Effect of barium sulfate modification on the SO2 tolerance of V2O5 /TiO2 catalyst for NH3-SCR reaction

Sulfur poisoning of V_2O_5/BaSO_4–TiO_2(VBT),V_2O_5/WO_3–TiO_2(VWT) and V_2O_5/BaSO_4–WO_3–TiO_2(VBWT) catalysts was performed in wet air at 350℃ for 3 hr,and activities for the selective catalytic reduction of NO_x with NH_3 were evaluated for 200–500℃.The VBT catalyst showed higher NO_x conversions after sulfur poisoning than the other two catalysts.The introduction of barium sulfate contributed to strong acid sites for the as-received catalyst,and eliminated the redox cycle of active vanadium oxide to some extent,which resulted in a certain loss of activity.Readily decomposable sulfate species formed on VBT-S instead of inactive sulfates on VWT-S.These decomposable sulfates increased the number of strong acid sites significantly.Some sulfate species escaped during catalyst preparation and barium sulfate was reproduced during sulfur poisoning,which protects vanadia from sulfur oxide attachment to a great extent.Consequently,the VBT catalyst exhibited the best resistance to sulfur poisoning.     

基于环境质量管理的城市综合环境绩效评估研究

文章以26个省会城市2004~2013年的样本数据,从环境健康、生态保护、资源与能源利用、环境治理等4个方面开展研究,构建了包括4项二级指标、12项三级指标和26项四级指标在内的城市综合环境绩效指标体系。研究发现,大部分城市的综合环境绩效历年差异明显,东、中、西部的环境绩效有明显的差异。因此,文章认为应该进一步优化环境绩效指标体系,充分体现区域差异特点,通过实施城市综合环境绩效考核来提高城市环境质量管理水平。     

Modification of Ce02-ZrO2 catalyst by potassium for NOx-assisted soot oxidation

Potassium-modified ceria-zirconia catalyst was synthesized by wetness impregnation method. The ageing treatment was performed in static air at 800℃ for 20 hr to evaluate the thermal stability of the catalyst. The catalysts were characterized by X-ray diffraction,BET surface area, oxygen storage capacity, NOx-temperature programmed desorption and soot-temperature programmed oxidation measurements. By introduction of potassium, the maximum soot oxidation rate temperature (Tm) of the ceria-zirconia based catalyst decreased from 525 to 428℃ in the presence of NO under a loose contact mode. The shift of Tm of the K-modified catalyst after ageing is only 15℃. The enhanced activity of the aged catalyst mainly lies in the promotional effect of potassium on the NOx/oxygen storage cacity as well as the soot-catalyst contact.     

沉入式膜生物反应器处理池塘污水的初步实验研究

膜生物反应器(MBR)主要用于工业污水和城市生活污水的处理,但在水产养殖污水处理方面的应用研究,国内外尚未见报道.作者根据膜生物反应器的工作原理和水产养殖污水的主要特征,设计了一种简易的沉入式膜生物反应器,尝试性地对珠江口有代表性的对虾低位养殖池污水进行了处理实验,并根据实验结果对今后开展无公害高效水产养殖模式提出了一些设想.     

<Emphasis Type="Italic">Synechococcus</Emphasis> production and grazing loss rates in nearshore tropical waters

Temporal variation of Synechococcus, its production (μ) and grazing loss (g) rates were studied for 2 years at nearshore stations, i.e. Port Dickson and Port Klang along the Straits of Malacca. Synechococcus abundance at Port Dickson (0.3–2.3 × 10⁵ cell ml^?1) was always higher than at Port Klang (0.3–7.1 × 10⁴ cell ml^?1) (p < 0.001). μ ranged up to 0.98 day^?1 (0.51 ± 0.29 day^?1), while g ranged from 0.02 to 0.31 day^?1 (0.15 ± 0.07 day^?1) at Port Klang. At Port Dickson, μ and g averaged 0.47 ± 0.13 day^?1 (0.29–0.82 day^?1) and 0.31 ± 0.14 day^?1 (0.13–0.63 day^?1), respectively. Synechococcus abundance did not correlate with temperature (p > 0.25), but nutrient and light availability were important factors for their distribution. The relationship was modelled as log Synechococcus = 0.37Secchi ? 0.01DIN + 4.52 where light availability (as Secchi disc depth) was a more important determinant. From a two-factorial experiment, nutrients were not significant for Synechococcus growth as in situ nutrient concentrations exceeded the threshold for saturated growth. However, light availability was important and elevated Synechococcus growth rates especially at Port Dickson (F = 5.94, p < 0.05). As for grazing loss rates, they were independent of either nutrients or light intensity (p > 0.30). In nearshore tropical waters, an estimated 69 % of Synechococcus production could be grazed.     

Investigating the spatial distribution of phototrophic picoplankton in a tropical estuary

We sampled extensively (29 stations) at the Klang estuarine system over a 3-day scientific expedition. We measured physical and chemical variables (temperature, salinity, dissolved oxygen, total suspended solids, dissolved inorganic nutrients) and related them to the spatial distribution of phototrophic picoplankton (Ppico). Multivariate analysis of variance of the physicochemical variables showed the heterogeneity of the Klang estuarine system where the stations at each transect were significantly different (Rao’s F _{18, 36}?=?8.401, p?<?0.001). Correlation analyses also showed that variables related to Ppico abundance and growth were mutually exclusive. Distribution of Ppico was best explained by the physical mixing between freshwater and seawater whereas Ppico growth was correlated with temperature.     

