Fast screening compositions of PM by ATR-FTIR: Comparison with results from IC andOC/EC analyzers.

Chemical speciation of fine particles or PM collected on filters is still a costly and time-consuming task. In this study, filter-based PM samples were collected during November-December 2013 at four sites in Guangzhou, and the major components were fast screened (~7min per filter sample) by Attenuated Total Reflectance (ATR)-Fourier Transform Infrared Spectroscopic (FTIR) in comparison with that measured by Organic carbon/Element carbon (OC/EC) analyzer and Ion Chromatography (IC). The concentrations of nitrate, ammonium, sulfate, primary organic carbon (POC) and secondary organic carbon (SOC) measured by OC/EC and IC analyzers were better correlated with their infrared absorption peak heights at 1320cm for nitrate, 1435, 3045 and 3215cm for ammonium, 615cm for sulfate, 690, 760 and 890cm for POC and 1640 and 1660cm for SOC respectively, during polluted days (PM>75μg/m) than during clean days (PM≤75μg/m). With the evolution of a haze episode during our field campaign, the concentrations of the major PM components displayed consistent variations with their infrared absorption peak heights, suggesting ATR-FTIR could be a fast and useful technique to characterize filter-based PM compositions particularly during pollution events although cautions should be taken when PM levels are low. Notably, elevated PM mass concentrations occurred with enhanced ratios of [NO]/[SO] and [NH]/[SO], implying that nitrogenous components play vital roles in the PM pollution events in the study region.