Influence of fertilizer and sewage sludge compost on yield and heavy metal accumulation by lettuce grown in urban soils

Abstract

Previous research has demonstrated that many urban soils are enriched in Pb, Cd and Zn. Culture of vegetable crops in these soils could allow transfer of potentially toxic metals to foods. 'Tanya' lettuce (Lactuca sativa L.) was grown in pots of five urban garden soils and one control agricultural soil to assess the effect of urban-soil metal enrichment, and the effect of soil amendments, on heavy metal uptake by garden vegetables. The amendments included NPK fertilizer, limestone, Ca(H2PO4)2, and two rates of limed sewage sludge compost. Soil Cd ranged from 0.08 to 9.6 mg kg(-1); soil Zn from 38 to 3490 mg kg(-1); and soil Pb from 12 to 5210 mg kg(-1). Lettuce yield on the urban garden soils was as great as or greater than that on the control soil. Lettuce Cd, Zn and Pb concentrations increased from 0.65, 23, and 2.2 mg kg(-1) dry matter in the control soil to as high as 3.53, 422 and 37.0 mg kg(-1) on the metal-rich urban garden soils. Adding limestone or limed sewage sludge compost raised soil pH and significantly reduced lettuce Cd and Zn, while phosphate fertilizer lowered soil pH and had little effect on Zn but increased Cd concentration in lettuce. Urban garden soils caused a significant increase in lettuce leaf Pb concentration, especially on the highest Pb soil. Adding NPK fertilizer, phosphate, or sludge compost to two high Pb soils lowered lettuce Pb concentration, but adding limestone generally did not. On normally fertilized soils, Pb uptake by lettuce was not exceptionally high until soil Pb substantially exceeded 500 mg kg(-1). Comparing garden vegetables and soil as potential sources of Pb risk to children, it is clear that the risk is greater through ingestion of soil or dust than through ingestion of garden vegetables grown on the soil. Urban dwellers should obtain soil metal analyses before selecting garden locations to reduce Pb risk to their children.

Assessing potential dietary toxicity of heavy metals in selected vegetables and food crops

“…Metal contamination of garden soils may be widespread in urban areas due to past industrial activity and the use of fossil fuels (Chronopoulos et al, 1997;Sánchez-Camazano et al, 1994;Sterrett et al, 1996;van Lune, 1987;Wong, 1996). Heavy metals may enter the human body through inhalation of dust, direct ingestion of soil, and consumption of food plants grown in metal-contaminated soil (Cambra et al, 1999;Dudka and Miller, 1999;Hawley, 1985).…”

Assessing potential risk of heavy metal exposure from consumption of home-produced vegetables by urban populations.

“…Metal contamination of garden soils may be widespread in urban areas due to past industrial activity and the use of fossil fuels (Chronopoulos et al 1997;SanchezCámazano et al 1994;Sterrett et al 1996;van Lune 1987;Wong 1996). Heavy metals may enter the human body through inhalation of dust, direct ingestion of soil, and consumption of food plants grown in metal-contaminated soil (Cambra et al 1999;Dudka and Miller 1999;Hawley 1985).…”

Bioaccumulation of heavy metals in cane rat (Thryonomys swinderianus) in Ogun State, Nigeria

“…Metal contamination of garden soils may be widespread in urban areas due to continuous industrial activities and the use of fossil fuels (Chronopoulos et al, 1997). Several studies have shown that the concentrations of heavy metals in vegetation and natural rodent populations are generally correlated with environmental pollution (Schleich et al, 2010;Hawley, 1985;Sánchez-Camazano et al, 1994;Sterrett et al, 1996;Van Lune, 1987). Heavy metals which usually got transferred unto man and have highly adverse effects are lead, cadmium, copper, chromium, selenium and mercury (Wong, 1996).…”