خيارات البحث
النتائج 3001 - 3010 من 4,896
Distribution and emission characteristics of filterable and condensable particulate matter before and after a low-low temperature electrostatic precipitator
2019
Li, Xiaodong | Zhou, Chenyang | Li, Jingwei | Lu, Shengyong | Yan, Jianhua
The low-low temperature electrostatic precipitator (LLT-ESP), a combination of a traditional temperature electrostatic precipitator (ESP) and a non-leakage media gas-gas exchange (MGGH), could reduce the inlet flue gas temperature below the dew point and improved the performance of the ESP. Particulate matter (PM) from the stationary sources contains filterable particulate matter (FPM) and condensable particulate matter (CPM). In this study, coal with a high ash content (coal-HA) was burned, and the emission characteristics and removal efficiencies of the particulate matter in an LLT-ESP were investigated. The standards used to test filterable and condensable PM were ISO standard 23210-2009 and U.S. EPA Method 202, respectively. The LLT-ESP was efficient in removing filterable PM, with a total filterable PM removal efficiency as high as 99.6%. The removal efficiency of filterable PM increased with increasing particulate size and decreasing imported flue gas temperature. The LLT-ESP also provided excellent removal of condensable PM with a condensable PM removal efficiency exceeding 77%. Upstream of the LLT-ESP, the concentrations of filterable PM were much higher than those of condensable PM. Downstream of the LLT-ESP, the relationship between the quantities of condensable and filterable PM reversed. To reduce the emissions of PM from coal-fired power plants, more attention should be paid to controlling condensable PM. The temperature of the flue gas upstream of the LLT-ESP played an important role in eliminating condensable PM. At lower imported flue gas temperature operation conditions, the removal efficiency of the LLT-ESP for the condensable PM and the escaping mass concentration of condensable PM increased. Among the organic fraction of the condensable PM, hydrocarbons and esters were dominant. Meanwhile, SO₄²⁻ was the primary component, followed by Cl⁻ in anions. Na⁺, Ca²⁺, and Fe³⁺ were the main components in metal ions. Particles with diameters ≥ 10 μm, which contained most of the Si and Al, were dominant in the fly ash collected from sections 1 and 2 of the LLT-ESP. The main particles in sections 3 and 4 were PM₁₀, which contained the highest concentrations of Ca and Fe.
اظهر المزيد [+] اقل [-]Metals and emerging contaminants in groundwater and human health risk assessment
2019
Francisco, Luiza Flavia Veiga | do Amaral Crispim, Bruno | Spósito, Juliana Caroline Vivian | Solórzano, Julio César Jut | Maran, Nayara Halimy | Kummrow, Fábio | do Nascimento, Valter Aragão | Montagner, Cassiana Carolina | De Oliveira, Kelly Mari Pires | Barufatti, Alexeia
Groundwaters are normally consumed without previous treatment and therefore the monitoring of contaminants in order to guarantee its safety is necessary. Thus, we aimed to evaluate the groundwater contamination by metals and emerging contaminants, seeking to understand the relationship between their presence in the groundwater and the use and land cover profile of Itaporã and Caarapó. In addition, the contaminant concentrations observed were compared with maximum permitted values (MPV) and/or with calculated water quality criteria (WQC) for human consumption to investigate possible human health risks due to the groundwater intake. We collected one groundwater sample from each of the 12 wells located in Itaporã and 11 wells located in Caarapó. The metals were analyzed using ICP-OES and the emerging contaminants using LC-MS/MS. At least 1 of the 9 metals analyzed was found in each of the samples. In 12 samples, the metal concentrations verified exceeded the MPV or calculated WQC. A risk to human health has been observed for metals Co, Mn, Cr, and Ni. The emerging contaminant concentrations found in some samples were low (ng/L) and probably did not pose health risks, but their presence in the groundwater showed the impact of agriculture and the inadequate disposal of domestic sewage in the wells of both cities.
اظهر المزيد [+] اقل [-]Performance and working mechanism of a novel anaerobic self-flotation reactor for treating wastewater with high suspended solids
2019
Zeng, Zhuo | Zheng, Ping | Zhang, Meng | Abbas, Ghulam
The new design of internal flotation components and the use of biogas were employed to develop a novel anaerobic self-flotation (ASF) reactor. Compared with the upflow anaerobic sludge blanket (UASB) reactor, the removal efficiencies of total chemical oxygen demand (COD) and suspended solids (SS) of the ASF reactor were higher than 90% under high SS concentration and high volumetric organic loading rate (OLR). The biogas flotation, sludge bed retention, and effluent washout accounted for 60%, 30%, and 10% of SS mass, respectively, proving that the biogas flotation was the main mechanism of SS removal in the ASF reactor. Extracellular polymer substance, mainly consisting of polysaccharide (PS) and protein (PN), was found to promote the SS removal by biogas flotation via the scum formation at the ratio of 294.12 g-VS/g-PS and 103.09 g-VS/g-PN. The EPS yield was determined as 2.3 ± 0.6 g-PS/g-COD and 11.5 ± 2.6 g-PN/g-COD at the OLR of 60 kg/(m³ day). The biogas production was revealed to enhance the SS removal by providing flotation driving force and by decreasing the scum density. A model was established to describe the quantitative relationship between flotation scum and OLR. This work would shed light on the high SS wastewater treatment challenge of high-rate anaerobic processes by using biogas flotation.
