Land -atmosphere exchange of mercury in temperate wetlands

by Smith, Lora M., Ph.D., RUTGERS THE STATE UNIVERSITY OF NEW JERSEY - NEW BRUNSWICK, 2008, 194 pages; 3349591


Gaseous elemental mercury (Hg0) cycling in temperate wetlands was evaluated by performing an atmospheric deposition study in addition to in situ micrometeorological and laboratory dynamic flux chamber experiments examining New Jersey salt marsh sediments.

Mercury wet deposition was measured at an urban/suburban site in eastern central New Jersey (New Brunswick) and at a rural site in northwestern New Jersey (Belvidere). Volume-weighted mean mercury concentrations in precipitation were greater in New Brunswick (11 ng L-1) than Belvidere (8.6 ng L-1) and exhibited seasonality with highest concentrations in the summer. Over a seven year period (1999-2002 from Zhuang 2004, plus 2003-2006 from this study), mercury concentrations in New Brunswick precipitation decreased at a rate of 0.2 μg m-2 y-1, while over a three year period (2002-2005) in Belvidere, mercury concentrations were constant. Annual wet deposition fluxes for New Brunswick and Belvidere were 12 and 11 μg m-2 y-1 respectively, similar to previous estimates for New Jersey. No patterns were observed between Hg and other analyzed trace metals. Meteorological conditions also did not correlate, indicating local and regional sources.

In situ estimates of sediment-air mercury volatilization fluxes were an order of magnitude higher at the Secaucus High School Marsh (-375 to +677 ng m-2 h-1) than at the Great Bay estuary (-34 to +81 ng m-2 h-1). Mercury volatilization fluxes were positively correlated with solar radiation at the Great Bay estuary but only on one out of six sampling days in Secaucus, potentially a result of tides. Areally averaged annual mercury emissions from Secaucus (0.06 kg y -1) are much lower than those from industrial sources in New Jersey, but preliminary scaling up of mercury emissions estimated for the much larger Great Bay estuary (13 kg y-1) indicate that it is comparable to minor industrial sources in the State.

Laboratory flux chamber experiments showed that photochemistry is more important in sediment-air mercury volatilization than other physicochemical sediment characteristics. In the light, mercury flux from sediments was up to 50 times larger than in the dark, with the greatest emissions observed during visible + UV treatments, as observed in the natural environment.

AdviserJohn R. Reinfelder
Source TypeDissertation
SubjectsBiogeochemistry; Atmospheric sciences; Environmental science
Publication Number3349591

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