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首页> 外文期刊>Environmental Science & Technology >Spatial Distribution and Temporal Variability of Arsenic in Irrigated Rice Fields in Bangladesh. 1. Irrigation Water
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Spatial Distribution and Temporal Variability of Arsenic in Irrigated Rice Fields in Bangladesh. 1. Irrigation Water

机译：孟加拉国灌溉稻田中砷的时空分布和时空变异1.灌溉水

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Around 38% of the area of Bangladesh is irrigated with groundwater to grow dry season crops, most importantly boro rice. Due to high As concentrations in many groundwaters, over 1000 tons of As are thus transferred to arable soils each year, creating a potential risk for future food production. We studied the reactions and changing speciation of As, Fe, P, and other elements in initially anoxic water during and after irrigation and the resulting spatial distribution of As input to paddy soils near Sreenagar (Munshiganj), 30 km south of Dhaka, in January and April 2005 and February 2006. The irrigation water had a constant concentration of 397 ± 7 μg L~(-1) As (～84% As~Ⅲ), 11 ± 0.1 mg L~(-1) Fe, and 2 ± 0.1 mg L~(-1) P. During the fast flow along the longest irrigation channel (152 m) As, Fe, and P speciation changed, but total concentrations did not decrease significantly, indicating that As input to fields was independent of the length of the irrigation channels. In contrast, during slow water flow across the fields, As, Fe, and P concentrations decreased strongly with increasing distance from the water inlet, due to formation and settling of As- and P-bearing Fe aggregates and by adsorption to soil minerals. Total As concentrations in field water were ～3 times higher close to the inlet than in the opposite field corner shortly after irrigation, and decreased to below 35 μg L~(-1) over the next 72 h. The laterally heterogeneous transfer of As, Fe, and P from irrigation waterto soil has important consequencesfortheir distribution in irrigated fields and needs to be considered in sampling and in assessing the dynamics and mass balances of As fluxes among irrigation water, soil, and floodwater.
机译：孟加拉国约38％的土地被灌溉以种植旱季作物，最重要的是硼米。由于许多地下水中砷的浓度很高，因此每年将超过1000吨的砷转移到可耕土壤中，为将来的粮食生产带来潜在的风险。我们研究了灌溉期间和灌溉后初始缺氧水中As，Fe，P和其他元素的反应和形态变化，以及1月在达卡以南30公里处Sreenagar（Munshiganj）附近的水稻土中As输入的空间分布情况。以及2005年4月和2006年2月。灌溉水的恒定浓度为397±7μgL〜（-1）As（〜84％As〜Ⅲ），11±0.1 mg L〜（-1）Fe和2± 0.1 mg L〜（-1）P。在沿最长灌溉通道（152 m）的快速流动过程中，As，Fe和P的形态发生了变化，但总浓度并未显着降低，表明向田间输入的As不受灌溉渠道的长度。相反，在穿过田间的缓慢水流中，由于含砷和磷的Fe聚集物的形成和沉降以及对土壤矿物质的吸附，随着距水入口距离的增加，砷，铁和磷的浓度会急剧下降。灌溉后不久，靠近进水口的田间水中总As浓度约为对面角落的3倍，然后在接下来的72小时内降至35μgL〜（-1）以下。砷，铁和磷从灌溉水到土壤的横向异质转移对其在灌溉田中的分布具有重要影响，在采样以及评估灌溉水，土壤和洪水中砷通量的动力学和质量平衡时，需要考虑这些因素。

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