【作者】 李志建；

【导师】 岳钦艳；

【作者基本信息】 山东大学 ， 环境工程， 2011， 博士

【摘要】 湖泊沉积物记录着水体污染历史、人类影响和环境变迁,沉积物与水体有着紧密的、强烈的相互作用,对沉积物污染物的状态和动态的研究,可以评价内源污染对水体的影响及预测有内源释放导致的水质变化和富营养化有着重要的理论和实际意义。本研究在结合大量国内外相关文献的基础上,通过野外监测与室内实验分析,运用动态模拟和多元统计分析等方法,对南四湖上下级湖区沉积物的营养物及重金属污染特征、潜在的生态风险、污染物的环境化学行为,释放规律和特征,沉积物-水界面的相互作用,以及与沉积物对应的水质的响应关系进行了系统的研究。主要研究包括主要从污染物形态上进行了释放风险评价;通过室内沉积物-水界面模拟,分析其中不同环境条件及水质条件的释放规律,对释放的动力学进行了拟合以进一步寻求其释放的特征和机制。最后,通过分析沉积物与水体污染物及理化特征间的相关性,进一步探究其相互作用和影响过程。本研究得出以下结论：1.用沉积物营养物剖面分析了南四湖沉积物中营养元素的积累规律,结果表明南四湖受近代人为影响较大,沉积物氮、磷、有机质有进一步的积累,含量范围分别达925.66～4695.82mg/kg,176.37～1281.37 mg/kg和1.21%～16.65%。表层沉积物总磷富集以入湖河流最为严重,入湖河流高于湖区,湖区沉积物中富集顺序为：南阳湖>独山湖>微山湖>昭阳湖。2.运用顺序提取法测定沉积物磷的形态,分析了其移动性、生物有效性和潜在释放风险。结果表明,南四湖上下级湖以无机磷占优势,有机磷含量占总磷的3.98%-27.59%,无机磷中又以交换态磷、铁磷等活性磷含量高,占比例大,磷极易向水体释放,生物有效性高,潜在释放风险大。3.磷形态相关性分析结果表明：除残渣态磷外,其余各形态磷含量与总磷含量均显著相关,尤其是Fe-P和Ex-P与总磷呈极显著相关；沉积物中的生物可利用磷的含量变化趋势与人为活动造成的沉积物中TP含量的增加趋势相一致。铁磷与交换态磷、闭蓄态磷、自生磷和有机磷均具有极高的相关性。交换态磷与铁磷、有机磷均有较高的相关性,有机磷的降解释放,铁结合态磷的还原释放等作用,都可导致弱吸附态磷含量的增高。除了残渣态磷外,其他磷形态与沉积物有机质均有着良好的相关性,尤其以有机磷与有机质的相关性极显著。4.南四湖下级湖12个监测点沉积物与水质TP浓度对比分析表明,夏季有利于磷P向上覆水体释放。相关分析表明,沉积物总磷与水体总磷和溶解性磷含量不相关,水体磷污染的响应与沉积物磷污染积累并不一致。下级湖区沉积物磷负荷较高,但上覆水中磷负荷较低,表明沉积物-水中污染物交换更强烈。说明水质响应的并不取决于沉积物污染物的含量,而更多地决定于污染物在固-液两相的交换和相互作用,及沉积物所处的状态及变化。5.为了进一步阐明污染物在沉积物-水体两相的交换和相互作用,进行了沉积物-水界面动态模拟实验,能够在一定程度上反应了沉积物在环境条件改变时水中污染物的响应情况；还可定量确定其交换速率,通量,以此判断不同条件下,一段时间内的释放量。沉积物在好氧和缺氧条件下均可能发生磷的释放,缺氧条件下总磷和溶解反应性磷(SRP)的释放速率和释放量均大于好氧条件下。但在好氧阶段更倾向于吸附磷,而在水体磷浓度较低时也可能转向磷的释放；在缺氧条件下,沉积物趋向于向上覆水释放磷,6.吸附和释放动力学和等温线能够很好地解释磷吸附和释放能力,进一步预测沉积物污染动态和趋势。Pseudo一级和二级动力学均能较好地描述磷吸附／解吸过程,但pseudo二级速率方程预测的平衡吸附量更接近实际所测得的结果。因此,更适合解释沉积物磷吸附和释放过程,说明磷的吸附／释放是受化学速率控制的,吸附速率取决于吸附量而非吸附质浓度。改进的Langmuir模型比Freundlich模型和线性模型能更好地拟合磷释放过程。拟合结果表明沉积物磷的吸附过程是在低浓度范围内的单分子层吸附,并可通过得出的最大吸附量评价沉积物的吸附／解吸能力.7.通过序批等温实验,拟合后计算得到沉积物与水平衡时的零平衡磷浓度(EPC0),该方法能够有效地预测沉积物磷所处的释放状态,在白马河、新薛河、小泥河、十字河入湖口及大捐,沉积物向水体释放磷的风险较大,需密切关注；而在大捐洼、艾湖近岸及微山岛北,沉积物和水体磷处于近似的平衡,也有释放的可能,需加强野外监测。8.用重金属总量富集因子法分析沉积物重金属的累积程度,结果表明：南四湖沉积物中重金属以Cd富集最严重,与本底值相比超过几十倍,其次Zn, Cu, Pb为中等污染,超标本底值2-6倍,Cr, Mn超标较少,Fe与本底值基本持平。重金属污染较重的为上级湖的独山湖,下级湖的艾湖境内,入湖河流为上级湖区的洗府河和下级湖区的十字河。上级湖区重金属污染较下级湖区严重。9.运用沉积物重金属总量和影响筛分标准对比法,详细地评价重金属污染和毒性风险及对生物环境的影响。结果表明,南四湖大部分沉积物在一定程度上遭受到了重金属的污染。其中,受Cr和Zn的影响最严重,受Cd, Pb, Cu, Mn的影响中等,Fe的影响最轻。上级湖较下级湖更多地受至Cu, Cr, Pb和Cd的污染；Zn、Fe和(?)Mn的污染在上、下级湖无明显差异。10.运用重金属风险评价码(RAC)及各形态所占比例分析重金属的潜在释放风险。其中,Cd较大部分(30%-65%)是可移动态,因此具有高的进入食物链的风险,约46%-50%的Pb以交换态或碳酸盐结合态存在,对水环境具有较高风险,Cr和Zn移动性也相对较高。大部分Cu和Mn以非移动态存在,近少部分发现于碳酸盐结合态,因此对水生环境具有中等风险。铁绝大多数以非移动态存在,且富集因子很低,对环境风险很低。7种金属的潜在风险顺序为Cd>Pb>Cr>Zn>Cu>Mn>Fe。11.应用聚类分析为污染区域进行分类,发现上、下级湖重金属综合污染有着显著的差异；用主成分综合分析确定重金属综合污染的重点区域,结果表明U9,U1,U10,U8,D6和D1是重金属综合污染最严重的点位,上级湖较下级湖污染严重,这与当地密集的工业排放和人为活动有关,与聚类分析和富集因子法的评价结果一致。对重金属释放动力学的拟合研究表明,Pseudo二级动力学模型较Pseudo-一级动力学模型和Elovich模型更好的拟合沉积物重金属动力学。5种重金属的解吸能力顺序为Cr>Cu>Pb>Zn>Cd。更多还原

【Abstract】 Lake sediment recorded pollution history, human impact and environmental changes. Sediment interacts tightly and strongly with the water column. It is vital and significant to study on the pollution status and dynamic of sediment and further to assess the effect of internal pollution on water quality and predict water quality change and eutrophication. Based on large literature, the pollution characteristics of nutrients and heavy metals in sediments in the upperstream and downstream Nansi Lake, potential release risk, environmental behaviour, release rule and pattern, interaction between sediment-water interface and corresponding water quality response related the sediments were studied comprehensively and systimatically by the means of field monitoring, laboratory experiment analysis and dynamic modeling and multivariate statistical analysis. The main results and concusion were listed as follow:1. Nutrient accumulation degree were discussed by the vertical profile of sediment nutrients, and the results showed