我国亚热带季风气候区湿地土壤DOC分布特征和吸附特性研究
发布时间：2019-01-05 09:36
【摘要】：湿地碳循环中,土壤有机碳不仅能转化为气体形式(CO2、CH4)直接释放到大气中,也能够以水溶物形式即可溶性有机碳(DOC),被地表径流携带进入水体,构成碳循环的另一重要环节。目前关于湿地碳循环的研究主要集中在CO2与CH4的排放规律,对于DOC在湿地土壤中的迁移转化则少有关注。本文选取中国亚热带季风气候区的三种典型湿地(城市次生湿地-杭州西溪湿地、湖泊滩涂湿地-湖州下渚湖湿地、人工湿地-余杭区径山水稻田)作为研究对象。通过野外采样分析观测湿地土壤DOC含量的分布特征；通过实验室常规吸附模拟实验,得出较短时间尺度上湿地土壤对DOC的吸附特性；借助多种表征手段,进一步揭示湿地土壤对DOC的吸附机理。研究结果表明：1、土壤DOC的含量变化范围在125.72～512.92 mg·kg-1之间,平均含量为269.72±119.01mg·kg-1,约占TOC平均含量的2%,含量较为丰富。其在土壤剖面中的分布整体呈现出随土层深度增加而降低的趋势。三种湿地DOC平均含量的大小顺序为：水稻田城市次生湿地湖泊滩涂湿地。土壤理化性质对DOC的分布有一定影响。土壤TOC作为DOC的来源,其含量与DOC含量呈极显著正相关；高含水率的土壤有利于DOC的产生与积累；土壤全氮、碱解氮与DOC三者之间存在协同促进关系。通径分析结果表明：TOC和碱解氮是影响DOC含量分布的两个相对重要因素,其中TOC的直接影响更大。2、当吸附质初始浓度介于0～45 mg·1-1范围内时：IM isotherm、Freundlich、 Temkin三种等温吸附模型都能较好的拟合吸附过程,其中IM isotherm方程的拟合效果最佳。IM isotherm方程中的分配系数m可反映吸附能力强弱,m值越大,吸附能力越强,各采样点底层土壤均表现出最强的吸附能力。水稻田与城市次生湿地土壤的吸附能力相近,强于湖泊滩涂湿地。土壤吸附DOC的能力受多变量共同影响,其主控因素为土壤pH值、物理性粘粒和活性铝含量,而土壤TOC、活性铁及含水率等因子对吸附过程影响不显著。3、扫描电镜和比表面积分析表明土壤表面的孔隙结构是决定土壤吸附能力的关键因素,孔隙越多,比表面积越大,比表面能越大,对DOC的吸附能力就越强,进而推测土壤吸附DOC过程存在物理吸附机制。傅里叶-红外测试证实了化学吸附机制的存在,即DOC与土壤矿物羟基之间的配位体交换作用。颗粒物中的脂肪族或芳香族等大分子有机物可能不利于吸附过程的进行。
[Abstract]:In wetland carbon cycle, soil organic carbon can not only be transformed into gas form (CO2,CH4), but also be transported into water by surface runoff in the form of soluble organic carbon (DOC),). Another important part of the carbon cycle. At present, the study on the carbon cycle of wetland is mainly focused on the emission of CO2 and CH4, but little attention has been paid to the migration and transformation of DOC in wetland soil. In this paper, three typical wetlands (urban secondary wetland-Hangzhou Xixi wetland, lake beach wetland-Huzhou Xizhu lake wetland, artificial wetland-Jingshan paddy field) in the subtropical monsoon climate region of China are selected as the research objects. The distribution characteristics of DOC content in wetland soil were observed by field sampling analysis, and the adsorption characteristics of DOC to wetland soil on a short time scale were obtained by conventional adsorption simulation experiment in laboratory. The mechanism of DOC adsorption on wetland soil was further revealed by various characterization methods. The results showed that: 1. The content of DOC in soil ranged from 125.72 to 512.92 mg kg-1, and the average content of DOC was 269.72 卤119.01mg kg-1, which was about 2% of the average content of TOC. Its distribution in soil profile decreased with the increase of soil depth. The order of average DOC content of the three kinds of wetland is: the secondary wetland lake tidal flat wetland in paddy field city. The physical and chemical properties of soil have a certain effect on the distribution of DOC. As a source of DOC, soil TOC content was significantly positively correlated with DOC content; soil with high moisture content was conducive to the production and accumulation of DOC; and there was a synergistic promotion relationship among soil total nitrogen, alkali-hydrolyzed nitrogen and DOC. Path analysis results show that TOC and alkali-hydrolyzed nitrogen are two relative important factors affecting the distribution of DOC content, among which the direct influence of TOC is greater. 2. When the initial concentration of adsorbate is in the range of 0 ~ 45 mg 1-1: IM isotherm,Freundlich, The three isothermal adsorption models of Temkin can fit the adsorption process well. The best fitting effect of IM isotherm equation is that the partition coefficient m of. IM isotherm equation can reflect the strength of adsorption ability, the larger the value of m, the stronger the adsorption ability. The bottom soil of each sampling point showed the strongest adsorption ability. The sorption capacity of paddy field and urban secondary wetland is similar, which is stronger than that of lake beach wetland. The ability of soil to adsorb DOC is affected by many variables. The main controlling factors are soil pH value, physical clay and active aluminum content, but the factors such as soil TOC, active iron and moisture content have no significant effect on the adsorption process. 3. SEM and surface area analysis showed that the pore structure of soil surface was the key factor to determine the adsorption ability of soil. The more pores, the larger specific surface area and specific surface energy, the stronger the adsorption capacity of DOC was. Furthermore, the physical adsorption mechanism of soil adsorption DOC was inferred. The existence of chemical adsorption mechanism was confirmed by Fourier transform infrared spectroscopy (FTIR), that is, ligand exchange between DOC and soil mineral hydroxyl groups. Macromolecular organic compounds such as aliphatic or aromatic compounds in particulate matter may not be conducive to the adsorption process.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53
