خيارات البحث
النتائج 271 - 280 من 753
Coal-tar based pavement sealant toxicity to freshwater macroinvertebrates النص الكامل
2010
Bryer, Pamela J. | Scoggins, Mateo | McClintock, Nancy L.
Non-point-source pollution is a major source of ecological impairment in urban stream systems. Recent work suggests that coal-tar pavement sealants, used extensively to protect parking areas, may be contributing a large portion of the polycyclic aromatic hydrocarbon (PAH) loading seen in urban stream sediments. The hypothesis that dried coal-tar pavement sealant flake could alter the macroinvertebrate communities native to streams in Austin, TX was tested using a controlled outdoor laboratory type approach. The treatment groups were: control, low, medium, and high with total PAH concentrations (TPAH = sum of 16 EPA priority pollutant PAHs) of 0.1, 7.5, 18.4, & 300 mg/kg respectively. The low, medium, and high treatments were created via the addition of dried coal-tar pavement sealant to a sterile soil. At the start of the 24-day exposure, sediment from a minimally impacted local reference site containing a community of live sediment-dwelling benthic macroinvertebrates was added to each replicate. An exposure-dependent response was found for several stream health measures and for several individual taxa. There were community differences in abundance (P = 0.0004) and richness (P < 0.0001) between treatments in addition to specific taxa responses, displaying a clear negative relationship with the amount of coal-tar sealant flake. These results support the hypothesis that coal-tar pavement sealants contain bioavailable PAHs that may harm aquatic environments.
اظهر المزيد [+] اقل [-]Occurrence and fate of pharmaceuticals in wastewater treatment plants and rivers in Korea النص الكامل
2010
Sim, Won-Jin | Lee, Ji-Woo | Oh, Jeong-Eun
We measured 25 pharmaceuticals in ten municipal wastewater treatment plants (WWTPs), one hospital WWTP and five rivers in Korea. In the municipal WWTP influents, acetaminophen, acetylsalicylic acid and caffeine showed relatively high concentrations. The occurrence of pharmaceuticals in the wastewater seems to be influenced by production and consumption of pharmaceuticals. The hospital WWTP influent showed higher total concentrations of pharmaceuticals than the municipal WWTPs, and caffeine, ciprofloxacin and acetaminophen were dominant. In the rivers, caffeine was dominant, and the distribution of pharmaceuticals was related to the inflow of the wastewater. In the municipal WWTPs, the concentrations of acetaminophen, caffeine, acetylsalicylic acid, ibuprofen and gemfibrozil decreased by over 99%. The decrease of these pharmaceuticals occurred mainly during the biological processes. In the physico-chemical processes, the decrease of pharmaceuticals was insignificant except for some cases. In the hospital WWTP, ciprofloxacin, acetylsalicylic acid, acetaminophen and carbamazepine showed the decrease rates of over 80%.
اظهر المزيد [+] اقل [-]Homogeneity of δ15N in needles of Masson pine (Pinus massoniana L.) was altered by air pollution النص الكامل
2010
Kuang, Yuan Wen | Wen, Da Zhi | Li, Jiong | Sun, Fang Fang | Hou, Qing En | Zhou, Guo Yi | Zhang, De Qiang | Huang, Lon-bin
The present study investigated the changes of δ15N values in the tip, middle and base section (divided by the proportion to needle length) of current- and previous-year needles of Masson pine (Pinus massoniana L.) from two declining forest stands suffering from air pollution, in comparison with one healthy stand. At the healthy stand, δ15N in the three sections of both current- and previous-year needles were found evenly distributed, while at the polluted stands, δ15N values in the needles were revealed significantly different from the tip to the base sections. The results implied that the distribution of δ15N among different parts or sections in foliages was not always homogeneous and could be affected by air pollution. We suggested that the difference of δ15N values among pine needle sections should be reconsidered and should not be primarily ignored when the needle δ15N values were used to assess plant responses to air pollution.
