Уточнить поиск
Результаты 141-150 из 1,535
Removal of the antiviral agent oseltamivir and its biological activity by oxidative processes
2012
Mestankova, Hana | Schirmer, Kristin | Escher, Beate I. | von Gunten, Urs | Canonica, Silvio
The antiviral agent oseltamivir acid (OA, the active metabolite of Tamiflu®) may occur at high concentrations in wastewater during pandemic influenza events. To eliminate OA and its antiviral activity from wastewater, ozonation and advanced oxidation processes were investigated. For circumneutral pH, kinetic measurements yielded second-order rate constants of 1.7 ± 0.1 × 10⁵ and 4.7 ± 0.2 × 10⁹ M⁻¹ s⁻¹ for the reaction of OA with ozone and hydroxyl radical, respectively. During the degradation of OA by both oxidants, the antiviral activity of the treated aqueous solutions was measured by inhibition of neuraminidase activity of two different viral strains. A transient, moderate (two-fold) increase in antiviral activity was observed in solutions treated up to a level of 50% OA transformation, while for higher degrees of transformation the activity corresponded to that caused exclusively by OA. OA was efficiently removed by ozonation in a wastewater treatment plant effluent, suggesting that ozonation can be applied to remove OA from wastewater.
Показать больше [+] Меньше [-]Spatial distribution and trends of total mercury in waters of the Great Lakes and connecting channels using an improved sampling technique
2012
Dove, A. | Hill, B. | Klawunn, P. | Waltho, J. | Backus, S. | McCrea, R.C.
Environment Canada recently developed a clean method suitable for sampling trace levels of metals in surface waters. The results of sampling for total mercury in the Laurentian Great Lakes between 2003 and 2009 give a unique basin-wide perspective of concentrations of this important contaminant and represent improved knowledge of mercury in the region. Results indicate that concentrations of total mercury in the offshore regions of the lakes were within a relatively narrow range from about 0.3 to 0.8 ng/L. The highest concentrations were observed in the western basin of Lake Erie and concentrations then declined towards the east. Compared to the offshore, higher levels were observed at some nearshore locations, particularly in lakes Erie and Ontario. The longer-term temporal record of mercury in Niagara River suspended sediments indicates an approximate 30% decrease in equivalent water concentrations since 1986.
Показать больше [+] Меньше [-]Influence of black carbon addition on phenanthrene dissipation and microbial community structure in soil
2012
Wang, Ping | Wang, Haizhen | Wu, Laosheng | Di, Hongjie | He, Yan | Xu, Jianming
Biodegradation processes and changes in microbial community structure were investigated in black carbon (BC) amended soils in a laboratory experiment using two soils (black soil and red soil). We applied different percentages of charcoal as BC (0%, 0.5% and 1% by weight) with 100 mg kg⁻¹ of phenanthrene. Soil samples were collected at different incubation times (0, 7, 15, 30, 60, 120 d). The amendment with BC caused a marked decrease in the dissipation (ascribed to mainly degradation and/or sequestration) of phenanthrene residues from soil. Extracted phenanthrene in black soil with 1% BC were higher, oppositely in red soil, 0.5% BC amendments were higher. There were significant changes in the PLFA pattern in phenanthrene-spiked soils with time but BC had little effect on the microbial community structure of phenanthrene-spiked soils, as indicated by principal component analysis (PCA) of the PLFA signatures.
Показать больше [+] Меньше [-]Levels, isomer profiles and chiral signatures of particle-bound hexabromocyclododecanes in ambient air around Shanghai, China
2012
Li, Huiru | Mo, Ligui | Yu, Zhiqiang | Sheng, Guoying | Fu, Jiamo
Hexabromocyclododecanes (HBCDs) have been considered candidate persistent organic pollutants, however, environmental data on their presence in China, a major world market, are limited. In this study, airborne particle-bound HBCDs in Shanghai, China were quantified with liquid chromatography–tandem mass spectrometry, and their total concentrations varied from 3.21 to 123 pg/m³. The industrial area showed about three times higher HBCD levels than the urban areas. Gamma-HBCD dominated in particle-associated HBCDs in the industrial area, while α-HBCD was the major diastereomer of the urban areas, which is quite different from the pattern of technical products. Besides α-, β- and γ-HBCDs, δ-HBCD was also detected in all samples (0.09–6.31 pg/m³), while no ɛ-HBCD was found. Airborne β- and γ-HBCDs were racemic in most studied areas due to their chiral signatures showing no significant difference from commercial mixture. Fractions of (+)-α-HBCD (0.417–0.467), however, suggested the enrichment of (−)-α-HBCD and the involvement of enantioselective bioprocesses.