本文编号：2401585
[Abstract]:In wetland carbon cycle, soil organic carbon can not only be transformed into gas form (CO2,CH4), but also be transported into water by surface runoff in the form of soluble organic carbon (DOC),). Another important part of the carbon cycle. At present, the study on the carbon cycle of wetland is mainly focused on the emission of CO2 and CH4, but little attention has been paid to the migration and transformation of DOC in wetland soil. In this paper, three typical wetlands (urban secondary wetland-Hangzhou Xixi wetland, lake beach wetland-Huzhou Xizhu lake wetland, artificial wetland-Jingshan paddy field) in the subtropical monsoon climate region of China are selected as the research objects. The distribution characteristics of DOC content in wetland soil were observed by field sampling analysis, and the adsorption characteristics of DOC to wetland soil on a short time scale were obtained by conventional adsorption simulation experiment in laboratory. The mechanism of DOC adsorption on wetland soil was further revealed by various characterization methods. The results showed that: 1. The content of DOC in soil ranged from 125.72 to 512.92 mg kg-1, and the average content of DOC was 269.72 卤119.01mg kg-1, which was about 2% of the average content of TOC. Its distribution in soil profile decreased with the increase of soil depth. The order of average DOC content of the three kinds of wetland is: the secondary wetland lake tidal flat wetland in paddy field city. The physical and chemical properties of soil have a certain effect on the distribution of DOC. As a source of DOC, soil TOC content was significantly positively correlated with DOC content; soil with high moisture content was conducive to the production and accumulation of DOC; and there was a synergistic promotion relationship among soil total nitrogen, alkali-hydrolyzed nitrogen and DOC. Path analysis results show that TOC and alkali-hydrolyzed nitrogen are two relative important factors affecting the distribution of DOC content, among which the direct influence of TOC is greater. 2. When the initial concentration of adsorbate is in the range of 0 ~ 45 mg 1-1: IM isotherm,Freundlich, The three isothermal adsorption models of Temkin can fit the adsorption process well. The best fitting effect of IM isotherm equation is that the partition coefficient m of. IM isotherm equation can reflect the strength of adsorption ability, the larger the value of m, the stronger the adsorption ability. The bottom soil of each sampling point showed the strongest adsorption ability. The sorption capacity of paddy field and urban secondary wetland is similar, which is stronger than that of lake beach wetland. The ability of soil to adsorb DOC is affected by many variables. The main controlling factors are soil pH value, physical clay and active aluminum content, but the factors such as soil TOC, active iron and moisture content have no significant effect on the adsorption process. 3. SEM and surface area analysis showed that the pore structure of soil surface was the key factor to determine the adsorption ability of soil. The more pores, the larger specific surface area and specific surface energy, the stronger the adsorption capacity of DOC was. Furthermore, the physical adsorption mechanism of soil adsorption DOC was inferred. The existence of chemical adsorption mechanism was confirmed by Fourier transform infrared spectroscopy (FTIR), that is, ligand exchange between DOC and soil mineral hydroxyl groups. Macromolecular organic compounds such as aliphatic or aromatic compounds in particulate matter may not be conducive to the adsorption process.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53
【参考文献】
相关期刊论文 前5条
1 许端平,李发生,曹云者,谷庆宝,王婉华;典型土壤组分及其与丁草胺除草剂作用的红外光谱研究[J];环境科学研究;2005年04期
2 李太魁;王小国;朱波;;紫色土可溶性有机碳的吸附-解吸特征[J];农业环境科学学报;2012年04期
3 董洪芳;于君宝;管博;;黄河三角洲碱蓬湿地土壤有机碳及其组分分布特征[J];环境科学;2013年01期
4 王晶苑;张心昱;温学发;王绍强;王辉民;;氮沉降对森林土壤有机质和凋落物分解的影响及其微生物学机制[J];生态学报;2013年05期
5 P.ROYCHAND;P.MARSCHNER;;Respiration and Sorption of Water-Extractable Organic Carbon as Affected by Addition of Ca~(2+),Isolated Clay or Clay-Rich Subsoil to Sand[J];Pedosphere;2014年01期
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