| Abstract
| - The use of arsenic (As) contaminated groundwater forirrigation of crops has resulted in elevated concentrationsof arsenic in agricultural soils in Bangladesh, WestBengal (India), and elsewhere. Paddy rice (Oryza sativaL.) is the main agricultural crop grown in the arsenic-affectedareas of Bangladesh. There is, therefore, concernregarding accumulation of arsenic in rice grown thosesoils. A greenhouse study was conducted to examine theeffects of arsenic-contaminated irrigation water on thegrowth of rice and uptake and speciation of arsenic.Treatments of the greenhouse experiment consisted oftwo phosphate doses and seven different arsenateconcentrations ranging from 0 to 8 mg of As L-1 appliedregularly throughout the 170=day post-transplantationgrowing period until plants were ready for harvesting.Increasing the concentration of arsenate in irrigation watersignificantly decreased plant height, grain yield, thenumber of filled grains, grain weight, and root biomass,while the arsenic concentrations in root, straw, and rice huskincreased significantly. Concentrations of arsenic in ricegrain did not exceed the food hygiene concentration limit (1.0mg of As kg-1 dry weight). The concentrations of arsenicin rice straw (up to 91.8 mg kg-1 for the highest Astreatment) were of the same order of magnitude as rootarsenic concentrations (up to 107.5 mg kg-1), suggesting thatarsenic can be readily translocated to the shoot. Whilenot covered by food hygiene regulations, rice straw is usedas cattle feed in many countries including Bangladesh.The high arsenic concentrations may have the potential foradverse health effects on the cattle and an increase ofarsenic exposure in humans via the plant−animal−humanpathway. Arsenic concentrations in rice plant partsexcept husk were not affected by application of phosphate.As the concentration of arsenic in the rice grain waslow, arsenic speciation was performed only on rice strawto predict the risk associated with feeding contaminatedstraw to the cattle. Speciation of arsenic in tissues (usingHPLC−ICP-MS) revealed that the predominant speciespresent in straw was arsenate followed by arsenite anddimethylarsinic acid (DMAA). As DMAA is only present atlow concentrations, it is unlikely this will greatly alterthe toxicity of arsenic present in rice.
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