【作者】 刘静；

【导师】 戴亚南； 彭渤；

【作者基本信息】 湖南师范大学 ， 自然地理学， 2021， 硕士

【摘要】 黑色页岩是形成于海相还原环境的、富含有机质和硫化物矿物、化学性质特殊的沉积岩。黑色页岩暴露于地表极易发生风化分解,其风化分解过程中释放CO₂、产生酸性水溶液、淋滤释出Pb、Zn、Cd等重金属而对环境产生影响,引起环境（土壤、水体）重金属污染。故黑色页岩风化及其环境效应的研究受到特别关注。黑色页岩风化过程中元素的活动性是表征黑色页岩风化特征、阐明其环境效应的关键。故黑色页岩风化的元素活动性研究一直是黑色页岩风化研究的核心议题。本文从元素分析和逐级提取实验分析的角度,进一步探讨黑色页岩风化的元素活动性规律。取得如下研究结果和认识。新鲜黑色页岩比风化黑色页岩更富集Cu、V、Ni、Pb、Cd、U、Mo、Ba等重金属;新鲜与风化岩石中都亏损Mn、Co;Zn、Th在新鲜与风化岩石中无明显差异。高场强与大离子亲石元素（除Sr外）,在新鲜和风化岩石中的元素组成无显著差异。风化岩石比新鲜岩石更亏损稀土元素,且更亏损重稀土元素。Mn、Cd、REE等元素在风化过程中主要赋存形态为铁-锰氧化物结合态,其次为活化态,在风化过程中具有较强活动性,对环境影响较大。Cu、Zn主要以铁-锰氧化物结合态存在,对氧化还原环境较为敏感。质量迁移系数表明Ba、Cd、U、Mo、Ni等元素的活动性强,随风化程度增大其淋滤释出增加;V、Pb、Zn既存在相对富集又有淋滤释出,活动性中等;Co、Cu、Th、Ti、Zr、Hf、Nb、Ta、Ga、Ge、Rb、Cs等元素在黑色页岩风化过程中较为稳定,不易淋滤释出,活动性较弱,可能与硅酸盐矿物结合在一起;稀土元素总体迁出能力较强,活动性较强,且轻稀土的活动性较重稀土弱。利用逐级提取实验与质量迁移系数两种方法对Mn活动性判断不太一致,推断Mn的活动性较为复杂。地累积指数计算显示黑色页岩土壤存在Mo、Cd、U、Ba等重金属污染,污染程度依次降低。并估算了单位质量重金属Ba、Mo、U、Cd等元素在黑色页岩风化过程中具体的释放量,结果显示活性较强的元素对周围环境的威胁较大,特别是黑色页岩风化过程中重金属对环境质量的影响不容忽视。更多还原

【Abstract】 The black shale is a kind of sedimentary rock with particularly chemical properties,which formed under a marine anoxic condition,and thus was generally enriched in organic matter and sulfide minerals.Thus,black shale is prone to be weathered and decomposed when exposing to the earth’s surface where it is frequently affected by the atmosphere and water.The black shales weathering can cause the exhalation of CO₂,the production of the acidic mine drainage,and the release of heavy metals such as Cd,Cu,Pb,Zn,and others.Therefore,the black shales weathering can cause many kinds of environmental issues,among which the heavy metal contamination of soil and water systems is one of the most serious,which can cause heavy metal contamination to environment（soil and water,etc.）.Thus,the study on black shales weathering and its environmental impacts has received special attention.The elements mobility during black shale weathering is the key to characterize the weathering characteristics of black shale and clarify its environmental impacts.Therefore,it has always been the core topic of black shale weathering research.This paper explores furtherly the elements mobility of black shales weathering from the perspective of element analysis and sequential extraction analysis.The research results and findings are as follows.The fresh black shales were more enriched in heavy metals such as Cu,V,Ni,Pb,Cd,U,Mo and Ba than weathered black shales.Both of Mn and Co were depleted in fresh and weathered black shales.And it was no significant difference for Zn and Th between fresh and weathered black shales.Meanwhile,High field strength elements or large ionic lithophile elements（except Sr）,which did not differ significantly in elemental composition between fresh and weathered rocks.The weathered black shales were deficient in HREE than in fresh black shales.The main occurrence of Mn,Cd and REE during weathering process was iron-manganese oxide bonding fraction,followed by activation fraction,which had strong mobility during weathering process and a great impact on environment.Cu and Zn mainly existed in the iron-manganese oxide fraction and were sensitive to the reduction conditions.The mass transfer coefficient indicated that the Ba、Cd、U、Mo、Ni and Sr were more active and the leaching release increases with the increase of weathering degree.V,Pb and Zn were relatively enriched and leached,with moderate mobility.Co,Cu,Th,Ti,Zr,Hf,Nb,Ta,Ga,Ge,Rb and Cs with weak mobility were not easy to leach out and might be combined with silicate minerals.The mobility of REE was relatively strong while it was weaker for LREE than HREE.The judgement about the mobility of Mn was not inconsistent by two methods such as the sequential extraction,mass transfer coefficient,so we inferred the mobility of Mn was complicated.The evaluation of geo-accumulation index showed there was heavy metals pollution by Mo,Cd,U and Ba,etc.And the specific release of elements such as Ba,Mo,U and Cd per unit mass in black shales weathering was estimated.The results showed that the active elements were a threaten to the environment,especially the impacts of heavy metals on environmental quality.更多还原