RESUMO
@#Abstract: Objective To understand the pollution characteristics and sources of PM2.5 in the atmosphere during heating and non-heating periods in Urumqi City in 2021, and provide scientific basis for pollution control during different periods. Method A total of 188 air samples were collected from area A and area B of Urumqi City, and 12 metal elements and 5 water-soluble ions were quantitatively analyzed, and the pollution sources were analyzed by enrichment factor method and principal component analysis method. Results In 2021, the mass concentrations of PM2.5 in areas A and B of Urumqi were 45.0 (20.0, 158) µg/m3 and 28.0 (17.5, 66.0) µg/m3, respectively, with statistically significant difference (Z=-2.870, P<0.05). During the heating period, the concentrations were 110 (68.0, 250) µg/m3 and 61.0 (31.0, 88.0) µg/m3, respectively, with no statistically significant difference (Z=-3.822, P<0.01). During the non-heating period, the concentrations were 18.0 (13.0, 22.3) µg/m3 and 18.0 (12.8, 22.0) µg/m3, respectively, with no statistically significant difference (Z=-0.596, P>0.05). The SNA (the sum of SO42-, NO3-and NH4+) accounted for 71.7% and 23.4% of PM2.5 in A area during heating and non-heating periods, respectively, with statistically significant difference (Z=-8.057, P<0.01); the corresponding proportions in B area were 60.7% and 24.9%, with statistically significant difference (Z=-6.672, P<0.01). During the heating and non-heating periods, the ratios of NO3-/SO42-are 0.63 and 0.54 in A area were 0.63 and 0.54, respectively, with statistically significant difference (Z=-2.382, P<0.05); and the corresponding ratios in B area were 0.72 and 0.53, respectively, with statistically significant difference (Z=-3.182, P<0.05). The ratio of NO3- to SO42- was less than 1 in both heating and non-heating periods in the two areas. and the correlation between five water-soluble ions was significant (P<0.05). The correlation coefficient between NH4+ and SO42-, NO3-and Cl- in A and B areas during heating periods were all >0.9, indicating that NH4+and SO42-, NO3- and Cl- bind in (NH4)2SO4, NH4HSO4, NH4NO3, and NH4Cl. During non-heating periods, the correlation between NH4+ and each ion was slightly lower. During heating periods in area A, Sb, As, Cd, Pb, and Tl were severely enriched (EF>100). During non-heating periods in the same area, As, Cd, Pb, Tl, and Hg were severely enriched (EF>100). During heating periods in area B, Sb, As, Cd, Pb, and Hg were severely enriched (EF>100), and during non-heating periods in the same area, Sb, Cd, and Hg were severely enriched (EF>100). Coal emission, photochemical secondary pollution, motor vehicle exhaust, dust and industrial pollution were the main sources of PM2.5 pollution in the two areas, and the contribution rate of fixed sources was higher than that of mobile sources. Conclusion In 2021, the mass concentration of PM2.5, water-soluble ions and metal elements in Urumqi City were higher in area A than area B, the heating period was higher than the non-heating period, the excess rate of area A was higher than that in area B, and the contribution rate of fixed air pollution was greater than that of mobile sources.