Accumulation of Lead and Arsenic by Lettuce Grown on Lead-arsenate Contaminated Orchard Soils

Abstract

Lead-arsenate was used to control codling moth (Cydia pomonella) in apple (Malus sylvestris Mill) orchards from the 1900’s to the1960’s. Lead and arsenic are generally immobile and remain in the surface soil. Some orchard lands are being used for vegetable crop production. There are concerns of lead and arsenic accumulation in vegetables crops grown in these soils. Objectives were to 1) determine lead and arsenic uptake by lettuce and 2) determine the translocation into lettuce leaves. Lettuce (Lactuca sativa L) was grown for 60 days in four orchard soils (Bagstown, Hudson, Spike and Cashmont) with total lead and arsenic ranging from 350-961 and 93-291 mg kg^-1 respectively. Plants were harvested and separated in younger and older leaves, rinsed and dried. Yield reduced to 18, 11, 38 and 31 percent for plants grown on Bagstown, Hudson, Spike and Cashmont soils respectively. Tissue lead and arsenic concentrations were higher in the plants grown on the lead-arsenate soils compared to control. Lead and arsenic concentrations ranged from 0.44 to 3.91 and 4.65 to 24.1 mg kg^-1 respectively. Unlike arsenic levels in water, there are no established standard for arsenic in food; therefore, it is difficult to determine if arsenic levels observed in this study should be of concern to the consumer. Until there are established standard limits for arsenic in food, care should be taken when these soils are used for lettuce production without soil remediation. Further studies are needed to determine what fraction of lead and arsenic in lettuce is bioaccessible when consumed.