渤黄海典型近岸表层沉积物中重金属和磷的地球化学特征及环境指示

	渤黄海典型近岸表层沉积物中重金属和磷的地球化学特征及环境指示
	庄文
学位类型	博士
导师	高学鲁
	2014-05
学位授予单位	中国科学院研究生院
学位授予地点	北京
学位专业	环境科学
关键词	重金属磷沉积物生态风险莱州湾獐子岛
摘要	环境中的重金属具有毒性、难降解性和生物放大效应等；磷作为一种海洋生物所必需的生源要素，其含量及分布直接影响着全球海洋的初级生产力。重金属污染和磷的研究多年来一直是全球关注的热点问题。研究沉积物中重金属和磷的地球化学行为，对揭示近海环境演变机制及评价和保护近海生态环境有重要的科学意义。本学位论文选择渤黄海典型近岸区域——莱州湾和獐子岛近海表层沉积物中的重金属（As、Cd、Cr、Cu、Hg、Ni、Pb、Zn）和磷为研究对象，系统研究了莱州湾和獐子岛近海表层沉积物中重金属和磷的地球化学分布特征、来源、迁移转化机制、影响控制因素，并评价了沉积物中重金属的潜在生态风险和磷的生物可利用性潜力；另外还对由莱州湾西南部入海的10条河流表层沉积物中的重金属进行了研究。通过上述研究，获得了一系列新的结果和认识：（1）莱州湾表层沉积物中重金属主要来源于河流输入和大气沉降，秋季比夏季有更多的陆源碎屑来源；沉积物重金属受控于粒度、有机质以及铝、铁、锰等的氧化物；各重金属在沉积物中的赋存形态存在显著差异；重金属不同形态间具有一定相互转化能力。研究表明莱州湾西南部入海河流表层沉积物中重金属的含量明显高于莱州湾内的沉积物，莱州湾内黄河口附近表层沉积物重金属含量也较高，因此莱州湾的重金属主要来源于黄河及湾西南部入海河流，其中包括陆源碎屑来源和人类活动来源。As和Cr的自然来源比例相对较高，而其他重金属的人类活动来源较显著。大气颗粒沉降和化石燃料的燃烧是Hg和Pb的另一重要来源。相关分析表明，莱州湾表层沉积物中重金属的含量随沉积物粒径的减小和粘土含量的增加而增加，且与有机质及铝、铁、锰的氧化物含量呈显著正相关，表明重金属的分布受控于沉积类型和沉积模式及其形成的驱动力–物理迁移。夏季与秋季表层沉积物中重金属与环境参数之间的相关分析结果间存在较大差异，这可能是由于经过丰水期后，各种来源的污染物都输入到水环境中，加上人类活动强度的不确定性，造成了两个季节相关分析结果之间出现了差异。与夏季相比，秋季莱州湾表层沉积物重金属含量有小幅增加，并且陆源来源比重上升。从形态分析结果可知，重金属的残渣态占总量的比例最高，说明这些重金属主要为矿物质起源。其中Cd的非残渣态占其总量的比重高于其他重金属，是表层沉积物中最具有生物活性的重金属。然而表层沉积物中Cd总量非常低，很难对生物产生毒性作用。Cr残渣态含量占总量的比例达80%以上，在所研究的重金属中生物活性最低。可还原态及可氧化态的Cd、可氧化态的Cr、可氧化态的Pb有向残渣态转化的趋势；酸可溶态、可氧化态的Zn可以和可还原态发生转化；Cr的酸可溶态与可氧化态之间也可以互相转化，互为来源。（2）各种重金属在莱州湾表层沉积物中的污染程度和生态风险各不相同；部分河流表层沉积物表现为高污染和高生态风险，湾内沉积物总体为无污染或轻微污染及低生态风险。由国家海洋沉积物质量标准和临界效应浓度/必然效应浓度评价标准可知Cr、Cu、Hg、Ni和Zn在部分河流表层沉积物中污染比较严重，海区表层沉积环境状况总体较好。受沿岸化工企业、生活污水、农田灌溉等影响，重金属污染较高的区域主要分布于溢洪河、广利河、小清河、弥河、虞河及堤河的某些区域。另外新、老黄河口、西南近岸和小清河口以及莱州湾中部存在轻微重金属污染。富集因子显示Cd、Cr、Hg、Ni、Zn具有明显的富集，而As几乎无富集。酸可挥发性硫和同步可提取金属的研究表明，除了弥河、堤河的某些区域外，研究区域表层沉积物中均含有足够量的硫化物来结合重金属离子，因此表层沉积物中重金属的毒性普遍较低。而单因子潜在生态风险指数显示Cd、Hg、Zn具有较高潜在生态风险，其他重金属潜在生态风险较低。综合潜在生态风险指数与沉积物质量准则判定的污染较严重的区域比较一致。（3）莱州湾表层沉积物中的磷主要来源于陆源输入，受粒度、有机质以及铝、铁、锰等的氧化物控制比较显著；表层沉积物中潜在的生物可利用性磷含量较低。莱州湾表层沉积物中总磷含量为315.9～582.7 μg g^-1。利用连续提取法提取了6种不同形态的磷，依次为可交换态与松散结合态磷（Ads-P）、铝结合态磷（Al-P）、铁结合态磷（Fe-P）、自生钙磷（Ca-P）、碎屑态磷（De-P）及有机磷（OP）。各形态磷占总磷的顺序为：De-P（66.7%）＞ OP（12.6%）＞ Ca-P（11.9%）＞ Fe-P（6.5%）＞ Ads-P（2.1%）＞ Al-P（0.2%）。河口区附近表层沉积物中磷含量相对较高，且湾西部磷含量高于东部，表明西南部河流尤其是黄河的输入对磷含量的贡献较高。另外，莱州湾中部表层沉积物磷含量较高，这是水动力条件、粒度因素等共同作用的结果。与重金属类似，粒度、有机碳及Al、Fe、Mn的氧化物是沉积物中磷分布的重要控制因素。Al-P主要来源于污染物的排放，De-P主要源于早期成岩作用，两者受上述环境参数的控制不明显。莱州湾表层沉积物中生物可利用性磷包括Ads-P及OP，占总磷的比例为14.7%。可见莱州湾表层沉积物中能重新释放到水体从而被生物所利用的磷占磷总量的比例很低。对于莱州湾此类中国重要的渔业区来说，磷缺乏对海洋初级生产里的限制已经显而易见，如何降低水体中氮的含量，同时增加水体中磷的含量已经成为当务之急。（4）獐子岛近海表层沉积物中重金属主要为自生来源和人类活动来源，陆源碎屑输入贡献较低，该区域总体沉积环境状况良好。表层沉积物中潜在生物可利用性磷占总量的比例高于莱州湾，但总量依然较低。所研究的8种重金属在獐子岛近海的表层沉积物中均未超过国家一类沉积物对应的上限浓度，表明该区域沉积环境质量状况较好。獐子岛近海表层沉积物重金属主要为自然来源，人为活动来源所占比例较低。综合多种风险评估指数的评价结果，Cd具有中高等生态风险，其他重金属为低风险或无风险。养殖区附近生态风险相对较高，潮间带几乎无生态风险。表层沉积物中Cr、Cu和Ni的含量分布明显受有机物质和粒度的控制；而Cd和Hg含量分布受粒度影响比较显著。所有重金属都与Al、Fe、Mn氧化物的含量无显著相关性，表明该区域重金属的陆源碎屑来源所占比例较低，且与Fe、Mn氧化物的亲和性不高。獐子岛近海表层沉积物中总磷浓度为81.3～401.3 μg g^-1。各形态磷占总磷百分含量的顺序为：De-P（49.5%）＞ OP（19.7%）＞ Fe-P（13.7%）＞ Ca-P（11.3%）＞ Ads-P（4.5%）＞ Al-P（1.3%）。表层沉积物中人类活动来源及河流输入来源对磷的贡献较小，磷含量明显低于莱州湾。獐子岛近海表层沉积物生物可利用性磷同样包括Ads-P及OP，占总磷的24.2%。可见獐子岛表层沉积物中能重新释放到水体从而被海洋生物所利用的磷占总磷的比例不高，磷缺乏可能对獐子岛海区海洋初级生产力具有限制作用。
