Hourly variations of water-soluble ions under different sand and dust weather processes in Lanzhou, China

In this paper we aimed to collect water-soluble anion and cationic through rapid capturing system of atmospheric fine particles in order to analyze the source of water-soluble ions of atmospheric PM_2.5 in Lanzhou city, and the characteristics of hourly concentration changes in different sand and dust weather processes. The author also applied Hysplit4.8 to conduct backward trajectory analysis. The results showed that the correlation between water-soluble ions is instrumental to infer the forms of water-soluble ions in Lanzhou, such as (NH₄) ₂ SO₄, NH₄NO₃, CaSO₄, and NH₄Cl. Lanzhou has been severely polluted by sand and dust apart from the increasing amount of Ca²⁺ under different dust sources and transmission paths. Na⁺ was also elevated in March, resulted from the dust going through the Hexi Corridor from the Taklimakan. Furthermore, in April Cl⁻ also increased due to the dust being derived from Outer Mongolia then passing Qaidam Basin. In addition, Na⁺ dramatically went up in the process of precipitation.