2018 ESA Annual Meeting (August 5 -- 10)

COS 129-2 - Climate change may worsen mercury pollution in northern hardwood forests

Friday, August 10, 2018: 8:20 AM
356, New Orleans Ernest N. Morial Convention Center
Yang Yang1, Linghui Meng2, Ruth D. Yanai1, Charles T. Driscoll2, Mario Montesdeoca2, Pamela Templer3, Lindsey E. Rustad4 and Heidi Asbjornsen5, (1)Forest and Natural Resources Management, SUNY College of Environmental Science and Forestry, Syracuse, NY, (2)Department of Civil and Environmental Engineering, Syracuse University, Syracuse, NY, (3)Department of Biology, Boston University, Boston, MA, (4)Northern Research Station, USDA Forest Service, Durham, NH, (5)Department of Natural Resources and the Environment, University of New Hampshire, Durham, NH
Background/Question/Methods

Mercury (Hg) is a neurotoxic pollutant emitted by anthropogenic activities that can be transported long distances and deposited in remote forested areas. Major pathways that contribute to Hg accumulation and retention in forest soils are throughfall, litterfall, bidirectional gas fluxes, and leaching in soil solutions all of which will likely be altered under changing climate. Under future climate, we expect more frequent extreme events such as ice storms and drought, warmer soils, and more frequent soil freeze and thaw cycles due to a reduced snowpack. We took advantage of three ongoing climate-change manipulation studies at the Hubbard Brook Experimental Forest, New Hampshire, USA: a combined growing season soil warming and winter freezing experiment, throughfall exclusion to mimic drought, and a simulated ice storm experiment. Across these three studies, we compared Hg inputs in throughfall and leaf litterfall and Hg outputs in soil gas fluxes in spring, summer, and fall of 2017.

Results/Conclusions

The soil temperature manipulation experiment increased soil Hg evasion. The warming plot and plot with combined warming and winter freezing had 28% and 32% higher soil Hg evasion than the reference plot in June, 36% and 40% higher in August and 26% and 30% higher in October, respectively. The drought plot had 20 ~ 22% lower soil Hg evasion than the reference plot in all three seasons.

The simulated ice storm decreased inputs of Hg into forest soils from litterfall and throughfall, and increased outputs through soil Hg evasion and leaching in soil solution. Litter Hg concentrations were not affected by the simulated ice storm compared to the reference plot. Throughfall Hg concentration was 14% lower in the ice treated plot than the reference plot. The ice treated plot had 31% higher soil Hg evasion in June, 48% higher in August and 28% higher in October compared to the reference plot. Concentrations of Hg in lysimeter solutions in the ice treated plot were 2.5 times those in the reference plot.

These observations suggest that climate changes such as warmer air temperatures and intense ice storms are likely to exacerbate Hg pollution by releasing Hg sequestered in forest soils.