Differential subsurface mobilization of ambient mercury and isotopically enriched mercury tracers in a harvested and residue harvested hardwood forest in northern Minnesota
| Autor: | Susan L. Eggert, Carl P. J. Mitchell, Randall K. Kolka, Colin P. R. McCarter, Stephen D. Sebestyen |
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| Rok vydání: | 2021 |
| Předmět: |
Biogeochemical cycle
010504 meteorology & atmospheric sciences chemistry.chemical_element 04 agricultural and veterinary sciences 15. Life on land 01 natural sciences Mercury (element) chemistry 13. Climate action Environmental chemistry TRACER Soil water Dissolved organic carbon 040103 agronomy & agriculture 0401 agriculture forestry and fisheries Environmental Chemistry Environmental science Precipitation Subsurface flow Surface runoff 0105 earth and related environmental sciences Earth-Surface Processes Water Science and Technology |
| Zdroj: | Biogeochemistry. 154:119-138 |
| ISSN: | 1573-515X 0168-2563 |
| Popis: | Mercury is a global pollutant of critical concern but its movement through terrestrial upland systems is poorly understood. We investigated whether forest harvesting practices and varying hydrological conditions resulted in different subsurface transport pathways, fluxes and proportions of recent vs. ambient mercury in runoff. In a multiyear field experiment, we measured subsurface lateral mercury fluxes at three adjacent hillslope plots, including one that was not harvested, one where all biomass was removed after harvest, and one where residual biomass was left after harvest. Two different enriched stable mercury isotopes (Hg tracer) were added to the hillslope plots (one pre-harvest and one post-harvest) to help differentiate between recently deposited mercury and ambient mercury in soils, as well as to identify changes between years. More Hg tracer was recovered in runoff post-harvest (16.2–54.0 μg) than pre-harvest (3.7–11.8 μg) from both harvested hillslopes, but differences between harvested hillslopes were not significant. The movement of Hg tracer was governed by periods of near surface preferential flow that was enhanced by forest harvesting. Runoff Hg tracer concentrations were significantly and inversely related to both event runoff magnitude (R2 = 0.85) and runoff ratio (R2 = 0.81). Insignificant relationships between Hg tracer concentrations and both DOC and precipitation pH suggest that for recently deposited mercury, the overarching controls on mobilization were hydrological rather than biogeochemical. The dependence of mercury mobilization on the routing of precipitation to different subsurface flow pathways suggests an important interaction between climate and the age of mercury pools for mercury transport from terrestrial landscapes. |
| Databáze: | OpenAIRE |
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