【作者】 宋明义；

【导师】 周涛发；

【作者基本信息】 合肥工业大学 ， 矿物学岩石学矿床学， 2009， 博士

【摘要】 随着黑色岩系中石煤等矿产资源被广泛地开发利用,赋存其中的重金属和稀散元素在表生条件下释放出来,对生态环境造成严重的破坏和潜在威胁,已引起政府和众多研究者的广泛关注。浙西地区广泛分布着下寒武统黑色岩系,丰富的石煤、黄铁矿、磷块岩等矿产资源被开采利用,已有数百年的历史。因此,研究矿化黑色岩系在开采和表生作用过程中元素的释放迁移、转化对土壤环境造成的深刻影响,为土地科学利用和提高当地居民的健康水平,具有重要的意义。本文通过大量和细致的野外工作和室内分析研究,对西石煤矿山废煤堆、矿坑废水、土壤、农作物等的环境地球化学以及对东带龙游、诸暨地区和西带安吉、开化地区等代表性石煤矿山风化剖面的特征进行研究,揭示了Hg、Cd、Cr、Pb、Ni、As、Cu、Zn等重金属以及有益元素硒在矿山废煤堆的释放、迁移和转化规律,重金属在土壤剖面各层次的赋存形态和生物活性,研究了重金属和硒元素在废煤堆、地表水、沉积物和土壤中的空间分布特征,系统分析和评价了石煤矿山开采给浙西地区带来的环境影响,并对石煤中硒的迁移规律以及富硒土壤的形成机制进行了深入的探讨,建立了重金属和硒在不同介质中的释放、迁移和转化模式。在风化剖面上,与新鲜石煤成分相比,西带SiO₂、Al₂O₃、K₂O、Na₂O、TFe₂O₃变化不大,MnO在表层明显减少;东带风化剖面显示出SiO₂在表层发生富集,K₂O在中间层发生富集,CaO、MgO在中间层富集和在表层亏损十分明显。在不同的剖面上,Mn、Co、Mo的富集达到最高,部分元素REE、Cr、Cu、Th、Pb、Ba以及Ti也有一定的富集。其中以Mo最为典型,在各个剖面上的富集都是很高的。研究表明,常量元素在岩—土界面之间变化明显,表明风化淋溶作用常量元素的减少主要发生在岩—土界面附近。浙西地区黑色岩系微量、稀土元素的地球化学特征明显,主要表现在:①Sr/Ba0.00427-0.041,Co/Ni在0.054-0.371,均＜1,P₂O₅与Y、La-Ce、U-Th以及Co/Zn-（CO+Ni+Cu）等关系图均显示正常海水和热水混合的沉积特征;②不同地区风化剖面自下而上,从弱风化层到强弱风化层直至表土层,∑REE逐渐升高,向上迁移明显,表现出较强的表层富集能力。③从稀土模式上可以看出,上述三个碳质硅质岩剖面LREE/HREE＞1,稀土元素北美页岩的标准化配分模式表现为左倾,轻稀土元素表现为中度富集;而球粒陨石标准化配分模式则出现明显右倾,轻稀土相对于重稀土表现为富集,反映了典型的热水沉积稀土元素配分模式。不同剖面的稀土数据在球粒陨石标准化和北美页岩标准化的分布型式,均表现出较好的一致性,说明具有相同的沉积环境和密切的成因联系。淋溶实验研究发现,大多数重金属淋溶初始阶段都是快速的,以后随着时间的推移逐渐减慢。其中在酸性条件下Cd、As、Cr、Cu、Zn、Ni滤出率很快达到最高,以后很快减少,尤其是Cd、Zn、Ni起始阶段速度较高,很快地速度便降下来,7天的淋出量分别占淋溶柱对应元素总量的10.40%,9.66%,9.19%;而Hg、Pb滤出速度缓慢,以后逐渐增多,但总量并不高,如Hg的7天淋出量仅占总量的0.11%。Se在碱性条件下7天的滤出量占总量的0.69%,而且随着时间的推移持续升高,具有较大的潜在利用价值。通过对工作区岩相古地理研究,认为造成东西两带富硒土壤pH和土壤地球化学成分差异较大的主要原因是由于东西两带地质背景、沉积环境和沉积相不同。其中西带荷塘期沉积环境属于台沟相,石煤层厚度大,碳酸盐层所占比例较少,石英/粘土比值为0.65,P₂O₅、CaO含量较低,黄铁矿含量高达9.3%;而东带荷塘期沉积环境属于台地相,石煤层厚度小,碳酸盐层夹层较多,石英/粘土比值为0.30,P₂O₅、CaO含量高,黄铁矿含量为4%。风化削面对比研究发现,重金属在剖面上迁移的表现形式,与地形地貌、风化沉积作用等有着密切的联系。在源岩地区,石煤层主要发育风化剖面,富阳、常山、龙游以及诸暨等地石煤矿山风化剖面,重金属元素以迁出为主,表土层多数元素出现贫化,其中以Cd、Zn、Ni的贫化率最为明显,表明这些元素化学性质活泼,在表生条件下迁移性极强,大部分随水、风等介质在重力作用下发生迁移。而在沉积区主要发育土壤剖面,如西带的安吉、开化,东带的龙游等河谷平原黑色岩系风化物堆积区,重金属元素以累积形式为主,与剖面C层相比,Cd、Cu表层富集程度为最高,前者富集系数2.07～9.91,后者0.65～4.74;其次为As、Hg、Ni、Pb、Cr,表层出现富集明显。剖面分析和元素形态分析发现,东、西两带土壤重金属活性组分的含量有较大的差别,具体表现在:（1）西带活性组分含量高,其中Cd的水溶态、离子交换态占总量的46.13%,Ni水溶态和离子交换态占总量的4.48%。重金属含量超标如此严重,Cd、Ni对生态环境应具有较大的危害。（2）东带重金属活性组分低,Cd离子交换态（含水溶态）占总量的17.9%,Ni离子交换态（含水溶态）仅占1.79%,有效态的绝对含量不高,对环境的危害很小。通过土壤地球化学调查和利用高精度测试手段,首次在浙西地区发现大规模的富硒土壤,分布在龙游、安吉、诸暨等地区。该地区土层深厚,质地适中,土壤肥沃,总面积506.8km²。根据现代沉积学理论分析,确认浙西地区富硒区硒主要来源于下寒武统荷塘组黑色岩系。其中东带富硒土壤形成特点:第四系沉积区与源岩风化区距离较远,沉积区为一长条形盆地,土壤类型为潴育型水稻土,呈弱碱性—碱性,土层厚,土壤质地为重壤,Cd、Hg含量为国家土壤环境质量二～三级标准,Ca、Mg、Se含量较高为特征。该区农产品富硒程度高,重金属含量低。西带富硒土壤形成特点:第四系沉积区与源岩风化区距离较近,地形坡度较陡,沉积区为一开放的河谷地带,土壤类型为渗育型水稻土,土层薄,呈弱酸性—酸性,颗粒相对较粗,地球化学以富Cd、Ni、Se、Zn、As、S、Fe,低Ca、Mg为特征。通过系统对比,首次发现,浙西富硒土壤中S、Org.C、CaO、MgO、Cd、Zn、Ni、Hg、As、Se与源区石煤相比具有较高的继承性。其中,S、Org.C、CaO、MgO对土壤的酸碱度和理化性质等具有深刻的影响。安吉富硒土壤中S、Org.C含量仍高于龙游,而龙游土壤中CaO含量仍高于安吉,显示出龙游土壤呈碱性,安吉土壤呈酸性的差别,表明两地区土壤中的氧化物和微量元素等与其源岩地质背景仍有较密切的联系。相关分析发现,在浙西富硒区不同母质、不同类型的土壤中,有效硒含量与土壤pH密切相关;在相同母质和相同类型的土壤中,有效硒含量与土壤硒总量极显著相关。根据因子分析原理,应用最大正交旋转求得该区土壤中指标的最终因子载荷,F₁、F₃分别反映了沉积区富硒土壤中Se与Cd、Cu、Zn以及与MgO的原生共生组合特征。研究发现,龙游富硒区土壤偏碱性,P、Ca、Zn、Mn含量丰富,由于磷酸盐、碱性环境对Se活化的促进作用,Ca、Zn、Mn对Cd的拮抗作用以及碱性环境对Cd的固化作用,使作物根部对Se的吸收增加,对Cd等重金属的吸收大大减少,使得该区农产品成为低镉高硒的天然富硒农产品。而安吉富硒区由于S、Org.C等地质高背景,土壤呈酸性,Se多被土壤粘粒吸附活性较低,加上Ca、Mn含量较低对Cd、Ni拮抗作用不明显,因此,导致农产品中Cd、Ni超标而Se含量相对不高的现象。通过生物地球化学研究,发现东西两带土壤元素的活性组分含量、农产品硒与重金属的含量和生态效应三者之间具有良好的对应关系。其中,西带富硒区稻米中硒含量仅达到富硒临界值,与农业部粮食卫生限量标准值相比,农产品Cd、Ni含量超标严重（Cd 0.26～0.63mg/kg,Ni 0.5～1.0mg/kg）,但同时也达富锌、富硒水平。实地调查发现,当地居民健康状况良好,并未出现“痛痛病”等地方性疾病。由此推断是人体内部Se、Zn对Cd、Ni的拮抗屏蔽作用,影响了人体对Cd、Ni的吸收。相反,东带稻米、莲子等农产品中Se含量高,Cd、Ni低,表现出高硒低重金属的特点。首次在东带发现龙游天然优质富硒大米和富硒莲子。这些农产品硒含量高,重金属在农业部食品卫生限量范围之内,体现出富硒农产品的保健性与安全性的统一。富硒土壤研究成果,经过近年来富硒农产品规模开发利用,已取得巨大的经济效益。长期食用这些农产品的当地居民,表现为精力充沛、健康长寿,发硒含量是正常人发硒0.28mg/kg的1.79～3.75倍。综合上述黑色岩系风化剖面研究、淋溶实验研究、土壤剖面研究以及元素形态分析研究等,表明浙西下寒武统荷塘组黑色岩系地区Cd、Zn、Ni在酸性条件下具有较强的迁移能力,但在碱性环境相对固定;而Se在碱性条件下迁移能力强,在酸性环境较为稳定。根据这一特点,选择相对碱性地区开发富硒土壤,为贫瘠山区生产天然优质富硒农产品提供科学依据。更多还原

