School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV, USA,
Environ Monit Assess. 2014 May;186(5):3181-97. doi: 10.1007/s10661-013-3609-1. Epub 2014 Jan 11.
A field study was conducted on a small urban watershed (residential and golf course dominated) in southern Nevada to assess the concentration and speciation of selenium (Se) in a series of drain lines and monitoring wells and to quantify the mass discharge of Se from the drain system. Water samples were collected on a monthly basis and analyzed for total Se, selenate (SeO4 (=)) and selenite (SeO3 (=)). In addition, where possible, flow was assessed as was, temperature, redox potential, pH, dissolved oxygen (DO) along with all major cations and anions. The data were then modeled with PhreeqC to identify selenium speciation. Results revealed a SeO4 (=) dominated system with SeO4 (=) concentrations ranging from 13 to 62 ppb. In the monitoring wells, 66 % of the variation in the total Se concentration could be described based on depth to groundwater, temperature and sulfate concentrations (P < 0.001). In particular, higher total Se concentrations were predicted for shallower depth to groundwater, suggesting the solubilization of Se evapo-concentrates near the surface could be reduced by lowering water tables. The highest of all correlations was found between SeO4 (=) concentrations (↑) and the sodium (↑) and DO (↑) concentrations in the monitoring wells (R (2) = 0.77, P < 0.001). An excellent curvilinear relationship was found between total Se and the electrical conductivity in the water (R (2) = 0.73, P < 0.001). Based on the Se data and time line identified in this study, high concentrations of Se could be expected to drain from this area for many years to come, with salinity acting as a good proxy for Se concentration. In the drain lines, Se concentrations were found to be invariant to flow (P > 0.05). Flow discharge from the main drain system to the Las Vegas Wash was estimated at 559 acre feet during the 1 year study period. This flow was estimated to carry 4,203 Mg of salts 6.71 Mg of nitrate-N and 27.1 kg of total Se.
在内华达州南部的一个小型城市流域（以住宅和高尔夫球场为主）进行了实地研究，以评估一系列排水管道和监测井中硒（Se）的浓度和形态，并量化从排水系统排出的 Se 质量。每月采集水样并分析总硒、硒酸盐（SeO4 (=)）和亚硒酸盐（SeO3 (=)）。此外，在可能的情况下，还评估了流量以及温度、氧化还原电位、pH 值、溶解氧（DO）以及所有主要阳离子和阴离子。然后使用 PhreeqC 对数据进行建模以确定硒的形态。结果表明，系统中以硒酸盐（SeO4 (=)）为主，硒酸盐（SeO4 (=)）浓度范围为 13 至 62 ppb。在监测井中，总 Se 浓度的 66%可根据地下水位深度、温度和硫酸盐浓度来描述（P < 0.001）。特别是，预测地下水位较浅的地方总 Se 浓度较高，表明通过降低地下水位，可以减少靠近地表的硒蒸发浓缩物的溶解。在监测井中，发现 SeO4 (=)浓度与钠离子（↑）和 DO（↑）浓度之间的相关性最高（R (2) = 0.77，P < 0.001）。在水中总 Se 与电导率之间发现了极好的曲线关系（R (2) = 0.73，P < 0.001）。根据本研究中确定的 Se 数据和时间线，预计在未来许多年，该地区将有大量高浓度的 Se 流出，而盐分则是 Se 浓度的良好替代物。在排水管道中，发现 Se 浓度与流量无关（P > 0.05）。在 1 年的研究期间，从主要排水系统到拉斯维加斯溪的流量估计为 559 英亩英尺。据估计，该流量携带了 4203 Mg 盐、6.71 Mg 硝酸盐-N 和 27.1 kg 总 Se。
