Analysing the anomalous relationship between precipitation and PM10 concentrations in Peninsular India

Department of Environmental Engineering, Delhi Technological University, New Delhi, India

^* Corresponding author: lgupta@dce.ac.in

Abstract

Global air quality trends suggest decreased PM10 levels with increased precipitation, however, Peninsular India exhibits a distinct pattern. This research investigates the correlation between precipitation and PM10 concentrations in Peninsular India, with special focus on the anomalous relationship between the two variables, where rainfall does not consistently lead to lower PM10 concentration levels. The study examines data from 11 air quality monitoring stations across four states, considering PM10 concentrations, precipitation intensities and meteorological data of wind. Statistical analyses were employed to study the distribution patterns of PM10 mass concentrations corresponding to the type of rainfall during the monsoon season in every city of research. To investigate further, the correlation between PM10 levels before the rainfall and the average precipitation intensity during the rainfall duration was established. Results have revealed that the impact of precipitation on PM10 concentration levels varies depending upon the pollutant’s concentration before the rainfall duration and precipitation intensities. Light rainfall (precipitation intensity between 2.5 mm/day to 7.6 mm/day) leads to a decrease in PM10 concentration levels in particular meteorological conditions, whereas very light rainfall (precipitation intensity less than 2.5 mm/day) increases the PM10 concentration levels post rainfall. The scavenging effect of precipitation is investigated by measuring the difference in PM10 concentration levels before and after a certain precipitation intensity. When initial PM10 concentration is lower than the seasonal average, results show a little increase in PM10 concentration levels after a light rainfall lasting less than 10 hours. This research also explores the fluctuations in the PM10 concentration levels under different wind directions and speeds. It is observed that increasing wind speed in one direction improves the clearance effect on PM10 concentrations. The objective of this research is to close the knowledge gap between regional meteorological conditions (primarily related to precipitation and wind dynamics) and regional air quality by offering data-backed observations. This facilitates effective air pollution management for such disparate air quality patterns.