【作者】 郑永红；

【导师】 胡友彪；

【作者基本信息】 安徽理工大学 ， 环境工程， 2017， 博士

【摘要】 溶解性有机碳(DOC)是土壤有机碳的重要组成部分,具有移动快,稳定性差,易氧化分解的特点,对污染物特别是重金属具有很强的吸附和络合能力,影响重金属在土壤中吸附解吸行为。本论文围绕淮南潘一矿区,选择重金属镉(Cd)为污染物典型代表,通过对煤矸石风化物和土壤的基本理化特性、Cd和DOC含量的测定,影响因素的确定,系统分析了煤矸石风化物-土壤系统中DOC的分布特征、DOC和Cd吸附解吸机制及动力学模型。最后研究了在该系统中DOC影响下,Cd的吸附解吸机制及动力学模型,并建立了小尺度多因素耦合函数模型。(1)DOC在煤矸石风化物-土壤系统中的分布特征表明:煤矸石风化物中DOC含量高于土壤,DOC在雨水的淋溶作用下,向周边土壤迁移趋势明显,对周边土壤DOC含量有较大的贡献,贡献率随离煤矸石山距离的增大而降低。在垂直方向上,煤矸石风化物中DOC含量随深度的增加逐渐变大;土壤中DOC含量则先减少后增大。另一方面,DOC含量随着温度、pH、含水率的增加而增大,与有机质、全氮、速效磷之间呈极显著或显著正相关关系。(2)DOC在煤矸石风化物和土壤中的吸附解吸特性表明:煤矸石风化物对DOC的吸附量和解吸量均低于土壤,并随着DOC浓度的升高而增大,但煤矸石风化物对DOC的解吸率大于土壤。因此,DOC容易通过淋溶和雨水径流途径进入土壤,增大土壤DOC含量。煤矸石风化物和土壤对DOC的吸附、解吸动力学曲线表明,吸附和解吸过程都存在2个阶段,即快速反应阶段和慢速反应阶段。吸附过程包括0～1h的快速吸附和1.2～6h的慢速吸附;解吸过程包括0～1h的快速解吸和1.2～6h的慢速解吸。(3)Cd在煤矸石风化物和土壤中的吸附解吸特性表明:煤矸石风化物对Cd的吸附量和解吸量均高于土壤,并随着Cd浓度的升高而增大。另一方面,煤矸石风化物对Cd的解吸率大于土壤,因此Cd容易通过淋溶和雨水径流途径迁移进入土壤、地表水及地下水,造成二次污染。煤矸石风化物和土壤对Cd的吸附、解吸动力学曲线表明,吸附和解吸过程都存在2个阶段,即快速反应阶段和慢速反应阶段。吸附过程包括0～0.5h的快速吸附和1～12h的慢速吸附;解吸过程包括0～2h的快速解吸和2.5～12h的慢速解吸。(4)DOC影响下,Cd在煤矸石风化物和土壤中的吸附解吸特性表明:DOC的加入,能够抑制煤矸石风化物和土壤对Cd的吸附能力,使吸附率降低了7.55%～15.04%,同时提高了二者对Cd的解吸能力,解吸率提高了 20.10%～50.29%。不同浓度DOC影响下,随着DOC浓度的增大,煤矸石风化物和土壤对Cd的吸附量逐渐减小,解吸量逐渐增大。DOC影响下,煤矸石风化物和土壤对Cd的吸附、解吸动力学曲线表明,吸附和解吸过程都存在2个阶段,即快速反应阶段和慢速反应阶段。吸附过程包括0～0.5h的快速吸附和1～12h的慢速吸附;解吸过程包括0～2h的快速解吸和2.5～12h的慢速解吸。(5)分别建立了 Cd在煤矸石风化物-土壤系统中吸附解吸多因素耦合函数模型:采用灰色理论对Cd在煤矸石风化物和土壤中的吸附量、解吸量影响因素进行灰色关联分析排序为:Cd浓度>DOC浓度>pH>温度。利用回归分析方法,分别建立了在DOC影响下,煤矸石风化物和土壤对Cd吸附量、解吸量多因素耦合函数模型,即:Y=a+bXHA+cXT+dXpH+eXCd。该模型与实测值进行验证相对误差较小,可以应用于淮南复垦区域内或类似矿区的预测和验证工作。综上所述,进入土壤环境中的Cd易于吸附,长期滞留在土壤环境导致土壤污染。而DOC的加入,能明显抑制煤矸石风化物和土壤对Cd的吸附能力,且能有效降低Cd的吸附量,提高其解吸量,为利用土壤污染修复技术来治理Cd污染土壤提供一种新的思路和方法。更多还原

