【作者】 于瑞莲；

【导师】 赵元慧； 袁星；

【作者基本信息】 东北师范大学 ， 环境科学， 2009， 博士

【摘要】 闽东南沿海是我国人口密集、经济发展迅速的地区之一,近三十年来的经济改革和工业化发展,直接或间接排入近岸海域的污染物越来越多,由此带来的环境问题日渐突出。重金属因具有毒性大、来源广、非降解性和可通过食物链富集的特性,其污染问题倍受关注。近海沉积物是重金属的主要汇集场所,了解沉积物中重金属的含量、时空分布及其赋存形态,对于探寻近海海域重金属的来源、评价污染现状、预测对整个生态系统的影响具有重要的现实意义,是海洋污染防治和环境保护的重要环节,也是正确划分不同海区功能和保证海洋经济可持续发展的关键所在。本文以泉州湾潮间带沉积物为研究对象,分析了10种重金属元素(Fe、V、Cr、Mn、Co、Ni、Cu、Zn、Cd、Pb)的时空分布、来源、赋存形态及其生物可利用性,并采用基于重金属总量和形态分析两个体系的不同评价方法对研究区内重金属污染水平及其潜在生态风险进行了评价。得到的主要结论概括如下:泉州湾潮间带表层沉积物中各重金属元素的平均含量顺序:Fe(38900 mg/kg)﹥Mn(1248 mg/kg)﹥Zn(238 mg/kg)﹥Cr(98.6 mg/kg)﹥Cu(82.5 mg/kg)﹥V(81.9 mg/kg)﹥Pb(74.0 mg/kg)﹥Ni(27.0 mg/kg)﹥Co(12.0 mg/kg)﹥Cd(1.17 mg/kg)。其中Pb、Cr、Cu、Zn、Cd、Mn的区域总平均含量高于国内外大部分海湾、河口的平均值和福建省海岸带土壤环境背景值。由于受人类活动的影响程度不同,所研究的大多数重金属元素在晋江河口和泉州湾南岸表层沉积物中含量相对较高,而在泉州湾外湾表层沉积物中含量相对较低。相关分析、主成分分析和聚类分析结果表明,除Fe、Mn外,泉州湾潮间带表层沉积物中大多数重金属元素主要存在于细颗粒中,且与有机质结合紧密,而不易与S2-形成硫化物,也不易与碳酸盐结合;除Fe、Mn外的大多重金属元素具有人为同源性----工业废水、生活污水、固体废物和大气沉降等,而Fe、Mn主要来源于岩石的自然风化和侵蚀,受人类活动的影响相对较小。从柱状样中重金属分布情况来看,研究区域重金属总体上在1983~1995年之间污染最严重,从20世纪90年代中期以来,污染程度略呈减轻趋势。用改进的BCR逐步提取法(微波消解辅助)分析了泉州湾潮间带表层沉积物中重金属的赋存形态,结果表明,Mn、Cd、Cu、Pb、Co主要以可提取态(前三态之和)为主,而Fe、V、Cr、Zn、Ni主要以残渣态为主,尤其是V、Fe,残渣态占总量80%以上。在可提取态中,Mn、Cd、Zn的弱酸溶态,Cu、Pb、Co的可还原态,Cr、Ni的可氧化态比例相对较高。BCR四步形态之和与微波辅助提取重金属总量之间有着很好的一致性(回收率80%～119%),说明BCR法提取效果好,准确度较高。整个研究区内,表层沉积物中重金属的平均有效态(前三态之和,反映了可迁移性和生物可利用性)含量占总量的百分比顺序如下:Mn (77.69%) >Cu (75.81%) > Pb (71.51%) > Cd (64.11%) > Co (53.97%) > Cr (49.13%)> Ni (48.92%) > Zn (46.55%) > V (18.34%) > Fe (18.07%)。除Cr外,其它重金属的0.5mol/L盐酸可提取量占了BCR可提取量的绝大部分;除V外,其他重金属的0.5mol/L盐酸可提取量与BCR可提取量之间均呈显著正相关,但能否用相对简单的稀盐酸一步提法代替相对复杂的BCR顺序取法来评价沉积物中重金属的生物有效性尚需进一步探讨。基于沉积物中重金属总量,用5种评价方法对泉州湾潮间带表层沉积物中重金属污染进行了评价。以海洋沉积物质量标准(GB18668-2002)进行评价,泉州湾潮间带表层沉积物中各重金属平均含量均为二类沉积物质量,不能满足该区域应执行的一类标准。以地累积指数法进行评价,表层沉积物中V、Co、Ni、Fe为无污染水平,Cr、Mn、Zn、Pb为无-中等污染水平,Cu为中等污染水平,而Cd为强污染水平。以潜在生态风险指数法评价,研究区内各元素的平均潜在生态危害指数(Eir )顺序为:Cd > Cu > Pb > Ni > Co > Cr > Zn > Mn > V;沉积物中重金属综合潜在生态风险指数(RI)表明,研究区域总体上处于生态风险极高水平,Cd、Cu为重要污染因子;各分区重金属综合潜在生态风险顺序为:晋江河口>洛阳江河口>泉州湾南岸>泉州湾外湾。以生物效应浓度法评价,Cr、Ni、Cu、Zn、Cd、Pb的区域总平均含量均在其各自的ER-L与ER-M之间,说明泉州湾潮间带表层沉积物中以上元素对生物的负面效应中等。以综合响应因子法评价,从研究区总平均来看,沉积物重金属污染指示元素及其污染贡献大小顺序为:Cd>Cu >Zn>Mn>Cr,大多站位重金属污染严重。基于形态分析的次生相与原生相分布比值法对重金属污染程度进行评价,研究区沉积物中重金属元素Cu、Mn、Cd、Pb为重要污染因子;总体上洛阳江河口沉积物的污染程度为中度污染水平,而其它三个分区基本为轻度污染水平。以上评价方法各有其优缺点,尚需进一步探讨和完善,在进行沉积物重金属污染评价时应结合多种方法,取长补短,以保证评价结果的合理性和科学性。更多还原

【Abstract】 Southeastern coast of Fujian province is one of thickly populated and fast economic developing district in China. After nearly three decades of economic reform and industrial development, a tremendous amount of waste was discharged to the coast, which resulted in serious environmental problems. Heavy metals are of considerable environmental concern due to their toxicity,wide sources, non-biodegradable properties and accumulative behaviors. Therefore, it is necessary to investigate the content, time-space distribution and speciation of heavy metals in coastal sediments where heavy metals accumulating. The result would make a great contribution to understand the heavy metal resources, pollution status and the effect to the ecosystem, and would have a great significance in protecting the marine environment and ensuring the sustainable development of marine economy.The spatial and temporal distribution, sources, speciation and bio-availability of ten heavy metals (Fe, V, Cr, Mn, Co, Ni, Cu, Zn, Cd and Pb) were analyzed in the intertidal sediments collected from Quanzhou bay, an important estuary in southeast of Fujian province. Several assessment methods, which based on two different assessment systems (total content and sequential extraction), were applied to assess the pollution and potential ecological risk of heavy metals in the surface sediments. The main conclusions were summed up as follows.The average content order of heavy metals in the intertidal surface sediments from Quanzhou Bay was as following: Fe(38900 mg/kg)> Mn(1248 mg/kg)> Zn(238 mg/kg)> Cr(98.6 mg/kg)> Cu(82.5 mg/kg)> V(81.9 mg/kg)> Pb(74.0 mg/kg)> Ni(27.0 mg/kg)> Co(12.0 mg/kg)> Cd(1.17 mg/kg). The average contents of Pb、Cr、Cu、Zn、Cd and Mn in the intertidal surface sediments from Quanzhou Bay were higher than those in most of other domestic and overseas bays and estuaries, and were higher than the background values of Fujian coastal soil. Most of the studied heavy metals presented comparatively higher contents in the surface sediments of Jinjiang estuary and southern coast of Quanzhou Bay, whereas lower in the surface sediments of outside Quanzhou Bay because of the different impact of human activities. The results of multi-statistic analysis (including correlation analysis, principal component analysis and hierarch cluster analysis) showed that most of the studied heavy metals (except Fe and Mn) in the intertidal surface sediments of Quanzhou Bay mainly existed in fine grains, and combined tightly with organic matter other than sulfide and carbonate. Fe and Mn mainly came from the natural efflorescence and erosion of rock, and were influenced comparatively slightly by human activities. But most of other studied heavy metals had the same anthropogenic resources--industrial waste water, life sewage, solid waste, atmospheric settlement, and so on. The distribution of heavy metals in the core sediments showed that the highest polluted period was 1983~1995 on the whole. Since mid-1990s, the pollution degree of heavy metals presented appreciably light trend.The modified BCR-sequential extraction technique, assisted by microwave digestion, was used to determine the speciation (acid-soluble, reducible, oxidizable and residual fraction) of the studied heavy metals in the intertidal surface sediments from Quanzhou Bay. The results showed that Mn, Cd, Cu, Pb and Co mainly appeared in the extractable forms (the sum of the first three fractions), whereas Fe, V, Cr, Zn and Ni mainly appeared in the residual fraction, especially Fe and V presented more than 80% in the residual fraction. In the extractable forms, Mn, Cd and Zn presented comparatively higher percentages in the acid-soluble fraction, Cu, Pb and Co relatively higher in the reducible fraction, Cr and Ni relatively higher in the oxidizable fraction. Comparison of the sum of heavy metal contents in the four steps of BCR-sequential extraction procedure with the total digestion metal contents showed a good agreement for all elements,the recoveries for all metals ranged from 80% to 119%, indicating satisfactory accuracy and validation of the sequential extraction procedure. The mobility and bioavailability, based on the mean values of the relative abundance of the sums of