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Geomorphic controls on mercury accumulation in soils from a historically mined watershed, Central California Coast Range, USA

Applied Geochemistry

By:
, ,
DOI: 10.1016/j.apgeochem.2009.04.020

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Abstract

Historic Hg mining in the Cache Creek watershed in the Central California Coast Range has contributed to the downstream transport of Hg to the San Francisco Bay-Delta. Different aspects of Hg mobilization in soils, including pedogenesis, fluvial redistribution of sediment, volatilization and eolian transport were considered. The greatest soil concentrations (>30 mg Hg kg-1) in Cache Creek are associated with mineralized serpentinite, the host rock for Hg deposits. Upland soils with non-mineralized serpentine and sedimentary parent material also had elevated concentrations (0.9-3.7 mg Hg kg-1) relative to the average concentration in the region and throughout the conterminous United States (0.06 mg kg-1). Erosion of soil and destabilized rock and mobilization of tailings and calcines into surrounding streams have contributed to Hg-rich alluvial soil forming in wetlands and floodplains. The concentration of Hg in floodplain sediment shows sediment dispersion from low-order catchments (5.6-9.6 mg Hg kg-1 in Sulphur Creek; 0.5-61 mg Hg kg-1 in Davis Creek) to Cache Creek (0.1-0.4 mg Hg kg-1). These sediments, deposited onto the floodplain during high-flow storm events, yield elevated Hg concentrations (0.2-55 mg Hg kg-1) in alluvial soils in upland watersheds. Alluvial soils within the Cache Creek watershed accumulate Hg from upstream mining areas, with concentrations between 0.06 and 0.22 mg Hg kg-1 measured in soils ~90 km downstream from Hg mining areas. Alluvial soils have accumulated Hg released through historic mining activities, remobilizing this Hg to streams as the soils erode.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Geomorphic controls on mercury accumulation in soils from a historically mined watershed, Central California Coast Range, USA
Series title:
Applied Geochemistry
DOI:
10.1016/j.apgeochem.2009.04.020
Volume
24
Issue:
8
Year Published:
2009
Language:
English
Publisher:
Elsevier
Contributing office(s):
Crustal Geophysics and Geochemistry Science Center
Description:
11 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
1538
Last page:
1548