Quantification and speciation of mercury in streams and rivers sediment samples from Paracatu, MG, Brazil, using a direct mercury analyzer®

Determination and human health risk assessment of mercury in honey from the Brazilian eastern amazon

Honey has nutritional and therapeutic properties that bring various health benefits. Heavy metals are a major source of environmental pollution. The aim of this study was to determine mercury levels in honey samples from the Brazilian eastern amazon using a direct mercury analyzer (DMA) and human health risk assessment. The levels of Hg found in the samples ranged from 0.10 to 0.73 ng g-1, except for 13 samples which were below the detection limit. The values estimates of average dietary exposure to total mercury in honey for adults were below the PTWI (4 µg kg-1), thus presenting a low risk for the percentage of exposure, and the target hazard quotient (THQ) evaluation obtained values below 1. This study shown that Hg are accumulating in honey, presumably facilitated by dietary sources of the bees and direct environmental exposure.

Jackfruit seed biochar-apatite amendments: investigating changes in lead and zinc's fractionation in the multi-metal-contaminated soil

Multi-metal contamination in soil presents major environmental and agricultural challenges globally, impacting the feasibility of phytoremediation. This study investigated the efficacy of jackfruit seed-derived biochar (JSB) produced at 300 °C (JSB300) and 600 °C (JSB600), combined with apatite, to mitigate potentially toxic elements (PTEs), thus influencing bioavailability, in soils heavily contaminated with lead (Pb) and zinc (Zn). The primary objective was to determine how these amendments altered the chemical fractions of Pb and Zn using Tessier's sequential extraction procedure. Soil samples with initial concentrations of 3052.5 ± 15.6 mg kg-1 Pb and 1531.0 ± 20.2 mg kg-1 Zn were treated with biochar and apatite at 5%, 10%, 2.5:2.5%, and 5:5% (w/w). Results revealed that JSB600 and JSB300 at a 10% ratio, achieved the most significant reduction in exchangeable Pb and Zn fractions, decreasing them by up to 49.3 and 48.6%, respectively, within one month. This substantial decrease in readily available metal fractions, alongside concurrent increases in soil pH (+22.6%), organic carbon (+290.3%), and electrical conductivity (+249.0%), suggests that jackfruit seed biochar and apatite can significantly improve soil conditions for phytostabilization, by reducing metal bioavailability, or potentially for phytoextraction by influencing specific metal chemical fractions, in multi-metal-contaminated environments, enhancing soil conditions for remediation.

Comparison of the Performance of ICP-MS, CV-ICP-OES, and TDA AAS in Determining Mercury in Marine Sediment Samples

Mercury (Hg) determination in marine sediment is an analytical challenge due to the toxicity of this element even at low concentrations (up to 130 μg kg-1 in marine sediments) and complex matrices. Therefore, it is necessary to use analytical techniques that have high sensitivity, selectivity, and low limits of quantification (LoQ). In this study, two methods that require sample treatment and one method with direct sampling were studied. The techniques studied were inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry with cold vapor generation (CV-ICP-OES), and atomic absorption spectrometry with thermodecomposition and amalgamation (TDA AAS) for Hg determination in marine sediment samples. Since ICP-MS has more studies in the literature, optimization with design of experiments was developed for CV-ICP-OES and TDA AAS. Although it was found to have low levels of instrumental LoQ for all three techniques, differences were found once the method LoQ was calculated. The calculation for method LoQ considers all analytical procedures executed, including sample treatment, which provides a 100-fold dilution for ICP-MS and CV-ICP-OES. The method LoQ obtained were 1.9, 165, and 0.35 μg kg-1 for ICP-MS, CV-ICP-OES, and TDA AAS, respectively. Comparing marine sediment sample analyses, Hg concentrations had no statistical difference when determined by ICP-MS and TDA AAS. It was not possible to determine Hg in marine sediment samples by CV-ICP-OES due to the high method LoQ obtained (165 μg kg-1). Although ICP-MS has the advantage of being a multielemental technique, it is high-value equipment and needs a large volume of argon, which has a high cost in the market, and it requires sample treatment. On the other hand, TDA AAS-based spectrometer DMA-80 performs direct sampling, avoiding the pretreatment stage, and has a relatively lower cost, both in terms of initial investment and maintenance, while maintaining the high sensitivity, accuracy, and precision required for Hg determination on marine sediment samples.

