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题名: 海河流域黑臭河流沉积物耗氧过程与机理研究
作者: 荣楠
学位类别: 博士
答辩日期: 2016-05
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 单保庆
关键词: 海河流域,黑臭河流,沉积物耗氧,分布趋势,耗氧机理 ; Hai river basin, Malodorous black river, Sediment oxygen demand, Distribution trend, Oxygen consumption mechanism
其他题名: Research on sediment oxygen consuming processes and mechanisms of malodorous black rivers in the Hai river basin
学位专业: 环境工程
中文摘要:       水体缺氧导致的河流黑臭已成为我国许多河流共同存在的污染问题。沉积物耗氧(SOD)是影响水系统中溶解氧(DO)平衡的重要因素之一,不仅会在一定程度上控制上覆水体中的氧含量,其中包含的一些还原性物质(如Fe2+、S2−)耗氧过程还直接与水体黑臭有关。因此,研究沉积物中的耗氧过程和机理对剖析水体黑臭的成因和缺氧河流治理具有重要的意义。明确沉积物中主要耗氧物质的含量分布和耗氧贡献量,以及外部沉积环境的驱动机制,是研究河流黑臭形成的原因以及沉积物耗氧机理的关键。
      本论文以海河流域平原区为研究对象,首先分析了沉积物的氧化还原状态及各种氧化还原敏感元素在沉积物中的含量和分布,推断造成水体黑臭的内在因素。然后构建了沉积物耗氧速率的分析方法,并应用于海河流域平原区河流,明确了SOD在季节和空间分布上的变化特征,判断了其耗氧污染程度。随后对沉积物耗氧过程进行了分级,分析了各个耗氧过程对SOD的贡献比例,结合沉积物表层和不同深度中各种耗氧物质的含量分布特征,在理论推导的基础上,提出了沉积物耗氧的主要机理和模式。最后探讨了沉积物耗氧可能带来的水环境效应,以及沉积物理化指标对微生物群落结构的影响。
      主要研究内容和结果如下:
      (1)分析海河流域平原河流表层沉积物中ORP、Fe2+、酸挥发性硫(AVS)的含量,推断水体黑臭的主要原因。沉积物氧化还原电位(ORP)在-454.2~93 mV之间,接近90%的沉积物处于弱还原态和还原态,有机质(OM)、Fe2+、AVS的含量高,含量分别在1.4%~16.9%、0.37~63.73 g/kg(干重)、0.66~58.73g/kg(干重)之间,严重污染的子牙河区域其含量甚至比文献报道的值高出一个数量级。沉积物ORP与AVS、Fe2+、OM之间存在显著的负相关关系,强还原环境促进了铁和硫的富集,形成FeS等黑色物质,释放到上覆水中消耗氧气并造成水体发黑发臭。
       (2)构建沉积物耗氧速率分析方法,确定海河流域平原区沉积物耗氧季节和空间变化特征,评价其耗氧污染水平。通过微电极系统和柱培养系统同时对沉积物耗氧速率进行了测定,两种方法的SOD测定结果相近,微电极法测得的氧扩散通量略小于柱培养法测得的氧总通量。根据2组实验结果之间具有很好的相关性(R2=0.842),可以认为这2种测定方法均具有一定的可靠性。应用可操作性更好的柱培养法测定了海河流域平原区沉积物耗氧速率,其分布具有明显的夏季高于秋季的变化特征,夏季SOD最高达3.098 g/m2/d,秋季SOD均小于1.0 g/m2/d;在空间分布上,子牙河水系和徒骇马颊河水系SOD较其他水系高。通过对比研究和文献调研,确定了海河流域SOD的评价标准:SOD<0.5 g/m2/d时,沉积物耗氧水平较低;0.5 g/m2/d 1.0 g/m2/d时,沉积物耗氧水平很高。夏季整个流域平原段有75.3%的样点SOD>0.5 g/m2/d,判断沉积物耗氧污染严重。SOD与沉积物中还原性物质AVS、Fe2+存在显著的正相关关系,AVS和Fe2+可能是产生沉积物耗氧的主要因子。
      (3)对SOD进行分级,明确各个耗氧过程的相对贡献,揭示沉积物耗氧机理。采用添加不同的抑制剂方法,将沉积物耗氧过程分为生物耗氧过程和化学耗氧过程,进一步将化学耗氧过程划分为Fe2+耗氧、S2−耗氧、Mn2+耗氧。结果显示,在沉积物中化学耗氧>生物耗氧> Fe2+耗氧> S2−耗氧> Mn2+耗氧,其中化学耗氧平均占总SOD的58.87%,是SOD的主要贡献者;Fe2+耗氧占化学耗氧的33.26~96.79%,是化学耗氧的主要贡献者;S2-耗氧占总SOD的1.78~45.71%; Mn2+的耗氧很低。沉积物SOD与Fe2+、AVS含量具有显著的相关关系,生物耗氧与NH4+浓度之间有显著的相关关系,加之沉积物的还原性和富铁富硫特征,认为主要耗氧机理是生物耗氧中的NH4+硝化耗氧和化学耗氧中的Fe2+、S2-耗氧占主导,这与流域高NH4+高Fe2+、S2-的污染特征一致。
      (4)探索了沉积物耗氧伴随的环境学效应以及沉积物耗氧和其他理化特征对微生物群落结构的影响。沉积物耗氧培养实验过程中,有氧条件下沉积物NH4+和溶解性活性磷(SRP)的释放通量要小于缺氧条件下,其中NH4+的释放量足以使水体变为劣V类水质。估算子牙河水系水体的总耗氧速率(WOD)在0.034~5.587 g/m2/d之间,沉积物的耗氧速率约为水体耗氧速率的41.9%,对水体溶氧的消耗能力也很显著。SOD产生的沉积物表面低溶氧直接作用于底栖生物,导致其生物量和密度降低。采用分子生物学的方法分析了环境因子对微生物分布的影响,主要环境因子为SOD、OM、Fe(Ⅱ),它们与古菌和细菌的分布均有显著的正相关关系。
