10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Oxidative Potential of Ambient Fine Aerosol during Intense Biomass Burning over the Indo-Gangetic Plain-India
ANIL PATEL, Rangu Venkata Satish, Atinderpal Singh, Darshan Singh, Neeraj Rastogi, Physical Research Laboratory, Ahmedabad, India
Abstract Number: 475 Working Group: Aerosols and Health - Connecting the Dots
Abstract Emissions from biomass burning (BB) are dominant global source for carbonaceous aerosol and gases in the atmosphere. On regional scale, the emission budget reveals that nearly 400 Gg of particulate organic carbon (OC) are produced per year from post-harvest paddy-residue burning emissions in the Indo-Gangetic Plain (IGP). Particulate matter (PM) from BB, mostly comprised of fine carbonaceous aerosol, may have significant impact on regional air quality and human health as they are capable of penetrating into the alveolar region and might absorbed into the blood stream of the human body that may cause various cardio-pulmonary diseases. A widely accepted proposed mechanism related to the effect of PM on human health is that inhaled ambient PM generates reactive oxygen species (ROS), which further cause cellular damage and induce oxidative stress in human. Capacity of PM to generate ROS is termed as their oxidative potential (OP). A variety of cellular and acellular assays have been developed to quantify different aspects of PM-induced oxidative stress based on the possible mechanistic route linking aerosol chemistry to health.
In present study, daytime and nighttime PM2.5 (PM with aerodynamic diameter less than or equal to 2.5µm) samples (n = 69) were collected on tissuquartz filters using high volume air sampler during October–November, 2014 over a semi-urban site (Patiala: 30.2°N; 76.3°E, 250m amsl) in the IGP, India. In parallel, the mass concentration of black carbon (BC) was also determined with seven wavelengths Aethalometer. Study period covers the ambient air conditions of the study region before, during and after a large scale post-harvest paddy-residue burning to assess the effect of biomass burning emissions on the OP of aerosol. Filter samples were analyzed for major anions, cations, organic carbon (OC) and elemental carbon (EC), water soluble organic carbon (WSOC), sugars including levoglucosan, and trace metals. Further, a widely used dithiothreitol (DTT) assay was used to measure the OP of soluble ambient PM2.5.
Volume normalized OP (OP m-3) is found to be highly correlated (R2 ≥ 0.70, p<0.05) with many BB markers such as OC/EC, K+/EC, BC370/BC880, and levoglucosan, which attests that observed OP is mainly due to species emitted from BB. OP m-3 exhibited a positive significant correlation with ambient PM2.5 mass concentration during paddy-residue burning period (m=0.037, R2=0.78, p<0.05) with ~ 2 times higher slope compared to that reported for winter (Jan-2014, m=0.017, R2=0.44, p<0.05) from the same site. It is attributable to dominant contribution of species from BB to PM2.5 during study period, which should have higher OP. However, mass normalized OP (OP µg-1) was found to be increasing during post-burning period, which suggests that the aging and/or atmospheric processing of PM species from BB increase their OP. Further, OP µg-1 is found to be significantly correlated with ratio of WSOC to secondary inorganic aerosol (SIA) in daytime samples collected during paddy-residue burning (m=25, R2=0.59, p<0.05, N=16) with ~ 5 times lower slope than that observed during winter 2014. WSOC during winter was reported to be predominantly of secondary origin whereas during this study, it was mixture of primary (from BB) and secondary sources. This observation suggests that WSOC formed through secondary processes are more DTT active than those emitted directly from primary sources. Such studies have implications in understanding the role of PM from BB emissions on air quality and atmospheric chemistry over a given study region, and designing appropriate mitigation strategies.