Mercury speciation in environmental samples by cold vapour atomic absorption spectrometry with in situ preconcentration on a gold trap

Enhanced insight into the biogeochemical cycle of Hg in the Antarctic marine environment of Terra Nova Bay via isotopic analysis

Mercury (Hg) is a globally significant pollutant, which is particularly concerning due to its ability to undergo long-range atmospheric transport and its bioaccumulation and biomagnification in marine ecosystems, even in remote regions like Antarctica. This study explores the biogeochemical cycling of Hg in the marine coastal environment of Terra Nova Bay (Antarctica) by determining the total content of mercury (THg) and its isotopic composition in fish (Trematomus bernacchii), bivalve molluscs (Adamussium colbecki) and sediment samples, collected in 1996-1998 and 2021. Significantly lower THg concentrations are found in the organisms sampled in 2021 compared to those sampled in 1996-1998, with a concurrent shift toward higher δ202Hg (governed by mass-dependent isotope fractionation MDF) and lower Δ199Hg and Δ201Hg (governed by mass-independent isotope fractionation MIF) values. These results suggest changes in the exposure to Hg and the photochemical processes that the element and its species undergo, likely influenced by differences in the environmental conditions during the sampling periods, such as light exposure and ice cover. Sex-specific analysis of the 2021 fish samples further suggests differences in Hg accumulation and both MDF and MIF isotopic patterns between male and female specimens, emphasising a potential effect of sex on Hg exposure and dynamics. However, due to the limited number of individuals analyzed and the pooling of samples, this sex differentiation is still preliminary. Finally, the linear increase of Δ199Hg as a function of Δ201Hg during trophic transfer suggests MeHg bioaccumulation along the food chain. These findings provide valuable insights into the biogeochemical cycling of Hg in the Antarctic coastal marine environment and underscore the need for ongoing monitoring of Hg (including isotopic analysis) in this fragile ecosystem.

Ultra-trace determination of total mercury in Italian bottled waters

Mercury (Hg) is a widespread, highly toxic persistent pollutant with adverse health effects on humans. So far, concentrations below the method detection limit have always been reported by studies on the concentration of mercury in bottled water when determined using instrumental analytical methods. These are often very expensive and are unaffordable for many laboratories. In this work, a less expensive method based on cold vapour atomic fluorescence spectrometry has been employed to determine total mercury (Hg_T) concentrations in bottled natural mineral waters. In all, 255 waters representing 164 different typologies were analysed. They came from 136 springs located in 18 Italian regions. In all samples, Hg_T concentrations were found in the range of sub-nanogram to a few nanograms per litre, well below the National and European regulatory limit (1 μg L^-1). Differences in Hg_T concentrations were related not only to the environmental characteristics of the springs but also to the extent and impact of human activities. Higher concentrations were found in waters coming from regions with former mining and/or natural thermal and volcanic activity. These data allowed us to estimate the mercury intake by population (adults, children and toddlers) from drinkable mineral waters consumption. The mean mercury daily intake was found to be remarkably lower, not only than the provisional tolerable value (1 μg L^-1 according to European and Italian legislation) but also than the estimated provisional tolerable weekly intake (PTWI) value (4 μg kg^-1 body weight) recommended by the Joint FAO/WHO Expert Committee on Food Additives (JECFA).

Retrospective biomonitoring of chemical contamination in the marine coastal environment of Terra Nova Bay (Ross Sea, Antarctica) by environmental specimen banking

Antarctica offers a good opportunity to investigate planetary-scale pollution and climate change, and provides baseline values for contaminants such as Trace Elements (TEs) and Persistent Organic Pollutants (POPs). Literature data on contaminant levels in the Antarctic environment indicate that long-range atmospheric transport is the primary pathway by which pollutants from surrounding continents are carried to this pristine environment. However, local contamination sources represented by the scientific stations are also not negligible. Climate change and global warming are altering the global budget of anthropogenic contaminants and their monitoring in Antarctica ecosystems is very important to protect the global environment. In this work, eighty specimens of Adamussium colbecki (Smith, 1902), a benthic Antarctic scallop, collected from 1996 to 2009 and stored in the Antarctic Environmental Specimen Bank, were analyzed to quantify TEs and POPs, including polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs) and polycyclic aromatic hydrocarbons (PAHs). Metals concentrations were not affected by anthropogenic contributions, highlighting a natural accumulation with the age of the organism. Similarly, no temporal trend was found for PCNs, PCBs and PAHs. However, specimens collected during the summer 1997-98 showed enhanced concentration levels of PCBs and PAHs that could refer to a local anthropogenic source of contamination.

