Distribution of Total Mercury and Methyl Mercury in Water, Sediment, and Fish from South Florida Estuaries

Abstract

Concentrations of total mercury and methyl mercury were determined in sediment and fish collected from estuarine waters of Florida to understand their distribution and partitioning. Total mercury concentrations in sediments ranged from 1 to 219 ng/g dry wt. Methyl mercury accounted for, on average, 0.77% of total mercury in sediment. Methyl mercury concentrations were not correlated with total mercury or organic carbon content in sediments. The concentrations of total mercury in fish muscle were between 0.03 and 2.22 (mean: 0.31) micrograms/g, wet wt, with methyl mercury contributing 83% of total mercury. Methyl mercury concentrations in fish muscle were directly proportional to total mercury concentrations. The relationship of total and methyl mercury concentrations in fish to those of sediments from corresponding locations was fish-species dependent, in addition to several abiotic factors. Among fish species analyzed, hardhead catfish, gafftopsail catfish, and sand seatrout contained the highest concentrations of mercury. Filtered water samples from canals and creeks that discharge into the Florida Bay showed mercury concentrations of 3-7.4 ng/L, with methyl mercury accounting for < 0.03-52% of the total mercury. Consumption of fish containing 0.31 microgram mercury/g wet wt, the mean concentration found in this study, at rates greater than 70 g/day, was estimated to be hazardous to human health.

Total mercury in the night shark, Carcharhinus signatus in the western equatorial Atlantic Ocean

“…This value was more than five times the 30 µg of Hg per day maximum intake concentration established by the World Health Organization (WHO). Results of this magnitude have already limited the human consumption of piscivorous species in the USA (Kannan et al, 1998) and Australia (Simpfendorfer and Donohue, 1998). Higher Hg concentration in apex predator fish species is recognizably a problem associated with the biomagnification process Marcovecchio et al (1991).…”

Mercury and methylmercury in muscle tissue of chub from the Elbe River main tributaries

“…The hazard index was calculated according to Kannan et al (1998) using the reference dose (RfD) for THg (0.3 µg/kg body weight per day) set forth by US EPA.…”

“…Potential health hazard caused by mercury in fish was calculated according to the method of Kannan et al (1998), who described the calculation of the hazard index associated with fish consumption. The hazard indexes calculated for Hg are given in Table 3.…”

Clapper rails as indicators of mercury and PCB bioavailability in a Georgia saltmarsh system

“…The normalization was performed since studies have shown predictable associations of lipophilic contaminants as well as MeHg with detrital carbon (Castro and Vale 1995;King et al 2001;Nhan et al 2001). However, other studies from the southeast have shown the relationship between Hg and carbon content to be complex (Kannan et al 1998b), most likely because carbon is only one component that can influence methylation processes.…”