title: Submarine groundwater discharge of total mercury and monomethylmercury to central California coastal waters.
abstract: Fluxes of total mercury (Hg(T)) and monomethylmercury (MMHg) associated with submarine groundwater discharge (SGD) at two sites onthe central California coast were estimated by combining measurements of Hg(T) and MMHg in groundwater with the use of short-lived, naturally occurring radium isotopes as tracers of groundwater inputs. Concentrations of Hg(T) were relatively low, ranging from 1.2 to 28.3 pM in filtered groundwater, 0.8 to 11.6 pM in filtered surface waters, and 2.5 to 12.9 pM in unfiltered surface waters. Concentrations of MMHg ranged from < 0.04 to 3.1 pM in filtered groundwater, < 0.04 to 0.53 pM in filtered surface waters, and 0.07 to 1.2 pM in unfiltered surface waters. Multiple linear regression analysis identified significant (p < 0.05) positive correlations between dissolved groundwater concentrations of Hg(T) and those of NH4+ and SiO2, and between dissolved groundwater concentrations of MMHg and those of Hg(T) and NH4+. However, such relationships did not account for the majority of the variability in concentration data for either mercury species in groundwater. Fluxes of Hg(T) via SGD were estimated to be 250 +/- 160 nmol day m(-1) of shoreline at Stinson Beach and 3.0 +/- 2.0 nmol m(-2) day(-1) at Elkhorn Slough. These Hg(T) fluxes are substantially greater than net atmospheric inputs of Hg(T) reported for waters in nearby San Francisco Bay. Calculated fluxes of MMHg to coastal waters via SGD were 10 +/- 12 nmol day(-1) m(-1) of shoreline at Stinson Beach and 0.24 +/- 0.21 nmol m(-2) day at Elkhorn Slough. These MMHg fluxes are similar to benthic fluxes of MMHg out of surface sediments commonly reported for estuarine and coastal environments. Consequently, this work demonstrates that SGD is an important source of both Hg(T) and MMHg to coastal waters along the central California coast.
authors.affiliation: WIGS Laboratory, Department of Environmental Toxicology, and Institute of Marine Sciences, University of California, Santa Cruz, California 95064, USA. fblack@princeton.edu
authors.forename: Friank J
authors.initials: FJ
authors.lastname: Black
authors.forename: Adina
authors.initials: A
authors.lastname: Paytan
authors.forename: Karen L
authors.initials: KL
authors.lastname: Knee
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: De Sieyes
authors.forename: Priya M
authors.initials: PM
authors.lastname: Ganguli
authors.forename: Ellen
authors.initials: E
authors.lastname: Gray
authors.forename: A Russell
authors.initials: AR
authors.lastname: Flegal
mesh_terms: D002140:California; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods; D019015:Geologic Sediments; D008628:Mercury / Q000032:analysis*; D008767:Methylmercury Compounds / Q000032:analysis*; D011883:Radium / Q000032:analysis; D012044:Regression Analysis; D012623:Seawater / Q000032:analysis; D014867:Water / Q000737:chemistry; D014872:Water Movements; D014873:Water Pollutants / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis; D018508:Water Purification
chemical_list: D008767:Methylmercury Compounds; D014873:Water Pollutants; D014874:Water Pollutants, Chemical; D014867:Water; D008628:Mercury; D011883:Radium