【作者】 刘勇；

【导师】 弓晓峰； 吴丰昌；

【作者基本信息】 南昌大学 ， 环境科学， 2012， 硕士

【摘要】 目前,我国湖泊富营养化及流域水污染问题十分突出,严重影响着湖区人民的生产生活及饮用水安全,极大地制约了区域社会经济的可持续发展。湖泊富营养化问题已经成为湖泊环境变化研究的热点和前沿问题。湖泊中的沉积物以其信息量丰富、连续性好、时间分辨率高和地域覆盖面广等特点,记录了湖泊流域人类活动的信息以及湖泊水质和生态系统的演变过程。因此,利用湖泊沉积记录重建湖泊不同历史时期的环境变迁过程,对研究湖泊生态环境演变以及富营养化发展过程具有重要的科学意义。本文以滇池为研究对象,采集了滇池表层沉积物和柱状沉积物样品,对滇池长期演变过程中沉积物中营养盐、化学元素的地球化学特征以及重金属污染进行了分析研究。论文探讨了滇池表层沉积物中不同结合态磷含量空间分布特征,滇池近代富营养化加剧过程中柱状沉积物中有机质(碳、氮)、磷形态与生物硅的沉积记录,同时分析了滇池沉积物中化学元素的地球化学特征以及对沉积物中几种典型重金属污染进行了评估。结合近年来滇池富营养化和生态系统结构发生变化过程,主要得到以下结论：(1)滇池表层沉积物中主要以钙结合态磷(Ca-P)、铁结合态磷(Fe-P)、酸可提取有机磷(ASOP)以及碱可提取有机磷(NaOH-P)、核酸及焦磷酸盐磷(POLY-P)、残渣态磷(Res-P)、葡萄糖结合态磷(Sugar-P)、水溶性磷(H20-P)。为主。各磷形态含量大小关系表现为：钙结合态磷(Ca-P)>酸可提取有机磷(ASOP)>碱可提取有机磷(NaOH-P)>铁结合态磷(Fe-P)>核酸及焦磷酸盐磷(POLY-P)>残渣态磷(Res-P)>葡萄糖结合态磷(Sugar-P)>水溶性磷(H20-P)。(2)滇池表层沉积物中各磷形态含量分布具有差异性,各磷形态含量分布是人为因素和自然因素共同作用的结果。不仅受到来自人类活动污染排放的影响(如铁结合态磷(Fe-P)及酸可提取有机磷(ASOP)等),而且也与滇池流域地貌背景(喀斯特地貌,磷酸盐岩分布较多)有关(如钙结合态磷(Ca-P)),同时可能也受到湖泊水动力等自然过程的影响(如碱可提取有机磷(NaOH-P))。(3)滇池表层沉积物中,生物有效性磷形态组分(主要包含铁结合态磷(Fe-P)、酸可取有机磷(ASOP).水溶性磷(H2O-P)、核酸及焦磷酸盐磷(POLY-P)以及葡萄糖结合态磷(Sugar-P))含量较高(介于753.2～1036.4mg/kg),表明滇池沉积物中内源磷释放潜力较大。生物有效性磷形态组分(BAP)含量与各磷形态之总和(Total-P)正相关((r=0.896,p<0.05,n=18)),即各磷形态总和含量高,则对应的生物有效性磷形态组分含量也高。同时,生物有效性的磷形态组分相对比例在滇池北部湖滨区域较高,南部区域较低,这可能与近年来滇池北部人类污染排放更多有关,而且这也与近年来滇池北部富营养化更严重,蓝藻水华频繁暴发具有一致性。(4)滇池沉积物中总有机碳(TOC)、总氮(TN)、总磷(TP)、铁/铝磷(Fe/Al-P)、钙磷(Ca-P)以及有机磷(OP)的沉积记录显示,约自20世纪50年代后滇池各营养盐在沉积物中迅速累积,而在1950s之前,沉积物中营养盐累积较少且变化稳定,这表明自20世纪50年代以后滇池开始由中营养化向富营养化过渡。(5)滇池沉积物中有机质含量逐年在增加,特别是1950s后,滇池富营养化加剧,沉积物中有机质含量逐年增加更明显,且沉积物中有机质(碳氮比介于7～13.5内)主要来源于滇池内源藻类和细菌等各种生物残体的贡献,陆源有机质贡献较小。沉积物中总氮(TN)、总磷(TP)以及有机磷(OP)含量均与总有机碳(TOC)含量显著正相关。生物有效性的铁/铝磷(Fe/Al-P)在1950S后也急剧增加,表明滇池外源磷的输入与生物量的增长以及蓝藻水华的暴发一致性,外源磷污染控制的必要性。(6)滇池不同区域生物硅(BSi)沉积记录及其与总磷(TP)以及总有机碳(TOC)含量关系表明滇池在长期演变中,生态系统结构发生了变化。滇池北部近年来富营养化加剧,蓝藻大量繁殖成为优势种群而导致生物群落结构单一化；而中部等地区硅藻仍保持大量增长趋势,进而表明藻类在该区域也正处于大量增长的过程,这预示了该区域富营养化正处于某一发展阶段,同时也暗示了滇池生态系统结构存在不断恶化趋势。(7)滇池沉积物中微量元素(Ba、Si、Cu、Pb、Zn、V、Cd)主要与近60年来人类活动更频繁,污染物排放量大而对滇池物源和化学元素贡献密切相关。同时,浅层沉积物中微量元素的富集也受到水动力等自然作用影响明显。常量元素(Al、Fe、K、Ca、Mn、Ti)含量具有空间差异性主要与滇池地理环境空间差异性有关。滇池北部多碳酸盐岩、玄武岩和磷块盐,南部多碎屑岩、磷酸盐岩以及磷块盐而造成元素空间分布不均。(8)滇池沉积物中典型重金属(Cd、Cu、Zn、Pb)污染分析表明：Cu、Zn、Pb尚处于中度污染程度,潜在生态风险程度属于低微水平,然而近60年来各重金属污染均有所加重,潜在对环境的危害也更大,其中沉积物中Cd污染十分严重,潜在生态风险程度很高,对生态环境危害巨大。同时滇池北部污染较南部严重,这表明人为环境干扰可能是重金属污染的主要因素。更多还原

【Abstract】 At present, the problem of lacustrine eutrophication and watershed pollution is noticeable, which seriously affects the production, living and the drinking water security. It extremely restricted the sustainable development of area social economy. Eutrophication has already been the focus and the advancing edge of the lacustrine environment research.The lacustrine deposit is capable of recording the information of human activities and the process of environmental change in lake basins with the characteritics of large information capacity, outstading