【作者】 龙於洋；

【导师】 沈东升；

【作者基本信息】 浙江大学 ， 环境工程， 2009， 博士

【摘要】 垃圾填埋场是一个长期而重大的重金属二次污染源，为了保护填埋场周边土壤、地表水和地下水的环境质量，亟需对垃圾填埋场内重金属的环境行为进行准确的评估，并据此提出相应的污染防治对策。本研究以生活垃圾中含量最高的重金属Cu和Zn为目标物，首先从重金属总量的角度，基于生活垃圾组分的地域性和季节性变化因素，系统地解析了生活垃圾中重金属源分布特征，并针对重金属总量在环境行为评估的信息不足之劣势，将重金属形态分析方法引入了非均质的填埋垃圾，初步较精确地探讨了垃圾填埋过程中Cu和Zn的可能的迁移行为；基于以上结果，以生物反应器填埋场为主体，构建了三种不同工艺的模拟填埋场，聚焦于填埋垃圾及渗滤液这一整体系统，深入系统地研究了Cu和Zn在生物反应器填埋场稳定化过程中的释放行为，提出了不同运行方式模拟填埋场中Cu和Zn总量的长期环境渗沥模型及各形态迁移转化模型，揭示了生物反应器填埋场中重金属原位固定的SRB调控现象。主要结论为：（1）生活垃圾中Cu和Zn均不同程度地超过了土壤二级环境质量标准，具有较高的重金属污染潜力，尤其春夏两季，较好的垃圾分类收集能明显降低其中重金属来源。塑料、厨余、灰渣和纸张四类垃圾组分对生活垃圾的重金属Cu、Zn总量贡献最大，生活垃圾的重金属污染源头控制有赖于对该四类组分的削减。（2）修正BCR连续提取方法对0-7a的不同填埋龄的生活垃圾中Cu和Zn的形态分析具有极高的重现性和回收率，在应用于非均质的填埋垃圾体系时能更为准确地反映垃圾填埋场中不同稳定化程度下重金属对应的环境行为。不同的填埋垃圾样品预处理方法对形态分析结果的影响因素主要为填埋垃圾的NH₄⁺-N、VFA、硫化物等原始环境条件的变更所致，湿样是填埋垃圾样品形态分析最理想的预处理方式。（3）由于渗滤液的迁移，不同运行方式的模拟填埋场的下层垃圾中Cu和Zn含量均明显高于上层垃圾，其中Zn较Cu具有更强的迁移性。填埋垃圾的稳定化差异及由此而引起的重金属的不同释放机理导致Cu和Zn含量呈现阶段性增减变化，变化幅度为CL（普通卫生填埋场）＞RL（直接回灌型生物反应器填埋场）＞BL（序批式生物反应器填埋场）、Cu＞Zn，产酸阶段填埋垃圾中Cu和Zn具有最高的环境污染风险，随模拟填埋场的稳定化程度增加，填埋垃圾中Cu和Zn释放行为逐步减缓并趋于稳定。（4）渗滤液中Cu（Ⅱ）和Zn（Ⅱ）的浓度变化与填埋垃圾中Cu和Zn的释放行为形成强烈响应，不同运行工艺的模拟填埋场渗滤液中重金属浓度差异不明显。普通卫生填埋场的重金属释放量符合的正指数递增模型，而生物反应器填埋场的释放量则遵循不同阶数的负指数衰减模型，渗滤液的回灌操作较普通卫生填埋能明显降低填埋场对外环境的重金属输出，而两相分离的产甲烷反应器的引入更能促进重金属在生物反应器填埋场内的行为稳定。（5）渗滤液的回灌能促使Cu和Zn形态从不稳定态（酸可溶解态和可还原态）往稳定态（可氧化态和残渣态）迁移从而可减缓其释放行为，Zn比Cu具有更强的环境迁移和污染潜力。不同时期不同深度填埋层内Cu和Zn形态的差异明显，填埋垃圾的好氧环境的暴露能促使Cu和Zn从稳定态向不稳定态迁移。（6）Cu和Zn的各级形态与环境因素的回归模型表明填埋场环境中氨氮、HA、FA、DOC、硫化物、硫酸盐等环境因素对Cu和Zn的各级形态影响较大，其中硫化物对Cu和Zn在填埋环境中的迁移影响最大，分别与Cu和Zn的不稳定态（酸可溶解态和可还原态）呈显著负相关，与稳定态（可氧化态和残渣态）呈显著正相关。Visual MINTEQ模拟计算结果表明，渗滤液中Cu（Ⅱ）大部分为腐殖质络合态，并逐渐由与松结合态富里酸络合态（FA₁-Cu）向稳结合态富里酸络合态（FA₂-Cu）转变；Zn（Ⅱ）则主要表现为与S^2-的络合，其络合程度随模拟填埋场内还原性环境形成而加剧，生物反应器填埋场的渗滤液长期回灌能促使Cu和Zn逐步形成络合沉淀而使其在填埋垃圾内的迁移行为减缓。不同方式填埋场渗滤液的重金属环境风险并不在于其瞬时浓度及形态，在于长期渗滤而引起的量累积。（7）生物反应器填埋场中较高的SRB代谢活性及其逐步累积的代谢产物硫化物是填埋垃圾中的Cu²⁺和Zn²⁺形成硫化物沉淀而发生重金属原位固定现象主要原因，生物反应器填埋场中重金属存在原位固定的硫酸盐还原菌调控机理，初步从形态判断填埋垃圾中的优势硫酸盐还原菌属普通脱硫弧菌属（Desulfovibriovulgaris sp．），其对Cu²⁺和Zn²⁺的生物沉降能力约1-10ppm。更多还原

