The characteristics and local-regional contributions of atmospheric black carbon over urban and suburban locations in Shanghai, China.

Abstract

Black carbon (BC), produced from the incomplete combustion of carbonaceous fuels, has emerged as a major contributor to global climate change with adverse health effects. Based on one-year (2016.06.01-2017.06.30) equivalent black carbon (eBC) measurements, this study analyzed the characteristics of eBC concentrations and the local-regional contributions at an urban site (Pudong, PD) and a suburban site (Qingpu, QP) in Shanghai, China. The results showed that the annual average eBC concentrations were 1.17\u202f±\u202f0.61\u202fμg\u202fm-3 and 2.09\u202f±\u202f0.97\u202fμg\u202fm-3 at PD and QP, respectively. The high eBC concentrations occurred in winter and at weekends both for PD and QP. There were significant negative correlation coefficients between the daily eBC, the daily wind speed (WS) and the daily boundary layer height (BLH) at PD (rws: 0.45, rblh\u202f=\u202f-0.35, p\u202f<\u202f0.01) and QP (rws: 0.49, rblh\u202f=\u202f-0.32, p\u202f<\u202f0.01). And the relative higher eBC concentrations coincided with southerly, southwesterly and westerly winds although these winds had lower frequencies. This could be related to the agricultural fire in these directions during summer harvesttime. The significant partial correlation coefficients of eBC-CO (ru:0.37-0.64, rs:0.18-0.44, p\u202f<\u202f0.01) and eBC-NO2 (ru:0.49-0.74, rs:0.38-0.75, p\u202f<\u202f0.01) could suggest that eBC mainly come from vehicular exhaust emissions in Shanghai. Besides, the higher eBC/PM2.5 (5.29%\u202f±\u202f1.94%) and eBC/CO(0.30%\u202f±\u202f0.14%) at QP indicated the more combustion activities and diesel-powered vehicle emissions in suburban areas. The concentration weighted trajectory (CWT) analysis indicated that the surrounding areas at the junction of Shanghai, Jiangsu, and Zhejiang provinces seemed to be relatively the most important sources outside of Shanghai.