Preparation and Characterization of Hydrogel Based on Poly(vinyl alcohol) Cross-Linked by Different Cross-Linkers Used to Dry Organic Solvents

Poly(vinyl alcohol) (PVA) hydrogels were chemically cross-linked with/without different cross-linkers such as glutaraldehyde and epichlorohydrin, in the presence of a catalyst, or activator (potassium hydroxide) to produce three types of hydrogels. The structures of PVA and the prepared gel types were determined by FTIR spectroscopy, the mechanical and thermal properties, of these hydrogels were examined. The effects of different pH values and temperatures on the swelling properties of the prepared gels were examined. From the obtained results, it was found that, the low concentration of the cross-linker produced hydrogel with moderate properties, but in absence of the cross-linker, the obtained hydrogel exhibited good properties and can be used as friendly environmentally moisture absorbents from the organic solvents. The insolubility and swelling properties of gels were tested in these solvents. The results indicated that these hydrogels can be used as moisture absorbents and solvent dryers.     

Purification and Properties of Extracellular Poly(3-hydroxybutyrate) Depolymerase Produced by <Emphasis Type="Italic">Aspergillus fumigatus</Emphasis> 202

An extracellular poly(3-hydroxybutyrate) (PHB) depolymerase produced by a thermotolerant fungal soil isolate, Aspergillus fumigatus 202, was purified and characterized. Maximum PHB depolymerase production was obtained at the end of 48 h with initial medium pH 7.0 and 45 °C in Bushnell Haas Minerals medium containing PHB as sole source of carbon. The PHB depolymerase was purified using size exclusion chromatography to a fold purification of 20.62 and 61.62% yield. SDS-PAGE and isoelectric focusing revealed the molecular weight and pI of the purified enzyme as 63,744 Da and 4.2, respectively. N-terminal amino acid sequence of purified enzyme was HAXDAYLVK. This non-glycosylated enzyme was most active at pH 9.0 and 45 °C. Purified enzyme was inactivated by N-bromosuccinimide and dithiothreitol suggesting the involvement of tryptophan residues and disulfide bonds at its active site. Nonionic detergents like Tween 20, Tween 80 and Triton X-100 inhibited the enzyme activity. Ions like Ca⁺² and Mg⁺² (5 mM) increased the enzyme activity 1.5 times. Fe⁺² effectively inhibited the enzyme activity to 88% whereas Hg⁺² completely inhibited the enzyme.     

Monitoring Regional Riparian Forest Cover Change Using Stratified Sampling and Multiresolution Imagery1

Claggett, Peter R., Judy A. Okay, and Stephen V. Stehman, 2010. Monitoring Regional Riparian Forest Cover Change Using Stratified Sampling and Multiresolution Imagery. Journal of the American Water Resources Association (JAWRA) 46(2):334-343. DOI: 10.1111/j.1752-1688.2010.00424.x Abstract: The Chesapeake Bay watershed encompasses 165,760 km² of land area with 464,098 km of rivers and streams. As part of the Chesapeake Bay restoration effort, state and federal partners have committed to restoring 26,000 miles (41,843 km) of riparian forest buffers. Monitoring trends in riparian forest buffers over large areas is necessary to evaluate the efficacy of these restoration efforts. A sampling approach for estimating change in riparian forest cover from 1993/1994 to 2005 was developed and implemented in Anne Arundel County, Maryland, to exemplify a method that could be applied throughout the Bay watershed. All stream reaches in the county were stratified using forest cover change derived from Landsat imagery. A stratified random sample of 219 reaches was selected and forest cover change within the riparian buffer of each sampled reach was interpreted from high-resolution aerial photography. The estimated footprint of gross change in riparian forest cover (i.e., the sum of gross gain and gross loss) for the county was 1.83% (SE = 0.22%). Stratified sampling taking advantage of a priori knowledge of locations of change proved to be a practical and efficient protocol for estimating riparian forest buffer change at the county scale and the protocol would readily extend to much broader scale monitoring.     

Aerosol speciation and mass prediction from toluene oxidation under high NOx conditions

A kinetically based gas-particle partitioning box model is used to highlight the importance of parameter representation in the prediction of secondary organic aerosol (SOA) formation following the photo-oxidation of toluene. The model is initialized using experimental data from York University's indoor smog chamber and provides a prediction of the total aerosol yield and speciation. A series of model sensitivity experiments were performed to study the aerosol speciation and mass prediction under high NO_x conditions (VOC/NO_x = 0.2). Sensitivity experiments indicate vapour pressure estimation to be a large area of weakness in predicting aerosol mass, creating an average total error range of 70 μg m^?3 (range of 5–145 μg m^?3), using two different estimation methods. Aerosol speciation proved relatively insensitive to changes in vapour pressure. One species, 3-methyl-6-nitro-catechol, dominated the aerosol phase regardless of the vapour pressure parameterization used and comprised 73–88% of the aerosol by mass. The dominance is associated with the large concentration of 3-methyl-6-nitro-catechol in the gas-phase. The high NO_x initial conditions of this study suggests that the predominance of 3-methyl-6-nitro-catechol likely results from the cresol-forming branch in the Master Chemical Mechanism taking a significant role in secondary organic aerosol formation under high NO_x conditions. Further research into the yields and speciation leading to this reaction product is recommended.     

