【作者】 唐东民；

【导师】 伍钧； 陈华林；

【作者基本信息】 四川农业大学 ， 环境工程， 2008， 硕士

【摘要】 溶解性有机质（dissolved organic matter,DOM）,亦称水溶性有机质,主要是指能够溶解于水、酸或碱溶液中的有机质,如天然水中的有机质、土壤溶液中的有机质、土壤和有机肥中能被水、酸或碱等浸提的有机质。其操作上定义为能通过0.45μm滤膜的有机质。由于其水溶性特点,DOM被认为是陆地生态系统和水生生态系统中一种重要的、非常活跃的化学组分,是土壤圈与相关圈层物质交换的重要形式,影响着成土过程和营养物质的输送,以及有机污染物质的环境行为特性（如毒性、迁移转化特性以及生物可降解性等）。随着人们对有机污染关注程度的加深,DOM对有机物环境行为的影响研究日益成为土壤学、生态学和环境科学等学科的研究热点。本文以有机物料（水稻秸秆）为DOM来源,研究了其腐解过程中DOM的动态变化。同时,采用完全混合法定量地研究了各腐解阶段DOM对除草剂（苄嘧磺隆,BSM）和多环芳烃（芘,PYR）在土壤中吸附解吸行为的影响,并探讨了影响机理。得到以下主要结论:（1）采用化学分析、XAD-8树脂分组等方法研究了水稻秸秆分解过程中产生DOM的组成性质变化特征。结果表明,有机物料分解期间溶出DOM的含量与化学组成是一个动态变化的过程。在有机物料分解的初期阶段,有机物料自身溶出的水溶性物质等是DOM的主要来源,此时DOM组成以碳水化合物和有机酸为主,表现出较强的亲水性。随着秸秆进一步腐解,半纤维素、纤维素的分解产物成为DOM的主要来源,此时DOM组成主要是分子量大、芳香性较强的物质,表现出很强的疏水性。秸秆分解91天后,DOC、DON、水溶性糖、溶解性酚酸都趋于稳定,但DOM各组分的含量仍处于变化中。通过相关性分析发现,不同指标之间存在一定的相关性,其中溶解性碳与溶解性酚酸、胡敏酸（HA）呈显著正相关,与富里酸（FA）呈显著负相关,溶解性糖与亲水组分呈正相关,溶解性酚酸与胡敏酸呈极显著正相关,胡敏酸与疏水组分、富里酸与亲水组分分别呈极显著正相关。（2）采用特征波段扫描和红外光谱分析研究了DOM的光学性质及其结构特征的变化,结构表明,随着秸秆腐解的不断进行,提取的DOM其ΔlogK先上升后下降,而A₂₈₀值、A₂₅₄值和E₄/E₆升高,表明DOM氧化程度和芳香性增强,脂族性降低,分子结构向复杂化方向转变,分子量增大。DOM的羧基、羰基和酚羟基含量增加,甲氧基和醇羟基含量降低,富含酸性解离基的暗色高分子在不断生成。同时,DOM中可提取的HA比例（PQ）上升,FA的最初形成速度大于HA,随着培养时间延长,FA转化为HA。从红外光谱可见,不同阶段得到的DOM本身含有的官能团组成是相似的。主要包括:甲基、亚甲基、次甲基、羟基、羧基、酰胺基和苯环等;化合物的组成主要为:碳水化合物、糖类、脂肪族有机酸、芳香族有机酸、醇类、酰胺化合物和酚类化合物。（3）BSM和PYR的吸附.解吸作用存在两段行为,即快速吸附-解吸阶段和慢速吸附-解吸阶段,8h内能基本达到吸附-解吸平衡。同时,线性方程和Freundilch方程能很好地描述BSM和PYR在土壤中的吸附解吸行为,BSM和PYR存在解吸迟滞现象,解吸并不完全是吸附的可逆过程,这二者存在不同的机制。（4）DOM的加入抑制了土壤对BSM和PYR吸附作用,却促进了BSM和PYR的解吸。但不同阶段DOM产生的抑制和促进效应不一样,各阶段的DOM之间所产生的抑制和促进效应存在显著差异（p＜0.05）。总体上,DOM对BSM抑制或促进效应均随着秸秆腐解时间的延长而减弱;而DOM对PYR抑制或促进效应均随着秸秆腐解时间的延长而增强,这种效应是多种因素共同作用的结果,其中亲水组分-疏水组分和富里酸.胡敏算起着重要作用。亲水组分和富里酸在BSM的吸附解吸中起主要作用,而疏水组分和胡敏酸在PYR的吸附解吸中起主要作用。更多还原

