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Mercury cycling in terrestrial watersheds

By:  and 
Edited by: Michael S. Banks

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Abstract

This chapter discusses mercury cycling in the terrestrial landscape, including inputs from the atmosphere, accumulation in soils and vegetation, outputs in streamflow and volatilization, and effects of land disturbance. Mercury mobility in the terrestrial landscape is strongly controlled by organic matter. About 90% of the atmospheric mercury input is retained in vegetation and organic matter in soils, causing a buildup of legacy mercury. Some mercury is volatilized back to the atmosphere, but most export of mercury from watersheds occurs by streamflow. Stream mercury export is episodic, in association with dissolved and particulate organic carbon, as stormflow and snowmelt flush organic-rich shallow soil horizons. The terrestrial landscape is thus a major source of mercury to downstream aquatic environments, where mercury is methylated and enters the aquatic food web. With ample organic matter and sulfur, methylmercury forms in uplands as well—in wetlands, riparian zones, and other anoxic sites. Watershed features (topography, land cover type, and soil drainage class) are often more important than atmospheric mercury deposition in controlling the amount of stream mercury and methylmercury export. While reductions in atmospheric mercury deposition may rapidly benefit lakes, the terrestrial landscape will respond only over decades, because of the large stock and slow turnover of legacy mercury. We conclude with a discussion of future scenarios and the challenge of managing terrestrial mercury.

Additional publication details

Publication type Book chapter
Publication Subtype Book Chapter
Title Mercury cycling in terrestrial watersheds
Year Published 2012
Language English
Publisher University of California Press
Publisher location Berkeley, CA
Contributing office(s) New Hampshire-Vermont Water Science Center
Description 24 p.
Larger Work Type Book
Larger Work Title Mercury in the environment: pattern and process
First page 119
Last page 142
Online Only (Y/N) N
Additional Online Files (Y/N) N