اظهر المزيد [+] اقل [-]Organochlorine pesticides and PCBs in fish from lakes of the Tibetan Plateau and the implications النص الكامل
2010
Yang, Ruiqiang | Wang, Yawei | Li, An | Zhang, Qinghua | Jing, Chuanyong | Wang, Thanh | Wang, Pu | Li, Yingming | Jiang, Guibin
High mountains may play significant roles in the global transport of persistent organic pollutants (POPs). This work aims to investigate the levels, patterns and distribution of semi-volatile organoclorine pollutants and to improve the understanding of the long-range atmospheric transport and fate of contaminants on the Tibetan Plateau. A total of 60 fish samples were collected from eight lakes located between 2813 and 4718 m above sea level across the Plateau. Concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) including dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were measured in fish muscle. The results showed that concentrations of DDT, HCH and HCB were comparable to or lower than those found in remote mountains of Europe, Canada and US, while PCB concentrations in fish were, on average, about 4-150 times lower on Tibet than at other mountain areas. The transport and fate of contaminants in the Plateau are significantly influenced by the unique climatological and meteorological conditions, particularly by the summer Indian monsoon and winter westerly jet stream.
اظهر المزيد [+] اقل [-]Changes in susceptibility of beech (Fagus sylvatica) seedlings towards Phytophthora citricola under the influence of elevated atmospheric CO2 and nitrogen fertilization النص الكامل
2010
Fleischmann, F. | Raidl, S. | Oßwald, W.F.
The growth-differentiation balance hypothesis (GDBH) predicts changes in susceptibility of plants against herbivores with changing resource availability. In the presented study we tested the validity of the GDBH for trees infected with a root pathogen. For this purpose Fagus sylvatica seedlings grown under different atmospheric CO2- and soil nitrogen regimes were infected with the root pathogen Phytophthora citricola. High nitrogen supply increased total biomass of beech regardless of the CO2-treatment, whereas elevated CO2 enhanced biomass only in the high nitrogen treatment. The responses of beech under the different growing regimes to the Phytophthora root infection were not in line with the predictions of the GDBH. Enhanced susceptibility of beech against P. citricola was found in seedlings grown under elevated CO2 and low nitrogen supply. Fifteen months after inoculation these plants were characterized by enhanced water use efficiency, by altered root–shoot ratios, and by enhanced specific root tip densities. Susceptibility of Fagus sylvatica to the root pathogen Phytophthora citricola increased under elevated CO2
اظهر المزيد [+] اقل [-]Development of models for predicting toxicity from sediment chemistry by partial least squares-discriminant analysis and counter-propagation artificial neural networks النص الكامل
2010
Alvarez-Guerra, Manuel | Ballabio, Davide | Amigo, José Manuel | Bro, Rasmus | Viguri, Javier R.
There is strong interest in developing tools to link chemical concentrations of contaminants to the potential for observing sediment toxicity that can be used in initial screening-level sediment quality assessments. This paper presents new approaches for predicting toxicity in sediments, based on 10-day survival tests with marine amphipods, from sediment chemistry, by means of the application of Partial Least Squares-Discriminant Analysis (PLS-DA) and Counter-propagation Artificial Neural Networks (CP-ANNs) to large historical databases of chemical and toxicity data. The exploration of the internal structure of the developed models revealed inherent limitations of predicting toxicity from common chemical analyses of bulk contaminant concentrations. However, the results obtained in the validation of these models combined relevant values of non-error classification rate, sensitivity and specificity of, respectively, 76, 87 and 73% with PLS-DA and 92, 75 and 97% with CP-ANNs, outperforming the results reported for previous approaches. Models for predicting toxicity based on amphipod tests, derived using PLS-DA and CP-ANN, can be useful aids for screening-level sediment quality assessment.
اظهر المزيد [+] اقل [-]Recent levels of organochlorine pesticides and polychlorinated biphenyls in sediments of the sewer system in Hanoi, Vietnam النص الكامل
2010
Hoai, Pham Manh | Ngoc, Nguyen Thuy | Minh, Nguyen Hung | Viet, Pham Hung | Berg, Michael | Alder, Alfredo C. | Giger, W (Walter)
The occurrence, temporal trend, sources and toxicity of PCBs and organochlorine pesticides were investigated in sediment samples from the sewer system of Hanoi City, including the rivers Nhue, To Lich, Lu, Set, Kim Nguu and the Yen So Lake. In general, the concentrations of the pollutants followed the order DDTs > PCBs > HCHs (β-HCH) > HCB. However, the pollution pattern was different for the DDTs and PCBs when the sampling locations were individually evaluated. The concentrations of the DDTs, PCBs, HCHs, and HCB ranged from 4.4 to 1100, 1.3 to 384, <0.2 to 36 and <0.2 to 22 ng/g d.w., respectively. These levels are higher than at any other location in Vietnam. Compared to measurements from 1997, the DDTs, PCBs, β-HCH and HCB levels show an increasing trend with DDT/DDE ratios, indicating very recent inputs into the environment although these persistent compounds are banned in Vietnam since 1995. Organochlorine pesticides and PCBs were studied in sediments of the sewer system in Hanoi.
