School of Civil and Environmental Engineering, Cornell University, Ithaca, NY, 14853, USA.
Environmental Microbiology Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne, CH, 1015, Switzerland; Institute of Earth Surface Dynamics, Faculty of Geosciences and Environment, University of Lausanne, 1015 Lausanne, Switzerland.
Chemosphere. 2021 Feb;265:129092. doi: 10.1016/j.chemosphere.2020.129092. Epub 2020 Nov 27.
There is growing concern regarding human dietary exposure to arsenic (As) via consumption of rice. The concentration and speciation of As in rice are highly variable, and models describing rice As speciation as a function of environmental covariates remain elusive. We conducted a survey of paddy rice and soil in the Mekong Delta with the objective of linking patterns in rice As content to soil chemical variables or hydrogeological parameters. The sum of As species (ΣAs) in husked rice averaged 243 μg/kg and the average inorganic As (iAs) content was 84%. There was no relationship found between rice As concentration or speciation and As levels in soil. However, mean As concentrations in groundwater near rice sampling locations were strongly correlated with grain ΣAs and iAs over a large part of the study region, despite the fact that groundwater is not commonly used for rice paddy irrigation in this region. We hypothesize that surficial sediments with high concentrations of soluble and plant-available As also serve as sources of arsenic to downgradient shallow aquifers, explaining the observed associations between rice and groundwater As. This study suggests that shallow groundwater As concentrations may serve as a useful indicator for locations at risk of elevated iAs concentrations in rice.
人们越来越关注通过食用大米摄入砷（As）对人体的影响。大米中砷的浓度和形态差异很大，描述其形态与环境协变量关系的模型仍难以建立。本研究对湄公河三角洲的稻田和土壤进行了调查，旨在将大米中砷含量的变化模式与土壤化学变量或水文地质参数联系起来。去壳大米中砷的总量（ΣAs）平均为 243μg/kg，无机砷（iAs）的平均含量为 84%。然而，在研究区域的很大一部分地区，水稻采样点附近地下水的砷浓度与稻谷ΣAs 和 iAs 之间存在很强的相关性，尽管在该地区，地下水通常不用于稻田灌溉，但并未发现大米中砷浓度或形态与土壤砷含量之间存在关系。我们假设，表层沉积物中高浓度的可溶性和植物可利用的砷也可能成为下游浅层含水层砷的来源，这解释了观测到的水稻与地下水砷之间的关联。本研究表明，浅层地下水中的砷浓度可能是砷浓度升高的高风险地区的一个有用指标。