the first three fractions, of the heavy metals in the surface sediments was in the following order: Mn (77.69%) >Cu (75.81%) > Pb (71.51%) > Cd (64.11%) > Co (53.97%) > Cr (49.13%)> Ni (48.92%) > Zn (46.55%) > V (18.34%) > Fe (18.07%). The extractable contents by 0.5 mol/L hydrochloric acid of most heavy metals (except Cr) accounted for the most of the extractable contents by BCR sequential procedure, and the extractable contents of most heavy metals (except V) by the two extracting methods presented significant positive correlation. But whether the comparatively simple one-step extracting method by dilute hydrochloric acid could be used instead of the relatively complex BCR sequential procedure to assess the bioavailability of heavy metals in sediments should be discussed further.Based on the total contents of heavy metals, five assessment methods were applied to assess the pollution degree and potential ecological risk of heavy metals in the intertidal surface sediments from Quanzhou Bay. The comparison of heavy metal contents from this study with that of Marine Sediment Quality (GB18668-2002) showed that the overall average contents of all studied heavy metals in the intertidal surface sediments from Quanzhou Bay met the secondary standard criteria but exceeded the recommended primary standard criteria. The results of geoaccumulation indices showed that Cd presented strong pollution, Cu presented moderate pollution, Cr, Mn, Zn, and Pb presented from low to moderate pollution, V, Co, Ni and Fe presented almost no pollution in most of the sites. According to the indices of potential ecological risk, the consequence of the average potential ecological risk index (Eir) for heavy metal was Cd > Cu > Pb > Ni > Co > Cr > Zn > Mn > V. On the whole, the comprehensive potential ecological risk index (RI) of the sediments presented very high degree. The potential ecological risk indices of the sediments for the different sampling area could be ranked in the following order: Jinjiang Estuary > Luoyang Estuary > Southern Coast of Quanzhou Bay > Outside Quanzhou Bay. According to the bio-effect concentration criteria, the average contents of Cr, Ni, Cu, Zn, Cd and Pb in the surface sediments of study area were all between the effects range low (ER-L) and the effects range media (ER-M), which indicating moderate negative bio-effect. According to the integrated response factors, the pollution indicator elements and their pollution contribution order were as follows Cd > Cu > Zn > Mn > Cr, and most sampling sites were polluted seriously by heavy metals.The result of the ratios of secondary phase and primary phase (RSP), based on the speciation analysis, showed that Cu, Mn, Cd and Pb were important pollution elements, and the pollution degree of heavy metals in the intertidal surface sediments from Luoyang Estuary was moderate whereas those in the other three study sub-areas were slight. Each of the above assessment methods has both strongpoint and shortcoming, and needs to be discussed and improved further. Therefore, several assessment methods should be combined to assess the pollution degree and potential ecological risk of heavy metals in sediments in order to ensure the rationality and scientificity of the assessment result.更多还原