خيارات البحث
النتائج 3081 - 3090 من 3,208
Spatial distribution and source apportionment of atmospheric dust fall at Beijing during spring of 2008–2009 النص الكامل
2015
Wang, Rende | Zou, Xueyong | Cheng, Hong | Wu, Xiaoxu | Zhang, Chunlai | Kang, Liqiang
Beijing is a megacity, where atmospheric dust fall amount is great, and its resultant air pollution is serious. So, analyzing the chemical elements in atmospheric dust fall and revealing its various sources can provide a scientific basis for taking effective measures to improve atmospheric environmental quality. In this paper, we investigated the spatial and temporal distribution of dust fall in Beijing, based on the dust samples collected in the spring of 2008 and 2009 at 18 observation sites laid out in Beijing and then analyzed the sources of atmospheric dust fall based on the test of samples, adopting enrichment factor and factor analysis methods. Our results found that the dust fall quantity in the observation periods was respectively 33.6230 t km⁻²and 28.7130 t km⁻²; the dust fall quantity varied significantly in different months in the spring, but the variation trend was similar at the sites. There were two centers of large quantity in Beijing; one was in the southwest of downtown, and the other was in the northeast of downtown. The spatial distribution of dust fall generally showed a structural feature of three loops; the northwestern mountainous area was a small quantity belt; the plain area around the downtown was a large quantity belt, and the central downtown was a center of small quantity. Soil dust, construction dust, coal dust, and vehicle exhaust were the four major sources of dust fall in spring of Beijing, respectively, accounting for 38.50, 22.25, 14.06, and 20.82 % of the total dust fall quantity.
اظهر المزيد [+] اقل [-]Modeling of trihalomethanes (THMs) in drinking water supplies: a case study of eastern part of India النص الكامل
2015
Kumari, Minashree | Gupta, S. K.
This study aimed at developing a model for predicting the formation of trihalomethanes (THMs) in drinking water supplies. Monitoring of THMs in five major water treatment plants situated in the Eastern part of India revealed high concentration of THMs (231–484 μg l⁻¹). Chloroform was predominant, contributing 87–98.9 % to total THMs. Seasonal variation in THMs levels dictated that the concentration were higher in autumn than other seasons. Linear regression analysis of data indicated that TOC is the major organic precursors for THMs formation followed by DOC and UV₂₅₄. Linear and non-linear predictive models were developed using SPSS software version 16.0. Validation results indicated that there is no significant difference in the predictive and observed values of THMs. Linear model performed better than non-linear one in terms of percentage prediction errors. The model developed were site specific and the predictive capabilities in the distribution systems vary with different environmental conditions.
اظهر المزيد [+] اقل [-]Phthalate esters contamination in soils and vegetables of plastic film greenhouses of suburb Nanjing, China and the potential human health risk النص الكامل
2015
Ma, Ting Ting | Wu, Long Hua | Chen, Like | Zhang, Hai Bo | Teng, Ying | Luo, Yong Ming
The contamination of phthalate esters (PAEs) has become a potential threat to the environment and human health because they could be easily released as plasticizers from the daily supply products, especially in polyethylene films. Concentration levels of total six PAEs, nominated as priority pollutants by the US Environmental Protection Agency (USEPA), were investigated in soils and vegetables from four greenhouse areas in suburbs of Nanjing, East China. Total PAEs concentration ranged from 930 ± 840 to 2 450 ± 710 μg kg⁻¹ (dry weight (DW)) in soil and from 790 ± 630 to 3 010 ± 2 130 μg kg⁻¹ in vegetables. Higher concentrations of PAEs were found in soils except in Suo Shi (SS) area and in vegetables, especially in potherb mustard and purple tsai-tai samples. Risk assessment mainly based on the exposures of soil ingestion and daily vegetable intake indicated that bis(2-ethylhexyl) phthalate (DEHP) in the samples from Gu Li (GL) and Hu Shu (HS) exhibited the highest hazard to children less than 6-year old. Therefore, the human health risk of the PAEs contamination in soils and vegetables should greatly be of a concern, especially for their environmental estrogen analog effects.
