In order to study the status and sources of heavy metal pollution in Yinchuan Yellow River floodplain soils, we used inductively coupled plasma mass spectrometry (ICP-MS) to determine the presence of eight heavy metals in 92 soil samples from the Yinchuan Yellow River floodplain and used enrichment factors, geological accumulation index, and potential ecological risk index to analyze and evaluate the characteristics of heavy metal pollution in the study area. Combined correlation analysis, absolute factor analysis-multiple linear regression model (APCS-MLR), positive matrix factorization (PMF), and geostatistics were used to analyze the sources of soil heavy metals. The results showed that the content of eight heavy metals in the surface soil of the Yellow River floodplain in Yinchuan City were lower than the screening value of soil pollution risk in agricultural land; Cu and Pb contents were lower than the background value of Yinchuan City soil, and the contents of the remaining six elements were higher than the background value. The coefficients of variation of Zn and Cd were large and in the medium variation level and were influenced by anthropogenic activities. The heavy metal content varied between different land types and generally showed that wasteland > abandoned farmland > woodland > cultivated land. The average content of Cu and Pb in forest and arable soils was lower than the regional background value, whereas the rest of the heavy metals in different land types were higher than the soil background value. The analysis of enrichment factors showed that Zn and Cd were slightly enriched in the study area, and the cumulative index method and the evaluation of the potential risk of single heavy metals indicated that more than 60% of the sites in the study area were contaminated with Cd at a medium or higher potential ecological hazard. The comprehensive evaluation results of potential ecological risk showed that the overall ecological risk level of the study area was mild. From the distribution of heavy metal ecological risk comprehensive index sample points, only one point was in moderate ecological hazard, and the pollution point showed very few. Comprehensive correlation analysis, APCS-MLR model, PMF model, and geostatistical analysis results confirmed that Zn and Cd in the study area were mainly derived from human activities such as agricultural activities and transportation, and the remaining heavy metals were derived from soil parent materials. The results of this study can provide a scientific basis for the ecological protection and sustainable development of the Yellow River in Yinchuan City.
Keywords: Yellow River floodplain; absolute factor analysis-multiple linear regression （APCS-MLR）; heavy metals; pollution evaluation; positive matrix factorization （PMF）; source apportionment.