Characterisation of particulate matter at a high-altitude site in southwest India: Impact of dust episodes

Abstarct Observations on a particulate matter (PM 10 and PM 2.5 ) were carried out during March 2015 to February 2017 over a high-altitude location Mahabaleshwar in the Western Ghats region in southwest India. Apart from temporal variation of PM and the ratio of PM 2.5 /PM 10 , impacts of local meteorological parameters on the concentration of PM are examined. PM 10 showed a maximum concentration during pre-monsoon, whereas PM 2.5 showed it in winter. The monsoon season showed the lowest concentrations for both PM 10 and PM 2.5 . Concentrations were significantly reduced in 2016 due to the washout effect from enhanced rainfall during that year. Diurnal variations of PM were related to the variation in a planetary boundary layer, mountain valley winds as well as changes in different local sources. Dominance of primary particles was observed from the PM 2.5 /PM 10 ratio. The Central Pollution Control Board (CPCB) threshold limit for PM was exceeded on several days mainly during pre-monsoon due to transported dust from the Arabian Peninsula and Thar Desert apart from an increase in the tourist activity. A typical case for transported dust event during March 2016 is studied. Organics and sulphate particles showed a significant enhancement during dust event. Overall, the study indicated emissions from mixed sources for PM from local as well as distant source regions over Mahabaleshwar.