Chemistry and Phytotoxicity of Soil Trace Elements from Repeated Sewage Sludge Applications

Abstract

Municipal sewage sludges, or biosolids, can be applied to croplands to supply and recycle nutrients and organic C. Trace elements in sludges, however, may be of environmental concern. This study examines the long‐term consequences to crops and soil when loading phytotoxic levels of one or more trace elements to cropland. Municipal sewage sludges containing trace elements, including high concentrations of Cd, Cr, Cu, Pb, Ni, and Zn, were applied to cropland from 1977 to 1986 at three rates plus an untreated control. Plant and soil samples were collected between 1985 and 1990. These results report on yield and metal uptake of corn (Zea mays L.), sorghum‐sudangrass (Sorghum bicolor L. Moench × S. sudanese P. Stapf.), and soybean (Glycine max L.). Yields of all crops were reduced on one or more sludge treatments because of phytotoxic concentrations of soil trace elements, probably Zn and Ni. Phytotoxicity has continued since the last sludge application. Chemical fractionation of surface soils was performed using a sequential extraction technique and trace elements were measured in each of eight fractions. Cadmium, Ni, and Zn occupied soil fractions that were potentially available for plant uptake. Copper and Cr loadings increased the environmental availability of these two elements to a smaller extent. Loadings of Pb to the levels seen in this study did not appear to significantly increase its environmental availability. The Toxicity Characteristic Leaching Procedure (TCLP) and guidelines used to characterize hazardous wastes were inappropriate to use when testing soils for potential phytotoxic concentrations of trace elements or uptake of these elements into the food chain.

Alterações químicas em solos e crescimento de milho e feijoeiro após aplicação de lodo de esgoto

“…Para o Zn, este valor foi de 38 %, enquanto, para o Pb, 15 % do total adicionado pode tornar-se disponível. Os teores de metais pesados nas plantas de milho e de feijoeiro (Quadro 6) encontram-se abaixo dos limites tóxicos (Schimidt, 1997;Berti & Jacobs, 1996), motivo pelo qual não foram observados sintomas de fitotoxidez em nenhum dos tratamentos. O Zn foi o elemento que apresentou maior incremento de absorção com o aumento das doses de lodo aplicadas para ambas as culturas nos dois solos (Quadro 6).…”

Lead behavior in soil treated with contaminated sewage sludge and cultivated with maize

“…Silva (1995) observed no effect in metal concentration in the tissue and in the export of Cd, Cr, N, Pb and Se in the sugar cane stalk + leaves with the addition of sewage sludge. Berti and Jacobs (1996) stated that Pb was not detected in the plant in all crops evaluated. The sorption (adsorption and absorption) of Pb by the maize plant could be also attributed to its probable concentration in the roots (Malavolta, 1994) and low bioavailability (Zufiaurre et al, 1998;Berti and Jacobs, 1996;McBride, 1995;Hooda and Alloway, 1994).…”

“…Successive agricultural applications may result in accumulation of these elements in the environment and in the food chain: sewage ⇒ soil ⇒ plant ⇒ animal ⇒ man (Kabata -Pendias and Pendias, 1992). According to Berti and Jacobs (1996), sewage sludge may be used in agriculture for increasing product yield. However, sometimes it can present high metal concentration (Cd, Cu, Ni, Pb and Zn) that can cause serious problems in plants and its consumers.…”

Field and laboratory evaluation of soil quality changes resulting from injection of liquid sewage sludge

“…A great number of studies have been published which document the effects of sludge application on soil properties, nutrient availability and crop growth, heavy metal toxicity, degradation of organic pollutants, and contamination of surface and ground water. Studies of soil property changes have selectively focused on nutrient enrichment and de®ciency, organic matter dynamics, chemical toxicities, microbial and enzymatic activity and soil physical parameters (Metzger and Yaron, 1987;Smith, 1991;Berti and Jacobs, 1996;Smith, 1996;McBride et al, 1997). Sewage sludge application to soil generally improves soil fertility by increasing the soil organic matter, microbial activity and residual nitrogen and by improving soil physical properties.…”