خيارات البحث
النتائج 2441 - 2450 من 4,033
Wash effect of atmospheric trace metals wet deposition and its source characteristic in subtropical watershed in China
2016
Gao, Yang | Hao, Zhuo | Yang, Tiantian | He, Nianpeng | Tian, Jing | Wen, Xuefa
In order to better understand air pollution in deve-loping regions, such as China, it is important to investigate the wet deposition behavior of atmospheric trace metals and its sources in the subtropical watershed. This paper studies the seasonal change of trace metal concentrations in precipitation and other potential sources in a typical subtropical watershed (Jiazhuhe watershed) located in the downstream of the Yangtze River of China. The results show that typical crustal elements (Al, Fe) and trace element (Zn) have high seasonal variation patterns and these elements have higher contents in precipitation as compared to other metals in Jiazhuhe watershed. In addition, there is no observed Pb in base flow in this study, and the concentration magnitudes of Al, Ba, Fe, Mn, Sr, and Zn in base flow are significantly higher than that of other metals. During different rainfall events, the dynamic export processes are also different for trace metals. The various trace metals dynamic export processes lead to an inconsistent mass first flush and a significant accumulative variance throughout the rainfall events. It is found that in this region, most of the trace metals in precipitation are from anthropogenic emission and marine aerosols brought by typhoon and monsoon.
اظهر المزيد [+] اقل [-]Performance of mixed algae for treatment of slaughterhouse wastewater and microbial community analysis
2016
Taşkan, Ergin
This study investigated organic matter (OM) and nutrient removal efficiency of mixed algal species from slaughterhouse wastewater (SWW) by using photo-bioreactor. For this purpose, different dilution multiples of 10, 4, and 2 were applied to the SWW, and pure wastewater was finally used for algal cultivation. OM and nutrient removal performance in an algal photo-bioreactor were severely affected by the dilution ratio. After 7 days of cultivation, the highest removal percentages of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) were 89.6, 70.2, and 96.2 %, respectively. Furthermore, the changes in eukaryotic algae and cyanobacterial species in the algal photo-bioreactors were investigated using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The results indicated that cyanobacterial species were more efficient than eukaryotic species in removing nutrients from the SWW. This study suggests that mixed algal photo-bioreactors could be used efficiently in the treatment of SWW.
اظهر المزيد [+] اقل [-]Effects of honey HMF on enzyme activities and serum biochemical parameters of Wistar rats
2016
Özkök, Duran | Silici, Sibel
Hydroxymethylfurfural (HMF) is a by-product of thermal degradation of glucose and fructose. In this study, the effects of high HMF content of honey on biochemical parameters of rats were investigated. Experiments were conducted with 40 Wistar albino male rats, each weighing 250–350 g and covered a period of 5 weeks. The animals were divided into five groups. The first group was served as control group. HMF was injected subcutaneously at a dose of 200 mg/kg rat b.w. to the animals in group 2. Group 3 was fed with honey that contains 10 mg HMF/kg honey. In group 4 and 5, there were honeys that contain significantly high HMF content due to long storage period (181 mg HMF/kg honey) and heat process (140 mg HMF/kg honey). At the end of the feeding process, biochemical blood parameters of rats were investigated. It was observed that there were no differences among the glucose, triglyceride, HDL cholesterol, uric acid, Na, GGT, and ALP parameters of the groups. On the other hand, significant differences were observed among the cholesterol, LDL, BUN, creatinine, Ca, P, Mg, K, Cl, total bilirubin, LDH, CPK, AST, ALT, total protein, and pseudocholinesterase values of the rats. The highest adverse effects were obtained from group HMF, and it was followed by groups SH (stored honey) and HH (heated honey). It can be concluded that high HMF content of honey may affect the human health adversely; thus, HMF in honey must be controlled by beekeepers.
