Title: Mercury Cycling in Florida Everglades

Speaker: Prof. Cai Yong

Moderator: Prof. WANG Huanyu

Time: 9:00 AM, July 25, 2014

Place: Room C305, IHEP Main Building

Abstract:

The Florida Everglades is a subtropical wetland ecosystem that mainly receives mercury (Hg) input from atmospheric deposition. Monitoring data show that total Hg (THg) concentrations in Everglades surface water and soil are typically within background levels (<10 ng/L for water and <500 ng/g for soil). However, elevated Hg levels (up to 3 mg/kg), comparable with those observed at highly contaminated sites, were detected in Everglades wildlife and have led to the issue of a fish consumption advisory for almost the entire Everglades. The unexpectedly high Hg levels in Everglades wildlife must therefore be driven by biogeochemical controls that make Hg available for bioaccumulation, rather than by high Hg loading. The elevated Hg levels in wildlife could be related to high methylmercury (MeHg) production rate in Everglades soil, which is a critical factor in Hg bioaccumulation. However, there are a number of biogeochemical processes, such as partitioning and methylation/demethylation of Hg, intermittent drying and rewetting, the sulfur cycling and P biogeochemistry, controlling Hg cycling in the Everglades. Our Laboratory has been actively engaged in the study of mercury biogeochemistry in this ecosystem over the last 20 years. This presentation, a brief summary of our efforts, will give a framework we used to address some of the key questions regarding mercury cycling in the ecosystem.