Monitoring of selected veterinary antibiotics in environmental compartments near a composting facility in Gangwon Province, Korea

Many studies have been recently reported that veterinary antibiotics released into the environment have a detrimental effect on humans such as the occurrence of antibiotic-resistant bacteria. However, only limited information is available regarding to the release of antibiotics in environmental compartments in Korea. Objectives of this study were to evaluate the concentrations of antibiotics in water, sediment, and soil adjacent to a composting facility in Korea and to determine the dilution effects of antibiotics when released into the environment. Seven antibiotics of chlortetracycline, oxytetracycline, tetracycline, sulfamethazine, sulfamethoxazole, sulfathiazole, and tylosin were evaluated by high-performance liquid chromatography?Ctandem mass spectrometry following pretreatment using solid-phase extraction to clean the samples. Results showed that the highest concentration of each antibiotic in both aqueous and solid samples was detected from a site adjacent to the composting facility. We also found that the studied water, sediment, and soil samples are contaminated by veterinary antibiotics throughout comparison with studies from other countries. However, relatively lower concentrations of each antibiotic were observed from the rice paddy soil located at the bottom of the water stream. Further research is necessary to continuously monitor the antibiotics release into ecosystems, thereby developing an environmental risk assessment.     

Nitrogen oxides emissions from the MILD combustion with the conditions of recirculation gas

The nitrogen oxides (NO_x) reduction technology by combustion modification which has economic benefits as a method of controlling NO_x emitted in the combustion process, has recently been receiving a lot of attention. Especially, the moderate or intense low oxygen dilution (MILD) combustion which applied high temperature flue gas recirculation has been confirmed for its effectiveness with regard to solid fuel as well. MILD combustion is affected by the flue gas recirculation ratio and the composition of recirculation gas, so its NO_x reduction efficiency is determined by them. In order to investigate the influence of factors which determine the reduction efficiency of NO_x in MILD coal combustion, this study changed the flow rate and concentration of nitrogen (N₂), carbon dioxide (CO₂) and steam (H₂O) which simulate the recirculation gas during the MILD coal combustion using our lab-scale drop tube furnace and performed the combustion experiment. As a result, its influence by the composition of recirculation gas was insignificant and it was shown that flue gas recirculation ratio influences the change of NO_x concentration greatly. Implications: We investigated the influence of factors determining the nitrogen oxides (NO_x) reduction efficiency in MILD coal combustion, which applied high-temperature flue gas recirculation. Using a lab-scale drop tube furnace and simulated recirculation gas, we conducted combustion testing changing the recirculation gas conditions. We found that the flue gas recirculation ratio influences the reduction of NO_x emissions the most.     

Oxidative damage induced in hearts, kidneys and spleens of mice by landfill leachate

The effects of the Xingou landfill leachate on levels of thiobarbituric acid reactive substances (TBARS) and the activities of Cu, Zn-superoxide dismutase (Cu, Zn-SOD), Se-dependent glutathione peroxidase (Se-dependent GPx) and catalase (CAT) were investigated in hearts, kidneys and spleens of Kunming albino mice of both sexes. Exposure to leachate caused significant increases of TBARS levels in the organs tested from mice of both sexes. For hearts, Cu, Zn-SOD, Se-dependent GPx and CAT activities were significantly increased at high concentrations for male mice, but the activities of these antioxidant enzymes were significantly increased at low concentration and decreased at high concentrations for female mice. For kidneys, Cu, Zn-SOD and Se-dependent GPx activities were significantly increased at high concentrations for male mice, but the activities were significantly increased at low concentrations and the ratio of increase was reduced with the increasing of concentration for female mice; CAT activities remained unchanged for male mice and were significantly increased at all concentrations tested for female mice. For spleens, Cu, Zn-SOD and Se-dependent GPx activities were significantly increased at high concentrations for male mice, but the activities were significantly increased at low concentrations and decreased at high concentrations for female mice; CAT activities remained unchanged for male mice and were significantly increased at high concentrations for female mice. The results suggest that leachate exposure can cause oxidative damage on hearts, kidneys and spleens of mice, and there were sex difference and organ difference in the response of antioxidant status.     

Combined toxicity of copper and phenol derivatives to Daphnia magna: effect of complexation reaction

The complexation of Cu with phenol was investigated in aqueous solution to find the changes in toxicity toward Daphnia magna in mixtures of copper and phenol derivatives and determine an appropriate prediction model for the toxicity of these mixtures. In the titration experiment, the results showed that phenol played an important role in the remarkable reduction of the Cu(2+) concentration, due to its complexation with Cu, with the subsequent reduction in the toxicity of aqueous mixtures containing both Cu and phenol. As a result, it was clearly demonstrated that Cu-phenol formed a non-toxic complex toward D. magna as the mortality declined, despite the addition of phenol to a fixed Cu concentration. Meanwhile, prediction of the combined toxicity for binary mixtures of Cu and 11 phenol derivatives more accurately followed an independent action model (p = 0.143, df = 124, and t = -1.475 in t-test) than an effect summation model (p approximately 0, df = 134, and t = 7.528 in t-test) due to the dissimilar modes of action and the complexation reactions between Cu and each of the phenolic compounds. Consequently, this study supports the importance of considering complexation reactions in assessing the combined toxicity for the formulation of water quality in mixtures of heavy metals and organic compounds, and in these cases, an independent action model was found to be appropriate.     

