【作者】 易秀；

【导师】 李佩成；

【作者基本信息】 长安大学 ， 地质工程， 2003， 博士

【摘要】 地下水是黄土地区重要的水资源。在人类农事活动和水事活动日益增强的情况下，如何利用包括土壤层在内的黄土地层自身的净水作用，保护地下水不受污染，具有重大的理论和实际价值，这是本论文的立项依据。作者在论文中依次研究了如下问题，并得出了相应的结论： （1）通过论证黄土的物理化学性质与结构特性，得出利用广布而深厚的黄土地层净化污水，以保证地下水的供给安全，这在黄土地区是可行的，并具有重大意义。 （2）分析了由于农事和水事活动所发生的土层入渗水中的污染元素，确定了毒性强、数量大、易迁移的铬、砷作为主要研究对象，研究其在黄土类土中的行为作用有代表性意义。 （3）开展试验从静态角度揭示土壤对铬、砷的净化机制、净化能力及影响因素。结果表明： ①黄土类土中Cr（Ⅲ）被净化主要是Cr（Ⅲ）形成Cr（OH）₃的沉淀作用； ②黄土类土对Cr（Ⅵ）和As（Ⅴ）的吸附主要为专性吸附，Cr（Ⅵ）被吸附的形态是HCrO₄^-； ③根据测得的土壤吸附量利用朗格谬方程计算出整个黄土土层对Cr（Ⅵ）的平均最大吸附量为162μg／g，As（Ⅴ）为552μg／g； ④黄土中Cr（Ⅵ）被净化，是吸附作用和还原作用的综合表现。对As（Ⅴ）的净化机制不只限于吸附作用，还包括沉淀等其他理化作用； ⑤影响黄土对Cr（Ⅵ）、As（Ⅴ）起净化作用的主要因素有pH、有机质、铁、铝、钙化合物、土壤粘粒含量等。 （4）通过土柱淋滤试验，从动态角度研究得出铬、砷在黄土中具有以下迁移规律及特点： ①Cr（Ⅵ）、As（Ⅴ）在黄土中的吸附和迁移与土壤中的粘粒含量有关。迁移速度顺序为Cr（Ⅵ）＞As（Ⅴ）。黄土对As（Ⅴ）的净化能力比净化Cr（Ⅵ）强； ②Cr（Ⅵ）在黄土中的迁移形式为CrO₄^2-，As（Ⅴ）的迁移形式为HAsO₄^2-； ③当一定深度的土壤层达到吸附饱和状态时，如果持续增加污水淋入量时，则吸附饱和状态的界限就会向深部移动，淋出液中的Cr（Ⅵ）、As（Ⅴ）亦会随水向深部转移； ④当污水入渗液中铬、砷浓度小于10.0mg／L时，黄土5m深度可作为Cr（Ⅵ）的净化深度，1.5m深度可作为As（Ⅴ）的净化深度。 （5）研究了Cr（Ⅵ）和As（Ⅴ）与营养元素钙、镁、磷及它们相互之间的交互作用。初步发现钙、镁对黄土吸附Cr（Ⅵ）有减小作用，对吸附As（Ⅴ）有增大作用；Cr（Ⅵ）和As（Ⅴ）同时存在时，似乎在黄土中的吸附量有相互促进趋势。 （6）在全面阐述土壤环境容量模型的基础上，用土柱淋滤试验方法研究首次得出了黄土类土中铬、砷的土壤环境容量分别为95.9kg／ha和12.6kg／ha。 （7）在陕西关中交口灌区进行了相关的野外试验研究，进而选用不同模型耦合计算得出当灌溉水中铬、砷浓度不超过10.0m目1时，黄土地下水“防污埋深”对铬不小于5.0m，对砷不小于1.5m。 以上取得的研究成果，为保证黄土区水资源的可持续利用提供了理论和实践依据。更多还原

【Abstract】 Groundwater is important water resources in loess land. With increasing of human being’s activities on farming and watering, it has great theoretical and practical significance on how to utilizing purification function of loessial soil to protect groundwater from polluting, which is the basis of building item of this paper. On the basis of these, the author studies the following problems and draws corresponding conclusions:(1) By demonstrating physichemical and structural character of loessial soil, the results are obtained that it is having great meaning to utilize widely distributive and profound loessial soil resources to purify sewage for protecting groundwater supplying security.(2) The contaminative elements are analyzed that is penetrated in soil by human being’s activities on farming and watering, and Cr and As are decided as the primary researching objects which have great toxicity, quantities and easy migration. There is representative meaning to researching the action of Cr and As in loessial soil.(3) By experiments the paper reveals purification mechanism and ability and its influencing factors of soil to Cr and As. The results indicate:1) The main action to purifying Cr(III) in the loessial soil is that Cr(III) changes into Cr(OH)s. 2) The main absorption to Cr(VI) and As(V) is special absorption. The absorption form of Cr(VI) is HCrO4-. 3) Calculated by Langmuir equation the average absorption quantity of loessial soil layer to Cr(VI) is 162ug/g and to As(V) is 552ug/g. 4) Cr(VI) in loess purified is synthetical effects of adsorption and reduction. The purification mechanism to As( V) is not only absorption , and also includes other physical and chemical actions. 5) The main factors influencing loessial soil purification to Cr(VI) and As(V) are pH, organic matter, calcium, iron, aluminous compounds and contents of mucilaginous grain etc.(4) By the infiltration test of soil column, the author concludes that Cr and As has the following migration patterns by dynamic researches.1) The absorption and migration of Cr(VI) and As(V) in loessial soil relate to content of mucilaginous grain. The order of migration velocity is Cr(VI) > As(V). The purification ability of loessial soil to As( V) is strongger than Cr(VI). 2) The migration form of Cr(VI) in loessial soil is CrO42-, and that of As(V) is HAsO42-. 3) With a certain deepness when layer of soil reaches saturated absorption, the limit of saturated absorption will move to deeper place, with which Cr(VI) and As(V) will move to deeper place too, if infiltration quantity of sewage is continually increasing. 4) When concentration of Cr and As is less than 10.0mg/Lin sewage infiltration fluid, the purification depths of Cr(VI) is 5m, and that of As(V) is 1.5m in loessial soil.(5) The paper discusses interaction of Cr(VI) and As(V) with nutritional element: Ca, Mg, P and finds that Ca and Mg have decrease absorption of loessial soil to Cr(VI) and have increase to As(V).Between Cr and As have possibly promotion to absorption amounts in loessial soil.(6) Utilizing infiltration experiment of soil column, the results show that environmental capacity of Cr and As in loessial soil is 95.9kg/ha and 12.6kg/ha.(7) Exampled by Jiaokou irrigation district in Shaanxi, the author forecasts the influence of irrigation to Cr and As of groundwater by investigating and monitoring irrigation water resource, groundwater and soil. The paper concludes that the safety buried depths of preventing groundwater from being polluted by Cr and As in irrigation district are not less than 5.0m and 1.5m on condition that concentrations of Cr and As in irrigation water are less than 10.0mg/L.更多还原