Desorption characteristics of kaolin clay contaminated with zinc from electrokinetic soil processing

A number of bench scale laboratory column tests were carried out using a newly designed and developed electrokinetic cell to investigate the fundamental behavior of zinc-spiked kaolin clay subjected to an electric field. Laboratory investigations focused on (i) zinc migration by the combined effects of electromigration and electro-osmosis and (ii) the electrically induced desorption characteristics of zinc-contaminated kaolin that occurred during processing. The correlations of the applied voltage gradient, electro-osmotic flow rate, and the development of a pH gradient were examined and evaluated. The results showed that the removal efficiency was high during the early stage of processing due to rapid desorption by electrokinetic effects in the cathode region. However, the majority of zinc migrating from the anode was precipitated due to the high pH environment in the cathode region.     

Distribution of perfluorochemicals between sera and milk from the same mothers and implications for prenatal and postnatal exposures

The levels of six perfluorocarboxylates (PFCAs), four perfloroalkylsulfonates (PFASs), and one sulfonamide were measured in paired samples of maternal serum, umbilical cord serum, and breast milk. The maternal and cord sera were strongly correlated with each other for all measured compounds (r > 0.5 and p < 0.01). Nevertheless, there was a significant difference in compound composition profile between the two sera matrices, with a more depletion of the longer chain compounds in cord serum. The transfer efficiency values from maternal to cord serum (TF_CS/MS) decreased by 70% with each increasing unit of -CF₂ chain within a PFCA group, and for perfluorooctanesulfonate (PFOS), by a half compared to perfluorooctanoate (PFOA). In contrast to the strong correlation in concentrations between the two sera matrices, the pattern of compounds in breast milk differed considerably with those in sera. Accordingly, compound- and matrix-specific transfer must be considered when assessing prenatal and postnatal exposure.     

PCB153 and p,p′-DDE disorder thyroid hormones via thyroglobulin,deiodinase 2, transthyretin,hepatic enzymes and receptors

Polychlorinated biphenyls (PCBs) and DDT are widespread environmental persistent organic pollutants that have various adverse effects on reproduction, development and endocrine function. In order to elucidate effects of PCBs and DDT on thyroid hormone homeostasis, Sprague–Dawley rats were dosed with PCB153 and p,p′-DDE intraperitoneally (ip) for five consecutive days and sacrificed within 24 h after the last dose. Results indicated that after combined exposure to PCB153 and p,p′-DDE, total thyroxine , free thyroxine, total triiodothyronine, and thyroid-stimulating hormone in serum were decreased, whereas free triiodothyronine and thyrotropin-releasing hormone were not affected. Thyroglobulin and transthyretin levels in serum were significantly reduced. mRNA expression of deiodinases 2 (D2) was also suppressed, while D1 and D3 levels were not significantly influenced after combined exposure. PCB153 and p,p′-DDE induced hepatic enzymes, UDPGTs, CYP1A1, CYP2B1, and CYP3A1 mRNA expressions being significantly elevated. Moreover, TRα1, TRβ1, and TRHr expressions in the hypothalamus displayed increasing trends after combined exposure to PCB153 and p,p′-DDE. Taken together, observed results indicate that PCB153 and p,p′-DDE could disorder thyroid hormone homeostasis via thyroglobulin, deiodinase 2, transthyretin, hepatic enzymes, and hormone receptors.     

Detection of airborne Legionella while showering using liquid impingement and fluorescent in situ hybridization (FISH)

Aerosols of water contaminated with Legionella bacteria constitute the only mode of exposure for humans. However, the prevention strategy against this pathogenic bacteria risk is managed through the survey of water contamination. No relationship linked the Legionella bacteria water concentration and their airborne abundance. Therefore, new approaches in the field of the metrological aspects of Legionella bioaerosols are required. This study was aimed at testing the main principles for bioaerosol collection (solid impaction, liquid impingement and filtration) and the in situ hybridization (FISH) method, both in laboratory and field assays, with the intention of applying such methodologies for airborne Legionella bacteria detection while showering. An aerosolization chamber was developed to generate controlled and reproducible L. pneumophila aerosols. This tool allowed the identification of the liquid impingement method as the most appropriate one for collecting airborne Legionella bacteria. The culturable fraction of airborne L. pneumophila recovered with the liquid impingement principle was 4 and 700 times higher compared to the impaction and filtration techniques, respectively. Moreover, the concentrations of airborne L. pneumophila in the impinger fluid were on average 7.0 x 10(5) FISH-cells m(-3) air with the fluorescent in situ hybridization (FISH) method versus 9.0 x 10(4) CFU m(-3) air with the culture method. These results, recorded under well-controlled conditions, were confirmed during the field experiments performed on aerosols generated by hot water showers in health institutions. This new approach may provide a more accurate characterization of aerobiocontamination by Legionella bacteria.     

