Mineralogical and geochemical composition of particulate matter (PM10) in coal and non-coal industrial cities of Henan Province, North China

A total of 19 24-h PM10 samples, the 11 for a typical coal industrial city and 8 for a non-coal industrial city, were collected by a TSP-PM10 sampler during a serious and continuous haze event in Henan Province, North China. An X-ray diffractometer (XRD) was used to determine the mineralogy and a scanning electron microscope equipped with an energy-dispersive X-ray spectrometer (SEM-EDS) was used to determine the morphology and chemical composition of the PM10 samples. The crystalline phases that were identified by XRD mainly include sulfate (dominated by koktaite, boussingaultite, gypsum, etc.) and silicate (quartz and kaolinite) as well as small amount of chloride (sal-ammoniac). Silicate particles mainly originate from crust as well as waste dumps for coal industrial cities, and usually have an irregular shape, while sulfate particles occur as individual sheets or needles, and have an anthropogenic origin, which are the products of chemical reaction of preexisting carbonate with SO2 emitted by coal combustion. Nitrogen, S and Cl occurring in particulate matter are considered to have an anthropogenic origin due to their high enrichment factors, and their abundance in particulate matter is associated with coal industrial activities. Nitrogen mainly occurs as NH4+ in sulfate, as well as in small amount of organic matter. Sulfur mainly occurs as SO42 − in sulfate. Chlorine mainly occurs in chloride.