【Abstract】 With the exploitation of the stone coal and other mineral resources in black rock series, heavy metals and scattered elements have released from it and the ecological environment has been heavily destroyed, the government and many researchers have paid close attention to it. Lower Cambrian black rock series are widely distributed in the Western Zhejiang, and the exploitation of stone coal, pyrite, phosphorite and other mineral resources has a history of hundred of years. Studying on the soil environment influence of the releasing and migration of elements in the process of the exploitation and hypergenesis of these black rocks will contribute to the utilization of these mineral resources reasonably and also improve the living standard of the local people.Based on the intensive and systematic field and indoor investigations, the characters of the environmental geochemistry of the waste coal stack, waste water of the pit, soil and crops are studied. The characters of representative weathering profiles in the area of Longyou, Zhuji, and Kaihua are also included in this work. In addition, the rules of releasing, migration, and transformation of heavy metals and selenium in waste coal stack as well as the existing form and biological activities of heavy metals in different layers of representative black series profiles are fully investigated. The distribution characteristics of heavy metals and selenium in waste coal stack, surface water, and sediment soils are studied and the environment influences of exploitation of the stone coal are analyzed and evaluated systematically. More over, the migration of selenium in stone coal and the formation of selenium-rich soils are the focus of this work. Models of releasing, migration, and transformation of heavy metals and selenium in different mediums in the study area are established.In the western weathering profiles, compared to fresh stone coal, the content of SiO₂, Al₂O₃, K₂O, Na₂O and TFe₂O₃ don’t have greatly changed, while the content of MnO in the surface layers decreased significantly. In the eastern weathering profiles, Si_O2 is enriched in the surface layer, while K₂O, CaO and MgO are enriched in the middle layers. CaO and MgO are obviously defective in the surface layers. In different profiles, Mn, Co, Mo and Sc have the highest degree of enrichment, and REE, Cr, Cu, Th, Pb, Ba and Ti are also enriched to a certain degree. Mo is the most enriched element in every profile. Decreasing of major elements in rock-soils interface is due to the weathering and eluviation.The geochemical characteristics of trace and rare earth elements in the black rock series of western Zhejiang province are significant in three 3 aspects. 1) The ratios of Sr/Ba and Co/Ni are 0.00427-0.041 and 0.054-0.371, respectively, all less than 1. Correlation figures of P₂O₅-Y, La-Ce, U-Th and Co/Zn-（CO+Ni+Cu） all show that the chemical sediments deposited in these rock series are from mixing of normal sea water and hot water. 