Effects and risk assessment of linear alkylbenzene sulfonates in agricultural soil. 4. The influence of salt speciation, soil type, and sewage sludgeon toxicity using the collembolan Folsomia fimetaria and the earthworm Aporrectodea caliginosa as test organisms

Sewage sludge applied to agricultural soils often contains linear alkylbenz ene sulfonates (LAS) in the range of 1 to 10 g/kg dry weight, and their tox icity to relevant soil organisms should, therefore, be assessed to ensure s afe use of sewage sludge as a fertilizer. Studies of LAS toxicity to soil o rganisms are few, and to our knowledge, factors that may influence the toxi city in the field have not been studied in detail. In this paper, we report on the influence of speciation of LAS in the test solution added to soil ( soluble Na-LAS vs poorly soluble Ca-LAS or Mg-LAS), the influence of soil t ype, and the modifying effects of sludge amendment on the toxicity of LAS; These issues were investigated using reproduction of Collembola and growth of juvenile earthworms as test parameters. Speciation of the LAS added to t est soil did not have any influence on toxicity for any of the test species . Likewise, in three different agricultural soils (sand, loam, and clay), w e found almost equal toxicities. The LAS added to test soil in a sludge-wat er suspension was equally toxic as when it was added in an aqueous solution . However, anaerobic incubation for 7 and 14 d of the LAS-sludge suspension (with no decay of LAS) caused the toxicity to increase almost threefold in both collembolan and earthworm. The relationships between soil constituent s, bioavailability, and toxicity are also discussed.