新疆阿尔泰山不同泥炭地记录的全新世大气粉尘信息及其影响因素

Holocene atmospheric dust record and its influencing factors from different peatlands in the Altay Mountains of Xinjiang

本文以中国西北阿尔泰山铁力沙汗和哈拉萨孜泥炭地为研究对象,结合AMS^(14)C年代框架,高分辨率测定两处泥炭地柱芯中的微量元素和常量元素,分析中国西北高山区泥炭记录的全新世大气粉尘历史沉降过程及其影响因素。研究发现:铁力沙汗和哈拉萨孜记录的全新世大气粉尘通量分别为22.74~76.92 g/(m^(2)·a)和18.60~198.38 g/(m^(2)·a)。与铁力沙汗相比,哈拉萨孜泥炭中矿物元素主要来源于大气沉降,表现为早全新世和早−中全新世时期粉尘通量较高,中全新世后粉尘通量较低,更能代表区域粉尘活动历史变化。阿尔泰地区泥炭记录的全新世粉尘通量高于季风区,且在中全新世后通量下降的特征,与季风区泥炭记录的高粉尘通量的结论相反。粉尘来源和气候环境是导致不同区域粉尘通量变化存在差异的主要原因。中国西北干旱区粉尘源区的湿度和温度通过影响植被覆盖状况,对区域大气沉降过程产生影响,但局地环境和冻土变化差异,也会导致区域内不同载体记录的大气粉尘信息存在明显差异。本研究对更全面更准确地认识区域大气环境变化过程及其主要影响因素,具有科学意义。

In this article,we selected Tielishahan peatland and Halasazi peatland in the Altay Mountains,Northwest China as the research objects.We used AMS^(14)C to establish a dating framework and determined trace and macronutrient contents in two peat cores to reconstruct the historical Holocene atmospheric dust deposition process and its influencing factors in high mountainous areas in Northwest China.The results show that atmospheric dust deposition fluxes recorded from Tielishahan and Halasazi peat cores ranged from 22.74 to 76.92 and 18.60 to 198.38 g/(m^(2)·a),respectively.Atmospheric deposition is the main source of mineral element and water recharge in the Halasazi peatlands,which is more representative of the changes in dust activity in the region.The dust fluxes recorded in the Halasazi peat show higher dust fluxes during the early Holocene and early-middle Holocene periods and lower dust fluxes after the middle Holocene.Compared with other regions,the Holocene dust fluxes from the peat record in the Altay region were higher than those from the peat record in the monsoon region.A decreasing trend observed in the Altay region after the middle Holocene,contrary to the conclusion that the peat records of the monsoon region which showed higher dust fluxes in the late Holocene.The dust sources and the characteristics of the climatic environment were the main reasons for the differences in dust flux variation processes in different regions.Humidity and temperature variations directly affect the vegetation cover status in the dust source area of the northwest arid zone of China,and further affect the variation of atmospheric dust fluxes in the region.However,differences in local environmental and permafrost variation can also cause significant differences in the atmospheric dust information recorded by different environmental carriers.This study is of great scientific significance for a more comprehensive and accurate understanding of the atmospheric environmental change processes and their main influencing factors in different regions of China.