洞穴滴(流)水的双重(滴－侵蚀、沉积)作用——以桂林盘龙洞为例

洞穴滴水主要来源于大气降水的入渗,是岩溶洞穴内的低能量的渗流水,它受控于水- 土- 岩的相互作用。本文通过对桂林盘龙洞滴水一个水文年的动态监测表明,洞穴滴水对大气降水的响应较快,其所记录的滴水特性直接反映大气降水的物理、化学特征,并系统地记录了滴水溶- 侵蚀和沉积过程,以及与生态环境和石漠化的演化历史。常年性滴水的动态监测,揭示在夏半年( 5- 10月)是新碳酸盐的主要沉积时段,表现出新碳酸盐的沉积具有与雨热同季的特点。暴雨或季节性滴水基本保持了雨水的物理化学特性,滴水量大,滴速快,因而具有较强的溶- 侵蚀作用,导致盘龙洞石笋Pa、Pb、Pc 形成后被溶- 侵蚀的体积分别达339872 cm3、13 680 cm3 和33 792 cm3; 在冬半年,常年性滴水由于滴速和滴量较小,其溶- 侵蚀性较弱;而在夏半年,由于滴水的饱和度高,沉积量大,往往将在冬半年形成细微的滴溶蚀凹坑或孔穴填平补齐。 

Drip water deposits and erosion-dissolution process by drip water in karst cave-Taking the Panlong cave as an example

Drip water,a kind of seeping water with low energy in caves,mostly come from the atmospheric precipitating water.It is controlled by the interaction of water,soil and rock.Our monitoring for drip water through a hydrologic year in Panlong cave of Guilin indicates that cave drip water is of quick response to atmospheric precipitation and the recorded features by the drip water can directly reflect the physical and chemical characteristics of atmospheric precipitation.Not only the dissolving/eroding and depositing processes,but also the evolution processes of ecological environment and rocky desertification are also recorded systematically by the cave drip water.In particular,the perennial dynamic monitoring to the drip water has revealed that the summer half year(from May to October) is the main deposit stage of new CaCO3 which shows the deposit of new CaCO3 takes place in the same season with precipitation and heat.The rainstorm or seasonal drip water in cave can basically keep the original physical and chemical characteristics of atmospheric precipitation and is greater in flow amount and faster in flow velocity,so it has strong erosion-dissolution effect that has resulted in 339 872 cm3,13 680 cm3 and 33 792 cm3 in erosion-dissolution volume after stalagmite Pa,Pb and Pc in the cave being formed.The perennial drip water in the winter half year has weak erosion-dissolution process because it is smaller in flow amount and slower in flow velocity.In the summer half year,because the drip water is more saturated,the deposition is stronger which usually fill and level up the micro-flute or pot formed by drip water dissolution in the winter half year.