云南不同成土母质土壤剖面中重金属元素地球化学行为与风险分析

发布时间：2018-07-09 22:25

本文选题：成土母质 + 重金属　；参考：《中国地质大学(北京)》2016年硕士论文

【摘要】：《全国土壤污染状况调查公报》指出,我国西南、中南地区土壤重金属超标范围较大。云南省地处中国西南边陲,成土母质类型多样,不同成土母质成壤过程中重金属元素具有明显不同的地球化学行为。本文以云南滇中地区碳酸盐岩、泥页岩、冲积物三种不同成土母质7条土壤剖面为研究对象,通过对风化成土剖面中常量元素和重金属元素及形态含量的地球化学分析,讨论了不同成土母质风化成土过程中控制重金属元素地球化学行为的主要因素,初步分析了不同成土母质区土壤重金属的潜在生态风险。不同成土母质中元素含量与母岩平均值相比较可以得出,碳酸盐岩风化成土剖面中常量元素K、Al、Fe、Si含量相对富集,Na、Ca、Mg明显流失,As、Cd、Hg、Pb、Se呈现普遍次生富集的特征。泥页岩成土母质常量元素在风化成壤过程中,Al、Fe、Si含量相对富集,K、Na、Ca、Mg呈现相对流失,As、Pb、Se、Hg略有富集的特征,而Cd大量流失。冲积物风化成土剖面中K、Ca、Mg、Al、Fe含量相对富集,Na、Si相对流失,As、Cd、Hg、Pb呈现普遍次生富集的特征。不论何种成土母质,在炎热、潮湿气候环境下,由于强烈的化学风化作用和成壤作用,Na普遍流失,Al和Fe富集。Na的流失程度表现为泥页岩冲积物碳酸盐岩,Al和Fe的富集程度表现为碳酸盐岩冲积物泥页岩。重金属元素在不同成土母质富集—贫化呈现不同特征。碳酸盐岩风化成土剖面As、Cd、Hg、Pb的富集程度明显大于冲积物风化成土剖面。同一成土母质同一成壤演化过程,不同重金属元素的富集程度也存在显著差异。碳酸盐岩风化成土剖面中,重金属元素的富集程度表现为AsPbHgCd,泥页岩中HgPbAsCd,冲积物中表现为CdAs=HgPb。碳酸盐岩、泥页岩和冲积物三种不同成土母质发育土壤中,As、Pb主要以残渣态形式为主,其次为腐殖质态和铁锰氧化物态。Cd在碳酸盐结合态、腐殖酸结合态和铁锰氧化物结合态分配比例高于其它形态。腐殖酸结合态、强有机态和残渣态Se、Hg是土壤中Se和Hg的主要存在形态。不同成土母质土壤剖面中As、Cd、Hg、Pb、Se的离子交换态、碳酸盐结合态、腐殖酸态及铁锰氧化物结合态大部分受全量、pH和Corg的影响,但水溶态含量高低可能与成土母质无关,主要受土壤的环境条件所控制。碳酸盐岩、泥页岩和冲积物风化成土剖面中,水溶态、离子交换Cd均在近地表富集,可被植物直接吸收利用,其潜在生态风险不容忽视。推测三种不同成土母质中作物Cd的超标风险顺序为:碳酸盐岩区冲积物区泥页岩区。虽然水溶态As含量和占总量的百分比总体不高,但对泥页岩和冲积物成土母质地区的土壤而言,作物As的超标风险仍有待进一步评价。
[Abstract]:The National soil pollution investigation Bulletin pointed out that the range of heavy metals exceeded the standard in the southwest and middle south of China. Yunnan Province is located in the southwestern border of China. There are various types of soil parent material, and the heavy metal elements have different geochemical behaviors in the process of soil formation of different soil-forming parent materials. In this paper, seven soil profiles of carbonate rock, shale and alluvial materials in central Yunnan are studied. The geochemical analysis of the contents of major elements and heavy metal elements and their speciation in weathered soil profile is carried out. The main factors controlling the geochemical behavior of heavy metal elements in the weathering process of different parent materials were discussed, and the potential ecological risks of heavy metals in different parent material areas were preliminarily analyzed. Compared with the average values of parent rocks, it can be concluded that the relative enrichment of K _ (Aln) Al _ 2O _ (Fe) Si in the weathering soil profile of carbonate rocks is characterized by a general secondary enrichment of Na _ (+) Ca ~ (2 +) mg ~ (2 +). In the process of weathering and forming soil, the relative enrichment of K ~ (2 +) ~ (2 +) Na ~ (2 +) ~ (2 +) Ca ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) in In the weathering profile of alluvium, the relative enrichment of K _ (Ca) Ca ~ (2 +) mg ~ (2 +) Al ~ (2 +) Fe ~ (2 +) and the relative loss of Na ~ (2 +) Si ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) ~ Whatever the parent material, in hot, humid climates, As a result of strong chemical weathering and soil forming action, the loss of Na and Fe enriched Al and Fe generally showed that the enrichment degree of carbonate rock, Al and Fe in mudstone alluvium was that of carbonate rock alluvial mud shale, and the loss degree of Na was that of carbonate rock alluvial shale. The enrichment and dilution of heavy metals in different parent materials of soil showed different characteristics. The enrichment degree of HgPb in weathering soil profile of carbonate rock is obviously higher than that in alluvial weathering section. There are significant differences in the enrichment of heavy metals among the same parent material and the same soil forming process. In the weathering profile of carbonate rock, the enrichment degree of heavy metal elements is AsPbHgCdd1, HgPbAsCdCdin shale and HgPb in alluvium. In carbonate rock, mud shale and alluvial soil, the residual form of As-Pb is mainly in the form of residual, followed by humus and ferromanganese oxide. CD in carbonate bound state. The distribution ratio of humic acid bound state and iron manganese oxide bound state is higher than that of other forms. The main forms of se and Hg in soil are humic acid bound, strong organic state and residual se Hg. The ion exchange state, carbonate bound state, humic acid state and iron-manganese oxide binding state in different parent soil profiles are mostly affected by the total pH and Corg, but the water soluble state content may not be related to the parent material. It is mainly controlled by the environmental conditions of the soil. In the weathering profile of carbonate shale and alluvial materials the water-soluble and ion-exchange CD are enriched near the surface and can be directly absorbed by plants and their potential ecological risks can not be ignored. It is inferred that the risk order of crop CD in three different soil-forming parent materials is as follows: carbonate rock area alluvial area mud shale area. Although water soluble as content and percentage of total amount are not high, the risk of crop as exceeding the standard is still needed to be further evaluated for the soil of shale and alluvial soil-forming parent material area.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X53

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