خيارات البحث
النتائج 401 - 410 من 3,208
Sources, occurrence and predicted aquatic impact of legacy and contemporary pesticides in streams النص الكامل
2015
McKnight, Ursula S. | Rasmussen, Jes J. | Kronvang, Brian | Binning, Philip J. | Bjerg, Poul L.
We couple current findings of pesticides in surface and groundwater to the history of pesticide usage, focusing on the potential contribution of legacy pesticides to the predicted ecotoxicological impact on benthic macroinvertebrates in headwater streams. Results suggest that groundwater, in addition to precipitation and surface runoff, is an important source of pesticides (particularly legacy herbicides) entering surface water. In addition to current-use active ingredients, legacy pesticides, metabolites and impurities are important for explaining the estimated total toxicity attributable to pesticides. Sediment-bound insecticides were identified as the primary source for predicted ecotoxicity. Our results support recent studies indicating that highly sorbing chemicals contribute and even drive impacts on aquatic ecosystems. They further indicate that groundwater contaminated by legacy and contemporary pesticides may impact adjoining streams. Stream observations of soluble and sediment-bound pesticides are valuable for understanding the long-term fate of pesticides in aquifers, and should be included in stream monitoring programs.
اظهر المزيد [+] اقل [-]Health risk assessment of various metal(loid)s via multiple exposure pathways on children living near a typical lead-acid battery plant, China النص الكامل
2015
Cao, Suzhen | Duan, Xiaoli | Zhao, Xiuge | Wang, Beibei | Ma, Jin | Fan, Delong | Sun, Chengye | He, Bin | Wei, Fusheng | Jiang, Guibin
Manufacture of lead-acid batteries is of widespread interest because of its emissions of heavy metals and metalloids into environment, harming environmental quality and consequently causing detrimental effects on human health. In this study, exposure pathways and health risks of children to heavy metal(loid)s (Pb, Cd, As, etc) were investigated based on field sampling and questionnaire. Pb was one of the most abundant elements in children's blood, with an elevated blood lead level of 12.45 μg dL−1. Soil/dust and food were heavily polluted by targeted metal(loid)s. Food ingestion accounted for more than 80% of the total exposure for most metal(loid)s. The non-cancer risks to children were 3–10 times higher than the acceptable level of 1, while the cancer risks were 5–200 times higher than the maximum acceptable level of 1.0 × 10−4. The study emphasized the significance of effective environmental management, particularly to ensure food security near battery facilities.
اظهر المزيد [+] اقل [-]Silver nanoparticle dissolution in the presence of ligands and of hydrogen peroxide النص الكامل
2015
Sigg, Laura | Lindauer, Ursula
Dissolution of silver nanoparticles (AgNP with carbonate or citrate coating, total Ag 1–5 μM) was examined in the presence of the ligands cysteine, chloride and fulvic acids and of the oxidant hydrogen peroxide (H2O2) at low concentrations at pH 7.5. Dissolved Ag was separated from AgNP by ultrafiltration. Cysteine in the concentration range 0.2–5 μM resulted in an initial increase of dissolved Ag within few hours. Chloride (up to 0.1 mM) and fulvic acids (up to 15 mg L−1) had little effect on the dissolution of AgNP within hours to days. In contrast, very rapid dissolution within 1–2 h of both carbonate and citrate coated AgNP was observed in the presence of H2O2 in the concentration range 0.1–10 μM, under dark or light conditions. The high efficiency of H2O2 in dissolving AgNP is likely to be of importance in toxic effects of AgNP to algae, as H2O2 is produced and released into solution by algae.
اظهر المزيد [+] اقل [-]Chemical and anatomical changes in Liquidambar styraciflua L. xylem after long term exposure to elevated CO2 النص الكامل
2015
Kim, Keonhee | Labbé, Nicole | Warren, Jeffrey M. | Elder, Thomas | Rials, Timothy G.
