Adverse impacts of fog events during winter on fine particulate matter, CO and VOCs: a case study of a highway near Dhanbad, India

Abstract

AbstractAdverse meteorological conditions due to frequent fog events during the winter period are a primary cause of the sharp increase in the number of cities with high levels of air pollution, especially in terms of fine particulate matter. Dense fog events were recorded over Dhanbad, in the eastern part of India, during January 2015. Variations in particulate matter (mass/number) concentrations and gaseous pollutant concentrations (carbon monoxide (CO), and volatile organic compounds (VOCs)) during foggy days were studied. Elevated ambient concentrations of air pollutants during foggy days were observed, due to high relative humidity (RH), low temperature (T) and stagnant wind conditions. During fog events, the average mass concentrations of particulate matter smaller than 1μm (PM1), 2.5μm (PM2.5), and 10μm (PM10) were observed to be 352, 394 and 497μgm−3, respectively. During fog events, high mass fractions of PM1 (72%) and PM2.5 (82%) in PM10 were observed. However, during normal winter days in January 2015 smaller fractions of PM1 (43%) and PM2.5 (57%) in PM10 were observed. This clearly indicates that fog events were responsible for the creation of additional fine particles (PM1–2.5) in the atmosphere due to adverse meteorological conditions. During fog events the levels of CO and VOCs were found to rise by 88 and 81%, respectively, relative to a normal winter day in January 2015. Similarly, particle number concentrations in the accumulation mode (265–900nm) were observed to be higher on foggy days compared to normal winter days in January 2015. Overall, this study finds that foggy conditions affected PM1–2.5 fractions considerably, and moderately affected levels of CO and VOCs.