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Результаты 3431-3440 из 4,924
Management of green transportation: an evidence-based approach
2019
Shouket, Bilal | Zaman, Khalid | Nassani, Abdelmohsen A. | Aldakhil, Abdullah Mohammed | Abro, Muhammad Moinuddin Qazi
The objective of the study is to examine the impact of air-railways transportation on environmental degradation in the form of high mass carbon emission, natural resource depletion and forest depletion in the context of Pakistan by using an annual time series data from 1975 to 2016. The results show that railway passengers carried increases carbon emissions while air-railways transportation and travel services degrade environment in the form of natural resource depletion. The study verified “pollution haven hypothesis” where trade liberalization policies increases carbon emissions; however, “population genius” principle is hold where population growth conserve natural resources and environment through affluence and technology. The study concluded that government should take serious action to re-define transportation infrastructure in order to promote environmental sustainability agenda by introducing green vehicles and green transportation system, which is imperative for country’s long-term sustainable development.
Показать больше [+] Меньше [-]Studies on mercury occurrence in inorganic constituents of Polish coking coals
2019
Dziok, Tadeusz | Strugała, Andrzej | Włodek, Adam
During the cokemaking process, a significant amount of mercury occurring in a coal blend is released to the atmosphere. One of the ways of reducing this emission is to reduce mercury content in a coal blend. This could be obtained through the coal washing process. The optimization of this process requires the knowledge of mercury occurrence in coal, especially in its inorganic constituents. A qualitative analysis of mercury occurrence in the inorganic constituents of Polish coking coals was performed using an electron probe microanalyzer (EPMA). For that purpose, selected samples of rejects and middling products derived from the washing process in dense media separators and jig concentrators were examined. The obtained results have confirmed a strong connection between mercury occurrence and the presence of sulfides (pyrite, marcasite, and chalcopyrite) in Polish coking coals. Significant amounts of mercury were also noticed for barite, siderite, and aluminosilicates. The highest value of mercury content, at the level of 0.100%, was obtained for marcasite. For the analyzed coals, the effectiveness of mercury removal in the washing process was determined by the forms of pyrite occurring in coal. The highest values of effectiveness of mercury removal were obtained in the case of coals for which the large framboidal pyrite aggregates with chalcopyrite overgrowths were noticed. It was also found that middling products were characterized by the occurrence of the Hg-rich overgrowths of pyrite on organic matter. To achieve a significant reduction in mercury content in clean coal, it is necessary to develop an effective method of removing this form of pyrite from hard coal.
Показать больше [+] Меньше [-]Metal distribution in sediments of a drinking water reservoir: influence of reservoir morphometry and hydrodynamics
2019
Zhu, Lin | Wang, Tianxiang | Liu, Jianwei | Xu, Shiguo | Chen, Xiaoqiang | Jiang, Xin
Metal(loid)s in the reservoir sediment tend to be released into the water column when encountering disturbances and thus pose threats to the aquatic system. In this study, sediment and pore water samples collected from eight cross sections in the Biliu River Reservoir (Dalian, China) were analyzed to determine the spatial distributions of six metal(loid)s and their associations with reservoir morphometry and hydrodynamics. The results show that total metal concentrations of the sediments are higher at the sites with greater water depths and are influenced by the reservoir morphometry. Mn is of great concern with respect to its increasing total concentration from the upstream sites to the dam sites. According to the improved BCR sequential extraction procedure, the acid-soluble fraction of Mn increases along the thalweg to the dam, implying the soluble Mn²⁺ in the upstream hypolimnion, and sediment is possible to be transported longitudinally by water currents. For Fe, Mn, Pb, Cu, and Zn, the reducible fraction accounts for more than 15% of the total metal concentration, which suggests that Fe–Mn (hydr)oxides could be important in scavenging these metals. High Mn concentrations in pore waters close to the dam, with an average value of more than 40 mg/L, give rise to significant Mn diffusive flux up to 296.1 mg/m²/day.
