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Bureau Seminar, October 23, 2009

Arsenic in near-surface groundwater: patterns at petroleum-affected sites

Franz K. Hiebert, Environmental Resources Management, Inc. (ERM)

Link for streaming video: available 10.23.09 at 8:25am CST

In January, 2006 the United States Environmental Protection Agency (USEPA) lowered the maximum contaminant level (MCL) for dissolved arsenic in groundwater from 0.050 mg/L to 0.010 mg/L heightening public and regulatory awareness of dissolved arsenic in groundwater. Arsenic, both naturally-occurring and of anthropogenic source, may be mobilized into shallow groundwater by inputs of biodegradable organic carbon, including petroleum hydrocarbons. Hydrocarbon impact of shallow aquifers is a common occurrence and resulting effects are well characterized. Spatial patterns of arsenic distribution are linked to geochemical zones that develop as the result of biodegradation of petroleum in near-surface groundwater.

The purpose of this work is to develop a conceptual model of arsenic occurrence at petroleum-impacted sites that serves as a basis for regulatory/technical evaluation of site-specific risk to human health and the environment.

The research team collected field data and surveyed existing data on mineralogy and groundwater chemistry from a series of sites in which a pulse of hydrocarbons were introduced as a result of industrial activity. We report on our findings regarding sources of arsenic, groundwater chemistry, mechanisms of mobilization and attenuation, and fate of arsenic under a series of conceptual models of hydrocarbon biodegradation.


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