that Nansi Lake suffered quite human impact in recent years, nitrogen (N), phosphorus (P) and organic matters (OM) accumulated constantly, and the contents range were 925.66～4695.82mg/kg,176.37～1281.37 mg/kg and 1.21%～16.65%, respectively. Surface sediment total phosphorus (TP) accumulation in inflows was heavier than that in lake area. In the lake sediment, TP load followed the order: Nanyang Lake>Dushan Lake>Weishan Lake>Zhaoyang Lake.2. P speciation was determined by the sequential extaction method to evalue the mobility, bioavailability and potential release risk. The results indicated that inorganic phosphorus was predominant both in the upperstream and the downstream lake, while, organic phosphorus just accounted for 3.98%～27.59% of total phosphorus. Among inorganic phosphorus, reactive P, like Ex-P and Fe-P, was predominant speciation, with a lare percentage, and was high bioavailable, so it is extremely susceptible to release into water column and brought large risk to environment.3. The correlation between phosphorus speciations suggested that, except for De-P, other phosphorus forms showed a significant correlation with total phosphorus, especially for Fe-P and Ex-P, displaying an extremely significant correlation. The change of bioavailable P accorded with the increase of TP in the sediment due to human activities. Fe-P manifested a quite high correlation with Ex-P, Oc-P, ACa-P and Or-P. except De-P, other P forms showed a good correlation with sediment OM, especially, Or-P, is highly related to OM.4. Comparation the TP contents of sediment and water of winter and thoseof summer at 12 monitoring sites in the downstream Mansi Lak, the results showed that water TP tended to increase in summer, however, most sediment TP decreased in summer, indicating part of P was susceptible to release in summer. Inaddition, the downstream lake had a relatively low sediment TP load, but a high water TP load, suggestin a moer stronger exchange among pollutants in sediment and water.The analysis revealed that there was no correlation between sediment TP and water TP. Water quality response to the sediment P pollution is not reflected by the sediment P content, but, in most extent, dependent on the exchange and interaction between the solid and the liquid phase, ie., sediment and water, as well as the status of sediment and water.5. In order to clarifying the exchange and interaction of pollutant between sediment and water, sediment-water interface dynamic modeling experiment was performed, which, to some degree, reflected the water response to sediment pollution when environmental condition varied, and can further to determine the exchange rate and flux in certain time. The results indicated that P release can occure in both anerobic and oxic condition, the release rate and flux of TP and SRP in anerobic condition were higher than those in oxic condition. Sediment tended to adsorb P in oxic condition, while, when the overlying water P is quite low, sediment can relese P into overlying water. Sediment was more susceptible to release P in anerrobic status.6. The kinetics and isotherm of adsorption/desorption can well decriblethe capacity of adsorption/desorption, and further to predict the exchange dymamic and rule. The results showed that Pseudo-first and Pseudo-second order rate equation can well describe the adsorption and release course, however, the pseudo-second-order rate model was more proper to elucidate sediment P sorption and release because adsorption/adsorption capacity predicted by the pseudo-second-order rate was more close to the measured results Pseudo. It suggested that the adsorption and release of P were chemically rate controlled, and the rate depended on the