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Effects of Temperature on the Transport of Suspended Particles Through Sand Layer During Groundwater Recharge Texto completo
2019
Cui, Xianze | Fan, Yong | Wang, Hongxing | Huang, Shibing
This paper presents an experimental study of suspended particle transport through sand layer using a new self-developed sand layer transportation-deposition testing system, and the study aims to identify the effects of temperature on the transport of suspended particles through porous medium. Four typical temperatures (5 °C, 15 °C, 25 °C, and 35 °C) were considered in our study, and the experiments were conducted under four size compositions and three flow velocities (1.5 cm/s, 0.2 cm/s, and 0.04 cm/s). The tests were conducted using quartz sand as the porous medium and quartz powder as particles to monitor the change in turbidity under the different conditions. The breakthrough curves were analyzed, and the results demonstrated that changes in temperature can affect the breakthrough curves, especially at the peak. The influence is particularly significant under lower flow velocities and for smaller particles. In regard to the influence factors on the transport process, water viscosity and adsorption effect can be regarded as promoting factors, while kinetic energy of particles can be classified as constraining factors.
Mostrar más [+] Menos [-]Association between particulate matter air pollution and cardiovascular disease mortality in Lanzhou, China Texto completo
2019
Wu, Tingting | Ma, Yuan | Wu, Xuan | Bai, Ming | Peng, Yu | Cai, Weiting | Wang, Yongxiang | Zhao, Jing | Zhang, Zheng
Ambient particulate matter (PM) pollution has been linked to elevated mortality, especially from cardiovascular diseases. However, evidence on the effects of particulate matter pollution on cardiovascular mortality is still limited in Lanzhou, China. This research aimed to examine the associations of daily mean concentrations of ambient air pollutants (PM₂.₅, PMC, and PM₁₀) and cardiovascular mortality due to overall and cause-specific diseases in Lanzhou. Data representing daily cardiovascular mortality rates, meteorological factors (daily average temperature, daily average humidity, and atmospheric pressure), and air pollutants (PM₂.₅, PM₁₀, SO₂, NO₂) were collected from January 1, 2014, to December 31, 2017, in Lanzhou. A quasi-Poisson regression model combined with a distributed lag non-linear model (DLNM) was used to estimate the associations. Stratified analyses were also performed by different cause-specific diseases, including cerebrovascular disease (CD), ischemic heart disease (IHD), heart rhythm disturbances (HRD), and heart failure (HF). The results showed that elevated concentration of PM₂.₅, PMC, and PM₁₀ had different effects on mortality of different cardiovascular diseases. Only cerebrovascular disease showed a significant positive association with elevated PM₂.₅. Positive associations were identified between PMC and daily mortality rates from total cardiovascular diseases, cerebrovascular diseases, and ischemic heart diseases. Besides, increased concentration of PM₁₀ was correlated with increased death of cerebrovascular diseases and ischemic heart diseases. For cerebrovascular disease, each 10 μg/m³ increase in PM₂.₅ at lag4 was associated with increments of 1.22% (95% CI 0.11–2.35%). The largest significant effects for PMC on cardiovascular diseases and ischemic heart diseases were both observed at lag0, and a 10 μg/m³ increment in concentration of PMC was associated with 0.47% (95% CI 0.06–0.88%) and 0.85% (95% CI 0.18–1.52%) increases in cardiovascular mortality and ischemic heart diseases. In addition, it exhibited a lag effect on cerebrovascular mortality as well, which was most significant at lag6d, and an increase of 10 μg/m³ in PMC was associated with a 0.76% (95% CI 0.16–1.37%) increase in cerebrovascular mortality. The estimates of percentage change in daily mortality rates per 10 μg/m³ increase in PM₁₀ were 0.52% (95% CI 0.05–1.02%) for cerebrovascular disease at lag6 and 0.53% (95% CI 0.01–1.05%) for ischemic heart disease at lag0, respectively. Our study suggests that elevated concentration of atmospheric PM (PM₂.₅, PMC, and PM₁₀) in Lanzhou is associated with increased mortality of cardiovascular diseases and that the health effect of elevated concentration of PM₂.₅ is more significant than that of PMC and PM₁₀.
