خيارات البحث
النتائج 3041 - 3050 من 4,924
Solidification/stabilization of municipal solid waste incineration fly ash using uncalcined coal gangue–based alkali-activated cementitious materials
2019
Zhao, Shujie | Muhammad, Faheem | Yu, Lin | Xia, Ming | Huang, Xiao | Jiao, Binquan | Lu, Ning | Li, Dongwei
The proper disposal of municipal solid waste incineration fly ash (MSWI FA) is necessary due to the presence of hazardous metals (Cu²⁺, Zn²⁺, Pb²⁺ and Cd²⁺). The solidification/stabilization through alkali-activated cementitious materials (having aluminosilicates) is regarded as one of the best methods for its disposal. In this paper, an uncalcined coal gangue–based alkali-activated cementitious material was used to solidify the MSWI FA. The compressive strength of these cementitious materials was evaluated through different contents of alkali activators, SiO₂/Na₂O molar ratios, liquid/solid ratios and curing temperatures by utilizing a single-factor experiment. The specimens with the highest compressive strength (31.37 MPa) were used for solidification of MSWI FA. The results indicated that compressive strength decreased with the addition of MSWI FA which caused the higher leaching of heavy metals. The solidification efficiencies of Cu²⁺, Zn²⁺, Pb²⁺ and Cd²⁺ were more than 95%. In addition, leaching concentrations had not surpassed the critical limit up to 20% addition of MSWI FA in solidified samples and representing the potential application of these samples for construction and landfill purposes. Heavy metals in MSWI FA were solidified through physical encapsulation and chemical bonding which was verified by speciation analysis, X-ray diffraction, Fourier transform infrared spectrometry and scanning electron microscopy with energy dispersive spectrometry analyses.
اظهر المزيد [+] اقل [-]Experimental investigation on engine characteristics fueled with waste HDPE oil and study on NO x emission variation using thermal imager
2019
Peer, Mohamed Shameer | Peer, Mohamed Nishath
For heavy duty applications like power generation and transportation, the best option is the compression ignition engines, but the major concerns are the rising prices and environmental issues due to the rapid depleting sources of conventional fossil fuels. The present investigation is to study the performance and emission characteristics of a single cylinder four-stroke, air-cooled direct injection diesel engine runs with an alternate fuel as waste high density polyethylene plastic oil (HDPE) obtained by catalytic pyrolysis. At constant speed, test fuels have been experimented successfully to determine the engine performance such as brake thermal efficiency, brake specific energy consumption, and exhaust gas emissions such as carbon monoxide, carbon dioxide, oxides of nitrogen, and unburned hydrocarbons. The result shows that the brake thermal efficiency is lower at all load conditions when compared to diesel fuel whereas the brake specific energy consumption decreases with increase in engine load and increases with increase in waste plastic oil blend ratio. CO emission increases and NOₓ emission level decreases with enhancement in engine load whereas the NOₓ emission and CO emission augments with increase in waste plastic oil blend percentage. But in case of NOₓ emission increase in concentration of waste plastic oil with diesel leads to raise in emission level. By using thermal imager, the link between in-cylinder temperature and NOₓ emission has been fixed. With the help of this course of action, it has been observed that in-cylinder temperature plays the major role in NOₓ concentration.
