[Source Apportionment of Soil Heavy Metals in Moqi Area on the Northwest Edge of Songnen Plain Based on the PCA-PMF Model].

Black soil resources are widely distributed in Morin Dawa Daur Autonomous Banner （Moqi）, northwest margin of the Songnen Plain, which is an advanced county of grain production in China and an important agricultural producing area in the east of Hulunbuir City, Inner Mongolia. Carrying out research on distribution characteristics and source apportionment of heavy metals in soil is important for preventing and controlling ecological environmental risks and protecting black soil in the northwest margin of the Songnen Plain. A total of 161 surface soil sites were systematically collected from black soil in the Moqi area, and the contents and spatial distribution characteristics of eight heavy metals （Cu, Pb, Ni, Cd, Cr, Zn, As, and Hg） were analyzed. The characteristics of soil heavy metal pollution and its ecological risk were evaluated using the single factor pollution index and potential ecological risk index, and the sources and contribution rates were quantitatively analyzed using multivariate statistical analysis and positive definite matrix factorization （PMF） model. The results showed that： ① The overall heavy metal pollution level in the soil of the research area was light, with Pb（PI=1.38）, Zn（PI=1.32）, and Cr（PI=1.32） being the main heavy metal pollution elements. ② The degree of variation of Cd and Hg was strong （CV≥0.36）, Cd showed moderate ecological risk at 17.39% of the sampling sites, Hg showed moderate and high ecological risk at 36.65% and 3.11% of the sampling sites, and the potential ecological risk of the other heavy metals was slight. ③ The spatial distribution of Cu, Ni, and Cr was similar, and there was a highly significant positive correlation among them, mainly derived from agricultural activities； Pb was significantly positively correlated with As, mainly influenced by transportation and agricultural activities； Cd and Zn had similar spatial distribution and were highly influenced by agricultural activities； and Hg mainly came from soil parent material. This research can provide scientific basis for the protection of black soil and the prevention and control of agricultural heavy metal pollution risks in the Moqi area on the northwest edge of the Songnen Plain.