Translocation And Transformation Of Fluorides Between Interfaces Of Soil, Water And Air In Relation To Their Ecological Effects

Fluoride is an essential element for animals and human beings. Unbalance of fluoride (F) in human body can cause diseases of teeth and bones. Soil, as a central media for the behavior of fluoride in the environment, plays an important role in the distribution and translocation of fluoride in the environment. Therefore, Study on the translocation and transformation of fluorides in soil environment is of important significance to control the fluoride pollution. A series of experiments and investigations in this paper were conducted to study the translocation and transformation of fluorides between interfaces of soil, water, and air in relation to their ecological effects, using paddy soils, red soils and others typical soils from Zhejiang Province. The main research results were summarized as follows:1. The translocation and transformation of fluoride between the interface of soil and water and their influence on the translocation of fluoride in soils to groundwater and food chain(l)Forms of fluoride in 15 soils developed from different parent materials were studied using sequential chemical extraction procedure: fluoride bound to Fe/Mn oxides (Fe/Mn-F), bound to organic matter (Or-F). The contents of different fluoride forms were decreased in the order. Residual fluoride(Res-F) exchangeable fluoride (Ex-F) > water soluble fluoride (Ws-F) > fluoride bound to organic matter (Or-F) > fluoride bound to Fe/Mn oxides (Fe/Mn-F). Ws-F contents were 0.57 mg/kg on average, ranging from 0.12 - 1.72 mg/kg, only about 0.14% of total fluoride in 15 soils, and 1.24mg/kg on average in paddy soils from Hang-Jia-Hu plain, Zhjiang Province.(2)Correlation analysis on different fluoride forms in 15 soils showed that Ws-F was significantly correlated with Ex-F (r = 0.7775). Ex-F was not only correlated with Ws-F, but also correlated with Fe/Mn-F Cr = 0.5753) and Organic-F (r = 0.5529). It was concluded that Ws-F could be transformed from Ex-F.(3) Stepwise linear regression analysis and correlation analysis was used to test the effect of various soil components on the contribution of fluoride forms, indicating that soil pH. clay content, and soil parent materials were the important influential factors. Ws-F had positively significant correlation with pH value(r = 0.9510, n = 15; r = 0.4999, n = 510), and negative correlation with clay content. The soils developed from some deposits had higher Ws-F contents than from other parent materials in the 15 soils. Ws-F content was the highest in the paddy soil developed from marine deposit, followed by fluviatile deposit, and the lowest was residual deposit of red soil and yellow soil, in Hang-Jia-Hu paddy soils. The percentages of Ws-F of total fluoride in paddy soils from different parent materials followed the order: marine deposit > residual deposit of red soil and yellow soil > Lacustrine deposit > fluviatile deposit > Quaternary red clay.(4)The Ws-F content changed with the tendency of low-high-low in profile of Percogenic paddy soil (A-Ap-P) and Hydrogric paddy soil (A-Ap-W), and with tendency of low-high-high in profile of Gleyed paddy soil (A-Ap-G) and Submergic paddy soil (A-Ap-C).(5)Both the content of total fluoride and the content of exchangeable fluoride in Hang-Jia-Hu paddy soils followed the normal distribution. But the content of Ws-F didn't follow the normal distribution. The content of total fluoride was 294.1mg/kg on average, ranging from 137.7 to 465.3 mg/kg. The content of Ws-F was 1.24mg/kg on average, ranging from 0.23 to 4.23mg/kg. It was concluded that there was low fluoride bioavailability in paddy soils. The fluoride in the profile of Percogenic paddy soil, Hydrogric paddy soil, and Gleyed paddy soil couldn't result in the increase of fluoride in the groundwater, while fluoride in Submergic paddy soil might have influence on fluoride content in groundwater.2. The translocation and transformation of fluoride between soil and plant and their ecological effects(l)The extractability of four extractants was in the order: 1 mol/L HC1 > 1 mol/L NH4AC...