Pollution situation and possible markers of different sources in the Ordos Region, Inner Mongolia, China

In order to investigate the pollution situation for a fast-developing industrial area at its first stage, a systematic study on the gaseous and particulate pollution in the Ordos Region of Inner Mongolia was performed during 9-24 September 2005. The gases SO₂, NO_x, O₃, CO, and the particulates PM₁₀ and PM_2.5 were sampled at five sites in Ordos. Species measured in aerosol were 21 elements, 10 ions, organic carbon (OC), elemental carbon (EC), and the acid-buffering capacity of particulates. Possible markers of sources for different transport directions were firstly investigated, which was a new attempt for clarification of regional transport with different directions. None of the gases exceeded the national standards of China. PM_2.5 contributed most to PM₁₀ at the background site, indicating the greatest contribution of regional transport. Organic matter, crustal material, and sulfate ion were the three dominant species of aerosol, followed by EC, NO₃⁻, NH₄⁺, trace elements, and other ions. The acidity of PM_2.5 was higher than that of PM₁₀, and the buffering capacity in PM₁₀ was higher than that in PM_2.5. Four peaks of pollution aerosol were observed during the 3-week study sampling period, separated by periods of cleaner air. Back-trajectories revealed that the peaks came from the south and the cleaner air from the north. It is the first time to find different markers for aerosols from different transport directions in Ordos. S and Pb, as well as SO₄²⁻, NO₃⁻, and NH₄⁺ appeared to be good markers of southern aerosol in the Ordos, since all showed four clear peaks on days dominated by southern direction. Extremely high peaks of Al and Ti on the 16th and 17th, especially at the dust-monitoring site, indicated good markers for soil dust. Ca and Mg showed earlier peaks on the 16th at the western site, indicating possible markers for western aerosol.