英文摘要:        Many streams in China are confronting with common malodorous and blackwater pollutions resulting from hypoxia. Sediment oxygen demand (SOD) is one of the important factors affecting oxygen balance in water systems. SOD can control the oxygen content in overlying water to some extent. Oxygen consumptions of some reduced substances (e.g., Fe2+ and S2−) involved in SOD also have relation with malodorous black problem. Therefore, study on sediment oxygen consumption processes and mechanisms has great significance for analysing the causes of malodorous black water and treatment on hypoxia river. The key is understanding concentrations and distributions of the main oxygen consumption substances and their oxygen consumption contributions, and indicating the driving mechanism of external sediment environment.
       The study area were plain rivers in the Hai river basin.
       The thesis first analyzed concentrations and distributions of sediment redox state and the relative sensitive elements, then deduced the causes of malodorous black water. The method of measuring sediment oxygen demand was proposed. Based on this method, the seasonal and spacial distribution of SOD in the study area were clear, then the sediment oxygen consumption levels were estimated. Fractionating SOD was carried out to determine the proportion of each oxygen consumption process to the total SOD. On the basis of the theoretical derivation, the fractionation result and concentrations and distributions of oxygen consumption substances in surface and deep sediments, the main mechanism and pattern of sediment oxygen consumption were proposed. Finally the environmental effects exerted by sediment oxygen demand and the impacts of physicochemical indexes of sediment on microbial community structure were discussed. The main contents and results are as follows:
      (1) Concentrations of oxidation-reduction potential (ORP), Fe2+ and acid volatile sulfide (AVS) in the plain river surface sediments of the Hai river basin were analyzed, and the causes of malodorous black water were infered. The sediment ORP was in the range of -454.2~93 mV, showing that nearly 90% of the sediments were at reduced state. High contents of organic matter (OM), Fe2+ and AVS were in the range of 1.4%~16.9%, 0.37~63.73 g/kg(dry weight) and 0.66~58.73 g/kg(dry weight), respectively. These substances in seriously polluted Ziya river system were an order of magnitude higher than other reported values. ORP had significant negative impacts on the concentrations of AVS, Fe2+ and OM. The strong reducing sediment environment promoted the enrichment of Fe and S and the formation of black FeS. FeS released into the overlying water would consume oxygen and cause malodorous and blackwater.
