Preprints
https://doi.org/10.5194/acp-2021-132
https://doi.org/10.5194/acp-2021-132

  23 Mar 2021

23 Mar 2021

Review status: this preprint is currently under review for the journal ACP.

On the competing effects of contemporary land management vs. land cover changes on global air quality

Anthony Y. H. Wong and Jeffrey A. Geddes Anthony Y. H. Wong and Jeffrey A. Geddes
  • Department of Earth and Environment, Boston University, Boston, MA, USA

Abstract. Our work explores the impact of two important dimensions of land system changes, land use and land cover change (LULCC) and direct agricultural reactive nitrogen (Nr) emissions from soils, on ozone (O3) and fine particulate matter (PM2.5) air quality over contemporary (1992 to 2014) time scales. We account for LULCC and agricultural Nr emissions changes with consistent remote sensing products and new global emission inventories, respectively, estimating their impacts on global surface O3 and PM2.5 concentrations and Nr deposition using the GEOS-Chem global chemical transport model. Over this time period, our model results show that agricultural Nr emission changes cause reduction of annual mean PM2.5 level over Europe and northern Asia (up to −2.1 μg m−3), while increasing PM2.5 level India, China and eastern US (up to +3.5 μg m−3). Land cover changes induce small reductions in PM2.5 (up to −0.7 μg m−3) over Amazonia, China and India due to reduced biogenic volatile organic compounds (BVOC) emissions and enhanced deposition of aerosol precursor gases (e.g. NO2, SO2). Agricultural Nr emission changes only lead to minor changes (up to ±0.6 ppbv) in annual mean surface O3 level, mainly over China, India and Myanmar. Meanwhile, our model result suggests a stronger impact of LULCC on surface O3 over the time period Across South America, the combination of changes in dry deposition and isoprene emissions results in −0.8 to +1.2 ppbv surface ozone changes. The enhancement of dry deposition reduces surface ozone level (up to −1 ppbv) over southern China, eastern US and central Africa. The enhancement of soil NOx emission due to crop expansion also contribute to surface ozone changes (up to +0.6 ppbv) over sub-Saharan Africa. In certain regions, the combined effects of LULCC and agricultural Nr emission changes on O3 and PM2.5 air quality can be comparable (> 20 %) to that of anthropogenic emission changes over the same time period. Finally, we calculate that the increase in global agricultural Nr emissions leads to a net increase in global land area (+3.67 × 106 km2) that potentially faces exceedance in critical Nr load (> 5 kgN ha−1 yr−1). Our result demonstrates the possible impacts of contemporary LULCC and agricultural Nr emission changes on PM2.5 and O3 air quality, which also implies the potential importance of land system changes on air quality over multi-decadal timescales.

Anthony Y. H. Wong and Jeffrey A. Geddes

Status: open (until 18 May 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-132', Anonymous Referee #1, 24 Mar 2021 reply
    • AC1: 'Reply on RC1', Anthony Y. H. Wong, 08 Apr 2021 reply

Anthony Y. H. Wong and Jeffrey A. Geddes

Anthony Y. H. Wong and Jeffrey A. Geddes

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Short summary
Land cover change and land management are considered to have important and distinct impacts on air quality. Here we use remote sensing products and agricultural emission inventories to characterize contemporary global land cover and land management changes for chemical transport model simulations. We find that contemporary land system change has significant impact on global air quality, with land management dominating the effects on PM, and land cover change dominating the impacts on ozone.
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