查干湖汇水区面源污染风险识别及管控

面源污染是我国流域面临的主要水环境问题,为了识别面源污染高风险区和潜在风险路径,实现流域水环境保护,以查干湖水质目标为约束条件,构建4类关键“源”景观.选取高程、坡度、土地利用类型、污染强度、距居民点距离、距公路距离、距铁路距离、距水体距离等8个评价因子构建阻力面,对查干湖汇水区面源污染风险区和风险路径进行识别,提出管控分区和治理措施.结果表明:①查干湖汇水区关键“源”景观有4类,分别为面源污染单位面积高负荷区、坡度>3°区域、污染传输通道和临湖区域,面积共126.33 km2.②查干湖汇水区面源污染高风险区即面源污染重点管控区,占汇水区总面积的27.10%,主要位于乾安灌区有字泡区域、查干湖及周边泡沼沿岸.区内现有耕地不再增加,同时对坡度较大的区域退耕还湿、退耕还草,并设置污染降解设施.③查干湖汇水区面源污染较高风险区即面源污染一般管控区,占汇水区总面积的20.23%.该区鼓励开展有机农业,发展生态旅游.④查干湖北岸和东南岸、库里泡周边设置一定宽度的植被缓冲带,汇水区设置生态降解渠道333.41 km,生态湿地节点9个.研究显示,污染排放强度是查干湖汇水区面源污染风险的主要威胁因素,需要重点加强查干湖汇水区乾安灌区有字泡、湖区北岸及东南岸的面源污染管控.      

Association of serum levels of perfluoroalkyl substances with gestational diabetes mellitus and postpartum blood glucose

This study was conducted to examine the association of perfluoroalkyl substance(PFAS)exposure with gestational diabetes mellitus(GDM) risk and postpartum fasting blood glucose.We used a 1:2 matched case–control study with 84 GDM subjects and 168 healthy pregnant women from Beijing, China. The maternal blood was collected at 1–2 days before delivery, and eight linear isomers and fourteen branched isomers were determined in maternal serum.Logistic regression analyses were performed to evaluate the associations after adjusting for potential confounders. The median of the sum of levels of total PFASs was 4.24 ng/m L with a interquartile range(IQR) of 2.82–6.54 ng/m L. Although maternal PFAS exposure was not associated with risk of GDM, significant positive associations were observed between evaluated exposure to specific PFAS congeners and increasing blood glucose. The odds ratio(ORs) of the highest category of postpartum fasting blood glucose for perfluoro-1-metylheptylsulfonat(1 m-PFOS), perfluoro-3/4-metylheptylsulfonat(3 m+4 m-PFOS), perfluoro-5-metylheptylsulfonat(5 m-PFOS), and perfluorohexane sulfonate(PFHx S) were 2.03(95% CI: 1.09–3.77), 1.93(95% CI:1.04–3.58), 2.48(95% CI: 1.33–4.65), and 2.26(95% CI: 1.21–4.21), respectively, suggesting negative effects of maternal exposure to specific PFAS compounds on glucose metabolism.     

Polar organic tracers in PM2.5 aerosols from an inland background area in Southwest China: Correlations between secondary organic aerosol tracers and source apportionment

PM_(2.5) aerosol samples were collected over 12 hr and 24 hr intervals in an inland background area, Gongga Mountain National Nature Reserve(hereafter shortened to Gongga), during the summer of 2011. Polar organic tracers, inorganic ions and meteorological data were measured. The purpose of this work was to investigate the variation patterns, formation and sources of the secondary organic aerosol tracers in the studied atmosphere. The average concentrations of isoprene oxidation products, α-pinene oxidation products, β-caryophyllinic acid, sugars, sugar alcohols and anhydrosugars were 88.6 ± 106.1, 3.6 ± 5.7,0.13 ± 0.30, 13.6 ± 13.1, 31.9 ± 31.4 and 14.8 ± 10.7 ng/m3 respectively in all aerosol samples.The aged α-pinene second organic aerosol(SOA) tracers(i.e., 3-hydroxyglutraric acid(3 HGA), 3-hydroxy-2,2-dimethylglutaric acid(HDMGA), 3-acetylpentandioic acid(APDA) and 3-methyl-1,2,3-butanetricarboxylic acid(MBTCA)) correlated significantly with each other in the 24 hr PM2.5 aerosol samples, indicating that OH· is the major factor controlling the formation of these α-pinene SOA tracers. Using the positive matrix factorization(PMF) model and the tracer-based source apportionment method, we calculated that isoprene oxidation products, α-pinene oxidation products, sesquiterpene oxidation products, biomass burning, fungi spores and anthropogenic SOA accounted for 21.9% ± 5.5%, 8.4% ± 2.1%, 3.0% ± 0.7%, 5.2% ± 5.3%, 5.0% ± 6.2% and 31.4% ± 7.8% of organic carbon respectively during the sampling period.     

A multilevel perspective of interpersonal trust: Individual,dyadic, and cross‐level predictors of performance

While it is generally known that interpersonal trust facilitates individual functioning, few studies have examined the role of specific features of the interpersonal trust network — individual, dyadic, third‐party, and network‐level features — on individual performance. We adopt a multilevel perspective of interpersonal trust to examine how individuals' performance is not only predicted by their individual‐level centrality in the interpersonal trust network but also moderated, at the network level, by the overall centralized nature of that network. Further, we examine whether mutual trust relationships at the dyadic level, as well as shared trust ties to common third parties, can predict individuals' performance. We test our hypotheses with 206 members in 15 professional networking groups and find that interpersonal trust operates at multiple levels to predict members' performance in terms of generating income from business referrals. These findings provide theoretical and practical implications on how interpersonal trust relationships operate and can be managed for performance gains. Copyright © 2016 John Wiley & Sons, Ltd.     