       (2) Method to analyze sediment oxygen consumption rate was formed, seasonal and spacial distributions of SOD in the study area were realized, and SOD levels were evaluated. Microelectrode measurements and sediment core incubations were performed to determine SOD. The two sets of results were similar, and the diffusive oxygen flux determined by the microelectrode method was smaller than the total oxygen flux determined by the core incubation method. Total oxygen flux obviously correlated with diffusive oxygen flux (R2=0.842). The two method, therefore, were believed to be reliable methods. By using the more effective core incubation method, SOD in the plain rivers of the Hai river basin were determined and showed apparent seasonal distribution of higher SOD in summer than in autumn. SOD could reach 3.098 g/m2/d in summer, whereas lower than 1.0 g/m2/d. In the spatial distribution, the Ziya river and Tuhaimajia river had higher SOD values than other rivers. By means of comparison and literature research, the SOD evaluation criterion was determined: SOD<0.5 g/m2/d, low levels; 0.5 g/m2/d 1.0 g/m2/d, very high levels. In summer, there were 75.3% of sampling sites had SOD higher than 0.5 g/m2/d, judging that sediment oxygen consumption in the plain rivers of the Hai river basin being serious. There were significant positive correlations between SOD and AVS, Fe2+. AVS and Fe2+ may be the major factors producing sediment oxygen consumption.
      (3) Fractionations of SOD and their relative contributions to SOD were conducted to reveal the sediment oxygen consumption mechanism. SOD was fractionated into biological SOD and chemical SOD and for further fractionating the chemical SOD into ferrous, manganese, and sulfide components. The results showed that SOD decreased in the order chemical SOD>biological SOD> ferrous SOD > sulfide SOD > manganous SOD. The chemical SOD contributed 58.87% of the total SOD, on average, representing the dominant component of the total SOD. The ferrous SOD contributed 33.26~96.79% of the chemical SOD, and it was the dominant contributor to the chemical SOD. The sulfide SOD contributed 1.78~45.71% of the total SOD, and the manganous SOD was very low. SOD had significant positive correlations with AVS and Fe2+,and biological SOD had significant positive correlations with NH4+. In addition, sediments were reductive and rich in iron and sulfur. It could be believed that the main sediment oxygen consumption mechanisms were NH4+-controlled biological SOD as well as Fe2+ and S2- -controlled chemical SOD. These mechanisms were consistent with the high NH4+, Fe2+ and S2- pollution characteristics of the basin.
      (4) The environmental effects exerted by sediment oxygen demand and the impacts of physicochemical indexes of sediment on microbial community structure were discussed. During the SOD incubation,the fluxes of NH4+ and soluble reactive phosphorus (SRP) from sediment to water at oxic conditions were both lower than that at anoxic conditions. The flux of NH4+ could cause the water quality exceed V class. Estimating the total water oxygen demand (WOD) was in the range of 0.034~5.587 g/m2/d. SOD accounted for 41.9% of the WOD, and its oxygen consumption ability was also very significant. Low DO at the sediment surface exerted by SOD would have direct effects on benthos, leading to decreased biomass and density. Using molecular biology methods to analyze the influences of environmental factors on the microbial distribution. The main environmental factors were SOD, OM, and Fe(Ⅱ), all having significant positive correlations with the distribution of archaea and bacteria.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/36950
Appears in Collections:环境水质学国家重点实验室_学位论文

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Recommended Citation:
荣楠. 海河流域黑臭河流沉积物耗氧过程与机理研究[D]. 北京. 中国科学院研究生院. 2016.
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