Photochemical Smog Modeling of Urban Airshed

1
Photochemical Smog Modeling of Urban Airshed

• by
• Mrs Zhang Baoning
• Mr. Liu Qishan

2
Introduction

• Photochemical smog is the result of reactions
  between hydrocarbons and nitrogen oxides trigged
  by the sunlight.
• Oxidants include ozone(O3), perxyacetyl nitrate
  (PAN), peroxybenzoyl nitrate (PBN), hydrogen
  peroxide (H2O2), and formic acid (HCOOH) which
  can oxidize potassium iodide.

3
Box Model

• Box model can be used to estimate pollutant
  concentration from an area source.
• The box represents the volume of air over the
  area of interest.
• Pollutants within the box are assumed to be mixed
  fast and completely so that concentrations are
  uniform within the box.

4
Area-Source Box Diffusion Model
5
Basic Equations

• Box model equation

6
Chemical Reaction Submodel

• Atmospheric photochemical reactions for
  simulation model

7
Sub-model Basic Equations
8
Survey Data Needs

• Dimension of some city, determination of
  simulating date, mixing height, wind speed and
  direction, upwind and background concentrations
  of O3 and PAN.
• Rate constants of each step, ultraviolet flux,
  initial concentrations of NO, NO2, CO, O3, PAN,
  and HC.

9
Model Verification

• Calculated O3 and PAN concentrations will be
  compared with observed values.
• The chemical reaction submodel affects model
  result directly.
• Multi-box model can be used to place single box
  model to achieve best result.