Mercury and methylmercury distribution in the intertidal surface sediment of a heavily anthrophogenically impacted saltwater-mangrove-sediment interplay zone

Abstract

Total mercury (THg) and methylmercury (MeHg) concentrations were determined from sediment samples collected from thirty sampling stations in Port Klang, Malaysia. Three stations had THg concentrations exceeding the threshold effect level of the Florida Department of Environmental Protection and the Canadian interim sediment quality guidelines. THg and MeHg concentrations were found to be concentrated in the Lumut Strait where inputs from the two most urbanized rivers in the state converged (i.e. Klang River and Langat River). This suggests that Hg in the study area likely originated from the catchments of these rivers. MeHg made up 0.06-94.96% of the sediment's THg. There is significant positive correlation (p < 0.01) between THg and MeHg concentrations. Significant positive correlation (p < 0.05) was also observed between fine sediment particles (i.e. clay and silt) with MeHg concentrations. Sediment particle size, however, was not found to have any influence on THg concentrations in the sediment in the study area.

Methylmercury in Industrial Harbor Sediments in Taiwan: First Observations on Its Occurrence, Distribution, and Measurement

“…The spatial distribution pattern of MeHg in the sediment was similar to that of T-Hg, TOC content, and ORP (Figure 3). Previous studies had indicated that MeHg concentration in the sediment was associated with T-Hg because MeHg in the sediments mainly was transferred by the bioavailable Hg via the biochemical effects [12,22]. Therefore, the sediments with the higher T-Hg concentration generally exhibited relatively higher MeHg concentration [12,23,24].…”

“…Previous studies had indicated that MeHg concentration in the sediment was associated with T-Hg because MeHg in the sediments mainly was transferred by the bioavailable Hg via the biochemical effects [12,22]. Therefore, the sediments with the higher T-Hg concentration generally exhibited relatively higher MeHg concentration [12,23,24]. Moreover, the estuary sediments with high TOC content and the highly anaerobic state could promote the activity of microorganism, which favors MeHg formation resulting in relatively higher MeHg concentration in the above environment [2].…”

“…The sediment characteristics (such as grain size, TOC, pH, and ORP) play an important role in the distributions of T-Hg and MeHg in the sediments, the correlation between the two is proposed above [12,15,40,41]. Table 5 lists the Pearson correlation matrix for the sediment characteristics, T-Hg, MeHg, and MeHg ratio.…”

“…However, a high sulfur content may hasten formation of Hg sulfide precipitates (e.g., HgS(s)), which in turn decreases the bioavailable Hg in the sediments and inhibits Hg methylation [2]. Therefore, environmental conditions and sediment characteristics result in variations in the distribution of MeHg in the sediments [11,12]. …”

“…Generally, the main steps of MeHg analysis procedures for solid samples are alkaline digestion (or acid leaching), tetraethylborate derivatization for reducing the polarity of target chemical, solvent extraction by heptane, benzene, toluene, dichloromethane, or hexane, chromatographic separation by gas chromatography (GC) or high performance liquid chromatography (HPLC), and detection by mass spectrometry (MS), electron capture detector (ECD), inductively coupled plasma mass spectrometry (ICP-MS), or cold vapour atomic fluorescence spectroscopy (CVAFS) [9,12,13,14]. This study analyzes MeHg content in sediments based on the above procedures and carried out qualitative and quantitative analyses to confirm the accuracy of the analytical results.…”