continuity, good temporal resolution and wide geographical coverage. Therefor, it’s scientific significant for studing ecological environment evolution and lake eutrophication to using the lacustrine deposit to note and rebulid historical period of lakes.Dianchi Lake was chosen as survey region in this paper,and collected the Dianchi Lake surface sediment and columnar sediment samples. The geochemical characteristics of nutrients and the heavy metal pollution in the lacustrine deposit in long-term evolution process of Dianchi Lake was analysed and researched in this paper. The distribution characteristics of the content of different dissolved combined amino phosphorus in the surface layer of the lacustrine deposit, the organic matter (C, N) in generated in modern aggravating process of eutrophication and the sedimentary records of phosphorus’ fractions and biogenic silica were mainly analysed and discussed. At the same time, the geochemical characteristics of nutrients was analysed.and several typical heavy metal pollution, combining with the situation of eutrophication and changed regional ecological system structure in Dianchi Lake, was emphatically assessed in this study. The main conclusions as follows:(1)The main forms of phosphorus in the Dianchi Lake surface sediments were Ca-P,Fe-P,ASOP,NaOH-P,POLY-P.Res-P.Sugar-P and H2O-P.The order of the content was:Ca-P> ASOP> NaOH-P> Fe-P> POLY-P> Res-P> Sugar-P> H2O-P.(2)There were difference of the distribution between different forms of phosphorus, which indicated that the distribution was caused by human and natural factors. Not only was it influenced by pollution emission, such as Fe-P and ASOP et al., but related to the geomorphic background of Dianchi Lake basin (Ca-P), such as the wide-spreaded karst landform and phosphate rock, and it also had relationship with the natural process of hydrodynamic force like NaOH-P.(3)The large potential of the release of internal phosphorus in the Dianchi Lake surface sediments could be improved by the high content, ranging from753.2to1036.4mg/kg, of the bioavailable phosphorus formation (mainly included Fe-P, ASOP, POLY-P, Sugar-P and H2O-P). BAP concentration had highly significant correlation with Total-P concentration (r=0.896, p<0.05, n=18). It meant that BAP concentration proformed increasing trend with the increase of Total-P concentration. The relative proportion of BAP in northern lakeside area was higher than southern area. The reason may be the more pollution emission and more serious eutrophication that coordinated with the frequently occuing of cyanobacterial bloom in northern area in Dianchi Lake.