Registration Dossier

Environmental fate & pathways

Biodegradation in soil

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
biodegradation in soil: simulation testing
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The studies are very well documented in this peer-reviewed publication.
Justification for type of information:
Commercial LAS as present in primary sludge or anaerobically digested sludge from WWTPs in the United Kingdom. The LAS present in primary sludge or anaerobically disgested sludge may be of slightly different homolog distribution than commercially available for LAS, therefore the test material identity is marked as not being the same as that in section 1. Given that the analysis of the field samples showed evidence of LAS components, the composition is similar enough to justify readacross.
Qualifier:
no guideline followed
Principles of method if other than guideline:
The disappearance of LAS from sludge-amended soils was investigated from 51 fields on 24 farms in the Thames Water Authority, U.K. Annual sludge spreading averaged 6 ton/ha. Application of sludge was made by subsurface injection, surface spreading onto arable land with or without ploughing, or surface spreading onto pasture land. Regular sampling was conducted for up to 122 days. LAS concentrations in the soil were analyzed with HPLC.
GLP compliance:
not specified
Test type:
field trial
Radiolabelling:
no
Oxygen conditions:
not specified
Soil classification:
not specified
Details on soil characteristics:
51 fields on 24 farms in the Thames Water Authority, U.K. Annual sludge spreading averaged 6 ton/ha. Application of sludge was made by subsurface injection, surface spreading onto arable land with or without ploughing, or surface spreading onto pasture land.
Duration:
<= 122 d
DT50:
> 7 - < 22 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Temperature not given
Transformation products:
not specified
Evaporation of parent compound:
not specified
Volatile metabolites:
not specified
Residues:
not specified
Details on results:
In fields not recently spread with sludge, the concentrations of LAS found in the sludge amended soil were generally less than 1 mg/kg. This represents an estimated loss of LAS from soil of >98%. In fields recently spread, the concentrations in soil are in the range of <0.2 to 20 mg/kg, representing losses of LAS between 70 and 99% of the estimated total cumulative load. The identity of the degradation products was not analyzed.

Half-lives compare well with those for ultimate degradation in lab soil tests (with 14-C-evolution), indicating that the degradation of LAS does not lead to the formation of significant levels of break-down intermediates in soil.

Conclusions:
The authors conclude that overall the data indicate that an adequate safety margin exists between the concentrations of LAS in sludge-amended soils and those likely to affect the growth of crop plants.
Executive summary:

The disappearance of LAS from sludge-amended soils was investigated from 51 fields on 24 farms in the Thames Water Authority. Sludge was applied by subsurface injection, or surface spreading. Sampling was conducted for up to 122 days. In fields not recently spread with sludge, the concentrations of LAS found in the sludge amended soil were generally less than 1 mg/kg.  In fields recently spread, the concentrations in soil are in the range of 0.2 to 20 mg/kg, representing losses of LAS between 70 and 99% of the estimated total cumulative load. 

Description of key information

The disappearance of LAS from sludge-amended soils was investigated from 51 fields on 24 farms in the Thames Water Authority (United Kingdom). Sludge was applied by subsurface injection or surface spreading. Sampling was conducted for up to 122 days. The disappearance of LAS from sludge-amended soils was reported as having a Half-life = between 7 and 22 days.

Key value for chemical safety assessment

Additional information

The disappearance of LAS from sludge-amended soils was investigated from 51 fields on 24 farms in the Thames Water Authority (United Kingdom). Sludge was applied by subsurface injection or surface spreading. Sampling was conducted for up to 122 days. In fields not recently spread with sludge, the concentrations of LAS found in the sludge amended soil were generally less than 1 mg/kg. In fields recently spread, the concentrations in soil were in the range of <0.2 to 20 mg/kg, representing losses of LAS between 70% and 99% of the estimated total cumulative load. The authors conclude that overall the data indicate that an adequate safety margin exists between the concentrations of LAS in sludge-amended soils and those likely to affect the growth of crop plants. Half-lives compare well with those for ultimate degradation in lab soil tests (with14-C-evolution), indicating that the degradation of LAS does not lead to the formation of significant levels of breakdown intermediates in soil.