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النتائج 5281 - 5290 من 6,560
The contents and release behavior of heavy metals in construction and demolition waste used in freeway construction النص الكامل
2020
Chen, Yuyun | Zhou, Yiqiang
A large volume (more than 4.0 million m³) of treated construction and demolition waste (CDW) is planned to be used in the construction of the Xi’an-Xianyang north loop line freeway in West China. These CDW were preliminarily separated into broken concretes, bricks, and porcelains in the treatment plants. In this study, a total of 190 CDW samples including 80 concretes, 80 bricks, 20 porcelains, and 10 mixed samples were collected from five treatment plants. Five farmland soil samples near treatment plants were collected as controls. The contents of 10 elements including cadmium (Cd), arsenic (As), copper (Cu), nickel (Ni), zinc (Zn), chromium (Cr), lead (Pb), manganese (Mn), silver (Ag), and mercury (Hg) in these samples were measured. The contents of 8 elements (Cu, Ni, Zn, Cr, Pb, Mn, Ag, and Hg) in all CDW samples were qualified for the third-level criterion of the Standard of Soil Environment (GB15618-2008). However, Cd contents in 37 concretes, 34 bricks, 6 porcelain samples, and 4 mixed CDW samples exceeded the national third-level standards (1 mg/kg) in GB15618-2008. And As contents in 28 concretes, 21 bricks, 5 porcelain samples, and 3 mixed CDW samples were higher than the national third-level standards (40 mg/kg). The total exceeding standard rates (ESRs) of Cd and As were 42.6% and 30%, respectively. The leaching tests for Cd and As were also done due to their higher ESRs. The results showed that the release amounts (μg/kg) of Cd and As from CDW were increased with increasing liquid to solid ratio (0.4–10 l/kg) but decreased with increasing pH (4–7). The leached concentrations of Cd and As from four types of CDW samples were both in a descending order: brick, mixed materials, concrete, and porcelain. The measured concentrations (μg/L) of Cd and As in leachate were all lower than second-grade criteria of Standard for Groundwater Quality (GB3838-2002). By comparing the leached concentrations of Cd and As with the value in European criteria (EU Council Decision 2003/33/EC) for hazardous wastes, all the CDW samples should be classified as inert or non-hazardous wastes. Thus, it could be concluded that heavy metals in these CDW would not pollute surrounding soil, surface water, and groundwater environment when applied in freeway construction.
اظهر المزيد [+] اقل [-]Radon and its progenies variation in the urban polluted atmosphere of the Mediterranean city of Thessaloniki, Greece النص الكامل
2020
Stoulos, Stylianos | Ioannidou, Alexandra
Radon and Rn progenies’ concentrations were determined in the urban polluted atmosphere of Thessaloniki’s city center using two experimental procedures: (i) filter with 0.8-μm porosity measured using α-counting technique determining the radon equilibrium equivalent concentration (CEER), which varies from 2.6 to 8.9 Bq m⁻³, and (ii) filter with 0.3-μm porosity measured in the laboratory using γ-spectrometry determining ²¹⁴Pb activity concentration 1.3–7.5 Bq m⁻³ and ²¹⁴Bi activity 3.1–11.5 Bq m⁻³. Strong daily correlation with the relative humidity is presented, in association to an inverse correlation with the temperature gradient. Radon and its daughter’s concentration correlate well smoke particles’ content because radon is trapped inside them due to their high effective porosity, and so the Rn daughter collection in the filter increases. Gas pollutants have similar daily distribution with the radon activity, while SO₂ levels are correlated the best with ²¹⁴Pb and ²¹⁴Bi concentrations, as Pb is more chemically associated to sulfuric complex ions than nitric formation in presence of vapors. The lower ²¹⁴Pb/ ²¹⁴Bi activity ratio appeared during the highest temperature gradient and amount of vapors, smoke, and gases giving rise to high formation of ultrafine aerosol particles. The ultrafine aerosol creation boosts ²¹⁴Pb recoil effect taken place during ²¹⁸Po α-decay, so ²¹⁴Pb nuclei become free starting the clustering process yet again having ingrowth coefficient ~ 0.1 nm² s⁻¹ regarding accumulation mode aerosols.