Quantifying trace gas emissions from composite landscapes: A mass-budget approach with aircraft measurements

Quantifying trace gas emissions and the influence of surface exchange processes on the atmosphere is a necessary step towards the control of global greenhouse gas emissions and reliability of air quality models. This paper proposes a procedure based on the mass balance method and implemented on highly resolved aircraft data. It allows one to estimate surface exchanges on areas of several km² and heterogeneous features exploiting the characteristics of convective boundary layer during steady state conditions that permit the estimation of emission/absorption terms as functions of advective fluxes only. A nonparametric approach is adopted and the fluxes on the surface of a virtual box surrounding the area of interest are reconstructed on the basis of scalar densities and wind vectors using Shepard functions. Two different techniques are also proposed to face lack of data on the top surface of the box. The method has been applied to experimental data coming from measurement campaigns on two different sites. It provides realistic estimates of the CO₂ emission/absorption in the considered areas that are in good agreement with CO₂ fluxes evaluated by Airborne Eddy Covariance and confirm the suitability of the proposed approach for the assessment of turbulent exchange of trace gases by composite landscapes. Uncertainties on the estimated emissions due to both propagation of the experimental error and interpolation have been quantified by bootstrap analysis as 6%.     

基于GIS的景观生态功能指标分析

针对当前我国规划及战略环评指标体系中缺乏直接反映生态功能指标的问题,提出可通过系统研究区域景观生态结构与景观功能变化间的关系,由斑块面积指数计算生物生产力、由景观香农多样性指数和景观香农均匀度指数反映生态质量,以此表征景观生态功能。以地理信息系统（GIS）为平台,提出了利用基于斑块面积而得到的景观要素转移矩阵及基于年鉴统计而得到的景观单位面积生物生产力的转移矩阵来计算生物生产力的方法,并在统计若干研究流域景观格局异质性指数文献的基础上发掘了景观多样性指数、景观均匀度指数与生态质量间的关系。最后,以江苏省沿江地区2000、2004年的数据开展了实例分析,结果表明,提出的生物生产力和生态质量这两个指标确实能反映区域景观功能的变化,在今后的规划和战略环评中具有一定的应用前景.     

资源型城市贵阳市的生态可持续发展研究

生态可持续发展是资源型城市可持续发展的基础。应用生态足迹的方法,对资源型城市贵阳市的生态可持续发展做了定量评估,并分析了影响贵阳市生态可持续发展的社会经济驱动力。贵阳市1999年-2007年间生态足迹从1.447 hm2/cap增长到2.472hm2/cap,而生态承载力从0.551 hm2/cap下降至0.509 hm2/cap,生态足迹远超出生态承载力,生态系统处于不可持续发展状况。但贵阳市生态效率在不断改善,从1999年的0.500万元GDP/hm2生态足迹增长到2007年的0.787万元GDP/hm2生态足迹,生态系统改善仍存在一定契机。人口增加、能耗增加等因素会导致贵阳市生态足迹增加,而增加农作物播种面积则可减少生态足迹。应用生态足迹的方法,有利于分析资源型城市可持续发展的相关问题,最后就如何缓解贵阳市生态系统压力,促进贵阳市生态可持续发展进行了探讨。     

High and low value fish chains in the Mekong Delta: challenges for livelihoods and governance

This paper investigates the structure, function and wealth distribution within the Pangasius hypophthalmus and Henicorhynchus spp./Labiobarbus spp. value chains in the Mekong Delta of Vietnam. The analysis is driven by key questions relating to the form and function of value chains, their contribution to the livelihoods of farmers and fishers, the effectiveness of government policy and the potential for value chain governance mechanisms, such as contracts and certification, to steer towards sustainable production. The results indicate that actors in the high value Pangasius hypopthalmus export chain have a higher potential income, but face considerably higher economic vulnerability from global markets. Alternatively, Henichorhychus/Labiobarbus spp. fishers are severely constrained in their ability to negotiate higher prices for their fish but appear to be less vulnerable to economic and environmental change. The paper concludes that for value chain governance to improve the livelihoods of fishers and farmers in both high and low value chains, new arrangements are needed that better accommodate customary institutions and informal market relations.     

Do EU pesticide standards promote environmentally-friendly production of fresh export vegetables in developing countries? The evidence from Kenyan green bean industry

Developed countries are major markets for developing country fresh produce. Demand by developed country consumers for spotless produce has encouraged developing country consumers to rely increasingly on pesticides in producing fresh export vegetables. However developed country pesticide standards enacted in response to reports of increased farmer and farm worker pesticide poisoning and the food safety scandals of the 1980s and 1990s require changes in the way growers use pesticides. The EU has especially developed stringent food safety standards relating to, among other things, pesticide usage. Under EU pesticide standards (EU-PS) farmers are trained by their buyers on safe use of pesticides and then closely monitored under contract. This paper looks at the impact of these standards on developing country farmers’ use of alternative pest management practices, pesticide protective clothing and the actual usage of pesticides. It finds that compliance with EU-PS increases the use of alternative pest management practices and protective clothing. However, EU-PS has mixed effect on the quantity of pesticides used. The paper also finds that farmer’s education and access to information play an important role in the use of alternative pest management practices. The paper concludes that EU-PS encourage the use of alternative pest management practices and pesticide protective gear in production of fresh export vegetables. The findings imply that EU-PS promote environmentally-friendly methods of production of fresh export vegetables in developing countries.