The many faces of Manganese: An under-recognized contaminant & driver of biogeochemical cycles
About the talk:
Manganese contamination of groundwater is a global phenomenon that has been reported in more than 74 countries with an increasing number of studies being published describing its adverse neurotoxic effects when consumed. Even so, the World Health Organization has recently removed manganese from the Guideline for Drinking-water Quality database and therefore no longer provides a suggested limit. Similarly, the USEPA sets a non-mandatory water quality standard for manganese presence in drinking water and therefore treatment is not enforced. In this talk, I will discuss how the biogeochemical processes that enhance arsenic contamination of groundwater overlap with conditions that also increase manganese concentrations in aquifers. Our findings show that seasonal fluctuations in groundwater recharge and discharge can lead to dramatic swings in groundwater concentrations, while manganese concentrations appear to be constantly high and unaltered by shifts in recharge. We also demonstrate that arsenic and manganese contamination are depth stratified using a global dataset, which may provide an opportunity to separate the uses of water produced by deep versus relatively shallow wells. Overall, our findings may be showing that due to the global emphasis of regulations on arsenic, drinking water sources are being mislabeled as safe when manganese contamination is overlooked in these same regions.
Sam is an assistant professor of soil biogeochemistry in the Department of Environmental Sciences at the University of California, Riverside. Her research group examines how human activities including agricultural practices will induce changes in soil carbon dynamics and drinking water quality. Her group is particularly interested in how biologically-driven and chemically-driven (abiotic) redox processes contribute to the mobilization of naturally-occurring metals in soils and sediments that ultimately pollute aquifers. She is a recent recipient of a Fulbright Award to investigate the short and long term metals release from mine-tailings, including the accumulation of manganese in fish and wildlife, in a collaborative project with researchers at the University of São Paulo, Brazil.