Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA.
Department of Statistics, Virginia Tech, Blacksburg, VA 24061, USA.
Int J Environ Res Public Health. 2018 Apr 18;15(4):787. doi: 10.3390/ijerph15040787.
We investigated if geologic factors are linked to elevated arsenic (As) concentrations above 5 μg/L in well water in the state of Virginia, USA. Using geologic unit data mapped within GIS and two datasets of measured As concentrations in well water (one from public wells, the other from private wells), we evaluated occurrences of elevated As (above 5 μg/L) based on geologic unit. We also constructed a logistic regression model to examine statistical relationships between elevated As and geologic units. Two geologic units, including Triassic-aged sedimentary rocks and Triassic-Jurassic intrusives of the Culpeper Basin in north-central Virginia, had higher occurrences of elevated As in well water than other geologic units in Virginia. Model results support these patterns, showing a higher probability for As occurrence above 5 μg/L in well water in these two units. Due to the lack of observations (<5%) having elevated As concentrations in our data set, our model cannot be used to predict As concentrations in other parts of the state. However, our results are useful for identifying areas of Virginia, defined by underlying geology, that are more likely to have elevated As concentrations in well water. Due to the ease of obtaining publicly available data and the accessibility of GIS, this study approach can be applied to other areas with existing datasets of As concentrations in well water and accessible data on geology.
我们研究了美国弗吉尼亚州的地质因素是否与井水砷浓度（As）超过 5μg/L 有关。我们利用 GIS 中绘制的地质单元数据和两个井水砷浓度测量数据集（一个来自公共水井，另一个来自私人水井），根据地质单元评估了高砷（超过 5μg/L）的发生情况。我们还构建了一个逻辑回归模型来检验砷浓度升高与地质单元之间的统计关系。弗吉尼亚州有两个地质单元，包括中北部弗吉尼亚州的三叠纪沉积岩和 Culpeper 盆地的三叠纪-侏罗纪侵入岩，其井水砷浓度升高的发生率高于弗吉尼亚州的其他地质单元。模型结果支持了这些模式，表明在这两个单元中，井水砷浓度升高的可能性更高。由于我们的数据集中缺乏（<5%）观察到砷浓度升高的情况，因此我们的模型不能用于预测该州其他地区的砷浓度。然而，我们的研究结果对于识别弗吉尼亚州的特定地区（定义为潜在的地质条件）具有重要意义，这些地区的井水砷浓度更有可能升高。由于易于获取公开可用的数据以及 GIS 的可访问性，这种研究方法可以应用于其他具有井水砷浓度现有数据集和可访问地质数据的地区。
