摘要
从过程考虑,腐殖质的形成和转化主要是微生物主导的生物化学过程,但就其始态和终态的能量水平变化而言,是热力学稳定性问题。在土壤中,影响腐殖质的形成转化的因素很多,如黏粒含量和类型,植被和微生物状况,土壤湿度、温度和空气组成,土壤溶液的化学组成、浓度、酸度和氧化还原状况等。但从热力学角度,为了计算反应平衡常数(logKR)和吉普斯生成自由能(ΔGfθ),如果将温度设为25℃,我们可以将土壤条件诸多因素简化为水活度([H2O])、氧分压(PO2)和二氧化碳分压(PCO2)这3个参数。之所以简化为这3个参数,因为任何有机成分均是由含有这3种元素的物质形成的,最终又均可以分解为含有这3种元素的H2O和CO2。本文按照上述新思路,以黑土为例探讨了胡敏酸(HA)、富里酸(FA)形成转化的驱动因素和热力学稳定性的研究方法,用元素组成-土壤条件参数法计算HA、FA的logKR和ΔGfθ及热力学稳定性范围。同时通过土壤添加有机物料的模拟培养实验研究了氧气和二氧化碳等单因素对HA和FA数量积累的影响。结果表明,黑土HA和FA的元素组成分子式分别为nC21H21O9N和nC24H33O17N。FA在缺氧、多水和高浓度二氧化碳条件下较稳定;HA则相反。培养实验中,高二氧化碳和低氧气浓度处理使FA与HA的相对比例增加。这一研究方法和结果将有助于解释和推测土壤腐殖质组成的空间变异规律,指导土壤肥力、土壤固碳的调控实践。
From the aspect of process, formation and transformation of humus are essentially microbe-based biochemical processes, while from that of difference in energy level between the initial and final stages, these processes could also be considered as an issue of the thermodynamic stability. In the soil there are quite a number of factors affecting these processes, such as type and content of clays, vegetation, microorganisms, soil moisture, temperature, air composition, chemical composition and concentration of soil solution, acidity, status of redox, etc. But from the angle of thermodynamics, in order to calculate reaction equilibrium constant （ logKR） and Gibbs energies （ΔGf^θ） at a given temperature of 25℃, those soil conditions could be simplified into 3 parameters： water activity （[ H2O ] ）, oxygen partial pressure （Po2） and carbon dioxide partial pressure （Pco2）, since all organic substances are composed of these three elements and would eventually be decomposed into H2O and CO2 that contain these three elements. According to this new idea and principle mentioned above, this paper cited black soil as an example to explore approaches to the study on factors driving formation and transformation and thermodynamic stability of HA and FA, and to the calculation of ΔGf^θ, logKR and range of thermo- dynamic stability of HA and FA with ＂the elemental composition-soil condition parameter method＂. Meanwhile, a simulated incubation in the lab of soil with organic matter was conducted to study effect of mono-environmental factors like O2 and CO2 on accumulation of HA and FA. Results show that the molecular formula of HA and FA is nC21H21OΦN and nC24H33 O17N, respectively. In soils low in O2, high in moisture and high in CO2 concentration, FA was relatively stable whereas HA was on the contrary. In the incubation experiment, high CO2 concentration and low O2 concentration would result in higher FA/HA ratio. This method and the findings in this study could help explain and speculate the rule of spatial variability of the composition of soil humus, and provide guidance to regulation of soil fertility and soil carbon sequestration.
出处
《土壤学报》
CAS
CSCD
北大核心
2010年第1期71-76,共6页
Acta Pedologica Sinica
基金
国家自然科学基金项目(40271069
40471076
40871107)
高校博士点基金项目(20040193002)资助
关键词
氧浓度
二氧化碳浓度
水活度
胡敏酸
富里酸
热力学稳定性
O2concentration
CO2 concentration
Water activity
Humic acid
Fulvic acid
Thermodynamic stability
作者简介
窦森（1959-），男，吉林人，教授，主要从事土壤有机质研究。E-mail：dousen@tom．com
