泰莱盆地西南部地下水位和硝酸盐浓度动态特征及成因机制

Dynamic Characteristics and Genetic Mechanism of Groundwater Level and Nitrate Concentration in Southwestern Tailai Basin

摘要:

地下水是物质运移和转化的重要载体。泰莱盆地西南部地下水硝酸盐浓度较高，目前针对该地区地下水位和地下水硝酸盐浓度动态变化特征及成因机制的研究较为缺乏。本文基于席桥、刘范和沙河站监测井20余年地下水位和水质动态监测数据，运用连续小波变换和小波相干分析，识别地下水位动态变化特征和影响因素，运用水化学图解法和离子比例关系法揭示枯水期和丰水期地下水硝酸盐浓度时空变化特征及成因机制。结果表明：地下水位呈现11 a、6~8 a和年际动态变化特征以及14 a动态变化趋势，地下水位周期变化特征主要受降雨影响；研究区水化学特征受水岩作用主导，主要来源于碳酸盐矿物和硫酸盐矿物溶解，还受阳离子交换作用影响；人类活动对地下水硝酸盐浓度影响显著，丰水期硝酸盐浓度显著高于枯水期，丰水期地下水中NO3主要来源于农业化肥污染，枯水期地下水中NO3主要来源于工业污水和粪便污染。

Abstract:

Groundwater is considered as the important carried fluid for the unground material migration and transformation. Groundwater is characterized by high NO3 concentration in the southwestern part of Tailai basin. However, dynamic change of groundwater and the spatiotemporal variation of nitrate pollution under the influence of human activities in this region has been studied very little. Based on monitoring data from three monitoring wells over 20 years, the continuous wavelet transform and wavelet coherence analysis have been used to identify the characteristics and external influence factors of groundwater level change. Hydrochemical diagrams and the ration of ionic centration have been used to explore the spatiotemporal variation of nitrate pollution and the sources of NO3 in groundwater. It is showed that the groundwater level exhibits dynamic changes of 11 years, 6~8 years, and interannual variations, as well as a dynamic trend of 14 years. The periodic variation of groundwater level is mainly influenced by rainfall.The hydrochemical characteristics of the study area are dominated by water rock interaction, and mainly derived from the dissolution of carbonate minerals and sulfate minerals. It is also influenced by cation exchange. Human activities have a significant impact on the concentration of nitrate in groundwater, with nitrate concentration significantly higher during the wet season than during the dry season. During the wet season, main source of nitrate in groundwater is agricultural fertilizer pollution, while during the dry season, main source of nitrate in groundwater is industrial wastewater and fecal pollution. During the wet season, NO3 in groundwater mainly comes from agricultural fertilizer pollution, while during the dry season, NO3 in groundwater mainly comes from industrial wastewater and fecal pollution.