Using a 3-D Air Quality Model to Simulate Ground-Level Ozone Production with Measured Speciated VOC in Sao Paulo, Brazil

摘要

One of the greatest challenges in modeling urban ozone is the development of representative and accurate input for air quality modeling. Special care must be taken when referring to the pollution inventory. In addition to the amount, spatial and temporal distribution of emitted pollutants, the knowledge of their chemical composition is of vital importance in order to portray atmospheric chemical transformations resulting in the production of secondary pollutants. It is therefore important to know the emitter profile and assign an appropriate chemical composition to the various pollutant flows to warrant a reliable description of the real environment assessed. Following this philosophy a joint study carried out by PETROBRAS R&D Center (CENPES) and Sao Paulo University Atmospheric Sciences Department (USP-IAG) was established aiming to assess the formation of ground-level tropospheric ozone. The 3-D Eulerian photochemical CIT model was used for the Metropolitan Area of Sao Paulo (MASP), together with local measurements for the ambient VOCs, thus upgrading previous studies of the same area of interest that resorted to published data. The present study aims to simulate MASP air pollution dynamics using measured concentrations of speciated VOCs in the local atmosphere covering the period from 30 March to 02 April 2004, when atmospheric VOC characterization campaigns were carried out by CENPES and its partners (DGA, USA). The total amounts of CO, NO_x, SO2 and VOCs were obtained from the official emissions inventory. Spatial distribution was proportional to the number of registered vehicles in each county, being the temporal emissions adjusted according to CO and NO_x profiles per day. Either observations or numerical modeling with the CSU Regional Atmospheric Modeling System (RAMS) were used to build the meteorological fields. Ambient concentrations of the criteria pollutants (NO2, CO, SO2 and ozone) were forecast and compared to the official air quality records (CETESB).