城镇生活垃圾转运技术的探讨

对垃圾转运系统的基本知识做了简要介绍,详细阐述了目前生活垃圾常用的转运模式,介绍了垃圾转运过程中的二次污染及控制技术,分析了现行主要的垃圾转运技术及其发展趋势。     

The role of the European commission in the maintenance of air quality standards

We describe intercomparison results obtained in the framework of the EC Directive 799/80 CEE on SO₂, Black Smoke (BS) and Total Suspended Particulates (TSP) using standard reference materials. Calibrations and measuring methods used in national laboratories were compared to the reference methods laid down in the Directive. For SO₂, the deviations were caused by inappropriate handling of the calibration rather than by possible shortcomings of the different methods themselves. In contrast, for BS, largest deviations were caused by differences in configurations of filter/reflectometer and of the conversion curves; for TSP by varying the type of filters and conditioning procedures before weighing.     

Chloride and atrazine transport through saturated soil columns

A possible contamination of water resources by the application of pesticides is a problem confronting many irrigated areas in arid and semi-arid areas. The best management practices have to be adopted to minimize pesticide transport and leaching under irrigated conditions. Atrazine dissipation in loam and sandy loam soils has been tested in the laboratory using disturbed soil columns under saturated flooding conditions. All the experiments were performed in replicates. The chloride transport was also studied to test its behavior as an inert tracer in both the soils. Atrazine and chloride breakthrough curves were analyzed with the parameter optimization program CXTFIT to determine transport parameters including pore-water velocity (v), retardation coefficient (R), hydrodynamic dispersion coefficient (D), and pulse duration (t _o ). The pore-water velocity and pulse duration of the solute were estimated from the experimental conditions and kept constant during the optimization procedure. The results indicated that the R of chloride was not significantly different from 1, indicating that chloride is an inert tracer for the types of soil tested in this study. The average R of atrazine was 4.56 and 3.15 for sandy loam and loam soils, respectively. Results also showed that the hydrodynamic dispersion coefficient was much higher in the case of sandy loam soil compared to the loam soil for the two solutes, thus indicating non-equilibrium transport conditions. In the case of chloride, D increased from 0.4 for the loam soil to 16.2?cm²/min for the sandy loam soil. Similar results were observed in the case of atrazine in which D for the sandy loam soil was 60% higher than that for the loam soil. More atrazine leaching is expected under field conditions due to the presence of soil cracks and macropores.     

产乙烯脱卤拟球菌195脱卤反应途径的理论探针

运用密度泛函理论在B3LYP/6-31G(d)水平下对多氯二苯并-对-二 (PCDDs)、多氯二苯并呋喃(PCDFs)、多氯联苯(PCBs)、多溴联苯醚(PBDEs)和氯苯分子进行计算,找到了一个可指示产乙烯脱卤拟球菌(Dehalococcoides ethenogenes)195降解转化这些芳香卤化物脱卤反应途径和中间产物的参数—结构上可能的脱卤产物的分子总能量(ET).以ET作为理论探针可指示PCDD/Fs、PCBs、PBDEs和氯苯被菌株195转化的主要脱卤中间产物,脱卤反应倾向于生成具有较低ET值的中间产物.另外可以利用结构上可能的脱卤中间产物与具有最低ET值脱卤中间产物间的分子总能量差(?ET)作为理论探针,推断存在第2种脱卤中间产物的可能性,?ET越小,则同时存在多种脱卤中间产物的可能性越大.     

Fate and transport of phenol in a packed bed reactor containing simulated solid waste

An assessment of the risk to human health and the environment associated with the presence of organic contaminants (OCs) in landfills necessitates reliable predictive models. The overall objectives of this study were to (1) conduct column experiments to measure the fate and transport of an OC in a simulated solid waste mixture, (2) compare the results of column experiments to model predictions using HYDRUS-1D (version 4.13), a contaminant fate and transport model that can be parameterized to simulate the laboratory experimental system, and (3) determine model input parameters from independently conducted batch experiments. Experiments were conducted in which sorption only and sorption plus biodegradation influenced OC transport. HYDRUS-1D can reasonably simulate the fate and transport of phenol in an anaerobic and fully saturated waste column in which biodegradation and sorption are the prevailing fate processes. The agreement between model predictions and column data was imperfect (i.e., within a factor of two) for the sorption plus biodegradation test and the error almost certainly lies in the difficulty of measuring a biodegradation rate that is applicable to the column conditions. Nevertheless, a biodegradation rate estimate that is within a factor of two or even five may be adequate in the context of a landfill, given the extended retention time and the fact that leachate release will be controlled by the infiltration rate which can be minimized by engineering controls.     

Seasonal variations of transport pathways and potential sources of PM2.5 in Chengdu,China (2012–2013)

PM_2.5 in Chengdu showed clear seasonal and diurnal variation. 5, 5, 5 and 3 mean clusters are generated in spring, summer, autumn, and winter. Short-distance air masses are important pathways in Chengdu. Emissions within the Sichuan Basin contribute significantly to PM_2.5 pollution. Long-range transport from Southern Xinjiang is a dust invasion path to Chengdu. Seasonal pattern of transport pathways and potential sources of PM_2.5 in Chengdu during 2012–2013 were investigated based on hourly PM_2.5 data, backward trajectories, clustering analysis, potential source contribution function (PSCF), and concentration-weighted trajectory (CWT) method. The annual hourly mean PM_2.5 concentration in Chengdu was 97.4 mg·m^–3. 5, 5, 5 and 3 mean clusters were generated in four seasons, respectively. Short-distance air masses, which travelled within the Sichuan Basin with no specific source direction and relatively high PM_2.5 loadings (>80 mg·m^–3) appeared as important pathways in all seasons. These short pathways indicated that emissions from both local and surrounding regions of Chengdu contributed significantly to PM_2.5 pollution. The cities in southern Chengdu were major potential sources with PSCF>0.6 and CWT>90 mg·m^–3. The northeastern pathway prevailed throughout the year with higher frequency in autumn and winter and lower frequency in spring and summer. In spring, long-range transport from southern Xinjiang was a representative dust invasion path to Chengdu, and the CWT values along the path were 30-60 mg·m^–3. Long-range transport was also observed in autumn from southeastern Xinjiang along a northwesterly pathway, and in winter from the Tibetan Plateau along a westerly pathway. In summer, the potential source regions of Chengdu were smaller than those in other seasons, and no long-range transport pathway was observed. Results of PSCF and CWT indicated that regions in Qinghai and Tibet contributed to PM_2.5 pollution in Chengdu as well, and their CWT values increased to above 30 mg·m^-3 in winter.     

