Li Desheng, Jiang Chunlu, Jiang Chenghong, Liu Feng, Zhu Qiyu
School of Resources and Environmental Engineering, Anhui University, Hefei 230601, Anhui, China.
School of Resources and Environmental Engineering, Anhui University, Hefei 230601, Anhui, China; School of Resources and Geoscience, China University of Mining and Technology, Xuzhou 221116, Jiangsu, China.
Sci Total Environ. 2023 Dec 15;904:166668. doi: 10.1016/j.scitotenv.2023.166668. Epub 2023 Sep 1.
Mining activities cause surface subsidence and the formation of subsidence lakes, which dynamically change with the continuous coal mining activities. Under the combined influence of various human activities such as agriculture, aquaculture, and floating photovoltaic (FPV), the lake environment undergoes continuous changes, thereby altering the geochemical characteristics of rare earth elements (REEs) in the sediment. This study focused on the subsidence lakes in the Huainan coalfield in eastern China to examine the REEs content in the sediment, elucidated the temporal variations and geochemical characteristics of REEs distribution, explored the main controlling factors of REEs in the sediment, and revealed the migration and transformation behavior of REEs during dynamic subsidence processes. The study revealed that the migration pattern of REEs in the sediment was closely related to the duration of subsidence. The average content of REEs in lake sediments with subsidence duration <5 years increased from 219 μg·g to 248 μg·g compared to the soil, showing an enrichment model primarily driven by rainwater runoff, groundwater input retention, and mineral dissolution. With further subsidence, the processes of reduction dissolution of Fe-Mn oxides/hydroxides, organic colloid adsorption, and hydraulic disturbance gradually replaced the aforementioned enrichment behavior as the main migration pathways, resulting in a decrease in the average REEs content in the sediment to 179 μg·g for subsidence durations exceeding 10 years. There was no strong correlation between REEs fractionation and subsidence duration. Artificial activities, such as FPV, are important factors causing Cerium and Erbium anomalies in some subsidence lake sediments. This study was not only of significant importance for understanding the migration, distribution, and environmental behavior of pollutants in aquatic environments under the interference of human activities but also provided a solid theoretical foundation for the future management of coal mining subsidence lakes.
采矿活动会导致地表沉陷和沉陷湖的形成，且随着煤炭开采活动的持续进行，这些情况会动态变化。在农业、水产养殖和漂浮光伏（FPV）等各种人类活动的综合影响下，湖泊环境不断变化，从而改变了沉积物中稀土元素（REEs）的地球化学特征。本研究聚焦于中国东部淮南煤田的沉陷湖，以检测沉积物中的稀土元素含量，阐明稀土元素分布的时间变化和地球化学特征，探究沉积物中稀土元素的主要控制因素，并揭示动态沉陷过程中稀土元素的迁移和转化行为。研究表明，沉积物中稀土元素的迁移模式与沉陷持续时间密切相关。与土壤相比，沉陷持续时间<5年的湖泊沉积物中稀土元素的平均含量从219μg·g增加到248μg·g，呈现出主要由雨水径流、地下水输入滞留和矿物溶解驱动的富集模式。随着进一步沉陷，铁锰氧化物/氢氧化物的还原溶解、有机胶体吸附和水力扰动等过程逐渐取代上述富集行为，成为主要迁移途径，导致沉陷持续时间超过10年时沉积物中稀土元素的平均含量降至179μg·g。稀土元素分馏与沉陷持续时间之间没有很强的相关性。诸如漂浮光伏等人工活动是导致一些沉陷湖沉积物中铈和铒异常的重要因素。本研究不仅对于理解人类活动干扰下水生环境中污染物的迁移、分布和环境行为具有重要意义，也为未来煤矿开采沉陷湖的管理提供了坚实的理论基础。
