Evaluation on the migrating quantity of fluorine among water-soil-rice system in soda saline-alkali soil as paddy field is developed

Soda saline-alkali soils are increasingly being developed for rice cultivation in western Jilin Province. This land-use change inevitably affects fluorine migration in paddy field ecosystems, particularly given the high background levels of fluorine in both soil and groundwater. However, the extent of this migration has not yet been quantitatively assessed. To investigate fluorine transport from soil to water and rice plants, we conducted a one-year pot experiment with 4 treatments of non-amendment (CK), Al 2 (SO 4 ) 3 (T1), desulfurized gypsum (T2) and compound amendment (a mixture of fungus bran, potassium humate and Al 2 (SO 4 ) 3 , T3), followed by a two-year field trial with 2 treatments of CK and T3. Our results demonstrated that total-F, water-soluble F and residual F decreased, while organic bounded F increased after the soil improvements for rice cultivation were applied. All amendments effectively enhanced exchangeable F and reduced water-soluble F, with the most significant effect observed in T3 treatment. Fluorine migration from soil to agricultural wastewater amounted to 33.14 mg/kg in the pot experiment and 6.77 mg/kg in the field trial during soil washing. Amendment treatments significantly reduced fluorine migration into both washing water and the paddy water layer. Compared to the CK, T3 reduced fluorine migration from soil to rice plants by 8.11 % and 46.52 % in the first and second planting years, respectively. Additionally, it decreased fluorine migration to agricultural wastewater by 50.14 % and 58.39 % and reduced downward migration by 62.52 % and 49.30 % in the respective years. These findings indicate that converting soda saline-alkali soil into paddy fields accelerates fluorine migration within the soil-water-rice plant system, while the compound amendment optimized the soil environment to enhance fluorine adsorption and fixation, thereby significantly reducing its migration into water and rice plants. • Soda saline-alkali soil developed to paddy field accelerated fluorine migration. • Amendments promoted exchangeable F and declined water-soluble F. • Soil washing caused the migration of fluorine from soil to agricultural waste water. • The compound amendment reduced fluorine downward migration and absorbed by plants.