Concentration, distribution and source apportionment of atmospheric polycyclic aromatic hydrocarbons in the southeast suburb of Beijing, China

Total suspended particle samples and gas phase samples were collected at three representative sampling sites in the southeastern suburb of Beijing from March 2005 to January 2006. The samples were analyzed for 16 US EPA priority PAHs using GC/MS. Concentrations of Sigma PAHs in particle and gas phases were 0.21-1.18 x 10(3) ng m(-3) and 9.5 x 10(2) ng-1.03 x 10(5) ng m(-3), respectively. PAH concentrations displayed seasonal variation in the order of winter>spring>autumn>summer for particle phase, and winter>autumn>summer>spring for gas phase. Partial correlation analysis indicates that PAH concentrations in particle phase are negatively correlated with temperature and positively correlated with air pollution index of SO(2). No significant correlation is observed between gas phase PAHs and the auxiliary parameters. Sources of PAH are identified through principal component analysis, and source contributions are estimated through multiple linear regression. Major sources of atmospheric PAHs in the study area include coal combustion, coke industry, vehicular emission and natural gas combustion.     

好氧颗粒污泥强化解体实验与机理研究

在120r／min的搅拌及pH=1的强酸条件下,进行好氧颗粒污泥的强化解体实验,研究颗粒污泥的总数、平均粒径和粒径分布的变化情况。在15h实验时间内,搅拌强化解体的颗粒平均粒径从1230μm降至320μm,颗粒总数从30个／mL增至193个／mL。强酸强化解体结果类似,但解体时间为110h。搅拌比强酸对颗粒解体的强化作用更明显。粒径分布结果显示,小颗粒所占比例明显增加。颗粒解体过程中粒径分布均符合对数正态分布,但颗粒粒径的期望值石,随解体时间明显减小。根据颗粒的解体机理,即4种解体类型：破碎、破裂、剥落和研磨,结合实验结果,将解体过程分为对数期、平缓期、二次对数期和稳定期。     

Bio-SR工艺去除硫化氢气体的研究

采用Bio-SR工艺,利用铁盐吸收与氧化亚铁硫杆菌的联合作用对H2S进行脱除实验。通过改进微生物的培养条件,减少了83.9%的沉淀量,一定程度上解决了挂膜后生物填料塔易堵塞的问题,保证了填料塔的连续运行。在实验选取工况下,硫化氢脱除率可达到98.4%以上,当吸收液中Fe3+浓度为5.5～6 g/L、H2S进气浓度为1 g/m3、通气量为0.08～0.12 m3/h时效果最佳,反应器可持续高效地运行。此外,对进气浓度、通气量与硫化氢去除率之间的相关性进行了进一步研究,其结果有利于反应器及运行参数的优化设计。     

城市污泥桨叶式干化优化实验研究

桨叶式干化是一种高效的污泥干化处理技术,为了降低污泥含水率达到污泥减量减容效果,同时为后期的工程化应用提供依据和参考,实验采用倾斜盘式桨叶干燥机,以北京市污水处理厂污泥为研究对象,研究了不同滞留时间、污泥供给量、干燥机换热面积等因素对桨叶式干化处理后蒸发速度和污泥含水率的影响,并从处理效率以及与工程化应用数据对比分析等多方面考核,确定最佳工艺运行条件：使用0．5—0．8MPa的蒸气,蒸发速率达到14～21．8kg／（m^2·h）时,干化处理后污泥含水率〈40％。     

印刷用铝基材碱洗废液的循环利用

对印刷用铝基材碱洗废液进行了循环利用研究。首先将高COD含量的碱洗废液进行除油脱色处理,通过石灰和硬脂酸的协同效应,使COD含量从26300mg／L降至480mg／L,色度降至60°;然后利用含铝碱性废液通过碳化法制备出结晶度66％的拟薄水铝石产品;最后对分离后的碱性废水按配方要求配制,对铝基材进行除油实验,经5次循环表明,除油效果和对铝基材的腐蚀率均100％达标。     

Nitrogen Dioxide Absorption and Sulfide Oxidation in Aqueous Sulfide

ABSTRACT

Rates of nitrogen dioxide (NO₂) absorption and sulfide oxidation were measured in a highly characterized stirred cell contactor at 55 °C, with O₂ present in the gas phase. The rate constant of the reaction between NO₂ and sul-fide at 55 °C was determined to be 26.4 x10⁵ M^-1sec^-1. A reaction mechanism was proposed that is consistent with the kinetic data. NO₂ absorption initiates sulfide oxidation in the presence of oxygen. The rate of sulfide oxidation increased with sulfide and oxygen concentration and with the rate of NO₂ absorption. Furthermore, thiosulfate was an effective inhibitor of sulfide oxidation.     