اظهر المزيد [+] اقل [-]Biological activity of the metal-rich post-flotation tailings at an abandoned mine tailings pond (four decades after experimental afforestation) النص الكامل
2015
Feketeová, Zuzana | Hulejová Sládkovičová, Veronika | Mangová, Barbara | Šimkovic, Ivan
In the spring 2012, post-flotation tailings of the inactive impoundment Lintich (Slovakia) were sampled. In the impoundment sediment and also in its surrounding, we detected concentration of Pb, Zn, Cd, Cu, and Ba exceeding limiting values. We detected low values of the microbial biomass carbon and microbial activity in the impoundment sediment (LiS) and its dam (DAM) along with potential respiration stayed relatively low and therefore also substrate availability index and metabolic quotient (qCO₂) were higher in the control sample (REF) than in the LiS and the DAM. The low qCO₂ level indicates that microbial community, despite of dangerously high levels of heavy metals in sediment, is still able to sufficiently utilize sources of available organic carbon. Anyway, we could doubt function of the metabolic index as universal indicator of environment conditions, regarding the anthropogenic substrates. We confirmed changes in composition of the mite communities along gradient dam—impoundment. The percentage of eudominant, recendent, and subrecendent species increased at the expense of dominants and subdominants, all together with decreasing diversity and equitability of the community. We identified species Chamobates borealis, Carabodes rugosior, Metabelba propexa, and Pergalumna nervosa with negative respond under the heavy metal stress. Species Adoristes ovatus was indifferent and Dissorhina sp., Hafenrefferia gilvipes, and Oppiella nova prospered under the loaded conditions. Forty years after experimental afforestation, we expect specific community of actively surviving microorganisms and Oribatida species detected in the DAM are usual in the greatly degraded habitats or on sites in the early succession.
اظهر المزيد [+] اقل [-]Sorption of sulfisoxazole onto soil—an insight into different influencing factors النص الكامل
2015
Maszkowska, Joanna | Białk-Bielińska, Anna | Mioduszewska, Katarzyna | Wagil, Marta | Kumirska, Jolanta | Stepnowski, Piotr
Although sulfonamides (SAs) are among the most commonly used veterinary drugs and their presence in the environment is well documented, knowledge of their fate and behavior in the soil environment is still limited, especially for sulfisoxazole (SSX) which is characterized by the lowest (among other SAs) pK ₐ value associated with acid-base equilibrium of sulfonamide group. Thus, this work was focused on determining the sorption potential of SSX onto natural soils differing in physicochemical properties. All the results were modeled using linear, Freundlich, Langmuir, Dubinin–Radushkevich, and Temkin sorption isotherms. The established sorption coefficients (K d) for SSX were quite low (from 0.27 to 0.95 L kg⁻¹), which indicated that this substance is highly mobile and has the potential to run off into surface waters and/or infiltrate ground water. The sorption data of SSX is well fitted to the Freundlich isotherm model (R ² > 0.968). Moreover, we assessed the sorption mechanism of these compounds in the edaphic environment with respect to organic matter (OM) content, pH, and ionic strength. To clarify the current state of knowledge, these factors were examined much more thoroughly than in previous investigations concerning other SAs. The wide range of ionic strength examined showed positive correlation of this factor and sorption of SAs. The results also yielded new insight into dependency of sorption of SAs on organic matter content in soil.
