基于海湾沉积物重金属有效态的文蛤生物标志物筛选与生态毒性评价

发布时间：2018-09-14 07:34

【摘要】：海洋沉积物中不同形态重金属的化学稳定性、迁移转化速度和生物可利用性和潜在毒性存在很大差异，，所以仅从重金属总量进行分析难以有效评价重金属的对底栖生物的生态毒理学效应。目前，针对沉积物重金属赋存形态的生物毒性研究多集中在生物富集与致死效应方面。分子生物标志物能够快速有效地反映污染物与细胞靶分子的相互作用及其后果，且具有灵敏度高、成本低等优点。然而，以往利用生物标志物评价沉积物重金属生态毒性评价研究，均以沉积物重金属总量为基础。未见有对亚致死条件下沉积物重金属赋存形态与生物标志物关系的研究报道。本研究在北部湾沿岸的港口区、养殖区、排污区等功能区设置11个站位，采集表层沉积物并测定其中7种重金属（Hg、As、Cu、Pb、Zn、Cd、Cr）各赋存形态（弱酸溶解态、可还原态、可氧化态、残渣态）的含量、总有机碳、粒径等因子，以及同步测定的底栖双壳类动物文蛤(Meretrix meretrix)鳃和内脏中各12种生化指标：超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、谷胱甘肽过氧化物酶（GPx）、谷胱甘肽硫转移酶（GST）、硫代巴比妥酸反应物（TBARS）、还原型谷胱甘肽（GSH）、氧化型谷胱甘肽（GSSG）、金属硫蛋白（MTs）、乙酰胆碱酯酶（AChE）、氧化型与还原型谷胱甘肽比值（GSH/GSSG）、总谷胱甘肽（tGSH）、氧化逆境指数（OSI）。在分析沉积物中各种重金属总量及其赋存形态含量分布特征基础上，通过文蛤生化指标与沉积物中重金属总量和有效态的相关性分析，分别确定对重金属总量、有效态具有敏感响应的生化指标，由此筛选出2套用于指示研究区域重金属生态毒性的生物标志物组合，然后，分别计算可反映环境损害生物学响应机制的综合生物标志物响应（IBRv2）指数，并对比其灵敏性和可靠性，确定有效的指标体系，建立基于生物效应的北部湾潮间带沉积物重金属综合生态毒性评价模式。进而对有效态重金属用于生物标志物筛选及生态毒性评价的效果进行评估。所得到的主要结论如下：（1）北部湾潮间带沉积物中重金属的有效态含量空间分布与总量分布基本一致（Cr除外），但个别站位有明显差异。各站位沉积物7种重金属中，Cr、Hg和As以残渣态为主要存在形态，Cd以有效态为主。有6个站位Pb、Zn和3个站位Cu以有效态为主，其余站位这3种重金属均以残渣态为主。有效态Hg、Cd和Cr的分布受沉积物中细颗粒和有机质含量的影响，而各重金属总量分布与沉积物物理化性质无明显关系。依据沉积物重金属形态的传统化学评价结果不尽一致，且均未充分考虑重金属的生物学效应以及污染物的综合作用。（2）文蛤鳃和内脏中的生化指标对沉积物重金属的响应规律及敏感性因其种类、形态而异，存在明显的组织差异性和空间差异性。生化指标对重金属有效态的响应敏感性高于总量。与重金属总量相比，其有效态含量能更好地反映沉积物的生物毒性效应。文蛤谷胱甘肽抗氧化系统对多种重金属的有效态有敏感响应，适于作为沉积物重金属污染的生物标志物。（3）依据生化指标对沉积物中重金属总量的响应关系，筛选得到的生物标志物组合为：GSHg/GSSGg、OSIg、TBARSg、GSTv、GSHv、GSHv/GSSGv（g、v分别代表鳃、内脏），依据生化指标对沉积物有效态响应筛选出的生物标志物组合为：GSHg/GSSGg、OSIg、GSTg、GSSGg、CATg、GSTv。与依据重金属总量筛选出的生物标志物组合相比，基于有效态筛选得到的生物标志物组合具有更高的灵敏度和可信度，以其计算的综合生物标志物响应指数（IBRv2A）对海湾沉积物重金属综合毒性的指示效果优于前者（IBRv2T）。IBRv2A评价结果显示，北部湾潮间带各站位沉积物重金属的综合生态毒性大小顺序为：S5（营盘渔港） S1（流沙湾） S6（西场镇海岸） S8（鹿耳环江） S10（防城港西湾） S9（防城港东湾） S7（犀牛角海岸） S3（乐民镇海岸） S4（铁山港） S11（月亮湾） S2（江洪镇海岸）。（4）在对沉积物重金属生态毒性评价时，运用基于有效态重金属筛选建立的综合生物标志物指数法，较传统风险评价方法更能反映沉积物重金属的生态毒性效应，且具有灵敏可靠、方便快速和低成本等优点及良好的应用前景。
[Abstract]:The chemical stability, migration and transformation rate, bioavailability and potential toxicity of different forms of heavy metals in marine sediments are very different, so it is difficult to evaluate the ecotoxic effects of heavy metals on benthic organisms by analyzing the total amount of heavy metals. Most studies focus on bioaccumulation and lethal effects. Molecular biomarkers can quickly and effectively reflect the interactions between pollutants and cell targets and their consequences. They have the advantages of high sensitivity and low cost. There is no report on the relationship between the occurrence of heavy metals and biomarkers in sediments under sub-lethal conditions.
In this study, 11 stations were set up in the harbor area, aquaculture area and sewage discharge area along the Beibu Gulf coast. Surface sediments were collected and the contents of seven heavy metals (Hg, As, Cu, Pb, Zn, Cd, Cr) in different forms (weak acid soluble, reducible, oxidizable, residual), total organic carbon, particle size and benthic amphibians were determined simultaneously. 12 biochemical indices in the gill and viscera of Meretrix Meretrix were superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione sulfotransferase (GST), thiobarbituric acid reactant (TBARS), reduced glutathione (GSH), oxidized glutathione (GSSG), metallothionein (MTs), respectively. Acetylcholinesterase (AChE), GSH/GSSG, total glutathione (tGSH), oxidative stress index (OSI). Based on the analysis of the distribution characteristics of heavy metals in sediments and their occurrence forms, the correlation between the biochemical indexes of Meretrix Meretrix and the total and available forms of heavy metals in sediments was analyzed. Two