Long-term observations of black carbon aerosol over a rural location in southern peninsular India: Role of dynamics and meteorology. (September 2018)

• Record Type: Journal Article
• Authors: Ravi Kiran, V.; Talukdar, S.; Venkat Ratnam, M.; Jayaraman, A.
• Is Part Of: Atmospheric environment. Volume 189(2018)
• Page Start: 264
• Page End: 274
• Publication Date: 2018-09
• Subjects: Black carbon -- Long-term trends -- Fossil fuel -- Bio-mass burning; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2018.06.020
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: Ten years (2008–2017) of Black Carbon (BC) observations obtained using Aethalometer (AE-31) are analyzed to investigate the seasonal trends and temporal variabilities over a tropical site Gadanki (13.5° N, 79.2° E) located in south-east India. Diurnal variations of BC have two peak structures one in the morning (∼08 IST) in all seasons and second in the evening (∼20 IST) only during the pre-monsoon (March–May). Intra-annual variation in BC indicated February and March months as the bio-mass burning with highest BC mass concentration (3000–5000 ng/m 3 ). About 46% of air parcel back trajectories found passing across the in-land regions of southern peninsular India brining transported aerosol to the source location during pre-monsoon. The lowest BC (∼1500 ng/m 3 ) is noticed during the monsoon months (June–September). The average BC (2200 ng/m 3 ) represents observational site as a typical rural site. The inter-annual variability of BC did not show any significant trend. However, trends in the maximum (March) and minimum (July) BC values show statistically significant decreasing trend suggesting reduction in bio-mass burning sources during March supported by the decrease in the fire counts. Diurnal variation in the absorption angstrom exponent indicates that the morning and evening peaks are contributed by the bio-mass combustion with values above threshold of 1. However, angstrom exponent values are found below 1 during noon time of monsoon season suggesting fossil fuel contribution. Strong coupling is found between aerosol concentration and tropospheric dynamics, meteorology in addition to the sources. The present study is expected to provide valuable input to the modelers and observational physicists as BC is climate sensitive variable. Highlights: 10 years of BC observations over a rural location are reported for the first time. Significant decreasing trend is found in the highest and lowest values of BC. Strong association of BC with dynamics and meteorology is found. Angstrom exponent values suggest fossil fuel combustion as a dominant source.