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Evaluation and Application of an Online Coupled Modeling System to Assess the Interaction between Urban Vegetation and Air Quality

Category: Urban Air Quality

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DOI: 10.4209/aaqr.2017.06.0199
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Jianbo Yang1,2, Hongnian Liu 1,3, Jianning Sun1,3

  • 1 School of Atmospheric Sciences and Institute for Climate and Global Change, Nanjing University, Nanjing 210023, China
  • 2 Tianjin Institute of Meteorological Science, Tianjin 300074, China
  • 3 Joint International Research Laboratory of Atmospheric and Earth System Sciences, Ministry of Education, Nanjing 210023, China

Highlights

Evaluate the ability of two parameterization schemes for dry deposition velocities.
Analyze the dry deposition processes over different vegetation species.
Quantify the potential air quality impacts under different urban greening scenarios.
Consider the role of urban vegetation on local air quality through 2 different ways.


Abstract

Urban vegetation has always been an integral part of the urban circumstances. It could affect ambient air quality through both direct and indirect ways: by enhancing dry deposition process of air pollutants and by contributing to the formation of ozone due to the emission of biogenic volatile organic compounds (BVOC). In this study, hourly measurements of gaseous dry deposition velocities are used to evaluate the performance of two dry deposition modules. Based on verification against measurements, an online coupled modeling system (RBLM-Chem) is introduced to investigate the dry deposition process of air pollutants (both gas and particles), the diurnal and seasonal variation patterns, the discrepancy between different vegetation species, and assessing the role of urban vegetation in affecting local air quality under different greening scenarios. Results indicated that trees are generally more efficient in removing air pollutants than shorter vegetation (e.g., grass). Moreover, conifers exhibit higher dry deposition velocities than broadleaf trees in terms of annual average. The introduction of vegetation (either trees or grass) clearly raises the dry deposition velocity of air pollutants. The air pollutant that is most removed by urban vegetation in Suzhou is PM10 and its annual removal rate amount to 1484.5 t a–1. Current urban greening scenario within Suzhou contributes to a reduction in daily mean concentration of 8.1% (SO2), 7.1% (NO2), 5.6% (O3), 4.7% (PM10) and 4.4% (PM2.5), respectively, in summer, and in winter, the reduction is 4.6%, 5.5%, 4.5%, 3.6% and 3.7%, respectively. The improvement of pollutant concentration would be strengthened with increasing vegetation coverage. Besides, peri-urban forest ecosystem would also play a role on air quality improvement within urban area. As for BVOC-emission-effect, the BVOC emission from the urban trees under 40% coverage could result in a consumption of NOx (–3.2%) and a formation of O3 (2.3%).

Keywords

Urban vegetation Dry deposition Air pollutant Urban air quality Greening scenarios


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