Hu Xiaoxi, Wang Feiyue, Hanson Mark L
Department of Environment and Geography, University of Manitoba, Winnipeg, Canada.
Sci Total Environ. 2009 Nov 1;407(22):5869-76. doi: 10.1016/j.scitotenv.2009.08.001. Epub 2009 Sep 3.
Similar to the San Joaquin Valley of California, the Canadian prairies are underlain with seleniferous shale and have recently witnessed a significant expansion in irrigated agriculture. The irrigated acreage in the prairies is expected to further increase due to global warming and changes in human use patterns. This raises concerns over potential selenium (Se) contamination in prairie surface waters and risk of adverse biological effects. To test the potential for elevated Se in the prairies, Se concentrations and speciation were examined in surface water, sediments, and sediment porewater in three water bodies in southern Manitoba, Canada, along a north-south transect with a gradient of irrigation and agricultural activities. A selenite addition experiment was also performed in mesocosms in a prairie wetland to assess the risk of increasing Se loading to the prairie waters. Overall, our results indicate that Se concentrations in the prairie waters of southern Manitoba are presently low except during the snowmelt season, that Se speciation is dominated by selenate which is of lower toxicity than selenite, and that if additional selenite is discharged into the prairie waters, it will be quickly removed from the surface water to the sediment. The low Se risk in the Canadian prairies is attributed to high soil drainability and relatively small scale of irrigation at present. The Se problem as being experienced in central California is thus unlikely to occur in surface waters of the Canadian prairies, although Se contamination in ground water is possible should the irrigated acreage continue to increase.
与加利福尼亚州的圣华金河谷类似，加拿大大草原的地下有富硒页岩，并且最近灌溉农业出现了显著扩张。由于全球变暖和人类使用模式的变化，大草原的灌溉面积预计将进一步增加。这引发了对大草原地表水潜在硒污染以及生物不良反应风险的担忧。为了测试大草原中硒含量升高的可能性，沿着一条具有灌溉和农业活动梯度的南北样带，对加拿大曼尼托巴省南部三个水体的地表水、沉积物和沉积物孔隙水中的硒浓度及形态进行了检测。还在一个大草原湿地的中宇宙中进行了亚硒酸盐添加实验，以评估向大草原水体增加硒负荷的风险。总体而言，我们的结果表明，除融雪季节外，曼尼托巴省南部大草原水体中的硒浓度目前较低，硒形态以毒性低于亚硒酸盐的硒酸盐为主，并且如果向大草原水体中排放额外的亚硒酸盐，它将很快从地表水转移到沉积物中。加拿大大草原目前较低的硒风险归因于土壤排水性高以及灌溉规模相对较小。因此，尽管如果灌溉面积持续增加，地下水可能会受到硒污染，但加利福尼亚州中部所经历的硒问题不太可能在加拿大大草原的地表水中出现。