Mostrar más [+] Menos [-]Advanced SiO2 Composite Materials for Heavy Metal Removal from Wastewater Texto completo
2019
Olteanu, Marius | Baraitaru, Andreea | Panait, Ana-Maria | Dumitru, Diana | Boboc, Mădălina | Deák, György
Thermal processing of materials is used in a very broad sense to cover all sets of technologies and processes for a wide range of industrial sectors and it refers to material development with a specific application potential due to its advantages over conventional synthesis methods. By applying hydrothermal technique, the development of advanced materials has been pursued, in order to retain heavy metals from wastewater. This research refers to nanosilica-based materials, specifically mesoporous silica, for which the heavy metal retention properties were improved by using nano-TiO₂ and nano-CeO₂, considering the properties of titanium and cerium. Advanced methods have been used to characterize the materials obtained as X-ray fluorescence (XRF) and energy-dispersive X-ray spectroscopy (EDS) for chemical composition; X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for microstructural properties and BET analyser for pores and specific surface area characterization. The results showed higher retention efficiencies for the doped nanosilica.
Mostrar más [+] Menos [-]Urban wastewater treatment by using Ag/ZnO and Pt/TiO2 photocatalysts Texto completo
2019
Murcia Mesa, Julie J. | Arias Bolivar, Lizeth G | Sarmiento, Hugo Alfonso Rojas | Martínez, Elsa Giovanna Ávila | Páez, César Jaramillo | Lara, Mayra Anabel | Santos, José Antonio Navío | del Carmen Hidalgo López, María
In this study, the treatment of wastewater coming from a river highly polluted with domestic and industrial effluents was evaluated. For this purpose, series of photocatalysts obtained by ZnO and TiO₂ modification were evaluated. The effect of metal addition and Ti precursor (in the case of the titania series) over the physicochemical and photocatalytic properties of the materials obtained was also analyzed. The evaluation of the photocatalytic activity showed that semiconductor modification and precursor used in the materials synthesis are important factors influencing the physicochemical and therefore the photocatalytic properties of the materials obtained. The water samples analyzed in the present work were taken from a highly polluted river, and it was found that the effectiveness of the photocatalytic treatment increases when the reaction time increases and for both, wastewater samples and isolated Escherichia coli strain follow the next order Pt/TiO₂ << ZnO. It was also observed that biochemical and chemical demand oxygen and turbidity significantly decrease after treatment, thus indicating that photocatalysis is a non-selective technology, which can lead to recover wastewater containing different pollutants.
Mostrar más [+] Menos [-]Research on sulfur oxides and nitric oxides released from coal-fired flue gas and vehicle exhaust: a bibliometric analysis Texto completo
2019
Wang, Han | Fu, Zhenghui | Lu, Wentao | Zhao, Yi | Hao, Runlong
A bibliometric method was used to evaluate the global scientific publications about sulfur oxides and nitric oxides released by coal-fired flue gas and vehicle exhaust from 1995 to 2018 and to provide insights into the characteristics of the articles and tendencies that may exist in the publications. Performance of publications, research tendency, and hotspots were analyzed. The article number had an explosive growth in 2004 and, then, began to grow steadily. China had an absolutely advantage in publication quantities; however, America had a leading position considering publication cited times. The simultaneous removal of mercury, particulate matter, and CO₂ was a research hotpot in sulfur oxide and nitric oxide control process; oxidation, absorption, and catalytic reduction were the central control methods that had the most strength in relation with sulfur dioxide and nitric oxide. Considering the study of traditional flue gas pollutant control method (limestone-gypsum method, selective catalytic reduction, etc.) was perfection, it was speculated that adsorption by ionic liquid, electricity charging, advanced oxidation progress, and multi-pollutant removal, simultaneously, would be the new research orientation in flue gas pollutant control. One of the hot points of controlling the vehicle exhaust was the application of the “green energy” biodiesel; lots of keywords concerning human health suggested that quite a lot studies were focused on the health hazard brought by sulfur oxides and nitric oxide.
