Linking groundwater arsenic to subsidence and aquifer properties


Arsenic in groundwater is a major health concern globally. While arsenic occurs naturally as a function of geologic sources and the geochemical condition of the aquifer, it can also be increased due to human activity. Arsenic often occurs at much higher concentrations in clay-rich portions of aquifers due to the higher reactivity and lower oxidation state of clays. When over-pumping aquifers occurs, it creates strong vertical gradients that draw more water out of clays. This can both cause subsidence and bring arsenic-rich water into the aquifer. This has been explored in Vietnam (Erban et al., 2013) and California (Smith et al., 2018). Others have proposed drawdown can lead to altered flow-paths and increased arsenic (Knappett et al., 2016). 

In this study, we are exploring natural and anthropogenic contributions to high arsenic concentrations in the aquifers of the San Luis Valley, Colorado. In this region, over 10% of all wells have arsenic concentrations above the WHO standard of 10 ppb, and the majority of drinking water wells are private, meaning they are not monitored. This is an interdisciplinary study that both explores the geospatial variability and drivers of arsenic, as well as its impact on health outcomes within the community.



Study areas


Figure Caption:

The figure to the right is taken from Smith  et al. (2018) and shows that regions with higher subsidence also have higher arsenic concentrations in the San Joaquin Valley of California.


Smith, R.G., R. Knight, S. Fendorf, 2018, Over-Pumping Leads to California Groundwater Arsenic Threat. Nature Communications. [link]