The anatomical and chemical characteristics of sweetgum were studied after 11 years of elevated CO2 (544 ppm, ambient at 391 ppm) exposure. Anatomically, branch xylem cells were larger for elevated CO2 trees, and the cell wall thickness was thinner. Chemically, elevated CO2 exposure did not impact the structural components of the stem wood, but non-structural components were significantly affected. Principal component analysis (PCA) was employed to detect differences between the CO2 treatments by considering numerous structural and chemical variables, as well as tree size, and data from previously published sources (i.e., root biomass, production and turnover). The PCA results indicated a clear separation between trees exposed to ambient and elevated CO2 conditions. Correlation loadings plots of the PCA revealed that stem structural components, ash, Ca, Mg, total phenolics, root biomass, production and turnover were the major responses that contribute to the separation between the elevated and ambient CO2 treated trees.
اظهر المزيد [+] اقل [-]Particulate Matter deposition on Quercus ilex leaves in an industrial city of central Italy النص الكامل
2015
A number of studies have focused on urban trees to understand their mitigation capacity of air pollution. In this study particulate matter (PM) deposition on Quercus ilex leaves was quantitatively analyzed in four districts of the City of Terni (Italy) for three periods of the year. Fine (between 0.2 and 2.5 μm) and Large (between 2.5 and 10 μm) PM fractions were analyzed. Mean PM deposition value on Quercus ilex leaves was 20.6 μg cm−2. Variations in PM deposition correlated with distance to main roads and downwind position relatively to industrial area. Epicuticular waxes were measured and related to accumulated PM. For Fine PM deposited in waxes we observed a higher value (40% of total Fine PM) than Large PM (4% of total Large PM). Results from this study allow to increase our understanding about air pollution interactions with urban vegetation and could be hopefully taken into account when guidelines for local urban green management are realized.
اظهر المزيد [+] اقل [-]Megacities and climate change – A brief overview النص الكامل
2015
Folberth, Gerd A. | Butler, Timothy M. | Collins, William J. | Rumbold, Steven T.
Megacities and climate change – A brief overview النص الكامل
2015
Folberth, Gerd A. | Butler, Timothy M. | Collins, William J. | Rumbold, Steven T.
Cities have developed into the hotspots of human economic activity. From the appearance of the first cities in the Neolithic to 21st century metropolis their impact on the environment has always been apparent. With more people living in cities than in rural environments now it becomes crucial to understand these environmental impacts. With the immergence of megacities in the 20th century and their continued growth in both, population and economic power, the environmental impact has reached the global scale. In this paper we examine megacity impacts on atmospheric composition and climate. We present basic concepts, discuss various definitions of footprints, summarize research on megacity impacts and assess the impact of megacity emissions on air quality and on the climate at the regional to global scale. The intention and ambition of this paper is to give a comprehensive but brief overview of the science with regard to megacities and the environment.
اظهر المزيد [+] اقل [-]Megacities and climate change: a brief overview النص الكامل
2015
Folberth, Gerd A. | Butler, Tim M. | Collins, W. J. | Rumbold, Steven T.
Cities have developed into the hotspots of human economic activity. From the appearance of the first cities in the Neolithic to 21st century metropolis their impact on the environment has always been apparent. With more people living in cities than in rural environments now it becomes crucial to understand these environmental impacts. With the immergence of megacities in the 20th century and their continued growth in both, population and economic power, the environmental impact has reached the global scale. In this paper we examine megacity impacts on atmospheric composition and climate. We present basic concepts, discuss various definitions of footprints, summarize research on megacity impacts and assess the impact of megacity emissions on air quality and on the climate at the regional to global scale. The intention and ambition of this paper is to give a comprehensive but brief overview of the science with regard to megacities and the environment.
اظهر المزيد [+] اقل [-]New observations on PAH pollution in old heavy industry cities in northeastern China النص الكامل
2015
Song, Ningning | Ma, Junhua | Yu, Yang | Yang, Zhifeng | Li, Yingxia
This study investigated the distinctive PAHs adsorbed on street dust near various industries in the three typical industrialized cities of Daqing (DQ), Harbin (HEB) and Jilin (JL) in northeastern China. The mean ∑PAHs concentrations in street dust of DQ, HEB and JL were 1.84, 4.87, 12.38 μg/g, respectively. Typical petroleum resource city DQ had higher proportions of low and medium ringed PAHs with higher proportions of phenanthrene (Phe), naphthalene (Nap), fluoranthene (Flua) and chrysene (Chr) at industrial sites. Typical chemical processing city JL had higher proportions of medium and high ringed PAHs with higher proportions of Flua, benz[a]anthracene (BaA), pyrene (Pyr) and benzo[a]pyrene (BaP) at industrial sites. Phe, Flua, Pyr and Chr were four major PAHs from most studied industries. The distinctive PAH emissions from the ferroalloy plant were BaA and BaP. BaA and BaP concentrations decreased by 90% at sites more than 2 km away from the ferroalloy plant.