Electroactive polyamide modified carbon paste electrode for the determination of ascorbic acid

Construction electroactive polyamide (EPA) with aniline-pentamer-based in the main chain has been modified on the surface of carbon paste electrode (CPE) for detecting ascorbic acid (AA). Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy studies confirm the well-defined molecular structure of the oligoaniline and EPA. Further, the in situ chemical oxidation of EPA was monitored by UV-Visible absorption spectrum. The electroactivity of the EPA was evaluated by performing electrochemical cyclic voltammetry study. The sensing response studies have revealed that this EPA-modified CPE electrode can detect AA in the range of 0.05–0.7 mM with detection limit of 0.005 mM and sensitivity of 1.5 × 10^–5 AmM^–1. Besides, this EPA-modified CPE electrode shows a minimal relative standard deviation of 1.73%.     

Two-phase modeling of sediment clouds

A sediment cloud release in stagnant ambient fluid occurs in many engineering applications. Examples include land reclamation and disposal of dredged materials. The detailed modeling of the distinct characteristics of both the solid and fluid phases of the sediment cloud is hitherto unavailable in the literature despite their importance in practice. In this paper, the two-phase mixing characteristics of the sediment cloud are investigated both experimentally and theoretically. Experiments were carried out to measure the transient depth penetration and the lateral spread of the sediment cloud and its entrained fluid using the laser induced fluorescence technique, with a range of particle sizes frequently encountered in the field (modeled at laboratory scale). A two-phase model of the sediment cloud that provides detailed predictions of the mixing characteristics of the individual phases is also proposed. The entrained fluid characteristics are solved by an integral model accounting for the buoyancy loss (due to particle separation) in each time step. The flow field induced by the sediment cloud is approximated by a Hill’s spherical vortex centered at the centroid and with the size of the entrained fluid. The particle equation of motion under the effect of the induced flow governs each computational particle. A random walk model using the hydrodynamic diffusion coefficient is used to account for the random fluctuation of particles in the dispersive regime. Overall, the model predictions of the two-phase mixing characteristics are in good agreement with the experimental data for a wide range of release conditions.     

城市建筑垃圾的资源化利用

随着建设项目的增多,建筑垃圾也日益增多。本文对建筑垃圾资源化利用进行了初步分析,重点通过对建筑垃圾的分类研究,提出我国建筑垃圾资源化存在问题及建议。     

Effect of metal ions and humic acid on the dechlorination of tetrachloroethylene by zerovalent iron

The dechlorination of tetrachloroethylene (PCE) by zerovalent iron (Fe(0)) in the presence of metal ions and humic acid was investigated. In the absence of metal ion and humic acid, 64% of the initial PCE was dechlorinated after 125 h with the production of ethane and ethene as the major end products. The dechlorination followed pseudo-first-order kinetics and the normalized surface rate constant (k(SA)) for PCE dechlorination was (3.43+/-0.61)x10(-3)lm(-2)h(-1). Addition of metal ions enhanced the dechlorination efficiency and rate of PCE, and the enhancement effect followed the order Ni(II)>Cu(II)>Co(II). The k(SA) for PCE dechlorination in the presence of metal ions were 2-84 times higher than that in the absence of metal ions. X-ray photoelectron spectroscopy (XPS) showed that Cu(II) and Ni(II) were reduced by Fe(0) to zerovalent metals, and resulted in the formation of bimetallic system to accelerate the dechlorination reaction. On the contrary, humic acid out-competed the reactive sites on iron surface with PCE, and subsequently decreased the dechlorination efficiency and rate of PCE by Fe(0). However, the reactivity of Fe(0) for PCE dechlorination in the presence of metal ions and humic acid increased by a factor of 3-161 when compared to the iron system containing humic acid alone. Since humic acid and metal ions are the most often found co-existing compounds in the contaminated aquifers with chlorinated hydrocarbons, results obtained in this study is useful to better understand the feasibility of using Fe(0) for long-term application to the remediation of contaminated sites.     

Degradation of carbofuran in water by solar photocatalysis in presence of photosensitizers

The effect of the presence of photosensitizers, methylene blue (MB) and rose Bengal (RB), on the degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) in water in a solar photocatalytic system was investigated. It was found that as compared to MB, RB generally showed a stronger effect on the decomposition of carbofuran under comparable conditions. Among the conditions studied, adding 2 x 10(-6) M of RB, that corresponding to 2% of the initial concentration of carbofuran solution in the system, rendered the most effective degradation of carbofuran. As a result, a carbofuran removal percentage of 69.9%, a mineralization efficiency of 28.0%, and a microtoxicity reduction of 65.0% could be achieved. The degradation and mineralization of carbofuran was found to follow the pseudo-first order reaction kinetics. The decomposition mechanism of carbofuran was further investigated through identification of the intermediates to elaborate the influence of dye photosensitizer on the solar photocatalysis of carbofuran in water. On the basis of the intermediates identified, including carbofuran phenol, 3-hydroxy carbofuran phenol, and substituted alcohols (3-phenoxy 1-propanol, 2-ethyl 1-hexanol, 2-butoxyl ethanol), it appears that hydrolysis and hydroxylation were the two key mechanisms for decomposing carbofuran during the process of solar photocatalysis with the aid of dye photosensitizer.