Oxidative potential of atmospheric PM_(10) at five different sites of Ahmedabad, a big city in Western India

摘要

The current study presents the oxidative potential (OP) along with a wide range of chemical speciation of particulate matter with an aerodynamic diameter less than 10 mm (PM10) at five sites representing different environments in Ahmedabad, a big city in western India. On an average, PM10 concentrations were 116 +/- 36, 228 +/- 43, 133 +/- 29, 101 +/- 21, and 70 +/- 20 mu g m(-3); volume-normalized OP (OPV) were 2.51 +/- 0.71, 5.62 +/- 0.68, 2.69 +/- 0.76, 2.14 +/- 0.41, and 1.55 +/- 0.51 nmol DTT min(-1) m(-3); and massnormalized OP (OPM) were 22 +/- 3, 25 +/- 5, 21 +/- 6, 21 +/- 2, and 22 +/- 3 pmol DTT min(-1) mg(-1) over Bapunagar (backward residential area), Narol (industrial), Paldi (bus transport hub), Income Tax (huge running traffic) and Science City (posh residential area), respectively. Overall, OPV showed a significant linear correlation with PM10, whereas OPM showed near uniformity with increasing PM10. Although the OPM values were similar, the site-to-site variability in PM10 concentration reflects the corresponding health risks associated with PM10 exposure for the people living in these areas. Further, a noticeable temporal variation in OPM at Narol and Paldi suggests that species with diverse OPM contributed to PM10 on different days. A strong linear relationship between the ratio of OPV to the mass concentration of organic carbon (OPOC) and the ratio of m/z 43 signal to total water-soluble organic aerosols (WSOA) signals (f43) suggests that the fossil-fuel combustion derived WSOA have higher OP. Furthermore, the relationships of OP with water-soluble trace metals and brown carbon are also investigated and discussed in this paper. Nitrogenous organic compounds particularly emitted from the traffic-related sources in Paldi and Income Tax have higher OPOC than those emitted from other sources over Bapunagar, Narol, and Science City. (C) 2020 Elsevier Ltd. All rights reserved.