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#           Stream mercury export in response to contemporary timber harvesting methods (Pacific Coastal Mountains, Oregon, USA)      

      January 25, 2018    

Land-use activities can alter hydrological and biogeochemical processes that can affect the fate, transformation, and transport of mercury (Hg).  Previous studies in boreal forests have shown that forestry operations can have profound, but variable effects on Hg export and methylmercury (MeHg) formation.  The Pacific Northwest is an important timber producing region that receives large atmospheric Hg loads, but the impact of forest harvesting on Hg mobilization has not been directly studied and was the focus of our investigation.  Stream discharge was measured continuously and Hg and MeHg concentrations measured monthly for 1.5 years following logging in three paired harvested and un-harvested catchments.  There was no significant difference in particulate-bound Hg concentrations or loads in the harvested and unharvested catchments which may have resulted from the best management practices aimed at minimizing erosion.  However, the harvested catchments had significantly higher discharge (32%), filtered Hg concentrations (28%), filtered Hg loads (80%), and dissolved organic carbon (DOC) loads (40%) compared to forested catchments.  MeHg concentrations were low (mostly <0.05 ng L-1) in both harvested, un-harvested and downstream samples due to well-drained/unsaturated soil conditions and steep slopes with high energy eroding stream channels that were not conducive to the development of anoxic conditions. These results have important implications for the role forestry operations have in affecting catchment retention and export of Hg pollution.

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#### Collin Eagles-Smith

##### Supervisory Research Ecologist

Forest and Rangeland Ecosystem Science Center

ceagles-smith@usgs.gov

541-750-0949

#### David P Krabbenhoft

##### Scientist Emeritus

Mercury Research Laboratory

Mercury Research Laboratory

dpkrabbe@usgs.gov

608-335-4234

## Related Content

#### Collin Eagles-Smith

##### Supervisory Research Ecologist

Forest and Rangeland Ecosystem Science Center

ceagles-smith@usgs.gov

541-750-0949

#### David P Krabbenhoft

##### Scientist Emeritus

Mercury Research Laboratory

Mercury Research Laboratory

dpkrabbe@usgs.gov

608-335-4234

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####               Forest and Rangeland Ecosystem Science Center (FRESC) Headquarters          

777 NW 9th StSuite 400Corvallis, OR97330United States

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####               Oregon Water Science Center          

601 SW 2nd Ave Ste 1950Portland, OR97204United States

####             Water Resources Mission Area - Headquarters        

USGS Headquarters12201 Sunrise Valley DriveReston, VA20192United States

####               Upper Midwest Water Science Center - Madison, WI, Office          

1 Gifford Pinchot DriveMadison, WI53726United States

608-828-9901

608-821-3817

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