长江口颗粒态金属元素分布特征及其影响因素的探究

发布时间：2017-12-27 07:00

本文关键词：长江口颗粒态金属元素分布特征及其影响因素的探究　出处：《华东师范大学》2017年硕士论文　论文类型：学位论文

【摘要】：为了探究不同水情条件下颗粒态金属元素的河口地球化学行为。在长江口洪季(2013年7月)与枯季(2014年1月)共采集34个站位(洪季16个,枯季18个)的表层水样,测定了洪枯季悬浮物中金属含量(包括Al、Fe、Mn、Cr、Co、Ni、Cu、Pb、Zn、Cd和稀土元素)以及金属可提取态组分含量。分析了洪枯季长江口颗粒态金属总量及其非残渣态组分的平面分布特征,结合长江口盐度场、SPM场等不同参数,探讨长江口颗粒态金属元素自淡水端元到口外海域的变化特征以及不同因子对其含量分布的影响。结果表明:(1)无论洪枯季,长江口颗粒态金属含量均呈现带状分布。自口内向外,含量逐渐降低。其中Cu、Pb、Zn、Cd等金属元素分带性相对显著。口外水域颗粒态金属含量分布也呈明显的带状特征,大部分金属含量为南部高、北部低。(2)长江口悬浮物中Cr、Co、Ni三种元素以残渣态为主存在,其中Cr、Ni非残渣态含量占其总量比例不及20%,残渣态组分占据绝对主导。Cu、Zn非残渣态含量占比达30%～40%。Pb、Cd的非残渣态含量占总量比例在55%～65%。可见金属Cu、Pb、Zn、Cd在长江口受人类活动输入影响相对显著。(3)长江口不同区域,颗粒态金属分布控制因素有所不同。口内低盐度区,颗粒态金属含量受SPM浓度影响大,洪季SPM浓度大于枯季,稀释效应相对较强。Cu、Pb、Zn、Cd等金属含量枯季高于洪季,且几种金属的非残渣态组分占比也表现为枯季高、洪季低的特征,其中非残渣态Pb的比例洪枯季分别为51.3%和66.5%,非残渣态Cd的比例洪枯季分别为77.2%和84.9%。可见长江流域向河口的人类活动金属输入存在显著的洪枯季差异。枯季,流域水沙减少,人类活动金属输入影响相对较大。口门高浊度区,Cu、Pb、Zn、Cd等金属含量洪枯季差异小,且几种金属的非残渣态组分占比洪枯季差异不显著。口门高浊度区SPM浓度较口内低盐度区增加了 5～10倍,高浊度区大部分金属含量较低盐度区显著减少,其中Cu含量降幅洪枯季分别为13%和27%;Pb含量降幅洪枯季分别为16%和21%;Cd含量降幅洪枯季分别为57%和73%。流域输入金属经过口门高浊度区,在大量再悬浮泥沙的稀释下,金属总量及其形态的洪枯季差异减小。可见口门高浊度区对入海物质有一定的调制作用。口外高盐度区,随着径流作用的减弱,颗粒物逐渐沉降,Cu、Zn、Cd等金属平均含量继续降低。颗粒态金属含量分布主要受粒度影响,尤其是细颗粒物组分。口外南部水域,颗粒态金属含量及其非残渣态组分含量显著高于高浊度区。从已有的长江口底质沉积物金属分布来看,口外南部水域沉积物中Cu、Pb、Zn、Cd等金属含量较高;再加上长江口三角洲如今以侵蚀为主的沉积环境。泥沙再悬浮影响下,可能是导致表层颗粒态金属"二次污染"的重要因素。相比于Cu、Pb、Zn、Cd等金属含量分布在长江口的区域带状特征,Cr、Co、Ni等以残渣态组分占据绝对主导的金属元素,其总量与形态分布的区域差异相对较小。(4)长江口悬浮物中REEs平均含量洪季为168.32μg/g,枯季为175.18μg/g,含量水平与黄河下游及河口地区沉积物、后太古宙澳洲页岩以及世界河流REEs平均值接近。经北美页岩标准化,其洪枯季配分曲线从La到Lu标准化值均接近于1,说明长江口悬浮物中REEs组成与北美页岩组成相似,伴有轻微的Ce亏损与中等程度的Eu富集。在稀土形态研究中,非残渣态存在明显的MREEs富集,占总含量的19～48%。悬浮物中稀土非残渣态比例显著高于沉积物,很可能与样品类型差异有关。
[Abstract]:In order to explore the estuarine geochemical behavior of granular metallic elements under different water conditions. At the mouth of the Yangtze River flood season (July 2013) and dry season (January 2014) were collected at 34 stations (16 flood season, dry season 18) in the surface water, the metal content of suspended solids in flood and dry season were determined (including Al, Fe, Mn, Cr, Co, Ni, Cu, Pb, Zn, Cd and rare earth elements) and metal extractable fractions. Analysis of areal distribution of flood and dry season in the Changjiang Estuary and its total particulate metal non residual components, combined with the salinity in different parameters field, SPM field and so on, the mouth of the Yangtze River particulate metals from freshwater endmember to change characteristics of Estuary and the influence of different factors on bearing weight distribution. The results showed that: (1) no matter the season of flood and dry season, the content of grain metal in the Yangtze Estuary showed a banded distribution. From the mouth to the outside, the content gradually decreased. The metal elements, such as Cu, Pb, Zn and Cd, have relatively significant zoning. The distribution of granular metal content in the waters of the outside of the mouth is also obviously banded, and most of the metal content is high in the South and low in the north. (2) the three elements of Cr, Co and Ni in the Yangtze Estuary are mainly residues. Cr and Ni account for less than 20% of the total residue content, and residues are dominant. The proportion of non residue in Cu and Zn is 30% ~ 40%. The non residue content of Pb and Cd accounted for 55% to 65% of the total amount. It can be seen that the influence of Cu, Pb, Zn and Cd on the input of human activity in the Yangtze Estuary is relatively significant. (3) the control factors of the distribution of granular metals are different in different regions of the Yangtze River Estuary. In the low salinity area of the mouth, the content of granular metals is greatly influenced by the concentration of SPM, and the concentration of SPM in the flood season is greater than that in the dry season, and the dilution effect