Pan Yunyu, Koopmans Gerwin F, Bonten Luc T C, Song Jing, Luo Yongming, Temminghoff Erwin J M, Comans Rob N J
Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, People's Republic of China.
Department of Soil Quality, Wageningen University, P.O. Box 47, 6700 AA, Wageningen, The Netherlands.
Environ Geochem Health. 2016 Dec;38(6):1355-1372. doi: 10.1007/s10653-016-9803-7. Epub 2016 Jan 30.
Alternating flooding and drainage conditions have a strong influence on redox chemistry and the solubility of trace metals in paddy soils. However, current knowledge of how the effects of water management on trace metal solubility are linked to trace metal uptake by rice plants over time is still limited. Here, a field-contaminated paddy soil was subjected to two flooding and drainage cycles in a pot experiment with two rice plant cultivars, exhibiting either high or low Cd accumulation characteristics. Flooding led to a strong vertical gradient in the redox potential (Eh). The pH and Mn, Fe, and dissolved organic carbon concentrations increased with decreasing Eh and vice versa. During flooding, trace metal solubility decreased markedly, probably due to sulfide mineral precipitation. Despite its low solubility, the Cd content in rice grains exceeded the food quality standards for both cultivars. Trace metal contents in different rice plant tissues (roots, stem, and leaves) increased at a constant rate during the first flooding and drainage cycle but decreased after reaching a maximum during the second cycle. As such, the high temporal variability in trace metal solubility was not reflected in trace metal uptake by rice plants over time. This might be due to the presence of aerobic conditions and a consequent higher trace metal solubility near the root surface, even during flooding. Trace metal solubility in the rhizosphere should be considered when linking water management to trace metal uptake by rice over time.
交替淹水和排水条件对水稻土中的氧化还原化学及微量金属的溶解度有强烈影响。然而，目前关于水分管理对微量金属溶解度的影响如何随时间与水稻植株对微量金属的吸收相关联的认识仍然有限。在此，在盆栽试验中，对一块受污染的田间水稻土进行了两个淹水和排水周期的试验，使用了两个具有高或低镉积累特性的水稻品种。淹水导致氧化还原电位（Eh）出现强烈的垂直梯度。pH值以及锰、铁和溶解有机碳浓度随Eh降低而增加，反之亦然。淹水期间，微量金属溶解度显著降低，这可能是由于硫化物矿物沉淀所致。尽管镉的溶解度较低，但两个品种水稻籽粒中的镉含量均超过了食品质量标准。在第一个淹水和排水周期中，不同水稻植株组织（根、茎和叶）中的微量金属含量以恒定速率增加，但在第二个周期达到最大值后下降。因此，微量金属溶解度随时间的高变异性并未反映在水稻植株随时间对微量金属的吸收上。这可能是由于即使在淹水期间，根际附近存在好氧条件以及随之而来的较高微量金属溶解度。在将水分管理与水稻随时间对微量金属的吸收联系起来时，应考虑根际中的微量金属溶解度。
