Dittmar Jessica, Voegelin Andreas, Roberts Linda C, Hug Stephan J, Saha Ganesh C, Ali M Ashraf, Badruzzaman A Borhan M, Kretzschmar Ruben
Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Sciences, ETH Zurich, CHN, CH-8092 Zurich, Switzerland.
Environ Sci Technol. 2007 Sep 1;41(17):5967-72. doi: 10.1021/es0702972.
Arsenic-rich groundwater from shallow tube wells is widely used for the irrigation of boro rice in Bangladesh and West Bengal. In the long term this may lead to the accumulation of As in paddy soils and potentially have adverse effects on rice yield and quality. In the companion article in this issue, we have shown that As input into paddy fields with irrigation water is laterally heterogeneous. To assess the potential for As accumulation in soil, we investigated the lateral and vertical distribution of As in rice field soils near Sreenagar (Munshiganj, Bangladesh) and its changes over a 1 year cycle of irrigation and monsoon flooding. At the study site, 18 paddy fields are irrigated with water from a shallow tube well containing 397 +/- 7 microg L(-1) As. The analysis of soil samples collected before irrigation in December 2004 showed that soil As concentrations in paddy fields did not depend on the length of the irrigation channel between well and field inlet. Within individual fields, however, soil As contents decreased with increasing distance to the water inlet, leading to highly variable topsoil As contents (11-35 mg kg(-1), 0-10 cm). Soil As contents after irrigation (May 2005) showed that most As input occurred close to the water inlet and that most As was retained in the top few centimeters of soil. After monsoon flooding (December 2005), topsoil As contents were again close to levels measured before irrigation. Thus, As input during irrigation was at least partly counteracted by As mobilization during monsoon flooding. However, the persisting lateral As distribution suggests net arsenic accumulation over the past 15 years. More pronounced As accumulation may occur in regions with several rice crops per year, less intense monsoon flooding, or different irrigation schemes. The high lateral and vertical heterogeneity of soil As contents must be taken into account in future studies related to As accumulation in paddy soils and potential As transfer into rice.
来自浅管井的富砷地下水在孟加拉国和西孟加拉邦被广泛用于灌溉夏播水稻。从长远来看，这可能导致稻田土壤中砷的积累，并可能对水稻产量和品质产生不利影响。在本期的相关文章中，我们已经表明，灌溉水带入稻田的砷在横向是不均匀的。为了评估土壤中砷积累的可能性，我们调查了斯利那加（孟加拉国蒙希甘杰）附近稻田土壤中砷的横向和垂直分布及其在一年灌溉和季风洪水周期中的变化。在研究地点，18块稻田用一口含砷量为397±7微克/升的浅管井中的水进行灌溉。对2004年12月灌溉前采集的土壤样本进行分析表明，稻田土壤中的砷浓度并不取决于井与田间进水口之间灌溉渠道的长度。然而，在单个田块内，土壤砷含量随着距进水口距离的增加而降低，导致表层土壤砷含量变化很大（11 - 35毫克/千克，0 - 10厘米）。灌溉后（2005年5月）的土壤砷含量表明，大部分砷输入发生在靠近进水口的地方，并且大部分砷保留在土壤表层的几厘米内。季风洪水过后（2005年12月），表层土壤砷含量再次接近灌溉前测量的水平。因此，灌溉期间的砷输入至少部分被季风洪水期间的砷迁移所抵消。然而，持续的横向砷分布表明在过去15年中存在砷的净积累。在每年种植几季水稻、季风洪水强度较小或灌溉方案不同的地区，可能会发生更明显的砷积累。在未来与稻田土壤中砷积累以及砷向水稻中潜在转移相关的研究中，必须考虑土壤砷含量在横向和垂直方向上的高度不均匀性。
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