外源砷在土壤中的老化及其对土壤微生物影响的机理研究

发布时间：2018-01-04 07:15

本文关键词：外源砷在土壤中的老化及其对土壤微生物影响的机理研究　出处：《中国农业大学》2016年博士论文　论文类型：学位论文

【摘要】：砷是自然界中普遍存在的有毒类金属元素,也是我国土壤中含量超标较严重的有毒元素之一。外源砷进入土壤后会随着与土壤胶体相互作用时间的延长出现有效性或毒性降低的现象,即发生老化过程,但目前对外源砷在土壤中的老化过程、影响因素、老化机理及老化过程中土壤微生物群落变化等方面的研究较少。本研究选取了红壤区几种母质发育的土壤和不同区域典型土壤,通过外源添加砷酸钠溶液(五价砷)室内模拟培养试验,系统研究了外源砷进入土壤后有效态砷及各结合态砷含量随老化时间的变化特征,并分析了影响砷老化进程的关键因子。以此为基础,初步构建了外源砷在土壤中老化的半机理模型,并利用野外采集的砷污染土壤进行了验证,明确了外源砷老化过程中起主导作用的老化机理。同时,应用高通量测序技术系统研究了上述土壤中理化性质差异较大的两种土壤中(黄壤和紫色砂页岩发育的土壤)细菌和古菌群落随砷老化时间的变化,初步探讨了土壤中细菌和古菌在砷胁迫下的群落适应机制。本研究结果,可为正确评价外源砷进入土壤后对生态系统的风险及砷污染农田安全利用等提供理论支撑。主要研究结果如下：1.通过对外源砷在红壤区几种母质发育土壤中老化过程的研究发现,培养期间紫色砂页岩发育的土壤(RS2)中砷的有效性显著高于其它母质发育的土壤。该结果意味着在湖南等砷污染较严重的亚热带地区,该母质发育土壤中砷对农田生态系统的危害和风险均较高。2.对外源砷在不同区域典型土壤中老化过程的研究发现,外源砷进入潮土(FS)和灌漠土(IDS1)后,其有效性始终较高(11.64-71.16%)且老化过程达到近似平衡的时间较长；而在黄壤(YS)和红壤(RS1)中则有效性较低(0.74-31%),老化达到近似平衡的时间较短,表明外源砷在不同类型土壤中的老化过程存在差异。逐步回归结果表明,土壤黏粒含量是决定外源砷老化达到近似平衡所需时间的关键因子。外源砷在不同类型土壤中老化达到近似平衡的时间排序为：褐土(CS)潮土(FS)灌漠土(IDS1)棕壤(BNS2)红壤(RS1)紫色土(PS)黄壤(YS)砖红壤(LS1)。3.准二级动力学方程能较好地拟合外源砷在土壤中有效性的变化过程(R2=0.939-0.999,P0.01)。土壤pH值和铁、铝、锰等氧化物的含量是影响外源砷有效性、控制砷老化速率以及老化达到平衡时土壤有效砷含量的关键因素。进一步分析发现,富含铁铝氧化物的红壤中铝氧化物对老化进程的影响要高于铁氧化物,可能是由于铝氧化物与砷结合可以形成结构更为稳定的双齿双核配合物。4.砷与土壤结合形态的改变直接影响其在土壤中的有效性。研究表明,非专性吸附态砷(F1)和专性吸附态砷(F2)是构成土壤中有效态砷的主要组成部分。随外源砷老化时间的延长,进入土壤中的砷最终向弱结晶度的铁铝水合氧化物结合态砷(F3)、结合度好铁铝水合氧化物结合态砷(F4)和残渣态砷(F5)转化。5.结合外源砷在土壤中表面沉淀／成核、微孔扩散和有机质包裹等老化过程以及土壤性质的共同影响,首次构建了外源砷在土壤中老化的半机理模型。明确了表面沉淀/成核在外源砷老化过程中起主导作用,确定了不同环境条件下H2AsO4-和HAsO42-两种离子对表面沉淀／成核作用的相对重要性。6.外源砷胁迫不同时期对黄壤(YS)和紫色砂页岩发育的土壤(RS2)中细菌和古菌群落产生的影响不同。细菌中放线菌门(Actinobacteria)、变形菌门(Proteobacteria)和绿弯菌门(Chloroflexi)等相对丰度较高的优势种群受到砷胁迫后群落丰度变化显著,但其在两种土壤中的变化规律明显不同；而古菌中的优势种群表现出较高的耐砷性和稳定性,表明土壤中的细菌和古菌在砷胁迫下可能具有不同的群落适应机制。
[Abstract]:Arsenic is a toxic metal elements exist in nature, is also our country one of the toxic elements in the soil content exceed the standard seriously. Exogenous arsenic in soil with prolonged effectiveness in reducing toxicity or phenomena and soil colloid interaction time, the aging process, but the external source of arsenic in soil the aging process, influence factors, and the aging mechanism in the process of soil microbial community changes and other aspects of the research. This study selected several soils in red soil area of soil in different regions and typical soil by adding sodium arsenate (arsenic) indoor simulation experiment system to study the effects of arsenic in soil available the combination of arsenic and arsenic content changes with aging time, and analyzes the key factors affecting the arsenic aging process. On this basis, initially built in exogenous arsenic Half the soil aging mechanism model, and verified by the field collection of arsenic contaminated soil, the exogenous arsenic aging mechanism in the process of leading role. At the same time, the application of high-throughput sequencing technology system to study the soil physicochemical properties between two kinds of soil (yellow soil and purple sand shale development soil) bacteria and archaea in the aging changes with time as, discussed in the community under arsenic stress of bacteria and archaea in soil adaptation mechanisms. The results of this study can be used to evaluate exogenous arsenic in soil to provide theoretical support for the correct and safe use of agricultural risk of arsenic pollution on the ecological system of the main research. The results are as follows: 1. through the foreign source of arsenic in several soils on red soil aging process in soil found during the cultivation of Purple Sandy Shale soil (RS2) is effective in significantly high arsenic