[Interannual Variation of Metal Elements and Water-Soluble Ions in PM_2.5 During Wintertime in Xinxiang and Their Source Apportionment]

To study the interannual variations of chemical composition and source apportionment, a field campaign was carried out to collect the PM_2.5 temperance sample during the winter of 2015 and the winter of 2016 in Xinxiang urban areas. PM_2.5 mass concentration, metal elements, and the water-soluble ions were determined and meteorological factors were recorded simultaneously. The results showed that the daily mean concentrations of PM_2.5 indicated serious pollution with values of 226 μg·m^-3 and 224 μg·m^-3 in 2015 and 2016, respectively. The Cd and Pb elements in PM_2.5 were significantly enriched, with EF more than 1000. However, compared with 2015, the enrichment effect of most metal elements showed a trend of decrease in 2016. The water-soluble ions were mainly composed of SO₄^2-, NO₃^-, and NH₄⁺. The results showed a trade-off effect between metal elements and water-soluble ions in the two study periods. The results of PCA and PMF analyses show that there were four main emission sources in Xinxiang city in winter, namely dust, secondary source, industrial source, and fossil fuel combustion source. Moreover, the main sources of PM_2.5 was the mixed source of soil and building dust and secondary aerosol pollution, with contributions of 37.46% and 34.94% in the winters of 2015 and 2016, respectively.