Occurrence and source characterization of perfluorochemicals in an urban watershed

Perfluorochemicals (PFCs) are used in numerous applications, mainly as surfactants, and occur ubiquitously in the environment as complex mixtures. This study was undertaken to characterize the occurrence and sources of commonly detected PFC compounds in surface waters of the Marina catchment, a watershed that drains an urbanized section of Singapore. Of the 19 target PFCs, 13 were detected with perfluorooctanoic acid (PFOA) (5-31 ng L⁻¹) and perfluorooctane sulfonate (PFOS) (1-156 ng L⁻¹) being the dominant components. Other compounds detected included perfluoroalkyl carboxylates (C7-C12) and perfluoroalkyl sulfonates (C6 and C8). Sulfonamide compounds detected 2-(N-ethylperfluorooctanesulfonamido) acetic acid (N-EtFOSAA), 2-(N-methylperfluorooctanesulfonamido) acetic acid (N-MeFOSAA), perfluorooctanesulfonamido acetic acid (FOSAA) and perfluorooctanesulfonamide (FOSA) were putative transformation products of N-EtFOSE and N-MeFOSE, the N-ethylated and N-methylated ethyl alcohol derivatives, respectively. Surface water concentrations were generally higher during dry weather than during storm water flow: the median concentrations of total PFCs in dry and wet weather were 57 and 138 ng L⁻¹ compared to 42 and 79 ng L⁻¹, respectively, at Stamford and Alexandra canal, suggesting the presence of a continuous source(s) which is subject to dilution during storm events. In rain water, median concentrations were 6.4 ng L⁻¹, suggesting rain contributed from 12-25% to the total PFC load for non-point source sites. The longitudinal concentration profile along one of the canals revealed a point source of sulfonated PFCs (PFOS), believed to originate from aqueous film-forming foam (AFFF). Sources were characterized using principal component analysis (PCA) and by plotting PFHxS/PFOA against PFOS/PFOA. Typical surface waters exhibit PFOS/PFOA and PFHxS/PFOA ratios below 0.9 and 0.5, respectively. PCA plots reveal waters impacted by “non-typical” PFC sources in Alexandra canal.     

Determination of polycyclic aromatic hydrocarbons in urban street dust: implications for human health

The determination of sixteen polycyclic aromatic hydrocarbons in urban street dust has been done. Samples were collected from 12 sampling locations in a city centre location (Newcastle upon Tyne, north east England) and extracted using in situ pressurised fluid extraction followed by gas chromatography mass spectrometry. From the results it was possible to identify three groups, with respect to PAH concentration, with PAH contents ranging between 0.6-2.3 mg kg⁻¹, 15.6-22.5 mg kg⁻¹ and 36.1-46.0 mg kg⁻¹. The total PAH content of samples from these sampling sites has been compared to 22 urban locations around the world; comparable levels were found in these samples compared to the other cities around the world.The potential source of PAHs has been investigated by investigating the proportion of pyrogenic and petrogenic material in urban street dust using specific individual PAH ratios. The results indicate that the PAH content of urban street dust from the chosen sites are more likely to be due to pyrogenic sources i.e. vehicle exhaust emissions. The particle size fractions (<63 μm; 63-125 μm; 125-250 μm; 250-500 μm; 500-1000 μm; and 1000-2000 μm) of individual PAHs in three selected sampling sites was investigated. In two of the selected sites the PAH content was independent of particle size whereas in sampling site 10 elevated PAH levels are noted in the <63 μm size fraction. Sampling site 10 is located at the junction of three road tributaries which are used as major access points to the east of the city centre. Finally, the potential health risk for unintentional consumption of PAHs was assessed in terms of a mean daily intake (based on an ingestion rate of 100 mg d⁻¹). It was found that all 4-6 membered ring PAHs had concentrations in excess of the mean daily intake thereby reflecting a potential health risk, particularly in the smallest size particle fractions.     

