Characteristics and mechanism of spatial-temporal changes of fluorosis in typical high fluoride areas of Northwest China over the past 40 years

Abstract

Abstract Since the 1980s, China, especially the northwest part had carried out extensive water-improving project to reduce fluoride, but the fluorosis has not been completely eliminated. Through historical data comparison, on-site investigation and sample detection, combined with hydrochemical analysis and spatial analysis, this paper studied the 40 years’ changes of water fluoride and the control effect of fluorosis in the typical fluorosis areas Dali County of northwest China. Results show that from 1980 to 2017, benefited from the water-improving project, the fluoride in local residents' drinking water significantly decreased, with the median value declined from 2.40 to 1.26 mg/L, which further reduced fluorosis. As a typical water-improving area by low-fluoride water sources developing, in Dali, the generally dropped fluoride of groundwater is the root cause for the controlled endemic fluorosis. The enrichment of fluoride in groundwater here is controlled by the fluoride-rich geological background, landform and evaporative climate. The water environment characterized by slight alkalinity, rich sodium and low calcium is also an important factor. For the temporal changes of groundwater, human irrigation activities were considered as the primary role. Although the fluorosis has improved significantly, low residents' satisfaction and the rise of fluoride concentration in some water sources have led to a continuous high fluoride water drinking and fluorosis in some areas. It is suggested that the local government should strengthen water quality improvement from the aspects of low fluoride water source development and water supply management to consolidate the effect of fluorosis prevention and control.