Mercury speciation and mobilization in a wastewater-contaminated groundwater plume

Environmental Science & Technology
By: , and 



We measured the concentration and speciation of mercury (Hg) in groundwater down-gradient from the site of wastewater infiltration beds operated by the Massachusetts Military Reservation, western Cape Cod, Massachusetts. Total mercury concentrations in oxic, mildly acidic, uncontaminated groundwater are 0.5–1 pM, and aquifer sediments have 0.5–1 ppb mercury. The plume of impacted groundwater created by the wastewater disposal is still evident, although inputs ceased in 1995, as indicated by anoxia extending at least 3 km down-gradient from the disposal site. Solutes indicative of a progression of anaerobic metabolisms are observed vertically and horizontally within the plume, with elevated nitrate concentrations and nitrate reduction surrounding a region with elevated iron concentrations indicating iron reduction. Mercury concentrations up to 800 pM were observed in shallow groundwater directly under the former infiltration beds, but concentrations decreased with depth and with distance down-gradient. Mercury speciation showed significant connections to the redox and metabolic state of the groundwater, with relatively little methylated Hg within the iron reducing sector of the plume, and dominance of this form within the higher nitrate/ammonium zone. Furthermore, substantial reduction of Hg(II) to Hg0 within the core of the anoxic zone was observed when iron reduction was evident. These trends not only provide insight into the biogeochemical factors controlling the interplay of Hg species in natural waters, but also support hypotheses that anoxia and eutrophication in groundwater facilitate the mobilization of natural and anthropogenic Hg from watersheds/aquifers, which can be transported down-gradient to freshwaters and the coastal zone.
Publication type Article
Publication Subtype Journal Article
Title Mercury speciation and mobilization in a wastewater-contaminated groundwater plume
Series title Environmental Science & Technology
DOI 10.1021/es402441d
Volume 47
Issue 23
Year Published 2013
Language English
Publisher American Chemical Society
Contributing office(s) National Research Program - Western Branch
Description 11 p.
First page 13239
Last page 13249
Country United States
State Massachusetts
Other Geospatial Cape Cod
Datum 1927 North American datum
Projection Polyconic projection
Google Analytic Metrics Metrics page
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