U.S. Geological Survey, 215 Limekiln Road, New Cumberland, PA 17070, United States.
U.S. Geological Survey, 10 Bearfoot Road, Northboro, MA 01532, United States.
Sci Total Environ. 2021 May 1;767:144691. doi: 10.1016/j.scitotenv.2020.144691. Epub 2020 Dec 26.
Lithium concentrations in untreated groundwater from 1464 public-supply wells and 1676 domestic-supply wells distributed across 33 principal aquifers in the United States were evaluated for spatial variations and possible explanatory factors. Concentrations nationwide ranged from <1 to 396 μg/L (median of 8.1) for public supply wells and <1 to 1700 μg/L (median of 6 μg/L) for domestic supply wells. For context, lithium concentrations were compared to a Health Based Screening Level (HBSL, 10 μg/L) and a drinking-water only threshold (60 μg/L). These thresholds were exceeded in 45% and 9% of samples from public-supply wells and in 37% and 6% from domestic-supply wells, respectively. However, exceedances and median concentrations ranged broadly across geographic regions and principal aquifers. Concentrations were highest in arid regions and older groundwater, particularly in unconsolidated clastic aquifers and sandstones, and lowest in carbonate-rock aquifers, consistent with differences in lithium abundance among major lithologies and rock weathering extent. The median concentration for public-supply wells in the unconsolidated clastic High Plains aquifer (central United States) was 24.6 μg/L; 24% of the wells exceeded the drinking-water only threshold and 86% exceeded the HBSL. Other unconsolidated clastic aquifers in the arid West had exceedance rates comparable to the High Plains aquifer, whereas no public supply wells in the Biscayne aquifer (southern Florida) exceeded either threshold, and the highest concentration in that aquifer was 2.6 μg/L. Multiple lines of evidence indicate natural sources for the lithium concentrations; however, anthropogenic sources may be important in the future because of the rapid increase of lithium battery use and subsequent disposal. Geochemical models demonstrate that extensive evaporation, mineral dissolution, cation exchange, and mixing with geothermal waters or brines may account for the observed lithium and associated constituent concentrations, with the latter two processes as major contributing factors.
对美国 33 个主要含水层中的 1464 口公共供水井和 1676 口家庭供水井的未处理地下水的锂浓度进行了评估，以研究其空间变化和可能的解释因素。全国范围内，公共供水井的锂浓度范围为<1 至 396μg/L（中位数为 8.1μg/L），家庭供水井的锂浓度范围为<1 至 1700μg/L（中位数为 6μg/L）。为了便于比较，将锂浓度与基于健康的筛选水平（HBSL，10μg/L）和仅饮用水阈值（60μg/L）进行了比较。在公共供水井中，有 45%和 9%的样本超过了这些阈值，在家庭供水井中，有 37%和 6%的样本超过了这些阈值。然而，超标和中位数浓度在地理区域和主要含水层之间广泛变化。在干旱地区和较老的地下水中，锂浓度最高，特别是在非固结碎屑含水层和砂岩中，而在碳酸盐岩含水层中最低，这与主要岩性之间的锂丰度差异以及岩石风化程度一致。非固结碎屑高平原含水层（美国中部）公共供水井的中位数浓度为 24.6μg/L；24%的井超过了仅饮用水阈值，86%的井超过了 HBSL。干旱西部的其他非固结碎屑含水层的超标率与高平原含水层相当，而比斯坎含水层（佛罗里达州南部）没有公共供水井超过任何一个阈值，该含水层中锂的最高浓度为 2.6μg/L。多条证据表明，锂浓度的自然来源；然而，由于锂离子电池使用量的快速增加及其随后的处置，人为来源可能在未来变得重要。地球化学模型表明，广泛的蒸发、矿物溶解、阳离子交换以及与地热或卤水的混合可能是造成观测到的锂及其相关成分浓度的原因，后两个过程是主要的影响因素。
