Influences of Natural Fugitive Dusts Emitted form Sandlands along a River Valley on Ambient Particulate Air Quality

摘要

This study aimed to characterize the physicochemical properties of atmospheric particles sampled along the Kaoping riverside in southern Taiwan. Regular sampling conducted to collect particulate matter less than 10 microns diameter (PM_(10)) with high-volume samplers at four sampling sites (KA , KB , PC and PD) on May 28～31, July 9～12, October 8～11, and December 4～7, 2012.Intensive sampling was also conducted by the same samplers on June 29～30, 2012. After sampling, metallic contents of PM_(10) were analyzed with an inductively coupled plasma-atomic emission spectrometer (ICP-AES). Ionic species and carbonaceous contents of PM_(10) were then analyzed with an ion chromatograph (IC) and an elemental analyzer (EA), respectively. Field sampling of PM_(10) indicated that natural fugitive dust event (NFDE) would increase local PM_(10) concentrations up 21.7-27.2 times of the background level, which could deteriorate ambient particulate air quality along the Kaoping River Valley. Chemical analysis results showed that the abundant chemical components of PM_(10) were sulfate (SO_4~(2-)), nitrate (NO_3~-), ammonium (NH_4~+) and organic carbon (OC), and crustal elements [calcium (Ca), aluminum (Al), iron (Fe) and magnesium (Mg)]. The highest organic carbon and element carbon (OC/EC) ratio of PM_(10) was observed in winter, indicating that biomass burning and/or anthropogenic combustion activities in winter occurred more frequently than other seasons. The most abundant metallic elements were Ca, Mg, Fe, and Al, showing an increase of crustal elements ranged from 3.0 to 8.3% during the NFDE. Finally, the source identification and apportionment of PM_(10) were analyzed by principal component analysis (PCA) and chemical mass balance (CMB) receptor model. Results from CMB receptor modeling showed that the major sources of atmospheric PM_(10) along the Kaoping River Valley were secondary nitrate, secondary sulfate, and vehicular exhausts for all seasons. Biomass burning occurred not only in winter, but also in other seasons. The natural fugitive dust event (NFDE) from the sandlands of Kaoping River Valley contributed 49.7%-57.8% of PM_(10).