内蒙古高原达里诺尔湖氟化物分布特征及成因

Distribution characteristics and cause of fluoride in Dalinuoer Lake in Inner Mongolia

达里诺尔湖位于内蒙古高原,是典型的原生高氟区。为揭示湖泊氟化物的分布特征及成因,采集达里诺尔湖上覆水和表层沉积物,对氟化物的空间分布及其赋存形态进行了详细调查,并探讨了达里诺尔湖氟化物的来源及环境因素对水体氟化物的影响。结果表明:达里诺尔湖水体中氟化物浓度为3.91~4.61 mg/L,平均值为4.41 mg/L,显著高于GB 3838—2002《地表水环境质量标准》Ⅴ类阈值(1.5 mg/L)。表层沉积物中氟化物浓度变化范围为252.69~940.14 mg/kg,平均值为643.07 mg/kg,高值主要分布在湖泊西南部和湖心区。从形态上看,各形态氟含量整体表现为残余态>有机结合态>水溶态>铁锰结合态>可交换态,其中水溶态氟在一定环境条件下易向水体释放,成为达里诺尔湖水体中氟化物的主要内源。稳定度风险评估表明,达里诺尔湖沉积物中氟化物整体处于中等风险水平。达里诺尔湖的高氟水是在地层岩性引起的高自然本底值下,寒旱气候、特殊水化学条件、入湖河流及内流湖蒸发浓缩特征等环境因素的共同影响所致。研究结果可为达里诺尔湖及其他高氟湖泊的生态环境安全评估提供理论支持和科学依据。

Dalinuoer Lake is located in Inner Mongolia of Plateau in Northern China,which is a typical primary high fluorine area.In order to reveal the distribution characteristics and causes of fluoride in the lake,the overlying water and surface sediments of Dalinuoer Lake were collected,and the spatial distribution and occurrence of fluoride were investigated in detail.The source of fluoride in Dalinuoer Lake and the influence of environmental factors on fluoride in water were discussed.The results indicated that the fluoride content in Dalinuoer Lake ranged from 3.91 to 4.61 mg/L,with an average value of 4.41 mg/L,significantly exceeding GradeⅤthreshold(1.5 mg/L)for Environmental Quality Standards for Surface Water(GB 3838-2002).The fluoride content in surface sediments varied from 252.69 to 940.14 mg/kg,with an average value of 643.07 mg/kg.Spatially,the area with high fluoride content was mainly distributed in the southwest and middle areas of Dalinuoer Lake.Regarding forms,the fluoride concentration in various forms generally showed a pattern of residual>organic bound>water soluble>ironmanganese bound>exchangeable,and the water-soluble fluoride was easy to release to the water body under certain environmental conditions,which became the main endogenous source of fluoride in Dalinuoer Lake.The stability risk assessment indicated that the fluoride in the sediment of Dalinuoer Lake was generally at a moderate risk level.The high fluorine water in Dalinuoer Lake was affected by environmental factors such as cold and dry climate,special hydrochemical conditions,the evaporation and concentration characteristics of inflow rivers and internal lakes under high natural background value caused by stratigraphic lithology.The results could provide theoretical support and scientific basis for the ecological environment security evaluation of Dalinuoer Lake and other lakes with high fluoride.