Title: Fluorine Speciation in Loess in The Shaanxi Loess Plateau, Related Quality Assessment And Exposure Risks Implication
Abstract: 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.