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Resultados 1631-1640 de 3,189
In situ remediation technologies for mercury-contaminated soil
2015
He, Feng | Gao, Jie | Pierce, Eric | Strong, P. J. | Wang, Hailong | Liang, Liyuan
Mercury from anthropogenic activities is a pollutant that poses significant risks to humans and the environment. In soils, mercury remediation can be technically challenging and costly, depending on the subsurface mercury distribution, the types of mercury species, and the regulatory requirements. This paper introduces the chemistry of mercury and its implications for in situ mercury remediation, which is followed by a detailed discussion of several in situ Hg remediation technologies in terms of applicability, cost, advantages, and disadvantages. The effect of Hg speciation on remediation performance, as well as Hg transformation during different remediation processes, was detailed. Thermal desorption, electrokinetic, and soil flushing/washing treatments are removal technologies that mobilize and capture insoluble Hg species, while containment, solidification/stabilization, and vitrification immobilize Hg by converting it to less soluble forms. Two emerging technologies, phytoremediation and nanotechnology, are also discussed in this review.
Mostrar más [+] Menos [-]Weather as physiologically equivalent was not associated with ischemic stroke onsets in Vienna, 2004–2010
2015
Ferrari, Julia | Shiue, Ivy | Seyfang, Leonhard | Matzarakis, Andreas | Lang, Wilfried
Stroke rates were found to have seasonal variations. However, previous studies using air temperature, humidity, or air pressure separately were not adequate, and the study catchment was not clearly drawn. Therefore, here we proposed to use a thermal index called physiologically equivalent temperature (PET) that incorporates air temperature, humidity, wind speed, cloud cover, air pressure and radiation flux from a biometeorological approach to estimate the effect of weather as physiologically equivalent on ischemic stroke onsets in an Austrian population. Eight thousand four hundred eleven stroke events in Vienna registered within the Austrian Stroke Unit Register from January 1, 2004 to December 31, 2010 were included and were correlated with the weather data, obtained from the Central Institute for Meteorology and Geodynamics in the same area and study time period and calculated as PET (°C). Statistical analysis involved Poisson regression modeling. The median age was 74 years, and men made up 49 % of the entire population. Eighty percent had hypertension while 25.4 % were current smokers. Of note, 26.5 % had diabetes mellitus, 28.9 % had pre-stroke, and 11.5 % had pre-myocardial infarction. We have observed that onsets were higher on the weekdays than on the weekend. However, we did not find any significant association between PETs and ischemic stroke onsets by subtypes in Vienna. We did not observe any significant associations between PETs and ischemic stroke onsets by subtypes in Vienna. Hospital admission peaks on the weekdays might be due to hospital administration reasons.
Mostrar más [+] Menos [-]Determination of 2,8-dichlorodibenzo-p-dioxin in toothpaste and mouthwash consumer products using GC-MS
2015
Wu, Jianlin | Hu, Chuanqin | Li, Charlie Chunlin | Cai, Zongwei | Hu, Di
A gas chromatography–mass spectrometry (GC-MS) method was developed for the identification and quantification of 2,8-dichlorodibenzo-p-dioxin (2,8-DCDD) in toothpaste and mouthwash consumer products. Liquid–liquid extraction and solid-phase extraction were used in the sample preparation. The limit of detection was 0.96 ng/g in toothpaste and 0.83 ng/g in mouthwash. The accuracy represented by relative errors was less than 12.5 %. The intra-day and inter-day precision, which are represented by the relative standard deviation values, were within 11.2 and 10.6 %, respectively. The method was successfully applied to analyze 2,8-DCDD in toothpaste and mouthwash products, as well as that from the photo-degradation of triclosan spiked in both sample matrix.
