| The geochemical study of the river can obtain the drainage basin chemical weathering, average chemical and isotopic composition of the upper crust. For nearly30years, Chinese scholars researched on hydrochemistry problems were more extensive and in-depth. However, hydrochemistry research about Guijiang basin focus on local basin in stead of the whole basin, it was relatively less and also not enough depth so far. Via the hydrochemistry test along the Guijiang river, analysis variations characteristics of the basin in time and space, and provide a scientific basis for the development and protection of water resources of the basin.The paper selected Guijiang watershed for the study area, on the basis of full investigation and master data of the climate, topography, geology and hydrogeology and the results of previous studies of the study area. Water samples were collected in the Guijiang river, on April9to16, July16to20, October11to15and Jan.14to18,2013as spring, summer, autumn, winter, respectively, and analysis water observational samples in a full hydrological annual. This article analysis spatial variation and its influencing factors of the watershed by the main stream and tributaries of the Guijiang river water chemistry test; In addition, karst carbon sink for the Guijiang river was researched from September2011to September2012through a complete hydrological year, to explore its change process and the laws of the amount of carbon sink and HCO3-in the river. In this study, we sat15points in Guijiang river, using the German WTW Multi340i portable water quality multi-parameter analyzer, and monitored each sampling point river water pH, water temperature (T), conductivity (EC) parameters on-site. River calcite saturation index (SIc)was calculated by hydrogeochemistry software PHREEQC. Cations (K+, Na+,Ca2+, Mg2+and NH3+) were analysised by Dionex ICS1500ion chromatograph and the anions (SO42-, NO3-, and Cl-) were analysised by Wantong MIC ion chromatograph.Karst carbon sinks was calculate through the water chemical-runoff method. Different scholars has different results about the river carbon sinks, because few studies on river flood. The amount of carbon sinks in the river floods, because HCO3-flood process may be due to the dilution effect of the decrease, but the flow has to increase in multiples. A more detailed study emerged,for the realization of a high-resolution real-time monitoring in the small watershed karst underground river and karst springs. Adverse conditions due to the fluctuation of water level, management inconvenience limitations for large and medium-sized basin surface karst area River, the instrument is difficult to automatically monitor, small karst area rivers high precision. Have been few studies of the low sampling frequency can not well reflect the dynamic changes of the river water chemistry and karst carbon sinks. Therefore, it is necessary to high-frequency monitoring of dynamic changes of the karst area rivers flood carbon sinks, to explore the river flood the HCO3-carbon sinks change process and law has important theoretical and practical significance of the accurate estimation of karst carbon sinks.We has high frequency day and night monitoring on the Li River in Yang Shuo hydrological stations at floods period, flat water and dry seasons on May8to17, July6to13and December3to10, respectively, flood water one hour of monitoring, flat water and dry seasons is two hours of monitoring. Underwater0.5m at the sampling point is located in the center line of a river.Through the above research, draw the following conclusions:1. Guijiang river basin water temperature between9.5～30℃, an average of20.9℃; pH values ranged from6.32to8.87, average7.61; As the lithological differences EC vary between18～379μs/cm, the average170μs/cm; SIC range of-4.04to0.98, and the average of-0.74. Guijiang water chemistry type is HCO3-Ca type, HCO3-average share of79%of the anion and Ca2+on average accounted for75%of the cation.2. Each ion concentration in the basin space variation:the middle reaches of limestone and other carbonate rocks are widely distributed, so Ca2+, Mg2+, HCO3-and SIc similar overall midstream high on the downstream low. Due to the impact of the industrial and agricultural activities, SO42-and NO3-in some tributaries of the the Guijiang river upstream and midstream was relatively high. Cl-, Na+and K+overall the middle and lower reaches higher, may be due to the precipitation and downstream sand shale formed.3. The Guijiang basin river ion variation in the seasons can be seen that the highest ion content of the river in winter, autumn and spring, followed by the summer river ion concentration is lowest. The phenomenon of the river inside this ion seasonal differences more summer precipitation the main ions dissolved in the river is a lot of rain diluted the opposite in winter, less precipitation, river have the highest ion concentration in winter.4. By monitoring at different times of the Lijiang River, we found karst carbon sink has a different variation:during floods because rainfall is high, may appear several flood peak, HCO3-may also be because of the dilution effect and diffusion boundary layer effect other factors change fluctuations; flat water and dry seasons change are similar because of rain less flow changes without changes in flood, HCO3-day changes in performance during the day and high night low, multi-day dynamic changes by the dilution effect impact.5. Through different periods of carbon sinks and flows and HCO3-correlation analysis found that carbon sinks and the flow is much higher than the correlation of carbon sinks and HCO3-, indicating that the primary factors that affect river carbon sinks was flow, but not HCO3-,and therefore strengthen the monitoring of flow is necessary.6. From September2011to September2012a complete hydrological year monitoring in the Guijiang River Basin, found HCO3-in autumn and winter than in spring and summer, in winter the average highest and lowest in summer. Changes in flow and HCO3-opposite, higher in the spring and summer, autumn and winter lower. It was highest in summer (average flow of1796m3/s), and lowest in autumn (average flow of only122m3/s). Water chemistry-runoff method to calculate the amount of carbon sinks, the overall performance of the spring and higher in summer, winter and fall lower characteristics. After the origin integral calculation derived the Guijiang river (Zhaoping sectional) annual carbon sink is about13253t C. |
PDF Full Text Request