【Abstract】 Dissolved organic carbon(DOC)was an important component of soil organic carbon,which charactered as high mobility,poor stability,easy oxidation of pollutants.It can easily adsorpted the pollutant especially for the heavy metals and affected the adsorption and desorption behavior of heavy metals in soil.In this study,heavy metal cadmium(Cd)was selected as the typical representative of pollutants in PanYi coal mining area in Huainan.By determination of the selected physicochemical properties of coal gangue weathering matter and soil,Cd and DOC contents and the influencing factors,the migration and distribution characteristics of DOC were systematically analyzed in the coal gangue weathering matter-soil system.The mechanism and dynamic model for the adsorption and desorption of DOC and Cd were also summed in this research.In addition,the mechanism and dynamic model of the adsorption and desorption of Cd affected by DOC in the system were investigated as well,and established multifactor coupling function model in small scale.(1)The distribution characteristics of DOC in coal gangue weathering matter-soil system showed that the content of DOC in coal gangue weathering matter was higher than that of soil.Under the leaching of rainwater,the migration trend of DOC from coal gangue dump to surrounding soil was obvious.The coal gangue weathering matter has a great contribution to the DOC content in the surrounding soil,and the rate of contribution decreased with the increasing of the distance from the coal gangue dump.In vertical direction,the content of DOC in coal gangue weathering matter gradually increased with the increase in depth.The content of DOC in soil decreased first followed by increased.On the other hand,the content of DOC increased with the increase of temperature,pH and moisture content,and had extremely significant or significant positive correlation with organic matter,total nitrogen and available phosphorus.(2)The adsorption and desorption characteristics of DOC in coal gangue weathering matter and soil showed that the adsorption and desorption capacity of DOC on coal gangue weathering matter was lower than that of the soil,and increased with the increasing of DOC concentration.However,the desorption rate of DOC from coal gangue weathering matter was higher than that from soil.Therefore,DOC was easy to enter soil and increased the content of DOC in soil via leaching and rainwater runoff.The adsorption and desorption dynamics curves of DOC showed that there were 2 stages of adsorption and desorption,categorized as the rapid reaction stage and the slow reaction stage.The adsorption process included the rapid adsorption of 0～1h and the slow adsorption of 1.2～6h.The desorption process included a rapid desorption of 0～1h and a slow desorption of 1.2～6h.(3)The adsorption and desorption characteristics of Cd in coal gangue weathering matter and soil showed that the adsorption and desorption capacity of Cd was higher than that of the soil,and increased with the increasing of Cd concentration.On the other hand,the desorption rate of Cd from coal gangue weathering matter was higher than that of soil.Therefore,Cd was easy to entered into the soil、surface water and groundwater by leaching and rainwater runoff,leaded to secondary pollution.The adsorption and desorption dynamics curves of Cd from coal gangue weathering matter and soil showed that there were 2 stages of adsorption and desorption,categorized as the rapid reaction stage and the slow reaction stage.The adsorption process included the rapid adsorption of 0～0.5h and the slow adsorption of 1～12h.The desorption process included a rapid desorption of 0～2h and the slow desorption of 2.5～12h.(4)The adsorption and desorption characteristics of Cd in coal gangue weathering matter and soil under the influence of DOC showed that the results showed that the addition of DOC could inhibit the adsorption capacity of Cd on the coal gangue weathering matter and soil,which reduced the adsorption rate by 7.55%～15.04%.With the addition of DOC,the desorption ability of Cd for the coal gangue weathering matter and soil was improved,with the desorption rate increased by 20.10%～50.29%.Under the influence of different concentrations of DOC,with the increasing of DOC concentration,the adsorption of Cd by coal gangue weathering matter and soil decreased gradually and the desorption capacity increased gradually as well.Under the influence of DOC,the dynamics curves based on the adsorption and desorption of Cd by coal gangue weathering matter and soil showed that there were 2 stages of adsorption and desorption,categorized as the rapid reaction stage and the slow reaction stage.The adsorption process included the rapid adsorption of 0～0.5h and the slow adsorption of 1～12h.The desorption process included a rapid desorption of 0～2h and a slow desorption of 2.5～12h.(5)The model established from adsorption and desorption multifactor coupling model of Cd in coal gangue weathering matter-soil system showed that the grey correlation analysis was carried out by using grey theory to analyze the influence factors of the adsorption and desorption quantity of Cd could build the order was as follows:Cd concentration>DOC concentration>pH>temperature.Based on the regression analysis method,the model of adsorption and desorption multifactor coupling function of Cd in coal gangue weathering matter-soil system could be established under the influence of DOC,as,Y=a+bXHA+cXT+dXpH+eXcd.The relative error between the model and the measured value was small and it could be applied to the prediction and verification of the reclamation area in Huainan or similar mining areas.In conclusion,Cd was easy to be adsorbed in soil environment and could result in long-term soil contamination.Addition of DOC could significantly inhibit the adsorption ability of Cd in coal gangue weathering matter-soil system,effectively reduce the adsorption capacity of Cd and improve the Cd desorption.It provided a new idea and method in remediation technology of Cd contamination in soil.更多还原