sorption capacity rather than the concentration of the sorbate. The results indicated that the P sorption isotherms on three sediment samples were better described by the modified Langmuir model than by Freundlich or the linear model because of its higher R2 value, which suggested that the adsorption process was single molecular layer adsorption within a low concentration range, and the maximum adsorption contents could be determined to assess the capacity of adsorption and release.7. The EPCo method can effectively predict sediment status. At the sample site S1, S3, S4, S5, and S7, i.e. at the sites Baima, Xinxue, Xiaoni, Shizi River and Dajuan, EPC0> SRP, the sediments had potential to release P to the water column. These sites need continual concern; while at S2, S6, S8, and S11, i.e. at the sites Dajuanwa, Aihu and North of Weishan Island, EPC0 SRP, the bed sediment and water were approximately in equilibrium with respect to SRP, and it was likely to release P into water, therefore, these site need to be monitored further.8. EFs for all metals from each sampled site can determinate the enrichment degree and the anthropogenic metals. According to the EFs, Cd suffered the most heavy accumulation, up to dozens of times of background value;then, Zn, Cu and Pb showed a medium pollution, about 2-6 times background values; followed by Cr and Mn, were slightly higher than background values. Last, Fe was just close to its background value.the upperstream lake suffered more heavily pollution of metas than the downstream did. In the upper reaches, the most serious pollution in lake area was founded in Dushan Lake, while, in the lower reaches, found in Aihu Lake. As for inflows, Guangfu River and Shizi Rigver were the mos large pollution spots.9. Compared the mean of total metal the Nansi Lake sediments with LEL and the SEL, the result indicates that Nansi Lake sediments can be severely impacted by Cr and Zn, meanwhile, the impact from Cd, Cu, Pb and Mn may be considered moderate, while, there is just very low impact from Fe. Based on the above analysis from metal distribution, in the whole, the upstream lake suffered more severe pollution from heavy metal. This is in accordance with the more industries, more developed cities and such high-dense population in the upstream.10. Comparing the percentages of 7 heavy metals contributed to different risk levels from 26 sites in Nansi Lake with the Risk Assessment Code (RAC) was used to assess the potential risk of sediment metals. According to the RAC, there was considerable enrichment of metals at inflows and lake area. Amongst the different metals, Cd concentration was the lowest but a major portion (30%-65%) was contained in mobile fraction (either exchangeable or carbonate bound), therefore, it was of great risk to enter the food chain. About 46%-50% of Pb in sediment existed in exchangeable or carbonate fraction and thus exert a potential risk for the aquatic environment. Followed this, Cr and Zn were relatively easy to mobile. Most Cu and Mg were in immobile fraction in Nansi Lake, just little part was found in carbonate fraction thus posing medium risk for the aquatic environment. Fe concentration was the highest but with lowest enrichment, thus showed only low risk for the aquatic environment. The potential risk of these 7 metals followed the order:Cd>Pb>Cr>Zn>Cu>Mn>Fe.11. The kinetics of heavy metal adsorption/release can explain the capacity of adsorption and release. The study results indicated that Pseudo-second-order model can more better fit the kinetics of heavy metal adsorption/release than Pseudo-first-order model and Elovich model。The capacity of desorption of five heavy metals followed in the order:Cr>Cu>Pb>Zn>Cd.更多还原