某卷烟厂卷接机组集中风力与除尘系统的应用

结合贵州某卷烟厂技术改造实践，采用集中工艺风力和除尘技术，对PASSIM和SUPER9卷接机组的工艺风力供给方式和除尘系统进行了改进。对于系统的结构、可靠性、调节性、稳定性进行了分析，改造后集中风力系统较常规风力系统在经济效益和工作环境上具有显著优势，降低了运行成本。     

Vertical distribution and characteristics of soil humic substances affecting radionuclide distribution

The humic substances extracted from different soil depths are separated into humic (HA) and fulvic (FA) acids, and characterized for their chemical composition, proton exchange capacity, spectroscopic characteristics and binding properties to the europium ion. The chemical and spectroscopic results show that FA compared to HA has a relatively high O/C ratio, high acidic functional group contents and low aromatic contents. The synchronous fluorescence spectroscopic results show that the stability constant (K) of the soil humic substances with Eu(III) ion tends to increase as the soil depth becomes deeper, and HA has a slightly stronger binding ability than FA. The measured total site concentrations (C(L)) reveal that Eu(III) ion is loaded onto HA by 62-77% of the total acid sites, but FA is only approximately 50% covered by Eu(III) ion. Information could be useful in understanding the migration of radionuclides in soil layer.     

Effect of complex nitrogen source on the synthesis and accumulation of poly(3-hydroxybutyric acid) by recombinantEscherichia coli in flask and fed-batch cultures

When a recombinantEscherichia coli XL1-Blue harboring pSYL105 was cultured in a complex medium, a poly(3-hydroxybutyric acid) (PHB) concentration of 7.16 g/L was obtained in 48 h. However, a PHB concentration of only 0.91 g/L was obtained in 60 h by culturing in a defined medium. Also, fed-batch culture in a defined medium resulted in considerably lower PHB accumulation than in a complex medium. With the aim to produce a high concentration of PHB at a reduced medium cost, we examined 10 complex nitrogen sources for their ability to promote PHB synthesis in a defined medium. Tryptone, casamino acids, and casein hydrolysate promoted PHB synthesis to a higher extent than the others tested. PHB synthesis was also enhanced during fedbatch cultures when a defined medium was supplemented with various complex nitrogen sources. With tryptone supplementation a PHB concentration of 66.7 g/L could be obtained in 44 h. Yeast extract was less effective for promoting PHB synthesis than tryptone. Corn steep liquor, which did not enhance PHB synthesis significantly, could promote PHB synthesis considerably when supplemented together with yeast extract in both flask and fed-batch cultures.     

黏性颗粒在滤料表面沉积的动态模拟及规律

为研究颗粒黏性对过滤除尘性能的影响,分析了颗粒沉积过程的受力情况,应用颗粒流计算软件PFC2D对颗粒在滤料表面的沉积行为进行了数值模拟。结果表明:颗粒形成粉尘层的过程中主要受到风流力、惯性力等压缩力和范德华力、滚动摩擦力偶矩等压缩阻力的作用,颗粒黏性的增加,会使颗粒间滚阻系数和摩擦系数显著增加;PFC可实现粉尘颗粒在滤料表面沉积过程的可视化,得到不同黏性颗粒在滤料表面的沉积形态,滚阻系数或摩擦系数越大,粉尘层孔隙率越大,过滤阻力越小,其中,摩擦系数的影响作用弱于滚阻系数。     

Modeling the impacts of temperature and precipitation changes on soil CO2 fluxes from a Switchgrass stand recently converted from cropland

Switchgrass(Panicum virgatum L.) is a perennial C_4 grass native to North America and successfully adapted to diverse environmental conditions. It offers the potential to reduce soil surface carbon dioxide(CO_2) fluxes and mitigate climate change. However, information on how these CO_2 fluxes respond to changing climate is still lacking. In this study, CO_2 fluxes were monitored continuously from 2011 through 2014 using high frequency measurements from Switchgrass land seeded in 2008 on an experimental site that has been previously used for soybean(Glycine max L.) in South Dakota, USA. DAYCENT, a process-based model, was used to simulate CO_2 fluxes. An improved methodology CPTE[Combining Parameter estimation(PEST) with "Trial and Error" method] was used to calibrate DAYCENT. The calibrated DAYCENT model was used for simulating future CO_2 emissions based on different climate change scenarios. This study showed that:(i) the measured soil CO_2 fluxes from Switchgrass land were higher for 2012 which was a drought year, and these fluxes when simulated using DAYCENT for long-term(2015–2070) provided a pattern of polynomial curve;(ii) the simulated CO_2 fluxes provided different patterns with temperature and precipitation changes in a long-term,(iii) the future CO_2 fluxes from Switchgrass land under different changing climate scenarios were not significantly different, therefore, it can be concluded that Switchgrass grown for longer durations could reduce changes in CO_2 fluxes from soil as a result of temperature and precipitation changes to some extent.     

Fuel cell system with sodium borohydride hydrogen generator for small unmanned aerial vehicles

A 100 W proton exchange membrane fuel cell (PEMFC) system with a sodium borohydride (NaBH₄) hydrogen generator was investigated for small unmanned aerial vehicles (UAVs). The performance of a cobalt–phosphorous/nickel foam catalyst was evaluated to determine the change in catalytic activity under real operating conditions. The response time increased owing to oxidation of the metals and accumulation of sodium; however, the catalyst remained active at high reaction temperatures. A NaBH₄ hydrogen generator with the catalyst was developed for a 100 W PEMFC system. The hydrogen generation rate was stable for 3 h, and the conversion efficiency was 97.8%. Finally, a 100 W PEMFC system with the NaBH₄ hydrogen generator was investigated for small UAVs. The maximum power and energy density of the PEMFC system were 95.96 W and 185.2 Wh/kg, respectively.