Показать больше [+] Меньше [-]Correction to: Efficient removal of dyes from dyeing wastewater by powder activated charcoal/titanate nanotube nanocomposites: adsorption and photoregeneration
2019
Lin, Yingchao | Ma, Jun | Liu, Wen | Li, Zeyu | He, Kai
The original publication of this paper contains a mistake. The published Fig. 8 does not cite the related reference, and several grammar errors has been found in the image. The improved version of Fig. 8 and its caption is shown in this correction. These errors do not change the conclusions
Показать больше [+] Меньше [-]Quantitative PCR-based identification of enteric viruses contaminating fresh produce and surface water used for irrigation in Egypt
2019
Shaheen, Mohamed N. F. | Elmahdy, Elmahdy M. | Chawla-Sarkar, Mamta
Fresh produce irrigated with surface water that may contain pathogens such as enteric viruses can lead to outbreaks of foodborne viral illnesses. In the current study, we performed real-time PCR (qPCR) to monitor the presence of enteric viruses such as human adenoviruses (HAdVs), hepatitis A virus (HAV), rotavirus group A (RVA), and norovirus GI (NoV GI) in surface water and fresh produce that were grown using this surface water in Egypt. Samples were collected on four occasions from different sites located in the Delta and in Greater Cairo, Egypt. Of the 32 water samples and 128 fresh produce samples, 27/32 (84.3%) and 99/128 (77.3%), respectively, were positive for at least one virus. HAdV (30/32) with a mean viral load = 1.5 × 10⁷ genome copies/L (GC/L) was the most commonly detected virus in water, followed by RVA (16/32, with a mean viral load = 2.7 × 10⁵ GC/L), HAV (11/32, with a mean viral load = 1.2 × 10⁴ GC /L), and NoV GI (10/32, with a mean viral load = 3.5 × 10³ GC/L). Additionally, HAdV (71/128, with a mean viral load = 9.8 × 10⁵ GC/g) was also the most commonly detected virus in the fresh produce, followed by NoV GI (43/128, with a mean viral load = 4.5 × 10³ GC/g), HAV (33/128, with a mean viral load = 6.4 × 10³ GC/g), and RVA (25/128, with a mean viral load = 1.5 × 10⁴ GC/g). Our results indicate that fresh produce may be contaminated with a wide range of enteric viruses, and these viruses may originate from virus-contaminated irrigation water. Moreover, this fresh produce may serve as a potential vector for the transmission of viral foodborne illnesses. These findings are important for future risk assessment analysis related to water/foodborne viruses. Graphical abstract . Please provide caption for Graphical AbstractGraphical abstract showing sample collection and processing
Показать больше [+] Меньше [-]Nanomaterials as versatile adsorbents for heavy metal ions in water: a review
2019
Sarma, Gautam Kumar | Sen Gupta, Susmita | Bhattacharyya, Krishna G.
Over the years, heavy metal pollution has become a very serious environmental problem worldwide. Even though anthropogenic sources are believed to be the major cause of heavy metal pollution, they can also be introduced into the environment from natural geogenic sources. Heavy metals, because of their toxicity and carcinogenicity, are considered to be the most harmful contaminants of groundwater as well as surface water, a serious threat to both human and aquatic life. Nanomaterials due to their size and higher surface area to volume ratio show some unique properties compared to their bulk counterpart and have drawn significant attention of the scientific community in the last few decades. This large surface area can make these materials as effective adsorbents in pollution remediation studies. In this review, an attempt has been made to focus on the applicability of different types of nanomaterials, such as clay-nanocomposites, metal oxide-based nanomaterials, carbon nanotubes, and various polymeric nanocomposites as adsorbents for removal of variety of heavy metals, such as As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sn, U, V, and Zn, from water as reported during the last few years. This work tries to analyze the metal–nanomaterial interactions, the mechanism of adsorption, the adsorption capacities of the nanomaterials, and the kinetics of adsorption under various experimental conditions. The review brings forward the relation between the physicochemical properties of the nanomaterials and heavy metal adsorption on them.
Показать больше [+] Меньше [-]Effects of straw returning and feeding on greenhouse gas emissions from integrated rice-crayfish farming in Jianghan Plain, China
2019
Sun, Zichuan | Guo, Yao | Li, Chengfang | Cao, Cougui | Yuan, Pengli | Zou, Fengliang | Wang, Jinhua | Jia, Pingan | Wang, Jinping
Great efforts have been devoted to assessing the effects of straw managements on greenhouse gas (GHG) emissions, global warming potential (GWP), and net economic budget in rice monoculture (RM). However, few studies have evaluated the effects of straw managements on GHG emissions and net ecosystem economic budget (NEEB) in integrated rice-crayfish farming (RC). Here, a randomized block field experiment was performed to comprehensively evaluate the effects of aquatic breeding practices (feeding or no feeding of forage) and straw managements (rice straw returning or removal) on soil NH₄⁺–N and NO⁻₃–N contents, redox potential (Eh), CH₄ and N₂O emissions, GWP, and NEEB of fluvo-aquic paddy soil in a rice-crayfish co-culture system in Jianghan Plain of China. We also compared the differences in CH₄ and N₂O emissions, GWP, and NEEB between RM and RC. Straw returning significantly increased CH₄ and N₂O emissions by 34.9–46.1% and 6.2–23.1% respectively compared with straw removal. Feeding of forage decreased CH₄ emissions by 13.9–18.7% but enhanced N₂O emissions by 24.4–33.2% relative to no feeding. Compared with RM treatment, RC treatment decreased CH₄ emissions by 18.1–19.6% but increased N₂O emissions by 16.8–21.0%. Moreover, RC treatment decreased GWP by 16.8–22.0% while increased NEEB by 26.9–75.6% relative to RM treatment, suggesting that the RC model may be a promising option for mitigating GWP and increasing economic benefits of paddy fields. However, the RC model resulted in a lower grain yield compared with the RM model, indicating that more efforts are needed to simultaneously increase grain yield and NEEB and decrease GWP under RC model.
