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Результаты 2461-2470 из 4,309
Occurrence and risk assessment of trace metals and metalloids in sediments and benthic invertebrates from Dianshan Lake, China Полный текст
2017
Wu, Yan | Zhou, Yihui | Qiu, Yanling | Chen, Da | Zhu, Zhiliang | Zhao, Jianfu | Bergman, Åke
The present study measured concentrations of Cr, Ni, Cu, Zn, As, Cd, Sb, and Pb in surface sediments and two benthic invertebrate species (Anodonta woodiana and Bellamya aeruginosa) collected from Dianshan Lake, located in the Yangtze River Delta. The Dianshan Lake acts as one of the most important drinking water sources to Shanghai, the biggest city in China. Concentrations of trace metals and metalloids ranged from 0.04 mg/kg for Cd to 288.0 mg/kg for Zn. Substantial bioaccumulation in invertebrates was observed for Zn and Cu based on the biota-sediment accumulation factor (BSAF) measurements. The results revealed that concentrations of metals and metalloids in sediments from Dianshan Lake were at the lower end of the range of levels found in other regions of China. The assessment of three significantly inter-related evaluation indices, including the geo-accumulation Index (Igₑₒ), potential ecological risk factor (Erⁱ), and mean probable effect concentration quotients (Qₘ₋PEC), suggested that sediment-associated trace elements exhibited no considerable ecological risks in the studied watershed. However, the target hazard quotient and hazard index analysis suggested that selected elements (particularly As) accumulation in edible tissues of benthic invertebrates could pose potential health risks to local populations, especially fishermen. Given that wild aquatic organisms (e.g., fish and bivalves) constitute the diet of local populations as popular food/protein choices, further investigations are needed to better elucidate human health risks from metal and metalloid exposure via edible freshwater organisms.
Показать больше [+] Меньше [-]Effects of live Myriophyllum aquaticum and its straw on cadmium accumulation in Nasturtium officinale Полный текст
2017
Huang, Kewen | Lin, Lijin | Chen, Fabo | Liao, Ming’an | Wang, Jin | Tang, Yi | Lai, Yunsong | Liang, Dong | Xia, Hui | Wang, Xun | Ren, Wei
The purpose of this study is to determine whether the allelopathy of living Myriophyllum aquaticum and its straw has the same effects; two pot experiments were conducted to study the effects of intercropping using M. aquaticum and its straw on the growth and cadmium (Cd) accumulation of Nasturtium officinale. Different planting ratios (1:3, 2:2 and 3:1) of N. officinale and M. aquaticum led to an increase in the biomass of both plant species and increased the Cd content in roots and shoots of N. officinale, but led to a reduction in the Cd content in roots and shoots of M. aquaticum. When the intercropping ratio of N. officinale and M. aquaticum was 3:1, the Cd amount in whole plants reached the maximum of 293.96 μg pot⁻¹. Mulching the straw of M. aquaticum roots on the soil surface increased the biomass of N. officinale, but mulching the straw of M. aquaticum stems and leaves led to a decrease. Mulching the straw of roots, stems and leaves of M. aquaticum reduced Cd content and amounts in roots and shoots of N. officinale. Intercropping with M. aquaticum can improve the Cd uptake ability of N. officinale, but mulching M. aquaticum straw can reduce its Cd uptake ability.
Показать больше [+] Меньше [-]Adsorption studies on the removal of COD and BOD from treated sewage using activated carbon prepared from date palm waste Полный текст
2017
Nayl, AbdElAziz A. | Elkhashab, RedaA. | El Malah, Tamer | Yakout, SobhyM. | El-Khateeb, MohamedA. | Ali, MahmoudM. S. | Ali, HazimM.
In this work, the adsorption of chemical oxygen demand (COD) and biological oxygen demand (BOD) from treated sewage with low-cost activated carbon prepared from date palm shell waste by chemical activation method was studied. Different parameters affecting the adsorption process such as carbon dose, pH, contact time, agitation rate, and temperature were studied. Adsorption equilibrium was attained after 150 min at pH 6.0 with agitation rate of 400 rpm at 25 °C. The results showed that COD removal percentage of 95.4 and 92.8% for BOD was obtained with carbon dosage of 0.1 g/100 ml of solution. The experimental batch equilibrium results follow linear, Langmuir, and Freundlich isotherm models. The experimental data was fitted to a pseudo-second-order kinetics model controlled by pore diffusion. Thermodynamic parameter values of ΔH ⁰, ΔG ⁰, and ΔS ⁰ were calculated. The obtained data indicated that the adsorption was spontaneous, endothermic nature and reflects an increased randomness and degree of disorderliness at the activated carbon/sewage interface during the adsorption process investigated in this study. Concentrations of different impurities were reduced to very small value by investigated adsorption process.