اظهر المزيد [+] اقل [-]A panel analysis of the sustainability of logistics industry in China: based on non-radial slacks-based method
2019
Tan, Lingling | Wu, Qunqi | Li, Qian | Cheng, Wen | Gu, Yulei
Previous studies have primarily targeted at positive causal linkages between the logistics industry and economic benefits, resulting in biased findings without the consideration of undesirable social and environmental problems. Therefore, this paper aims to develop a holistic approach to the assessment of logistics efficiency, through considering comprehensive inputs and desirable and undesirable outputs. In specific, contextualized in China, this paper comprehensively examined the spatiotemporal variations of China logistics efficiency and further investigated the impact of some exogenous factors. Results indicate that the overall logistics efficiency of China was low, but temporally showed a trend of increase. Spatially, the logistics efficiency followed the pattern of Eastern > Central > Western > Northeastern. Moreover, for the spatial interaction among adjacent provinces, there occurred high–high patterns in the Eastern, and low–low aggregation in the Western and Northeastern regions. However, along with time, the spatial interaction among adjacent provinces was weakening. For exogenous factors, level of economic development, urbanization level, utilization rate of logistics resources, and location advantage had a significant positive impact on SLE, while the effect of labor quality was not significant. Overall, this paper enriches the theoretical understandings of sustainable logistics efficiency evaluation and unbiasedly inform central and local governments with approaches to optimizing logistics efficiency.
اظهر المزيد [+] اقل [-]Correlation between pri-miR-124 (rs531564) polymorphism and congenital heart disease susceptibility in Chinese population at two different altitudes: a case-control and in silico study
2019
Yang, Wenke | Yi, Kang | Yu, Hongmiao | Ding, Yunhan | Li, Dehong | Wei, Yuping | You, Tao | Xie, Xiaodong
The development of congenital heart disease (CHD) is a complicated process and affected by multiple environmental factors, as genetic factors, and the interactions among those factors. Previous studies have shown that intrauterine hypoxic environment exposure is a risk factor of CHD, but the genetic factors involved in the process are not clear. In this study, given that tetralogy of Fallot (TOF) is a CHD with hypoxemia as its primary pathophysiological manifestation, an in silico analysis was performed to reveal the relationship between potential target genes (miR-124) with the energy metabolism in non-syndromic TOF patients’ cardiomyocyte. Furthermore, the study investigated the correlation between the primary miR-124 (rs531564) polymorphism and CHD susceptibility in 432 sporadic patients and 450 controls from two different altitude provinces (city) in China. Our study indicated that the minor C allele of rs531564 correlated with reduced risk of CHD in the low altitude city. Besides, the C allele has elevated frequency in the high-altitude group. Therefore, our findings suggest that the minor C allele of rs531564 SNP may be involved in the reduction of the risk of CHD in a way that interacts with the intrauterine hypoxic environmental factors.
اظهر المزيد [+] اقل [-]Mercury species accumulation and distribution in Typha domingensis under real field conditions (Almadén, Spain)
2019
Lominchar, Miguel Ángel | Sierra, María José | Jiménez-Moreno, María | Guirado, María | Martín-Doimeadios, Rosa Carmen Rodríguez | Millán, Rocío
Monomethylmercury (MeHg) is one of the most toxic and the most commonly occurring organomercury compound and the wetlands are one of the main areas of generation of this Hg form. Concretely, it is in the macrophyte root system where better conditions are given for its generation. However, the knowledge of absorption and subsequent distribution of mercury (Hg) and monomethylmercury in aquatic plants is still limited. Mercury mining district such as Almadén (Ciudad Real, Spain) is a natural laboratory where different rivers flow and the species Typha domingensis Pers. is a common macrophyte which grows in their riverbanks. The aim of the present work is to apply a recently developed method specially designed to analyze Hg species in plant tissues to the different fractions of T. domingensis under real field conditions and to study the accumulation and distribution of Hg species (inorganic Hg and MeHg) within the plant. The results proved that whatever Hg species has preference to be accumulated in the belowground fractions and demonstrated a high efficiency in the accumulation of MeHg.
