Impact of injection system design on ISCO performance with permanganate--mathematical modeling results

In situ chemical oxidation (ISCO) using permanganate (MnO(4)(-)) can be a very effective technique for remediation of soil and groundwater contaminated with chlorinated solvents. However, many ISCO projects are less effective than desired because of poor delivery of the chemical reagents to the treatment zone. In this work, the numerical model RT3D was modified and applied to evaluate the effect of aquifer characteristics and injection system design on contact and treatment efficiency. MnO(4)(-) consumption was simulated assuming the natural oxidant demand (NOD) is composed of a fraction that reacts instantaneously and a fraction that slowly reacts following a 2nd order relationship where NOD consumption rate increases with increasing MnO(4)(-) concentration. MnO(4)(-) consumption by the contaminant was simulated as an instantaneous reaction. Simulation results indicate that the mass of permanganate and volume of water injected has the greatest impact on aquifer contact efficiency and contaminant treatment efficiency. Several small injection events are not expected to increase contact efficiency compared to a single large injection event, and can increase the amount of un-reacted MnO(4)(-) released down-gradient. High groundwater flow velocities can increase the fraction of aquifer contacted. Initial contaminant concentration and contaminant retardation factor have only a minor impact on volume contact efficiency. Aquifer heterogeneity can have both positive and negative impacts on remediation system performance, depending on the injection system design.     

Characteristics of cadmium tolerance in 'Hermes' flax seedlings: contribution of cell walls

Most flax (Linum usitatissimum) varieties are described as tolerant to high concentrations of Cd. The aim of the present paper was to better characterize this tolerance, by studying the responses of flax plantlets, cv Hermes, to 18d growth on 0.5mM Cd. In Cd-treated seedlings, the majority of Cd was compartmentalized in the roots. Analysis of other elements showed that only Fe concentration was reduced, while Mn increased. Growth parameters of Cd treated flax were only moderately altered, with similar mass tolerance-indices for roots and shoots. Tissue anatomy was unaffected by treatment. The effect on lipid peroxidation, protein carbonylation and antioxidative activities appeared low but slightly higher in roots. The most important impacts of Cd were, in all organs, cell expansion, cell-wall thickening, pectin cross-linking and increase of cell-wall enzymatic activities (pectin methylesterase and peroxidase). Thus, the role of the cell wall in Cd tolerance might be important at two levels: (i) in the reinforcement of the tissue cohesion and (ii) in the sequestration of Cd.     

Arsenic concentration in porewater of an alkaline coal ash disposal site: Roles of siderite precipitation/dissolution and soil cover

The geochemical behavior of As in porewaters of an alkaline coal ash disposal site was investigated using multilevel samplers. The disposal site was in operation from 1983 until 1994 and was covered with 0.3–0.5 m thick soils in 2001 when this study was initiated. Sequential extraction analyses and batch leaching experiments were also performed using the coal ash samples collected from the disposal site. The results suggest the important roles of siderite (FeCO₃) precipitation/dissolution and soil cover, which have been ignored previously. Arsenic levels in the porewater were very low (average of 10 μg L⁻¹) when the site was covered with soil due to coprecipitation with siderite. The soil cover enabled the creation of anoxic conditions, which raised the Fe concentration by the reductive dissolution of Fe-(hydr)oxides. Because of the high alkalinity generated from the alkaline coal ash, even a small increase in the Fe concentration (0.66 mg L⁻¹ on average) could cause siderite precipitation. When the soil cover was removed, however, an oxidizing condition was created and triggered the precipitation of dissolved Fe as (hydr)oxides. As a result, the dissolution of previously precipitated As-rich siderite caused higher As concentration in the porewater (average of 345 μg L⁻¹).     

Photocatalytic bacterial inactivation by polyoxometalates

The photocatalytic inactivation (PCI) of Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive) was performed using polyoxometalate (POM) as a homogeneous photocatalyst and compared with that of heterogeneous TiO₂ photocatalyst. Aqueous suspensions of the microorganisms (10⁷–10⁸ cfu ml⁻¹) and POM (or TiO₂) were irradiated with black light lamps. The POM-PCI was faster than (or comparable to) TiO₂-PCI under the experimental conditions employed in this study. The relative efficiency of POM-PCI was species-dependent. Among three POMs (H₃PW₁₂O₄₀, H₃PMo₁₂O₄₀, and H₄SiW₁₂O₄₀) tested in this study, the inactivation of E. coli was fastest with H₄SiW₁₂O₄₀ while that of B. subtilis was the most efficient with H₃PW₁₂O₄₀. Although the biocidal action of TiO₂ photocatalyst has been commonly ascribed to the role of photogenerated reactive oxygen species such as hydroxyl radicals and superoxides, the cell death mechanism with POM seems to be different from TiO₂-PCI. While TiO₂ caused the cell membrane disruption, POM did not induce the cell lysis. When methanol was added to the POM solution, not only the PCI of E. coli was enhanced (contrary to the case of TiO₂-PCI) but also the dark inactivation was observed. This was ascribed to the in situ production of formaldehyde from the oxidation of methanol. The interesting biocidal property of POM photocatalyst might be utilized as a potential disinfectant technology.     