اظهر المزيد [+] اقل [-]Incorporating a non-reactive heavy metal simulation module into SWAT model and its application in the Athabasca oil sands region
2019
Du, Xinzhong | Shrestha, Narayan Kumar | Wang, Juyne
Heavy metal contaminations in an aquatic environment is a serious issue since the exposure to toxic metals can cause a variety of public health problems. A watershed-scale model is a useful tool for predicting and assessing heavy metal fate and transport in both terrestrial and aquatic environments. In this study, we developed a simulation module for non-reactive heavy metals and incorporated it into the widely used Soil Water Assessment Tool (SWAT) model. The simulated processes in the developed model include heavy metal deposition, partitioning in soil and water, and transport by different pathways in both terrestrial and aquatic environments. Three-phase partitioning processes were considered in the module by simulating heavy metals portioning to dissolved organic carbon in the soil and stream. This developed module was used for watershed-scale simulation of heavy metal processes in the Muskeg River watershed (MRW) of the Athabasca oil sands region in western Canada for the first time. The daily streamflow and sediment load from 2015 to 2017 were first calibrated and validated. Subsequently, the daily Lead and Copper loads at the outlet station were used for heavy metal calibration and validation. The performances for the daily heavy metal loads simulation during the whole simulation period can be considered as “satisfactory” based on the recommended model performance criteria with the Nash-Sutcliffe efficiency as 0.41 and 0.71 for Pb and Cu loads, respectively. The simulation results indicate that the spring and summer are hot moments for heavy metal transport and the snowmelt in spring and rainfall runoff events in summer are the main driving forces for the metal transport in the MRW. We believe the developed model can be a useful tool for simulating the fate and transport of non-reative heavy metals at watershed scale and further used to assess management scenarios for mitigating heavy metal pollution in the Athabasca oil sands region.
اظهر المزيد [+] اقل [-]A study of “cancer villages” in Jiangsu Province of China
2019
Cheng, Yuanyuan | Nathanail, P. (Paul)
China’s economic boom has created many environmental and health challenges, including so-called cancer villages. This study, the first to use the lens of “cancer villages” at provincial level, examines the correlation between changes in Jiangsu cancer villages and economic and environmental quality indicators identified as being relevant, and hence to highlight environmental issues that should be mitigated to protect public health. Since 2001, 25 cancer villages have been reported in Jiangsu. The distribution pattern of these villages is of a cluster whose mean centre had moved from Suzhou city in 2001 to Taizhou in 2006 and 2011. By applying the buffer analysis tool of ArcGIS10.2.2 using 3-km and 5-km radius buffer, to examine the relationship between these cancer villages and the surrounding rivers, it was revealed that 76% of the villages fall within the 3-km buffer zone, and 88% are within the 5-km buffer zone. A fairly strong correlation between the cancer villages and annual GDP, as well as pollutant discharge, was found, with correlation coefficients of 0.94 for Jiangsu, 0.89 for Northern Jiangsu, 0.93 for Central Jiangsu, 0.83 for Southern Jiangsu and 0.64 for city level. The change of newly added cancer villages is significantly influenced by the discharge of sewage water (raising COD) and SO₂, and the peak of newly added cancer villages, as well as discharge of COD and SO₂ all occurred in 2005. For four cities, the total sewage water discharge and SO₂ emissions are consistent with the order of the distribution density of the villages. The phenomenon of cancer villages in China will gradually be resolved as the government takes effective measures to tackle environmental issues coupled with people’s increasing environmental and health awareness.
اظهر المزيد [+] اقل [-]Horizontal distribution of pelagic crustacean zooplankton biomass and body size in contrasting habitat types in Lake Poyang, China
2019
Liu, Baogui | Liu, Jinfu | Jeppesen, Erik | Chen, Yuwei | Liu, Xia | Zhang, Wei
To evaluate the possible effects of habitat type on crustacean plankton (hereafter zooplankton) biomass and body size, a 5-year study (2011 to 2015) was conducted during wet seasons in three habitats in Lake Poyang, China. The lacustrine habitat with the most stable hydrologic regime had the highest zooplankton biomass coinciding with the highest phytoplankton biomass. The riverine habitat with the lowest Secchi depth overall had the largest zooplankton body size, but high zooplankton biomass only in high water level years. The seasonally inundated floodplain habitats had the lowest zooplankton biomass and the smallest individual body size, coinciding with the lowest phytoplankton biomass and the highest predation pressure, the latter indicated by a low zooplankton: phytoplankton biomass ratio (ZB:PB). Multiple linear regression analyses indicated that pelagic zooplankton assemblages were primarily influenced by phytoplankton biomass in lacustrine habitat, by advection and turbidity in riverine regions, and by predation pressure in seasonally inundated floodplain region. We conclude that the importance of bottom-up and top-down effects on zooplankton biomass and body size varied with habitat type in Lake Poyang.
