Aerosols chemical composition, light extinction, and source apportionment near a desert margin city, Yulin, China.

Daily PMand PM sampling was conducted during four seasons from December 2013 to October 2014 at three monitoring sites over Yulin, a desert margin city. PM and PM levels, water soluble ions, organic carbon (OC), and elemental carbon (EC) were also analyzed to characterize their chemical profiles. (light extinction coefficient) was calculated, which showed the highest in winter with an average of 232.95 ± 154.88 Mm, followed by autumn, summer, spring. Light extinction source apportionment results investigated (NH)SO and NHNO played key roles in the light extinction under high RH conditions during summer and winter. Sulfate, nitrate and Ca dominated in PM/PM ions. Ion balance results illustrated that PM samples were alkaline, and PM samples were more alkaline than PM. High SO /K and Cl/K ratio indicated the important contribution of coal combustion, which was consistent with the OC/EC regression equation intercepts results. Principal component analysis (PCA) analyses results showed that the fugitive dust was the most major source of PM, followed by coal combustion & gasoline vehicle emissions, secondary formation and diesel vehicle emissions. Potential contribution source function (PSCF) results suggested that local emissions, as well as certain regional transport from northwesterly and southerly areas contributed to PM loadings during the whole year. Local government should take some measures to reduce the PM levels.