Establishing a partition interpolation method for PAHs in site soil based on different pollution causes

PAHs are recognized as carcinogens by the International Agency for Research on Cancer. Acquiring spatial distribution information of PAHs is a prerequisite and foundation for soil pollution prevention and control on site. However, the presence of extremely high concentrations (outliers) limits the predictive accuracy of the spatial distribution of PAHs. This study focuses on fluoranthene (FLT), benzo[a]pyrene (BaP), benzo[b]fluoranthene (BbF), and indeno[1,2,3-cd]pyrene (InP), which have relatively high detection rate. Using geostatistical analysis, geodetectors, solute transport models, and multiple regression methods, we analyzed the spatial distribution characteristics and main influencing factors of these PAHs, and developed a new partition interpolation method. The research results are as follows: (1) The proportion of points exceeding the screening and risk intervention thresholds for BaP (16.10% and 4.23, respectively) was higher than that of the other three PAHs. The outlier values were primarily distributed in coking areas and wastewater treatment stations, where pollution was mainly due to leaks and affected areas within a 10-m radius, exhibiting high variability. Atmospheric deposition was the main influencing factor for zones excluding outliers, where variability was weaker; (2) We used solute transport models to simulate PAH distributions for the outlier zones and multiple linear regression models for the gentle zones without outliers. This approach reduced RMSE by over 90% compared to traditional interpolation methods, and reflected both localized highly-variable structures and overall distribution characteristics. This is of great significance for improving the accuracy of spatial distribution prediction of PAHs pollution with outlier values in the site soil.