Odstraňování rtuti z kyselých roztoků chloridu rtuťnatého sorbenty připravenými katalyzovanou vulkanizací rostlinných olejů

Mercury is a metallic element, dangerous and toxic for the environment. Presently, the incineration of municipal solid waste (MSW) belongs to important sources of Hg emissions. Methods of conversion of metallic mercury and mercury compounds from soluble and toxic forms into water insoluble/non-toxic form (HgS) are sought after. Gaseous HCl and a significant part of HgCl2 vapors present in flue gas from incineration of MSW can be removed there by absorption in hot water. Efficiencies of Hg2+ removal from acidic water solutions by means of sorbents prepared by catalyzed reaction of sulfur with vegetable oils (inverse vulcanization) were studied. These kinds of sorbents were tested and found to be exploitable for selective removal of mercury ions from aqueous solutions, particularly from acidic solutions containing HCl at higher temperatures (50–75 °C). Presence of relatively high concentrations of salts of some other metallic elements (Fe, Zn, Ca) had only very small effects on Hg-sorption. Mercury adsorbed on such sorbents converts relatively quickly into a non-toxic form (HgS). Reactive sulfides and SH‑groups present on the surface of the sorbent particles contribute to a faster sorption of mercury and its conversion to HgS. Leaching of zinc from the catalyst (Zn‑diethyldithiocarbamate) present in the vulcanized sorbents is negligible at neutral conditions and small (about 10 %) at acidic conditions (pH = 1.5).

Expanded Diversity and Phylogeny of mer Genes Broadens Mercury Resistance Paradigms and Reveals an Origin for MerA Among Thermophilic Archaea

Mercury (Hg) is a highly toxic element due to its high affinity for protein sulfhydryl groups, which upon binding, can destabilize protein structure and decrease enzyme activity. Prokaryotes have evolved enzymatic mechanisms to detoxify inorganic Hg and organic Hg (e.g., MeHg) through the activities of mercuric reductase (MerA) and organomercury lyase (MerB), respectively. Here, the taxonomic distribution and evolution of MerAB was examined in 84,032 archaeal and bacterial genomes, metagenome assembled genomes, and single-cell genomes. Homologs of MerA and MerB were identified in 7.8 and 2.1% percent of genomes, respectively. MerA was identified in the genomes of 10 archaeal and 28 bacterial phyla previously unknown to code for this functionality. Likewise, MerB was identified in 2 archaeal and 11 bacterial phyla previously unknown to encode this functionality. Surprisingly, homologs of MerB were identified in a number of genomes (∼50% of all MerB-encoding genomes) that did not encode MerA, suggesting alternative mechanisms to detoxify Hg(II) once it is generated in the cytoplasm. Phylogenetic reconstruction of MerA place its origin in thermophilic Thermoprotei (Crenarchaeota), consistent with high levels of Hg(II) in geothermal environments, the natural habitat of this archaeal class. MerB appears to have been recruited to the mer operon relatively recently and likely among a mesophilic ancestor of Euryarchaeota and Thaumarchaeota. This is consistent with the functional dependence of MerB on MerA and the widespread distribution of mesophilic microorganisms that methylate Hg(II) at lower temperature. Collectively, these results expand the taxonomic and ecological distribution of mer-encoded functionalities, and suggest that selection for Hg(II) and MeHg detoxification is dependent not only on the availability and type of mercury compounds in the environment but also the physiological potential of the microbes who inhabit these environments. The expanded diversity and environmental distribution of MerAB identify new targets to prioritize for future research.

ASSESSING MERCURY POLLUTION USING BLACK STORK EGGSHELLS

Female birds whose bodies contain environmental contaminants produce eggs with shells that are likewise contaminated, making bird eggshells appropriate indicators for monitoring environmental toxins. Common contaminants include organic mercury compounds, especially methylmercury, which are known to bioaccumulate and biomagnify in the food chain. Black storks (Ciconia nigra) predominantly consume fish and are thus at risk for high mercury intake. In this study, we used eggshells of black storks as a proxy to reconstruct the concentration levels and distribution of mercury, a well-known toxic element, in various parts of Latvia. Preliminary analyses have shown that deposition levels of mercury vary in different parts of the eggshell. Specifically, the shell and shell membrane differ in their level of mercury contamination by an average factor of nine; therefore, we measured the mercury content in these components separately whenever possible. We analysed 34 eggshell samples from nesting sites in Latvia using an atomic absorption spectrometer with Zeeman correction Lumex RA-915M and its attachment for pyrolytic combustion. We found that mercury concentrations varied from 5 to 22 ng/g in eggshells and from 42 to 293 ng/g in shell membranes. We discuss possible contamination sources and reasons behind this disparity.

Relativistic Hirshfeld atom refinement of an organo-gold(I) compound

The main goal of this study is the validation of relativistic Hirshfeld atom refinement (HAR) as implemented in Tonto for high-resolution X-ray diffraction datasets of an organo-gold(I) compound. The influence of the relativistic effects on statistical parameters, geometries and electron density properties was analyzed and compared with the influence of electron correlation and anharmonic atomic motions. Recent work in this field has indicated the importance of relativistic effects in the static electron density distribution of organo-mercury compounds. This study confirms that differences in electron density due to relativistic effects are also of significant magnitude for organo-gold compounds. Relativistic effects dominate not only the core region of the gold atom, but also influence the electron density in the valence and bonding region, which has measurable consequences for the HAR refinement model parameters. To study the effects of anharmonic motion on the electron density distribution, dynamic electron density difference maps were constructed. Unlike relativistic and electron correlation effects, the effects of anharmonic nuclear motion are mostly observed in the core area of the gold atom.

Atmospheric chemistry of oxygenated mercury-containing compounds

<p>Mercury is transported globally through the atmosphere as atomic mercury, but mostly it is transferred from the atmosphere to ecosystems in the form of Hg(II) compounds. As a result, scientists are increasingly focused on oxidation-reduction chemistry of mercury in the atmosphere. At present, little is known about the interaction of mercury compounds with environmental surfaces, which commonly possess adsorbed water.</p><p>As a first step towards understanding these interactions, we have theoretically studied the reaction of BrHgO• + CO → BrHg• + CO<sub>2</sub>, which constitutes a potentially important mercury reduction reaction in the atmosphere. We characterized the potential energy surface with CCSD(T)/CBS energies (with corrections for relativistic effects) at MP2 geometries. Master Equation simulations were used to reveal the factors controlling the overall rate constant.</p><p>In a second step and for the first time, the monohydration of several oxygenated mercury-containing compounds (BrHgO, BrHgOH, BrHgOOH, BrHgNO<sub>2</sub> and its isomers, and HgOH) with one water molecule has been theoretically studied using the ωB97X-D/aug‐cc‐pVTZ level of theory. The thermodynamic properties of the hydration reactions have been calculated using DFT geometries with energies with coupled-cluster calculations DK-CCSD(T) and the ANO‐RCC‐Large basis sets. Standard reaction enthalpy and standard Gibbs free reaction energy were computed. The temperature dependences of Δ<sub>r</sub>G°(T) were evaluated for all studied aggregates over the temperature range 200 - 400 K. For the first time, the monohydration processes have been studied to elucidate the role of hydrating water molecules. Atmospheric implications have been discussed.</p>