Recent developments in Korea’s Framework Act on Resource Circulation: toward a resource-circulating society

Korea is moving toward a sustainable resource-circulating society to fight climate change and resource scarcity. To achieve this goal, the Framework Act on Resource Circulation (FRC) was enacted on May 29, 2016 and came into effect on January 1, 2018. This act not only acknowledges the importance of resource efficiency and the transition to a resource-circulating society, but also plays a significant role in the progress of important and relevant market and industry developments. This study primarily focuses on an analysis of the FRC. It aims to evaluate key concepts such as a resource-circulating society, circular resources, important provisions including major principles and allocation of responsibilities, and measures to be taken to promote resource circulation. In addition, it explores whether the FRC is sufficiently comprehensive and ambitious to contribute to the transition to a more resource-circulating society.     

Heavy metal removal by activated sludge: influence of Nocardia amarae.

The goal of this research was to examine the metal binding capacity of Nocardia amarae cells and to assess the influence of Nocardia cells on the overall metal binding capacity of activated sludge. Metal sorption capacities of the pure Nocardia cells and activated sludge biomass containing various levels of added Nocardia pure cultures were determined by a series of batch experiments. Batch sorption isotherms for nickel (Ni), copper (Cu), and cadmium (Cd) showed that the pure culture of N. amarae exhibited significantly higher metal sorption capacity than the activated sludge biomass obtained from Wilmington Wastewater Treatment Plant (Wilmington, DE). Surface area of biomass estimated by a dye technique showed that pure N. amarae cells growing at stationary phase have substantially more specific surface area than that of activated sludge from Wilmington Treatment Plant. A two-fold difference in specific surface area indicated that the higher metal sorption capacity of Nocardia cells may be due to the higher specific surface area. The metal sorption capacity of activated sludge increased proportionally with the amount of Nocardia cells present in the mixed liquor. This increase was attributed to the greater specific surface area of the mixed liquor samples containing greater amounts of Nocardia cells.     

Factors inhibiting bioremediation of soil contaminated with weathered oils and drill cuttings

Oily drill cuttings and a soil contaminated with weathered crude oils were treated by enhanced biodegradation under tropical conditions in industrial scaled experiments. Oil contaminants were characterized by gas chromatography and mass spectrometry. This allowed for the identification of a mixture of two crude oils in the contaminated soil. After 12 months of bioremediation process, the removal of hydrocarbons reached by biodegradation an extent of 60% although nutrient amendment with elevated concentration of N-urea had highly detrimental effects on the hydrocarbon degrading fungal populations due to the production of toxic concentration of ammonia gas by nitrification. The saturated hydrocarbons were extensively assimilated, though n-alkanes were not completely removed. Aromatic hydrocarbons were less degraded than saturated whereas resin and asphaltene fractions were, surprisingly, partly assimilated. In laboratory conditions, the residual hydrocarbons in the field-treated materials were 15-20% further degraded when metabolic byproducts resulting from biodegradation were diluted or removed.     

乌东德库区消落带土壤水分分布特征

消落带土壤水分是制约植物生长发育的关键因素,对库区消落带生态修复意义重大.本文系统分析了乌东德库区消落带修复试验区土壤含水量分布,探索了土壤水分空间变化和影响因素.结果表明:研究区5月水分含量低于5％,不同试验分区和高程区域土壤水分分布受到微地形、土壤特征、植被类型和植被覆盖度等影响.土壤水分随深度变化的主控因素包括地...     

Distribution,removal and chemical forms of heavy metals in polluted rice seed

In this paper, the distribution, removal and binding forms of heavy metals in polluted seeds of rice were studied using the methods of histochemistry and biochemistry. The results indicate that the distribution of heavy metals in rice grains was very uneven. The heavy metals in rice grains chiefly exist in association with the parts of high protein. Separation of proteins by Sephadex chromatography and subsequent analysis by atomic absorption spectroscopy revealed that Cd, Pb and As were mainly bound to protein of 54.5 and 5.50 kD molecular weights. During the rice processing, the concentrations of heavy metals in the edible rice decrease greatly, for some heavy metals in these parts of chaff, coarse rice bran and fine rice bran were removed.