Improving risk management by using the spatial interaction relationship of heavy metals and PAHs in urban soil.

Identifying combined pollution risk areas is difficult because of the complex pollutant sources and heterogeneous soil properties in urban systems. This study used bivariate local Moran's I to analyze the spatial interaction between heavy metals and PAHs, revealed the causes of spatial interaction patterns through PMF, and proposed a risk zoning approach for combined pollution in urban areas. The results showed that both heavy metals and PAHs had high spatial heterogeneity in urban soil. Bivariate LISA maps revealed the spatial interactions between heavy metals and PAHs. The historical area was the hotspot of combined pollution. The overlay of pollutant sources and sinks was responsible for the spatial interaction patterns of combined organic and inorganic pollution. Coal consumption was the main emission source for heavy metal and PAHs pollution, accounting for 31% and 21%, respectively. We used bivariate LISA as the auxiliary variable to reduce the uncertainty of identification combined pollution risk zones. More than 11% of the total area clustered significantly where concentration of both heavy metals and PAHs ware in excess of the risk threshold. This study indicates that we can provide better decision-making support for soil risk management based on the knowledge derived from spatial interaction analysis.