Abstract
Mercury is a major pollutant in the Amazon River system, and its levels in fish and human hair are usually above the limit recommended by health agencies. The objective of this study was to analyze the methylmercury (MeHg) concentration in fish tissue from the Roosevelt River. The river’s water velocity, depth, pH, temperature, electrical conductivity, dissolved oxygen and substrate type were measured, and fifty specimens distributed in 14 fish species were collected. A total of 64.3% of the sampled species were of the order Characiform and 71.4% of the species were carnivores. Fifty percent of the species had MeHg concentrations above threshold limit (Hg-T 0.5 mg kg-1) established for food by the World Health Organization. Cichla monoculus had the highest value of MeHg (2.45 mg kg-1). The MeHg concentration in fish varied according to dietary habits. The study also found bioaccumulation of MeHg in fish tissue in the following descending order: carnivorous > detritivorous > frugivore. Low significant correlations were found between fish weight or length and MeHg. Further studies on MeHg contamination are recommended in tissues of fish consumed in human riverine communities in the Roosevelt River Basin.
Highlights
Mercury (Hg) is one of the most hazardous environmental pollutants, with a large number of physical and chemical forms (Nevado et al, 2010)
Hg is a naturally occurring element, anthropogenic activities may release it into the environment (Cristol et al, 2008), and there has been an increase in the amount currently cycled in the biosphere (Hugget et al, 2001)
High concentrations of mercury found in the Amazonian ecosystem have been usually attributed to gold mining (Nriagu et al, 1992), soils with relatively high concentrations of natural mercury (Lechler et al, 2000), and the atmospheric transport and deposition of mercury from anthropogenic activities (Lacerda, 1995)
Summary
Mercury (Hg) is one of the most hazardous environmental pollutants, with a large number of physical and chemical forms (Nevado et al, 2010). Hg is a naturally occurring element, anthropogenic activities may release it into the environment (Cristol et al, 2008), and there has been an increase in the amount currently cycled in the biosphere (Hugget et al, 2001). Complex chemical transformations cause the cycling of Hg in the environment, methylmercury (MeHg) formation is the predominant reason for Hg bioaccumulation in the aquatic food chain (Dorea et al, 2006). Research has shown that about 60 to 95% of the total mercury in muscle tissue occurs in the form of MeHg, which is one of the most toxic forms for humans (WHO, 1991). The concentrations of mercury in Amazonian fishes have been a matter of concern for human health and wildlife for over 25 years (Kehrig et al, 2008). High concentrations of mercury found in the Amazonian ecosystem have been usually attributed to gold mining (Nriagu et al, 1992), soils with relatively high concentrations of natural mercury (Lechler et al, 2000), and the atmospheric transport and deposition of mercury from anthropogenic activities (Lacerda, 1995)
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