Distribution characteristics of fluorine in soils of Zhujiang River delta in relation to endemic fluorosis

Abstract：The content and distribution characteristics of F in soils in the whole region and the typical areas of the Zhujiang River delta were studied by contrast with the F background of soils in the Zhujiang River delta and whole China. Soil types, parent rocks and land use types affecting the above situation were analyzed in this paper, and the relations between F content of soils and endemic fluorosis were discussed. The results show that the F average value of surface soils and deep soils in the Zhujiang River delta is respectively 510 mg/kg and 529 mg/kg. The F content of the delta gleyed paddy soils, delta salinized paddy soils and irrigated land in Quaternary marine (continental) loose layer areas is the highest. The high F background areas of surface soils whose acreage is 6760 km2 are distributed in the central plain, the F pollution areas are spread in local areas of Dongguan, Xinhui and Zhuhai. The acreage of high F background areas of deep soils is 5504 km2, the F pollution areas are distributed in Gaolan island and Sanzhao island of Zhuhai City. The enrichment of F in soils is obviously related to Quaternary marine-terrigenous and terrestrial-marine facies sediments, and evidently has to do with granitoids in the bedrock. The soils influenced by human activity, paddy soils and their salinization seem to be beneficial to F enrichment . The endemic fluorosis in this region is distributed in Conghua, Zengcheng, suburbs of Dongguan, Naihai, Xinhui and Enping, where endemic areas are located in high F strata, rocks and soils. There exists excessive F in the crops growing in soils of high F background areas, and the F excessive rates and excessive times of crops in endemic areas are greater than those of crops in the non-endemic areas, suggesting that the proportion of bioavailable dose of F in soils in pollution areas is high, and F in soils has been migrated and enriched in agricultural products, which jeopardizes the quality of agricultural products. High F soils and crops in the study region caused by high F geological environment become factors responsible for endemic fluorosis.