Fast screening compositions of PM2.5 by ATR-FTIR: Comparison with results from IC andOC/EC analyzers

J Environ Sci (China). 2018 Sep:71:76-88. doi: 10.1016/j.jes.2017.11.021. Epub 2017 Dec 11.

Abstract

Chemical speciation of fine particles or PM2.5 collected on filters is still a costly and time-consuming task. In this study, filter-based PM2.5 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-1 for nitrate, 1435, 3045 and 3215cm-1 for ammonium, 615cm-1 for sulfate, 690, 760 and 890cm-1 for POC and 1640 and 1660cm-1 for SOC respectively, during polluted days (PM2.5>75μg/m3) than during clean days (PM2.5≤75μg/m3). With the evolution of a haze episode during our field campaign, the concentrations of the major PM2.5 components displayed consistent variations with their infrared absorption peak heights, suggesting ATR-FTIR could be a fast and useful technique to characterize filter-based PM2.5 compositions particularly during pollution events although cautions should be taken when PM2.5 levels are low. Notably, elevated PM2.5 mass concentrations occurred with enhanced ratios of [NO3-]/[SO42-] and [NH4+]/[SO42-], implying that nitrogenous components play vital roles in the PM2.5 pollution events in the study region.

Keywords: ATR-FTIR; Ammonium; Fine particles (PM(2.5)); Haze episode; Nitrate; Organic carbon; Sulfate.

MeSH terms

  • Air Pollutants / analysis*
  • Air Pollutants / chemistry
  • Carbon / analysis
  • China
  • Environmental Monitoring*
  • Nitrates / analysis
  • Particulate Matter / analysis*
  • Particulate Matter / chemistry
  • Spectroscopy, Fourier Transform Infrared*
  • Sulfates / analysis

Substances

  • Air Pollutants
  • Nitrates
  • Particulate Matter
  • Sulfates
  • Carbon