The effect of rain on suspended particulate matter and other pollutants in an urban area

摘要

A study on the effect of rain on atmospheric pollutants in the city of Rome from 1994 to 1996 has been conducted based on data collected by governmental monitoring stations located in different areas of the city.rnIn the city of Rome, the average annual precipitation value is over 700 mm, referring to measurements collected from over a century. Almost every month exhibits at least one rainy day.rnDays have been divided into two categories: rainy days, if it has rained at least 2 mm in the day, and days with no rain, in the other cases. Particulate matter concentration has been averaged every month in both categories. The difference between the two monthly values has been divided by the days-with-no-rain average to calculate the monthly abatement.rnAbatement in the three years is around 10%, although there exist single events of heavily rainy days that reveal an up to 50 % decrease in hourly concentration. Concentrations of particulate matter, CO and NO_x have been correlated with precipitation, using working days and low wind speed conditions. Results have been compared with both the day preceding and succeeding the actual rainy day.