【作者】 陈孝杨；

【导师】 严家平； 许光泉； R.Anlauf；

【作者基本信息】 安徽理工大学 ， 环境工程， 2013， 博士

【摘要】 煤炭开采与燃烧利用引发两大主要环境问题,一是大面积地表塌陷的形成造成耕地损失,破坏区域生态环境；二是煤矸石等煤系伴生物产生和燃煤电厂固体废弃物的排放压占土地,通过扬尘与淋滤液等污染周围大气、水体和土壤环境。为应对这些环境问题给矿区可持续发展带来的挑战,利用固体废弃物充填重构土壤剖面进行土地复垦和生态环境修复的工程措施在矿区被较多地实施,其中燃煤电厂废弃物(如粉煤灰)作为充填基质是一种重要的形式。这种复垦地的土地利用方式若为林地或耕地,其土壤剖面水分运动和溶质迁移机理是需要研究解决的关键问题之一。论文应用实验室土柱试验和现场小区试验,重点研究重构土壤水分入渗和作物生长条件下水量平衡规律,粉煤灰高可溶性盐的迁移和污染深部土壤或地下水环境的可能性,以及重构土壤盐分剖面变化特征。在此基础上,探讨复垦地作物生长对水盐条件变化的响应与重构土壤肥力质量。以期为完善煤矿区充填重构土壤水盐运动的理论研究和复垦地植物栽培的田间管理实践等作出重要贡献。(1)设计覆土厚度为20cm和35cm的试验土柱,并分别控制不同的地下水位(-115cm和-300cm),研究重构层状土壤水分入渗和盐分迁移规律。结果表明：实验设计的两种覆土厚度对入渗锋下移速率影响的差异性存在但不显著,表土和粉煤灰层间水分入渗有明显的界面特征。强供水条件下,粉煤灰层中的K+和Cl-随水分快速向下运动,若污染防治措施不当,容易造成深部土壤或周围地下水中盐分离子浓度的短期急剧升高。地下水位对重构土壤水分入渗有显著影响,低地下水位时,入渗锋呈规则下移；高地下水位时,入渗锋与毛管水上升面出现界面胶结现象,交锋面约在-40cm处,所需时间约为灌溉后12h。(2)对照安徽省淮南市2001-2010年降雨量和蒸发量资料,应用Hydraus-1D软件模拟极端气象条件下重构土壤水量平衡特征,发现当地下水位较低(-300cm)时,含水量明显受到气象条件的影响,干旱年份与湿润年份相差0.100cm3/cm3左右,尤其是表层土壤含水量变化明显。高地下水位(-115cm)时,粉煤灰层含水量基本不受气象条件影响,始终在近饱和状态,表层土壤虽有变化,但幅度相对较小。无论干旱或湿润年份,表层土壤含水量均在田间含水量上下波动,能够满足作物生长需求。此时,试验的两种覆土厚度对含水量的影响差异很小。(3)分别建立覆土厚度25cm和45cm的田间试验小区,设置对照小区并控制地下水位(约-150cm),研究小麦生长条件下重构土壤水分平衡和盐分剖面特征。结果表明,试验小区粉煤灰层的含水量在整个小麦生长周期均接近饱和含水量,受气象条件的影响程度低,而表层土壤含水量与降雨量呈显著正相关。试验小区的表层土壤含水量在小麦生长各时期都低于对照小区,有限的表土厚度增加并不能改变粉煤灰充填重构土壤的水分条件。通过验证发现根系吸水条件下的Richards方程在描述重构土壤田间含水量变化时存在缺陷,计算值与实测值相比明显偏低。文章据此对Richards方程的源汇项进行了修正,引入了λ值,其计算公式为λ=γ*(dpb/dθ)。同时,试验小区土壤中SO42-、Mg2+和Ca2+含量较高,C032-和HCO-含量较低。与对照小区相比,试验小区土壤总可溶性盐分含量较高,在小麦生长的整个周期内,表土厚度越薄,重构土壤对可溶性盐分的聚集和保持能力越差。可溶性盐组分在重构土壤中的剖面特征明显。C032-和HCO-在小麦生长的各个阶段,自土壤表层至粉煤灰层,含量逐渐降低,而Cl-、SO42-和四种阳离子的含量自土壤表层至粉煤灰层,含量逐渐增加。(4)粉煤灰充填重构土壤水盐条件与小麦籽粒产量间存在明显“相悖”现象,即试验小区粉煤灰层含水量始终高于对照小区,而籽粒产量却显著低于对照小区(p<0.05)。由研究结果揭示其原因主要有两个方面：一是粉煤灰有低容重、大颗粒比表面积、强水分吸持能力等性质,水分向上输送困难,表层土壤含水量受其影响较小；二是重构土壤盐分含量总体不高,肥力质量综合指数较低,影响小麦生长和籽粒产量。覆土厚度与小麦产量间关系可用dY/dH=(-0.3632+0.0021H)*H+11.315经验模型来描述。复垦地表层土壤的最优厚度为35～45cm。(5)论文在研究重构土壤理化性质基础上,构建肥力质量评价指标体系,并应用主成分分析法和专家打分法相结合,赋予各指标的权重系数,建立评价模型。评价结果揭示对照小区的土壤肥力综合指数最高,其次为覆土厚度45cm的试验小区,覆土厚度25cm的试验小区最低,这与小麦籽粒产量结果一致。重构土壤养分肥力指标NFI值和土壤肥力质量综合评价指标IFI值之间存在极显著相关性,相关系数为0.9784(p<0.01,n=12)。更多还原