Elemental Speciation Analysis in Environmental Studies: Latest Trends and Ecological Impact

Speciation analysis is a key aspect of modern analytical chemistry, as the toxicity, environmental mobility, and bioavailability of elemental analytes are known to depend strongly on an element’s chemical species. Henceforth, great efforts have been made in recent years to develop methods that allow not only the determination of elements as a whole, but also each of its separate species. Environmental analytical chemistry has not ignored this trend, and this review aims to summarize the latest methods and techniques developed with this purpose. From the perspective of each relevant element and highlighting the importance of their speciation analysis, different sample treatment methods are introduced and described, with the spotlight on the use of modern nanomaterials and novel solvents in solid phase and liquid-liquid microextractions. In addition, an in-depth discussion of instrumental techniques aimed both at the separation and quantification of metal and metalloid species is presented, ranging from chromatographic separations to electro-chemical speciation analysis. Special emphasis is made throughout this work on the greenness of these developments, considering their alignment with the precepts of the Green Chemistry concept and critically reviewing their environmental impact.

The assessment and remediation of mercury contaminated sites: A review of current approaches

Remediation of mercury (Hg) contaminated sites has long relied on traditional approaches, such as removal and containment/capping. Here we review contemporary practices in the assessment and remediation of industrial-scale Hg contaminated sites and discuss recent advances. Significant improvements have been made in site assessment, including the use of XRF to rapidly identify the spatial extent of contamination, Hg stable isotope fractionation to identify sources and transformation processes, and solid-phase characterization (XAFS) to evaluate Hg forms. The understanding of Hg bioavailability for methylation has been improved by methods such as sequential chemical extractions and porewater measurements, including the use of diffuse gradient in thin-film (DGT) samplers. These approaches have shown varying success in identifying bioavailable Hg fractions and further study and field applications are needed. The downstream accumulation of methylmercury (MeHg) in biota is a concern at many contaminated sites. Identifying the variables limiting/controlling MeHg production-such as bioavailable inorganic Hg, organic carbon, and/or terminal electron acceptors (e.g. sulfate, iron) is critical. Mercury can be released from contaminated sites to the air and water, both of which are influenced by meteorological and hydrological conditions. Mercury mobilized from contaminated sites is predominantly bound to particles, highly correlated with total sediment solids (TSS), and elevated during stormflow. Remediation techniques to address Hg contamination can include the removal or containment of Hg contaminated materials, the application of amendments to reduce mobility and bioavailability, landscape/waterbody manipulations to reduce MeHg production, and food web manipulations through stocking or extirpation to reduce MeHg accumulated in desired species. These approaches often rely on knowledge of the Hg forms/speciation at the site, and utilize physical, chemical, thermal and biological methods to achieve remediation goals. Overall, the complexity of Hg cycling allows many different opportunities to reduce/mitigate impacts, which creates flexibility in determining suitable and logistically feasible remedies.

Adsorption of gaseous elemental mercury on soils: Influence of chemical and/or mineralogical characteristics

Gaseous elemental Hg is stable enough to be transported over long distances. Some of the most important sources of Hg in the atmosphere are artisanal gold mining activities and forest fires. Both of these sources are particularly prevalent in the Amazonia region. Information regarding the capacity of soils for retaining Hg transported by the atmosphere is very important for understanding the metal cycle in the environment. The aim of this work was to study gaseous elemental Hg adsorption in soils with different physical and chemical characteristics. For this purpose, soils from different regions in Brazil and Colombia influenced or possibly influenced by gold mining activities and forest fires were studied. Hg adsorption tests were conducted by exposing soil samples to a gaseous elemental Hg atmosphere for 144 h. The total Hg concentration (THg) and Hg oxidation states were monitored using a direct Hg analyzer. Sample characterization analyses were performed. THg values obtained before the adsorption tests were 43-413 and 144-590 µg kg^-1 for grain size fractions below 2 and 0.063 mm, respectively. The predominant species found was Hg²⁺, with abundance levels from 68% to 99%. The results show a wide range of enhanced Hg retention capacities among the samples, ranging from 13 to 2236 times the initial concentration, and the speciation results demonstrate a decrease in the oxidized species range, from 21% to 78%. The statistical analysis indicated the importance of Mn-bearing minerals for the processes of adsorption/oxidation of gaseous elemental Hg in soils. These results contribute to the elucidation of the processes that occur with Hg at the soil/atmosphere interface and may help to explain the high concentrations of Hg found in Amazonian soils where no gold mining activities are practiced.