{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,14]],"date-time":"2026-08-14T22:26:38Z","timestamp":1786746398524,"version":"build-2736575974"},"reference-count":76,"publisher":"American Chemical Society (ACS)","issue":"13","license":[{"start":{"date-parts":[[2020,6,3]],"date-time":"2020-06-03T00:00:00Z","timestamp":1591142400000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-029"},{"start":{"date-parts":[[2020,6,3]],"date-time":"2020-06-03T00:00:00Z","timestamp":1591142400000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-037"},{"start":{"date-parts":[[2020,6,3]],"date-time":"2020-06-03T00:00:00Z","timestamp":1591142400000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-045"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["41907198"],"award-info":[{"award-number":["41907198"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["41977190"],"award-info":[{"award-number":["41977190"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100017055","name":"NSFC-Shandong Joint Fund","doi-asserted-by":"crossref","award":["U1906215"],"award-info":[{"award-number":["U1906215"]}],"id":[{"id":"10.13039\/100017055","id-type":"DOI","asserted-by":"crossref"}]},{"name":"the International Partnership Program of Chinese Academy of Sciences (Grant No. )","award":["132744KYSB20170002"],"award-info":[{"award-number":["132744KYSB20170002"]}]},{"DOI":"10.13039\/501100013050","name":"Guangdong Foundation for Program of Science and Technology Research","doi-asserted-by":"crossref","award":["2017B030314057"],"award-info":[{"award-number":["2017B030314057"]}],"id":[{"id":"10.13039\/501100013050","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2020,7,7]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>Nitrogen oxide (NOx) abatement has become the focus of air quality management strategies. In this study, we examined NOx sources and the atmospheric conversion of NOx in Karachi, Pakistan, a megacity in South Asia with serious particulate pollution problems. Oceanic contributions to NOx were quantified for the first time based on a novel approach using nitrogen\/oxygen isotopic analysis in nitrate (\u03b415N\u2013NO3\u2013; \u03b418O\u2013NO3\u2013) and a Bayesian model. Our results showed that \u03b415N\u2013NO3\u2013 in Karachi varied between \u221210.2\u2030 and +12.4\u2030. As indicated by the \u03b418O\u2013NO3\u2013 findings (+66.2 \u00b1 7.8\u2030), the \u2022OH pathway dominated NOx conversion throughout the nearly two-year observation, but high NO3\u2013 events were attributed to the O3 pathway. Coal combustion was the most significant source (32.0 \u00b1 9.8%) of NOx in Karachi, with higher contributions in the autumn and winter; a similar situation occurred for biomass burning + lightning (30.3 \u00b1 6.5%). However, mobile sources (25.2 \u00b1 6.4%) and microbial processes (12.5 \u00b1 7.5%) exhibited opposite seasonal trends. The oceanic contributions to NOx in Karachi were estimated to be 16.8%, of which lightning, shipping emissions, and microbial processes accounted for 20.3%, 46.3%, and 33.4%, respectively, emphasizing the dominance of shipping emissions as an oceanic NOx source.<\/jats:p>","DOI":"10.1021\/acs.est.0c00490","type":"journal-article","created":{"date-parts":[[2020,6,3]],"date-time":"2020-06-03T15:03:00Z","timestamp":1591196580000},"page":"7787-7797","source":"Crossref","is-referenced-by-count":33,"title":["Isotopic\nInterpretation of Particulate Nitrate in\nthe Metropolitan City of Karachi, Pakistan: Insight into the Oceanic\nContribution to NO\n                    <i>x<\/i>"],"prefix":"10.1021","volume":"54","author":[{"given":"Zheng","family":"Zong","sequence":"first","affiliation":[{"name":"Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS) , , Shandong Key Laboratory of Coastal Environmental Processes, YICCAS , , ,","place":["Yantai, Shandong, P. R. China, 264003"]},{"name":"Center for Ocean Mega-Science, Chinese Academy of Sciences , No. 7, Nanhai Road , ,","place":["Qingdao\nCity, P. R. China, 