其他摘要	Heavy metals in the environment are toxic, non-biodegradable and easy to accumulate and magnify in organisms; as an important biogenic element in the ocean, phosphorus (P) directly affects the primary productivity of the ocean. Heavy metal pollution and phosphorus cycling have been hot issues all over the world for many years. Studies on the geochemical behavior of heavy metals and phosphorus in sediments have great scientific significance for the revelation of the evolvement mechanism of coastal environment and the evaluation and protection of coastal ecological environment. In this study, heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) and P in surface sediments from the Laizhou Bay and the coastal Zhangzi Island which were typical nearshore areas of the Bohai Sea and the Yellow Sea, respectively, were analyzed; Geochemical distribution characteristics, sources, transport processes, controlling factors of heavy metals and P, potential ecological risks of heavy metals and potential biological availability of P were systemically studied. In addition, heavy metals in surface sediments from ten major surrounding rivers in the southwestern Laizhou Bay were also analyzed. A series of results and viewpoints were presented as follows: (1) Heavy metals in surface sediments of the Laizhou Bay were mainly from river inputs and atmospheric precipitation; the concentrations of heavy metals appeared to be influenced by the grain size composition of the sediments, the amount of organic matters, and oxides of Al, Fe and Mn; fractional characteristics of metals were different from each other; different forms of heavy metals had the ability to transform mutually. Total concentrations of heavy metals in riverine sediments were much higher than in marine sediments, and the relatively higher concentrations of metals were also detected near to the Yellow River mouth. So heavy metals in surface sediments of the Laizhou Bay were mainly from the Yellow River and the rivers flowing into the southwestern Laizhou Bay, and the sources included terrigenous detrital and anthropogenic sources. The proportion of As and Cr of natural sources was relatively higher, and anthropogenic sources of other heavy metals were obvious. Atmospheric particle sedimentation and burning of fossil fuels were other important sources of Hg and Pb. Correlation analysis showed that the concentrations of heavy metals increased with the decrease of sediment particle size and the increase of clay content, and had significant positive correlations with organic matter content and contents of Fe, Mn and Al oxides, suggesting that the distributions of heavy metals were controlled by the sedimentary types, sedimentary model and the dominant driving power affecting the sediment transportation and distribution. Results of correlation analysis among heavy metals and enviromental parameters between summer and autumn had large differences, which could be caused by the inputs of pollutants of various sources during the rainy season, and the uncertainty of human activity intensity. Comparing with summer, in autumn heavy metal contents in surface sediments of the Laizhou Bay increased slightly, and the proportion of terrigenous sources rose. Metal fractionation analysis showed that the residual fraction was the most dominant one for all the studied metals, indicating these metals had a paramount mineralogical origin. Cd had the highest percentages of the acid soluble fraction among the studied metals which indicated it was the most bioactive metal. But Cd might unlikely be harmful to human and ecological health due to the very low total concentrations. Proportion of residual fraction for Cr was the highest of all the studied metals (>80%), so it had the lowest bioactivity. The reducible and oxidizable Cd and the oxidizable Cr and Pb showed a tendency of transforming to their residual states. The acid soluble