Mostrar más [+] Menos [-]Electrokinetic remediation of manganese and ammonia nitrogen from electrolytic manganese residue
2015
Shu, Jiancheng | Liu, Renlong | Liu, Zuohua | Du, Jun | Tao, Changyuan
Electrolytic manganese residue (EMR) is a solid waste found in filters after sulphuric acid leaching of manganese carbonate ore, which mainly contains manganese and ammonia nitrogen and seriously damages the ecological environment. This work demonstrated the use of electrokinetic (EK) remediation to remove ammonia nitrogen and manganese from EMR. The transport behavior of manganese and ammonia nitrogen from EMR during electrokinetics, Mn fractionation before and after EK treatment, the relationship between Mn fractionation and transport behavior, as well as the effects of electrolyte and pretreatment solutions on removal efficiency and energy consumption were investigated. The results indicated that the use of H₂SO₄ and Na₂SO₄ as electrolytes and pretreatment of EMR with citric acid and KCl can reduce energy consumption, and the removal efficiencies of manganese and ammonia nitrogen were 27.5 and 94.1 %, respectively. In these systems, electromigration and electroosmosis were the main mechanisms of manganese and ammonia nitrogen transport. Moreover, ammonia nitrogen in EMR reached the regulated level, and the concentration of manganese in EMR could be reduced from 455 to 37 mg/L. In general, the electrokinetic remediation of EMR is a promising technology in the future.
Mostrar más [+] Menos [-]Effects of ambient and elevated CO2 on growth, chlorophyll fluorescence, photosynthetic pigments, antioxidants, and secondary metabolites of Catharanthus roseus (L.) G Don. grown under three different soil N levels
2015
Singh, Aradhana | Agrawal, Madhoolika
Catharanthus roseus L. plants were grown under ambient (375 ± 30 ppm) and elevated (560 ± 25 ppm) concentrations of atmospheric CO₂at different rates of N supply (without supplemental N, 0 kg N ha⁻¹; recommended N, 50 kg N ha⁻¹; and double recommended N, 100 kg N ha⁻¹) in open top chambers under field condition. Elevated CO₂significantly increased photosynthetic pigments, photosynthetic efficiency, and organic carbon content in leaves at recommended (RN) and double recommended N (DRN), while significantly decreased total nitrogen content in without supplemental N (WSN). Activities of superoxide dismutase, catalase, and ascorbate peroxidase were declined, while glutathione reductase, peroxidase, and phenylalanine-ammonia lyase were stimulated under elevated CO₂. However, the responses of the above enzymes were modified with different rates of N supply. Elevated CO₂significantly reduced superoxide production rate, hydrogen peroxide, and malondialdehyde contents in RN and DRN. Compared with ambient, total alkaloids content increased maximally at recommended level of N, while total phenolics in WSN under elevated CO₂. Elevated CO₂stimulated growth of plants by increasing plant height and numbers of branches and leaves, and the magnitude of increment were maximum in DRN. The study suggests that elevated CO₂has positively affected plants by increasing growth and alkaloids production and reducing the level of oxidative stress. However, the positive effects of elevated CO₂were comparatively lesser in plants grown under limited N availability than in moderate and higher N availability. Furthermore, the excess N supply in DRN has stimulated the growth but not the alkaloids production under elevated CO₂.
Mostrar más [+] Menos [-]Evaluation of variations and affecting factors of eco-environmental quality during urbanization
2015
Cui, Erqian | Ren, Lijun | Sun, Haoyu
Regional eco-environmental quality is the foundation of economic sustainable development and rational utilization of resources. It is necessary to understand and evaluate the regional eco-environmental quality correctly. Based on national remote sensing land use data, normalized difference vegetation index (NDVI) data and some other statistical data, this paper established an eco-environmental quality index (EQI) model to evaluate the ecological status of Jinan from 2000 to 2011. The results of eco-environmental quality showed little variation, with EQI values ranged from 62.00 to 69.01. EQI of each region in Jinan firstly decreased sharply and then increased slowly with the development of local economy. Besides the spatial and temporal variations analysis, affecting factors of eco-environmental quality was also discussed in this article. According to the results of correlation and regression analysis, meteorological conditions (rainfall and sunshine duration) and industrial structure (the proportion of primary industry) had relatively high correlations with eco-environmental quality. To summarize, a better eco-environmental status is associated with increasing rainfall, shorter sunshine duration, and lower proportion of primary industry. This article aims to giving supporting data and decision-making bases to restore the ecological environment and promote the sustainable development of Jinan.