Показать больше [+] Меньше [-]A comparative study of trace elements in Cymodocea nodosa from three semi-enclosed coastal areas in Tunisia
2019
Zakhama-Sraieb, Rym | Zribi, Imen | Mnasri, Intissar | Charfi-Cheikhrouha, Faouzia
The present study quantifies the levels of five trace elements (TEs) Zn, Cu, Ni, Pb, and Cd in the leaves and rhizomes of Cymodocea nodosa as well as the surficial sediments from three semi-enclosed coastal areas in Tunisia, in the south Mediterranean Sea. Samples were taken from the Bizerte and Ghar El Melh lagoons and from marina Cap Monastir. The TE ranking was found to be Zn > Cu > Pb > Ni > Cd in sediments and Zn > Cu = Ni = Pb = Cd in C. nodosa leaves and rhizomes. Except for Ni, levels of Zn, Cu, Pb, and Cd significantly differed between the sites. Translocation factors (TFs) were > 1 for all trace elements proving the high capacity of C. nodosa to accumulate TEs in its above-ground tissues. Results show that marina Cap Monastir’s meadow exhibits higher TFs than the Bizerte and Ghar El Melh lagoons. This can be due to the presence of the non-indigenous species Halophila stipulacea. The present study highlights the need for further investigation on the effect of interspecific interaction on TE uptake by seagrasses.
Показать больше [+] Меньше [-]Can we use Cd-contaminated macrophytes for biogas production?
2019
Fernandes, Katiúcia Dias | Cañote, Susan Johana Benites | Ribeiro, Eruin Martusceli | Thiago Filho, Geraldo Lúcio | Fonseca, Ana Lúcia
Aside from the ability of plants to remove domestic-industrial wastewater contaminants from various types of water, macrophytes can also serve as an alternative source of energy. The goal of the present study was to test the viability of biogas production using aquatic macrophyte species—Eichhornia crassipes and Pistia stratiotes—contaminated with cadmium (Cd) after the phytoremediation process. The plants were transferred to a nutrient solution contaminated with 0.8 mg L⁻¹of Cd. The experiment was set up in a 2 × 3 factorial scheme with the presence or absence of Cd and three phytoremediation times (20, 40, or 60 days) using P. stratiotes followed by an additional treatment consisting of P. stratiotes + E. crassipes for 20 days. The acute and chronic effects of bioassays with the microcrustacean Daphnia similis were used to evaluate the ability of the macrophytes to remove toxicity by phytoremediation. The viability test of biogas production after phytoremediation was evaluated using micro-biodigesters. According to the results, at least 60 days of phytoremediation are necessary to remove/remediate the Cd present in the contaminated solution. The metal did not influence the macrophytes’ methanogenic activity, showing that these macrophytes can be used for biogas/methane production. The combination of Pistia stratiotes with Eichhornia crassipes is a good alternative to reduce phytoremediation time, but for 20 days of testing, the presence of Eichhornia crassipes reduces the biogas production/CH₄. However, it is believed that if the digestion time is extended, this effect can be minimized. The phytoremediation time indicated that Pistia stratiotes must remain at least 60 days to remove/remediate the Cd present in the contaminated solution.
Показать больше [+] Меньше [-]Distribution of heavy metal and macroelements of Indian and imported cigarette brands in Turkey
2019
Özcan, Mehmet Musa | Aljuhaimi, Fahad | Uslu, Nurhan | Ghafoor, Kashif | Mohamed Ahmed, Isam A. | Babiker, Elfadıl E.
While Cd contents of cigarettes are determined between 0.44 (C8) and 1.55 mg/kg (C7), Co contents of cigarette samples varied between 0.26 (B5) and 2.19 mg/kg (B3). Also, while Cr contents of tested cigarettes are determined between 0.88 mg/kg (C5) and 1.72 mg/kg (B2), Mo contents of cigarettes ranged from 0.39 (C7) to 1.13 mg/kg (B2). In addition, Cu contents of cigarettes varied between 10.36 (C11) and 30.47 mg/kg (C18), while Fe contents of cigarette samples range between 306.03 (C5) and 595.42 mg/kg (C16). In addition, while Ni contents of cigarettes vary between 1.00 (C7) and 3.17 mg/kg (C1), Pb contents of brands varied between 0.16 (B4) and 7.37 mg/kg (B1). In general, Indian and imported cigarette samples used in Turkey are rich in Ca, K, Mg, P, and S. In Indian samples, B4 and B5 cigarette samples contained lower heavy metals compared with other cigarettes.
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