Assessment of Seasonal Variations of Average Traffic Pollution Levels in Curbside Open-Air Microenvironments in Kolkata, India

Traffic is a source of both noise and air pollution, contributing more than 50% of the total environmental noise and air pollution load of urban areas..
The objective of the research was evaluation of seasonal variations of the average traffic pollution level (ATPL) in terms of traffic noise and concentrations of PM2.5 and NO2 in curbside open-air microenvironments in Kolkata, India..
Number of total motorized vehicles (TMV) traffic noise, and PM2.5 and NO2 concentrations were monitored repeatedly in the microenvironments of 21 major roads between 08:00 a.m. and 08:00 p.m. in the post-monsoon (winter) and pre-monsoon (summer) seasons. Simultaneous data on air temperature, relative humidity, and wind speed were collected from a roof-top automated weather monitoring station. The exceedance factor (EF) was calculated for traffic noise level and concentrations of PM2.5 and NO2. The average exceedance factor (AEF) was calculated to determine ATPL of the microenvironments in terms of traffic noise level and air pollutant concentrations. Interseasonal variations between the same variables were assessed with post-monsoon to pre-monsoon (W/S) ratio and correlation analysis..
ATPL was 3.35 times higher in the post-monsoon and 1.83 times higher in the pre-monsoon season than the permissible limits prescribed by the central pollution control board of India with respect to traffic noise level and PM2.5 and NO2 concentrations. W/S ratio and interseasonal correlation were 1.03 and 0.95, respectively, for TMV; 1.00 and 0.68 for traffic noise level; 2.40 and -0.11 for PM2.5 concentration; 1.74 and 0.19 for NO2 concentration; and 1.92 and 0.01 for AEF..
ATPL was higher in the post-monsoon season. W/S ratio and correlation analysis revealed interseasonal homogeneity of TMV and traffic noise levels and interseasonal heterogeneity of air pollutant concentrations and ATPL in the city microenvironments..