Mostrar más [+] Menos [-]Residue concentrations and profiles of PCDD/Fs in ash samples from multiple thermal industrial processes in Vietnam: Formation, emission levels, and risk assessment Texto completo
2019
Pham, Mai Thi Ngoc | Hoang, Anh Quoc | Nghiem, Xuan Truong | Tu, Binh Minh | Dao, Thi Nhung | Vu, Duc Nam
The residue concentrations and congener profiles of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) were examined in fly ash and bottom ash released from different thermal industrial processes in Vietnam. PCDD/F concentrations and toxic equivalents (TEQs) in the ash samples varied greatly and decreased in the following order: steel making > aluminum recycling > medical waste incinerator > boilers > municipal waste incinerator > tin production > brick production > coal-fired power plant. Both the precursor and de novo synthesis were estimated as possible formation mechanisms of dioxins in the ash, but the latter pathway was more prevalent. The highest emission factors were estimated for the ash released from some steel-making plants, aluminum-recycling facilities, and a medical waste incinerator. The emission factors of PCDD/Fs in ash released from some steel plants of this study were two to six times higher than the UNEP Toolkit default value. The annual emission amount of ash-bound dioxins produced by 15 facilities in our study was estimated to be 26.2 to 28.4 g TEQ year⁻¹, which mainly contributed by 3 steel plants. Health risk related to the dioxin-containing ash was evaluated for workers at the studied facilities, indicating acceptable risk levels for almost all individuals. More comprehensive studies on the occurrence and impacts of dioxins in waste streams from incineration and industrial processes and receiving environments should be conducted, in order to promote effective waste management and health protection scheme for dioxins and related compounds in this rapidly industrializing country.
Mostrar más [+] Menos [-]Study on new artificial floating island removing pollutants Texto completo
2019
Kong, Lingwei | Wang, Lu | Wang, Qirui | Mei, Rongwu | Yang, Yifan
In this study, two types of artificial floating islands (AFIs), group A (consists of 1# and 2# traditional AFIs with plant and soil) and group B (consists of 4# and 5# new-type AFIs with plant, substrate, and with luffa sponge and corncob hanging at the bottom), were constructed, respectively. The removal effects and degradation mechanisms of luffa sponge and corncob in group B were compared and investigated. Plant height, root growth, and packing degradation of the two types of AFIs were studied. Temperature, dissolved oxygen (DO), and pH on the decontamination effects of AFI were discussed. The results showed that group A and group B AFIs showed great significant differences in removal of CODCᵣ, TN, NO₃⁻−N, NH₄⁺−N, and TP (p < 0.05). The TP removal of group B was 92.8 ± 0.6%, and the TN removal and NO₃⁻−N removal were significantly higher than that of group A, which was 90.3 ± 0.8% and 96.0 ± 2.2%, respectively; The addition of luffa sponge and corncob could enhance the biodegradability of sewage and the nitrogen and phosphorus removal efficiency of group B. The plant growth height of group B planted with Lythrum salicaria was 2.36 times higher than that of group A. The effect of temperature on TP was significantly greater than that of TN, and both groups of AFIs presented continuous improvement capacities of TN and TP removal when the temperature was above 15 °C. Group B was observed with a lower pH range of 6.69~7.12, which was more suitable for denitrification than group A. The release of carbon source of 5#-corncob AFI was 2.51 times higher than 4#-luffa sponge AFI at the end of the experiment.
Mostrar más [+] Menos [-]Green vehicle adoption behavior among low-income households: evidence from coastal Malaysia Texto completo
2019
Al Mamun, Abdullah | Masud, Muhammad Mehedi | Fazal, Syed Ali | Muniady, Rajennd
In an attempt to mitigate the effects of extreme natural events caused by greenhouse gases (GHGs), a significant number of researchers and environmentalists have repeatedly stressed the importance of implementing protective measures, including the promotion of green consumption. This study examined the elements that motivated the willingness and the practice of green behavior (GB) among low-income households in coastal Peninsular Malaysia. To meet the research objectives, this study adopted the survey questionnaire method to collect data from 380 low-income households. The findings revealed that self-efficacy (SE) and environmental concerns (EC) have statistically significant effects on the attitude toward green products (ATT), while subjective norms (SN) and perceived behavioral control (PBC) have influence on the intention of green vehicles. Eventually, the study discovered the effects of the intention to adopt green vehicle on green vehicle adoption behavior. Hence, the findings of this study provide new insights for policymakers in Malaysia to place more emphasis on improving consumer attitudes, social standards, and PBC, which will ultimately contribute to the adoption of environment-friendly vehicles. In addition, car manufacturers should support this program by designing products and options that would encourage those in the low-income group to replace their conventional vehicles with green alternatives in Malaysia.
