Diffusion of municipal wastewater treatment technologies in China: a collaboration network perspective

The diffusion of municipal wastewater treatment technology is vital for urban environment in developing countries. China has built more than 3000 municipal wastewater treatment plants in the past three decades, which is a good chance to understand how technologies diffused in reality.We used a data-driven approach to explore the relationship between the diffusion of wastewater treatment technologies and collaborations between organizations. A database of 3136 municipal wastewater treatment plants and 4634 collaborating organizations was built and transformed into networks for analysis. We have found that: 1) the diffusion networks are assortative, and the patterns of diffusion vary across technologies; while the collaboration networks are fragmented, and have an assortativity around zero since the 2000s. 2) Important projects in technology diffusion usually involve central organizations in collaboration networks, but organizations become more central in collaboration by doing circumstantial projects in diffusion. 3) The importance of projects in diffusion can be predicted with a Random Forest model at a good accuracy and precision level. Our findings provide a quantitative understanding of the technology diffusion processes, which could be used for waterrelevant policy-making and business decisions.

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Comparison of sequential with intimate coupling of photolysis and biodegradation for benzotriazole

Benzotriazole (BTA) is an emerging contaminant that also is a recalcitrant compound. Sequential and intimate coupling of UV-photolysis with biodegradation were investigated for their impacts on BTA removal and mineralization in aerobic batch experiments. Special attention was given to the role of its main photolytic products, which were aminophenol (AP), formic acid (FA), maleic acid (MA), and phenazine (PHZ). Experiments with sequential coupling showed that BTA biodegradation was accelerated by photolytic pretreatment up to 9 min, but BTA biodegradation was slowed with longer photolysis. FA and MA accelerated BTA biodegradation by being labile electron-donor substrates, but AP and PHZ slowed the rate because of inhibition due to their competition for intracellular electron donor. Because more AP and PHZ accumulated with increasing photolysis time, their inhibitory effects began to dominate with longer photolysis time. Intimately coupling photolysis with biodegradation relieved the inhibition effect, because AP and PHZ were quickly biodegraded and did not accumulate, which accentuated the beneficial effect of FA and MA.

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Feasibility of bubble surface modification for natural organic matter removal from river water using dissolved air flotation

A novel, functionalized bubble surface can be obtained in dissolved air flotation (DAF) by dosing chemicals in the saturator. In this study, different cationic chemicals were used as bubble surface modifiers, and their effects on natural organic matter (NOM) removal from river water were investigated. NOM in the samples was fractionated based on molecular weight and hydrophobicity. The disinfection byproduct formation potentials of each fraction and their removal efficiencies were also evaluated. The results showed that chitosan was the most promising bubble modifier compared with a surfactant and a synthetic polymer. Tiny bubbles in the DAF pump system facilitated the adsorption of chitosan onto microbubble surfaces. The hydrophobic NOM fraction was preferentially removed by chitosan-modified bubbles. Decreasing the recycle water pH from 7.0 to 5.5 improved the removal of hydrophilic NOM with low molecular weight. Likewise, hydrophilic organic compounds gave high dihaloacetic acid yields in raw water. An enhanced reduction of haloacetic acid precursors was obtained with recycle water at pH values of 5.5 and 4.0. The experimental results indicate that NOM fractions may interact with bubbles through different mechanisms. Positive bubble modification provides an alternative approach for DAF to enhance NOM removal.

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Polyoxometalates for photocatalytic degradation of aqueous dyestuff solutions and quantitative structure–property relationship study on photolysis rate constants

Polyoxometalate, K₆TiW₁₁O₃₉Sn·7H₂O (TiW₁₁Sn), was synthesized and characterized. TiW₁₁Sn and K₆ZrW₁₁O₃₉Sn·12H₂O (ZrW₁₁Sn) were evaluated for their photocatalytic degradation of triarylmethane (brilliant green and acid blue 9), bisazo (C.I. reactive black 5), and monoazo dyestuffs (C.I. reactive red 24, C.I. reactive red 194, and C.I. reactive orange 5) with natural sunlight in homogeneous aqueous solutions. TiW₁₁Sn and ZrW₁₁Sn effectively and photocatalytically decolorized the dyestuffs. The TiW₁₁Sn- and ZrW₁₁Sn-mediated photocatalytic degradation of the dyestuffs involved a pseudo-first-order reaction and was modeled by Langmuir–Hinshelwood-type kinetics. The observed pseudo-first-order rate constants (K^/) of triarylmethane dyestuffs were generally bigger than that of the azo dyestuffs. Quantitative structure–property relationship models of the K^/ of the dyestuffs were developed using partial least-square regression. The cumulative variance of the dependent variable explained by the partial least-square components was > 0.753 for each optimal model. This value indicated that the model had good predictive ability and robustness. The K^/ values of the dyestuffs were related to the energy of the lowest unoccupied molecular orbital, and the most positive net atomic charges on a sulfur atom of dyestuffs. The linear correlation coefficients between the predicted and experimental values were all > 0.9950.     

