中国新疆博斯腾湖现代碳库效应研究

The effects of modern 14 C pool in Lake Bosten,Xinjiang,China

碳库效应存在影响了14 C测年的准确性,制约了沉积物在湖泊研究中的应用。本文研究位于典型西风环流带的新疆博斯腾湖现代碳库效应,结合同位素地球化学、水化学等方法,探讨了博斯腾湖碳库效应的影响机制。研究结果表明,博斯腾湖最大现代碳库年龄为3535年,最小为现代碳,集中在670~945年。而过去碳库效应集中在1033~2200年。深水区表现为碳库年龄较小且稳定;在入湖口碳库效应最大,富水生植物浅水区碳库效应最小。与过去碳库年龄相比较,现代碳库效应整体表现更为年轻。研究发现,博斯腾湖口受流域外源“死”碳影响,深水区受湖水与大气CO_(2)交换率差异影响,富水生植物浅水区可能受水生植物光合作用影响。此外,核爆效应也对博斯腾湖现代碳库效应产生了影响,可能导致最高约1000年的年代误差。利用深水区放射性碳比活度(pMC)平均值与大气碳比活度差值(~18%),得出深水区沉积物存在约846年现代碳库效应,再经核爆效应校正后得出博斯腾湖存在最高约1800年碳库效应。

The effects of 14 C pool are highly concerned because it affects the accuracy of 14 C dating that limits the use of sediment in lake studies.However,the 14 C cycling mechanisms are still debating,largely due to a lack of investigation into the effects of modern 14 C pool.Lake Bosten in Xinjiang,situated in a typical westerly circulation zone,has high sediment concentration,and is an ideal location to study this issue due to its significant effect of 14 C pool.However,previous studies on Lake Bosten mainly focused on past effects of 14 C pool,heavily influenced by sediment processes.This study aimed to investigate the effect of modern 14 C pool for typical surface sediments of freshwater in Lake Bosten.By combining 14 C dating results with isotopic geochemistry,hydrochemistry,and other methods,the study determined that the maximum modern carbon pool age in Lake Bosten was 3535 years,and the minimum was 670-945 years.Past carbon pool effects were concentrated between 1033-2200 years.The deepwater area exhibited a smaller and more stable carbon pool age,while the carbon pool effect was highest in the lake inlet and lowest in the shallow water area with abundant aquatic plants.Compared with the past carbon pool age,the modern carbon pool effect was generally younger.The study found that the Lake Bosten inlet was influenced by external"dead"carbon,the deepwater area was impacted by differences in the exchange rate of lake water and atmospheric CO_(2),and the shallow water area with abundant aquatic plants may be affected by photosynthesis of aquatic plants.Additionally,nuclear explosion effects also influenced the modern carbon pool effect of Lake Bosten,leading to a potential age error of approximately 1000 years.Finally,by correcting the difference between the average pMC value of the deepwater area and the atmospheric carbon activity(about 18%),the study determined that the deepwater sediment in Lake Bosten has a modern carbon pool effect of about 846 years,which was further corrected for nuclear explosion effects to determine that the highest 14 C pool effect in Lake Bosten is about 1800 years.