亚热带典型岩溶区地表溪流水文地球化学昼夜变化及其影响因素研究

Diel Variations of Hydrochemistry and Influencing Factors in a Surface Stream in Subtropical Karst Area,SW China

为了解岩溶区地表溪流水文地球化学的昼夜变化过程及其影响因素,于2013-07-09～2013-07-14期间,在广西壮族自治区融安县官村地下河出口(G1)和下游雷崖村(G2)设置两个监测点同时展开了为期5 d的高分辨率昼夜监测工作,每15min监测水温(T)、pH、溶解氧(DO)和电导率(Spc),每2 h进行人工采样工作,样品测试Ca2+、HCO-3和NO-3等主要离子以及δ13CDIC.结果发现:1 G1和G2点都是HCO3-Ca型水,但是两个监测点表现出不同的水文地球化学昼夜变化过程;2监测期间官村地下河出口(G1)的物理化学参数和主要离子(Ca2+、HCO-3和NO-3等)基本上保持稳定,而雷崖监测点(G2)的物理化学参数(T、pH、DO、Spc)和Ca2+、HCO-3和NO-3离子表现出有规律的昼夜变化特征;3 G2监测点的溶解无机碳(DIC)和δ13C值表现出相反的昼夜变化特征,DIC在白天下降晚上升高而δ13C值白天上升晚上下降,并表现出较好的负相关关系(相关系数为-0.87,P<0.01).结果表明,水生植物的光合作用和呼吸作用、水温以及脱气作用共同影响岩溶区地表溪流水文地球化学的昼夜变化,控制了岩溶地表溪流内部物质循环过程.

In order to understand the diel variation and influencing factors of hydrochemistry in a surface creek fed by karst subterranean river in a subtropical area,where is located at Guancun Village,Daliang Township,Rong＇an County of Guangxi Zhuang Autonomous Region,China,two monitoring sites were set simultaneously to launch Guancun subterranean river outlet（G1） and surface creek mouth（G2）,respectively. Physical and hydrochemical parameters including pH,dissolved oxygen（DO）,water temperature（T） and specific conductivity（Spc） were measured at 15-minute intervals and water samples for analyzing major ions such as Ca^2＋,HCO3^-and NO3^-as well as δ^13DICwere collected at 2-hour intervals. The results showed that： 1 G1 and G2 sites were both HCO3-Ca type water,however the two monitoring sites showed different diel variations of hydrogeochemical process; 2 The physical and hydrochemical parameters（T,DO,pH,Spc） and major ions（Ca^2＋,Mg^2＋,Na^＋,K^＋,HCO3^-,SO4^2-,NO3-3,Cl^-） in G1 site were basically stable,while the physical and hydrochemical parameters（T,DO,pH,Spc） and major ions（Ca^2＋,HCO3^-and NO3^-）in G2 site displayed regular diel variation during monitoring; 3 The dissolved inorganic carbon（DIC） and δ^13 values in G2 monitoring site showed reverse characteristics in diurnal fluctuations,where DIC decreased in daylight and increased at night while theδ^13 value increased in daylight and decreased at night,DIC also showed a negative correlation with the δ^13 value（correlation coefficient is- 0. 87,P 0. 01） in G2 site. These results indicatd that photosynthesis and respiration of aquatic plants,water temperature and degassing jointly affected diurnal variation of hydrochemistry and controlled the cycling process of internal matter in this surface creek fed by karst subterranean river.