title: Arsenic accumulation and metabolism in rice (Oryza sativa L.).
abstract: The use of arsenic (As) contaminated groundwater for irrigation of crops has resulted in elevated concentrations of arsenic in agricultural soils in Bangladesh, West Bengal (India), and elsewhere. Paddy rice (Oryza sativa L.) is the main agricultural crop grown in the arsenic-affected areas of Bangladesh. There is, therefore, concern regarding accumulation of arsenic in rice grown those soils. A greenhouse study was conducted to examine the effects of arsenic-contaminated irrigation water on the growth of rice and uptake and speciation of arsenic. Treatments of the greenhouse experiment consisted of two phosphate doses and seven different arsenate concentrations ranging from 0 to 8 mg of As L(-1) applied regularly throughout the 170-day post-transplantation growing period until plants were ready for harvesting. Increasing the concentration of arsenate in irrigation water significantly decreased plant height, grain yield, the number of filled grains, grain weight, and root biomass, while the arsenic concentrations in root, straw, and rice husk increased significantly. Concentrations of arsenic in rice grain did not exceed the food hygiene concentration limit (1.0 mg of As kg(-1) dry weight). The concentrations of arsenic in rice straw (up to 91.8 mg kg(-1) for the highest As treatment) were of the same order of magnitude as root arsenic concentrations (up to 107.5 mg kg(-1)), suggesting that arsenic can be readily translocated to the shoot. While not covered by food hygiene regulations, rice straw is used as cattle feed in many countries including Bangladesh. The high arsenic concentrations may have the potential for adverse health effects on the cattle and an increase of arsenic exposure in humans via the plant-animal-human pathway. Arsenic concentrations in rice plant parts except husk were not affected by application of phosphate. As the concentration of arsenic in the rice grain was low, arsenic speciation was performed only on rice straw to predict the risk associated with feeding contaminated straw to the cattle. Speciation of arsenic in tissues (using HPLC-ICP-MS) revealed that the predominant species present in straw was arsenate followed by arsenite and dimethylarsinic acid (DMAA). As DMAA is only present at low concentrations, it is unlikely this will greatly alter the toxicity of arsenic present in rice.
authors.affiliation: Department of Plant and Soil Science, University of Aberdeen, United Kingdom. m.j.abedin@abdn.ac.uk
authors.forename: Md Joinal
authors.initials: MJ
authors.lastname: Abedin
authors.forename: Malcolm S
authors.initials: MS
authors.lastname: Cresser
authors.forename: Andy A
authors.initials: AA
authors.lastname: Meharg
authors.forename: Jorg
authors.initials: J
authors.lastname: Feldmann
authors.forename: Janet
authors.initials: J
authors.lastname: Cotter-Howells
mesh_terms: D001151:Arsenic / Q000378:metabolism / Q000493:pharmacokinetics*; D018533:Biomass; D004784:Environmental Monitoring; D005506:Food Contamination; D012275:Oryza / Q000502:physiology*; D018517:Plant Roots / Q000737:chemistry / Q000502:physiology; D012989:Soil Pollutants / Q000378:metabolism / Q000493:pharmacokinetics*; D014018:Tissue Distribution; D014873:Water Pollutants / Q000378:metabolism / Q000493:pharmacokinetics*; D014881:Water Supply
chemical_list: D012989:Soil Pollutants; D014873:Water Pollutants; D001151:Arsenic