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

Observations on a particulate matter (PM10 and PM2.5) 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 PM2.5/PM10, impacts of local meteorological parameters on the concentration of PM are examined. PM10 showed a maximum concentration during pre-monsoon, whereas PM2.5 showed it in winter. The monsoon season showed the lowest concentrations for both PM10 and PM2.5. 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 PM2.5/PM10 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.