Impact of chemical leaching on permeability and cadmium removal from fine-grained soils

The aim of this study was to investigate the influence of chemical leaching on permeability and Cd removal from fine-grained polluted soils. Column leaching experiments were conducted using two types of soils (i.e., artificially Cd-polluted loam and historically polluted silty loam). Chemical agents of CaCl₂, FeCl₃, citric acid, EDTA, rhamnolipid, and deionized water were used to leach Cd from the soils. Results showed that organic agents reduced permeability of both soils, and FeCl₃ reduced permeability of loam soil, compared with inorganic agents and deionized water. Entrapment and deposition of colloids generated from the organic agents and FeCl₃ treatments reduced the soil permeability. The peak Cd effluence from the artificially polluted loam columns was retarded. For the artificially polluted soils treated with EDTA and the historically polluted soils with FeCl₃, Cd precipitates were observed at the bottom after chemical leaching. When Cd was associated with large colloid particles, the reduction of soil permeability caused Cd accumulation in deeper soil. In addition, the slow process of disintegration of soil clay during chemical leaching might result in the retardation of peak Cd effluence. These results suggest the need for caution when using chemical-leaching agents for Cd removal in fine-grained soils.

     

Facile Preparation of Chitosan Films for High Performance Removal of Reactive Blue 19 Dye from Aqueous Solution

This study aimed at finding effective strategies for high-performance removal of reactive blue 19 (RB19) dye from aqueous solution. Chitosan (CS) films had been prepared by using solvent casting with mild drying for this purpose. The CS films were characterized by X-ray diffraction, field-emission scanning electron microscopy, and Fourier transform infrared (FTIR) spectroscopy. The performance of RB19 removal using CS were evaluated by varying contact time, solution pH, initial dye concentration, and adsorbent dosage. Adsorption isotherms, kinetics, and desorption were investigated by batch experiments. Results showed that CS films exhibited the optimal adsorption performance for RB19 removal and high maximum adsorption capacities of RB19, which were 799 and 822.4 mg g^?1 at 20 and 40 °C, respectively. Adsorption kinetic data were well described by the pseudo-second-order kinetic model. FTIR analyses further indicated that interactions between RB19 and the CS film occurred during adsorption. The CS films also exhibited satisfactory desorption of RB19 at about 80 % after 30 min of desorption at pH 11. Our study demonstrated that the CS films can be easily prepared and applied for effective removal of RB19 in treatment of wastewater.     

Report on the fifth meeting of INRA’s national network of ecotoxicologists,ECOTOX

The fifth meeting of INRA’s national network of ecotoxicologists took place on 25 to 27 November 2014 in Biarritz, France. The main aim of the meeting was to bring together ecotoxicologists from INRA and associated partners, providing them ample opportunity to share and discuss their latest scientific results as well as the national policy of research in ecotoxicology and to precise perspectives for the network.     

Research on the experiment of the enhancement removal of fine sand by hydrocyclone in sewage treatment plant

