Formation of condensable organic vapors from anthropogenic and biogenic volatile organic compounds (VOCs) is strongly perturbed by NO&amp;lt;sub&amp;gt;&amp;lt;i&amp;gt;x&amp;lt;/i&amp;gt;&amp;lt;/sub&amp;gt; in eastern China

Yuliang Liu,Mikael Ehn,Jiaping Wang,Neil M Donahue,Chao Yan,Liangduo Chen,Yuanyuan Li,Chong Liu,Yanjun Zhang,Tianyi Wang,Xuguang Chi,Lei Wang,Ximeng Qi,Dafeng Ge,Peng Sun,Zheng Xu,Dandan Huang,Zhe Wang,Aijun Ding,Wei Nie,Zhifei Xu ,Jing Yuan ,Douglas R Worsnop

doi:10.5194/acp-21-14789-2021

Abstract

Abstract. Oxygenated organic molecules (OOMs) are the crucial intermediates linking volatile organic compounds (VOCs) to secondary organic aerosols (SOAs) in the atmosphere, but comprehensive understanding of the characteristics of OOMs and their formation from VOCs is still missing. Ambient observations of OOMs using recently developed mass spectrometry techniques are still limited, especially in polluted urban atmospheres where VOCs and oxidants are extremely variable and complex. Here, we investigate OOMs, measured by a nitrate-ion-based chemical ionization mass spectrometer at Nanjing in eastern China, through performing positive matrix factorization on binned mass spectra (binPMF). The binPMF analysis reveals three factors about anthropogenic VOC (AVOC) daytime chemistry, three isoprene-related factors, three factors about biogenic VOC (BVOC) nighttime chemistry, and three factors about nitrated phenols. All factors are influenced by NOx in different ways and to different extents. Over 1000 non-nitro molecules have been identified and then reconstructed from the selected solution of binPMF, and about 72 % of the total signals are contributed by nitrogen-containing OOMs, mostly regarded as organic nitrates formed through peroxy radicals terminated by nitric oxide or nitrate-radical-initiated oxidations. Moreover, multi-nitrates account for about 24 % of the total signals, indicating the significant presence of multiple generations, especially for isoprene (e.g., C5H10O8N2 and C5H9O10N3). Additionally, the distribution of OOM concentration on the carbon number confirms their precursors are driven by AVOCs mixed with enhanced BVOCs during summer. Our results highlight the decisive role of NOx in OOM formation in densely populated areas, and we encourage more studies on the dramatic interactions between anthropogenic and biogenic emissions.

Highlights

Secondary organic aerosols (SOAs), as an important and complex component of submicron particles (Zhang et al, 2007; Jimenez et al, 2009; Huang et al, 2014), are fully involved in affecting climate (IPCC, 2013) and causing health risks (Nel, 2005; Lim et al, 2012)
Among OOMs, highly oxygenated organic molecules (HOMs), first observed in the gas phase at a boreal forest site (Ehn et al, 2010, 2012) and reviewed by Bianchi et al (2019), are so functionalized and have such low volatility that they can participate at the beginning of new particle formation (NPF) by stabilizing sulfuric acid (Kulmala et al, 2013; Riccobono et al, 2014) or through clustering alone (Kirkby et al, 2016; Bianchi et al, 2016), and they condense on existing particles and are responsible for a large fraction of SOAs (Ehn et al, 2014)
The complex mixtures of anthropogenic and biogenic Volatile organic compounds (VOCs) can be oxidized through a variety of pathways to produce OOMs, of which some low-volatility components will condense into particles, forming organic aerosols

Summary

Introduction

Secondary organic aerosols (SOAs), as an important and complex component of submicron particles (Zhang et al, 2007; Jimenez et al, 2009; Huang et al, 2014), are fully involved in affecting climate (IPCC, 2013) and causing health risks (Nel, 2005; Lim et al, 2012). Volatile organic compounds (VOCs) are ubiquitous in the atmosphere and are recognized as the main precursors of SOAs (Hallquist et al, 2009; Ziemann and Atkinson, 2012). Benefiting from state-of-the-art measurement technics (Bertram et al, 2011; Jokinen et al, 2012; Lee et al, 2014), many previously unreported oxygenated organic molecules (OOMs), as intermediates from VOCs to SOAs (Ziemann and Atkinson, 2012), have been discovered. The production of OOMs, especially HOMs, from precursors such as monoterpenes (Ehn et al, 2014; Jokinen et al, 2015; Kirkby et al, 2016; Berndt et al, 2016), sesquiterpenes (Richters et al, 2016), isoprene (Jokinen et al, 2015; Zhao et al, 2021), aromatics (Wang et al, 2017; Molteni et al, 2018; Garmash et al, 2020), and alkanes (Wang et al, 2021) has been investigated in laboratories by using chemical ionization atmospheric pressure interface time-of-flight mass spectrometers with nitrate reagent ions (nitrate CI-APi-TOFs)

Methods

Results

Conclusion