【作者】 谢凯；

【导师】 张雁秋；

【作者基本信息】 中国矿业大学 ， 环境工程， 2014， 博士

【摘要】 淮南矿区煤炭开采导致了广泛的土地沉陷和积水，形成了大量的水塘、湖泊、湿地等不同的生态景观，水资源潜力巨大，生态环境效应突出，对矿区经济和环境可持续发展产生了重要影响。以淮南潘谢采煤沉陷积水区水环境的富营养化问题为研究中心，根据此类水生态区特殊的沉积物环境，提出两个关键科学问题：(1)沉陷区覆水农业土层中磷元素是否具有向表层或水体显著迁移的潜能；(2)相比沉陷区水域自然演化模式，较重的外源污染负荷输入是否会加速驱动土壤/沉积物中磷的迁移而对水域营养水平和结构造成重要影响。以科学问题为导向展开相应研究。在淮南潘谢矿区东部、中部和西部共选取3个代表性研究站点潘集(PJ)、顾桥(GQ)和谢桥(XQ)进行相关研究。主要内容包括五部分：(1)水环境特征调查与分析：每个站点设置7-9个水质采样点进行一年四个季度的水质调查，主要包括富营养化状态表征、营养盐含量及比例结构和水化学特征分析；(2)沉积物磷的赋存形态特征研究：采集柱状沉积物样品，对野外沉积物样品进行理化性质和磷赋存形态分析，以Psenner提取方法为基础，分别提取了NH4Cl-P、BD-P、NaOH-P和OP，并对磷的迁移转化基础和潜能进行了分析；(3)沉积物磷的吸附特征研究：以区域水化学为背景，研究实际水环境溶液中影响磷吸附特征的主控因子；(4)土柱覆水条件下磷迁移转化过程模拟研究：设计室内模拟实验，对其农业耕作层土壤初期覆水条件下的氧化还原过程进行了观察，研究了磷自农业土壤内部向“水-土”界面迁移转化过程和机制。(5)沉陷区水域水体磷的模拟研究：对沉陷积水区污染负荷方式进行了分析，区分了“封闭”水体、河湖常年连通、季节性连通3种不同水量调蓄和污染负荷模式，利用混合箱式模型分析了PJ、GQ和XQ水体磷元素水平对不同水量调蓄和污染负荷模式的响应特征。主要研究成果如下：(1)区分了淮南潘谢采煤沉陷积水区两类富营养化状态：XQ站点可以代表整个矿区富营养化的起点，属于“中度-轻度富营养化”状态；而PJ和XQ由于受外源污染，属于负荷较高的两个水体，营养状态已经过渡至“中度富营养化”水平，总磷(TP)浓度和TN浓度分布达到0.1mg/L和2.0mg/L的范围。PJ、GQ和XQ三个研究站点氮磷比较大，PO4-P浓度很低，总体上体现出磷限制的特点。(2)发现沉积物理化指标和磷的赋存形态有明显的层次差异：自表层而下，OM、氮磷、铁各形态含量均呈现出下降的趋势。PJ、GQ和XQ的OM含量均值范围分别为0.7%~1.8%、0.8%~1.7%和0.6%~1.6%；TN均值范围分别为496.6mg/kg~1069.6mg/kg、689.1mg/kg~1437.6mg/kg和592.0mg/kg~1300.8mg/kg；TP均值范围分别为201.4mg/kg~348.2mg/kg、217.8mg/kg~401.2mg/kg和159.8mg/kg~351.0mg/kg。磷的赋存形态中，铁铝结合态磷所占据比率较大(表层BD-P和NaOH-P之和所占TP比率在50%左右)。(3)提出实际水环境溶液中水化学条件对“水-沉积物”界面磷元素释放控制中作用的重要性，发现区域水化学体系中影响磷吸附特征的主控因子:区域水化学条件对磷的吸附特征具有重要影响，体系中Ca2+能显著增强磷的吸附潜能，减小内源负荷，NaHCO3弱碱性环境则不利于磷的吸附，实际水化学条件下为二者作用的综合，但CaCl2的强化作用要大于NaHCO3的弱化作用。潘谢矿区的三个研究水域，由于受人为活动影响强弱不同、水体营养水平和底质的差异，PJ站点表层沉积物磷内源负荷要强于GQ和XQ站点，起源于淹水农业土壤的沉积环境使得本研究区域沉积物磷内源负荷低于富营养化湖泊。(4)揭示了永久覆水条件下农业土壤中铁氧化还原与营养元素磷迁移转化的耦合作用及相应的生态环境效应：土柱覆水模拟实验研究表明，现阶段沉陷区水体的“好氧”状态使得“泵吸”至沉积物表层的Fe2+重新氧化后形成非晶质氧化物而强烈影响磷的迁移，除外源负荷输入的原因外，区域农业土壤中铁氧化物的丰度和活性是控制区域水体磷相对缺乏状态的一个重要机制。OM、TN、TP以及磷各形态的含量由底层向表层增加的剖面形态特征主要是由于表层土壤或沉积物的理化指标和营养元素含量的空间不均匀性所造成。铁会发生由土柱内部向表层的迁移，而磷只是发生了相应的转化，在更长的时间尺度上，如土壤有机质中呈现较高的碳磷比，BD-P有极大可能向OP进行转化。(5)提出淮南采煤沉陷区水体磷浓度对不同水量调蓄和污染负荷方式的响应模式，为定量解释区域水体富营养状态和发展趋势提供了理论依据：模拟研究结果和塌陷湖泊的实际营养盐水平状态吻合良好，不同水量调蓄和污染负荷模式下塌陷湖泊TP浓度分别能够保持在III类(TP<=0.05mg/L)和V类(TP<=0.2mg/L)的范围，从而实现不同的水体功能目标。研究结果对科学问题回答如下：研究结果中，表层沉积物BD-P和NaOH-P所占TP比例超过了50%，具备了磷释放的基础条件之一，而区域铁氧化物的丰度和活性则束缚了磷的释放。另一方面，人为活动影响导致高外源OM污染的输入会导致磷内源负荷风险增加。因此，未来淮南沉陷区水体营养调控及管理的关键策略在于磷元素的控制。更多还原

【Abstract】 Extensive coal mining in the Huainan Coal Mines has resulted in extensive landsubsidence and submergence around the mines with landscapes of pondsk, lakes andwetlands. As a result, it has produced vast water resource potencial with significantimpact on sustainability of local ecnomy and environment. This research focused onthe eutrophication in the aquatic zones around the Huainan “Panxie” coal minesubsidence areas. Two research scientific problems were proposed based on localunique sedimentary environments：Firstly, could phosphorus (P) migrate from theagricultural soil column to the surface sediment or water column? Secondly, could theheavy external pollution load impact the P behavior of transforms and transports inthe water-sediment