اظهر المزيد [+] اقل [-]Intelligent-activated carbon prepared from pistachio shells precursor for effective adsorption of heavy metals from industrial waste of copper mine النص الكامل
2020
Nejadshafiee, Vajihe | Islami, Mohammad Reza
A novel and efficient bio-adsorbent based on magnetic activated carbon nanocomposites (MAC NCs)–modified by sulfamic acid (H₃NSO₃) has been developed from pistachio shell precursor as agricultural by-products and then was applied for heavy metal removal. Design an experimental model (Central Composite Design (CCD)) for adopting surface response could efficiently be used for adsorption process, and it is an economical way of obtaining the optimal adsorption conditions based on the limited number of experiments. The variants of adsorbent dosage, metal ion concentration, and contact time were optimized for Cu(II) metal by CCD. In addition, adsorption capacity and isoelectric point (pHzpc) of adsorbent were studied at different pH values. Kinetic and isotherm of adsorption were investigated via the Langmuir and the pseudo-second-order model. The maximum adsorption capacity using the Langmuir model was 277.77 mg g⁻¹ for Cu(II) ions on H₂NSO₃-MAC NCs. Then adsorption process was investigated for ions of Fe(II), Zn(II), and Ni(II) under optimized condition. Also, the competitive adsorption of Fe(II), Zn(II), and Ni(II) ions mixed solution onto H₂NSO₃-MAC NCs was conducted. Adsorption-desorption results exhibited that the H₂NSO₃-MAC NCs can be used up to seven cycles while they have excellent performance. Finally, to evaluate the efficiency of this bio-adsorbent, the removal of heavy metals from wastewater of the Sarcheshmeh copper mine as a real sample was studied. Graphical abstract
اظهر المزيد [+] اقل [-]Urinary speciated arsenic and depression among US adults النص الكامل
2020
Rahman, Humairat H. | Yusuf, Korede K. | Niemann, Danielle | Dipon, Shahriar R.
Arsenic is a naturally occurring chemical in the environment. The International Agency for Research on Cancer (IARC) declared arsenic a class 1 human carcinogen. The inorganic form of arsenic is considered toxic to the human population; arsenic is a neurotoxin and can cause memory dysfunction. Very few studies have investigated the association between exposure to arsenic and depression in humans. The purpose of this study was to assess the association between urinary speciated arsenic and depression among adults in the USA using the 2015–2016 National Health and Nutrition Examination Survey (NHANES) III dataset. Depression was measured using the nine-item Patient Health Questionnaire (PHQ-9). We computed a total depression score from the PHQ-9 and categorized individuals with a score ≥ 10 as depressed. The exposure included six different speciated arsenic concentrations dichotomized as at or above the limit of detection and below the limit of detection. We conducted a crude and multivariate logistic regression analysis using complex survey procedures to assess the association between speciated arsenic concentrations and depression. The sample included 1619 adults, of whom approximately half were females (51.69%) and married (53.29%). Seven percent of the sample had depression. Urinary arsenous acid was significantly associated with depression. In the adjusted model, arsenous acid was associated with depression with an odds ratio of 1.76 (95% CI 1.05–2.96, p = 0.035). No other forms of arsenic were significantly associated with depression. In this study, urinary arsenous acid was significantly associated with depression. Future research in humans is required to confirm or refute this finding.