اظهر المزيد [+] اقل [-]Effects of oxygen and weak magnetic field on Fe0/bisulfite system: performance and mechanisms
2016
Xiong, Xinmei | Gan, Jinhong | Zhan, Wei | Sun, Bo
The performance and mechanisms of 4-nitrophenol (4-NP) degradation by the Fe⁰/bisulfite system were systematically investigated for the first time. The evidences presented in this study verified that O₂ was a crucial factor that affected the mechanism of Fe⁰/bisulfite-driven 4-NP degradation. In the Fe⁰/bisulfite/O₂ system, Fe⁰ acted as a supplier of Fe²⁺ to catalyze bisulfite oxidation that induced a chain reaction to produce reactive radicals for 4-NP degradation. While under N₂ purging condition, bisulfite worked as a specified reductant that facilitated the transformation of Fe³⁺ to nascent Fe²⁺ ions, which principally accounted for the reductive removal of 4-NP. The application of a weak magnetic field (WMF) efficiently improved the removal rate of 4-NP and did not alter the mechanisms in both Fe⁰/bisulfite/O₂ and Fe⁰/bisulfite/N₂ processes. The secondary radicals, HO·, SO₄ ·⁻, and SO₅ ·⁻, were considered as the most possible active oxidants contributing to the oxidative removal of 4-NP and even partial mineralization under an oxic condition. Compared with anoxic conditions, the performance removal of 4-NP by the WMF-Fe⁰/bisulfite/O₂ system showed less pHᵢₙᵢ dependence. To facilitate the application of WMF-Fe⁰/bisulfite/O₂ technology in real practice, premagnetization of Fe⁰ was employed to combine with bisulfite/O₂ and proved to be an effective and applicable method for 4-NP removal.
اظهر المزيد [+] اقل [-]Removing heavy metals from Isfahan composting leachate by horizontal subsurface flow constructed wetland
2016
Bakhshoodeh, Reza | Alavi, Nadali | Soltani Mohammadi, Amir | Ghanavati, Hossein
Composting facility leachate usually contains high concentrations of pollutants including heavy metals that are seriously harmful to the environment and public health. The main purpose of this study was to evaluate heavy metals removal from Isfahan composting facility (ICF) leachate by a horizontal flow constructed wetland (HFCWs) system. Two horizontal systems were constructed, one planted with vetiver and the other without plant as a control. They both operated at a flow rate of 24 L/day with a 5-day hydraulic retention time (HRT). The average removal efficiencies for Cr (53 %), Cd (40 %), Ni (35 %), Pb (30 %), Zn (35 %), and Cu (40 %) in vetiver constructed wetland were significantly higher than those of the control (P < 0.05). Accumulations of heavy metals in roots were higher than shoots. Cd and Zn showed the highest and the lowest bioconcentration factor (BCF), respectively. Vetiver tolerates the extreme condition in leachate including high total dissolved solids.
اظهر المزيد [+] اقل [-]A multipoint (49 points) study of dry deposition of polycyclic aromatic hydrocarbons (PAHs) in Erzurum, Turkey by using surrogated snow surface samplers
2016
Bayraktar, Hanefi | Paloluoğlu, Cihan | Turalioğlu, Fatma S. | Gaga, Eftade O.
Dry deposition of atmospheric 18 polycyclic aromatic hydrocarbon (PAH) components was investigated in the scope of the study by using surrogate snow samplers at 49 different sampling points in and around the city center of Erzurum, Turkey. Snow was sampled twice, the first of which was taken immediately after the first fresh snow cover and placed into aluminum trays to obtain dry deposition surface while the second sample was taken from the snow cover (accumulated snow) exposed to an 8-day dry deposition period and then analyzed and extracted. All the samples taken from the samplers were extracted using solid and liquid phase extraction and analyzed through GC-MS. It was observed that at the end of an 8-day dry period, snow samples enriched 5.5 times more in PAH components than the baseline. PAH deposition was determined to be influenced mainly by coal, mixed source, traffic, diesel fuel, and petrol fuel at 43, 27, 20, 8, and 2 % of sampling points, respectively. Local polluting sources were found to be effective on the spatial distribution of dry deposition of PAH components in urban area.
اظهر المزيد [+] اقل [-]Future of lignite resources: a life cycle analysis
2016
Wang, Qingsong | Liu, Wei | Yuan, Xueliang | Zheng, Xiaoning | Zuo, Jian
Lignite is a low-quality energy source which accounts for 13 % of China’s coal reserves. It is imperative to improve the quality of lignite for large-scale utilization. To further explore and analyze the influence of various key processes on the environment and economic costs, a lignite drying and compression technology is evaluated using an integrated approach of life cycle assessment and life cycle costs. Results showed that lignite mining, direct air emissions, and electricity consumption have most significant impacts on the environment. An integrated evaluation of life cycle assessment and life cycle costs showed that the most significant contributor to the environmental impacts and economic costs was the lignite mining process. The impact of transportation and wastewater treatment process on the environment and economic costs was small enough to be ignored. Critical factors were identified for reducing the environmental and economic impacts of lignite drying and compression technology. These findings provide useful inputs for both industrial practice and policy making for exploitation, processing, and utilization of lignite resources.
اظهر المزيد [+] اقل [-]Styela plicata: a new promising bioindicator of heavy metal pollution for eastern Aegean Sea coastal waters
2016
Aydın-Önen, S.
