INCREASED RISK TO HUMAN HEALTH FROM MOBILIZED TRACE METALS IN GROUNDWATER ISLINKED TO RISING SEA LEVEL, INCREASED PRECIPITATION, AND HUMAN IMPOUNDMENTS (Invited Presentation)

Research by Eric Grimm and colleagues on sediments from Lake Tulane, Florida led to unexpected insights about how climate change and rising sea level are likely to endanger human health in coastal populations globally.

Rising sea level, an important consequence of global warming, results from thermal expansion of ocean water, eustatic processes (melting of glaciers), and regional isostasy. The changes vary from place to place around the globe and are difficult to predict. Nevertheless, rising sea level can have serious outcomes including interactions of salt water with coastal groundwater through salinization and raising of groundwater tables. Increased precipitation and impoundments also influence groundwater tables.

We identify an unanticipated outcome of rising sea level and rising groundwater tables that may have large implications for human health. This threat involves mobilization of trace metals – e.g., As, Cd, Mn, and Hg – as rising groundwater levels lead to a more reducing environment in overlying soils. The metal mobilization results primarily from dissolution of secondary Fe oxyhydroxide in soils and release of adsorbed metals, as soils transition from trace-metal sinks to sources. We document and explain the mechanisms at several different temporal and spatial scales. These include: (1) sea-level rise at the end of the last glacial maximum; (2) flooding of regional soils by impoundments; and (3) altered speciation and solubility of redox-sensitive species.

The compounding influences of sea level rise and increased precipitation will likely lead to mobilization of health-threatening trace metals in coastal aquifers. As coastal regions are home to nearly 40% of the world’s population, identification of regions with elevated health risk will aid vulnerability assessment and planning for climate adaptation. To this end, we present a preliminary analysis using spatially-restricted data on population distribution, weather and climate change, geology, soils, and groundwater hydrology.