Modeling the sensitivity of soil mercury storage to climate-induced changes in soil carbon pools

Background/Question/Methods

Soil has long been considered the largest mercury pool with the main input from the atmosphere through wet and dry deposition. Numerous studies have reported the high degree of coupling between soil carbon and soil mercury. Results from a recent systematic study of mercury across United States show high correlation of soil mercury concentrations with soil carbon, precipitation, latitude, and soil clay content.
The purpose of this study is to (i) use the relationship between soil mercury and soil carbon, clay content, latitude, and precipitation to explore regional variability of the soil mercury content across the United States; (ii) assess the sensitivity of the top soil mercury pool to changing temperature, precipitation and carbon dioxide using NCAR’s Community Land Model.

Results/Conclusions

The top soil mercury content ranged from 1 mg/m² in the southwestern United States to 140 mg/m² in the northeastern and northwestern coastal areas.  Soil mercury was most sensitive to altered precipitation: it decreased by up to 70% from the present-day values when precipitation was decreased by 50% and increased by up to 150% from the present-day values when precipitation was increased by 50%. Elevated carbon dioxide increased top soil mercury by up to 20% from the present-day values. Elevated temperature decreased top soil mercury pool by up to 20% of the present-day values when temperature was increased by 6°C. The results suggest that in future soil mercury pool will be regulated mostly by precipitation as well as changes in the soil carbon.