interface, enhance P-releasing potential and changed the nutrientlevel and structure in the water bodies furthermore?Three representative sites, including PJ site in the east part, GQ site in the centralpart, and XQ site in the west part of the studied mining areas, were selected to addressrelated research work. The research included the following five parts:(1) Waterquality investigation and analysis: Annual investigations on water quality parameterswere conducted in one year period of four seasons for eutrofication status evaluation,analysis of nutrient contents and ratio, and characterization of regional waterchemistry.(2) Sediment P fractionation: P contents and fractions (NH4Cl-P, BD-P,NaOH-P and OP) in the sediments of three sites from subsided land were analyzed bythe Pesnner method for P extraction to obtain the database to determine P migrationpotential.(3) Sediment P adsorption characteristics in the sediments: P adsorptionbehavior was conducted in the sediments considering the impact of regional waterchemistry in order to clarify the role of surrounding environmental solutions on Preleasing.(4) Simulation of P transforms and transport processes after agriculturalsoils inundation: Simulated experiments were designed to observe the processes ofredox and P migration in inundated agricultural soils. The goal was to obtain theprocesses and mechanisms of P transform and transport from inside soils tosoil-overlying water interface.(5) Modelling P behavior in the aquatic zones: Differentrelationship between subsidence waters and local rivers were classified, in cases ofseparated collapse lakes, lakes of permanently and seasonal connecting to rivers,respectively. Accordingly the features for the regulation of lake storage capacity andpollution loading were characterized. The water quality model of completely mixed tanks was employed to simulate phosphorus response in the water column to differenttypes for water volume filling and pollution loading within the three sites of PJ, GQand XQ.The main results and fruits include the following five parts:(1) Eutrophication characterization: The aquatic zone at XQ site, showed “lighteutrophic” states, indicating a start point for local eutrophciton processed. Whereasthe waters at the other two sits of PJ and XQ, have been processed to“meso-eutrophic” level due to heavier pollution from external inputs, where TP andTN concentrations reached at the level of0.1mg/L and2.0mg/L, respectively. All testsamples of the two mining areas presented features of rather high nitrogen tophosphorus ration (N:P) and with low soluble P concentrations, presenting Plimitation potential in the studied aquatic zones.