西藏几种土壤有机无机复合状况及其热性质的研究

ORGANO-MINERAL COMPLEX STATUS ANDITS PYROLYTIC CHARACTERISTICS OFSEVERAL SOILS IN TIBET

在西藏七种土壤结合态腐殖质分组测定的基础上，进行了相应不同有机无机复合体的差热（ＤＴＡ）和热重（ＴＧ）分析，结果表明：供试土壤的有机无机复合度普遍较低，复合碳中松结态和紧结态相对占有优势。土壤原样及其不同结合形态有机无机复合体在３１０℃和４３０℃左右均有一放热峰，部分土样在５７０℃左右出现另一放热峰，相应于各放热峰伴有失重。综合ＤＴＡ、ＴＧ分析以及有机质分组测定结果得出：与土壤矿物呈稳结态与紧结态复合的有机质是３１０℃左右放热峰的主导因子；松结态有机质主要在４３０℃左右分解；未形成复合体的轻组有机质则在５１０℃附近分解。土类之间的比较表明：在高山或亚高山草原植被下形成的莎嘎土或巴嘎土的有机质热解焓值大于在高山或亚高山草甸植被下形成的草毡土或黑毡土的有机质热解焓值。

he thermal analyses (DTA and TG)of various organo-mineral complexes inseven soil types of Tibet were carried out based on the fractionation and assessmentof soil organic matter.The results sLow that the degree of organo-mineral complex-ation in the test soils was lower.Tlie loosely conibined carbon and tightly combinedcarbon occupied a relatively dominant position in total coiiiplexed carbon.Exothermicpeaks were found at about 310℃ and 430℃ for original soil samples and its varionsorgano-mineral complexes- Another exothermic peak at 510℃ existed in a few soilsainples in the study.An obvious-weight loss followed each exothermic peak.Fromthe results of the thermal analyses (DTA and TG) and the fractionation and asses-sment of organic matter in the soils discussed,it can be concluded that the heavyfraction of organic matter stably and tightly combined with soil mineral particles wasthe dominant factor of the exothermic peak at 310℃,the loosely combined organicmatter was pyrolyzed at about 430℃,and the light fraction of organic matter whichdid not complex with soil minerals was pyrolyzed at about 510 ℃.The results alsoindicated that the pyrolytic enthalpy changes (△H) of organic matter in the alpinesteppe soil and subalpine steppe soil were greater than tliose in the alpine meadowsoil and subalpine ineadow soil respectively.