【Abstract】 Dissolved organic matter（DOM）,also called water suluable organic matter,is defined as it can be extracted by water,acid and alkali,like organic matter in water,soil solution and organic materials.The operation definiation of DOM is defined through filtration,the size limit,which is used to differentiate DOM from particulate organic matter,is somewhat arbitrary,but there is an almost universal consensus that it is around 0.45μm.In the past 20 years,much progress has been made in the understanding of DOM functions in terrestrial and aquatic ecosystems.In the presence of DOM,weathering rates can be accelerated,and DOM plays a central role during podsolisation.Furthermore,DOM contains organically bound nutrients such as N,P and S,and DOM dynamics will therefore also affect their mobility and availability.Today,it is commonly acknowledged that DOM can affect the solubility,biodegradation and mobility of organic compounds and thus contributes to pollutant transport or to micronutrient availability.For more attention was payed to organic pollutants,studying the relationship between DOM and organic pollutants will be the frontier of soil science,ecology and environment science.The dynamics of DOM derived from various stages of crop straw decomposition have been studied in this research,its effects on the sorption-desorption behavior of two probe organic pollutants in soil had also been studied,one is herbicide（Bensulfuron-methyl,BSM）and the other is polycyclic aromatic hydrocarbons（Pyrene,PYR）.The main results as follows:（1）The dynamic changes of DOM derived from crop straw decomposition was studied by using chemical analysis and XAD-8 resin.The results showed that the content and constituents of DOM was in dynamic changes at all the incubation stages.At the initial decomposition stages,the DOM orignated from water-dissolved matter derived from organic materials,temperately,the primary composition of DOM was carbonhydrates and micromolecular organic acid,its hydrophile was a little strong.With crop straw incubation time prolonged,the DOM was origanted from the product of cellulose and hemicellulose decomposition.Temperately,the DOM was macromolecular matter,its aromaticity and hydrophobic nature increased.The DOC,dissolved nitrogen,dissolved sugar and phenol acid increased gradually until constant after 91 days’ incubation,but the compositions were still changing.The correlation annlysis among the different index was carried out. The results showed that:DOC was positive correlated to DPC and HA,and negative correlated to FA significantly at 0.05 level respectively.Dissolved sugar was positive correlated to hydrophilic fraction.DPC was positive correlated to HA significantly at 0.01 level.HA was positive correlated to hydrophobic fraction,and FA was negative correlated to hydrophilic fraction significantly at 0.01 level respectively.（2）The dynamical changes of optical property and structure characteristics of DOM by using wave scanning and Frourier Transform Infra Spectroscopy（FTIR）.During the crop straw decomposition,the△logK value increased at first,then decreased,while A₂₈₀、A₂₅₄and E₄/E₆ increased,which indicated that the aromaticity and oxidation degree of DOM increased,their molecular structure became less aliphatic and more complex.The content of carboxyl,carbonnyl phenol hydroxyl increased,methoxy and methanol hydroxyl decreased.The propotion of HA in DOM（PQ value）gradually increased, indicating that FA took up formation faster than HA in the initial stage of incubation.With prolonged incubation,FA transformed into HA.Frourier Transform Infra Spectroscopy indicated that the DOM derived from crop straw decomposition had siminar structure characteristics,such as methyl,methylene,methine,carboxyl,hydroxyl et al.The compounds in DOM were saccharide,aliphatic and aromatic organic acid,hydroxybenzene et al..（4）Sorption of model pollutants in soil was biphasic,a fast sorption phase followed by a slow sorption phase.The equilibrium reached in 8 hours.Likewise,desorption were biphasic,too,containing a fast phase no more than 8 hours,in which a small portion model pollution adsorbed in soil desorbed into aqueous phase quikly,however,the other portion seemed to be resistant to desorption.It was found that the sorption-desorption hystersis of soil was statistically significant.（5）The Freundlich and linear model can comletely explained the mechanism of BSM and PYR sorption and desorption.Within the selected concentration range of the BSM, PYR and DOM in this study,the sorption capacity of soil BSM and PYR reduced significantly after applying DOM into soil,which derived from different decomposing stages.Fuetheremore,there is significant difference（p＜0.01）comparing to control treatment（i.e.,no DOM in sorption-desorption course）.The effects of DOM on the sorption capacity of soil BSM were weakened with longer DOM compositon time,but the sorption capacity of soil PYR was reverse to BSM.The hysteresis index（HI）value was much lower and was not statistically significant comparing with control treatment after adding DOM. The DOM accelerated desorption of soil BSM.The restraint and accelaration effects were caused by comprehensive factors.The hydrophilic fraction and fulvic acid palyed the primary role on the BSM sorption-desorption,while hydrophobic fraction and humic acid palyed the primary role on the PYR sorption-desorption.This research was important to direct the reasonable application of organic fertilizer.更多还原