Показать больше [+] Меньше [-]Cadmium effect on physiological responses of the tolerant Chlorophyta specie Picocystis sp. isolated from Tunisian wastewaters Полный текст
2017
Rihab, Ben Ali | Sabrine, Ben Ouada | Lina, Chouchene | Imed, Messaoudi | Hatem, Ben Ouada | Ali, Othmane
This study aims to investigate the effects of different concentrations of cadmium (Cd) (0–800 μM) on the growth, the photosynthetic performance, and the biochemical parameters of the Chlorophyta Picocystis sp. during 3 and 9 days. Results showed that this exposure did not inhibit the Picocystis growth during the first 3 days of treatment. Growth inhibition did not exceed 53%, which was recorded at high Cd concentrations (800 μM) after nine exposure days. Moreover, no inhibitory effect on the Picocystis sp. photosynthesis has been recorded during the three exposure days regardless the Cd concentrations. Lipid peroxidation was significantly increased at high Cd concentrations (500 and 800 μM) by 40 and 80%, respectively. Furthermore, the highest Cd concentration enhanced the thiol protein content, indicating no consequent protein oxidation. The exposure of Picocystis to Cd stimulated the antioxidant activities of catalase and ascorbate peroxidase. These results showed that Picocystis sp. has an impressive tolerance to Cd stress.
Показать больше [+] Меньше [-]Financial development and sectoral CO2 emissions in Malaysia Полный текст
2017
Maji, Ibrahim Kabiru | Muzafar Shah Habibullah, | Mohd. Yusof Saari,
The paper examines the impacts of financial development on sectoral carbon emissions (CO₂) for environmental quality in Malaysia. Since the financial sector is considered as one of the sectors that will contribute to Malaysian economy to become a developed country by 2020, we utilize a cointegration method to investigate how financial development affects sectoral CO₂ emissions. The long-run results reveal that financial development increases CO₂ emissions from the transportation and oil and gas sector and reduces CO₂ emissions from manufacturing and construction sectors. However, the elasticity of financial development is not significant in explaining CO₂ emissions from the agricultural sector. The results for short-run elasticities were also consistent with the long-run results. We conclude that generally, financial development increases CO₂ emissions and reduces environmental quality in Malaysia.
Показать больше [+] Меньше [-]Preparation of transition metal composite graphite felt cathode for efficient heterogeneous electro-Fenton process Полный текст
2017
A composite graphite felt (GF) modified with transition metal was fabricated and used as cathode in heterogeneous electro-Fenton (EF) for methyl orange (MO) degradation. Characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), the morphology and surface physicochemical properties of the cathodes after modification were observed considerably changed. After loading metals, the current response became higher, the accumulation of H₂O₂ and the degradation efficiency of MO were improved. Under the same conditions, GF-Co had the highest catalytic activity for electro-reduction of O₂ to H₂O₂ and MO degradation. At pH 3, 99 % of MO degradation efficiency was obtained using GF-Co after 120 min treatment and even at initial pH 9, 82 % of that was obtained. TOC removal efficiency reached 93.8 % using GF-Co at pH 3 after 120 min treatment while that was 12.3 % using GF. After ten-time runs, the mineralization ratio of the GF-Co was still 89.5 %, suggesting that GF-Co was very promising for wastewater treatment. The addition of isopropanol proved that ·OH played an important role in degradation of MO.
Показать больше [+] Меньше [-]Enhancing filterability of activated sludge from landfill leachate treatment plant by applying electrical field ineffective on bacterial life Полный текст
2017
Akkaya, Gulizar Kurtoglu | Sekman, Elif | Top, Selin | Sagir, Ece | Bilgili, Mehmet Sinan | Guvenc, Senem Yazici
The aim of this study is to investigate filterability enhancement of activated sludge supplied form a full-scale leachate treatment plant by applying DC electric field while keeping the biological operational conditions in desirable range. The activated sludge samples were received from the nitrification tank in the leachate treatment plant of Istanbul’s Odayeri Sanitary Landfill Site. Experimental sets were conducted as laboratory-scale batch studies and were duplicated for 1A, 2A, 3A, 4A, and 5A of electrical currents and 2, 5, 10, 15, and 30 min of exposure times under continuous aeration. Physicochemical parameters such as temperature, pH, and oxidation reduction potential in the mixture right after each experimental set and biochemical parameters such as chemical oxygen demand, total phosphorus, and ammonia nitrogen in supernatant were analyzed to define the sets that remain in the range of ideal biological operational conditions. Later on, sludge filterability properties such as capillary suction time, specific resistance to filtration, zeta potential, and particle size were measured for remaining harmless sets. Additionally, cost analyses were conducted in respect to energy and electrode consumptions. Application of 2A DC electric field and 15-min exposure time was found to be the most favorable conditions to enhance filterability of the landfill leachate-activated sludge.