The content of fine sand (< 200 μm) in primary sludge is relatively high in Chongqing sewage treatment plant owing to the part of rainwater will be mixed with sand and discharged into the municipal pipe network. Due to the insufficient separation of the sand, different obstacles to subsequent treatment processes may increase equipment wear, reduce effective volume of the tank, or shorten the cleaning cycle. There is a common use of grit chamber for the separation. Nevertheless, the use of hydrocyclone shows an outstanding performance in cost effectiveness and ease operation. The primary sludge in a sewage plant in Chongqing was monitored, and the average concentration of total suspend solids (TSS), total sand content, and volatile suspended solid (VSS) were 40.25 g/L, 17.51 g/L, and 13.41 g/L, respectively. The size of sand in the sludge was small, and the sand below 30 μm accounted for about 70% of the total sand. It formed flocs with organic matter and was removed in subsequent process units. While the size between 30–200 μm, called fine sand, was the main separation object, accounted for about 28.5%. According to XRF and XRD analysis, the sludge composition was mainly composed of quartz (SiO₂), plagioclase (Na(AlSi₃O₈)), and calcite (CaCO₃), which were similar to the main mineral composition of surface sediments and mountain rocks in the main urban area of Chongqing. A single-factor experiment on two types (FX100 and FX50) of hydrocylones was conducted to determine their abilities concerning the separation of fine sand and enrichment of organic matters from primary sludge. FX100 and FX50 showed best performance in the case of P = 0.17 Mpa, underflow diameter (Du) = 18 mm and P = 0.20 Mpa, Du = 6 mm, respectively. The removal efficiency of fine sand by hydrocyclone FX50 was 71.39%. While, it had poor performance on organic matter enrichment and the removal efficiency of which was 17.38%. By contrast, the removal rate by FX100 reached 61.89% for fine sand and only 6.89% for organic matters detached. The superimposition effect did not appear in the serial experiments on hydrocylone FX100 and FX50, but the power is 3.5 times of that of single-stage hydrocylone FX100. Comprehensive consideration of the processing capacity per unit time and operating power, the hydrocylone FX100 was more suitable for actual operation.

     

The influence of low-dose cadmium on the laryngeal microstructure and ultrastructure of Pelophylax nigromaculata

Environmental Science and Pollution Research - Cadmium (Cd) is one of the common heavy metals dispersed throughout the modern environment that disrupts the development of aquatic organisms....     

The temporal stability and developmental differences in the environmental impacts of militarism: the treadmill of destruction and consumption-based carbon emissions

This study examines the relationship between national-level militarism and consumption-based carbon dioxide emissions. We analyze panel data from 1990 to 2010 for 81 nations to determine whether the magnitude of the effects of (1) military expenditures as percent of total gross domestic product and (2) military personnel as percent of total labor force on carbon emissions change over time. Results of two-way fixed effects models highlight the temporal stability of the environmental impacts of both national-level military characteristics. The findings also reveal that the effect of military expenditures on emissions is larger in the more developed OECD nations than in the developing non-OECD nations. Overall, the results support the treadmill of destruction perspective, which suggests that the nations’ militaries are an important social institution to consider in sustainability science research on the human drivers of global environmental change.     

Carbon dioxide emissions,output, and energy consumption categories in Algeria

This study examines the relation between CO₂ emissions, income, non-renewable, and renewable energy consumption in Algeria during the period extending from 1980 to 2011. Our work gives particular attention to the validity of environmental Kuznets curve (EKC) hypothesis. The autoregressive distributed lag (ARDL) with break point method outcome demonstrates the positive effect of non-renewable type of energy on CO₂ emissions consumption. On the contrary, the results reveal an insignificant effect of renewable energy on environment improvement. Moreover, the results accept the existence of EKC hypothesis but the highest gross domestic product value in logarithm scale of our data is inferior to the estimated turning point. Consequently, policy-makers in Algeria should expand the ratio of renewable energy and should decrease the quota of non-renewable energy consumption.     

Optimal Policy Mechanism Design for Cross-Sector and Multi-Stage Pollution Control with a Bilevel Model: Application to SO<Subscript>2</Subscript> Emission in China

In this paper, we construct a multi-stage coordinated programming model under tax system to control SO₂ emission. The model is based on an explicitly formulated SO₂ abatement cost function created under Chinese condition. Analysis of the effectiveness and impact on the economy of the model is carried out with consideration of game theory. By solving the model, theoretical results show that the volume-based multi-stage SO₂ tax system has two properties: effectiveness and equal-rate. Based on these theoretical results, empirical study is also performed using Chinese historical data. Compared with yearly single-stage programming model, the tax rate generated by the coordinated multi-stage programming model is time-invariant and rather moderate in scale. The total abatement cost among planning years in our model is 21.03 % less than the actual number and 6.68 % less than that in the single-stage situation. The tax payment suggested by our model is 10.62 % less than by the single-stage model. In general, a coordinated multi-stage programming model helps reduce the overall costs of environmental protection while achieving the same emission control target with less burden added to the economy.