One decade of parallel fine (PM2.5) and coarse (PM10–PM2.5) particulate matter measurements in Europe: trends and variability

摘要

The trends and variability of PM, PM and PMconcentrations at seven urban and rural background stations in five Europeancountries for the period between 1998 and 2010 were investigated. Collocatedor nearby PM measurements and meteorological observations were used in orderto construct Generalized Additive Models, which model the effect of eachmeteorological variable on PM concentrations. In agreement with previousfindings, the most important meteorological variables affecting PMconcentrations were wind speed, wind direction, boundary layer depth,precipitation, temperature and number of consecutive days with synopticweather patterns that favor high PM concentrations. Temperature has anegative relationship to PM concentrations for low temperatures anda positive relationship for high temperatures. The stationary point of thisrelationship varies between 5 and 15 °C depending on the station.PM concentrations increase for increasing temperatures almostthroughout the temperature range. Wind speed has a monotonic relationship toPM except for one station, which exhibits a stationary point.Considering PM, concentrations tend to increase or stabilize forlarge wind speeds at most stations. It was also observed that at allstations except one, higher PM concentrations occurred for east winddirection, compared to west wind direction. Meteorologically adjusted PMtime series were produced by removing most of the PM variability due tometeorology. It was found that PM and PM concentrationsdecrease at most stations. The average trends of the raw andmeteorologically adjusted data are −0.4 μg m yr forPM and PM size fractions. PM have much smallertrends and after averaging over all stations, no significant trend wasdetected at the 95% level of confidence. It is suggested that decreasingPM in addition to PM can result in a faster decrease ofPM in the future. The trends of the 90th quantile of PMand PM concentrations were examined by quantile regression in orderto detect long term changes in the occurrence of very large PMconcentrations. The meteorologically adjusted trends of the 90thquantile were significantly larger (as an absolute value) on average overall stations (−0.6 μg m yr).