اظهر المزيد [+] اقل [-]Occupational exposure to pesticides and associated health effects among greenhouse farm workers النص الكامل
2020
Amoatey, Patrick | Al-Mayahi, Ahmed | Omidvarborna, Hamid | Baawain, Mahad Said | Sulaiman, Hameed
The number and production capacities of greenhouse farms have been increased across the globe, driven by an effort for addressing food security problems related to the rapid population growth and the effects of climate change. As a result, there was a large increase in the number of greenhouse farm workers who are typically involved in chemical preparations and pesticide sprayings, crop harvesting, and greenhouse maintenance activities. Considering the enclosed architecture of the greenhouse farm design and the frequent application of pesticides, the objective of this review was to characterize pesticide exposure levels and resultant health effects among greenhouse farm workers. While most health assessment studies were mainly based on self-reported symptoms, this review showed limited epidemiological and clinical studies on the assessment of the health effects of pesticide exposure on greenhouse workers’ health. Reproductive disorders, respiratory symptoms, neurological symptoms, and skin irritations were the most reported health effects among greenhouse farm workers. Additionally, there were limited studies on respirable pesticide-borne fine and ultrafine particulate matters in greenhouse farms. Ventilation systems and indoor environmental conditions of greenhouse farms were not designed according to specifications of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). Among recommendations provided, long-term exposure assessments of pesticide effects on children born by greenhouse farm workers should be considered in future research. Also, compliance with ASHRAE indoor ventilation and environmental standards will be very important in reducing pesticide exposure and health effects among greenhouse farm workers.
اظهر المزيد [+] اقل [-]The effect of finance on inequality in Sub-Saharan Africa: avoidable CO2 emissions thresholds النص الكامل
2020
Asongu, Simplice A. | Vo, Xuan V.
There is a glaring concern of income inequality in the light of the post-2015 global development agenda of Sustainable Development Goals (SDGs), especially for countries that are in the south of the Sahara. There are also concerns over the present and future consequences of ecological degradation on development outcomes in Sub-Saharan Africa (SSA). This study provides carbon dioxide (CO₂) emissions thresholds that should be avoided in the nexus between financial development and income inequality in a panel of 39 countries in SSA over the period 2004–2014. Quantile regressions are used as an empirical strategy. The following findings are established. Financial development unconditionally decreases income inequality with an increasing negative magnitude, while the interactions between financial development and CO₂ emissions have the opposite effect with an increasing positive magnitude. The underlying nexuses are significant exclusively in the median and top quantiles of the income inequality distribution. CO₂ emission thresholds that should not be exceeded for financial development to reduce income inequality continuously are 0.222, 0.200, and 0.166 (metric tons per capita) for the median, the 75th quantile, and the 90th quantile of the income inequality distribution, respectively. Policy implications are discussed with particular relevance to Sustainable Development Goals (SDGs).
اظهر المزيد [+] اقل [-]Effectiveness of clean development policies on coal-fired power generation: an empirical study in China النص الكامل
2020
Zhang, Meizhen | Lv, Tao | Zhao, Yang | Pan, Junju
Coal-fired power will remain China’s primary source of electricity for a long time to come. The clean development of coal-fired power generation has become an important strategic choice for China’s energy transformation. Based on collecting and sorting out the driving policies for China’s clean development of coal-fired power generation from 1997 to 2016, firstly, we reviewed the historical evolution of these policies in terms of the policy quantity, policy theme, and policy instrument. Then, we designed the scoring criteria to quantify the policies. Finally, the effectiveness of the overall policies and different policy instruments was empirically analyzed by the econometric model built on the basis of Cobb-Douglas production function. The results show that the annual release amount of driving policies for the clean development of coal-fired power in China presents a trend of fluctuating growth. Policy themes are mainly divided into two parts, namely production capacity management and air pollutants control; policy instruments mainly include elimination of backward units, project approval, standards, generation price regulation, tax incentives, loan policy, and information publicity; the overall policies have significant positive effects on the clean development of coal-fired power industry; in terms of policy instruments, the elimination of backward units and generation price regulation have significant effects on improving the energy efficiency; project approval and generation price regulation are effective for reducing SO₂ emissions rate; and the effects of standards, tax incentives, loan policy, and information publicity on the clean development of coal-fired power are not significant. On these bases, some policy implications to further promote the clean development of coal-fired power industry are provided.
