射阳海岸现代沉积速率及重金属污染特征

发布时间：2018-04-03 19:01

本文选题：射阳海岸　切入点：~(210)Pb和~(137)Cs定年　出处：《南京师范大学》2015年硕士论文

【摘要】：射阳海岸是江苏中部沿海典型粉砂淤泥质平原海岸,也是近现代快速淤积的海岸之一,其面积广阔且不断淤涨的滩涂是我国东部地区潜力最大、最重要的后备土地资源,它开发与利用能够缓解人增地减矛盾、实现耕地总量动态平衡,满足经济和社会发展对海岸港口资源、土地资源和生物资源的开发提出的更高的要求。同时,近年来人类围垦筑堤等活动影响着海岸的淤涨速度；工业、农业、交通运输、生活和社会活动产生的大量污染物排入河流、湖泊和沿岸海域,致使海岸生态恶化。本文针对射阳海岸动力环境复杂、物质来源丰富等特点,通过采集射阳海岸潮滩柱状样沉积物和挖取剖面,以及对沉积物剖面样品的进行210pb和137Cs测年分析、相互验证并估算射阳海岸沉积速率,确定沉积年代；通过粒度、重矿物及重金属含量测定,多指标分析沉积物质来源、解释沉积速率的变化过程；最后将放射性核素确定的沉积物年代与特定的环境下海岸重金属污染事件相联系,以探明射阳海岸沉积物中重金属的不同沉积时段内分布特征,判别重金属来源、污染历史并初步评价了研究区的重金属污染程度。结果显示：(1)通过放射性核素210pb和137Cs测年法得出210pbex比活度自表层至底层呈现锯齿状波动的阶段性趋势,充分考虑沉积物堆积过程中受人类活动的影响,并得出射阳海岸一百年以来的沉积速的变化过程；结合137Cs的测年结果中存在的几个明显的计年时标：1954年、1963年和1986年蓄积峰,推算出1954年以来海岸沉积速率；210Pb和137Cs结果相互验证,可识别该区域的沉积年代,且确定年代具有可靠性和准确性。(2)根据210pbexCRS计年模型,得出射阳海岸柱芯SY-1和SY-2平均沉积速率分别为1.03 cm/a和2.04cm/a,并以此划分出射阳海岸淤积的四个阶段：A：自然淤涨阶段(1920～1956),沉积速率低且相对稳定；B：淤积调整期阶段(1957年～1990年)海岸沉积物沉积速率出现缓慢上升过程；C：快速促淤期(1991年～2000年),沉积速率迅速增加,增幅最大,受人类活动影响剧烈；D：淤积波动期(2001年～2013年),平均沉积速率最大,呈锯齿状波大幅度波动,受自然因素和人类活动双重作用。(3)根据137Cs测年结果可以计算出柱芯SY-1和SY-2自1954年以来、1963年以来和1986年以来射阳海岸平均沉积速率分别为0.88cm/a和1.69cm/a、0.87cm/a和1.72cm/a、1.13cm/a和2.22cm/a,结果与前人研究基本一致。(4)利用沉积物粒度参数的分析可知,研究区主要以细粉砂和粗粉砂为主,说明射阳海岸主要为细颗粒沉积物堆积区。柱状样剖面从底部向上均表现出先变细再变粗的总体趋势,结合年代推出主要与上世纪80年代末期至90年代初期和本世纪初期大规模垦荒种植、围海养殖等人类活动密切相关。(5)本区重矿物主要为赤褐铁矿、磁铁矿、绿帘石、石榴子石、锆石、金红石、电气石等17种,总体含量普遍较低,均低于1%,随深度的变化相对较小,但大致趋势为由上至下重矿物含量逐渐减少；形态上以柱状为主,仅极少量的云母片状；以稳定矿物为主的重矿物组成,表明该海岸水动力相对较强,物源稳定。其中,不稳定性的角闪石出现在第4层位,表明80～90年代射阳海岸水动力条件稍弱,与该时期沉积物快速淤积相一致。(6)总体来看,沉积物中重金属元素变化趋势相似,除了Cr和Mn元素外,其它重金属元素含量垂向变化为随着深度增加出现先增加后减少、或比较稳定地波动变化；并且在2005和1991左右出现的富集现象与该时段沉积物粒径细化、水动力较弱以及沉积速率加快的变化具有同步性。其中Al、Fe、Zn、Mg、Mn、Ni、Cu、Pb元素主要来自于自然物质风化,而Cr、Hg和As元素的积累主要反映了人类活动的影响。最后运用地积累指数法初步评价得出,除了Hg元素属于轻度污染,其他元素均状况良好。
[Abstract]:Sheyang coast is the central coast of Jiangsu typical silt plain coast, one of the coast is modern rapid siltation, the vast area and continuous siltation beach is the largest potential in the eastern region of China, the most important reserve land resources development and utilization, it can alleviate the increasing population contradiction, realize the dynamic balance of the total arable land and meet the economic and social development of coastal port resources, land resources and biological resources put forward higher requirements. At the same time, the activities of reclamation embankment in recent years affect coastal sediment rate; industry, agriculture, transportation, life and social activities of the large amount of pollutants discharged into rivers, lakes and coastal the sea coast, resulting in deterioration of ecological environment. According to the Sheyang coast complex dynamic environment, rich material source and other characteristics, through the acquisition of Sheyang coastal tidal flat core sediments and digging section, And determined 210Pb and 137Cs on sediment samples, mutual authentication and estimation of Sheyang coast deposition rate, determined by particle size, deposition time; Determination of heavy minerals and heavy metal content, multi index analysis source of sedimentary materials, explain the change of the deposition rate of the process; finally determine the radionuclide ages of sediments and the particular environment under the coastal heavy metal pollution incidents linked, distribution of different sedimentary periods to determine heavy metals in the sediments of the Sheyang coast, distinguishing the sources of heavy metal pollution history, and a preliminary evaluation of the degree of heavy metal pollution in the study area. The results showed that: (1) by radionuclide 210Pb