2) In different weathering profiles,ΣREE increases gradually from the below to up. And 3) from the distribution pattern of the rare earth elements, we find that in the 3 siliceous rocks profiles mentioned in above paragraphs, LREE/HREE is more than 1. The North American shale normalized REE patterns are aslope to the left with LREE enriched, while chondrite normalized REE patterns are obviously aslope to the left with LREE enriched. This reflects a typical REE pattern of sediments deposited from hot water, the chondrite normalized REE patterns are consistent in different weathering profiles, which indicate that they deposited in the same environment with similar genesis.Based on a series of leaching experiments, we found that most of the heavy metals were leached fast at the beginning, and gradually slowed down as the time past. Especially, in acidic conditions, the leaching rates of Cd, As, Cr, Cu, Zn, and Ni reached the maximum extent quickly, and then decrease quickly. Take Cd, Zn, and Ni elements for example, the leaching rate in seven days are respectively 10.40%, 9.66% and 9.19%. Hg, and Pb leached slowly at first, and then increased gradually, but the total leaching amount is in a low level. The leaching rate of Hg in seven days is 0.11. In alkaline conditions, Se has the higher leaching rate to 0.69% in seven days. Moreover, the leaching rate increased with the time past. This showed the great potential usage for Se.In this research, we found that the pH value and geochemical constituents of soils between the eastern and western Selenium-rich Soil areas have much difference, which are caused by the differences in geological background, depositional environment, sedimentary facies in both regions. The depositional environment of the Hetang formation in the western region was ditch phase unit, so the stone coal layer is thick, and the proportion of carbonate is less. The ratio of quartz/clay of rock is 0.65, and the contents of P₂O₅ and CaO in the rocks are low. The content of pyrite is as high as 9.3%. However, in the eastern region, depositional environment of Hetang formation belonged to the platform phase. The stone coal layer it is thin, and the proportion of carbonate is high. The ratio of quartz/clay is 0.30, and the contents of P₂O₅ and CaO are high. It contains 4% pyrite.The comparative study based on the weathering profiles find that the migration of heavy metal in profiles is relation with topography, geomorphology and weathering sedimentation. In source rock area, the stone coal layers usually produce weathering profiles, such as Fuyang profile, Changshan profile, Longyou profile and Zhuji profile. In these sections, most of the heavy metals move out. The dilution rates of heavy metal are in a high level, especially Cd, Zn and Ni. It shows that these elements are all active, and have the ability of migration in the condition of supergene. They can move with the wind, the water and other media at gravity. In quaternary deposits, there are more soil profiles. In black rock series weathering deposits of river valley, such as Anji and Kaihua in the western, Longyou in the eastern, and heavy metals are accumulation in