Показать больше [+] Меньше [-]Using magnetic and chemical measurements to detect atmospherically-derived metal pollution in artificial soils and metal uptake in plants
2012
Sapkota, B. | Cioppa, M.T.
Quantification of potential effects of ambient atmospheric pollution on magnetic and chemical properties of soils and plants requires precise experimental studies. A controlled growth experiment assessing magnetic and chemical parameters was conducted within (controls) and outside (exposed) a greenhouse setting. Magnetic susceptibility (MS) measurements showed that while initial MS values were similar for the sample sets, the overall MS value of exposed soil was significantly greater than in controls, suggesting an additional input of Fe-containing particles. Scanning electron microscope images of the exposed soils revealed numerous angular magnetic particles and magnetic spherules typical of vehicular exhaust and combustion processes, respectively. Similarly, chemical analysis of plant roots showed that plants grown in the exposed soil had higher concentrations of Fe and heavy (toxic) metals than controls. This evidence suggests that atmospheric deposition contributed to the MS increase in exposed soils and increased metal uptake by plants grown in this soil.
Показать больше [+] Меньше [-]Surface-bound humic acid increased Pb²⁺ sorption on carbon nanotubes
2012
Lin, Daohui | Tian, Xiaoli | Li, Tingting | Zhang, Zhiyong | He, Xiao | Xing, Baoshan
Solid humic acid (HA) particles were dissolved and subsequently coated on a type of multiwalled carbon nanotubes (MWCNTs). Pb²⁺ sorption from water by the solid HA, the MWCNTs and the obtained HA-MWCNT complexes was compared. The underlying mechanism of the difference in the sorption was discussed with the data at different pHs, results of desorption in the presence and absence of Ca²⁺ and the characterizations using inductively coupled plasma mass spectrometry, X-ray energy dispersion spectroscopy and X-ray absorption fine structure spectroscopy. The effect of MWCNT-contained impurities on the sorption was also examined. It was shown that the surface-bound HA introduced oxygen-containing functional groups and negative charges on the MWCNTs, thus greatly increasing Pb²⁺ sorption on the MWCNTs. Pb²⁺ could be electrostatically attracted into outer-sphere of the electric double layer of the HA-MWCNT complexes, a fraction of which would form coordination complexes with carboxyl groups in the inner- and/or outer-sphere.
Показать больше [+] Меньше [-]Concentrations of methylmercury in invertebrates from wetlands of the Prairie Pothole Region of North America
2012
Bates, Lara M. | Hall, Britt D.
Prairie wetlands may be important sites of mercury (Hg) methylation resulting in elevated methylmercury (MeHg) concentrations in water, sediments and biota. Invertebrates are an important food resource and may act as an indicator of MeHg exposure to higher organisms. In 2007–2008, invertebrates were collected from wetland ponds in central Saskatchewan, categorized into functional feeding groups (FFGs) and analyzed for total Hg (THg) and MeHg. Methylmercury and THg concentrations in four FFGs ranged from 0.2–393.5 ng·g⁻¹ and 9.7–507.1 ng·g⁻¹, respectively. Methylmercury concentrations generally increased from gastropods with significantly lower average MeHg concentrations compared to other invertebrate taxa. Surrounding land use (agricultural, grassland and organic agricultural) may influence MeHg concentrations in invertebrates, with invertebrate MeHg concentrations being higher from organic ponds (457.5 ± 156.7 ng·g⁻¹) compared to those from grassland ponds (74.8 ± 14.6 ng·g⁻¹) and ponds on agricultural lands (32.8 ± 6.2 ng·g⁻¹).