Tropical surface water quality studies: Implications for the aquatic fate of N-methyl carbamate pesticides

Water quality assessment was conducted on the Ruiru River, a tributary of an important tropical river system in Kenya, to determine baseline river conditions for studies on the aquatic fate of N-methyl carbamate (NMC) pesticides. Measurements were taken at the end of the long rainy season in early June 2013. Concentrations of copper (0.21–1.51 ppm), nitrates (2.28–4.89 ppm) and phosphates (0.01–0.50 ppm) were detected at higher values than in uncontaminated waters, and attributed to surface runoff from agricultural activity in the surrounding area. Concentrations of dissolved oxygen (8–10 ppm), ammonia (0.02–0.22 ppm) and phenols (0.19–0.83 ppm) were found to lie within normal ranges. The Ruiru River was found to be slightly basic (pH 7.08–7.70) with a temperature of 17.8–21.2°C. The half-life values for hydrolysis of three NMC pesticides (carbofuran, carbaryl and propoxur) used in the area were measured under laboratory conditions, revealing that rates of decay were influenced by the electronic nature of the NMCs. The hydrolysis half-lives at pH 9 and 18°C decreased in the order carbofuran (57.8 h) > propoxur (38.5 h) > carbaryl (19.3 h). In general, a decrease in the electron density of the NMC aromatic ring increases the acidity of the N-bound proton removed in the rate-limiting step of the hydrolysis mechanism. Our results are consistent with this prediction, and the most electron-poor NMC (carbaryl) hydrolyzed fastest, while the most electron-rich NMC (carbofuran) hydrolyzed slowest. Results from this study should provide baseline data for future studies on NMC pesticide chemical fate in the Ruiru River and similar tropical water systems.     

Pesticide residues in soils, sediments, and vegetables in the Red River Delta, northern Vietnam

This study assessed pesticide residues in soils, sediments, and vegetables in the Xuan Khe and Hop Ly communes located along the Chau Giang River in the Red River Delta, northern Vietnam. Samples were collected from agricultural areas within and outside of embankments built to prevent flooding. In Xuan Khe, the soils outside of the embankment were more clayey with higher organic matter contents compared with the inside, due to selective deposition during river flooding. Many of the soils contained significant amounts of pesticides including dichlorodiphenyltrichloroethane (DDT), dicofol, isoprothiolane, and metalaxyl although their levels were below the maximum allowable concentration set by the Vietnamese government. The spectrum of DDT derivatives found suggested that the source of DDTs was not contaminated dicofol. Soils in Hop Ly resembled soils in Xuan Khe but were relatively sandy; one field showed appreciable contents of DDT derivatives. The ratios of (p,p ^′-dichlorodiphenyldichloroethylene + p,p ^′-dichlorodiphenyldichloroethane)/∑DDT in the surface and subsurface soils in Hop Ly were 0.34 and 0.57, suggesting that the DDTs originated from recent application. Pesticide residues in soils were not likely to translocate into vegetable crops, except for metalaxyl. High concentrations of cypermethrins in kohlrabi leaves could be ascribed to foliar deposition.     

Arsenic contamination in groundwater and its possible sources in Hanam, Vietnam

This study investigated the arsenic (As) level in groundwater, and the characteristics of aquifer sediment as related to the occurrence of As in groundwater in Hanam, Vietnam. The deposition and transport of As-containing substances through rivers were also examined. Arsenic concentrations in 88% of the groundwater samples exceeded the As limit for drinking water based on the WHO standards. The dominating form of arsenic was As(III). The maximum total As content in bore core sediment was found in a peat horizon of the profiles and generally, elevated levels of As were also found in other organic matter-rich horizons. Total As contents of the bore core sediments were significantly correlated with crystalline iron oxide, silt and clay contents, suggesting that As in aquifer sediment was mainly associated with iron (hydr)oxides and clay mineral. In the groundwater, As concentration showed significant correlations with the total concentrations of Fe and HCO (3)(-). Significant correlations between HCl-extractable As and non-crystalline Fe oxide, total C, N, and S were also observed in the profiles. The results support the hypothesis that under favorable reductive conditions established by the degradation of organic matter, the dissolution of iron (hydr)oxides releases adsorbed As into the groundwater. The deposition of As in the sediments from the Red River were significantly higher than that in the Chau Giang River, suggesting that the Red River is the main source of As-containing substances deposited in the study area.     

Simulation study of the Lower Cretaceous geothermal reservoir for aquifer thermal energy storage

Environmental Geochemistry and Health - The aquifer thermal energy storage (ATES) has gained attention in several countries as an installation for increasing the energy efficiency of geothermal...