Temperature-induced fractionation of oxygen isotopes of diatom frustules and growth water in Lake Sihailongwan in Northeast China |
| |
Authors: | Dong Li JingTai Han |
| |
Institution: | 1.Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,China |
| |
Abstract: | 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. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|