A holistic life cycle analysis of waste management scenarios at increasing source segregation intensity: The case of an Italian urban area

Life cycle analysis of several waste management scenarios for an Italian urban area was performed on the basis of different source segregation collection (SS) intensities from 0% up to 52%. Source segregated waste was recycled and or/recovered by composting. Residual waste management options were by landfilling, incineration with energy recovery or solid recovered fuel (SRF) production to substitute for coal. The increase in fuel and materials consumption due to increase in SS had negligible influence on the environmental impact of the system. Recycling operations such as incineration and SRF were always advantageous for impact reduction. There was lower impact for an SS of 52% even though the difference with the SS intensity of 35% was quite limited, about 15%. In all the configurations analyzed, the best environmental performance was achieved for the management system producing SRF by the biodrying process.     

基于城市用地单元的自然灾害风险评估概念模型

为使城市土地利用规划与灾害风险管理更好地结合,从城市规划的基础单元———城市用地系统出发,提出基于城市用地单元的区域综合自然灾害风险评估的概念模型。基于城市用地单元的灾害风险评估,包括城市土地利用单元上潜在致灾因子及承灾体自然脆弱性相结合的灾损风险评估,以及人口、经济、社会因素等所引起的社会脆弱性评估2个方面。通过耦合矩阵,得到5个等级的灾害风险。其中,灾损风险与脆弱性均较高的城市用地单元或区域应得到高度关注。基于城市土地利用单元的灾害风险评估模型的应用关键,在于建立城市用地单元的数据库。提高基础数据的精度,有助于提高评估结果的精度。     

城市环境管理信息系统的应用与技术

介绍并讨论了地理信息系统在环境方面的应用及技术，根据我国大城市环境污染现状和环境管理的特点，提出了在地理信息系统技术的支持下．利用数据仓库，建立城市环境污染控制的动态管理系统。     

城市有机固体废弃物联合厌氧发酵技术及工程应用

根据城市有机固体废弃物的组成、特性和处理现状,在大量小试和中试研究基础上,开发出以"联合厌氧发酵工艺"为核心的城市有机固体废弃物综合处理技术。本文介绍了该技术的实际工程应用状况,并对该技术的工艺组成、特点及主要性能参数进行了分析。工程实践证明,该技术能够将污染物处理和能源回收利用相结合,真正实现城市有机固体废弃物的减量化、无害化和资源化。     

广州市城市垃圾终处理的现状及发展策略

结合广州市自然地理,社会经济条件,概括总结了广州市垃圾产出特点及垃圾终处理的发展阶段,重点分析了现有垃圾填埋场存在的问题及产生原因。在此基础上,提出了广州市垃圾终处理要“四个坚持”的发展策略。      

重庆城市交通环境现状调查及治理对策

首先介绍了交通环境问题的定义，指出了城市是交通环境问题研究的重点。然后，以重庆市为典型，通过一系列调查资料，介绍了重庆市的城区机动车污染排放、交通噪声和交通扬尘的现状，并对重庆市的交通环境现状进行了较深入的分析和研究，同时针对污染原因，给出了治理对策和建议。最后，作者呼吁全社会关注和爱护城市交通环境。     

村镇生活垃圾热解处理技术综述

村镇生活垃圾处理是关系环境生态、经济民生的重要问题,是我国发展生态文明、建设美丽乡村的重要环节.新形势下,村镇生活垃圾处理不仅要求减量化、无害化,同时应实现就近、就地处理,资源、能源回用.本文综述了我国村镇生活垃圾产量与分布特性,对比分析当前村镇生活垃圾的处理模式与常用技术.热解技术是一项新兴的村镇生活垃圾技术.针对村镇生活垃圾热解工艺,从过程控制、产物导向、装备设计、研究前沿等角度展开全方位分析,列举相关政策法规,并对现有应用示范进行梳理分析.     

生态城市建设中城市水景观建设存在的误区及对策

城市水景观建设作为实现生态城市建设目标的系统工程与城市水资源、土地资源、生态环境等息息相关,是关系到城市水环境安全和可持续发展的战略问题。本文分析了城市水景观在建设中存在的两大误区,并提出了科学、合理建设城市水景观的相关对策。