sets of biomarker combinations were selected to indicate the ecological toxicity of heavy metals in the study area. Then, the comprehensive biomarker response (IBRv2) index reflecting the biological response mechanism of environmental damage was calculated and its sensitivity and reliability were compared. The main conclusions are as follows:1. To establish an effective index system and establish a comprehensive ecological toxicity assessment model of heavy metals in the intertidal sediments of the Beibu Gulf based on biological effects.
(1) The spatial distribution of available heavy metals in the intertidal sediments of the Beibu Gulf is basically the same as that of the total amount of heavy metals (except Cr), but there are obvious differences in individual stations. Among the seven heavy metals in the sediments of each station, Cr, Hg and As are mainly in residual form, Cd is mainly in effective form, Pb is dominant in six stations, Zn and Cu is dominant in effective form in three stations, and the rest are dominant in effective form. The distribution of available Hg, Cd and Cr is affected by the content of fine particles and organic matter in sediments, but the total distribution of heavy metals has no obvious relationship with the physical and chemical properties of sediments. Biological effects and the combined effects of pollutants.
(2) The biochemical indices in the gill and viscera of Meretrix Meretrix were sensitive to heavy metals in sediments because of their species and morphology, and there were obvious differences in tissue and space. The biochemical indices were more sensitive to the available heavy metals than the total amount of heavy metals. Compared with the total amount of heavy metals, the content of the available metals in the gill and viscera of Meretrix Meretrix meretrix could better reflect the sediment The glutathione antioxidant system of Meretrix Meretrix is sensitive to the available state of many heavy metals and is suitable for biomarkers of heavy metal pollution in sediments.
(3) According to the response of biochemical indexes to the total amount of heavy metals in sediments, the selected biomarkers were GSHg/GSSGg, OSIg, TBARSg, GST v, GSHv, GSHv/GSSGv (g, V respectively represent gill and viscera). According to the biochemical indexes, the selected biomarkers were GSHg/GSSGg, OSIg, GST g, GSSGg, CATg, GST, GST. V. Compared with the biomarker combinations screened according to the total amount of heavy metals, the biomarker combinations based on the available state screening have higher sensitivity and reliability. The comprehensive biomarker response index (IBRv2A) calculated by IBRv2A is better than the former (IBRv2T). The results showed that the order of the synthetical ecological toxicity of heavy metals in the intertidal sediments of the Beibu Gulf was S5 (Yingpan Fishing Harbor) S1 (Liusha Bay) S6 (Xichangzhen Coast) S8 (Luer Huanjiang Coast) S10 (Fangcheng Harbor West Bay) S9 (Fangcheng Harbor East Bay) S7 (Rhino Cape Coast) S3 (Lemin Town Coast) S4 (Tieshan Harbor) S11 (Moon Bay) S2 (Jianghongzhen Coast).
(4) When evaluating the ecological toxicity of heavy metals in sediments, the comprehensive biomarker index method based on the screening of available heavy metals can better reflect the ecological toxicity of heavy metals in sediments than the traditional risk assessment method, and has the advantages of sensitivity, reliability, convenience, rapidity and low cost, and has a good application prospect.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：X55;X826

【参考文献】