As part of a research project, the concentrations of Cd, Cu, Pb, V, and Zn in the tissues of Styela plicata were investigated for the first time to determine if S. plicata is a suitable biological indicator for biomonitoring of heavy metals in eastern Aegean Sea coastal waters. To examine the relationships, heavy metal levels in suspended particulate matters (SPMs) and sediments were also determined. According to the results, the mean metal levels in SPM, sediments, and S. plicata samples could be arranged in the following order of abundance: Zn > Cu > Pb > V > Cd. As for heavy metal levels, significant positive correlations were noted between Cd-Pb, Cd-V, Cd-Zn, Cu-V, and Pb-V in SPM; Cd-Zn, Cu-Zn, Pb-Cd, Pb-Cu, and Pb-Zn in sediment; and Cu-Pb, Cu-Zn, and Pb-Zn in S. plicata samples. Positive relationships between these metals showed that they were originated from same sources and that they were associated with each other. Based on the findings, Zn, Cu, and Pb concentrations in suspended particulate matters, sediments, and S. plicata samples were generally represented with higher levels at stations that were used for boating, shipping, and related activities. As S. plicata is a strongest accumulator of V, the relatively low V levels observed in this study may indicate the lack of anthropogenic sources of this metal in the sampling stations. In conclusion, suspended particulate matter and sediment can be useful tool to detect the pollution status of the marine environment. Furthermore, the findings of this study highlighted that S. plicata is a promising alternative for the monitoring of heavy metal pollution for eastern Aegean Sea coasts.
اظهر المزيد [+] اقل [-]Testing the relationships between energy consumption, CO2 emissions, and economic growth in 24 African countries: a panel ARDL approach
2016
Asongu, Simplice | El Montasser, Ghassen | Toumi, Hassen
This study complements existing literature by examining the nexus between energy consumption (EC), CO₂ emissions (CE), and economic growth (GDP; gross domestic product) in 24 African countries using a panel autoregressive distributed lag (ARDL) approach. The following findings are established. First, there is a long-run relationship between EC, CE, and GDP. Second, a long-term effect from CE to GDP and EC is apparent, with reciprocal paths. Third, the error correction mechanisms are consistently stable. However, in cases of disequilibrium, only EC can be significantly adjusted to its long-run relationship. Fourth, there is a long-run causality running from GDP and CE to EC. Fifth, we find causality running from either CE or both CE and EC to GDP, and inverse causal paths are observable. Causality from EC to GDP is not strong, which supports the conservative hypothesis. Sixth, the causal direction from EC to GDP remains unobservable in the short term. By contrast, the opposite path is observable. There are also no short-run causalities from GDP, or EC, or EC, and GDP to EC. Policy implications are discussed.
اظهر المزيد [+] اقل [-]Prevalence of hypertension and its associated factors in contaminated areas of the Santos-São Vicente Estuarine region and Bertioga, Brazil: 2006-2009
2016
Ribeiro, T. S. | Carvalho, D. P. | Guimarães, M. T. | Campina, N. N. | Lobarinhas, M. R. | Lopes, A. L. J. | Cunha, M. G. | Souza, I. B. | Oliveira, V. L. F. | Martins, L. C. | Gomes, A. | Pereira, L. A. A. | Braga, A. L. F.
In Brazil, cardiovascular diseases account for 33% of deaths and the prevalence of hypertension is of approximately 22%. The Santos and São Vicente Estuarine System is the most important example of environmental degradation by chemicals from industrial sources. The aim of the present study was to evaluate the prevalence of hypertension and its associated factors in the population of this estuary in the period 2006-2009. A cross-sectional study was conducted to assess the aforementioned prevalence of hypertension in the evaluated areas, as well as risk factors for this disease in four contaminated areas located in the Estuary, and one area outside Estuary, the city of Bertioga. Associations between categorical variables were tested using Pearson's chi-square test incorporating Yates' correction, or Fisher's exact test. Single and multiple logistic regression models were applied to evaluate the risk factors for hypertension. The highest prevalence of hypertension was found in Continental São Vicente (28.4%). The risk factors for hypertension were the following: living in Center of Cubatão (OR: 1.3; IC95%: 1.0 – 1.6) and Continental São Vicente (OR: 1.4; IC95%: 1.1 – 1.8); illiterate (OR: 1.9; IC95%: 1.1 – 3.2); living in the area for more than 20 years (OR: 1.2; IC95%: 1.0 – 1.5); group of people aged 36-60 years (OR: 3.9; IC95%: 3.3 – 4.6) and who have had past occupational exposure (OR: 1.3; IC95%: 1.1 – 1.6). Results indicate that living in contaminated areas, especially for a longer time, is a risk factor for hypertension.
اظهر المزيد [+] اقل [-]