the surface layer. Take Cd and Cu for example, the enrichment coefficient of the former is from 2.07 to 9.91, and the latter is from 0.65 to 4.74. As, Hg, Ni, Pb and Cr are also accumulation in the surface layer of soil obviously.The active component of heavy metals in the soil are also obviously different between the eastern and the western region: The contents of active component of heavy metals are higher in western region, for example, the contents of water soluble and ion-exchange state of Cd take up 46.13% of the total, and Ni takes up 4.48%. Cd and Ni are greatly hazard on the ecological environment in this region. The contents of active component are lower in the eastern region. The contents of water soluble and ion-exchange state of Cd take up only 46.13% of the total, and Ni takes up only 4.48%. The concentration of the element effective form is not high, which indicate the heavy metals in the rocks are not much harmful to the ecological environment at the present. Based on geochemistry survey also with precise analysis, a large-scale selenium-rich soil distributed area 506.8km² first found in the western Zhejiang, Longyou, Anji, and Zhuji contained. In this area, the soil is thick and fecundity. These selenium-rich soils in the western Zhejiang were from the decay of the Lower Cambrian black rock series. The characters of eastern belt are summarized as follow: There is long distance between quaternary deposits and weathering zone of source rock. The deposit area is a rectangular basin, and the soil belongs to paddy soil, and the layer is thick. The pH changes from weak alkaline to alkaline, and the texture is weight loam. T Cd, Hg content in the soil exceed the national environmental quality standards for 2-3 level, and the content of Ca, Mg, Se are also high. The content of Se in agricultural products is high in this area, but the heavy metals content is low. Western belt has the following characteristics: The quaternary deposit is near to the weathering zone of source rock, and slope is steep. The sedimentation area is an opened river valley. The type of soil is paddy soil, and the layer is thin. The pH changes from weak acid to acid and the particles are coarse relatively. The contents of Cd, Ni, Se, Zn, As, S and Fe are high, but the contents of Ca and Mg are low.Based on the result of comparison, it is first found that, to a great extent, S, Org.C, CaO, MgO, Cd, Zn, Ni, Hg, As, and Se in selenium-rich soil in the western Zhejiang are inherited from the source stone coal, and alkalinity acidity and physicochemical properties in the soil are deeply influenced by S, Org.C, CaO and MgO. The content of S and Org.C in selenium-rich soil is higher in Anji than in Longyou, while the content of CaO is higher in Longyou than in Anji. Moreover, soil in Longyou presents alkaline to weak alkaline, while soil in Anji presents acid. The result shows that oxides and trace elements in the soil of studied area have a close relationship with source rock.According to correlation analysis, in the soil of different parent materials and different types in selenium-rich area of western Zhejiang, we find that the content of effective selenium and pH has a great relationship. In the soil of same parent material and same type, the content of effective selenium