Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; School of Science, University of Chinese Academy of Sciences, Beijing 100049, China; Kathmandu University, Dhulikhel, Nepal.
Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China.
Sci Total Environ. 2018 Mar 15;618:1583-1590. doi: 10.1016/j.scitotenv.2017.09.329. Epub 2017 Oct 18.
Atmospheric polycyclic aromatic hydrocarbons (PAHs) in urban areas have always been a global concern, as these areas are considered to be the source region. Despite studies on the concentrations of PAHs in water, soils and sediments, knowledge of the distribution patterns, seasonality and sources of PAHs in urban areas of Nepal remains limited. In this study, polyurethane foam passive air samplers were used to measure gas-phase PAH concentrations over different land types in three major cities of Nepal-namely, Kathmandu (the capital) and Pokhara (both densely populated cities), and Hetauda (an agricultural city). The average concentrations of ∑15PAHs in ng/m were 16.1±7.0 (6.4-28.6), 14.1±6.2 (6.8-29.4) and 11.1±9.0 (4.1-38.0) in Kathmandu, Pokhara and Hetauda, respectively. Molecular diagnostic ratio analysis suggested that fossil fuel combustion was a common PAH source for all three cities. In addition to this, coal combustion in Kathmandu, vehicle emissions in Pokhara, and grass/wood combustion in Hetauda were also possible sources of PAHs. In terms of cancer risk from PAH inhalation, a religious site with intense incense burning, a brick production area where extensive coal combustion is common, and a market place with heavy traffic emission, were associated with a higher risk than other areas. There were no clear seasonal trends in atmospheric PAHs. The estimated cancer risk due to inhalation of gas-phase PAHs exceeded the USEPA standard at >90% of the sites.
城市地区的大气多环芳烃（PAHs）一直是一个全球性的关注点，因为这些地区被认为是源区。尽管已经对水中、土壤和沉积物中的 PAHs 浓度进行了研究，但尼泊尔城市地区 PAHs 的分布模式、季节性和来源仍知之甚少。在这项研究中，使用聚氨酯泡沫被动空气采样器测量了尼泊尔三个主要城市——加德满都（首都）、博克拉（人口稠密的城市）和赫特瓦达（农业城市）——不同土地类型上空的气相 PAH 浓度。∑15PAHs 的平均浓度为 16.1±7.0（6.4-28.6）、14.1±6.2（6.8-29.4）和 11.1±9.0（4.1-38.0）ng/m3。分子诊断比分析表明，化石燃料燃烧是三个城市共同的 PAH 来源。除此之外，加德满都的煤炭燃烧、博克拉的车辆排放以及赫特瓦达的草/木燃烧也可能是 PAHs 的来源。就 PAH 吸入的致癌风险而言，一个香火旺盛的宗教场所、一个广泛使用煤炭燃烧的砖厂以及一个交通排放量大的市场，其风险高于其他地区。大气 PAHs 没有明显的季节性趋势。由于吸入气相 PAHs 而导致的癌症风险估计值在超过 90%的地点超过了美国环保署的标准。
