Evaluation of coarse and fine particles in diverse Indian environments

The estimates of airborne fine particle (PM_2.5) concentrations are possible through rigorous empirical correlations based on the monitored PM₁₀ data. However, such correlations change depending on the nature of sources in diverse ambient environments and, therefore, have to be environment specific. Studies presenting such correlations are limited but needed, especially for those areas, where PM_2.5 is not routinely monitored. Moreover, there are a number of studies focusing on urban environments but very limited for coal mines and coastal areas. The aim of this study is to comprehensively analyze the concentrations of both PM₁₀ and PM_2.5 and develop empirical correlations between them. Data from 26 different sites spread over three distinct environments, which are a relatively clean coastal area, two coal mining areas, and a highly urbanized area in Delhi were used for the study. Distributions of PM in the 0.43-10-μm size range were measured using eight-stage cascade impactors. Regression analysis was used to estimate the percentage of PM_2.5 in PM₁₀ across distinct environments for source identification. Relatively low percentage of PM_2.5 concentrations (21, 28, and 32%) in PM₁₀ were found in clean coastal and two mining areas, respectively. Percentage of PM_2.5 concentrations in PM₁₀ in the highly urbanized area of Delhi was 51%, indicating a presence of a much higher percentage of fine particles due to vehicular combustion in Delhi. The findings of this work are important in estimating concentrations of much harmful fine particles from coarse particles across distinct environments. The results are also useful in source identification of particulates as differences in the percentage of PM_2.5 concentrations in PM₁₀ can be attributed to characteristics of sources in the diverse ambient environments.