水生光合生物对茂兰拉桥泉及其下游水化学和δ^(13)C_(DIC)昼夜变化的影响  

Effects of aquatic phototrophs on diurnal hydrochemical and δ^(13)C_(DIC) variations in an epikarst spring and two spring-fed ponds of Laqiao, Maolan, SW China

作　　者：陈波[1,2] 杨睿[1,2] 刘再华[2] 晏浩[1,2] 赵敏[2] 

机构地区：[1]中国科学院大学,北京100049 [2]中国科学院地球化学研究所环境地球化学国家重点实验室,贵州贵阳550002

出　　处：《地球化学》2014年第4期375-385,共11页Geochimica

基　　金：国家重点基础研究发展计划(2013CB956700);国家自然科学基金项目(41172232)

摘　　要：碳酸盐风化能否形成稳定持久碳汇很大程度上取决于风化产生的溶解无机碳(DIC)能否被水生光合生物利用及其利用程度,后者可通过地表水水化学和?13CDIC的昼夜变化进行探讨。本研究对冬季茂兰拉桥表层岩溶泉及其中游和下游池水的温度、pH、电导率(EC)和溶解氧(DO)进行了为期30 h(1月27日10:00至1月28日16:00)高分辨率(15 min/次)的昼夜动态监测和?13CDIC定期取样(白天每隔2 h,夜间每隔4 h)测定,以了解水生光合生物对水化学和?13CDIC昼夜动态变化的影响。同时,结合水面静态箱CO2测定获得的岩溶水与空气CO2交换通量,对生物碳泵效应进行了估算。结果表明,在少有沉水植物生长的泉口及其下游水池,水化学和?13CDIC的昼夜变化明显偏小,而在沉水植物(轮藻为主)大量生长的中游水池,水的DO、pH、SIC(方解石饱和指数)和?13CDIC在白天呈逐渐增加趋势,而在夜间逐渐降低,与水生生物的新陈代谢进程(白天以光合作用为主,晚上以呼吸作用占优势)相一致;另一方面,水的EC、3HCO?、Ca2+和p(CO2)(二氧化碳分压)呈现相反的变化趋势,即白天下降,晚上上升。计算得到中游水池因类似海洋"生物碳泵"效应固定下来的有机碳通量达到336 t C/(a·km2),是海洋的51倍,表明陆地水生生态系统应该作为"遗失碳汇"的一个重要方面继续进行研究。Whether carbonate weathering could form stable and durable carbon sink or not depends mainly on the efficiency of the utilization of dissolved inorganic carbon （DIC） by aquatic phototrophs. The latter can be investigated by determing the diurnal variations in hydrochemistry and stable carbon isotope composition of DIC （δ13CDIC） in surface waters. In this research, four parameters, including water temperature, pH value, electrical conductivity （EC） and dissolved oxygen （DO）, were synchronously monitored with high resolution （an interval of 15 min.） from 10： 00, 27th Jan. to 16： 00, 28th Jan. （30-hour period） at the spring, midstream pond, and downstream pond at Laqiao, Maolan, SW China. In addition, δ13CDIC values were sampled and analyzed at an interval of 2 hours in daytime and 4 hours in nighttime. Moreover, a static floating chamber was placed on the water surface to obtain CO2 exchange flux between atmosphere and water to evaluate the biological carbon pump effect with the hydrochemical change. The results show that diurnal changes in hydrochemical characteristics andδ13CDIC values at the spring and downstream pond where few submerged plants developed were much smaller than those at the midstream pond where submerged plants （dominated by Chara Fragilis） flourished. DO, pH, SIC （saturation index of calcite） andδ13CDIC values in the midstream pond show the largest increase in daytime while the largest decrease happened during the nighttime, which had synchronous change with the process of aquatic metabolism （photosynthesis dominated in daytime while respiration dominated in nighttime）. On the other hand, EC, [ 3HCO-], [Ca2＋] and p（CO2） （CO2 partial pressure） showed the inverse variations. The calculated biological carbon pump flux in the middle pond was 336 t C/（a·km2） which was about 50 times higher than that in the ocean, indicating that the carbon fixation in terrestrial freshwater ecosystems may need to be considered as an important part of the miss

关 键 词：岩溶水 水化学 碳同位素 昼夜变化 水生光合生物 生物碳泵效应 

分 类 号：P593[天文地球—地球化学]