香港及珠三角地区MODIS高分辨率气溶胶光学厚度的反演

为了有效解决地区性和城市范围内的气溶胶分布并反演陆地上气溶胶的性质,一种针对中分辨率成像光谱辐射计(MODIS)的气溶胶反演新算法应运而生.本文首先通过改良的最小反射率技术(MRT)来确定季节性的地表反射率和利用瑞利通道辐射率中解析出大气上气溶胶的反射率来估计气溶胶的反射系数.结果表明,MRT地表反射率的图像和MODIS地表反射系数的产品(MOD09)有很好的契合度.两者的相关系数高达0.9.此外,考虑到不同气溶胶的光学性质和太阳观测组合对计算辐射传输的影响,本研究还制定了全面广泛的差算表(LUT).由此产生的卫星500m分辨率的气溶胶光学厚度(AOT)和香港太阳光度计(AERONET)及MicrotopsⅡ观测资料的相关系数r分别为0.96和0.87(相伴概率值P<0.0001).该研究证明了城区高分辨率气溶胶反演的可行性,还能帮助研究气溶胶的分布和城区大气瞬态污染的影响.此外,MODIS 500m分辨率的气溶胶光学厚度图像还可用于研究跨境气溶胶,使定位珠江三角洲区域污染源变得可行.     

Effects of a dynamic membrane formed with polyethylene glycol on the ultrafiltration of natural organic matter

The formation of a dynamic membrane (DM) was investigated using polyethylene glycol (PEG) (molecular weight of 35000 g/mol, concentration of 1 g/L). Two natural organic matters (NOM), Dongbok Lake NOM (DLNOM) and Suwannee River NOM (SRNOM) were used in the ultrafiltration experiments along with PEG. To evaluate the effects of the DM with PEG on ultrafiltration, various transport experiments were conducted, and the analyses of the NOM in the membrane feed and permeate were performed using high performance size exclusion chromatography, and the effective pore size distribution (effective PSD) and effective molecular weight cut off (effective MWCO) were determined. The advantages of DM formed with PEG can be summarized as follows: (1) PEG interferes with NOM transmission through the ultrafiltration membrane pores by increasing the retention coefficient of NOM in UF membranes, and (2) low removal of NOM by the DM is affected by external factors, such as pressure increases during UF membrane filtration, which decreases the effective PSD and effective MWCO of UF membranes. However, a disadvantage of the DM with PEG was severe flux decline; thus, one must be mindful of both the positive and negative influences of the DM when optimizing the UF performance of the membrane.     

Effect of biogeochemical interactions on bioaccessibility of arsenic in soils of a former smelter site in Republic of Korea

The total concentration-based regulations for soil remediation do not consider the possible changes in bioaccessibility of remaining arsenic (As) in soils due to biogeochemical interactions after remediation. This study used As-contaminated soil and pore water samples that were collected from the rice paddy and forest/farmland located in the vicinity of a former smelter site in Republic of Korea to elucidate the changes in As bioaccessibility due to biogeochemical interactions. Bioaccessibility and chemical forms of As in soils were determined by using an in vitro method and sequential extraction, respectively, and soil microbial community was evaluated. Bioaccessibility of As in the rice paddy soil samples was higher than that in the forest/farmland soil samples. This could be attributed to relatively higher dependence of bioaccessible As in the rice paddy soils on the soil concentration of iron (Fe), aluminum, or manganese, which could lead to greater changes in bioaccessible As via reductive dissolution. The strong linear relationship (R ² = 0.90, p value ≤0.001) between the pore water As and Fe concentrations, and the greater portion of bacterial species related to reductive dissolution of Fe oxides in the rice paddies can support the higher As bioaccessibility promoted by reductive dissolution. Therefore, it is necessary to consider the potential changes in the bioaccessible As due to biogeochemical interactions in remediation of As-contaminated soils, particularly when soils are likely to be reused under reductive dissolution-promoting conditions (e.g., flooded conditions).     

Physiological responses of Cladophora glomerata to cyanotoxins: a potential new phytoremediation species for the Green Liver Systems

Due to increased pollution of potable water sources as a consequence of eutrophication and anthropogenic xenobiotics, sustainable water purification is an essential concern. Therefore, the Green Liver System, a natural, economic and sustainable water purification system employing the biotransformation capabilities of aquatic plants, was developed. To expand the capacities and applications of this system, new aquatic plants are continually evaluated for their potential to remediate various aquatic pollutants. In this study, the potential of Cladophora glomerata to internalize cyanotoxins, microcystins (MCs) and anatoxin-a, and consequently its ability to cope with the subsequent oxidative stress associated with toxin-uptake were investigated. C. glomerata was able to take up all three of the tested MC congeners as well as anatoxin-a, similarly to previous toxin internalizations reported for aquatic plants such as Ceratophyllum demersum, Myriophyllum spicatum and Hydrilla versiculata. The antioxidative stress defense of C. glomerata proved to efficiently endure the toxin-uptake with no adverse effects. Subsequently, the uptake potential of C. glomerata was investigated at lab-scale by exposure to the three MC congeners and anatoxin-a collectively. After a period of seven days, 95–97% of the MCs and 100% of anatoxin-a were removed from the exposure media. C. glomerata therefore, is a suitable candidate to be incorporated in future Green Liver Systems.     

