Effects of sewage sludge organic matter amendment on the fate of pesticides in soils
Project co-ordinator: Dr. Metka Suhadolc
Sewage sludge, produced as a by-product of water treatment, may have different physical or chemical properties, depending on the treatment at each plant (mechanical treatment followed by one or more steps of biological stabilisation, and in some cases also anaerobic digestion of sludge). In recent years there has been a trend to increasing sewage sludge production, but the quantity of sludge that is actually used in agriculture has remained fairly (approx. 3300 t d.m.a-1).
Application of sewage sludge to agricultural land may be beneficial from two aspects: (i) sewage sludge as a waste is recycled and (ii) the organic content of soil is increased. Soil organic matter is recognised as one of the major active constituents controlling microbiological activity, as well as sorption and transport of pesticides in the soil. In general, a higher level of organic matter in soil increases adsorption and degradation of pesticides, and thus it is expected that leaching of pesticides to groundwater should decrease. However, the possible negative effects of heavy metals in sewage sludge on microbiological activity (pesticide degradation) need to be evaluated.
The fate of pesticides in the environment will be evaluated in a microcosmic soil system using the 14C technique, which enables their qualitative and quantitative determination. Important pathways of a pesticide such as degradation, including mineralisation, bound residue formation, volatilisation, mobility and leaching will be measured. Changes in the microbial community structure will be determined at the genotypic and phenotypic level, as both complementary approaches have been reported to be successful for assessing changes in the community structure exposed to the impact of pollutants in complex matrices such as soil. The availability of heavy metals in sewage sludge and in soil samples treated with sewage sludge will be determined using sequential extraction procedures, and when necessary using the eco-toxicity tests described in the Subproject “Remediation of lead, zinc and cadmium contaminated soil in Celje area”.
Collaborative organizations:
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