Mercury L3 and sulfur K-edge studies of Hg-bound thiacrowns and back-extracting agents used in mercury remediation

Effect of heavy metals on the stabilization of mercury(II) by DTCR in desulfurization solutions

Several heavy metals, including Cu(2+), Ni(2+), Pb(2+), and Zn(2+), were investigated in simulated desulfurization solutions to evaluate their interferences with Hg(2+) during the reaction with dithiocarbamate type chelating resin (DTCR). Appropriate DTCR dosage and the effect of pH were also explored with respect to restoration of high Hg(2+) precipitation efficiency and reduction of mercury concentrations. The experimental results suggested that increasing heavy metal concentration inhibited Hg(2+) precipitation efficiency to a considerable extent and the inhibition order of the four heavy metals was Cu(2+)>Ni(2+)>Pb(2+)>Zn(2+). However, the coordination ability was closely related to the configuration and the orbital hybridization of each metal. In the cases of Cu(2+) and Pb(2+), increased DTCR dosage was beneficial to Hg(2+) precipitation, which could lay the foundation of practical applications of DTCR dosage for industrial wastewater treatment. The enhanced Hg(2+) precipitation performance seen for increasing pH might have come from the deprotonation of sulfur atoms on the DTCR functional groups and the formation of metal hydroxides (M(OH)(2), M=Cu, Pb, Hg).

Local characteristics of cross-unit contamination around high-rise building due to wind effect: mean concentration and infection risk assessment

In this present work, the characteristics of hazardous gas dispersion and possible cross-unit contamination around a complex-shaped high-rise residential building due to wind effect are thoroughly studied using physical modeling method. Experiments were performed in a boundary layer wind tunnel for a 1:30 scale model that represented a 10-story residential building in prototype. Tracer gas, simulating exhausted room air, was continuously released from different floor levels, and its concentrations on the adjacent envelope surfaces were measured using fast flame ionization detectors. The mean concentration fields were reported and analyzed under different configurations during the experiment to consider the effects on pollutant dispersion behavior due to changes in source position and approaching wind condition, with the main emphasis on the differences between open-window and closed-window conditions. In particular, the measured concentration fields were further examined from a practical point of view, with respect to hazard assessment. Understanding these hazardous plume dispersion features is useful for employing effective intervention strategies in modern residential building environment in case of hazardous substance release. The study on this physical process is not only helpful to reduce the hazardous effect of routine release of harmful pollutant near the building, but also useful for the purpose of prevention and control of accidental infectious diseases outbreak.