[Spatial Distribution Characteristics and Source Analysis of Heavy Metals in Urban River Surface Sediments from the Lanzhou Reach of the Yellow River].

), together with the sediment pollution index (SPI), were used to assess heavy metal pollution characteristics and ecological risk levels in the urban river surface sediments of the Lanzhou reach of the Yellow River. Pearson's correlation analysis (CA), positive matrix factorization (PMF), and principal component analysis/absolute principal component score (PCA/APCS) were jointly employed to quantitatively analyze pollution sources of heavy metals. The results showed that the mean concentrations of the majority of heavy metals exceeded their corresponding background values of Gansu Province and Lanzhou City with the exception of As, and the spatial distribution of high concentrations of heavy metals was mainly concentrated in the corner of the river. Based on the single factor pollution and geo-accumulation indexes of the eight heavy metals, in the Lanzhou reach of the Yellow River, Cr was the dominant pollution element in the urban river surface sediments, followed by Cd and Ni. Additionally, the SPI values for the eight heavy metals in the surface sediments ranged from 0.48 to 8.56, presenting natural to low ecological risk level. Furthermore, source apportionment revealed that a mixture source of industrial and agricultural activities (77.6%) was the largest contributor of Cr, Ni, Zn, As, Cd, and Pb in the urban river surface sediments, followed by natural sources (11.4%) and a mixed source of industrial and traffic activities (11%).