اظهر المزيد [+] اقل [-]Correlations of Eisenia fetida metabolic responses to extractable phenanthrene concentrations through time النص الكامل
2010
McKelvie, Jennifer R. | Wolfe, David M. | Celejewski, Magda | Simpson, Andre J. | Simpson, Myrna J.
Eisenia fetida earthworms were exposed to phenanthrene for thirty days to compare hydroxypropyl-β-cyclodextrin (HPCD) extraction of soil and 1H NMR earthworm metabolomics as indicators of bioavailability. The phenanthrene 28-d LC50 value was 750 mg/kg (632–891, 95% confidence intervals) for the peat soil tested. The initial phenanthrene concentration was 319 mg/kg, which biodegraded to 16 mg/kg within 15 days, at which time HPCD extraction suggested that phenanthrene was no longer bioavailable. Multivariate statistical analysis of 1H NMR spectra for E. fetida tissue extracts indicated that phenanthrene exposed and control earthworms differed throughout the 30 day experiment despite the low phenanthrene concentrations present after 15 days. This metabolic response was better correlated to total phenanthrene concentrations (Q2 = 0.59) than HPCD-extractable phenanthrene concentrations (Q2 = 0.46) suggesting that 1H NMR metabolomics offers considerable promise as a novel, molecular-level method to directly monitor the bioavailability of contaminants to earthworms in the environment.
اظهر المزيد [+] اقل [-]Endophytic bacteria improve phytoremediation of Ni and TCE co-contamination النص الكامل
2010
Weyens, Nele | Croes, Sarah | Dupae, Joke | Newman, Lee | Lelie, Daniel van der | Carleer, Robert | Vangronsveld, Jaco
The aim of this work was to investigate if engineered endophytes can improve phytoremediation of co-contaminations by organic pollutants and toxic metals. As a model system, yellow lupine was inoculated with the endophyte Burkholderia cepacia VM1468 possessing (a) the pTOM-Bu61 plasmid, coding for constitutive trichloroethylene (TCE) degradation, and (b) the ncc-nre Ni resistance/sequestration system. Plants were exposed to Ni and TCE and (a) Ni and TCE phytotoxicity, (b) TCE degradation and evapotranspiration, and (c) Ni concentrations in the roots and shoots were determined. Inoculation with B. cepacia VM1468 resulted in decreased Ni and TCE phytotoxicity, as measured by 30% increased root biomass and up to 50% decreased activities of enzymes involved in anti-oxidative defence in the roots. In addition, TCE evapotranspiration showed a decreasing trend and a 5 times higher Ni uptake was observed after inoculation.
اظهر المزيد [+] اقل [-]Dissolved organic carbon from sewage sludge and manure can affect estrogen sorption and mineralization in soils النص الكامل
2010
Stumpe, Britta | Marschner, Bernd
In this study, effects of sewage sludge and manure borne dissolved organic carbon (DOC) on 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) sorption and mineralization processes were investigated in three agricultural soils. Batch equilibrium techniques and equilibrium dialysis methods were used to determine sorption mechanisms between DOC, estrogens and the soil solid phase. It was found that that the presence of organic waste borne DOC decreased estrogen sorption in soils which seems to be controlled by DOC/estrogen complexes in solution and by exchange processes between organic waste derived and soil borne DOC. Incubation studies performed with 14C-estrogens showed that DOC addition decreased estrogen mineralization, probably due to reduced bioavailability of estrogens associated with DOC. This increased persistence combined with higher mobility could increase the risk of estrogen transport to ground and surface waters. The effect of DOC on estrogen sorption and mineralization is influenced by exchange processes between organic waste borne and soil derived DOC.
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