Ecotoxicological assessment of organic wastes using the soil collembolan Folsomia candida

Domene X., Alcañiz J.M., Andrés P. (2007) Ecotoxicological assessment of organic wastes using the soil collembolan Folsomia candida. Applied Soil Ecology. 35: 461-472.
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Doi: 10.1016/j.apsoil.2006.10.004

Resum:

The reproduction test with the collembolan Folsomia candida is used as a tool to evaluate the ecotoxicological potential of organic wastes currently applied to soil. Seven organic wastes (dewatered sewage sludges, thermally dried sewage sludges, composted sewage sludges, and a thermally dried pig slurry) were tested. These wastes had different origins, treatments, and pollutant burdens, and were selected as a representative sample of the wide variety of wastes currently generated. F. candida showed varied sensitivity depending on the waste, but also depending on the endpoint assessed. Reproduction was more sensitive than survival, although no correlations between reproduction and physico-chemical parameters and pollutant burden could be found. On the other hand, mortality was directly related to the lack of stability of wastes, probably reflecting the toxicity of end-products such as ammonium. Body length was not shown to be a sensitive endpoint for waste testing, as it was neither affected nor even stimulated by waste concentrations. Organic matter, pH, and electrical conductivity varied with waste concentration in soil-waste mixtures, although their effect on collembolan performance was expected to be low and part of the complex effect exerted by wastes when applied to real soils. Selection of the water content is the most problematic aspect in waste testing, as it may affect the performance of test organisms. In this study, a qualitative approach for water content selection in waste testing was considered to be the most suitable. Treatment of wastes affected composition and toxicity. Composting of sewage sludge increased its stability, compared to the initial sludge, but decreased its non-persistent organic pollutant burden and toxicity. On the other hand, thermally dried wastes from sludge and pig slurry displayed high toxicity, mainly attributable to their low stability. The results from the study indicate the inability of chemical methods to predict the effects of complex mixtures on living organisms with respect to ecotoxicity bioassays, but also the need for stabilization treatments of organic wastes prior to their reuse in soils. © 2006 Elsevier B.V. All rights reserved.

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Feeding inhibition in the soil collembolan Folsomia candida as an endpoint for the estimation of organic waste ecotoxicity

Domene X., Natal-Da-Luz T., Alcañiz J.M., Andrés P., Sousa J.P. (2007) Feeding inhibition in the soil collembolan Folsomia candida as an endpoint for the estimation of organic waste ecotoxicity. Environmental Toxicology and Chemistry. 26: 1538-1544.
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Doi: 10.1897/06-623R.1

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Despite the increasing quantities of organic wastes that are being reused in soils, there are few studies that focus on the selection of bioassays for the ecotoxicological risk assessment of organic wastes to soils. In the present study, differences in feeding inhibition in the soil collembolan Folsomia Candida were evaluated as an ecotoxicological endpoint for the assessment of risk to soils amended with polluted organic wastes. Seven organic wastes (dewatered sewage sludges, thermally dried sewage sludges, composted sewage sludges, and a thermally dried pig slurry) were tested. These wastes had different origins, treatments, and pollutant burdens, and were selected as a representative sample of the wide variety of wastes currently generated. A clear dose response was observed for this parameter, with an increase in percentage of individual feeding inhibition with increased doses of organic wastes. More significantly, feeding inhibition correlated highly with mortality and reproduction inhibition in the different wastes. Composted sludges displayed the lowest toxicity, followed by thermally dried sludge and dewatered sludge. Thermally dried pig slurry showed the highest toxicity for feeding, with lower median effective concentration (EC50) values than the lowest dose tested. Among waste physicochemical parameters and pollutants, low organic matter stability appeared to be the main predictor of potential adverse effects on soil fauna, because it correlated significantly with feeding inhibition and mortality. Furthermore, feeding inhibition tests were run over a short exposure time (less than 7 d), which, together with the results obtained, makes this bioassay a good screening tool for organic waste toxicity. © 2007 SETAC.

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A multi-criteria evaluation of organic amendments used to transform an unproductive shrubland into a Mediterranean dehesa

Tarrasón D., Ortiz O., Alcañiz J.M. (2007) A multi-criteria evaluation of organic amendments used to transform an unproductive shrubland into a Mediterranean dehesa. Journal of Environmental Management. 82: 446-456.
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Doi: 10.1016/j.jenvman.2006.01.002

Resum:

Environmental and health problems associated with the use of digested sewage sludge hinder its application and encourage the introduction of additional treatments such as composting and thermal drying. The aim of this paper is to assess the possibility of using three different types of sewage sludge (digested, composted and thermally dried) to improve soil fertility and enhance the transformation of an unproductive shrub land into a Mediterranean dehesa for grazing purposes and also to reduce wildfire risk. In total, 10 t ha-1 of dry matter of three types of sewage sludge were spread on the soil surface of 4×5 m field plots, and then seeded with a mixture of grasses. Effects on soil fertility and plant growth were monitored over 2 years. The results show that all three types of sludge application had a significant effect on vegetation cover, herbaceous biomass (2767.7±716.1 and 1735.0±299.7 kg ha-1 for digested sludge amended and control plots, respectively) and tree growth (0.41±0.108 cm year-1 on amended trees, 14.6% more than control trees). This study proposes the use of multi-criteria analysis to identify the most suitable fertilization alternatives and to assist in the decision-making process of sludge recycling. Because of the high degree of uncertainty and conflicting objectives associated with these decisions, multi-criteria evaluation tools make a valuable contribution to decision-making processes concerning sewage sludge applications. According to multi-criteria results, the composted sludge alternative is the most suitable. This is because all the objectives are achieved: an improvement in the properties and functions of the soil with a positive vegetation response as well as minimal economic cost and risk of toxicity. © 2006 Elsevier Ltd. All rights reserved.

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