典型岩溶地区岩溶泉溶解性碳浓度变化及其通量估算

溶解性无机碳(DIC)和溶解性有机碳(DOC)是岩溶作用、碳汇与碳循环研究的重要指标.为增进对小流域岩溶泉DIC和DOC运移特征的认识,提升离散、有限的水质监测数据条件下碳通量的估算精度,研究了贵州普定陈旗岩溶泉DIC和DOC浓度的变化特征,采用LOADEST模型建立了估算DIC和DOC日通量的回归方程,并估算了陈旗岩溶泉的岩溶碳汇强度.结果表明,陈旗岩溶泉DIC和DOC的浓度分别为16. 47～42. 31 mg·L~(-1)和0. 87～6. 89 mg·L~(-1),它们分别随瞬时径流量的增加呈指数减小和增加.从LOADEST模型构建的回归方程可知,DIC日通量主要受径流量的影响,DOC日通量受径流量和时间的影响;陈旗岩溶泉DIC和DOC的估算通量分别为9 490. 01 kg·a~(-1)和1 704. 87 kg·a~(-1),陈旗岩溶泉的岩溶碳汇强度为3. 40 g·(m~2·a)~(-1). LOADEST模型是低频率水质监测条件下估算岩溶泉DIC和DOC通量的有效工具.

Concentration Variations and Flux Estimation of Dissolved Carbon in Karst Spring of a Typical Karst Area

Dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) are two important indices for studying karstification, carbon sinks, and the carbon cycle. In order to further understand the migration characteristics of DIC and DOC in karst springs in small watersheds and improve the estimation accuracy of carbon flux under conditions of discrete and limited water quality monitoring data, the concentration variations of DIC and DOC were studied in karst outlet springs of Chenqi small watershed in Puding County, Guizhou Province, China. The flux estimation regression equations of DIC and DOC were established by the LOADEST model, and the carbon sink intensity in Chenqi karst spring basin was estimated. The results showed that the concentrations of DIC and DOC were 16.47-42.31 mg·L^-1 and 0.87-6.89 mg·L^-1, which displayed exponential decrease and increase with increased instantaneous runoff, respectively. Based on the regression equations constructed by the LOADEST model, the daily flux load of DIC was mainly affected by runoff, whereas that of DOC was affected by both time and runoff. The estimated total fluxes of DIC and DOC were 9490.01 kg·a^-1 (95% confidence interval of 11293.58-7972.33 kg·a^-1) and 1704.87 kg·a^-1 (95% confidence interval of 1895.24-1553.24 kg·a^-1), respectively. The carbon sink intensity of the Chenqi karst spring basin was 3.40 g·(m²·a)^-1[95% confidence interval of 2.85-4.05 g·(m²·a)^-1]. The LOADEST model fully utilized discrete and limited water quality data to improve flux estimation accuracy from the monthly average to the daily average. Therefore, it is an effective tool to estimate the fluxes of DIC and DOC in karst springs under low frequency water quality monitoring conditions.