缺水、海水淡化与污染

全世界快速的人口增长、城市化和高标准生活加剧了水的短缺,已经导致许多国家(特别是在干旱与半干旱地区)不得不采用海水淡化技术,首要满足家庭需求.在1950与1960年代,海水淡化业商业化.随着成本的大幅度降低和效率的提高,特别是自从1970年代以来,海水淡化已经变成满足家庭需要的一项战略和可靠来源.     

Estimation of maximum scour depths at upstream of front and rear piers for two in-line circular columns

Previous investigations indicate that scour around bridge piers is one of the most important factors for the failure of waterway bridges. Hence, it is essential to determine the accurate scour depth around the bridge piers. Most of the previous studies were based on scour around a single pier; however, in practice, new bridges are usually wide and then piers comprise two circular piers aligned in the flow direction that together support the loading of the structure. In this study, the effect on maximum scour depth of the spacing between two piers aligned in the flow direction was investigated experimentally under clear water scour conditions. The results show that the maximum scour depth at upstream of the front pier occurs when the spacing between the two piers is 2.5 times the diameter of the pier. Two semi empirical equations have been developed to predict the maximum scour depth at upstream of both front and rear piers as a function of the spacing between the piers, in terms of a pier-spacing factor. If the new equations for the pier-spacing factor are used with some of the existing equations for scour at a single pier, the predicted scouring depths are in good agreement with observed results. The S/M equation exhibited the best performance among the various equations tested and was recommended for use in prediction of the equilibrium scour depth. The findings of this study can be used to facilitate the positioning of piers when scouring is a design concern.     

Metal contamination of surface soils of industrial city Sialkot,Pakistan: a multivariate and GIS approach

In this study concentrations of selected metals viz., Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Na, Ni, Pb and Zn in surface soils of Sialkot city known worldwide for tanneries and pharmaceutical industries were measured to assess the status of urban soil pollution and to identify sources of contamination. Hierarchical cluster analysis (HACA) indicated concentrations of Mg and Ca related to parent rock material, Cd, Co, and Pb with traffic related activities, Cr, Cu, Ni and Zn either associated with automobiles activities or industrial pollution and Fe, K and Na related with anthropogenic activities or lithogenous materials. Correlation analyses and principal component analysis based on factor analysis confirmed the results of HACA. Spatial distribution maps exhibited relatively higher concentrations of Cd, Co, Cu, Ni, Pb, Cr and Zn along traffic routes in the city and streams. The results highlighted concentration of Cd, Ni, Cr, Zn, and Pb measured in urban soil exceeded the permissible limit of surface soils and advocated an imperative need for detailed baseline investigations of spatial distribution of heavy metals and other contaminants for the formulation of geochemical database that should be made available to stakeholder involved in monitoring, assessment and conservation of soil contamination for future planning and management of the Sialkot city.     

Estimation of Aerobic Capacity and Determination of Its Associated Factors Among Male Workers of Industrial Sector of Iran

Introduction. The aim of this study was to estimate maximal aerobic capacity (V_O2max), to determine its associated factors among workers of industrial sector of Iran and to develop a regression equation for subjects’ V_O2max. Methods. In this study, 500 healthy male workers employed in Shiraz industries participated voluntarily. The subjects’ V_O2max was assessed with the ergocycle test according to the Åstrand protocol. Required data was collected with a questionnaire covering demographic details (i.e., age, job tenure, marital status, education, nature of work, shift work, smoking and weekly exercises). Results. The subject’s mean V_O2max was 2.69 ± 0.263 L/min. The results showed that there was an association between V_O2max and age, BMI, hours of exercise and smoking, but there was no association between V_O2max and height, weight, nature of work and working schedule. On the basis of the results, regression equations were developed to estimate V_O2max. Conclusion. Final regression equation developed in this study may be used to estimate V_O2max reliably without the need to use other laboratory instruments for aerobic measurement.     

Mechanistic aspects of poly(ethylene terephthalate) recycling–toward enabling high quality sustainability decisions in waste management

Environmental Science and Pollution Research - Since plastic waste pollution is a severe environmental concern in modern life, the demand for recycling poly(ethylene terephthalate) (PET) has...     

On integration of policies for climate and global change

Currently envisaged mitigation of greenhouse gases (GHG) emissions will be insufficient to appreciably limit climate change and its impacts. Adaptation holds the promise of ameliorating the impacts on a small subset of systems being affected. There is no question that both will be needed. However, climate change is only part of a broader multi-stress setting of global through to local changes. Privileging climate related policies over other concerns leads to tragic outcomes. Climate policies need to be designed for and integrated into this broader and challenging context. This paper focuses on placing climate change within the broader context of global change and the importance of aligning climate policy objectives with the myriad other policies that still need to be implemented if our primary goal is improving human welfare rather than limiting our focus to climate change and its impacts.     

