ABSTRACT
Amendment of agricultural soils with municipal sewage sludges provides a valuable source of plant nutrients and organic matter. Nevertheless, addition of heavy metals and risks of eutrophication continue to be of concern. Metal behaviour in soils and plant uptake are dependent on the nature of the metal, sludge/soil physico-chemical properties and plant species. A pot experiment was carried out to evaluate plant production and heavy metal uptake, soil heavy metal pools and bioavailability, and soil P pools and possible leaching losses, in agricultural soils amended with sewage sludge for at least 10 years (F20) compared to non-amended soils (control). Sewage sludge application increased soil pH, N, Olsen-extractable-P, DOC and exchangeable Ca, Mg and K concentrations. Total and EDTA-extractable soil concentrations of Cu and Zn were also significantly greater in F20, and soil metal (Cu, Mn and Zn) and P fractionation altered. Compared to the control, in F20 relative amounts of acid-extractable (Mn, Zn), reducible (Mn, Zn) and oxidisable (Cu, Zn) metal fractions were greater, and a dominance of inorganic P forms was observed. Analyses of F20 soil solutions highlighted risks of PO4 and Cu leaching. However, despite the observed increases in metal bioavailability sewage sludge applications did not lead to an increase in plant shoot concentrations (in wild plants or crop species). On the contrary, depending on the plant species, Mn and Zn tissue concentrations were within the deficiency level for most plants.
Subject(s)
Metals, Heavy/metabolism , Phosphorus/metabolism , Plants/metabolism , Sewage , Soil , Biomass , Copper/metabolism , Manganese/metabolism , Plant Development , Zinc/metabolismABSTRACT
BACKGROUND: In spring of 1998, an acute gastroenteritis outbreak, which mainly affected preschool children, took place in Guadarrama (Community of Madrid, Spain). METHODS: A descriptive and analytical (cases and controls) study of the outbreak was done. Stool samples of the cases were taken to microbiological investigation. The tap water getting system of the municipality was inspected and samples were collected to microbiological analysis. RESULTS: Twenty one children from 0 to 5 years-old had liquid diarrhea which lasted more than five days. A significant statistical association was found within tap water consumption and gastroenteritis [OR = 5.73 (1.18-43.30); p < 0.05]. It did not have association with other variables investigated. Cryptosporidium parvum (Cp) oocysts were detected in stool samples of eight cases. Deficiencies were observed in the tap water getting and treatment system of the municipality but no oocysts were found in the analysis of the water. CONCLUSIONS: The results of the epidemiological investigation support that the source of the gastroenteritis outbreak was tap water, likely contaminated with Cp. While this parasite was not detected in the analysis of the water, it is explainable for the difficulties which this technique involves. In our review similar descriptions of outbreaks have not been found in Spain, but it seems that this reports are not infrequent in neighbour countries. Therefore, Cp should be borne in mind in diagnostic and management of these situations.