اظهر المزيد [+] اقل [-]Urinary bisphenol A (BPA) concentrations and exposure predictors among pregnant women in the Laizhou Wan Birth Cohort (LWBC), China
2019
Zhao, Shasha | Wang, Caifeng | Pan, Rui | Shi, Rong | Wang, Weiye | Tian, Ying
Although BPA use is widespread and often detectable in humans, little is known about its exposure levels and potential exposure predictors in pregnant women in China. We investigated the BPA exposure levels in pregnant women and its health implications and potential exposure predictors. Urinary BPA levels were measured for 506 pregnant women in northern China. Hazard quotients (HQs) based on estimated daily intakes (EDIs) were conducted. Sociodemographic characteristics and food consumption during pregnancy were collected and seasons of sample collection were recorded. The detection rate of urinary BPA was 86.6% and the median concentrations were 0.48 μg/L (1.05 μg/g creatinine). The EDI (median = 0.008 μg/kg bw/day) was much lower than the recommended tolerable daily doses and the HQ (median = 0.002) much lower than 1. The urine collected in summer had significantly higher BPA levels than that collected in other seasons (β = 0.225; 95% CI − 0.008, 0.458; p = 0.03). Women “always consuming shellfish” had significantly higher BPA levels than those “seldom consuming shellfish” (β = 0.341; 95% CI 0.022, 0.66; p = 0.04). The study found a wide exposure to BPA among pregnant women in this region, which might be associated with seasonal variation and shellfish consumption. Although the HQs suggested no obvious risk, further attention to the comprehensive exposure and potential determinants should be paid in view of its endocrine-disrupting potential.
اظهر المزيد [+] اقل [-]Production of gasoline range hydrocarbons from catalytic cracking of linoleic acid over various acidic zeolite catalysts
2019
Gurdeep Singh, Haswin Kaur | Suzana Yusup, | Quitain, Armando T. | Kida, Tetsuya | Sasaki, Mitsuru | Cheah, Kin Wai | Ameen, Mariam
Employment of edible oils as alternative green fuel for vehicles had raised debates on the sustainability of food supply especially in the third-world countries. The non-edible oil obtained from the abundantly available rubber seeds could mitigate this issue and at the same time reduce the environmental impact. Therefore, this paper investigates the catalytic cracking reaction of a model compound named linoleic acid that is enormously present in the rubber seed oil. Batch-scale experiments were conducted using 8.8 mL Inconel batch reactor having a cyclic horizontal swing span of 2 cm with a frequency of 60 cycles per minute at 450 °C under atmospheric condition for 90 min. The performance of HZSM-5, HBeta, HFerrierite, HMordenite and HY catalysts was tested for their efficiency in favouring gasoline range hydrocarbons. The compounds present in the organic liquid product were then analysed using GC-MS and classified based on PIONA which stands for paraffin, isoparaffin, olefin, naphthenes and aromatics respectively. The results obtained show that HZSM-5 catalyst favoured gasoline range hydrocarbons that were rich in aromatics compounds and promoted the production of desired isoparaffin. It also gave a higher cracking activity; however, large gaseous as by-products were produced at the same time.
