【作者】 张晶；

【导师】 孙德智；

【作者基本信息】 北京林业大学 ， 生态环境工程， 2012， 博士

【摘要】 湿地土壤中磷的形态分布特征和迁移转化行为对水体富营养化状态和湿地生态功能的发挥具有非常关键的作用,野鸭湖湿地自然保护区是北京地区面积最大的湿地,对保护官厅水库水质、调节气候具有重要作用。本文以野鸭湖湿地为对象,研究了湿地土壤中磷的形态分布特征、土壤对无机磷和有机磷的吸附行为和机理以及室内动态模拟条件下土壤-水界面不同形态磷的转化行为。采用化学连续提取法研究了不同形态磷随土壤深度(0-60cm)分布特征及表层土壤中(0-10cm)磷随植物生长季的形态变化规律,并分析了不同形态磷含量与土壤理化性质的相关性。结果表明,土壤总磷含量在352.3～836.1 mg-kg-1之间,无机磷约占总磷的72.76%,有机磷含量相对较低,约占总磷的27.24%；土壤总磷和大部分形态磷随土壤深度增加呈减少趋势。无机磷中的闭蓄态磷(Oc-P)随土壤深度增加明显降低,可能是与土壤中A1-P和Fe-P发生相互转化的结果,交换态磷(Ex-P)则来源于Oc-P和残渣态磷(Re-P)的分解。表层土壤中总磷和大部分形态磷与植物的生长周期存在密切关系,在植物快速生长期,磷的含量较低,而在植物凋落衰败期,磷含量则较高；表层土壤中Oc-P在植物凋落期明显增加,说明植物凋落物中的磷是表层土壤Oc-P的主要来源；稳定态有机磷是土壤有机磷的主要存在形态(占总有机磷的90.28%),其含量与土壤pH值呈负相关,与含水率和有机质呈显著正相关,而其它形态有机磷与土壤理化性质没有明显相关性,但是高稳定有机磷与其它有机磷之间可以相互转化。核磁共振磷谱分析得出野鸭湖湿地土壤中的磷主要以正磷酸盐和磷酸单酯的形式存在,并证明了土壤中稳定态有机磷主要以磷酸单酯形式存在(占总有机磷的92.98%)。在磷的吸附行为研究中,采用静态吸附和动态吸附柱两种方法,研究了不同环境因素下,土壤-水系统中磷的吸附行为和形态转化规律。静态吸附实验结果表明,土壤对无机磷和植酸的动力学吸附特性符合二级动力学方程;Langmuir交叉型等温式可较好地描述土壤对无机磷、植酸和β甘油磷酸的等温吸附过程；pH对磷吸附的影响表现为,随水体pH值增加,土壤对磷吸附量先缓慢增加后急剧减少,土壤对无机磷、植酸和β甘油磷酸的吸附最适pH在8左右；水体中低浓度有机质促进土壤对磷的吸附,其中有机质浓度为100mmg·L-1时土壤对正磷酸盐和植酸的吸附量较高,有机质浓度为50mg·L-1时则促进土壤对β甘油磷酸盐的吸附。土壤吸附磷后比表面积减小,吸附的磷主要聚集在微孔和中孔：根据吸附滞后环的类型,推断土壤的孔结构是片状离子堆积形成的狭缝孔;SEM-EDS分析得出土壤吸附的磷主要分布在永久电荷和可配位官能团聚集的土壤颗粒凸起部位；FT-IR和XRD分析表明,土壤中高岭石是参与土壤吸附无机磷和有机磷的主要矿物。动态吸附结果表明,上覆水的性质对表层土壤影响较大：除P0外,上壤中Ex-P、A1-P和Fe-P三种活性较高的无机磷随上覆水磷浓度的增加显著增加,而稳定态无机磷Oc-P和Ca-P增加较小;随着上覆水体有机质浓度的增加,土壤中EX-P和Fe-P均有所增加,这是由于有机质的增加促进了土壤中微生物的增殖,进而促进了土壤微生物对水体中磷的吸收；Ex-P、A1-P和Fe-P在灭菌上壤中的含量明显高于未火菌土壤,这是灭菌土壤比表面积较大、微孔较多以及矿物组成发生改变所致。再覆水过程和落干过程改变了土壤吸附磷的行为和土壤中磷的形态,使得再覆水后土壤中Ex-P表现出随上覆水有机质浓度的增加而减少,并且由于原上覆水水质、土壤微生物存活和土壤氧化还原条件的不同,落干后土壤中Ex-P、Al-P、Fe-P和Oc-P表现出不同的变化规律。更多还原