and oxidizable Zn was interchangeable with its reducible fraction. The acid soluble Cr could be interchangeable with its oxidizable fraction. (2) Each metal showed different pollution status and ecological risk level from others in surface sediments of the Laizhou bay; some riverine sediments suffered high pollution and ecological risk from heavy metals; Overall, surface sediments inside the Laizhou Bay were pollution-free or slightly polluted and had low ecological risk. Based on the marine sediment quality of China and threshold effects level – probable effects level (TEL – PEL), pollution caused by Cr, Cu, Hg, Ni and Zn in some riverine surface sediments was serious, and surface sediments of the marine region were in good condition. The relatively higher concentrations of metals were mainly recorded in the Yihonghe River, the Guanglihe River, the Xiaoqinghe River, the Mihe River, the Dihe River and the Yuhe River, which was caused by industrial wastewater, sewage runoff and agricultural activity from the coast. In addition, relatively higher concentrations of metals were also recorded near to the new and old mouths of the Yellow River, and in the southwest coastal area, the Xiaoqinghe River, and the middle of the Bay. The results of enrichment factor (EF) indicated that Cd, Cr, Hg, Ni and Zn were obviously enriched in surface sediments of the Laizhou Bay, and As had no enrichment. According to the acid volatile sulfides – simultaneously extractable metals (AVS–SEM) guideline, except in some sites of the Mihe River and the Dihe River, sulfide ions were in sufficient quantities to combine with the divalent metal ion in surface sediments, so the generation of acute toxicity was less possible. According to the monomial potential ecological risk factor, Cd, Hg and Zn showed high potential ecological risk, and the potential ecological risk of other metals was low. The areas with high potential ecological risk determined by the potential ecological risk index were the same with the sediment quality guidelines. (3) Phosphorus in surface sediments of the Laizhou Bay were mainly from continental input, and were mainly controlled by the sediment grain size composition, the amount of organic matters, and oxides of Al, Fe and Mn; the potential bio-available P accounted for only a small part of sedimentary P pool in surface sediments. Contents of total P (TP) in surface sediments of the Laizhou Bay were 315.9~582.7 μg g^-1. Six different forms of P were separated by employing a sequential extraction technique: exchangeable or loosely sorbed phosphorus (Ads-P), aluminum-bound phosphorus (Al-P), iron-bound phosphorus (Fe-P), authigenic apatite plus CaCO₃-bound phosphorus plus biogenic apatite (Ca-P), detrital apatite plus other inorganic phosphorus (De-P) and organic phosphorus (OP). The average percentages of various geochemical forms of P in surface sediments were in the order: De-P (66.7%) > OP (12.6%) > Ca-P (11.9%) > Fe-P (6.5%) > Ads-P (2.1%) > Al-P (0.2%). Relatively higher levels of TP content were observed near to the river mouths. TP content in the west of the Bay was higher than in the east, reflecting the influence from the rivers in the west especially the Yellow River. In addition, high content of TP was also observed in the central part of the Laizhou Bay, which was attributed to the joint effect of the hydrodynamic conditions, particle size factor and so on. P in surface sediments of the