摘要:
钙华是岩溶区常见的次生化学沉积物,也是陆地气候环境信息的高分辨率载体之一.它的形成常常与水生植物有关,后者的新陈代谢过程可能会改变水中溶解无机碳(DIC)的同位素组成,进而影响钙华的碳同位素值.然而在古环境重建中,永生植物引起微环境变化所造成的影响常常被研究者忽视.本研究选取了白水台两个具有丰富沉水植物的钙华水池,对水池入口、出口的水化学和DIC的碳同位素组成(δ13 CDIC)进行了高分辨率的昼夜观测和取样分析.结果显示,在低浓度DIC水体(S1-3)补给水池时,水池出口与入口之间的δ13 CDIC的变化很小,主要反映的是出口δ13CDIC继承入口δ13 CDIC,反映了滞后效应对水体δ13CDIC的控制;而在高浓度DIC水体(S1-1)补给水池时,水池出口与入口之间的δ13CDIC的变化主要受脱气作用控制.通过对水生光合作用影响比例的计算发现,由于库效应的存在,水生植物的光合作用对δ13CDIC的影响很小.
Abstract:
Travertine is a common secondary chemical sediment in karst areas,also one of the continental high-resolution climatic archives.Its formation is often associated with aquatic plants,whose metabolism can likely change hydrochemistry and carbon isotopic composition of dissolved inorganic carbon (DIC),thus affecting the carbon isotopic composition of travertine.However,the influence of micro-environment caused by aquatic plants is usually ignored when reconstructing paleoenvironments using carbon isotopic composition of travertine.A method of combining on-site high-resolution monitoring and in-situ titrating with measurement of samples in laboratory was used in present study to investigate the influence of submerged plant on hydrochemistry and carbon isotopic compositions of pool water.The results show that when pools were fed by low DIC concentration water (S1-3),the δ13CDIC difference between the outlet and inlet of the pool reflects the control of hysteresis effect,while fed by high DIC concentrations water (S1-1),the δ13CDICdifference between the outlet and inlet of the pool indicates the control of degassing effect.Because of the existence of the reservoir effect,the influence of metabolism of submerge plant on δ13CDICis small.
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