How New Chemistry Findings Affect Our Understanding of the Weekend Effect: A Modeling Study

摘要

High ozone mixing ratios are a serious concern of public health. While ozone concentrations are high on weekdays due to anthropogenic emissions, they are often higher on weekends despite lower emissions. This phenomenon has been named the weekend effect. This study uses the UCI-CIT air quality model to assess the weekend effect in the South Coast Air Basin (SoCAB) of California. The weekend effect is reproduced by the model using an emissions inventory that includes representative weekday and weekend emissions. There are four main objectives in this study. First, to examine the influence of renoxification process on the weekend effect. Second, to quantify the impact of heterogeneous/multiphase chlorine reactions on the weekend effect. Third, to analyze the contribution of distributed generation (DG) to the weekend effect in the year 2010. Finally, to study the consequences of reducing NOx emissions on ozone concentration aloft and the subsequent impact on the weekend effect. The Caltech Atmospheric Chemistry Mechanism (CACM), used in the UCI-CIT model, is modified to accommodate these scenarios by introducing new heterogeneous reactions involving nitrogen oxides and chlorine. The emissions inventory from the 2003 Air Quality Management Plan is used to simulate a one-week episode in 2010.