Influence of HCl on oxidation of gaseous elemental mercury by dielectric barrier discharge process

The influence of HCl on the oxidation of gaseous elemental mercury (Hg0) has been investigated using a dielectric barrier discharge (DBD) plasma process, where the temperature of the plasma reactor and the composition of gas mixtures of HCl, H2O, NO, and O2 in N2 balance have been varied. We observe that Cl atoms and Cl2 molecules, created by the DBD process, play important roles in the oxidation of Hg0 to HgCl2. The addition of H2O to the gas mixture of HCl in N2 accelerates the oxidation of Hg0, although no appreciable effect of H2O alone on the oxidation of Hg0 has been observed. The increase of the reaction temperature in the presence of HCl results in the reduction of Hg0 oxidation efficiency probably due to the deterioration of the heterogeneous chemical reaction of Hg0 with chlorinated species on the reactor wall. The presence of NO shows an inhibitory effect on the oxidation of Hg0 under DBD of 16% O2 in N2, indicating that NO acts as an O and O3 scavenger. At the composition of Hg0 (280 microg m(-3)), HCl (25 ppm), NO (204 ppm), O2 (16%) and N2 (balance) and temperature 90 degrees C, we obtain the nearly complete oxidation of Hg0 at a specific energy density of 8 J l(-1). These results lead us to suggest that the DBD process can be viable for the treatment of mercury released from coal-fired power plants.     

Management status of end-of-life vehicles and characteristics of automobile shredder residues in Korea

An end-of-life vehicle (ELV) is dismantled to recover and recycle any re-usable parts, then shipped to the shredding facility for further recovery of iron with any remaining Automobile Shredder Residue (ASR) to be considered as wastes and to be disposed of by either thermal treatment or landfill. Overall ELVs management status in Korea, including recycling resulting from the dismantling processes, was surveyed using some questionnaires given to dismantlers and other available information to provide some feasible means for future treatment. The averaged recycle rate in the dismantling stage showed a value of 44% and the rest of an ELV was then compressed and transported to shredding companies to recover mainly the iron content which averaged 38.7% of the mass of a new vehicle. The non-ferrous metals such as copper, antimony, zinc and aluminum accounted for only 1.5%. The Shredder dusts (SDs) were found to be composed of light and heavy fluffs and soil/dust and amounted to 15.8% based on the mass of a new vehicle. Dumping of fluff and inorganic residues into a landfill site, however, will be restricted when new regulations are implemented to reduce the disposal amount to less than 5% of a new car as done in European countries and Japan. The detailed characteristics of SDs were investigated to provide an idea of how to treat them in order to meet a future expected enforcement.     

Human health risk assessment of explosives and heavy metals at a military gunnery range

In this research, a risk assessment was undertaken in order to develop the remediation and management strategy of a contaminated gunnery site, where a nearby flood controlling reservoir is under construction. Six chemicals, including explosives and heavy metals, posing potential risk to environmental and human health, were targeted in this study. A site-specific conceptual site model was constructed, based on effective, reasonable exposure pathways, to avoid any overestimation of the risk. Also, conservative default values were adapted to prevent underestimation of the risk when site-specific values were not available. The risks posed by the six contaminants were calculated using the API’s Decision Support System for Exposure and Risk Assessment, with several assumptions. In the crater-formed-area (Ac), the non-carcinogenic risks (i.e., HI values) of tri-nitro-toluene (TNT) and Cd were slightly larger than 1, but for RDX (Royal Demolition Explosives) was over 50. The total non-carcinogenic risk of the whole gunnery range was calculated to be 62.5, which was a significantly high value. The carcinogenicity of Cd was estimated to be about 10⁻³, while that for Pb was about 5 × 10⁻⁴, which greatly exceeded the generally acceptable carcinogenic risk level of 10⁻⁴–10⁻⁶. It was concluded from the risk assessment that there is an immediate need for remediation of both carcinogens and non-carcinogens before construction of the reservoir. However, for a more accurate risk assessment, further specific estimations of the changes in environmental conditions due to the construction of the reservoir will be required; and more over, the effects of the pollutants to the ecosystem will also need to be evaluated.     