اظهر المزيد [+] اقل [-]Estimation of cadmium content in Egyptian foodstuffs: health risk assessment, biological responses of human HepG2 cells to food-relevant concentrations of cadmium, and protection trials using rosmarinic and ascorbic acids
2019
Darwish, Wageh Sobhy | Chiba, Hitoshi | Elhelaly, Abdelazim Elsayed | Hui, Shu-Ping
Cadmium (Cd) is an environmental pollutant that can get entry into human body via ingestion of contaminated foods causing multiple organ damage. This study aimed at monitoring Cd residues in 20 foodstuffs of animal origin that are commonly consumed in Egypt. Health risk assessment was conducted via calculation of Cd dietary intakes and non-carcinogenic target hazard quotient. An in vitro approach was performed to investigate the constitutive effects of Cd on human hepatoma (HepG2) cells under food-relevant concentrations. Trials to reduce Cd-induced adverse effects on HepG2 cells were done using rosmarinic (RMA) and ascorbic acids (ASA). The achieved results indicated contamination of the tested foodstuffs with Cd at high levels with potential human health hazards. Cd at food-relevant concentrations caused significant cytotoxicity to HepG2 cells. This may be attributed to induction of oxidative stress and inflammation, as indicated by the overexpression of stress and inflammatory markers. At the same time, Cd downregulated xenobiotic transporters and upregulated the proliferation factors. Co-exposure of HepG2 cells to Cd and micronutrients such as RMA and ASA led to recovery of cells from the oxidative damage, and subsequently cell viability was strongly improved. RMA and ASA ameliorated the biological responses of HepG2 cells to Cd exposure.
اظهر المزيد [+] اقل [-]Predicting eco-conscious consumer behavior using theory of planned behavior in Pakistan
2019
Hameed, Irfan | Waris, Idrees | Amin ul Haq, Mirza
Sustainability of the environment has become pivotal in the modern world, and there have been enormous efforts by the world leaders and organizations to reduce the effects of hazardous production on the environment. This has led companies to implement pro-environment programs and work on sustainability to shift consumption from conventional products to green products. This study incorporates green trust, environmental concerns, and intrinsic religious orientation as a moderator into the theory of planned behavior. It aims to validate the theory of planned behavior and its extended form to predict Pakistani consumers’ eco-conscious behavior, and simultaneously assess the moderating effect of intrinsic religious orientation on consumers’ attitude towards green products. The data for the study was collected from 300 respondents through purposive sampling from Karachi, the metropolitan city of Pakistan. Structural equation model (SEM) was applied to test the proposed hypotheses. The results of SEM indicate that all paths in the model are significant, except the path from attitude towards green products to eco-conscious behavior. The results also indicate that intrinsic religious orientation has no moderating effect on the green trust and attitude towards green products. This study contributes to understand the effects of new constructs in the theory of planned behavior and their relationship with other variables in the model. It also provides theoretical and managerial implications to academics and marketing professionals for understanding and promoting eco-conscious consumer behavior.
اظهر المزيد [+] اقل [-]Agricultural practices and quality of environment: evidence for global perspective
2019
Anwar, Awais | Sarwar, Suleman | Amin, Waqas | Arshed, Noman
The study emphasizes to examine the causal relationship among CO₂ emission, agricultural value added, industrial production, urbanization, nuclear energy consumption, and economic growth across the panel of 59 countries. The data is collected from World Bank database over the period of 1982–2015. For econometric estimations, we have divided the sample into different income groups: low income, lower middle income, upper middle income, and higher income. In case of higher income countries, empirical results have reported the unidirectional causality from agricultural value added to CO₂ emission, whereas, bidirectional causality between nuclear energy consumption and CO₂ emission. Upper-middle-income countries have confirmed the bidirectional causality between CO₂ emissions and agricultural added; however, unidirectional causality runs from nuclear consumption to CO₂ emission. According to Granger causality estimations, agricultural value added and nuclear energy consumption do not cause the CO₂ emission in low income and lower-middle-income countries. Long-run estimations have mentioned that higher agricultural value added leads to increase the CO2 emission, in upper middle income and higher income countries. On contrary, in case of low-income and lower-middle-income countries, agricultural value added has inverse relationship with CO₂ emission. Higher nuclear energy consumption tends to reduce the CO₂ emission, except the upper-middle-income countries.
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