اظهر المزيد [+] اقل [-]The spatial distribution of human exposure to PCBs around a former production site in Slovakia النص الكامل
2015
Wimmerová, Soňa | Watson, Alan | Drobná, Beata | Šovčíková, Eva | Weber, Roland | Lancz, Kinga | Patayová, Henrieta | Richterová, Denisa | Koštiaková, Vladimíra | Jurečková, Dana | Závacký, Pavol | Strémy, Maximilián | Jusko, Todd A. | Palkovičová Murínová, Ľubica | Hertz-Picciotto, Irva | Trnovec, Tomáš
We evaluated concentrations of 15 PCB congeners in blood serum of 2047 adults, 431 8–9-year old children and 1134 mother-child pairs born in 2001–2003. These subjects were long-standing residents living up to 70 km (to the north) and up to 50 km (to the south) of the former Chemko Strážske PCB production facility in the Michalovce district of Slovakia. We plotted serum concentration against distance from the plant both with and without consideration of the direction of their homes from the site. The decrease in exposure with distance could be described by an exponential function which was dependent on direction and climatic parameters. By kriging we created maps depicting predicted isoconcentration contours for sex- and age-adjusted serum concentration of ∑PCBs for the same group of children, adults and mothers. The principle of our risk analysis was to relate serum concentration data, reflecting PCB body burden, using the critical concentrations established by the French Agency for Food, Environmental and Occupational Health & Safety (ANSES 2010) as thresholds below which the probability of effects on health is regarded as negligible. We conclude that 10 years ago, around 200,000 residents were at risk in this densely populated area. Exposure has since decreased but the mechanism for this has not yet been studied.
اظهر المزيد [+] اقل [-]Hybrid alkali-hydrodynamic disintegration of waste-activated sludge before two-stage anaerobic digestion process النص الكامل
2015
Grübel, Klaudiusz | Suschka, Jan
The first step of anaerobic digestion, the hydrolysis, is regarded as the rate-limiting step in the degradation of complex organic compounds, such as waste-activated sludge (WAS). The aim of lab-scale experiments was to pre-hydrolyze the sludge by means of low intensive alkaline sludge conditioning before applying hydrodynamic disintegration, as the pre-treatment procedure. Application of both processes as a hybrid disintegration sludge technology resulted in a higher organic matter release (soluble chemical oxygen demand (SCOD)) to the liquid sludge phase compared with the effects of processes conducted separately. The total SCOD after alkalization at 9 pH (pH in the range of 8.96–9.10, SCOD = 600 mg O₂/L) and after hydrodynamic (SCOD = 1450 mg O₂/L) disintegration equaled to 2050 mg/L. However, due to the synergistic effect, the obtained SCOD value amounted to 2800 mg/L, which constitutes an additional chemical oxygen demand (COD) dissolution of about 35 %. Similarly, the synergistic effect after alkalization at 10 pH was also obtained. The applied hybrid pre-hydrolysis technology resulted in a disintegration degree of 28–35 %. The experiments aimed at selection of the most appropriate procedures in terms of optimal sludge digestion results, including high organic matter degradation (removal) and high biogas production. The analyzed soft hybrid technology influenced the effectiveness of mesophilic/thermophilic anaerobic digestion in a positive way and ensured the sludge minimization. The adopted pre-treatment technology (alkalization + hydrodynamic cavitation) resulted in 22–27 % higher biogas production and 13–28 % higher biogas yield. After two stages of anaerobic digestion (mesophilic conditions (MAD) + thermophilic anaerobic digestion (TAD)), the highest total solids (TS) reduction amounted to 45.6 % and was received for the following sample at 7 days MAD + 17 days TAD. About 7 % higher TS reduction was noticed compared with the sample after 9 days MAD + 15 days TAD. Similar results were obtained for volatile solids (VS) reduction after two-stage anaerobic digestion. The highest decrease of VS was obtained when the first stage, the mesophilic digestion which lasted 7 days, was followed by thermophilic digestion for 17 days.
اظهر المزيد [+] اقل [-]Effects of simulated acid rain on microbial characteristics in a lateritic red soil النص الكامل
2015
Xu, Hua-qin | Zhang, Jia'en | Ouyang, Ying | Lin, Ling | Quan, Guo-ming | Zhao, Ben-liang | Yu, Jia-yu
A laboratory experiment was performed to examine the impact of simulated acid rain (SAR) on nutrient leaching, microbial biomass, and microbial activities in a lateritic red soil in South China. The soil column leaching experiment was conducted over a 60-day period with the following six SAR pH treatments (levels): 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0 and one control treatment (pH = 7). Compared with the control treatment, the concentrations of soil organic matter, total nitrogen, total phosphorus, total potassium, soil microbial biomass carbon (MBC), soil microbial biomass nitrogen (MBN), and average well color density (AWCD) in the Ecoplates were all significantly decreased by leaching with SAR at different pH levels. The decrease in MBC and MBN indicated that acid rain reduced the soil microbial population, while the decrease in AWCD revealed that acid rain had a negative effect on soil bacterial metabolic function. Soil basal respiration increased gradually from pH 4.0 to 7.0 but decreased dramatically from pH 2.5 to 3.0. The decrease in soil nutrient was the major reason for the change of soil microbial functions. A principal component analysis showed that the major carbon sources used by the bacteria were carbohydrates and carboxylic acids.
