發(fā)布時間：2018-09-14 07:34

【摘要】：海洋沉積物中不同形態(tài)重金屬的化學(xué)穩(wěn)定性、遷移轉(zhuǎn)化速度和生物可利用性和潛在毒性存在很大差異，，所以僅從重金屬總量進行分析難以有效評價重金屬的對底棲生物的生態(tài)毒理學(xué)效應(yīng)。目前，針對沉積物重金屬賦存形態(tài)的生物毒性研究多集中在生物富集與致死效應(yīng)方面。分子生物標(biāo)志物能夠快速有效地反映污染物與細(xì)胞靶分子的相互作用及其后果，且具有靈敏度高、成本低等優(yōu)點。然而，以往利用生物標(biāo)志物評價沉積物重金屬生態(tài)毒性評價研究，均以沉積物重金屬總量為基礎(chǔ)。未見有對亞致死條件下沉積物重金屬賦存形態(tài)與生物標(biāo)志物關(guān)系的研究報道。 本研究在北部灣沿岸的港口區(qū)、養(yǎng)殖區(qū)、排污區(qū)等功能區(qū)設(shè)置11個站位，采集表層沉積物并測定其中7種重金屬（Hg、As、Cu、Pb、Zn、Cd、Cr）各賦存形態(tài)（弱酸溶解態(tài)、可還原態(tài)、可氧化態(tài)、殘渣態(tài)）的含量、總有機碳、粒徑等因子，以及同步測定的底棲雙殼類動物文蛤(Meretrix meretrix)鰓和內(nèi)臟中各12種生化指標(biāo)：超氧化物歧化酶（SOD）、過氧化氫酶（CAT）、谷胱甘肽過氧化物酶（GPx）、谷胱甘肽硫轉(zhuǎn)移酶（GST）、硫代巴比妥酸反應(yīng)物（TBARS）、還原型谷胱甘肽（GSH）、氧化型谷胱甘肽（GSSG）、金屬硫蛋白（MTs）、乙酰膽堿酯酶（AChE）、氧化型與還原型谷胱甘肽比值（GSH/GSSG）、總谷胱甘肽（tGSH）、氧化逆境指數(shù)（OSI）。在分析沉積物中各種重金屬總量及其賦存形態(tài)含量分布特征基礎(chǔ)上，通過文蛤生化指標(biāo)與沉積物中重金屬總量和有效態(tài)的相關(guān)性分析，分別確定對重金屬總量、有效態(tài)具有敏感響應(yīng)的生化指標(biāo)，由此篩選出2套用于指示研究區(qū)域重金屬生態(tài)毒性的生物標(biāo)志物組合，然后，分別計算可反映環(huán)境損害生物學(xué)響應(yīng)機制的綜合生物標(biāo)志物響應(yīng)（IBRv2）指數(shù)，并對比其靈敏性和可靠性，確定有效的指標(biāo)體系，建立基于生物效應(yīng)的北部灣潮間帶沉積物重金屬綜合生態(tài)毒性評價模式。進而對有效態(tài)重金屬用于生物標(biāo)志物篩選及生態(tài)毒性評價的效果進行評估。所得到的主要結(jié)論如下： （1）北部灣潮間帶沉積物中重金屬的有效態(tài)含量空間分布與總量分布基本一致（Cr除外），但個別站位有明顯差異。各站位沉積物7種重金屬中，Cr、Hg和As以殘渣態(tài)為主要存在形態(tài)，Cd以有效態(tài)為主。有6個站位Pb、Zn和3個站位Cu以有效態(tài)為主，其余站位這3種重金屬均以殘渣態(tài)為主。有效態(tài)Hg、Cd和Cr的分布受沉積物中細(xì)顆粒和有機質(zhì)含量的影響，而各重金屬總量分布與沉積物物理化性質(zhì)無明顯關(guān)系。依據(jù)沉積物重金屬形態(tài)的傳統(tǒng)化學(xué)評價結(jié)果不盡一致，且均未充分考慮重金屬的生物學(xué)效應(yīng)以及污染物的綜合作用。 （2）文蛤鰓和內(nèi)臟中的生化指標(biāo)對沉積物重金屬的響應(yīng)規(guī)律及敏感性因其種類、形態(tài)而異，存在明顯的組織差異性和空間差異性。生化指標(biāo)對重金屬有效態(tài)的響應(yīng)敏感性高于總量。與重金屬總量相比，其有效態(tài)含量能更好地反映沉積物的生物毒性效應(yīng)。文蛤谷胱甘肽抗氧化系統(tǒng)對多種重金屬的有效態(tài)有敏感響應(yīng)，適于作為沉積物重金屬污染的生物標(biāo)志物。 （3）依據(jù)生化指標(biāo)對沉積物中重金屬總量的響應(yīng)關(guān)系，篩選得到的生物標(biāo)志物組合為：GSHg/GSSGg、OSIg、TBARSg、GSTv、GSHv、GSHv/GSSGv（g、v分別代表鰓、內(nèi)臟），依據(jù)生化指標(biāo)對沉積物有效態(tài)響應(yīng)篩選出的生物標(biāo)志物組合為：GSHg/GSSGg、OSIg、GSTg、GSSGg、CATg、GSTv。與依據(jù)重金屬總量篩選出的生物標(biāo)志物組合相比，基于有效態(tài)篩選得到的生物標(biāo)志物組合具有更高的靈敏度和可信度，以其計算的綜合生物標(biāo)志物響應(yīng)指數(shù)（IBRv2A）對海灣沉積物重金屬綜合毒性的指示效果優(yōu)于前者（IBRv2T）。IBRv2A評價結(jié)果顯示，北部灣潮間帶各站位沉積物重金屬的綜合生態(tài)毒性大小順序為：S5（營盤漁港） S1（流沙灣） S6（西場鎮(zhèn)海岸） S8（鹿耳環(huán)江） S10（防城港西灣） S9（防城港東灣） S7（犀牛角海岸） S3（樂民鎮(zhèn)海岸） S4（鐵山港） S11（月亮灣） S2（江洪鎮(zhèn)海岸）。 （4）在對沉積物重金屬生態(tài)毒性評價時，運用基于有效態(tài)重金屬篩選建立的綜合生物標(biāo)志物指數(shù)法，較傳統(tǒng)風(fēng)險評價方法更能反映沉積物重金屬的生態(tài)毒性效應(yīng)，且具有靈敏可靠、方便快速和低成本等優(yōu)點及良好的應(yīng)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.
【學(xué)位授予單位】：中國海洋大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：X55;X826

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