Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China; University of Chinese Academy of Sciences, Beijing, 100049, China; Department of Natural Sciences, 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; University of Chinese Academy of Sciences, Beijing, 100049, China.
Chemosphere. 2018 Jun;200:532-541. doi: 10.1016/j.chemosphere.2018.01.119. Epub 2018 Feb 20.
Due to the high temperature and extensive use of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), tropical cities could act as secondary sources of these pollutants and therefore received global concern. As compared with other tropical cities, studies on the air-soil exchange of OCPs, PCBs and PAHs in tropical Nepali cities remained limited. In the present study, 39 soil samples from Kathmandu (capital of Nepal) and 21 soil samples from Pokhara (second largest city in Nepal) were collected The soil concentrations of the sum of endosulfans (α- and β-endosulfans) ranged from 0.01 to 16.4 ng/g dw. Meanwhile, ∑dichlorodiphenyltrichloroethane (DDTs) ranged from 0.01 to 6.5 ng/g dw; ∑6PCBs from 0.01 to 9.7 ng/g dw; and ∑15PAHs from 17.1 to 6219 ng/g dw. High concentrations of OCPs were found in the soil of commercial land, while, high soil PAH concentrations were found on tourist/religious and commercial land. Combined the published air concentrations, and the soil data of this study, the directions and fluxes of air-soil exchange were estimated using a fugacity model. It is clear that Nepal is a country contributing prominently to secondary emissions of endosulfans, hexachlorobenzene (HCB), and low molecular weight (LMW) PCBs and PAHs. The flux for all the pollutants in Kathmandu, with ∑endosulfans up to 3553; HCB up to 5263; and ∑LMW-PAHs up to 24378 ng m h, were higher than those in Pokhara. These high flux values indicated the high strength of Nepali soils to act as a source.
由于高温和有机氯农药(OCPs)、多氯联苯(PCBs)和多环芳烃(PAHs)的广泛使用,热带城市可能成为这些污染物的二次污染源,因此受到全球关注。与其他热带城市相比,关于尼泊尔热带城市中 OCPs、PCBs 和 PAHs 的气-土交换研究仍然有限。本研究采集了尼泊尔首都加德满都(Kathmandu)的 39 个土壤样本和尼泊尔第二大城市博克拉(Pokhara)的 21 个土壤样本。土壤中硫丹(α-和 β-硫丹)总和的浓度范围为 0.01 至 16.4ng/g 干重。同时,∑滴滴涕(DDTs)的浓度范围为 0.01 至 6.5ng/g 干重;∑6PCB 的浓度范围为 0.01 至 9.7ng/g 干重;∑15PAHs 的浓度范围为 17.1 至 6219ng/g 干重。商业用地的土壤中发现了高浓度的 OCPs,而旅游/宗教和商业用地的土壤中则发现了高浓度的土壤 PAHs。结合已发表的空气浓度和本研究的土壤数据,使用逸度模型估算了气-土交换的方向和通量。显然,尼泊尔是一个对硫丹、六氯苯(HCB)和低分子量(LMW)PCBs 和 PAHs 的二次排放做出重要贡献的国家。加德满都的所有污染物通量都很高,∑硫丹高达 3553ng/m²/h;HCB 高达 5263ng/m²/h;∑LMW-PAHs 高达 24378ng/m²/h,均高于博克拉。这些高通量值表明尼泊尔土壤作为源的强度很高。