is relatively strong. Cu, Pb, Zn, Cd and other metal content in the dry season than that in flood season, and the non residual group of several metal divided accounted for the performance characteristics of the dry season and flood season low, the non residual ratio of Pb in flood and dry season were 51.3% and 66.5%, the proportion of non residual Cd flood season 77.2% and 84.9% respectively. It is obvious that the input of human activity metal in the Yangtze River basin to the estuary has significant difference in the flood and dry season. In the dry season, the water and sediment in the basin decreased, and the influence of human activity metal input was relatively large. The metal content of Cu, Pb, Zn and Cd in the high turbidity area of the mouth gate was small, and the non residue components of several metals accounted for no significant difference in the flood season. The entrance area of high turbidity SPM concentration than in low salinity area increased by 5 ~ 10 times, the high turbidity zone most of the metal content is low salinity area decreased significantly, the content of Cu was in flood and dry season were 13% and 27%; the Pb content decreased in flood and dry season were 16% and 21%; the Cd content decreased in flood and dry season 57% and 73% respectively. As the input metal passes through the high turbidity area of the mouth gate, the difference of the total metal amount and its form in the flood and dry season decreases with the dilution of a large number of suspended sediment. It can be seen that the high turbidity area of the mouth gate has a certain modulation effect on the matter entering the sea. In the high salinity area out of the mouth, with the decrease of runoff, the particles gradually settle, and the average metal content of Cu, Zn and Cd continues to decrease. The distribution of the particle metal content is mainly influenced by the particle size, especially the fine particle composition. The content of granular metal and its non residue composition in the southern waters of the mouth is significantly higher than that in the high turbidity area. According to the distribution of metals in the sediments of the Yangtze Estuary, the contents of Cu, Pb, Zn and Cd in sediments are higher than those in the southern part of the Changjiang River. Under the influence of sediment resuspension, it may be an important factor leading to the "two pollution" of the surface granular metal. Compared with Cu, Pb, Zn and Cd, the distribution of metal content in the Yangtze River estuary is characterized by regional zonal characteristics. Cr, Co, Ni and other residual metal fractions occupy the absolute dominant metal elements, and their total and morphological differences are relatively small. (4) the average REEs content of suspended sediment in the Yangtze River estuary is 168.32 g/g, and 175.18 g/g in dry season. The content is close to the average value of REEs in the lower reaches of the Yellow River and the estuarine sediments, after the Archean Australian shale and the world rivers. The standardized values of dry and dry season partition curves from La to Lu were close to 1 through the standardization of North America shale. The REEs composition of suspended matter in the Yangtze Estuary is similar to that of North America shale, with slight Ce loss and moderate Eu enrichment. In the study of rare earth morphology, there is an obvious MREEs enrichment in the non residue state, which accounts for 19 to 48% of the total content. The proportion of rare-earth non residue in suspended matter is significantly higher than that in sediment, and it is likely to be related to the difference of sample type.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X142

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