Uncertainty Estimation in PM10 Mass Measurements

Abstract

Mass measurements of particles in the atmosphere are important for regulatory and scientific purposes. In nearly all of the countries, particulates ≤ 10 µm in aerodynamic size (PM10) are one of the most significant parameters of National Ambient Air Quality Standards (NAAQS). In India, as given in NAAQS, the PM10 regulatory limit is 60 µg m−3 which is based on the annual mean weight of samples (minimum 104) annually at a specific site taken for two/three days in a week for 24 h. In this paper, the components of uncertainty involved in the filter-based sampling of PM10 along with the gravimetric determination of mass have been calculated. As per the EPA guidelines, PM10 mass was monitored for a year at NPL (National Physical Laboratory), New Delhi from January 2014 to January 2015. The 24-h time-weighted mean mass concentration (n = 104) for one-year measurement varied from 32.5 to 480.2 µg m−3.During the study, high mass loading was observed in the month of December to February. In general, the flow rate of the sampling has been reported to be major uncertainty component in size-segregated PM sampling. In this work, the flow rate of the sampling (90.4%) and charge effect of the filter (6.7%) had the major contribution in the total uncertainty budget of PM10 mass measurement. Rest of the uncertainty components, e.g., balances (0.39%) and conditioning of filter (2.39%), had the least contribution.