Concentration and distribution of metals, total fluorine, per- and poly-fluoroalkyl substances (PFAS) in vertical soil profiles in industrialized areas.

The widespread usage of per- and poly-fluoroalkyl substances (PFAS) has caused great concern due to their potential toxicology to human and environmental health. However, there have been limited investigations on the vertical distribution of PFAS in fluorine (F) contaminated soils. In this study, the spatial and vertical distribution of metals, total F, and PFAS in the soil profiles were investigated at different areas in an industrial city. The higher F concentrations in the farmland soils with intensive agricultural activities suggested the impacts of soil tillage. The ΣPFAS concentrations ranged from 0.187 to 1.852 ng g-1 in all soil samples, with PFOA as the dominant pollutant, which accounted for 17.2%-51.6% of the ΣPFAS in all samples. Highest level of PFAS was found in the shallow layer of the soil profiles. The long-chain PFAS such as PFUdA and PFTeDA tended to remain in the topsoil, while the short-chains (PFBA, PFPeA, and PFHxA) have migrated to depth of 100 cm in the vertical soil profile. The application of F-enriched phosphorus fertilizers and atmospheric deposition may be important sources of F and PFAS in soils in this area. Correlation analysis indicated that most of PFAS have similar common sources, and the significantly positive correlation between Zn and PFAS suggested they may share similar sources. This study highlights the need for further work to monitor the PFAS level in soil environments in industrialized areas, in addition to focusing on soil metal and F pollution.

Agricultural activities impact on soil and sediment fluorine and perfluorinated compounds in an endemic fluorosis area.

Perfluorinated compounds (PFCs) are organo-fluorine compounds which have been identified at significant levels in soils due to their widespread usage in industrial and commercial applications. However, few studies are available regarding the occurrence of PFCs in the environment of endemic fluorosis areas. To address the issue, soils collected from an endemic fluorosis area of southwestern China were analyzed for the distribution of fluorine and 21 kinds of PFCs. The average water-soluble fluorine concentration in cultivated soil (4.87 mg kg-1) was significantly higher than that in uncultivated soil (3.15 mg kg-1), which mainly ascribed to the utilization of fluorine-enriched fertilizers during agricultural practices. Concentrations of ΣPFCs in all soils ranged from 0.508 to 6.83 ng g-1, with an average of 2.81 ng g-1, dominated by perfluorononanoic acid (PFNA) and perfluorooctanoic acid (PFOA). Highest ΣPFCs was found in the soil samples collected from cropland with intensive agricultural activities. Long-chain PFCs, including four perfluoroalkylcarboxylic acids (PFCAs, C ≥ 8) and one perfluoroalkylsulfonic acids (PFSAs) (perfluorooctane sulfonate (PFOS), C8), exhibited high levels in soils, probably due to their higher hydrophobicity and lower water-solubility than short-chain PFCs. While in sediments, short-chain PFCAs were the dominant compounds. Based on correlation analysis, the relationship between total fluorine and PFCs was insignificant, and soil organic matter was a relevant factor affecting PFCs distribution in soils. This study is expected to present a more comprehensive information about fluorine contamination under the influence of agricultural activities in an endemic fluorosis area.