In other soils soil. This result means that the arsenic pollution is more serious in Hunan and other subtropical regions, the development of parent materials of arsenic in soil on farmland ecosystem hazard and risk of.2. were higher in different regions of typical exogenous arsenic in soil aging process found that exogenous arsenic into soil (FS) and irrigated desert soil (IDS1), has high effectiveness (11.64-71.16%) and the aging process to approximate balance of a longer time; and (YS) in the Yellow Soil and red soil (RS1) in lower effectiveness (0.74-31%), aging reached approximate balance for a short time, indicate the presence of exogenous arsenic in aging process in different types of soil differences. Stepwise regression results showed that the soil clay content is the key factor to determine the exogenous arsenic aging time required to approximate balance. Exogenous arsenic aging reached equilibrium time was approximate sorting in different types of soils: Cinnamon ( CS) (FS) soil irrigated desert soil (IDS1) (BNS2) red brown purple soil (RS1) (PS) (YS) yellow latosol (LS1).3. quasi two order kinetic equation can better fit the exogenous arsenic in soil changes in the effectiveness of the process (R2=0.939-0.999, P0.01). The pH value of soil and iron, aluminum, manganese oxide content is the effect of exogenous arsenic effectively, control the rate of aging and aging arsenic balance available arsenic content of soil factors. Further analysis showed that the red soil is rich in iron and aluminum oxides and aluminum oxides in the influence of the aging process is higher than that of iron oxide, aluminum oxide and arsenic may be due to the structure can combine to form more stable complexes with bidentate binuclear.4. arsenic combined with the soil morphological changes directly affect its effectiveness in the soil. The study shows that the non specifically adsorbed arsenic (F1) and specifically adsorbed arsenic (F2) constitute a major group of Available Arsenic in soil Part. With the prolonging of aging time of exogenous arsenic in soil, arsenic in iron and aluminum oxides to weak crystallinity bound arsenic (F3), the combination of good iron hydrated aluminum oxide bound arsenic (F4) and residual arsenic (F5) combined with exogenous.5. transformation of arsenic in soil and surface precipitation the nucleation, micropore diffusion and organic package aging process as well as the influence of soil properties, first constructed a semi mechanistic model exogenous arsenic in soil aging. The surface precipitation / nucleation plays a dominant role in exogenous arsenic during aging process were determined under different environmental conditions of H2AsO4- and HAsO42- two kinds of ions on the relative the importance of.6. exogenous arsenic surface precipitation / nucleation stress at different stages on yellow soil (YS) and the development of purple sand shale soil (RS2) effect in bacteria and archaea in different bacteria. Actinobacteria (Actinobacteria), Proteobacteria ( Proteobacteria) and Chloroflexi (Chloroflexi) dominant species relative abundance affected by changes in abundance after arsenic stress significantly, but in the two kinds of soil changes were significantly different; and the advantages of the archaeal populations showed arsenic tolerance and high stability, showed that the bacteria in soil and archaea in may under arsenic stress have different mechanisms to adapt to the community.

【学位授予单位】：中国农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S151.9

【引证文献】