Hourly Variations and Potential Sources of Airborne Trace Elements in PM10 in Four Representative Regions of Southeastern China

Aerosol pollution episodes have frequently occurred in China in recent years, and the airborne trace elements in particulate matter have been a cause for concern worldwide because of their impacts on human health. However, there is limited information on the hourly variations of airborne trace elements. This paper describes a detailed investigation conducted in March 2013 on the hourly variations and potential sources of airborne trace elements. Trace elements in particles with aerodynamic diameters less than 10 mu m (PM10) were monitored on-line in four representative regions with similar latitudes in southeastern China. Our results showed that the number of species of elements in PM10 detected at urban sites and an industrial park was greater than that at a rural site, due to the influences of human activities. The hourly variation patterns of trace elements indicated that their concentrations were stable during the day at the rural site, whereas a visible double peak of Pb and Cu was observed in the tourist city and a single morning peak of Pb and As was seen in the industrial city. These variations indicated the abundant traffic in the tourist city, and strong industrial emissions in the industrial city. However, the single morning peak and the slight double peak patterns of the trace elements were both found at the industrial park, indicating a combined source of industry and traffic. The results from the source identification also indicated that the sources of airborne elements were mainly industrial emissions at industrial sites, whereas the elements in the tourist city might primarily result from traffic. The correlations between PM10 concentrations and trace element concentrations were also studied. The results revealed that PM10 correlated better with elements originating from natural sources (e.g., K, Ca, Fe) than with those from anthropogenic sources (e.g., Pb, Zn, Cu). Our results provide a scientific basis for pollution control strategies at these sites.