Fluorine Speciation in Loess in The Shaanxi Loess Plateau, Related Quality Assessment And Exposure Risks Implication

Abstract In this study, distributing characteristics of five fluorine (F) species in loess in the Shaanxi Loess Plateau (SLP) were determined including unextractable residual F (F re ), extractable water-soluble F (F ws ), exchangeable F (F ex ), F bound to Fe-Mn oxides (F fm ), and F bound to organics (F or ). The results show that unextractable F re represents most percentage of F tf in loess. Of the four extractable F species, the content of F ws is higher than the other three extractable F species in most loess samples. The loess in the southeast SLP has the highest F ws content while the loess in the southwest has the highest F tf content. And the loess in the north SLP contains the lowest overall concentrations of F tf and F ws . Similar to F ws , the respective content of F ex , F fm , and F or in the loess is also very low. However, the total of them and F ws cannot be negligible for F mobility in loess. Overall, the loess in the SLP can be assessed as inferior quality in terms of F as a result of high F ws content in most samples. Based on the F speciation in the loess, F exposure to grazing animals and humans, in fact to children, was assessed, indicating that F in the loess in the southwest SLP might pose a much greater risk to grazing animals than in other part of SLP as the loess contains more F tf . However, there is no concern for the children’s exposure to loess F via ingestion in the study area in the present condition. As for the loess F risk to groundwater, it can be concluded that not only F ws but also the other extractable F including F ex , F fm and F or in loess may be responsible for the F enrichment in local groundwater in the area with the aid of the characteristics of F speciation in loess and distribution of local high-fluoride groundwater.