اظهر المزيد [+] اقل [-]Examining the asymmetric effects of stock markets on Malaysia’s air pollution: a nonlinear ARDL approach
2019
Al-mulali, Usama | Solarin, Sakiru Adebola | Ozturk, Ilhan
The objective of this research is to examine the effects of stock market on air pollution in Malaysia during the period 1980–2017. To realize this aim, a nonlinear autoregressive distributed lag (ARDL) model is constructed. The short results in general revealed that the increase in stock markets will increase CO₂ emissions and its significance increases in the long run. Moreover, the decline in stock market will reduce Malaysia’s CO₂ emissions but only in the long run. From the outcomes obtained, a number of policy recommendations were provided for the investigated country.
اظهر المزيد [+] اقل [-]Assessment of short-term changes in street dust pollution with heavy metals in Lublin (E Poland)—levels, sources and risks
2019
Zgłobicki, Wojciech | Telecka, Małgorzata | Skupiński, Sebastian
Street dust forms as a result of the interaction of the atmosphere, lithosphere (pedosphere) and anthroposphere and can be regarded as an index of the condition of the environment in urban areas. At the end of the twentieth century, there was a significant decrease in heavy metal emissions in Europe, but not so intensive in Poland. The question arises: Is the intensity of pollution still decreasing? The study objective was to assess changes in street dust pollution with heavy metals in Lublin (E Poland) in the years 2013 and 2018. The sample collection sites (68) were located within streets with a varying intensity of motor traffic. Cd, Cr, Cu, Ni, Pb and Zn concentrations were determined in two dust fractions, 63–200 μm and < 63 μm, by means of an X-ray fluorescence spectrometer. The levels of street dust pollution with heavy metals, expressed both in absolute concentrations and geochemical indices, were lower in 2018 than those in 2013. The clearest decrease of concentration levels occurred within the main roads, in the 63–200 μm fraction for Cu and Cd, and in both fractions for Pb. The mean concentrations of the investigated metals, normalised to the background values, are in the following order for both fractions in 2013 and 2018: Zn > Cd > Cu > Cr > Pb > Ni. Metals form the following order for Igₑₒ and EF: Zn > Cd > Cu > Pb > Cr > Ni. This order is slightly different for the ecological risk factor: Cd > Cu > Pb > Zn > Cr > Ni. In general, street dust in Lublin does not show contamination with Cr, Ni and Pb. Igₑₒ and EF indices show moderate levels of pollution with Cu, Cd and Zn.
اظهر المزيد [+] اقل [-]The efficient removal of methylene blue from water samples using three-dimensional poly (vinyl alcohol)/starch nanofiber membrane as a green nanosorbent
2019
Murādī, Ibrāhīm | Ebrahimzadeh, Homeira | Mehrani, Zahra | Asgharinezhad, Ali Akbar
In the present study, a simple, fast, and economical method was introduced to eliminate methylene blue from dye wastewater water using a non-toxic, inexpensive, stable, and efficient adsorbent. The poly (vinyl alcohol) (PVA)/starch hydrogel nanofiber membrane with high surface area and the three-dimensional structure was fabricated in water via electrospinning strategy, and the cross-linking reaction was done by thermal treatment. The characterization of the nanofibers was carried out using Fourier-transform infrared spectrometer (FT-IR) and field-emission scanning electron microscopy (FE-SEM), and the cross-linked PVA/starch nanofiber was applied as a membrane for the removal of methylene blue (MB). The recovery of MB was performed by methanol solution containing 5% (v/v) HCl. Langmuir isotherm model successfully described the adsorption of MB on nanosorbent, and the maximum adsorption capacity (qₘ) was 400 mg g⁻¹. Also, the kinetic of adsorption was well fitted by the pseudo-second-order model. In this study, because of the high stability of fabricated membrane (based on the tensile testing), it can be used as a filter for the fast separation of MB (cationic dye) and methyl orange (MO, anionic dye). Graphical abstract
اظهر المزيد [+] اقل [-]Configurational conditions of national carbon intensity: a fuzzy set analysis of 136 countries
2019
Mao, Yimin
Drawing on the insights from the literature in environmental economics and politics, this study examines the configurational conditions of national carbon intensity by constructing a new analytical framework integrating six factors, i.e. population, affluence, industrial structure, energy intensity, urbanization rate and democracy. A fuzzy set analysis of 136 countries shows that national carbon intensity is not determined by any single factor but rather by the combined effects of multiple factors. There are two configurational pathways to low-carbon development while four pathways to high-carbon development, each with its own configuration. Low-carbon development occurs most often in those affluent, highly urbanized and democratic countries with low intensity of energy use, while high-carbon development is most likely in those small, poor countries with high intensity of energy use. This study also shows that the role of particular factor should be understood in the context as its combinations with different sets of other factors may produce opposite effects on national carbon intensity. That is, the policy efforts concentrated on single factor may be ineffective to reduce carbon intensity. These findings permit a more contextualized and systematic understanding of the determinants of national carbon intensity.
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