Field-scale remediation of a metolachlor-contaminated spill site using zerovalent iron

Pesticide spills are common occurrences at agricultural cooperatives and farmsteads. When inadvertent spills occur, chemicals normally beneficial can become point sources of ground and surface water contamination. We report results from a field trial where approximately 765 m3 of soil from a metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] spill site was treated with zerovalent iron (Fe0). Preliminary laboratory experiments confirmed metolachlor dechlorination by Fe0 in aqueous solution and that this process could be accelerated by adding appropriate proportions of Al2(SO4)3 or acetic acid (CH3COOH). The field project was initiated by moving the stockpiled, contaminated soil into windrows using common earth-moving equipment. The soil was then mixed with water (0.35-0.40 kg H2O kg(-1)) and various combinations of 5% Fe0 (w/w),2% Al2(SO4)3 (w/w), and 0.5% acetic acid (v/w). Windrows were covered with clear plastic and incubated without additional mixing for 90 d. Approximately every 14 d, the plastic sheeting was removed for soil sampling and the surface of the windrows rewetted. Metolachlor concentrations were significantly reduced and varied among treatments. The addition of Fe0 alone decreased metolachlor concentration from 1789 to 504 mg kg(-1) within 90 d, whereas adding Fe0 with Al2(SO4)3 and CH3COOH decreased the concentration from 1402 to 13 mg kg(-1). These results provide evidence that zerovalent iron can be used for on-site, field-scale treatment of pesticide-contaminated soil.     

Evaluation of Lake Modification Alternatives for Lake Sihwa, Korea

After the construction of an embankment at the Bay of Sihwa in Korea, a lake of 56.5 km² surface area and 330 million m³ volume was created. Because of rapid socioenvironmental changes and the lowering of water quality in Lake Sihwa, various external measures have been proposed and some of them are being implemented. In this paper, we examine two alternatives for in-lake modification: one alternative is zoning of the lake by constructing two submerged dams and the other is channeling of the lake through reclamation. Water quality modeling was conducted for both alternatives to assess their effects. Results of the modeling revealed that the reduction of the lake size through two different approaches, when accompanied with other external measures, would improve the water quality, but to different degrees. The zonation is expected to improve the freshwater quality up to the level supplying 45 million m³ of water per year for agricultural use. The quality of channeled water would be inappropriate for agricultural use, but suitable for outdoor activities such as recreation or fishing regardless of reclamation plans considered.     

Development of effective hydrogen sulphide removing equipment using Thiobacillus sp.IW

Hydrogen sulphide is one of the commonest odours emitted by chemical plants. To remove the hydrogen sulphide biologically, a three phase fluidised bed bioreactor was used in which Thiobacillus sp.IW was immobilised on activated carbon. The optimum operating conditions of the bioreactor were 30 degrees C, pH7, aspect ratio (L/D) = 1 and at these conditions, the system removed over 94% of the hydrogen sulphide in the concentration range of 100-200 ppm and flow rate of 1.0-2.0 litre min(-1). From the upset and recovery test, the system proved stable within the moderate inlet concentration changes investigated.     

Synthesis of copolyesters containing poly(ethylene terephthalate) and poly(ε-caprolactone) units and their susceptibility toPseudomonas sp. lipase

Copolyesters containing poly(ethylene terephthalate) (PET) and poly(-caprolactone) (PCL) were synthesized from PET and PCL homopolymers by transesterification reaction at 270°C in the presence of catalyst. The copolyesters were characterized by¹³C-NMR and differential scanning calorimetry (DSC). The degradation behavior of PCL byPseudomonas sp. lipase in buffer solution (pH 7) and tetrahydrofuran (THF) was investigated by gel permeation chromatography (GPC) and¹H-NMR. From these experiments, it was found thatPseudomonas sp. lipase acted endoenzymatically on PCL. Using this lipase, degradation tests for PET/PCL copolyesters whose PCL content was below 50% by weight were also performed in buffer solution (pH 7). However, evenPseudomonas sp. lipase with high degradation activity on PCL did not easily degrade the PCL unit in PET/PCL copolyesters.     

Evaluation of CO exposure in active smokers while smoking using breath analysis technique

The current study evaluated the personal CO exposure of active smokers while smoking under controlled conditions, decay rate of CO in the body following active smoking, and CO accumulation in the body from repeated active smoking using a novel device for the direct measurement of alveolar breath CO. Prior to this evaluation, the proposed alveolar CO measurement device was successfully evaluated as regards the effect of humidity, CO recovery, carryover effect, and in comparison with the bag sampling method. The breath concentrations prior to and after a single cigarette were measured using a repeated measure design. Under the controlled conditions employed in the present study, active smoking was found to cause a significant body burden of CO. The post-exposure breath CO level was 1.6-2.0 times higher than the background breath level, depending on the subject and cigarette brand. In addition, the pre- and post-exposure breath concentrations were both significantly different among the subjects, yet the ratios of post-exposure to pre-exposure breath concentrations did not differ significantly between the different cigarette brands. The time-series alveolar breath concentrations measured following active smoking showed that the post-exposure alveolar CO concentrations decreased slowly even in the early phase of the decay curves, indicating a mono-compartment uptake and elimination model for the human body. The half-lives estimated in the present study (301, 315, and 385 min) were longer than or comparable to those in previous studies. The breath measurements prior to and after repeated active smoking exhibited a significant increasing trend for both the pre- and post-exposure concentrations. The changes in the pre- and post-exposure breath CO concentrations with repeated smoking ranged from 7% to 23% and from 10% to 15%, respectively, with half-hour intervals between cigarettes, and from 4% to 11% and from 6% to 8%, respectively, with hour intervals between cigarettes. Accordingly, most of the current results indicated that CO was accumulated in the human body with repeated active smoking.     

