SPATIAL AUTOCORRELATION ANALYSIS FOR THE DISTRIBUTION OF PER- AND POLYFLUOROALKYL SUBSTANCES (PFAS) IN ALABAMA SURFACE WATERS

Among the emerging contaminants of concern (CECs), per- and poly-fluoroalkyl substances (PFAS) have been known to be widely detected in surface water across the United States. In the present study, we examined seventy-five (75) PFAS samples across ten (10) major river basins and four (4) minor rivers in Alabama. Among them, the total summed concentrations of sixty-six (66) detected PFAS contaminants were analyzed using spatial autocorrelation model (Global and Local Moran’s Index) to identify spatial clusters and probable sources. The highest concentrations were observed along Alabama and its tributary, the Coosa River, indicating a likely source area for PFAS within the Coosa River basin in the southeast of Alabama. Analysis based on the spatial agglomeration results indicated elevated PFAS levels downstream of wastewater treatment plants (WWTPs), military bases, airports, and industrial facilities for short-chain PFAAs (PFBS, PFPeA, PFHxA, PFHpA) and long-chain PFAAs (PFOS and PFOA). These locations likely serve as primary sources of PFAS pollution in the area. The Tombigbee and Black Warrior Rivers, both tributaries to the Mobile River exhibited notable coldspots, along with the Conecuh, and Yellow Rivers. Negative autocorrelation (a pattern of high PFAS concentration near low concentrations) along the Choctawhatchee and Mobile Rivers in south Alabama implied spatial heterogeneity, suggesting potential PFAS sources in tributary watersheds. To evaluate the significant trend of PFAS, the Global Moran’s I spatial autocorrelated model summary sheet was back-calculated for the summed concentrations of PFAS, which was 0.414, indicating a positive and significant correlation.

Keywords: Per- and -polyfluoroalkyl substances, Spatial autocorrelation, Spatial Agglomeration, Source apportionment.