Department of Environmental, Water Resources and Coastal Engineering, Military Institute of Science and Technology (MIST), Mirpur Cantonment, Dhaka, 1216, Bangladesh.
Department of Civil Engineering, College of Engineering, Qassim University, Buraydah, 51452, Saudi Arabia.
J Environ Manage. 2023 Oct 1;343:118204. doi: 10.1016/j.jenvman.2023.118204. Epub 2023 May 23.
Irrigation water in rice cultivation significantly affects the arsenic (As) mobilization in the paddy field soil. This research assessed the effect of rainwater (RW) and groundwater (GW) on the dissolution dynamics of arsenic (As) in paddy field soil. Up-flow column flooding experiments were conducted continuously for 80 d with simulated RW and GW to evaluate As dissolution phenomena in actual field conditions. Arsenic dissolution from the soil was lower in GW (309 μg/kg) irrigation than in RW flooding conditions (1086 μg/kg). The redox potential (Eh) of the soil pore water decreased, and pH increased over-irrigation time in both flooding conditions. The dissolution of arsenic (As) and iron (Fe) in the soil pore increased, while the dissolution of manganese (Mn) decreased over flooding time. The release of As in the soil pore water was attributed to the dissolution of Fe-As and Mn-As minerals and microbial reduction of As. Fe-As dissolution ratios in the soil pore water were relatively low and estimated as 0.68 mol/mol and 4.9 mol/mol for RW and GW, respectively. The dissolution of As and Mn dominated in the initial phase (0-40 d) of flooding, while the dissolution of As and Fe dominated in the second phase (40-80 d). The release of As was much lower in GW flooding than in RW flooding conditions. The Presence of Ca, Mg, and Mn in the GW facilitated the reduction of As dissolution by precipitating Ca-As and Mg-As and the oxidizing dissolved Mn in the soil pore water. The findings of this study provide valuable insights into the mechanisms of As release during monsoon flooding and groundwater flooding to assess the potential risks of As contamination in rice grown in paddy field soils.
在水稻种植中，灌溉水会显著影响稻田土壤中砷的迁移。本研究评估了雨水（RW）和地下水（GW）对稻田土壤中砷溶解动力学的影响。通过连续 80 天的上向流柱浸出实验，用模拟的 RW 和 GW 评估了实际田间条件下砷溶解现象。与 RW 淹没条件（1086μg/kg）相比，GW 灌溉条件下土壤中砷的溶解量（309μg/kg）较低。在两种淹没条件下，土壤孔隙水的氧化还原电位（Eh）随灌溉时间的延长而降低，pH 值升高。随着淹没时间的延长，土壤孔隙中砷（As）和铁（Fe）的溶解增加，而锰（Mn）的溶解减少。土壤孔隙水中 As 的释放归因于 Fe-As 和 Mn-As 矿物的溶解以及 As 的微生物还原。土壤孔隙水中 Fe-As 的溶解比例相对较低，RW 和 GW 分别估计为 0.68mol/mol 和 4.9mol/mol。在淹没的初始阶段（0-40 天），As 和 Mn 的溶解占主导地位，而在第二阶段（40-80 天），As 和 Fe 的溶解占主导地位。GW 淹没条件下的 As 释放量明显低于 RW 淹没条件。GW 中 Ca、Mg 和 Mn 的存在促进了 Ca-As 和 Mg-As 的沉淀以及土壤孔隙水中溶解 Mn 的氧化，从而减少了 As 的溶解。本研究的结果为季风淹没和地下水淹没过程中 As 释放机制提供了有价值的见解，有助于评估稻田土壤中砷污染的潜在风险。
