Temperature-induced fractionation of oxygen isotopes of diatom frustules and growth water in Lake Sihailongwan in Northeast China
Temperature-induced fractionation of oxygen isotopes of diatom frustules and growth water in Lake Sihailongwan in Northeast China
复制标题
东北四海龙湾硅藻壳和生长水的氧同位素温度诱导分馏
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
Jingtai Han
中科院分区：
文献类型：
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作者：
Dong Li;Jingtai Han
硅藻氧同位素在古气候和古环境的定量重建中得到了广泛的应用，但在国内的报道却很少。本文以东北四海龙湾湖为研究对象，详细研究了生长温度对硅藻体与湖水氧同位素分馏的影响。该研究包括为期2年的多个深度的湖泊水温现场监测，每两周收集浅层和底部深度（分别低于湖面7米和49米）沉积物和水的捕集器，对捕集器沉积物进行硅藻分离和净化，并对硅藻二氧化硅和湖水样品进行氧同位素测量。本文进行的条件实验表明，本研究中使用的实验室设备、方法和技术能够生成硅藻体典型氧同位素组成的可靠数据。结果表明，现代硅藻的氧同位素组成与生长期间的湖泊温度呈显著的线性关系。在3.6 ~ 24℃的温度范围内，分馏系数约为- 0.185‰/°C - 0.238‰/°C，这与不同水生环境和不同硅藻分类群的实验室培养结果一致。这些发现为生长温度对硅藻体与环境水之间氧同位素分馏的主导控制提供了有力的支持。表层和底层硅藻氧同位素的分馏系数存在显著差异，表明不同的沉积过程和埋藏效应影响了表层和底层样品。造成这种差异的另一个因素可能是，蒸发的富集和降雨的稀释对地表的影响更大。综上所述，中国硅藻氧同位素评价取得了重大进展，并引起了人们对表层和底层硅藻氧同位素组成差异的关注。
Diatom oxygen isotopes have been widely applied in quantitative reconstruction of the paleoclimate and paleoenvironment, but have rarely been reported in China. In the present study, Lake Sihailongwan in Northeast China was selected for detailed investigation of oxygen isotopic fractionation between diatom frustules and lake water induced by growth temperature. This study involved a 2-year period of field monitoring of the lake water temperature at multiple depths and biweekly collections of traps for both sediment and water at shallow and bottom depths (7 and 49 m below the lake surface, respectively), diatom separation and purification of the trap sediments, and oxygen isotope measurement for diatom silica and lake water samples. The conditioned experiment conducted herein demonstrated that the laboratory device, methods and techniques used in this study were capable of generating reliable data for the typical oxygen isotope composition of diatom frustules. The data obtained revealed a prominent linear relationship between the oxygen isotope composition of the modern diatom and lake temperature during growth. The fractionation coefficient was about −0.185‰/°C−0.238‰/°C in the temperature range of 3.6–24°C, which is consistent with the observations from various aquatic environments and laboratory culture with different diatom taxa. These findings provide strong support for the dominant control of the growth temperature on the oxygen isotope fractionation between the diatom frustules and ambient water. A notable difference in the fractionation coefficient was observed between the surface and bottom diatom oxygen isotopes, suggesting that various depositional processes and taphonomic effects influenced the surface and bottom trap samples. Another factor leading to this difference may be that enrichment by evaporation and dilution by rainfall have a stronger influence on the surface. Overall, the results presented here demonstrate significant progress in evaluation of diatom oxygen isotopes in China and draw attention to the differences between surface and bottom diatom oxygen isotope compositions.