Arsenic in the soil–rice system of the Mekong River delta

Arsenic (As) in rice has been known as a worldwide human health threat that results originally from the accumulation of As in soil in many rice cultivation regions. This study aims to evaluate As levels in the soil–rice system in the Mekong River delta (MRD) with special focuses on the geographical distribution and the relation to soil physio-chemical properties. It was found that soil As contents varied from 0.3 to 15.9 mg kg⁻¹ (x˜ = 7.22 ± 0.3 mg kg⁻¹), whereas straw As content was about one order of magnitude lower (x˜ = 0.92 ± 0.1 mg kg⁻¹). The content of As in grain varied from “not detectable” to 1115 µg kg⁻¹ (x˜ = 73 ± 19 µg kg⁻¹). Relatively similar geographical distribution patterns were observed for soil As and straw As, meanwhile grain As did not reveal a clear association with straw As and soil As. The accumulation of As in rice (straw and grain) were likely affected by various factors, but the mutual effects of soil As pool and soil properties were the most obvious. The East coastal area of the MRD has been identified as a vulnerable area to As threat. This finding suggests that in addition to the action plans to preserve coastal paddy soils from the threats of sea level rise and salt intrusion, contamination of As should also be considered.

稻米中的砷（Arsenic, As）已被证实为全球性人类健康威胁，其主要诱因是多数水稻种植区土壤中砷的累积。本研究旨在评估湄公河三角洲（Mekong River Delta, MRD）土壤-水稻体系中的砷含量，重点关注其空间分布特征及其与土壤理化性质的关联。研究结果显示，土壤砷含量介于0.3至15.9 mg·kg⁻¹之间，平均值为7.22 ± 0.3 mg·kg⁻¹；稻秆砷含量则低约一个数量级，平均值为0.92 ± 0.1 mg·kg⁻¹。稻米籽粒中的砷含量范围为未检出至1115 μg·kg⁻¹，平均值为73 ± 19 μg·kg⁻¹。土壤砷与稻秆砷呈现出较为相似的空间分布格局，但稻米籽粒砷含量与稻秆砷、土壤砷均未表现出显著相关性。水稻（稻秆与籽粒）中砷的累积过程可能受多种因素影响，其中土壤砷库与土壤性质的交互作用最为显著。湄公河三角洲东部沿海区域被认定为砷污染威胁的高风险敏感区域。该研究结果提示，除了制定保护沿海稻田土壤免受海平面上升与盐渍入侵威胁的行动计划外，还应将砷污染防控纳入统筹考量范畴。