Characteristics of environmentally persistent free radicals in PM2.5: Concentrations, species and sources in Xi'an, Northwestern China

Qingcai Chen; Haoyao Sun; Zhen Mu; Yuqin Wang; Yanguang Li; Lixin Zhang; Mamin Wang; Zimeng Zhang

doi:10.1016/j.envpol.2019.01.015

Characteristics of environmentally persistent free radicals in PM_2.5: Concentrations, species and sources in Xi'an, Northwestern China

Environ Pollut. 2019 Apr:247:18-26. doi: 10.1016/j.envpol.2019.01.015. Epub 2019 Jan 7.

Authors

Qingcai Chen¹, Haoyao Sun², Zhen Mu², Yuqin Wang², Yanguang Li³, Lixin Zhang², Mamin Wang², Zimeng Zhang²

Affiliations

¹ School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China. Electronic address: chenqingcai@sust.edu.cn.
² School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China.
³ Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits, MLR, Xi'an, 710054, China; Xi'an Center of Geological Survey, China Geological Survey, Xi'an, 710054, China.

PMID: 30650344
DOI: 10.1016/j.envpol.2019.01.015

Abstract

Environmentally persistent free radicals (EPFRs) are a new class of environmental risk substances that can stably exist in atmospheric particles and pose a potential threat to human health. In this study, electron paramagnetic resonance (EPR) spectroscopy was used to study the concentration levels, species characteristics, and sources of EPFRs in PM_2.5 in Xi'an in 2017. The results showed that the concentrations of EPFRs in PM_2.5 in Xi'an in 2017 ranged from 9.8 × 10¹¹ to 6.9 × 10¹⁴ spins/m³. The highest concentration of EPFRs occurred in winter when the average concentration was 2.1 × 10¹⁴ spins/m³. The lowest concentration of EPFRs occurred in autumn when the average concentration was 7.0 × 10¹³ spins/m³. According to the annual average atmospheric concentration of EPFRs, the amount of EPFRs inhaled by people in Xi'an is equivalent to approximately 5 cigarettes per person per day and approximately 23 cigarettes per person per day in winter when haze occurs. The results of the study on the EPFR characteristics show that the EPFRs in PM_2.5 in Xi'an are mainly C-center organic radicals that are primarily non-decaying types, accounting for approximately 75% and 85% of total concentration of EPFRs in autumn and winter, respectively. Finally, a correlation analysis was used to explore the origins of EPFRs in PM_2.5. Significant positive correlations were found between EPFRs and SO₂, NO₂ and the thermally derived OC3 and OC4 carbonaceous components. The results suggested that coal-fired and traffic may be important sources of EPFRs in PM_2.5 in Xi'an. In addition, EPFRs are significantly positively correlated with O₃ in summer, suggesting that some EPFRs may also originate from secondary processes. This study provides important basic data and evidence for further assessments of the potential health risks of EPFRs in PM_2.5 and the development of effective air pollution control measures.

Keywords: Air pollution; Concentration levels; Decay; EPFRs; Environmentally persistent free radicals; Sources.

MeSH terms

Air Pollutants / analysis*
China
Coal / analysis
Environmental Monitoring*
Free Radicals / analysis*
Humans
Particulate Matter / analysis*
Seasons

Substances

Air Pollutants
Coal
Free Radicals
Particulate Matter