Trend and variability of total gaseous mercury (TGM) in the state of Connecticut, USA during 1997-1999

A statewide total gaseous mercury (TGM) monitoring campaign was conducted from January 1997 to December 1999 in the State of Connecticut, U. S. A. Eight monitoring sites with different characteristics of geographical location ( coastal vs. interior) and land use ( rural vs. urban) were included in the monitoring program. Statistical procedures were utilized to evaluate the temporal trend and spatial distribution of the TGM concentration in the State, and the influence of long-range transport from non-local sources. The statewide mean TGM concentration was 2.08 ng m(-3). The annual mean concentration had no significant differences among the three years of measurements for all the sites. Weak seasonal variations were detected in the State with higher ambient TGM concentration found in warmer seasons. Urban areas in general had higher TGM concentrations than rural areas. The effect of site location of the monitoring sites on TGM concentration was interacted with land use characteristics. Waterbury site with extremely high concentration measurements was the major cause for this interaction. The long-range transport of TGM from remote sources showed an important influence on local ambient concentrations, by explaining over 45% of the total variance of the ambient TGMconcentration for most sites. Local sources were responsible for the extremely high TGMconcentration in the Waterbury site. The TGM concentrations at Voluntown, Hammonasset and Avery Point in southeast Connecticut were likely to be affected by some local sources.