Path selection and foraging efficiency in Argentine ant transport networks

We experimentally investigated both individual and collective behavior of the Argentine ant Linepithema humile as they crossed symmetrical and asymmetrical bifurcations in gallery networks. Ants preferentially followed the branch that deviated the least from their current direction and their probability to perform a U-turn after a bifurcation increased with the turning angle at the bifurcation. At the collective level, colonies were better able to find the shortest path that linked the nest to a food source in a polarized network where bifurcations were symmetrical from one direction and asymmetrical from the other than in a network where all bifurcations were symmetrical. We constructed a model of individual behavior and showed that an individual’s preference for the least deviating path will be amplified via the ants’ mass recruitment mechanism thus explaining the difference found between polarized and non-polarized networks. The foraging efficiency measured in the simulations was three times higher in polarized than in non-polarized networks after only 15 min. We conclude that measures of transport network efficiency must incorporate both the structural properties of the network and the behavior of the network users.     

Transport of bacterial cell (E. coli) from different recharge water resources in porous media during simulated artificial groundwater recharge

• The recharge pond dwelling process induced changes in cell properties. • Cell properties and solution chemistry exerted confounding effect on cell transport. • E. coli cells within different recharge water displayed different spreading risks. Commonly used recharge water resources for artificial groundwater recharge (AGR) such as secondary effluent (SE), river water and rainfall, are all oligotrophic, with low ionic strengths and different cationic compositions. The dwelling process in recharge pond imposed physiologic stress on Escherichia coli (E. coli) cells, in all three types of investigated recharge water resources and the cultivation of E. coli under varying recharge water conditions, induced changes in cell properties. During adaptation to the recharge water environment, the zeta potential of cells became more negative, the hydrodynamic diameters, extracellular polymeric substances content and surface hydrophobicity decreased, while the cellular outer membrane protein profiles became more diverse. The mobility of cells altered in accordance with changes in these cell properties. The E. coli cells in rainfall recharge water displayed the highest mobility (least retention), followed by cells in river water and finally SE cells, which had the lowest mobility. Simulated column experiments and quantitative modeling confirmed that the cellular properties, driven by the physiologic state of cells in different recharge water matrices and the solution chemistry, exerted synergistic effects on cell transport behavior. The findings of this study contribute to an improved understanding of E. coli transport in actual AGR scenarios and prediction of spreading risk in different recharge water sources.     

典型氯碱污染场地环境风险评价

以广东某氯碱化工污染场地为研究区域,采集了场地22个土壤及地下水样品,分析了25项污染物在不同区域的分布特征及其来源。监测结果表明,煤炭堆场与锅炉房区土壤受重金属铅、镍污染。六六六、四氯化碳、三氯甲烷、六氯苯、苯是场地的特征污染物,主要分布在危险品仓库、漂洗车间与四氯化碳车间。根据监测结果开展了不同暴露途径致癌风险值及非致癌危害商的计算。结果表明,部分样品表层土壤中上述有机污染物的基于人体健康致癌风险指数均超过10-6,最高达到1.65×10-2,表明风险水平高;非致癌危害在各暴露途径下也超过可接受值1,最高达5.59×104,表明风险水平高。说明对于存在高风险的区域必须进行采取合适的措施进行修复,减缓场地再利用后对人群健康的影响。     

Positive Feedback Loop between Introductions of Non‐Native Marine Species and Cultivation of Oysters in Europe

With globalization, agriculture and aquaculture activities are increasingly affected by diseases that are spread through movement of crops and stock. Such movements are also associated with the introduction of non‐native species via hitchhiking individual organisms. The oyster industry, one of the most important forms of marine aquaculture, embodies these issues. In Europe disease outbreaks affecting cultivated populations of the naturalized oyster Crassostrea gigas caused a major disruption of production in the late 1960s and early 1970s. Mitigation procedures involved massive imports of stock from the species’ native range in the northwestern Pacific from 1971 to 1977. We assessed the role stock imports played in the introduction of non‐native marine species (including pathogens) from the northwestern Pacific to Europe through a methodological and critical appraisal of record data. The discovery rate of non‐native species (a proxy for the introduction rate) from 1966 to 2012 suggests a continuous vector activity over the entire period. Disease outbreaks that have been affecting oyster production since 2008 may be a result of imports from the northwestern Pacific, and such imports are again being considered as an answer to the crisis. Although successful as a remedy in the short and medium terms, such translocations may bring new diseases that may trigger yet more imports (self‐reinforcing or positive feedback loop) and lead to the introduction of more hitchhikers. Although there is a legal framework to prevent or reduce these introductions, existing procedures should be improved. Ciclo de Retroalimentación Positiva entre la Introducción de Especies Marinas No‐Nativas y el Cultivo de Ostras en Europa