich adsorption constant in a peaty soil (29% organic matter ) was 241.4 resulting in a Koc of 1,441 (Friesel et al., 1984). The difference between adsorption and desorption (Kdes 200.8) indicates a high degree of reversibility of sorption.

 

In the study by Chiou et al. (1983), the adsorption was studied in a silt loam with 1.9% and a log Kom of 2.70 is presented. Recalculating Kom to Koc would result in a Koc of 864.

 

In an American study on an alluvial soil with low carbon content,the adsorption distribution constant K varied between 1.2 and 11.6 (l/kg) and the Koc values were calculated to be in the range 800 to 2,490 with the mean ± SD to be 1,460 ± 440 (Banerjee et al., 1985)

 

Other reported Koc values were 2,042 (US EPA, 1980; Howard, 1989; Calamari et al., 1983) and 1,000 (Wilson et al., 1981). Higher values of Koc have been found in the literature and using the TGD estimation (log Koc = 0.81 log Kow + 0.1) would result in Koc = 2,401.

 

A QSAR estimation performed by first order molecular connectivity index resulted in an estimated Koc of 718 (PCKOC in EPIWIN, 1995; Meylan and Howard, 1994).

 

The average Koc value from the data mentioned in this report is 1,424 and a Koc of 1,400 is used in the risk assessment estimations.

Applicant's summary and conclusion