【Abstract】 The distributions and the mobility-transformation of phosphorus (P) fractions in wetland soil play an important role in the water eutrophication and ecological balance of the wetland. Yeyahu wetland natural reserve with the largest area in Beijing is critical to the water quality of Guanting reservoir and climate changes. Thus Yeyahu wetland is selected as the objects. The distribution characteristics of P fractions, the adsorption behaviors and mechanism of the inorganic and organic P, the transformation of P fraction on the soil-water interface under different simulating conditions were investigated.The chemical sequential extraction method was performed in the research of the distribution characteristics of P fractions as the seasonal variations and the soil profile depth. And the mathematical statistical method was used for the correlation analysis between soil properties and P fractions. The results showed that the total P was in the range of 352.3～836.1 mg·kg-1, and the inorganic and organic P accounted for 72.76% and 27.24% of total P, respectively; total P and most of P fractions decreased with the soil profile depths. Occluded P (Oc-P) as the inorganic P fraction showed obvious decrease with soil depth, which was probably due the transformation to the Al-bound P (Al-P) and Fe-bound P (Fe-P), and the exchangeable P (Ex-P) was derived from the decomposition of Oc-P and residual P (Re-P). Total P and most P fractions were significantly correlated with the growth cycle of the vegetations. In the growth period, the concentration of P was lower, while in the litter period, P was much higher. Furthermore, Oc-P in the surface soil was the highest in the litter period, which indicated that P in vegetations was the main source to Oc-P in the soil. The resistant organic P (OP) was the main occurrence of OP in soil, accounting for 90.28% of total OP, and it was negatively correlated with the pH value and positively with water contents and organic matter, however, the other OP fractions were not correlated with soil properties. It also revealed that OP fractions in soil could be interchangeable under particular conditions.The results of the nuclear magnetic resonance (NMR) revealed orth-P and mono-P were the major occurrence of P in Yeyahu wetland soil, and indicated the resistance OP accounting for 92.98% of total OP occurred in the form of mono-P in wetland soil.The behaviors of P and the transformation of P fractions were studied by static adsorption experiments and dynamic adsorption experiments, respectively. The results of the static adsorption revealed that the kinetic adsorption process of inorganic P and phytate could be described by second order kinetic equation; and the isothermal adsorption process of inorganic P, phytate, andβ-glycerophosphate could be well described by Langmuir cross-shaped adsorption isothermal equation. The water pH had an impact on the P adsorption, with the increase of pH, the adsorption capability slowly increased in the beginning, subsequently, the capability decreased sharply. The optimum pH of inorganic P, phytate, andβ-glycerophosphate adsorption were about 8. The adsorption of P could be promoted in the water with lower dissolved organic matter (DOM), the adsorption capabilities of inorganic P and phytate were higher in the water of 100mg·L-1 DOM, while that ofβ-glycerophosphate was higher in the water of 50mg·L-1 DOM; the specific surface area of soil particles decreased after the adsorption, and the absorbed P aggregated in micro- and meso-pore; according to the hysteresis loop of adsorption, the pore structure of soil particles was inferred as slit pore formed by schistose ion accumulation; by the SEM-EDS, the adsorbed P on the soil surface was distributed on the raised part with much more permanent charges and functional groups; the results obtained by FT-IR and XRD indicated that kaolinite in soil participated the adsorption process of inorganic and organic P.The results of dynamic adsorption revealed that the surface soil was readily effected by the properties of the overlying water; Ex-P, Al-P and Fe-P as labile P fractions in soil remarkably increased with the P concentration of overlying water, while the resistant fractions Oc-P and Ca-P increased inconspicuously; with the increase of the DOM in overlying water, Ex-P and Fe-P increased in soil, for the reason that micro-organism multiplied in the situation with sufficient organic matter and absorbed amount of P in overlying water; the contents of Ex-P, Al-P and Fe-P was larger in sterilized soil than that in unsterilized soil due to the greater specific surface area, more micropore and the change of mineral composition of the sterilized soil. The second water-lying and soil drying could influence the absorption behavior of P and the distribution of P fractions. In the second waterlying, the relationship between Ex-P and DOM varied, and Ex-P decrease with the concentration increase of DOM; after soil drying, Ex-P, Al-P, Fe-P and Oc-P in soil showed different variation patterns due to the different former properties of the overlying water, soil micro-organism and soil redox conditions.更多还原