(4)The sedimentary records of TOC, TN, TP, Fe/Al-P, Ca-P, OP showed the nutrient accumulated rapidly after1950s in the Dianchi Lake sediments. However, the nutrient was more steady before1950s, which illustrated that Dianchi Lake turned to eutrophication from a mesotrophic lake after1950s.(5)The content of organic matter was increasing year by year in Dianchi Lake. After1950s, the increase trend was more obvious and the eutrophication of Dianchi Lake was more serious. The organic matter in the sediments (the atomic ratios of TOC/TN ranged from7to13.5) mainly derived from many kinds of residual of authigenic alga and bacteria, peripherally from terrene. TN, TP and OP concentration in the sediments respectively had significant positive correlation with TOC concentration. And the sharp increase of bioavailable Fe/Al-P after1950s.suggesting that consistency of exogenous phosphorus input, the growth of the biomass and algae outbreaks. The high significant correlation indicates that it’s necessary to control the exogenous phosphorus pollution.(6)Vertical variation of BSi concentrations and its relationship with BSi, TOC and TP concentrations showed that the ecological system structure have changed with the long-term evolution of Dianchi Lake. Diatoms were still increasing in the central part of Dianchi Lake, which showed that the alga was increasing greatly in this area in recently years. While the dominant "blue alga" instead of the other alga, including diatoms, the ecosystem were destroyed in the northern Dianchi Lake because of eutrophication in recent years, and that meant the area eutrophication is in a stage of development and also indicated that the Dianchi Lake ecosystem structure had been the deteriorating trend.(7)The rising of concentration of microelement including Ba, Sr, Cu, Pb, Zn, V and Cd in the Dianchi Lake sediments was closely related to the more frequent human activity and more quantity of pollutant discharged. Besides, the enrichment of microelement in shallow sediments was also influence by some natural operation like hydrodynamic force. There were carbonatite, basalt, phosphorite in the northern and clastic rocks, phosphate rock and phosphorite in the southern, so the otherness of macroelement(Al,Fe,K,Ca,Mn and Ti) was caused by spatial diversity of geographical environment.(8)The analysis of the typical heavy metal (Cd, Cu, Zn, Pb) in the Dianchi Lake sediments showed the pollution of Cu, Zn. Pb was in moderate level and the potential ecological risk was insignificance. But the pollution and potential hazard was more and more notable. However the pollution of Cd in Dianchi Lake was very serious and it brought high potential ecological risk and was harmful for ecological environment. In addition, the pollution of heavy metal of northern was worse than southern area, which indicated that the main resource of heavy metal pollution was human activity.更多还原