and 137Cs dating method of trend from the surface to the specific activity of 210Pbex the bottom is jagged fluctuations, considering the sediment accumulation under the influence of human activities in the process, and obtains the Sheyang coast one hundred The change process of depositing velocity years; several combined 137Cs dating results in significant annual time scales: 1954, 1963 and 1986 accumulation peak, calculate since 1954 coastal deposition rate; 210Pb and 137Cs results of mutual authentication, which can identify the regional sedimentary years, and determine the age and reliability accuracy. (2) according to the 210pbexCRS model, the average sedimentation rate of Sheyang coastal cores from SY-1 and SY-2 were 1.03 cm/a and 2.04cm/a, and then divided into four stages: the Sheyang coast siltation A: natural silting up stage (1920~1956), low deposition rate and relatively stable; B: sediment adjustment stage (1957 ~ 1990) coastal sedimentary rate slow rise process; C: rapid siltation period (1991 to 2000), the deposition rate increases rapidly, the largest increase, human activities influence sharply; D: deposition The fluctuation period (2001 ~ 2013), the average maximum deposition rate, jagged wave fluctuations, influenced by both natural factors and human activities. (3) according to the 137Cs dating results can calculate the column core SY-1 and SY-2 since 1954, and since 1963 1986 since the average sedimentation rate of Sheyang coast and 0.88cm/a respectively. 1.69cm/a, 0.87cm/a and 1.72cm/a, 1.13cm/a and 2.22cm/a, and the results of previous studies are basically the same. (4) the analysis of sediment grain size parameters show that the study area mainly fine sand and coarse silt, Sheyang coast for fine grain sediment accumulation area. The column sample section from the bottom to show the first thinning change trend of crude, with the launch of the main and the last century, the late 80s to early 90s and the beginning of this century large-scale cultivation, aquaculture reclamation and other human activities are closely related. (5) the heavy Minerals are mainly magnetite, hematite and limonite, epidote, garnet, zircon, tourmaline, Jin Hongshi, 17, the overall content is generally low, lower than 1%, relatively small changes with depth, but the general trend is from top to bottom heavy mineral content gradually reduced; form in columns, only a few mica flake; heavy minerals in stable minerals composition, shows that the coastal water power is relatively strong, stable source. Among them, amphibole instability appeared in fourth layers, that 80~90's Sheyang coast hydrodynamic condition is weaker, with the period of rapid siltation of sediment is consistent. (6) overall, the trend of heavy metals the change in sediment is similar, except for Cr and Mn elements, other heavy metal elements in vertical change with the increase of the depth first increased and then decreased, or relatively stable fluctuations; and in the 2005 and 1991 or so Now with the time accumulation of sediment grain size refinement, with the simultaneous changes and weak hydrodynamic deposition rate. The Al, Fe, Zn, Mg, Mn, Ni, Cu, Pb elements are mainly from natural weathering material, while Cr, Hg and As elements accumulation mainly reflects the influence of human activities finally. The geoaccumulation index was used to preliminary evaluation, in addition to the Hg elements belong to light pollution, other elements are in good condition.

【学位授予单位】：南京师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P736.21;X55

【参考文献】