(2) It was found that the chemical properties and P fractionation showed theobvious difference between layers along the depth, and vertical profiles of OM, TN,TP and Feowere decreasing with the deeper layers of the sediments. The range of OMconsents was0.7%to1.8%at PJ site,0.8%to1.7%at GQ site,0.6%to1.6%at XQsite; it was496.6mg/kg to1069.6mg/kg at PJ site,689.6mg/kg to1437.6mg/kg atGQ site,592.0mg/kg to1300.8mg/kg at XQ site for TN contents; and it was201.4mg/kg to348.2mg/kg at PJ site,217.8mg/kg to401.2mg/kg at GQ site,159.8mg/kgto351.0mg/kg at XQ site, respectively. Fe/Al combined P (BD-P plus NaOH-P) hastaken the greatest proportion of TP in surface sediments.(3) It was found that regional water chemistry can impact P adsorption greatly.Usually, Ca2+can enhance P adsorption on sediment surfaces while weakly alkalineconditions caused by bicarbonates are unfavorable for its adsorption. As acomprehensive effect, the positive effect of the former is greater than the negativeeffect of the latter. The site of PJ presented greater P releasing potential than those inthe GQ and XQ sites, probably due to its higher nutrient level. Overall, P releasingrisks at present in the researched sediments are weaker than those in eutrophic lakes,while they are very similar to lakes with lower trophic levels, because of their uniquesedimentary environments from inundated agricultural soils with abundant Fe oxides.(4) Characterization of P transport and transforms processes in the sediments andevaluation of its eclogical and envrionmental effects: The research about simulationexperiment of agricultural soils inundation showed that enrichment of Fe-(hydr)oxidesin surface sediments was verified to be the main reason for limitations in regional P availability in water bodies. An increasing upward gradient in the contents of OM, TN,TP, and different P fractions was caused by spatial heterogeneity in soil properties. Fe,but not its bound P, moved upward from the submerged soil column to the surface. Pwas unable to migrate upwards towards the surface sediments as envisioned, becauseof complex secondary reactions within soil minerals. On decadal or longer time scales,BD-P has the highest likelihood of being transformed into OP, which originated froma high C:P ratio in soil organic matter.(5) Modelling P behavior and giving the theoritial explantion of P level andtrends in the aquatic zones: the simulated result matched well with the observedphosphorus levels in the studied lakes, which can be confined to different levelsmeeting national water criteria such as Class III of TP concentration less than0.05mg/L, Class IV of TP concentration less than0.10mg/L if the right or properwater reconstruction or management practices have been done.The answers to the scientific questions have been given as following: more than50%BD-P along with NaOH-P to TP presented great P releasing potential based onsediment chemical properties. However, reactive Fe oxides and their capacities for Padsorption could lead to P limitation in the aquatic zones. However, it has seriousinternal risks if given the right environments such as high organic matters loadingfrom external sources. Therefore, a key point for future ecological rehabilitation andconservation may depend on the control of P release rather than N.更多还原