【Abstract】 Landfill site is a long-term and serious secondary pollution because of heavy metal.With respect to protect the environmental quality of the soil, the surface water, and theground water near landfill site, there is a need to evaluate the environmental behaviorof heavy metal in landfill and carry out conservation strategy accordingly. In thisstudy, Cu and Zn were chosen to evaluate the heavy metal behavior in landfill duringdecomposition. Firstly, considering the regional and seasonal variation of MSWcomponents, the characteristic of Cu and Zn distribution in MSW wascomprehensively studied. Based on the insufficient information of heavy metal totalcontent, sequential extraction procedure was also adapted to the heterogeneous MSWto assess the possible migration of Cu and Zn in it more pertinently. Subsequently,three simulated MSW reactor landfill with different operation modes were constructedbasing on the bioreactor landfill. Focusing on the inseparable system includingleachate and landfill refuse, the releasing behavior of Cu and Zn in bioreactor landfillduring decomposition was studied. The long-term leaching behavior of Cu and Zncontent from landfill with different operation modes were modeled. Moreover, themigration of Cu and Zn fractionations in MSW basing on modified BCR sequentialextraction procedure were also modeled. Finally, the phenomenon of in-situbio-immobilization of heavy metal in refuse from bioreactor landfill was presented..The main conclusion of this study was list below.（1）The Cu and Zn contents in MSW exceeded the set standard for "environmentalquality standard for soil" of China with different degree. The MSW has high potentialof heavy metal pollution, especially in spring and summer. The heavy metal source inMSW can be cut by orderly classification. Components including plastic, foodresidual, dust, and paper are the four main contributions for total heavy metal contentin MSW. The controlling of heavy metal pollution source in MSW depends on the cutof the four above MSW components. （2）When it used to MSW with different landfill age among 0-7 yr, the modifiedBCR sequential extraction procedure has high recovery and reproducibility. It is moreexactly to evaluate the environmental behavior of heavy metal in MSW, a veryheterogeneous matrix, at different degradation stage accordingly. Effect of samplepretreatment on speciation of Cu and Zn in different MSW samples illustrated that theshift of sample characteristics such as ammonia nitrogen （NH₄⁺-N）, volatile fatty acid（VFA）, sulfide were the main reasons. The fresh sample is the ideal pretreatmentmanner of sequential extraction for MSW, and air drying is the other better choice.（3）The contents of Cu and Zn in MSW from bottom layers are always higher thanthat from upper layers due to the migration of leachate. Zn has higher mobility thanCu in MSW. The different releasing behavior of Cu and Zn caused by the differenceon MSW decomposition led to the staggered variation of Cu and Zn contents in MSWaccordingly. The variation degree ranking were CL＞RL＞BL and Cu＞Zn. The Cuand Zn contents in MSW at acidification phase have the highest environmental risk.Cu and Zn in MSW showed behaviors of staggered migration and retention gradually,which corresponded with the degradation process of landfill obviously.（4） The variation on Cu²⁺ and Zn²⁺ concentrations in leachate reflected thereleasing behavior of Cu and Zn in landfill refuse at different stage accordingly. Therewere no significant differences on the concentration of heavy metal in leachate fromlandfills with different operation modes. The leaching amounts of heavy metals fromthe conventional reactor landfill fit for the positive exponential increase model, whilethat of bioreactor landfills fit for negative exponential decrease models. The operationof leachate recirculation can obviously reduce the heavy metal leaching amount fromlandfill into environment than conventional operation, and the introduction ofsequential phase acidification reactor can promote the immobilization of heavy metalin landfill refuse.（5）The leachate recirculation promoted the speciation of Cu and Zn shift fromunsteady fractions （acid soluble fraction and reducible fraction） to steady fractions（oxidable fraction and residual fraction）, and attenuated their migration. Zn has higherpotential of migration and pollution than Cu in MSW. There are significant differences on Cu and Zn speciation in MSW from different landfill layers. Theaerobic exposure can promote the migration of Cu and Zn speciation from steadyfractions to unsteady fractions.（6）The regression models of Cu and Zn speciation indicated that characteristics, i.e.ammonia nitrogen, HA, FA, DOC, sulfide, sulfate, are the main factors of heavy metalspeciation variation.Especially, sulfide has significant positive correction and negativecorrection with unsteady fractions （acid soluble fraction and reducible fraction）andsteady fractions （oxidable fraction and residual fraction）of Cu and Zn in MSW,respectively. Simulation computation results from Visual MINTEQ showed that Cu²⁺was mainly associated with humus and migrated from lose association （FA₁-Cu） totight association （FA₂-Cu）, while Zn²⁺ was mainly presented with complexation withS^2- which was strengthened as the reducing environmental surrounding in landfillgradually. The long-term leachate recirculation in bioreactor landfill can promote theprecipitation of Cu and Zn as complexation and attenuate their migration. Theenvironmental risk of leachate from landfill with different operation modes depend ontheir accumulation amount rather than their sudden concentrations and fraction.（7）The high SRB metabolism activity and the accumulation of metabolite （sulfide）were the main reasons of in-situ precipitation phenomenon of Cu²⁺ and Zn²⁺ inlandfill refuse in bioreactor landfill. Heavy metals in bioreactor landfill havemechanism of in-situ immobilization controlling by SRB metabolism. Thepredominant SRB in landfill refuse belongs to Desulfovibrio vulgaris sp. with theCu²⁺ and Zn²⁺ bio-precipitation of 1-10 ppm approximately.更多还原