摘要
对陕西渭南１２．６ｍ黄土剖面做了２３５个样品有机碳（ＴＯＣ）、有机硫（ＴＯＳ）及岩石有机质快速评价仪（Ｒｏｃｋ－ｅｖａｌ）热解分析。ＴＯＣ的含量在黄土层（Ｌ_１和Ｌ_２的顶部）为０．０４％－０．４５％，古土壤层（Ｓ_０和Ｓ_１）为０．０５％－０．６４％，它随深度呈周期性变化，在古土壤层中含量较高，特别是在古土壤层向黄土层转变的界面上明显增高。黄土中的干酩根最高热解峰温度（Ｔ_（ｍａｘ））主要分布在５２５℃，古土壤的主要在４７５℃。引入大气物理学中测量湿度的比湿概念，根据模拟实验结果，将干酪根不同温度的热解烃，划分为与下降水有关的以低等生物为主的热解烃（ｐＨＣ_（２－１））、以高等生物为主的热解烃（ｐＨＣ_（２－２））和与蒸发作用有关的次生碳酸盐包裹烃（ｐＨＣ_（２－３）），提出计算黄土地区第四纪古湿度公式Ｑｑ＝（ｐＨＣ_（２－１）＋ｐＨＣ_（２－２））／ｐＨＣ_（２－１）＋ｐＨＣ_（２－２）＋ｐＨＣ_（２－３））。经计算该剖面由下而上湿度分别为Ｌ_２＜６０％，Ｓ_１为５５％－７５％，Ｌ_１为４５％－６３％，Ｓ_０为５５％－７２％，以及现今尚处于较湿周期的总趋势。
To understand the trend of the humidity evolution since 0.14Ma, the TOC and TOS have been determined and the pyrolysis of the organic matter is carried out by means of Rock-Eval for 235 samples (contained 113 loess and 122 paleosol samples)in 12.6m loess section of Weinan, Shanxi Province of China. The content of TOS is equal to or less than 0.008%, so it has not been discussed in this paper. The TOC content is 0.04%-0.64% in the section(0.04%-0.45% in the loess layer and 0.05%-0.64% in the paleosol layer). The TOC content is higher in paleosols than in the adjacent loess, especially in the intersurface between paleosol and loess layer. The main peak in Tmax frequency is distributed in 435-475℃ for paleosols and in 500-525℃ for loess. According to measurement results of a lot of nature and synthetic samples, the organic matter with Tmax of 435-450 is derived from bacteria or other lower organism and one with Tmax of 450-500℃ derived from higher plant or mixture of higher plant and lower organism, which is correlated to supergene water, including rain and other surface water and we called these pyrolysis hydrocarbon as pHC_(2-1) and pHC_(2-2) respectively. The organic matteer with Tmax of 500-600℃is mainly from inclusional organic matter in special secondary carbonate, which is correlated to evaporation and called as PHC_(2-3) The“specific humidity”concept from atmosphysics has been introduced, and the quaternary specific humidity fomula is that Q_q= (pHC_(2-1) +pHC_(2-2))/(pHC_(2-1)+PHC_(2-2) +PHC_(2-3)). According to the Q_qCalculation fomula, the variation of humidity is obtained, that is,<60% in L2, 55%-75% in S_1,45%-61% in L_1 and 58%-73% in S_0 of the profile and now the evolution trend of the humidity is in more moist in loess area.
出处
《地球化学》
CAS
CSCD
北大核心
1995年第C00期66-74,共9页
Geochimica
基金
国家自然科学基金
有机地球化学国家重点实验室资助