اظهر المزيد [+] اقل [-]Comparative study on the impact of copper sulphate and copper nitrate on the detoxification mechanisms in Typha latifolia النص الكامل
2015
Lyubenova, Lyudmila | Bipuah, Hanif | Belford, Ebenezer | Michalke, Bernhard | Winkler, Barbro | Schröder, Peter
The present study focused on cupric sulphate and cupric nitrate uptake in Typha latifolia and the impact of these copper species on the plant’s detoxification capacity. When the plants were exposed to 10, 50 and 100 μM cupric sulphate or cupric nitrate, copper accumulation in T. latifolia roots and shoots increased with rising concentration of the salts. Shoot to root ratios differed significantly depending on the form of copper supplementation, e.g. if it was added as cupric (II) sulphate or cupric (II) nitrate. After incubation with 100 μM of cupric sulphate, up to 450 mg Cu/kg fresh weight (FW) was accumulated, whereas the same concentration of cupric nitrate resulted in accumulation of 580 mg/kg FW. Furthermore, significant differences in the activity of some antioxidative enzymes in Typha roots compared to the shoots, which are essential in the plant’s reaction to cope with metal stress, were observed. The activity of peroxidase (POX) in roots was increased at intermediate concentrations (10 and 50 μM) of CuSO₄, whereas it was inhibited at the same Cu(NO₃)₂ concentrations. Ascorbate peroxidase (APOX) and dehydroascorbate reductase (DHAR) increased their enzyme activity intensely, which may be an indication for copper toxicity in T. latifolia plants. Besides, fluorodifen conjugation by glutathione S-transferases (GSTs) was increased up to sixfold, especially in roots.
اظهر المزيد [+] اقل [-]Use of dispersant in mudflat oil-contaminated sediment: behavior and effects of dispersed oil on micro- and macrobenthos النص الكامل
2015
Cuny, Philippe | Gilbert, Franck | Militon, Cécile | Stora, Georges | Bonin, Patricia | Michotey, Valérie | Guasco, Sophie | Duboscq, Karine | Cagnon, Christine | Jézéquel, Ronan | Cravo-Laureau, Cristiana | Duran, Robert
The present study aimed to examine whether the use of dispersant would be suitable for favoring the hydrocarbon degradation in coastal marine sediments without impacting negatively micro- and macrobenthic organisms. Mudflat sediments, maintained during 286 days in mesocosms designed to simulate natural conditions, were contaminated or not with Ural blend crude oil (REBCO) and treated or not with third-generation dispersant (Finasol OSR52). While the dispersant did not lead to an increase of hydrocarbon biodegradation, its use enables an attenuation of more than 55 % of the sediment concentration of total petroleum hydrocarbons (TPH). Canonical correspondence analysis (CCA) correlating T-RFLP patterns with the hydrocarbon content and bacterial abundance indicated weak differences between the different treatments except for the mesocosm treated with oil and dispersant for which a higher bacterial biomass was observed. The use of the dispersant did not significantly decrease the macrobenthic species richness or macroorganisms’ densities in uncontaminated or contaminated conditions. However, even if the structure of the macrobenthic communities was not affected, when used in combination with oil, biological sediment reworking coefficient was negatively impacted. Although the use of the dispersant may be worth considering in order to accelerate the attenuation of hydrocarbon-contaminated mudflat sediments, long-term effects on functional aspects of the benthic system such as bioturbation and bacterial activity should be carefully studied before.
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