Mostrar más [+] Menos [-]Using robust Bayesian network to estimate the residuals of fluoroquinolone antibiotic in soil
2015
Li, Xuewen | Xie, Yunfeng | Li, Lianfa | Yang, Xunfeng | Wang, Ning | Wang, Jinfeng
Prediction of antibiotic pollution and its consequences is difficult, due to the uncertainties and complexities associated with multiple related factors. This article employed domain knowledge and spatial data to construct a Bayesian network (BN) model to assess fluoroquinolone antibiotic (FQs) pollution in the soil of an intensive vegetable cultivation area. The results show: (1) The relationships between FQs pollution and contributory factors: Three factors (cultivation methods, crop rotations, and chicken manure types) were consistently identified as predictors in the topological structures of three FQs, indicating their importance in FQs pollution; deduced with domain knowledge, the cultivation methods are determined by the crop rotations, which require different nutrients (derived from the manure) according to different plant biomass. (2) The performance of BN model: The integrative robust Bayesian network model achieved the highest detection probability (pd) of high-risk and receiver operating characteristic (ROC) area, since it incorporates domain knowledge and model uncertainty. Our encouraging findings have implications for the use of BN as a robust approach to assessment of FQs pollution and for informing decisions on appropriate remedial measures.
Mostrar más [+] Menos [-]Phase ratio variation approach for the study of partitioning behavior of volatile organic compounds in polymer sample bags: Nalophan case study
2015
Van Durme, Jim | Werbrouck, Bas
Sorption of volatile organic compounds on the inner surface of polymer sampling bags leads to important underestimations of the real headspace concentration. Introducing a wide range of volatiles in a two-phase system containing Nalophan revealed that recoveries decreased down to 57 % in a period of 22 h. In this work, a phase ratio variation approach is investigated to quantify the degree of scalping, and thus enabling to compensate for sorption phenomena. This method requires limited measurements, without the need for time-consuming calibrations. By spiking identical amounts of volatiles in three two-phase systems, each having unique polymer volume/mass ratios β (β ₁ = 0, β ₂ = 80.9, β ₃ = 161.9), individual partitioning coefficients could be experimentally determined for a wide range of compounds. Additionally, a correlation was found between these partitioning coefficients and the liquid molar volume for a number of aliphatic, aromatic, and oxygenated compounds.
Mostrar más [+] Menos [-]Effects of flow speed and circulation interval on water quality and zooplankton in a pond–ditch circulation system
2015
Ma, Lin | He, Feng | Sun, Jian | Huang, Tao | Xu, Dong | Zhang, Yi | Wu, Zhenbin
A pond–ditch circulation system (PDCS) shows great promises for ecological restoration of rural contaminated water in southern China. In this study, the optimal flow speed, circulation interval, and their combination for the system were investigated for higher pollutant removal efficiency and lower costs in three separate experiments: I, II, and III, respectively. In each experiment, there are three PDCSs (S1, S2, and S3) with different water circulation speeds or circulation intervals, respectively. The results demonstrated that in experiment I, total nitrogen (TN) removal rates, species numbers, and diversity indexes of zooplankton in S1 with a flow speed of 3.6 L/h were significantly higher than those in S2 (7.2 L/h) and S3 (10.2 L/h), respectively. Similarly, in experiment II, S3 circulating every other 4 h had significantly higher TN reduction rates, species numbers, and diversity indexes than S1 and S2 circulating every other 1 and 2 h, respectively. In experiment III, water qualities in S1 (circulation of 3.6 L/h + interval of 4 h) were better than those in S2 (7.2 L/h + 4 h) and S3 (10.2 L/h + 6 h), respectively. Together, circulation at every other 4 h (3.6 L/h) is probably the optimal operating condition for the PDCS in remediating rural contaminated water.
Mostrar más [+] Menos [-]Combining UV-C treatment with biocontrol yeast to control postharvest decay of melon
2015
Huang, Ke | Zou, Yong | Luo, Jie | Liu, Yiqing
Significant losses in harvested melon can be directly attributable to decay fungi. In the present study, the use of UV-C treatment combined with biocontrol yeast, Pichia cecembensis, was evaluated for their ability to control postharvest decay of melon fruits after they were artificially inoculated with Fusarium oxysporum and Alternaria alternata. Natural infection of fruit was also assessed. As a stand-alone treatment, UV-C or P. cecembensis significantly reduced Fusarium rot and Alternaria rot, and also the level of natural infection on melon fruit, relative to the untreated control. The combination of UV-C or P. cecembensis, however, provided a superior level of decay control on artificially inoculated and naturally infected fruit, compared to either treatment alone. None of the treatments impaired fruit quality. Integrating the use of UV-C treatment with biocontrol yeast has potential as an effective method to control postharvest decay of melon.
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