Kentucky State University

Poster Title

Heavy Metals in Edible Portions of Plants Grown in Sewage Sludge Amended Soil

Institution

Kentucky State University

Abstract

The use of municipal sewage sludge as a source of nutrients in crop production is increasing in the U.S. and worldwide. Recycling this material as a soil amendment would reduce the impact of disposal on environmental quality. Sewage sludge may contain excessive concentrations of heavy metals. Elevated concentrations of heavy metals in plants could expose consumers to excessive levels of potentially hazardous chemicals. A field study was conducted at Kentucky State University Research Farm. Eighteen plots of 22 × 3.7 m each were separated using metal borders and the soil in six plots was mixed with sewage sludge, six plots were mixed with yard waste compost, and the native soil in six plots were used for comparison purposes. During a subsequent 5-year study, plots were planted with potato (year 1), sweet pepper (year 2), broccoli (year 3), squash (year 4), and eggplant (year 5). The objectives of this investigation were: 1) to determine the concentration of seven heavy metals (Cd, Cr, Ni, Pb, Zn, Cu, and Mo) in sewage sludge and yard waste compost and 2) monitor heavy metal concentration in edible portions of plants at harvest. Concentrations of heavy metals in sewage sludge were below the USEPA limits. Analysis of potato tubers, peppers, and broccoli grown in sludge-amended soil showed that Cd, Cr, Ni, and Pb were not significantly different from control plants. Concentrations of Zn, Cu, and Mo were significantly greater in tubers and peppers grown in sludge compared to their respective controls. Zinc and Mo in broccoli heads were higher than their control plants.

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Heavy Metals in Edible Portions of Plants Grown in Sewage Sludge Amended Soil

The use of municipal sewage sludge as a source of nutrients in crop production is increasing in the U.S. and worldwide. Recycling this material as a soil amendment would reduce the impact of disposal on environmental quality. Sewage sludge may contain excessive concentrations of heavy metals. Elevated concentrations of heavy metals in plants could expose consumers to excessive levels of potentially hazardous chemicals. A field study was conducted at Kentucky State University Research Farm. Eighteen plots of 22 × 3.7 m each were separated using metal borders and the soil in six plots was mixed with sewage sludge, six plots were mixed with yard waste compost, and the native soil in six plots were used for comparison purposes. During a subsequent 5-year study, plots were planted with potato (year 1), sweet pepper (year 2), broccoli (year 3), squash (year 4), and eggplant (year 5). The objectives of this investigation were: 1) to determine the concentration of seven heavy metals (Cd, Cr, Ni, Pb, Zn, Cu, and Mo) in sewage sludge and yard waste compost and 2) monitor heavy metal concentration in edible portions of plants at harvest. Concentrations of heavy metals in sewage sludge were below the USEPA limits. Analysis of potato tubers, peppers, and broccoli grown in sludge-amended soil showed that Cd, Cr, Ni, and Pb were not significantly different from control plants. Concentrations of Zn, Cu, and Mo were significantly greater in tubers and peppers grown in sludge compared to their respective controls. Zinc and Mo in broccoli heads were higher than their control plants.