Environmental Factors and Risk Areas of West Nile Virus in Southern California, 2007–2009

The West Nile virus (WNV) may post a significant health risk for mammals, including humans and insects. This study examines the spatial–temporal effects of environmental factors on WNV dissemination with a case study of ten counties in the southern California, where the epidemic was recently most prevalent within the USA. WNV surveillance data were obtained from the California Vectorborne Disease Surveillance System and Centers for Disease Control and Prevention. Remote sensing and Geographic Information Systems (GIS) techniques were combined to derive environmental variables. Principal component analysis was performed to select the most relevant environmental variables. Two ecological zones were identified based on the selected variables. Identification of risk areas for WNV was limited to a zone with 95% mosquitoes surveillance records. Three time windows, the epidemiological weeks?18–26, 27–35, and 36–44 in each year of 2007–2009, were examined in details with risk area mapping. It is found that the southern part of San Joaquin Valley in Kern County and Los Angeles County (especially its southern part) were the most vulnerable locations for WNV outbreak. Main factors contributing to the WNV propagation included summer mean temperature, annual mean deviation from the mean temperature, land surface temperature, elevation, landscape complexity, landscape diversity, and vegetation water content. The result of this study improves understanding of WNV ecology and provides tools for detecting, tracking, and predicting the epidemic. The holistic approach developed for this study, which integrated remotely sensed, GIS-based, and in situ-measured environmental data with landscape metrics, may be applied to studies of other vector-borne diseases.     

Factors controlling phosphate interaction with iron oxides

Factors such as pH, solution ion composition, and the presence of natural organic matter (NOM) play a crucial role in the effectiveness of phosphorous adsorption by iron oxides. The interplay between these factors shows a complicated pattern and can sometimes lead to controversial results. With the help of mechanistic modeling and adsorption experiments, the net macroscopic effect of single and combined factors can be better understood and predicted. In the present work, the relative importance of the above-mentioned factors in the adsorption of phosphate was analyzed using modeling and comparison between the model prediction and experimental data. The results show that, under normal soil conditions, pH, concentration of Ca, and the presence of NOM are the most important factors that control adsorption of phosphate to iron oxides. The presence of Ca not only enhances the amount of phosphate adsorbed but also changes the pH dependency of the adsorption. An increase of dissolved organic carbon from 0.5 to 50 mg L can lead to a >50% decrease in the amount of phosphate adsorbed. Silicic acid may decrease phosphate adsorption, but this effect is only important at a very low phosphate concentration, in particular at high pH.     

Assessing Surface Water Quality and Its Relation with Urban Land Cover Changes in the Lake Calumet Area, Greater Chicago

Urban land use and land cover change significantly affect spatial and temporal patterns of runoff, which in turn impacts surface water quality. With the exponential growth in urban areas over the past three decades, changes in land use and land cover to cater for the growth of cities has been a conspicuous spectacle in urban spaces. The main goal of this study was to assess the impacts of land cover change on runoff and surface water quality using a partial area hydrology framework. The study employed ArcHydro GIS extension and a modified version of Long-Term Hydrologic and Nonpoint Source Pollution model (L-THIA-NPS) in estimating runoff and nonpoint source pollutant concentration around Lake Calumet between 1992 and 2001. Data employed include National Land Cover Data set, rainfall data, digital elevation model (DEM), Soil Survey Geographic (SSURGO) data, and The United States Environmental Protection Agency’s STORET (storage and retrieval) water quality data. The model was able to predict surface water quality reasonably well over the study period. Sensitivity analysis facilitated a manual calibration of the model. Model validation was executed by comparing simulated results following calibration and observed water quality data for the study area. The study demonstrates that the level of concentration of nonpoint source pollutants in surface water within an urban watershed heavily depends on the spatiotemporal variations in areas that contribute towards runoff compared to the spatial extent of change in major land use/land cover.     

Remediating ethylbenzene-contaminated clayey soil by a surfactant-aided electrokinetic (SAEK) process

The objectives of this research are to investigate the remediation efficiency and electrokinetic behavior of ethylbenzene-contaminated clay by a surfactant-aided electrokinetic (SAEK) process under a potential gradient of 2 Vcm(-1). Experimental results indicated that the type of processing fluids played a key role in determining the removal performance of ethylbenzene from clay in the SAEK process. A mixed surfactant system consisted of 0.5% SDS and 2.0% PANNOX 110 showed the best performance of ethylbenzene removed in the SAEK system. The removal efficiency of ethylbenzene was determined to be 63-98% in SAEK system while only 40% was achieved in an electrokinetic system with tap water as processing fluid. It was found that ethylbenzene was accumulated in the vicinity of anode in an electrokinetic system with tap water as processing fluid. However, the concentration front of ethylbenzene was shifted toward cathode in the SAEK system. The electroosmotic permeability and power consumption were 0.17 x 10(-6)-3.01 x 10(-6) cm(2)V(-1)s(-1) and 52-123 kW h m(-3), respectively. The cost, including the expense of energy and surfactants, was estimated to be 5.15-12.65 USD m(-3) for SAEK systems, which was 2.0-4.9 times greater than that in the system of electrokinetic alone (2.6 USD m(-3)). Nevertheless, by taking the remediation efficiency of ethylbenzene and the energy expenditure into account for the overall process performance evaluation, the system SAEK was still a cost-effective alternative treatment method.