典型喀斯特流域旱雨季交替下溶解硅的输送特征

Abstract

河流溶解硅（DSi）作为营养物质对维持陆地、河流及海洋生态系统稳定性起到至关重要的作用。选取贵州典型喀斯特流域为研究对象，通过对DSi湿沉降过程，基流过程及降雨径流过程的动态变化进行全年监测分析，探讨DSi在旱雨季交替下的输送特征及河流DSi浓度变化引起的环境效应。结果表明：①湿沉降过程降雨量越大，DSi浓度越小，河流DSi浓度变化有明显的旱、雨季特征，雨季DSi浓度较高，旱季较低，地表水径流量及DSi浓度对降雨径流过程的响应比地下水明显。②DSi沉降通量及输出通量呈明显的旱、雨季差异，雨季DSi湿沉降通量占全年的69.5%，地表水雨季DSi输出负荷占全年的98.1%，地下水占51.4%。③流域硅酸盐岩风化过程不强烈，主要受到碳酸盐岩及蒸发岩控制。流域DSi浓度受人为水库影响明显，经过水库后河流中DSi浓度旱季下降29.0%、雨季下降70.9%。研究为全面认识硅在陆地生态系统中的生物地球化学循环提供科学依据。;Dissolved silicon (DSi) in natural waters plays important roles in sustaining continent, riverine and ocean ecosystems. It is a necessary nutrient for the growth and reproduction of aquatic plants and phytoplankton, especially diatoms. The composition of dissolved silicon in river systems is complex and depends on physical, chemical, and biological processes that occur in drainage basins and rivers. In this study, a typical karst watershed located in Guizhou Province, Southwest China was selected as the study area to reveal the characteristics of DSi transport and discuss seriously environmental effects on the variation of DSi concentration. The objects of this research were to monitor the dynamic characteristics of dissolved silicon in wet deposition, rainfall-runoff processes and baseflow process in the dry and wet seasons during the whole year and to discuss about serious environmental effects on the variation of DSi concentration. Results showed that (1) The greater the rainfall, the smaller the DSi concentration during the wet deposition. DSi concentration in the wet season was higher than that in the dry season. DSi concentration and discharge in surface water were more easily responded by rainfall-runoff process than in groundwater. (2) The deposition flux and export flux of DSi showed evident differences in the wet and dry seasons. DSi deposition flux in the wet season accounted for 69.5%, and export load of surface water and groundwater accounted for 98.1% and 51.4% of the whole year, respectively. (3) The study area had a slow weathering rate of silicate minerals which was mainly controlled by carbonates and evaporite rates. DSi concentration was significantly affected by man-made reservoir as the results showed that the DSi concentration dropped by 29% and 70% in the dry and wet seasons, respectively. The study is conducive to a more comprehensive understanding of the silicon biogeochemical cycle in terrestrial ecosystems. In future studies, long-term studies on the effects of agricultural activities and land use patterns on the supply of nutrients in the watershed are needed to predict the change of phytoplankton community with the dynamic change of DSi concentration from a long-term perspective. In addition to DSi monitoring, BSi monitoring should be added to further study the silicon cycling process and related environmental effects in terrestrial ecosystems.