Показать больше [+] Меньше [-]Preliminary insights into δ¹⁵N and δ¹⁸O of nitrate in natural mosses: A new application of the denitrifier method
2012
Liu, Xue-Yan | Koba, Keisuke | Takebayashi, Yu | Liu, Cong-Qiang | Fang, Yun-Ting | Yoh, Muneoki
Natural mosses have been employed as reactive and accumulative indicators of atmospheric pollutants. Using the denitrifier method, the concentration, δ¹⁵N and δ¹⁸O of moss nitrate (NO₃ ⁻) were measured to elucidate the sources of NO₃ ⁻ trapped in natural mosses. Oven drying at 55–70 °C, not lyophilization, was recommended to dry mosses for NO₃ ⁻ analyses. An investigation from urban to mountain sites in western Tokyo suggested that moss [NO₃ ⁻] can respond to NO₃ ⁻ availability in different habitats. NO₃ ⁻ in terricolous mosses showed isotopic ratios as close to those of soil NO₃ ⁻, reflecting the utilization of soil NO₃ ⁻. Isotopic signatures of NO₃ ⁻ in corticolous and epilithic mosses elucidated atmospheric NO₃ ⁻ sources and strength from the urban (vehicle NOₓ emission) to mountain area (wet-deposition NO₃ ⁻). However, mechanisms and isotopic effects of moss NO₃ ⁻ utilization must be further verified to enable the application of moss NO₃ ⁻ isotopes for source identification.
Показать больше [+] Меньше [-]Mapping critical loads of nitrogen deposition for aquatic ecosystems in the Rocky Mountains, USA
2012
Nanus, Leora | Clow, David W. | Saros, Jasmine E. | Stephens, Verlin C. | Campbell, Donald H.
Spatially explicit estimates of critical loads of nitrogen (N) deposition (CLNdₑₚ) for nutrient enrichment in aquatic ecosystems were developed for the Rocky Mountains, USA, using a geostatistical approach. The lowest CLNdₑₚ estimates (<1.5 ± 1 kg N ha⁻¹ yr⁻¹) occurred in high-elevation basins with steep slopes, sparse vegetation, and abundance of exposed bedrock and talus. These areas often correspond with areas of high N deposition (>3 kg N ha⁻¹ yr⁻¹), resulting in CLNdₑₚ exceedances ≥1.5 ± 1 kg N ha⁻¹ yr⁻¹. CLNdₑₚ and CLNdₑₚ exceedances exhibit substantial spatial variability related to basin characteristics and are highly sensitive to the NO₃ ⁻ threshold at which ecological effects are thought to occur. Based on an NO₃ ⁻ threshold of 0.5 μmol L⁻¹, N deposition exceeds CLNdₑₚ in 21 ± 8% of the study area; thus, broad areas of the Rocky Mountains may be impacted by excess N deposition, with greatest impacts at high elevations.
Показать больше [+] Меньше [-]Ecotoxicological effect characterisation of widely used organic UV filters
2012
Kaiser, D. | Sieratowicz, A. | Zielke, H. | Oetken, M. | Hollert, H. | Oehlmann, J.
Chemical UV filters are used in sun protection and personal care products in order to protect consumers from skin cancer induced by ultraviolet (UV) radiation. The present study aims to evaluate the effects of three common UV filters butyl-methoxydibenzoylmethane (B-MDM) ethylhexyl-methoxycinnamate (EHMC) and octocrylene (OCR) on aquatic organism, focussing particularly on infaunal and epibentic invertebrates (Chironomus riparius, Lumbriculus variegatus, Melanoides tuberculata and Potamopyrgus antipodarum). Due to their life habits, these organism are especially affected by lipophilic substances. Additionally, two direct sediment contact assays utilising zebra fish (Danio rerio) embryos and bacteria (Arthrobacter globiformis) were conducted. EHMC caused a toxic effect on reproduction in both snails with lowest observed effect concentrations (LOEC) of 0.4 mg/kg (Potamopyrgus antipodarum) and 10 mg/kg (Melanoides tuberculata). At high concentrations sublethal effects could be observed for D. rerio after exposure to EHMC (NOEC 100 mg/kg). B-MDM and OCR showed no effects on any of the tested organism.
Показать больше [+] Меньше [-]