Objective To assess the relationship between meteorological factors and selected air quality indicators including concentrations of particulate matters with particle size below 10 microns (PM10), sulfur dioxide (SO2), and nitrogen dioxide (NO2) in Wuhan during 2009-2012 by partial least squares regression (PLSR).
Methods Data on daily concentrations of PM10, SO2, and NO2 in Wuhan during 2009-2012 were provided by Hubei Environment Monitoring Central Station. During the same time period, the meteorological factors including 24-hour accumulated precipitation, mean pressure, mean wind speed, mean temperature, average relative humidity, and average daily hours of sunshine were synchronously obtained from China Meteorological Data Sharing Service System. Linear equations were established using the selected meteorological factors and air pollutants based on PLSR to extract variable variations, and a cross-validation approach was then applied to determine the number of principal components.
Results The air quality in Wuhan was gradually improved from 2009 to 2012. A combined PM10 and NO2 pollution pattern was observed. The results of PLSR analysis indicated that the scores of the first principal component to PM10, SO2, and NO2 were 0.722, 0.915, and 0.702, respectively. The increases of 24-hour accumulated precipitation, mean wind speed, mean temperature, average relative humidity, and average daily hours of sunshine were along with decreasing ambient concentrations of PM10, SO2,and NO2. Contrarily, the mean pressure showed an opposite effect on the above ambient concentrations. However, the contributions of meteorological factors to the atmospheric concentrations of PM10, SO2, and NO2 varied. The mean wind speed and the mean temperature were the leading meteorological factors affecting gaseous pollutants. The dilution effect of rainwater on atmospheric NO2 concentrations was stronger than that on PM10 concentrations.
Conclusion PLSR is able to overcome the multicollinearity of meteorological factors. The effects of meteorological factors in Wuhan, including 24-hour accumulated precipitation, mean pressure, mean wind speed, mean temperature, average relative humidity, and average daily hours of sunshine, are varied on atmospheric concentrations of PM10, SO2, and NO2.
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