废弃农药厂污染场地土壤浸出液的急性毒性和遗传毒性筛查

污染土地再开发是城市土地可持续利用的关键。为进行废弃农药厂的生态风险评价,采集常州市某废弃农药厂污染场地6个不同区域的土壤样品(编号为S1、S2、S3、S4、S5和S6),选取发光细菌、大型溞和蚕豆根尖细胞为试验生物,运用成组生物毒性试验对6个土壤样品的浸出液进行生物毒性检测。结果表明:6个土壤样品的浸出液都具有急性毒性和遗传毒性;发光菌和大型溞急性毒性试验表明,S3和S5的土壤浸出液毒性最高,S6的土壤浸出液毒性最低;蚕豆根尖微核遗传毒性试验表明S3和S5的土壤浸出液毒性最高,S4和S6的土壤浸出液毒性最低。蚕豆根尖微核遗传毒性试验结果与发光菌和大型溞急性毒性效应基本相同,表明成组生物毒性测试法可以用于污染土壤浸出液的毒性评价。污染物质和毒性检测结果的相关性分析结果表明,土壤中所含污染物种类和浓度已经对土壤毒性效应产生影响,结合化学分析与生物毒性检测可为污染场地进行综合评价与风险评估提供依据。     

生态文明建设的关键因素识别

生态文明建设是共创民族伟业、中国圆梦的时代重任,提高生态文明建设水平需要对生态文明建设的关键因素进行分析识别。本文从生态文明意识、生态文明制度和生态文明行为三个方面建立生态文明建设影响因素指标体系,选取全国31个省份2012至2014年的相关数据,运用BP神经网络法降低DEMATEL模型中专家打分建立关联矩阵的主观性,结合摆幅置权法(SW)得出综合重要度,遴选出生态文明建设关键因素。其中,年份最近的2014年计算得出的关键因素按照重要度排序依次为:本级环保能力建设资金使用总额、排污费解缴入库户金额、机动车污染物排放总颗粒物、网站主动公开各类政府环境信息条数和环保系统人员总数。将这些因素按照生态文明的基本内涵划分为三大类,得到3点结论:生态意识虽不起决定性作用,但能强化整个社会的生态文明建设的思想和理念,生态文明意识所占的比例先降后升,不断提高;随着生态文明建设理论和实践经验的丰富,逐渐感受到成熟的制度设计、明确的制度规范才是根本,生态文明制度类别在关键因素中所占的比例越来越高;生态文明行为作为表现形式,随着其他两方面的变化,生态文明行为不断改善,在生态文明建设的关键因素中所占比例下降。本文在生态文明意识方面提出要针对性地帮助和鼓励各级环保部门开展信息公开工作;在生态文明制度方面提出强化环保能力建设资金的监管力度,发挥排污费的真正作用,提升环保系统人员的能力素养,探索新工作思路等举措;在生态文明行为方面提出综合车、油、路等多方面措施防治机动车排放污染等建议。     

某石化废水的综合毒性评价及其处理工艺对毒性的削减规律研究

利用生物毒性测试对环境中的污染物进行生态风险评价,是目前风险评价中的研究热点。本研究以明亮发光杆菌(Photobacterium phosphoreum)、斜生栅藻(Scenedesmus obliquus)和大型溞(Daphina magna)为受试生物,对某石化厂废水的处理流程中5个主要单元出水的急性毒性进行了测试,分析了其急性毒性与理化指标间的相关性;同时,为了解不同处理单元毒性去除效果及主要毒性来源,结合毒性鉴别评价(toxicity identification evaluation,TIE)技术对各阶段出水的毒性削减及其主要致毒物质类别进行了分析。毒性测试结果表明,该废水处理厂对石化废水的毒性去除效果比较显著,其中进水对明亮发光杆菌、斜生栅藻和大型溞分别表现为中毒、高毒和剧毒,最终处理后出水的毒性分别为无急性毒、中毒和微毒,对毒性的去除效率分别为96.4%、74.3%和99.5%。TIE结果表明,石化废水中的主要致毒物质是非极性有机物和可滤型物质。本研究结果为石化废水的综合生物毒性评价提供了研究基础,为探讨废水生物毒性的去除提供了实例参考。     

环氟菌胺的水解动力学研究

为明确环氟菌胺的水解动力学规律,采用室内模拟试验方法,探究了温度、p H值、表面活性剂和不同种类水体对环氟菌胺水解的影响。结果表明:随着温度的升高,环氟菌胺的水解速率加快;环氟菌胺在碱性条件下降解最快;十二烷基磺酸钠(sodium dodecyl sulfonate,SDS)抑制环氟菌胺的水解;腐植酸的浓度低于1 mg·L-1时促进环氟菌胺的水解,浓度高于1 mg·L-1时抑制环氟菌胺的水解;环氟菌胺在不同水体中的水解速率顺序为:海水>江水>河水,环氟菌胺在自然条件下的降解速率显著高于室内模拟条件。     

Light absorption by water-soluble organic carbon in atmospheric fine particles in the central Tibetan Plateau

Environmental Science and Pollution Research - Brown carbon (BrC) has recently received much attention because of its light absorption features. The chemical compositions, optical properties, and...     

基于GIS和贡献权重迭加方法的区域滑坡灾害易损性评价

区域滑坡易损性是指特定区域对滑坡灾害的破坏和损害的敏感性.根据易损性指标的科学性、可操作性以及可定量化等基本选取依据和研究区的区域特点,选择了人口密度、道路密度、建筑密度、林地密度、耕地密度、滑坡灾害密度6个指标.探讨了贡献率方法评价区域滑坡易损性的建模过程和数学表达.区域滑坡易损性定量表达为各指标的自权重与互权重以及指标的归一化值的乘积.以四川米易县为研究实例,对此评价方法进行了应用,在GIS系统中运用自然断点法进行了易损度区划和区划制图,结果显示,高易损度区、中易损度区、低易损度区分别占研究区域的7.13%、21.19%、71.68%,易损性分布基本上与人口密度、建筑密度和道路密度分布相一致,反应了基于贡献率的区域滑坡灾害易损性区划的合理性.