266071"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6058-9353","authenticated-orcid":true,"given":"Chongguo","family":"Tian","sequence":"additional","affiliation":[{"name":"Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS) , , Shandong Key Laboratory of Coastal Environmental Processes, YICCAS , , ,","place":["Yantai, Shandong, P. R. China, 264003"]},{"name":"Center for Ocean Mega-Science, Chinese Academy of Sciences , No. 7, Nanhai Road , ,","place":["Qingdao\nCity, P. R. China, 266071"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3637-1642","authenticated-orcid":true,"given":"Jun","family":"Li","sequence":"additional","affiliation":[{"name":"Guangzhou Institute of Geochemistry, Chinese Academy of Sciences , , ,","place":["Guangzhou, China, 510640"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0942-8495","authenticated-orcid":true,"given":"Jabir Hussain","family":"Syed","sequence":"additional","affiliation":[{"name":"COMSATS University Islamabad (CUI) , , Park Road, Tarlai Kalan , ,","place":["Islamabad, Pakistan, 45550"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wei","family":"Zhang","sequence":"additional","affiliation":[{"name":"Yantai University , , , ,","place":["Yantai, Shandong, P. R. China, 264005"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7531-546X","authenticated-orcid":true,"given":"Yunting","family":"Fang","sequence":"additional","affiliation":[{"name":"Institute of Applied Ecology, Chinese Academy of Sciences , , , ,","place":["Shenyang, Liaoning, P. R. China, 110164"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yifan","family":"Jiang","sequence":"additional","affiliation":[{"name":"National University of Singapore , , Block E1A#07-03, No. 1 Engineering Drive 2 , ,","place":["Singapore, Singapore, 117575"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jawad","family":"Nasir","sequence":"additional","affiliation":[{"name":"Pakistan Space and Upper Atmosphere Research Commission (SUPARCO) , , P.O. Box 8402, ,","place":["Karachi, Pakistan, 75270"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Muhammad","family":"Mansha","sequence":"additional","affiliation":[{"name":"Pakistan Space and Upper Atmosphere Research Commission (SUPARCO) , , P.O. Box 8402, ,","place":["Karachi, Pakistan, 75270"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Syed Hussain Haider","family":"Rizvi","sequence":"additional","affiliation":[{"name":"Pakistan Space and Upper Atmosphere Research Commission (SUPARCO) , , P.O. Box 8402, ,","place":["Karachi, Pakistan, 75270"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2570-1722","authenticated-orcid":true,"given":"Muhammad","family":"Shafiq","sequence":"additional","affiliation":[{"name":"Pakistan Space and Upper Atmosphere Research Commission (SUPARCO) , , P.O. Box 8402, ,","place":["Karachi, Pakistan, 75270"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Suhaib Bin","family":"Farhan","sequence":"additional","affiliation":[{"name":"Pakistan Space and Upper Atmosphere Research Commission (SUPARCO) , , P.O. Box 8402, ,","place":["Karachi, Pakistan, 75270"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9010-8140","authenticated-orcid":true,"given":"Gan","family":"Zhang","sequence":"additional","affiliation":[{"name":"Guangzhou Institute of Geochemistry, Chinese Academy of Sciences , , ,","place":["Guangzhou, China, 510640"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2020,6,3]]},"reference":[{"issue":"2","key":"2026081417171205500_cit1","doi-asserted-by":"publisher","first-page":"153","DOI":"10.1007\/s10533-004-0370-0","article-title":"Nitrogen\ncycles: past, present, and future","volume":"70","author":"Galloway","year":"2004","journal-title":"Biogeochemistry"},{"issue":"12","key":"2026081417171205500_cit2","doi-asserted-by":"publisher","DOI":"10.1126\/sciadv.1601530","article-title":"Reactive nitrogen chemistry\nin aerosol water as a source of sulfate during haze events in China","volume":"2","author":"Cheng","year":"2016","journal-title":"Sci. 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