Surface O3 photochemistry over the South China Sea: Application of a near-explicit chemical mechanism box model

Environ Pollut. 2018 Mar:234:155-166. doi: 10.1016/j.envpol.2017.11.001. Epub 2017 Nov 22.

Abstract

A systematic field measurement was conducted at an island site (Wanshan Island, WSI) over the South China Sea (SCS) in autumn 2013. It was observed that mixing ratios of O3 and its precursors (such as volatile organic compounds (VOCs), nitrogen oxides (NOx = NO + NO2) and carbon monoxide (CO)) showed significant differences on non-episode days and episode days. Additional knowledge was gained when a photochemical box model incorporating the Master Chemical Mechanism (PBM-MCM) was applied to further investigate the differences/similarities of O3 photochemistry between non-episode and episode days, in terms of O3-precursor relationship, atmospheric photochemical reactivity and O3 production. The simulation results revealed that, from non-O3 episode days to episode days, 1) O3 production changed from both VOC and NOx-limited (transition regime) to VOC-limited; 2) OH radicals increased and photochemical reaction cycling processes accelerated; and 3) both O3 production and destruction rates increased significantly, resulting in an elevated net O3 production over the SCS. The findings indicate the complexity of O3 pollution over the SCS.

Keywords: Ozone; Photochemical box model; Photochemistry; South China Sea; VOCs.

MeSH terms

  • Air Pollutants / analysis
  • Air Pollutants / chemistry*
  • Carbon Monoxide / analysis
  • China
  • Environmental Monitoring
  • Islands
  • Models, Theoretical*
  • Nitrogen Oxides / analysis
  • Oceans and Seas
  • Ozone / analysis
  • Ozone / chemistry*
  • Photochemical Processes
  • Photochemistry
  • Volatile Organic Compounds / analysis

Substances

  • Air Pollutants
  • Nitrogen Oxides
  • Volatile Organic Compounds
  • Ozone
  • Carbon Monoxide