Mostrar más [+] Menos [-]Virulence, antimicrobial and heavy metal tolerance, and genetic diversity of Vibrio cholerae recovered from commonly consumed freshwater fish Texto completo
2019
Xu, Mengjie | Wu, Jinrong | Chen, Lanming
Vibrio cholerae is a leading waterborne pathogen worldwide. Continuous monitoring of V. cholerae contamination in aquatic products and identification of risk factors are crucial for assuring food safety. In this study, we determined the virulence, antimicrobial susceptibility, heavy metal tolerance, and genetic diversity of 400 V. cholerae isolates recovered from commonly consumed freshwater fish (Aristichthys nobilis, Carassius auratus, Ctenopharyngodon idellus, and Parabramis pekinensis) collected in July and August of 2017 in Shanghai, China. V. cholerae has not been previously detected in the half of these fish species. The results revealed an extremely low occurrence of pathogenic V. cholerae carrying the major virulence genes ctxAB (0.0%), tcpA (0.0%), ace (0.0%), and zot (0.0%). However, high incidence of virulence-associated genes was observed, including the RTX toxin gene cluster (rtxA-D) (83.0–97.0%), hlyA (87.8%), hapA (95.0%), and tlh (76.0%). Meanwhile, high percentages of resistance to antimicrobial agents streptomycin (65.3%), ampicillin (44.5%), and rifampicin (24.0%) were observed. Approximately 30.5% of the isolates displayed multidrug resistant (MDR) phenotypes with 42 resistance profiles, which were significantly different among the four fish species (MARI, P = 0.001). Additionally, tolerance of isolates to heavy metals Hg²⁺ (49.3%), Zn²⁺ (30.3%), and Pb²⁺ (12.0%) was observed. The enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR)-based fingerprinting of the 400 V. cholerae isolates revealed 328 ERIC-genotypes, which demonstrated a large degree of genomic variation among the isolates. Overall, the results of this study support the need for food safety risk assessment of aquatic products.
Mostrar más [+] Menos [-]Environmental behavior of paclobutrazol in soil and its toxicity on potato and taro plants Texto completo
2019
Jiang, Xiulan | Wang, Yanan | Xie, Hui | Li, Ruiqi | Wei, Jinling | Liu, Yan
The environmental behavior of paclobutrazol in soil and its toxicity were studied by field investigation and an outdoor pot experiment, and the residue of paclobutrazol was detected by gas chromatography–mass spectrometry. Field investigation has found that the residual paclobutrazol in the former succession crop could severely inhibit the growth of succeeding crops of potato; with migration and transformation of residual paclobutrazol in the soil, the stems of potato were thickened with residual amount of 1.23 mg kg⁻¹, the growth was slow, and the height of potato in soil with residual amount of 1.34 mg kg⁻¹ and the control was significantly different. The degradation dynamics of paclobutrazol fits with the first-order degradation kinetics, although T₁/₂ of paclobutrazol of the taro planting soil was 30.14–46.21 days and the residual paclobutrazol remained detectable even on day 120 after application. Taro leaves were sensitive to the stress of paclobutrazol pollution; the taro leaf thickness increased, the leaf area decreased, the chlorophyll content per area unit of taro leaf showed an obvious increased trend, and SOD and CAT activities and MDA and proline content increased significantly. Paclobutrazol promoted the tillering of taro, and the taro seedlings were dwarfed by 58.01, 63.27, and 75.88% at different concentrations. It indicated that taro had strong stress response ability under paclobutrazol pollution.
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