Synthesis, characterization and application of poly(acrylamide-co-methylenbisacrylamide) nanocomposite as a colorimetric chemosensor for visual detection of trace levels of Hg and Pb ions

In this study, a new colorimetric chemosensor based on TiO2/poly(acrylamide-co-methylenbisacrylamide) nanocomposites was designed for determination of mercury and lead ions at trace levels in environmental samples. The removal and preconcentration of lead and mercury ions on the sorbent was achieved due to sharing an electron pair of N and O groups of polymer chains with the mentioned heavy metal ions. The hydrogel sensor was designed by surface modification of a synthesized TiO2 nanoparticles using methacryloxypropyltrimethoxysilan (MAPTMS), which provided a reactive C=C bond that polymerized the acrylamide and methylenbisacrylamide. The sorbent was characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), EDS analysis and Fourier transform in frared (FT-IR) spectrometer. This nanostructured composite with polymer shell was developed as a sensitive and selective sorbent for adsorption of mercury and lead ions from aqueous solution at optimized condition. This method involves two-steps: (1) preconcentration of mercury and lead ions by the synthesized sorbent and (2) its selective monitoring of the target ions by complexation with dithizone (DZ). The color of the sorbent in the absence and presence of mercury and lead ions shifts from white to violet and red, respectively. The detection limit of the synthesized nanochemosensor for mercury and lead ions was 1 and 10 μg L(-1), respectively. The method was successfully applied for trace detection of mercury and lead ions in tap, river, and sea water samples.

Speciation analysis of mercury in water samples by dispersive liquid-liquid microextraction coupled to capillary electrophoresis

In this study, a method of pretreatment and speciation analysis of mercury by dispersive liquid-liquid microextraction along with CE was developed. The method was based on the fact that mercury species including methylmercury (MeHg), ethylmercury (EtHg), phenylmercury (PhHg), and Hg(II) were complexed with 1-(2-pyridylazo)-2-naphthol to form hydrophobic chelates and l-cysteine could displace 1-(2-pyridylazo)-2-naphthol to form hydrophilic chelates with the four mercury species. Factors affecting complex formation and extraction efficiency, such as pH value, type, and volume of extractive solvent and disperser solvent, concentration of the chelating agent, ultrasonic time, and buffer solution were investigated. Under the optimal conditions, the enrichment factors were 102, 118, 547, and 46, and the LODs were 1.79, 1.62, 0.23, and 1.50 μg/L for MeHg, EtHg, PhHg, and Hg(II), respectively. Method precisions (RSD, n = 5) were in the range of 0.29-0.54% for migration time, and 3.08-7.80% for peak area. Satisfactory recoveries ranging from 82.38 to 98.76% were obtained with seawater, lake, and tap water samples spiked at three concentration levels, respectively, with RSD (n = 5) of 1.98-7.18%. This method was demonstrated to be simple, convenient, rapid, cost-effective, and environmentally benign, and could be used as an ideal alternative to existing methods for analyzing trace residues of mercury species in water samples.

Sol-gel derived highly selective optical sensor for sensitive determination of the mercury(II) ion in solution

We report a versatile optical sensor by incorporating the indicator dye 4-phenyl-2,6-bis(2,3,5,6-tetrahydrobenzo[b][1,4,7]trioxononin-9-yl)pyrylium perchlorate into a sol-gel layer. The proposed optical sensor that is stable, fast and highly selective to Hg(2+) ions shows a significant absorbance signal change on exposure to an aqueous solution containing mercury(II) ion. The sensing film is able to determine mercury(II) ion in aqueous solution with a high selectivity over a wide dynamic range between 1.52x10(-9) and 1.70x10(-2)M, at pH 5, and a lower detection limit of 1.11x10(-9)M. Validation of the assay method revealed excellent performance characteristics for Hg(2+) ions over a wide variety of other metal ions, including good selectivity, long-term response stability and high reproducibility. Applications, for the direct determination of mercury(II) in real samples, gave the results with good correlation with the data obtained by using cold vapor atomic absorption spectrometry.