اظهر المزيد [+] اقل [-]Slash-and-char: An ancient agricultural technique holds new promise for management of soils contaminated by Cd, Pb and Zn النص الكامل
2015
Niu, Li-qin | Jia, Pu | Li, Shao-peng | Kuang, Jia-liang | He, Xiao-xin | Zhou, Wen-hua | Liao, Bin | Shu, Wen-sheng | Li, Jin-tian
Heavy metal contamination of agricultural soils is of worldwide concern. Unfortunately, there are currently no efficient and sustainable approaches for addressing this concern. In this study, we conducted a field experiment in which an agricultural soil highly contaminated by cadmium (Cd), lead (Pb) and zinc (Zn) was treated on-site by an ancient agricultural technique, ‘slash-and-char’, that was able to convert the biomass feedstock (rice straw) into biochar in only one day. We found evidence that in comparison to the untreated soil, the treated soil was associated with decreased bioavailability of the heavy metals and increased vegetable yields. Most importantly, the treatment was also coupled with dramatic reductions in concentrations of the heavy metals in vegetables, which made it possible to produce safe crops in this highly contaminated soil. Collectively, our results support the idea that slash-and-char offers new promise for management of soils contaminated by Cd, Pb and Zn.
اظهر المزيد [+] اقل [-]Estimating dry deposition and gas/particle partition coefficients of neutral poly-/perfluoroalkyl substances in northern German coast النص الكامل
2015
Wang, Zhen | Xie, Zhiyong | Möller, Axel | Mi, Wenying | Wolschke, Hendrik | Ebinghaus, Ralf
Dry deposition fluxes of 12 neutral poly-/perfluoroalkyl substances (PFASs) were estimated at Büsum located in northern German coast, and their gas/particle partition coefficients were predicted by employing the polyparameter linear free energy relationships (PP-LFERs). The gas deposition flux, particle deposition flux and total (gas + particle) flux of the 12 PFASs during sampling periods were 1088 ± 611, 189 ± 75 and 1277 ± 627 pg/(m2 d), respectively. The gas deposition of PFASs played a key role during deposition to marine ecosystem. Sensitivity analysis showed that wind speed was the most sensitive parameter for gas deposition fluxes. Good agreements (within 1 log unit) were observed between the measured gas/particle partitioning data of PFASs and the predicted partition coefficients using PP-LFERs, indicating the model can reliably predict the gas/particle partitioning behaviors of atmospheric neutral PFASs.
اظهر المزيد [+] اقل [-]Prenatal nonylphenol exposure, oxidative and nitrative stress, and birth outcomes: A cohort study in Taiwan النص الكامل
2015
Wang, Pei-Wei | Chen, Mei-Lien | Huang, Li-Wei | Yang, Wenni | Wu, Kuen-Yuh | Huang, Yu-Fang
Data concerning the effects of prenatal exposures to nonylphenol (NP) and oxidative stress on neonatal birth outcomes from human studies are limited. A total of 146 pregnant women were studied (1) to investigate the association between prenatal NP exposure and maternal oxidative/nitrative stress biomarkers of DNA damage (8-hydroxy-2’-deoxyguanosine (8-OHdG), 8-nitroguanine (8-NO2Gua)) and lipid peroxidation (8-iso-prostaglandin F2α (8-isoPF2α), 4-hydroxy-2-nonenal-mercapturic acid (HNE-MA)) and (2) to explore the associations among oxidative stress biomarkers, NP exposure, and neonatal birth outcomes, including gestational age, birth weight, length, Ponderal index, and head and chest circumferences. NP significantly increased the 8-OHdG and 8-NO2Gua levels. All infants born to mothers with urinary 8-OHdG levels above the median exhibited a significantly shorter gestational duration (Badjusted = −4.72 days; 95% CI: −8.08 to −1.36 days). No clear association was found between NP levels and birth outcomes. Prenatal 8-OHdG levels might be a novel biomarker for monitoring fetal health related to NP exposure.
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