Ecotoxicological assessment of organic wastes spread on land: Towards a proposal of a suitable test battery.

The land spreading of organic wastes in agriculture is a common practice in Europe, under the regulation of the Directive 86/278/EEC. One of the objectives of this Directive is to prevent harmful effects of organic wastes on soil, plants and animals. Despite this regulatory framework, there is still a lack of harmonized ecotoxicological test strategy to assess the environmental hazard of such wastes. The aim of this study was to provide a first step towards the a priori ecotoxicological assessment of organic wastes before their land use. For that purpose, nine different organic wastes were assessed using direct (i.e. terrestrial tests) and indirect (i.e. tests on water eluates) approaches, for a total of thirteen endpoints. Then, multivariate analyzes were used to discriminate the most relevant test strategy, among the application rates and bioassays used. From our results, a draft of test strategy was proposed, using terrestrial bioassays (i.e. earthworms and plants) and a concentration range between one and ten times the recommended application rates of organic wastes.

The use of soil mites in ecotoxicology: a review.

Mites, and especially soil-inhabiting ones, have been less studied than the other invertebrates used in bio-assays for the assessment of soil quality and the hazards of chemicals, although these organisms are included in the regulatory assessment scheme of pesticides. The recent advances in the development of test methods for soil mites groups have provided more information on their sensitivities towards chemicals, which needs to be presented for a more robust assessment of the current trends in soil mite ecotoxicology. Moreover, interestingly mite is the only taxa for which test methods were developed and standardized on predatory organisms. This review summarizes the different protocols for the assessment of chemicals using soil-inhabiting mites, including laboratory, semi-field and field studies. Among the data found in the literature, most of the chemicals assessed with mites were pesticides, while a few environmental samples were assessed with these organisms. Their sensitivities towards chemicals were then compared and discussed regarding other soil invertebrates. Finally, we conclude on the usefulness of soil mites in ecotoxicology, and provide future research trail in this area.

Improvement of the Caenorhabditis elegans growth and reproduction test to assess the ecotoxicity of soils and complex matrices.

A growth and reproduction test using the nematode Caenorhabditis elegans was recently standardized by the International Organization for Standardization (ISO). Performing the ISO 10872 protocol (2010) revealed some drawbacks when applied to soil or soil mixed with complex matrices. The authors propose some modifications to the current protocol to normalize the test conditions. An appropriate range of moisture conditions was determined as a percentage of the water-holding capacity (WHC) of the soil. According to the authors' results, C. elegans tests can be performed in the range of 60% to 100% WHC. To ensure that the modifications of the protocol did not affect the organisms' recovery, extraction ratios for the juveniles were subsequently estimated. The modified protocol was found to be as reliable as the standard one concerning recovery of juveniles (over 80%). The protocol was also applied to several chemicals to investigate their potential as reference chemicals for soil toxicity tests. Boric acid, copper chloride, and nickel sulfate showed deleterious effects in a concentration-dependent manner for the growth and reproduction of C. elegans. Finally, the modified protocol was used to assess the growth and reproduction of C. elegans in soil amended with a limed sewage sludge. The authors conclude that the C. elegans modified protocol is a promising tool for the assessment of soil toxicity as well as the toxicity of mixtures with complex matrices.