Показать больше [+] Меньше [-]Precipitation and air temperature control the variations of dissolved organic matter along an altitudinal forest gradient, Gongga Mountains, China Полный текст
2017
Hu, Zhaoyong | Wang, Genxu | Sun, Xiangyang
Dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) contribute significantly to C and N cycling in forest ecosystems. Little information is available on the variations in the DOC and DON concentrations and depositions in bulk and stand precipitation within forests along an altitudinal gradient. To determine the temporal variations in the DOC and DON concentrations and depositions in different forests and the spatial variations along the elevation gradient, the DOC and DON concentrations and depositions were measured in bulk precipitation, throughfall, and stemflow within three forest types, i.e., broadleaf forest (BLF), broadleaf-coniferous forest (BCF), and coniferous forest (CF), during the wet season (May to October) on Gongga Mountain, China, in 2015. The concentrations of bulk precipitation in BLF, BCF, and CF were 3.92, 4.04, and 2.65 mg L⁻¹, respectively, for DOC and were 0.38, 0.26, and 0.29 mg L⁻¹, respectively, for DON. BCF had the highest DOC deposition both in bulk precipitation (45.12 kg ha⁻¹) and stand precipitation (98.52 kg ha⁻¹), whereas the highest DON deposition was in BLF (3.62 kg ha⁻¹ bulk precipitation and 4.11 kg ha⁻¹ stand precipitation) during the study period. The meteorological conditions of precipitation and air temperature significantly influenced the dissolved organic matter (DOM) depositions along the elevation gradient. The leaf area index did not show any correlation with DOM depositions during the growing season.
Показать больше [+] Меньше [-]Selective adsorption of Pb (II) over the zinc-based MOFs in aqueous solution-kinetics, isotherms, and the ion exchange mechanism Полный текст
2017
Wang, Lei | Zhao, Xinhua | Zhang, Jinmiao | Xiong, Zhenhu
Two series of metal–organic frameworks (MOFs) with similar formula units but different central metal ions (M) or organic linkers (L), M-BDC (BDC = terephthalate, M = Zn, Zr, Cr, or Fe), or Zn-L (L = imidazolate-2-methyl, BDC, BDC-NH₂), were prepared and employed as the receptors for adsorption lead ions. It was found that the Zn-BDC exhibited a much higher adsorption capacity than the other M-BDC series with various metal ions which have very closely low capacities at same conditions. Furthermore, the Zn-L (L = imidazolate-2-methyl, BDC, BDC-NH₂) still have highly efficient adsorption capacity of lead ions, although the adsorption capacity varies with different ligand, as well as the adsorption rate and the equilibrium pH of the solution. This significant high adsorption over Zn-L, different from other M-BDC series with various metal ions (Zr, Cr, or Fe), can be explained by ion exchange between the central metal ions of Zn-L and lead ion in solution. Based on the analysis of FT-IR, X-ray diffraction pattern, the nitrogen adsorption isotherms, the zeta potentials, and the results, a plausible adsorption mechanism is proposed. When equivalent Zn-L were added to equal volume of aqueous solution with different concentration of lead ion, the content of zinc ion in the solution increases with the increase of the initial concentration of lead ions. The new findings could provide a potential way to fabricate new metal organic frameworks with high and selective capacities of the heavy metal ions.
Показать больше [+] Меньше [-]Adaptation of primocane fruiting raspberry plants to environmental factors under the influence of Bacillus strains in Western Siberia Полный текст
2017
Belyaev, Anatoly A. | Shternshis, Margarita V. | Chechenina, Nina S. | Shpatova, Tatyana V. | Lelyak, Anastasya A.
In geographical locations with a short vegetative season and continental climate that include Western Siberia, growing primocane fruiting raspberry varieties becomes very important. However, it is necessary to help the plants to overcome the environmental stress factors. This study aimed to evaluate the impact of the pre-planting treatment of primocane fruiting raspberry root system with Bacillus strains on the following plant development under variable environmental conditions. In 2012, Bacillus subtilis RCAM В-10641, Bacillus amyloliquefaciens RCAM В-10642, and Bacillus licheniformis RCAM В-10562 were used for inoculating the root system of primocane fruiting raspberry cultivar Nedosyagaemaya before planting. The test suspensions were 10⁵ CFU/ml for each bacterial strains. The effects of this treatment on plant growth and crop productivity were estimated in 2012–2015 growing seasons differed by environmental conditions. The pre-planting treatment by the bacterial strains increased the number of new raspberry canes and the number of plant generative organs as well as crop productivity compared to control. In addition, these bacilli acted as the standard humic fertilizer. Variable environmental factors such as air temperature, relative humidity, and winter and spring frosts seriously influenced the plant biological parameters and crop productivity of control plants. At the same time, the pre-planting primocane fruiting root treatment by Bacillus strains decreased the negative effects of abiotic stresses on plants in all years of the research. Of the three strains studied, B. subtilis was shown to reveal the best results in adaptation of primocane fruiting raspberry plants to environmental factors in Western Siberia. For the first time, the role of Bacillus strains in enhancing frost resistance in primocane fruiting raspberry plants was shown. These bacilli are capable of being the basis of multifunctional biological formulations for effective plant and environmental health management in growing primocane fruiting raspberry.
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