Accumulation of lead and arsenic in Malabar spinach (Basella alba L.) and sweet potato (Ipomoea batatas L.) leaves grown on urban and orchard soils.

Authors: Codling, Eton; ONYEADOR, JEFFREY - University Of Pittsburgh

Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2017
Publication Date: 9/21/2017
Citation: Codling, E.E., Onyeador, J. 2017. Accumulation of lead and arsenic in Malabar spinach (Basella alba L.) and sweet potato (Ipomoea batatas L.) leaves grown on urban and orchard soils. . Journal of Plant Nutrition. 40(20):2898-2909.

Interpretive Summary: Migration of people of different ethnic backgrounds to U.S. urban areas has resulted in different ethnic vegetable crops being grown in urban gardens. There are concerns that some ethnic vegetable crops may accumulate heavy metals when grown on urban soils. The objective of this study was to evaluate the accumulation of lead, arsenic, copper, manganese, zinc and phosphorus in shoots of Malabar spinach (Basella alba L.) and sweet potato (Ipomoea batatas L.) when grown on lead and/or arsenic contaminated soil amended with phosphorus. Soils were collected from an urban area, orchard and a wooded area (control) with total lead concentration 1120, 272, and 6.27 mg kg-1, and arsenic of 6.92, 90, and 0.69 mg kg-1 respectively. Yield of both crops was greater when grown on the urban soil compared with the control or orchard soil. Both Malabar spinach and sweet potato tissue lead concentration was significantly higher in plants grown in the contaminated soils. Arsenic concentration was highest in plants grown on the orchard soil. Sweet potato stem had higher arsenic and lead concentrations compared with the leaf or tuber. Tissue copper, manganese, zinc and phosphorus concentrations in both crops were below or within the range found in vegetable crops. This study demonstrated that Malabar spinach did not accumulate lead or arsenic in its leaves or stems. However, sweet potato stems accumulate lead to a greater extent than do the leaves or tubers, which may present a human health risk. Consumption of sweet potato stems should be avoided when consuming sweet potato leaves grown as a vegetable on urban soils with elevated levels of lead and arsenic.

Technical Abstract: Migration of people of different ethnic backgrounds to U.S. urban areas has resulted in different ethnic vegetable crops being grown in urban gardens. There are concerns that some ethnic vegetable crops may accumulate heavy metals when grown on urban soils. The objective of this study was to evaluate the accumulation of Pb, As, Cu, Mn, Zn and P in shoots of Malabar spinach (Basella alba L.) and sweet potato (Ipomoea batatas L.) when grown on Pb and/or As contaminated soil amended with P. Total soil Pb concentration in a Pb contaminated urban garden soil, a Pb/As contaminated orchard soil, and an uncontaminated control soil were 1120, 272, and 6.27 mg kg-1, respectively, while the corresponding values for soil As were 6.92, 90, and 0.69 mg kg-1. Yield of both crops was significantly greater when they were grown on the urban soil compared with the control or orchard soil. For both Malabar spinach and sweet potato, tissue Pb concentration was significantly higher than control values on both contaminated soils, while tissue As was higher only on the orchard soil. For Malabar spinach, tissue Pb was 7.7 and 40 times higher on the urban and orchard soils, respectively, compared to the control soil, while for sweet potato the corresponding increases were 2.5 and 8.7 times. Tissue As of plants grown on the orchard soil was 15 times higher than the control value in Malabar spinach and 65 times higher in sweet potato. Arsenic and Pb concentrations were significantly higher in stems of sweet potato compared with the leaf or tuber, while in Malabar spinach the levels of these elements were much higher in the root than in the above-ground tissue and did not differ significantly between leaf and stem. This study demonstrated that Malabar spinach did not accumulate Pb or As in its leaves or stems. However, sweet potato stems accumulate Pb to a greater extent than do the leaves or tubers, which may present a human health risk. Consumption of sweet potato stems should be avoided when consuming sweet potato leaves grown as a vegetable on urban soils with elevated levels of Pb and As.