Evaluation of bioremediation effectiveness on crude oil-contaminated sand

A treatability study was conducted using sea sand spiked with 3% or 6% (w/w) of Arabian light crude oil to determine the most effective bioremediation strategies for different levels of contamination. The sea sand used in the study was composed of gravel (0.1%), sand (89.0%), and silt and clay (10.9%). The water content of the sea sand was adjusted to 12.6% (w/w) for the study. Different combinations of the following treatments were applied to the sand in biometer flasks: the concentration of oil (3% or 6%), the concentration of a mixture of three oil-degrading microorganisms (Corynebacterium sp. IC-10, Sphingomonas sp. KH3-2 and Yarrowia sp. 180, 1x10(6) or 1x10(8) cells g-1 sand), the concentration of the surfactant Tween 80 (1 or 10 times the critical micelle concentration), and the addition of SRIF in a C:N:P ratio of 100:10:3. Three biometer flasks per combination of experimental conditions were incubated, and the performance of each treatment was examined by monitoring CO2 evolution, microbial activity, and oil degradation rate. The results suggest that the addition of inorganic nutrients accelerated the rate of CO2 evolution by a factor of 10. The application of oil-degrading microorganisms in a concentration greater than that of the indigenous population clearly increased biodegradation efficiency. The application of surfactant slightly enhanced the oil degradation rate in the contaminated sand treated with the higher concentration of oil-degrading microorganisms. The initial CO2 evolution rate was shown to efficiently evaluate the treatability test by providing significant data within a short period, which is critical for the rapid determination of the appropriate bioremediation approach. The measurements of microbial activity and crude oil degradation also confirmed the validity of the CO2 evolution rate as an appropriate criterion.     

Forest-based biomass supply potential and economics for the pellet production in Nepal

In the current study, the potential of forest-based biomass supply for the pellet production in Nepal is investigated. This study showed that about 2.76 million tonnes (Mt) biomass in the form of pellets are potentially available from forest-based biomass. Considering a processing capacity of 6 tonnes (t)/hr of a pellet plant, the production cost of the pellets was calculated to be $43.53/t. Pellets are generally used as fuel to produce thermal energy in industries, which helps to save the economy and the environment of the country.     

The effect of suspended particles coated by humic acid on the toxicity of pharmaceuticals, estrogens, and phenolic compounds

The sorption characteristics of 10 organic chemicals, categorized as pharmaceuticals, estrogens and phenols, onto synthetic suspended particle (i.e., alumina) coated with humic acid were investigated according to their octanol-water partition coefficient (K(ow)). Chemical analyses were performed with gas chromatography and mass spectrometry (GC/MS) and high performance liquid chromatography (HPLC). The effects of particles on the toxicity reduction were evaluated using bioassay tests, using Daphnia magna and Vibrio fisheri for phenols and pharmaceuticals, and the human breast cancer cell MCF-7 for estrogens. Sorption studies revealed that 22 and 38% of octylphenol and pentachlorophenol, respectively, were removed by suspended particle, whereas 2,4-dichlorophenol was not removed, which was directly proportional to the logK(ow) value. Similar to the sorption tests, suspended particles significantly reduced the acute toxicities of octylphenol and pentachlorophenol to D. magna and V. fisheri (p<0.01), but there was no significant difference in the toxicity of 2,4-dichlorophenol to D. magna (p=0.8374). Pharmaceuticals, such as ibuprofen, gemfibrozil and tolfenamic acid, showed no discernible sorption to the suspended particle, with the exception of diclofenac, which revealed 11% sorption. For estrogens, such as estrone, 17beta-estradiol and 17alpha-ethynylestradiol, the results indicated no reduction in the sorption test. This may be attributed to the polar interaction by functional groups in sorption between pharmaceuticals and estrogens and suspended particles. In the bioassays, presence of suspended particles did not significantly modify the toxicity of pharmaceuticals (regardless of their K(ow) values) to D. magna, V. fisheri or E-screen.     

Removal characteristics of CO2 using aqueous MEA/AMP solutions in the absorption and regeneration process

The carbon dioxide (CO2) removal efficiency, reaction rate, and CO2 loading into aqueous blended monoethanolamine (MEA) + 2-amino-2-methyl-1-propanol (AMP) solutions to enhance absorption characteristics of MEA and AMP were carried out by the absorption/regeneration process. As a result, compared to aqueous MEA and AMP solutions, aqueous blended MEA+AMP solutions have a higher CO2 loading than MEA and a higher reaction rate than AMP. The CO2 loading of rich amine of aqueous 18 wt.% MEA+12 wt.% AMP solution was 0.62 mol CO2/mol amine, which is 51.2% more than 30 wt.% MEA (0.41 mol CO2/mol amine). Consequently, blending MEA and AMP could be an effective way to design cousidering economical efficiency and used to operate absorber for a long time.     

Salinity intrusion characteristics analysis using EFDC model in the downstream of Geum River

As social interest in the environmental conservation and ecological restoration has recently increased, more research works have been done to resolve problems concerning environmental management of estuaries. In this study, a three-dimensional numerical model, Environmental Fluid Dynamics Code (EFDC) was used in the analysis of the salinity intrusion characteristics in the downstream of Geum River. The numerical simulation was performed to investigate the influence range for salinity intrusion when the gates were fully opened. The conditions used for simulation were the four flow regimes in Geum River Basin, Korea. Results indicated that the ranges of salinity intrusion from the barrage were 50.72 km (drought flow), 48.87 km (low flow), 46.56 km (normal flow) and 42.10 km (flood flow). These results indicated that the EFDC model used for numerical simulation has high accuracy. The result concluded in this study can be used as a basis in understanding the extent of salinity intrusion e ects at di erent flow rates.