美国犹他州中部Green River流域农业区硒的淋出速度和形态(英文)

Leaching rates and forms of selenium in cores from an agricultural area in middle Green River basin,UTAH,USA

尽管硒（Se）是一种重要的生命元素，但是即使浓度很低，也有可能会造成危害。在美国西部，包括犹他州中部Green River流域斯图尔特湖水乌管理区，大面积的农业排水区中都存在硒。为了对该场地进行地球化学研究和进行修复，取未受扰动的岩芯分析了硒的形态、浓度和迁移。用酸消解进行前处理对土壤和曼柯斯页岩风化壳进行了分析，结果表明，硒的最高浓度为3ppm，采用连续萃取法的分析结果表明，有19％～79％的硒是以有机物形式存在的，有17％～67％的硒是以元素形式存在的。柱实验研究结果表明，硒可以从深部土壤迅速淋出，可溶性硒的质量分数很高，达到了292×10^-9。表层土壤中硒的淋出速度最初很慢，但是非常稳定，最终淋出速度会超过深部土壤。当对岩心通过放射灭菌后，表层土壤和深部土壤的淋出速度都会加快。计算结果表明，在修复富含硒的土壤时，所需的水量很大，每kg土壤需要约500L的水量。

Selenium （Se） is a biologically essential element, but can become a potent toxicant even at low concentrations. Toxic concentrations of Se are present in irrigation drainage water from large areas in western USA, including Stewart Lake Waterfowl Management Area located in the middle Green River basin, Utah. As part of a major investigation of Se geochemistry and remediation for this site, undisturbed cores were collected to determine the form, concentration, and mobility of Se. Wet digestion analysis of soil and weathered Mancos Shale samples gave high total Se concentrations （up to 3 ppm） and sequential extractions showed that Se was present mainly in association with organic matter （19%-79%） and in the elemental form （17%-67%）. Column experiments indicated that Se could be leached rapidly from the deeper soil, where soluble Se is high （up to 292 ppb）. The Se leaching rate for the surface soil was initially lower, but was more stable and eventually exceeded that of the deeper soil. The leaching rate of both surface and deeper soils increased when the cores were sterilized by irradiation. Calculations indicate that the quantity of water required to remediate these Se-rich soils by leaching would be large （- 500 L/kg of soil）.