【Abstract】 There are many environmental problems from coal mining and coal combustion, the arable land loss and regional ecological environment destruction for a large area surface subsidence, the environmental pollution of atmosphere, water and soil through dust and leachate from solid waste, and so on. Furthmore, a great quantities of lands are occupied by the coal-series concomitants (i.e. coal gangue) and coal combustion residues (i.e. fly ash). Some engineering measures in coal mining areas were applied in response to the challenge of these environmental problems to sustainable development, that were the land reclamation and ecological environment restoration by reconstructing soil profiles filled with the solid waste. One of the important rilling matrix was fly ash (FA). Water movement and solute transport mechanism of reconstruction soil profiles are the key problems which should be studied and solved if the land use pattern of the reclamation soil is woodland or farmland.Soil columns and field plots were built to focuse on simulating water infiltration and water balance under the crop growing conditions in reconstruction soils. The possibility is also studied of high soluble salt in FA layers transporting to deeper soil layer or groundwater environment, including salinity concentration variation of reconstruction soil profiles. On this basis, the response of crop growth to water-salt conditions change and fertility quality of the reconstruction soil were discussed to improve the soil water-salt movement theories and plant cultivation field managements of coal mining areas.(1) The soil columns of two different cover soil thickness (20cm and35cm) were designed for studying the water infiltration and salt migration of reconstruction layered soil, with controling two different groundwater levels (-115cm and-300cm). The results show that the differences exist but does not significantly of the experimental designed two topsoil thickness affecting on the infiltration front downshift rate and the moisture infiltration has obviously interface features between the cover soil and FA layer. At the same time, K+and Cl" of FA will rapidly move downward along with moisture under strong water supply. The short-term sharp rise of salt ion concentration is very easy in deeper soil layer or groundwater around if no proper pollution prevention measures. In addition, the groundwater table can remarkably affect on water infiltration of the reconstruction soil. The infiltration front is well-regulated down under the low groundwater table condition, while the interface cemented phenomenon appears between the infiltration front and capillary water rise surface under the high groundwater table condition, the surface confrontation-40cm and time12h after irrigation.(2) The field water balance of reconstruction soil under the extreme climate conditions were simulated by Hydraus-1D software according to precipitation and evaporation data from2001to2010in Huainan, China. The results show that reconstruction soil moisture contents are obvious influenced by the meteorological conditions when the groundwater level is low (-300cm), and the difference is about0.100cm3/cm3between dry years and wet years. Especially, moisture changes are significant in the cover soil. Moreover, the water content in FA layer is substantially independent of meteorological conditions under the high groundwater level (-115cm), always near saturated. And water content variable magnitude is also relatively small. While the topsoil moisture content fluctuates along to the field water content and can meet the demand for crop growth, whether drought or wet years. In this case, the effect difference is very small of the experimental two topsoil thickness to water content.(3) The water balance and salt distribution of reconstruction soil profiles with wheat growth were studied through establishing the experimental plots of cover soil25cm and45cm, setting the control plots and controlling the groundwater table (-150cm). The results show that the moisture content in FA layer of experimental plots is closed to the saturated water content in the whole wheat growth cycle and less subjected to weather conditions, while that of cover soil is the significant positive correlation to the rainfall. Furthermore, the topsoil water content of experimental plots is lower than those of the control plots in wheat growth periods and the limited cover soil thickness increase does not change the moisture conditions of reconstruction soil filled with FA. Even more, the Richards equation with root uptake has defect as describing field water content variation of reconstruction soil, namely the calculated values lower than measured ones. So the concept of compensation factor is put forward to Amending Richards equation, which is calculated as λ=γ*(dpb/d(?)). Meanwhile, SO42-, Mg2+, and Ca2+concentration of soil in experimental plots are higher than that in control plots, and the total soluble salt content also higher, while CO32-and HCO- concentration are lower. The thinner of topsoil, the poorer of the ability from accumulating and keeping soluble salt in whole wheat growth cycle. Besides, the distribution characteristics of soluble salt components is clear in reconstruction soil profiles. CO32-and HCO" concentration gradually decrease from the topsoil to FA layer, while those of Cl-, SO42-, and four cations gradually increase in relevant position in various stages of wheat growth.(4) The inconsistent phenomenon is obvious between water-salt conditions of reconstrucion soil filled with FA and wheat grain yield, that is, water content in FA layer of experimental plots is always higher than that of the control ones, but the wheat grain yield remarkably lower (p<0.05). Two reasons mainly are uncovered form research results. Although water content of FA layers is high nearly saturated one but the its impact on topsoil is less because of FA properties with low bulk density, large particles specific surface area, and strong water suction holding capacity firstly. Secondly, low salinity content and fertility quality in reconstruction soil affect on wheat growth and grain yield. Model dY/dH=(-0.3632+0.0021H)*H+11.315can be described the relation between topsoil thickness and wheat yield.(5) This paper built the fertility quality evaluation index system on the basis of studying soil physico-chemical properties. And the weight coefficients were assigned to each index with the method of principal component analysis and expert scoring combination to establishing the reconstruction soil fertility quality evaluation model. The assessment results that soil fertility composite index of the control plots is the highest, following cover soil45cm, and that of topsoil25cm in experimental plots is the minimum, which is consistent with the results of wheat grain yield on field plots. Additionally, the correlation coefficient is0.9784between nutrient fertility indexes NFI and fertility quality comprehensive index IFI of reconstruction soil, expressively remarkable correlation (p<0.01, n=12).更多还原