The article explores how sulfur dioxide turns into sulfate and nitrogen dioxide into nitrate in urban areas. The researchers studied the daily changes in sulfate, nitrate, and other pollutants to understand this process. They found that these pollutants increase during the day and decrease at night, indicating that the oxidation of sulfur dioxide and nitrogen dioxide is influenced by sunlight. This study helps us understand how pollutants in the air are transformed into harmful substances, which can have implications for air quality and human health in urban environments.