Accumulation of lead and arsenic by carrots grown on four lead-arsenate contaminated orchard soils

Authors: Codling, Eton; Chaney, Rufus; Green, Carrie

Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2012
Publication Date: 2/15/2015
Citation: Codling, E.E., Chaney, R.L., Green, C.E. 2015. Accumulation of lead and arsenic by carrots grown on four lead-arsenate contaminated orchard soils. Journal of Plant Nutrition. 38(4):509-525. DOI: 10.1080/01904167.2014.934477.

Interpretive Summary: There are concerns of possible transfer of lead and arsenic from crops grown on orchard soils with histories of lead arsenate use to humans. The objective of this study was to determine the uptake of arsenic and lead by three cultivars of carrots. Carrots were grown on four orchard soils with histories of lead arsenate use. A soil with no history of lead arsenate use was used as the control. Total soil arsenic and lead concentrations in contaminated soils ranged from 93 to 291 and 350 to 961 mg kg-1 respectively. Arsenic concentrations in peeled carrot roots grown on the orchard soils ranged from 0.38 to 1.64 mg kg-1 dry weight (DW) compared to 0.05 mg kg­1 DW for those on the control soil. Lead concentrations in peeled carrot roots grown on the orchard soils ranged from 2.67 to 7.3 mg kg-1 DW, compared to 0.19 mg kg-1 DW for the control soil. Carrot lead concentrations were in the order of peeled carrot roots > carrot tops > carrot peel, while arsenic concentrations were in the order of carrot tops > carrot peel > peeled carrot roots. This study demonstrated that carrots will accumulate lead in the root, which may become a human health risk when consumed. However, Pb in food is much less well absorbed by humans than Pb in water; further studies are needed to determine what fraction of lead and arsenic in such carrots are bioavailable to humans.

Technical Abstract: Concerns have been raised about possible human food chain transfer of contaminants resulting from crops grown on orchard soils with histories of lead arsenate use. The objective of this study was to determine the uptake of arsenic and lead by three cultivars of carrots. Carrots were grown on four orchard soils with histories of lead arsenate use. A soil with no history of lead arsenate use was used as the control. Total soil arsenic and lead concentrations in contaminated soils ranged from 93 to 291 and 350 to 961 mg kg-1 respectively. Carrot yields were highest for crops grown on Bagstown and Hudson soils. Arsenic concentrations in peeled carrot grown on the orchard soils ranged from 0.38 to 1.64 mg kg-1 dry weight (DW), compared to 0.05 mg kg­1 DW for those on the control soil. Lead concentrations in peeled carrot roots grown on the orchard soils ranged from 2.67 to 7.3 mg kg-1 DW, compared to 0.19 mg kg-1 DW for the control soil. Carrot lead concentrations were in the order of peeled carrot roots > carrot tops > carrot peel, while arsenic concentrations were in the order of carrot tops > carrot peel > peeled carrot roots. This study demonstrated that carrots will accumulate lead in the root, which may become a human health risk when consumed. However, Pb in food is much less well absorbed by humans than Pb in water; further studies are needed to determine what fraction of lead and arsenic in such carrots are bioavailable to humans.