Laizhou Bay was mainly controlled by the sediment grain size composition, the amount of organic matters, and oxides of Al, Fe and Mn, which was under similar circumstances with heavy metals. Al-P usually came from the emissions of pollutants, and De-P mainly came from early diagenesis; both of them were not controlled by the aforementioned environment parameters. The bio-available P (Ads-P and OP) accounted for 14.7% of TP in sediments of the Laizhou Bay. Only a small part of P in surface sediments could be released into the overlying water under certain conditions. The Laizhou Bay is an important mariculture area in China, so it is important to reduc the input of nitrogen into its water body and increase the content of P for the primary producers. (4) Heavy metals in surface sediments from the coastal Zhangzi Island were mainly from Authigenic and anthropogenic sources, and contribution of terrigenous detrital sources to this area was at a low level; in general, sedimentary environment in the coastal Zhangzi Island was in good condition. The portion of potential bio-availability P in total phosphorus in the coastal Zhangzi Island was higher than in the Laizhou Bay, but the total quantity was still very low. All the concentrations of the eight studied metals at all the sites of the coastal Zhangzi Island were below the corresponding values of the upper limit for Class I sediment of China, indicating that the sedimentary environment of the coastal Zhangzi Island was in good condition. Heavy metals in surface sediments of the coastal Zhangzi Island were mainly from natural sources and a low proportion were from human activities. The comprehensive results of various risk evaluation indices indicated that Cd showed the highest level of ecological risk, and the ecological risk level of other metals were very low. Ecological risks of heavy metals in culture zones were relatively high, and there were almost no ecological risks in intertidal areas. Content distributions of Cr, Cu and Ni in surface sediments were mainly controlled by grain size and the amount of organic matters; Content distributions of Cd and Hg were mainly controlled by grain size. All metals had no significant correlation with contents of oxides of Al, Fe and Mn, which indicated there was a low ratio of terrigenous detrital sources and these metals had low affinity with oxides of Al, Fe and Mn. TP contents in surface sediments of the coastal Zhangzi Island were 81.3~401.3 μg g^-1. The average percentages of various geochemical forms of P were in the order: De-P (49.5%) > OP (19.7%) > Fe-P (13.7%) > Ca-P (11.3%) > Ads-P (4.5%) > Al-P (1.3%). Contribution from anthropogenic activities and river inputs to P in surface sediments of the coastal Zhangzi Island were small, and P content was obviously lower than that of the Laizhou Bay. The bio-available P in sediments of the coastal Zhangzi Island also included Ads-P and OP, accounting for 24.2% of TP content. There was also only a small part of P in surface sediments of the coastal Zhangzi Island which could be released into the overlying water and used by marine organisms. The deficiency of P could have restrictions on marine primary productivity around the Zhangzi Island.
语种	中文
文献类型	学位论文
条目标识符	http://ir.yic.ac.cn/handle/133337/6799
专题	中国科学院烟台海岸带研究所知识产出_学位论文
推荐引用方式 GB/T 7714	庄文. 渤黄海典型近岸表层沉积物中重金属和磷的地球化学特征及环境指示[D]. 北京. 中国科学院研究生院,2014.

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