and selenium（total） has a great relationship. Based on the theory of factor analysis, we obtain the factor loading of elements in studied soils after varimax rotation. The reslut shows that F1 and F3 reflect the characteristics of paragenetic association of Se and Cd, Cu, Zn and MgO respectively in selenium-rich soil of sedimentary area.The research shows that, the soil presents alkaline, and the content of P, Ca, Zn, and Mn is rich in selenium-rich area in Longyou. Because phosphate and alkaline condition can promote Se activation, and Ca, Zn and Mn can antagonize Cd, the Se absorption of the root of crops increase, while absorption of the heavy metal such as Cd decrease. Therefore, agricultural products in selenium-rich area are higher in selenium and lower in cadmium. However, the content of S and Org.C is high in selenium-rich area in Anji and the soil presents acid. Because of absorption of soil clay, the activation of Se is low. What is more, the antagonism to Cd and Ni is not obvious, because the content of Ca and Mn is low. Therefore, agricultural products are higher in cadmium and nickel and lower in selenium.According to the investigation on crop, the content of elements active component in the . eastern and western region, the content of selenium and heavy metal, and ecological effect has a great relationship. In western area, compared to limited value of food security standards of the Ministry of Agriculture, the content of Cd and Ni exceed seriously（Cd 0.26-0.63mg/kg, Ni 0.5-1.0mg/kg）. However, the crops are also zinc-enriched and selenium-enriched. Based on the field survey, local residents are in good health, and there isn’t any endemic disease such as "itai-itai disease". It is inferred that there are antagonism effects between Se, Zn and Cd, Ni in Human, and absorption of Cd and Ni is less. On the contrary, in the eastern area, the content of Se is high in crops such as rice and lotus seed, while Cd and Ni are low. It is showed that the content of Se is high and heavy metal is low.In this study, natural selenium-rich rice, lotus seed and other selenium-rich crop are found for the first time in the eastern area. The content of Se is high in these crops. Moreover, the content of heavy metal is low and isn’t over standard. This reflects the unity of health and safety in selenium-rich crops. Enormous economic benefits are made by scale development of selenium-rich soil. Local residents who live on these crops for long term are energetic, health and longevity. According to statistics, content of selenium in their hair is 1.79-3.75 times of others.In this thesis, we study on the characters of representative weathering profiles of black rock series in western Zhejiang. We also do some leaching experiments, and study on elemental speciation of profiles. The results showed that in the condition of acid, Cd, Zn, and Ni have strong ability of migration in black rock series of Lower Cambrian Hetang Group in western Zhejiang. However, Se has strong ability of migration in the alkaline condition. According to the research, the development of selenium-rich soil can be chosen in the area where is relative alkaline. And we hope to provide a scientific basis of producing selenium-rich natural and quality of agricultural products in barren mountain.更多还原