Mercury and selenium levels in lemon sharks (Negaprion brevirostris) in relation to a harmful red tide event

Tissue levels of mercury (Hg; total, organic) and selenium (Se) were assessed in juvenile lemon sharks (Negaprion brevirostris) from Florida nearshore waters collected during a harmful algal bloom (HAB, brevetoxin) event and compared with sharks not exposed to HABs. In all sharks studied, total Hg levels in the muscle were generally present in a molar excess over Se (which may protect against Hg toxicity) and mean muscle Hg levels (0.34  $\upmu $ g/g) exceed safe human consumption guidelines. While there was generally no difference in tissue Hg and Se levels following exposure of sharks to HABs, hepatic Hg levels were significantly lower (56% reduction) in the HAB-exposed sharks compared to controls. As Hg and HABs are globally increasing in scope and magnitude, further work is warranted to assess their interactions and biotic impacts within aquatic ecosystems, especially for a species such as the lemon shark that is classified as a near-threatened species by the International Union for the Conservation of Nature.     

Maternal serum levels of dimeric inhibin A in pregnancies affected by trisomy 21 in the first trimester

Dimeric inhibin A was measured in maternal serum samples from 45 pregnancies affected by trisomy 21 and 493 samples from unaffected pregnancies at 10–14 weeks of gestation. Inhibin A levels in affected pregnancies were compared with levels of free β-hCG and PAPP-A in the same series. In the trisomy 21 group, the median multiple of the median (MoM) inhibin A was not significantly elevated (1.28 vs 1.00) with only 15.5% being above the 95th centile. In contrast, the median MoM free β-hCG was significantly increased (2.05 vs 1.00) with 36% above the 95th centile and PAPP-A was significantly reduced (0.49 vs 1.00) with 42% below the 5th centile. Inhibin A levels in the trisomy 21 group were significantly correlated with gestational age such that median levels rose from 1.04 at 11 weeks to 1.30 at 12 weeks and 1.67 at 13 weeks. These findings suggest that first trimester biochemical screening for trisomy 21, which is currently optimised using maternal serum free β-hCG and PAPP-A and fetal nuchal translucency, will not benefit from the inclusion of inhibin A. Copyright © 2001 John Wiley & Sons, Ltd.     

A survey of parabens in aquatic environments in Hanoi,Vietnam and its implications for human exposure and ecological risk

Environmental Science and Pollution Research - Seven parabens including methylparaben (MeP), ethylparaben (EtP), propylparaben (PrP), iso-propylparaben (iPrP), butylparaben (BuP), benzylparaben...     

Characterization of compaction and CBR properties of recycled concrete aggregates for unbound road base and subbase materials in Vietnam

Journal of Material Cycles and Waste Management - Mechanical properties of recycled concrete aggregates (RCA) such as compaction and California bearing ratio (CBR) are important for application as...     

Effect of biogeochemical interactions on bioaccessibility of arsenic in soils of a former smelter site in Republic of Korea

The total concentration-based regulations for soil remediation do not consider the possible changes in bioaccessibility of remaining arsenic (As) in soils due to biogeochemical interactions after remediation. This study used As-contaminated soil and pore water samples that were collected from the rice paddy and forest/farmland located in the vicinity of a former smelter site in Republic of Korea to elucidate the changes in As bioaccessibility due to biogeochemical interactions. Bioaccessibility and chemical forms of As in soils were determined by using an in vitro method and sequential extraction, respectively, and soil microbial community was evaluated. Bioaccessibility of As in the rice paddy soil samples was higher than that in the forest/farmland soil samples. This could be attributed to relatively higher dependence of bioaccessible As in the rice paddy soils on the soil concentration of iron (Fe), aluminum, or manganese, which could lead to greater changes in bioaccessible As via reductive dissolution. The strong linear relationship (R ² = 0.90, p value ≤0.001) between the pore water As and Fe concentrations, and the greater portion of bacterial species related to reductive dissolution of Fe oxides in the rice paddies can support the higher As bioaccessibility promoted by reductive dissolution. Therefore, it is necessary to consider the potential changes in the bioaccessible As due to biogeochemical interactions in remediation of As-contaminated soils, particularly when soils are likely to be reused under reductive dissolution-promoting conditions (e.g., flooded conditions).