重庆芙蓉洞滴水现代次生化学沉积物沉积速率与元素特征

为了探讨芙蓉洞现代沉积物沉积速率和微量元素(Mg,Sr)的变化特征、控制机制以及气候环境指示意义,于2010年11月到2013年11月对芙蓉洞5个滴水点进行连续现场监测,并采集现代沉积物样品进行沉积速率计算和微量元素测定。结果显示:(1)芙蓉洞5个滴水点的现代沉积物沉积速率与滴量、pH、Ca2+浓度以及PCO2等指标的关系表现出多样性。其中MP4和MP5的沉积速率均与滴量呈正相关(r=0.75,n=11,p0.01;r=0.63,n=11,p0.05),两个滴水点的沉积速率整体表现出雨季高、旱季低的变化规律,表明MP4和MP5的沉积作用主要发生在雨季,其沉积速率的变化可以对季节性干湿度变化做出响应。(2)2012-2013年年降水量明显增加,在稀释作用、水岩作用以及植物对元素差异性吸收作用的影响下,各滴水点现代沉积物整体呈现出Mg浓度减小而Sr浓度增大的趋势,Mg/Ca和Sr/Ca比值呈反相关关系,它们响应了年际尺度上降水量增加的气候信息。

Deposition rates and element features of active sediments under drip water in Furong cave of Chongqing

To explore the variation, control mechanism and environmental significance of deposition rates and elements in the recent sediments under drip water in the Furong cave, Chongqing, five drip sites were monitored continuously from November 2010 to November 2013, and recent sediments were collected for the deposition rate calculation and determination of trace elements. The results show distinct correlations among the deposition rates and the discharges of drip water, pH, Ca2+ concentration, PCO2 of the five drip sites. The deposition rates of MP4 and MP5 are both positively correlated with their discharges of drip water (r=0.75, n=11, p<0.01; r=0.63, n=11, p<0.05, respectively), and the deposition rates of the two drip sites exhibit obvious variations, high in rainy seasons while low in dry seasons. The deposition of MP4 and MP5 occur mainly in rainy seasons. The changes of their deposition rates can indicate the dry and humid changes of the outside environment. The annual precipitation increased during 2012-2013. Under the influence of dilution effect, water-rock interaction and different absorptions of plants for elements, the concentration of Mg decreased while the Sr concentration increased. At the same time, the Mg/Ca is negatively correlated with the Sr/Ca. They can respond to the increasing of the precipitation on the interannual time scale.