اظهر المزيد [+] اقل [-]Macrobenthic invertebrates as bioindicators of trace elements in high-mountain lakes النص الكامل
2020
Pastorino, Paolo | Pizzul, Elisabetta | Bertoli, Marco | Perilli, Selene | Brizio, Paola | Salvi, Gianguido | Esposito, Giuseppe | Abete, Maria Cesarina | Prearo, Marino | Squadrone, Stefania
Alpine lakes are extreme ecosystems located in remote areas and populated by few but well-adapted species. Because of their remote location, they are often considered pristine, unpolluted ecosystems. Since the 1980s, however, they have been affected by global anthropogenic impacts. Macrobenthic invertebrates play a pivotal role in these ecosystems and can be used as bioindicators also for monitoring the accumulation of trace elements. We characterized the macrobenthic invertebrates community of Balma Lake (Cottian Alps, Northwest Italy) and Dimon Lake (Carnic Alps, Northeast Italy) in summer and autumn and measured the levels of nine trace elements (As, Cd, Cr, Cu, Fe, Ni, Pb, Se, Zn) in the most abundant taxa (Chironomidae and Oligochaeta in both lakes and Hirudinea in Dimon Lake) in both seasons. The highest levels of trace elements were recorded for Fe, Cu, and Zn according to their environmental availability and their function as essential elements. The total amount of trace elements was highest for the Chironomidae from both lakes compared to the other two taxa. As, Cd, Pb, and Zn were measured in sediment to calculate bioaccumulation factor (BAF) values. The amount of elements in sediment and macrobenthic invertebrates was higher for Dimon Lake, suggesting a greater flux via precipitation of contaminants from the lowland. The BAF values were decreased with increasing trace elements concentration in sediment, indicating mechanisms of elements excretion in biota where the environment is contaminated. This study is the first to report on the use of macrobenthic invertebrates to monitor trace elements in Alpine lakes.
اظهر المزيد [+] اقل [-]Ability of Indian pennywort Bacopa monnieri (L.) Pennell in the phytoremediation of sewage (greywater) النص الكامل
2020
Tabassum-Abbasi, | Patnaik, Pratiksha | Abbasi, Shahid Abbas
The freely and abundantly available amphibious plant Indian pennywort Bacopa monnieri (L.) Pennell was able to phytoremediate sewage (greywater) quickly and substantially in SHEFROL® (“sheet flow root level”) bioreactors, achieving reductions in the levels of several indicator parameters: suspended solids, chemical oxygen demand, biological oxygen demand, nitrogen, phosphorus, zinc, copper, nickel, and manganese to the extents of about 90%, 76–77%, 80%, 65%, 55%, 56%, 42%, and 41%, respectively at hydraulic retention times of just 6 h. As these indicators of primary, secondary, and tertiary treatments were achieved simultaneously in a single reactor compartment, the system presented in this paper promises to be simple, rapid, and economical, in achieving significant treatment of greywater.
اظهر المزيد [+] اقل [-]Air-water PCB fluxes from southwestern Lake Michigan revisited النص الكامل
2020
Boesen, Aaron C. | Martinez, Andres | Hornbuckle, Keri C.
From simultaneous air and water polychlorinated biphenyl (PCB) measurements collected in September 2010, we re-evaluated the direction and magnitude of net air-water exchange of PCBs in southwest Lake Michigan and compared them with estimations made using similar approaches 15 years prior. Air and water samples were collected during a research expedition on Lake Michigan at 5 km off the coast of Chicago, with prevailing winds from the southwest of our location. Gas-phase ΣPCB concentrations ranged from 190 to 1100 pg m⁻³ with a median of 770 pg m⁻³, which is similar to the concentrations measured in the City of Chicago at the same time and similar to concentrations measured in this part of the lake over the last 20 years. Water dissolved-phase ΣPCB concentrations ranged from 150 to 170 pg L⁻¹ with a median of 160 pg L⁻¹, which is one-tenth of that measured in the 1990s. ƩPCB net fluxes showed a slightly absorptive behavior, with a median of (−) 21 ng m⁻² day⁻¹ and an interquartile range of (−) 47 to (+) 5 ng m⁻² day⁻¹, where (−) and (+) fluxes indicate absorption and volatilization, respectively. Airborne PCB concentrations were higher when the winds were coming from Chicago and drive the deposition. Our fluxes are not significantly different from estimations from 1994 and 1995 and suggest that absorption of PCBs into the waters is slightly more prevalent than 15 years ago. It was confirmed that Chicago remains an important atmospheric source of PCBs to Lake Michigan.
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