Semicontinuous PM2.5 sulfate and nitrate measurements at an urban and a rural location in New York: PMTACS-NY summer 2001 and 2002 campaigns

Several collocated semicontinuous instruments measuring particulate matter with particle sizes < or =2.5 microm (PM2.5) sulfate (SO4(2-)) and nitrate (NO3-) were intercompared during two intensive field campaigns as part of the PM2.5 Technology Assessment and Characterization Study. The summer 2001 urban campaign in Queens, NY, and the summer 2002 rural campaign in upstate New York (Whiteface Mountain) hosted an operation of an Aerosol Mass Spectrometer, Ambient Particulate Sulfate and Nitrate Monitors, a Continuous Ambient Sulfate Monitor, and a Particle-Into-Liquid Sampler with Ion Chromatographs (PILS-IC). These instruments provided near real-time particulate SO4(2-) and NO3- mass concentration data, allowing the study of particulate SO4(2-)/NO3- diurnal patterns and detection of short-term events. Typical particulate SO4(2-) concentrations were comparable at both sites (ranging from 0 to 20 microg/m3), while ambient urban particulate NO3- concentrations ranged from 0 to 11 microg/m3 and rural NO3- concentration was typically less than 1 microg/m3. Results of the intercomparisons of the semicontinuous measurements are presented, as are results of the comparisons between the semicontinuous and time-integrated filter-based measurements. The comparisons at both sites, in most cases, indicated similar performance characteristics. In addition, charge balance calculations, based on major soluble ionic components of atmospheric aerosol from the PILS-IC and the filter measurements, indicated slightly acidic aerosol at both locations.     

Toward a high-rate enhanced biological phosphorus removal process in a membrane-assisted bioreactor.

A membrane enhanced biological phosphorus removal (MEBPR) process was studied to determine the impact of hydraulic retention time (HRT) and solids retention time (SRT) on the removal of chemical oxygen demand (COD), nitrogen, and phosphorus from municipal wastewater. The MEBPR process was capable of delivering complete nitrification independent of the prevailing operating conditions, whereas a significant improvement in COD removal efficiency was observed at longer SRTs. In the absence of carbon-limiting conditions, the MEBPR process was able to achieve low phosphorus concentrations in the effluent at increasingly higher hydraulic loads, with the lowest HRT being 5 hours. The MEBPR process was also able to maintain optimal phosphorus removal when the SRT was increased from 12 to 20 days. However, at higher suspended solids concentrations, a substantial increase was observed in carbon utilization per unit mass of phosphorus removed from the influent. These results offer critical insights to the application of membrane technology for biological nutrient removal systems.     

Elemental carbon and sulfate aerosols over a rural mountain site in the northeastern United States: Regional emissions and implications for climate change

The effect of elemental carbon (EC) on global as well as regional climate forcing is potentially very important. However, the EC data for northeastern U.S. is sparse. Daily EC concentrations, [EC], and [SO₄] were measured in the northeastern U.S. at a regionally representative rural site, Whiteface Mountain (WFM; 44.366°N, 73.903°W, 1.5 km amsl, above mean sea level), New York (NY), for 1997. The air mass origin was determined using 6-h backward in time air trajectories obtained from the Hybrid Single-Particle Lagrangian Integrated Trajectory Model (HYSPLIT 4). [EC] and [SO₄] were highly variable and influenced by synoptic–scale meteorology (rainy vs dry periods). The maximum daily [EC] and [SO₄] were 364 ± 55 and 28,800 ± 3000 ng m^?3, respectively. [EC] and [SO₄] also showed seasonal variations at WFM. Occurrences of high daily [EC] were mainly in spring months, while peak daily [SO₄] concentrations occurred in summer months. This behavior of aerosols is due to the fact that the sources of EC and SO₄ are not the same and also due to the enhanced photochemical activity during summer months that increased the production of SO₄ from SO₂. High [EC] and [SO₄] values were associated with westerly air flow from the industrialized Midwestern U.S. Sector analysis using HYSPLIT 4 air trajectories showed that regions lying between the southwest and northwest of the WFM contributed 81% and 83% of the [EC] and [SO₄], respectively. The monthly net direct radiative forcing for shortwave (SW) due to EC and SO₄ aerosols at the top of the atmosphere (TOA) varied from ?0.05 to ?0.50 W m^?2, with an annual average of ?0.20 ± 0.15 W m^?2 that gives a net cooling effect. Average net radiative forcing at WFM for clear sky is lower than the global average radiative forcing reported by IPCC (Foster and Ramaswamy, 2007).