A Comparison of Nonlinear Regression and Neural Network Models for Ground-Level Ozone Forecasting

ABSTRACT

A hybrid nonlinear regression (NLR) model and a neural network (NN) model, each designed to forecast next-day maximum 1-hr average ground-level O₃ concentrations in Louisville, KY, were compared for two O₃ seasons—1998 and 1999. The model predictions were compared for the forecast mode, using forecasted meteorological data as input, and for the hindcast mode, using observed meteorological data as input. The two models performed nearly the same in the forecast mode. For the two seasons combined, the mean absolute forecast error was 12.5 ppb for the NLR model and 12.3 ppb for the NN model. The detection rate of 120 ppb threshold exceedances was 42% for each model in the forecast mode. In the hindcast mode, the NLR model performed marginally better than the NN     

Trends in Meteorologically Adjusted Ozone Concentrations in Six Kentucky Metro Areas, 1998–2002

Abstract

Meteorologically adjusted ozone (O₃) concentrations during five recent O₃ seasons (1998-2002) were computed for six Kentucky metro areas using a nonlinear regression model originally developed for forecasting ground-level O₃ concentrations. The meteorological adjustment procedure was based on modifying actual measured O₃ concentrations according to model-predicted responses to climate departures with respect to a reference year. For all six Kentucky metro areas, meteorologically adjusted O₃ concentrations declined over the five-year period. The linear best-fit rate of decline in mean adjusted O₃ concentrations ranged from 0.9 to 2.6 ppb/yr for these metro areas; the average rate of decline was 1.6 ppb/yr. The rates of decline in meteorologically adjusted extreme value (e.g., 95th percentile) concentrations were approximately the same, but there is greater statistical uncertainty concerning the extreme value trends.     

Aquatic plant debris improve phosphorus sorption into sediment under anoxic condition

The effects of plant debris on phosphorus sorption by anoxic sediment were investigated. Addition of plant debris significantly enhanced the decrease of soluble relative phosphorus (SRP) in overlying water at both 10 and 30 °C during the 30-day investigation. Both cellulose and glucose, two typical plant components, also clearly enhanced the SRP decrease in anoxic overlying water. The measurement of phosphorus (P) fractions in sediment revealed that the levels of unstable P forms were decreased by plant debris addition, whereas the opposites were true for stable P forms. However, under sterilized condition, plant debris/glucose addition has no effect on the SRP decrease in overlying water. Overall, our results suggested that plant debris improve P sorption into sediment under anoxic condition through a microorganism-mediated mechanism.     

一株高效MC—RR降解菌的分离鉴定及其降解特性

为了得到一株具有降解微囊藻毒素一RR（MC—RR）特性的产芽孢菌株,采用加热富集芽孢菌的方法,从太湖分离到一株MC．RR降解菌CMl,该菌对MC—RR具有强烈的降解特性。通过形态学特征、生理生化特征及16SrDNA序列分析鉴定该菌株属于耐硼赖氨酸芽孢杆菌（Lysinibacillusb oronitolerans）。通过研究温度和pH值对菌株CMl降解MC—RR能力的影响,发现菌株CMl在60h将MC—RR由12．77μg／mL降解到1．67μg／mL,降解率达86．90％,最适降解温度为37℃,最适pH值为7．0。CMl菌株的胞外物质和胞内物质均能降解MC—RR,但胞内物质具有更强烈的降解特性,12h可以将7．27μg／mL的MC-RR完全降解。为丰富MC-RR降解菌纯菌种研究以及在去除水体中MC—RR应用研究方面提供了理论基础。