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Source Identification of Florida Bay's Methylmercury Problem: Mainland Runoff Versus Atmospheric Deposition and In situ Production

Figures and Tables

Study Area and Methods
Results and Discussion
>Figures and Tables


Fig. 1 Map of Florida Bay and its watershed showing sampling stations along two transects and at a single reference site. The Mercury Deposition Network (MDN) site is also shown

Fig. 2 Box plots showing the median, the 25th/75th percentile and the 10th/90th percentile concentrations of unfiltered total mercury (THg), methylmercury (MeHg), percent of THg as MeHg (%MeHg) and salinity of surface water samples collected quarterly from February 2000 through September 2002. Sites with similar letter designations within a transect did not differ significantly

Fig. 3 Box plots of filtered total mercury (THgF), filtered methylmercury (MeHgF) and % MeHg of surface water samples collected contemporaneously with unfiltered samples.

Fig. 4 Time series of water column concentrations of THg, MeHg and salinity. Bottom panel shows flows and rainfall measured at Taylor River (Taylor Slough Basin transect) and Trout Creek (C-111 Basin transect)

Fig. 5 Time series of filterable THg and MeHg

Fig. 6 Bar graph showing concentrations of THg, MeHg and percent of THg as MeHg in composite samples of sediment collected along Taylor Slough transect and at the reference site on a roughly semi-annual basis from late February 2000 through September 2002. Salinity measured just above bottom is also shown

Fig. 7 Bar graph showing concentrations of THg, MeHg and percent of THg as MeHg in sediment collected along C-111 Canal transect; freshwater marsh sites were sampled on an irregularly basis depending on airboat access. Salinity measured just above bottom is also shown

Fig. 8 Percent 202Hg methylation during a 24-h incubation of cores collected along transects.

Fig. 9 Relationship between organic content (%LOI) of sediments from top of cores and ambient THg, ambient MeHg and percent 202Hg methylation in incubated cores


Table 1 Comparison of median (and maximum) concentrations reported by the different contract laboratories for different analyte-matrix combinations

Table 2 Results of laboratory and field quality control check samples reported by the primary contract laboratory

Table 3 Source of hydrometeorological data used to estimate mass loads

Table 4 Surface water discharges and seasonal mass loads of (total mercury THg) and methylmercury (MeHg) at various locations by water-year (wet season is May-October, dry season is from November through April of the following year).

Table 5 Seasonal rainfall totals and loads from wet atmospheric deposition to select basins by water-year

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