Characteristics and risk assessment of surface water fluorine pollution in Ningxia section of Yellow River Basin.

In spring (April), summer (July) and autumn (October) of 2019 and 2021, six times were collected at 99 points in the Ningxia section of the Yellow River Basin. The 99 points were divided into 8 water systems which including the main stream of the Yellow River (S1), Qingshui River (S2), Kushui River (S3), Drainage ditch on the north bank of the Yellow River in Weining Section (S4), drainage ditch on the south bank of the Yellow River in Weining Section (S5), drainage ditch on the west bank of the Yellow River in Qingshi Section (S6), drainage ditch on the east bank of the Yellow River in Qingshi Section (S7), and urban landscape River and lake (S8), and the temporal and spatial distribution of fluorine was analyzed, the influence of environmental factors on fluorine enrichment was analyzed, and ecological and health risk assessment was carried out. The results showed that the average fluoride concentration of surface water in Ningxia section of the Yellow River Basin was 1.46mg/L, higher than the standard value of drinking water in China (1.0mg/L). Influenced by evaporation concentration and rainfall dilution, the fluorine concentration changed from high to low in autumn, spring and summer. The exceeding fluorine was the most serious in the Kushui River, Qingshui River and drainage ditch on the east bank of the Yellow River in Qingshi Section, and the main stream of the Yellow River was the only water system that was not polluted by fluoride. The average ecological risk of surface water fluoride in Ningxia section of the Yellow River Basin reached the low risk level, and the medium risk ratio was 27.84% in autumn, 22.33% in spring, and 11.11% in summer. The highest ecological risk of fluoride was found in the Kushui River, with the medium risk ratio reaching 80%. The results of the health risk assessment showed that except for the main stream of the Yellow River, other seven water systems posed health risks to both children and adults, and the harm to children was much greater than that to adults. The temporal and spatial distribution of fluorine was mainly affected by natural factors, and the dissolution of evaporite weathering and evaporation concentration were the main factors of fluorine enrichment in this area. © 2023 Chinese Society for Environmental Sciences. All rights reserved.