Understanding the redox reactions and transformation rates of mercury (Hg) species in the environment is important for predicting future gaseous elemental Hg (Hg
0
) levels and assessing the impacts ...of anthropogenic Hg
0
emissions on human health. Stable Hg isotope tracers are a promising tool for estimating Hg
0
production rates; however, traditional analytical approaches for quantifying Hg
0
, such as atomic fluorescence spectroscopy or atomic absorption spectrometry, cannot differentiate between Hg isotopes, and alternative approaches, such as inductively coupled plasma mass spectrometry (ICP-MS) with a typical aqueous sample introductory system, have relatively higher detection limit of Hg. Here, we developed and evaluated a custom-made thermal desorption unit coupled directly to a triple quadrupole ICP-MS (ICP-QQQ) for the quantification of Hg
0
pre-concentrated on Au traps. The performance of the system was validated with measurements of a Hg standard gas and of Hg
0
generated from aqueous Hg standards. Using our system, we were able to detect ultra-trace amounts of Hg
0
and obtain precise Hg isotope measurements with an analytical error of ≤ 3.5%. Calibration curves with superb linearity (
r
2
> 0.999) were obtained for the Hg concentration range of 0–300 pg. The method detection limit was approximately 0.01–0.03 pg of Hg. Using the latest ICP-QQQ instrument (Agilent 8900; Agilent Technologies Ltd.) was far superior to using a previous model (Agilent 8800), with the Agilent 8900 showing approximately five times higher sensitivity than the Agilent 8800 as well as the ability to precisely and simultaneously analyze up to five Hg isotopes by time-resolved analysis.
Graphical abstract
Hg0 oxidation as well as SO2/NO removal of V2O5-WO3/TiO2-SiO2 SCR catalyst can be enhanced after metal oxide impregnation. Flue gas components showed great influences in Hg0 oxidation.
•The total ...surface area of SCR catalyst was increased after surface treatment.•V4+/V5+, Mn4+, and Cu2+ existed in VOx-, MnOx-, and CuOx-impregnated catalysts.•Hg0 oxidation and SO2/NO reduction were enhanced after surface treatment.•Potential SO2–SO3 conversion due to metal oxide impregnation should be concerned.•L–H model explained the Hg0 oxidation of VOx- and MnOx-impregnated catalysts.
This research investigated the effects of transition metal oxide impregnation on the physical/chemical properties and the multipollutant (i.e., Hg/SO2/NO) control of a V2O5-WO3/TiO2-SiO2 selective catalytic reduction (SCR) catalyst. Additional V, Mn, and Cu of 5wt% as their precursor metal hydroxides were impregnated onto the catalyst surface. The impregnated metal oxides presenting in nanoscales caused an increase in total surface area of catalysts. SEM images suggested that the raw and treated catalysts presenting as bean-shaped nanoparticles within 10–30nm. V4+/V5+, Mn4+, and Cu2+ were the major valence states presenting on the surface of VOx-, MnOx-, and CuOx-impregnated catalysts, respectively. Hg0 oxidation, SO2 removal, and NO reduction of the SCR catalyst can be enhanced after the metal oxide impregnation. VOx- and CuOx-impregnated catalysts had not only excellent Hg0 oxidation but also great NO reduction. However, the increase in SO2 removal after metal oxide impregnation, assumed to be partly caused from enhancing SO2–SO3 conversion, may be of concern considering the potential downstream corrosion. Langmuir–Hinshelwood model can successfully explain the Hg0 oxidation by VOx- and MnOx-impregnated catalysts. Overall, multipollutant emission control using surface-impregnated SCR catalysts can be practically applied at 350°C under the tested coal-combustion flue gas condition.
Mercury is a major toxic metal ranked top in the Toxic Substances List. Cinnabar, which contains mercury sulfide, has been used in Chinese traditional medicines for thousands of years as an ...ingredient in various remedies, and 40 cinnabar-containing traditional medicines are still used today. Little is known about toxicology profiles or toxicokinetics of cinnabar and cinnabar-containing traditional medicines, and the high mercury content in these Chinese medicines raises justifiably escalations of public concern. This minireview, by searching the available database of cinnabar and by comparing cinnabar with common mercurials, discusses differences in their bioavailability, disposition, and toxicity. The analysis showed that cinnabar is insoluble and poorly absorbed from the gastrointestinal tract. Absorbed mercury from cinnabar is mainly accumulated in the kidneys, resembling the disposition pattern of inorganic mercury. Heating cinnabar results in release of mercury vapor, which in turn can produce toxicity similar to inhalation of these vapors. The doses of cinnabar required to produce neurotoxicity are 1000 times higher than methyl mercury. Following long-term use of cinnabar, renal dysfunction may occur. Dimercaprol and succimer are effective chelation therapies for general mercury intoxication including cinnabar. Pharmacological studies of cinnabar suggest sedative and hypnotic effects, but the therapeutic basis of cinnabar is still not clear. In summary, cinnabar is chemically inert with a relatively low toxic potential when taken orally. In risk assessment, cinnabar is less toxic than many other forms of mercury, but the rationale for its inclusion in traditional Chinese medicines remains to be fully justified.
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