Toxicity of profenofos to the springtail, Folsomia candida, and ammonia-oxidizers in two agricultural soils.

Extensive use of organophosphorus insecticide profenofos (PFF) for agricultural and house-hold purposes has led to serious environmental pollution, with potential risk to organisms in the ecosystem. This study examined the toxicity of PFF to the soil springtail Folsomia candida and ammonia-oxidizers through a series of toxicity tests conducted on two agricultural soils. It was found that the survival, reproduction, hsp70 gene expression of F. candida and the soil potential nitrification rate (PNR) were sensitive to the PFF, whereas no apparent change was observed in the abundance of ammonia-oxidizers. The reproduction of F. candida was the most sensitive endpoint (mean 0.10 mg/kg of EC(50) value) for PFF, although the test was more time-consuming. The results of the acute toxicity tests suggested that the survival of F. candida could be considered as the most suitable bioindicator for fast screening of PFF toxicity because of its fast and easy test procedure. In addition, the hsp70 gene expression in F. candida and the PNR could be used as important parameters for assessment of PFF toxicity. The threshold concentration based on the obtained endpoints differed in the two soils, and consequently the soil property should be considered in toxicity assessments of contaminated soils.