Effect of irrigation water containing arsenic on elemental composition of bean and lettuce plants cultivated in calcareous sandy soil

Background:The uptake of arsenic by vegetables from soil irrigated with arsenic enriched groundwater poses a major health hazard.The edible portion of these vegetables transfer arsenic to the human beings.The uptake of arsenic was studied in bean(Phaseolus vulgaris L.)and lettuce(Lactuca sativa L.)in a controlled greenhouse pot culture with calcareous sandy soil as substrate.The plants were irrigated with water containing sodium arsenate at concentrations 0.1,0.25 and 0.5 mg L^(-1).The total arsenic concentration of the different plants parts was determined by ICP-MS,following microwave-assisted acid digestion.The change in plant biomass production and essential macroelements(Mg,P,K)and microelements concentration(Fe,Mn,Cu,Zn)was also studied.Results:The As concentration in the bean was in the order:root>stem>leaf>bean fruit and in lettuce:root>leaves.At the highest dose(0.5 mg L^(-1))the As concentration in the bean fruit and lettuce leaves was 22.1μg kg^(-1)and 1207.5μg kg^(-1)DW,respectively.Increasing As concentration in the irrigation water resulted in decreased edible biomass production in bean,while in lettuce the edible biomass production increased.Neither plant exhibited any visible toxicity symptoms.No significant change was observed in the macro and microelements concentration.The total and the water-soluble arsenic in soil amounted to 3.5 mg kg^(−1)and 0.023 mg kg^(−1),respectively.The transfer factor was found to increase with increase in the As treatment applied.The transfer factor range for bean from root to fruit was 0.003–0.005,and for lettuce from root to leaves was 0.14–0.24.Conclusion:Considering the FAO-WHO recommended maximum tolerable daily intake(MTDI)limit of 2.1μg kg^(-1)body weight,and the biomass production,both plants should not be cultivated at As treatment level higher than 0.1 mg L^(-1).