Life cycle assessment of low impact development technologies combined with conventional centralized water systems for the City of Atlanta,Georgia

Low-impact development (LID) technologies, such as bioretention areas, rooftop rainwater harvesting, and xeriscaping can control stormwater runoff, supply non-potable water, and landscape open space. This study examines a hybrid system (HS) that combines LID technologies with a centralized water system to lessen the burden on a conventional system (CS). CS is defined as the stormwater collection and water supply infrastructure, and the conventional landscaping choices in the City of Atlanta. The study scope is limited to five single-family residential zones (SFZs), classified R-1 through R-5, and four multi-family residential zones (MFZs), classified RG-2 through RG-5. Population density increases from 0.4 (R-1) to 62.2 (RG-5) persons per 1,000 m2. We performed a life cycle assessment (LCA) comparison of CS and HS using TRACI 2.1 to simulate impacts on the ecosystem, human health, and natural resources.We quantified the impact of freshwater consumption using the freshwater ecosystem impact (FEI) indicator. Test results indicate that HS has a higher LCA single score than CS in zones with a low population density; however, the difference becomes negligible as population density increases. Incorporating LID in SFZs and MFZs can reduce potable water use by an average of 50% and 25%, respectively; however, water savings are negligible in zones with high population density (i.e., RG-5) due to the diminished surface area per capita available for LID technologies. The results demonstrate that LID technologies effectively reduce outdoor water demand and therefore would be a good choice to decrease the water consumption impact in the City of Atlanta.

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Comparison of metabolic nitramine degradation by denitrifying species

The biodegradation of two popular nitramine energetics were investigated. The HMX (octa‐hydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine) was mineralized by anaerobic mixed denitrifiers in digested sewage sludge culture. An initial HMX concentration of 120 mg/L decreased to a non‐detectable level (> 99% removal efficiency) in 8 days of incubation under strict anaerobic conditions. It was, however, not effectively metabolized by single denitrifying species, P. aeruginosa, B. subtilis in a nitrogen limiting condition under their optimum growth conditions. The other nitramine energetic, ADN (ammonium dinitramide), was mineralized well in the anaerobic mixed culture. The initial ADN concentration of 250 mg/L was reduced to non‐detectable levels (> 99% removal efficiency) in 5 days of incubation under anaerobic conditions. These results show that the anaerobic mixed culture, compared to the pure monoculture, is superior in the degradation of nitramine energetics.     

Evaluation of Korean recycled aggregates as backfilling underground power system considering particle breakage effect

Journal of Material Cycles and Waste Management - Attempts have been made to address the strict regulations on eco-friendly construction and recycle aggregate resources, encouraging researchers to...     

Determination of soil contamination sources in mining area using Zn/Cd ratios with mobile Cd

Environmental Geochemistry and Health - Paddy fields near metalliferous mining area are sometimes contaminated by tailings or mine water. In the contaminated paddy fields around the abandoned...     

Effects of SO<Subscript>2</Subscript> contamination on rising CO<Subscript>2</Subscript> drops under high pressure

Although the flow dynamics of pure liquid drops in other liquids has been well researched, little attention has been paid to the impacts of impurities. Hence, most of research is not directly applicable to the real world. To address this gap, we conducted numerical experiments simulating the rise of pure and contaminated drops. It was selected to study liquid CO₂ drops contaminated with SO₂ under high pressure because such mixtures mimic potential scenarios in which drops may leak from carbon capture and storage (CCS) facilities or pipelines. First, numerical simulation experiments were performed to validate our method by comparing our results with previous research on pure drops. Second, the validated numerical approach was applied to simulations of contaminated drops to investigate how contaminants affect rising drops. The results show that the SO₂ contamination caused changes in deformation, breakup phenomena, rising velocities, surrounding flow fields and drag coefficients. Most importantly, the contamination resulted in the formation of smaller “child drops”; such breakup is not observed in pure CO₂ drops. The formation of child drops in turn affects the streamlines, patterns and areas of wakes behind the contaminated drops. The addition of contaminants also enhances the dissolution rate, which is affected by the contaminant concentration and by the flow dynamics of the rising drop. Our results would improve understanding the rise of impure CO₂ drops, such as drops potentially leaked by future CCS operations.     

Leaching studies for tin recovery from waste e-scrap

Printed circuit boards (PCBs) are the most essential components of all electrical and electronic equipments, which contain noteworthy quantity of metals, some of which are toxic to life and all of which are valuable resources. Therefore, recycling of PCBs is necessary for the safe disposal/utilization of these metals. Present paper is a part of developing Indo-Korean recycling technique consists of organic swelling pre-treatment technique for the liberation of thin layer of metallic sheet and the treatment of epoxy resin to remove/recover toxic soldering material. To optimize the parameters required for recovery of tin from waste PCBs, initially the bench scale studies were carried out using fresh solder (containing 52.6% Sn and 47.3% Pb) varying the acid concentration, temperature, mixing time and pulp density. The experimental data indicate that 95.79% of tin was leached out from solder material using 5.5M HCl at fixed pulp density 50g/L and temperature 90°C in mixing time 165min. Kinetic studies followed the chemical reaction controlled dense constant size cylindrical particles with activation energy of 117.68kJ/mol. However, 97.79% of tin was found to be leached out from solder materials of liberated swelled epoxy resin using 4.5M HCl at 90°C, mixing time 60min and pulp density 50g/L. From the leach liquor of solder materials of epoxy resin, the precipitate of sodium stannate as value added product was obtained at pH 1.9. The Pb from the leach residue was removed by using 0.1M nitric acid at 90°C in mixing time 45min and pulp density 10g/L. The metal free epoxy resin could be disposed-of safely/used as filling material without affecting the environment.