| 摘要: |
| 极端降水是影响水环境质量的重要气象因素之一，随着全球气候变暖，极端降水事件的频率和量级呈显著上升的趋势，对湖泊水化学和水环境产生了深刻的影响.白洋淀是华北地区重要的湖泊型湿地和生态功能区，为查明极端降水条件下白洋淀主淀区的水化学和水质特征，本研究利用Piper三线图、Gibbs图和多元统计方法阐明了白洋淀极端降雨后的水化学特征、氢氧稳定同位素特征和水质空间变化，揭示了极端降水条件对白洋淀主淀区水化学和水质的影响.结果表明：（1）在极端降水条件下，白洋淀主淀区湖水呈弱碱性，水化学类型主要为Ca-HCO3·SO4型，极端降水减弱了蒸发结晶作用和人类活动等因素对白洋淀主淀区湖水水化学组成的影响.极端降水是导致白洋淀主淀区pH、电导率和总溶解性固体发生大幅度变化的原因之一.（2）极端降水条件下白洋淀主淀区湖水的δ2H和δ18O值的范围分别为-60.86‰~-35.01‰和-8.84‰~-3.45‰，其值均与水深呈显著负相关.极端降水使得白洋淀主淀区湖水的氢、氧稳定同位素贫化，但对其空间分布的影响不大，湖水氢、氧同位素关系受降水本身氢、氧同位素关系的影响更为强烈.强降水引起白洋淀的水深突然增加，导致湖水受到的蒸发分馏作用影响减弱.（3）极端降水增加了面源污染扩散的速度，导致白洋淀主淀区湖水中的氨氮、硝态氮和总磷等营养物质浓度升高，白洋淀大气降水中的氨氮也可能导致极端降水条件下主淀区湖水中氨氮浓度升高，而上游水库为了应对强降雨事件进行的调蓄放水使得白洋淀东北部水质有所改善.该研究为白洋淀的生态修复治理和雄安新区的生态系统管理提供了科学依据. |
| 关键词: 极端降水 水化学特征 氢、氧稳定同位素 水质 白洋淀 |
| DOI：10.18307/2022.0613 |
| 分类号: |
| 基金项目:国家重点研发计划项目（2019YFA0607102）资助. |
|
| Hydrochemical characteristics and water quality variations in the main area of Lake Baiyangdian under extreme precipitation |
|
Han Yuli1,2, Bu Hongmei1,2
|
|
1.Key Laboratory of Water Cycle and Related Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, P. R. China;2.College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, P. R. China
|
| Abstract: |
| Extreme precipitation is one of the important meteorological factors affecting water quality. With global warming, the frequency and magnitude of extreme precipitation events have increased significantly, which greatly influenced the hydrochemistry and water environment in lakes. Lake Baiyangdian is an important wetland and ecological area in North China. In order to identify the hydrochemical characteristics and water quality variations in the main area of Lake Baiyangdian under an extreme precipitation event, the Piper diagram, Gibbs diagram, and multivariate statistical methods were used to elucidate the hydrochemical characteristics, hydrogen and oxygen stable isotope characteristics, and spatial variations of water quality in this study. Accordingly, the effects of the extreme precipitation event on the hydrochemistry and water quality were detected in the main area of Lake Baiyangdian. The results showed that (1) Lake water is weakly alkaline, and the hydrochemistry type is Ca-HCO3·SO4 under the extreme precipitation event. The extreme precipitation weakened the effects of evapotranspiration and human activities on the chemical compositions of the lake water. The extreme precipitation also led to the large changes in pH, electrical conductivity and total dissolved solid values in the lake water. (2) The hydrogen and oxygen isotopic values (δ2H and δ18O) respectively ranged from -60.86‰ to -35.01‰ and from -8.84‰ to -3.45‰, showing significant negative correlations with water depths. Although the hydrogen and oxygen stable isotopes of the lake water were depleted by the extreme precipitation, the extreme precipitation did not affect their spatial distribution. The relationship between δ2H and δ18O values is more strongly influenced by the correlation between δ2H and δ18O values in precipitation itself. Additionally, the heavy precipitation caused a sudden increase in the water depth of the main area of the lake, which weakened the influence of evaporative fractionation on the lake water. (3) The extreme precipitation raised the diffusion rate of non-point source pollution and increased the concentrations of ammonia nitrogen, nitrate nitrogen and total phosphorus in the lake water. The ammonia nitrogen, in precipitation may also increase the ammonia nitrogen concentration in lake water. Additionally, releasing water from reservoirs located in the upper reaches of the lake in response to extreme precipitation improved the water quality in the northeastern area of the lake. This study provides a scientific basis for the ecological restoration of Lake Baiyangdian and the ecosystem management of Xiong'an New Area. |
| Key words: Extreme precipitation hydrochemical characteristics hydrogen and oxygen stable isotopes water quality Lake Baiyangdian |
