【作者】 张俊杰；

【导师】 郑西来；

【作者基本信息】 中国海洋大学 ， 环境工程， 2014， 博士

【副题名】以青岛李村河为例

【摘要】 河口是联系陆地河流与海洋两大生态系统的过渡地带，河口区营养元素的生物地球化学行为对其向海洋的输出有显著的影响。磷是水体中浮游植物生长的限制性营养元素之一，內源磷的释放是导致水体富营养化的重要因素。由于水深较浅，河口区的沉积物往往在风浪和潮汐等外力引起的底部剪切力作用下经历着周期性的再悬浮。沉积物再悬浮过程往往伴随着内源磷向上覆水体的放释，是內源磷迁移-转化的重要途径。作为一条典型的城市纳污河流，李村河口沉积物污染比较严重。再悬浮条件下，沉积物中赋存的磷的迁移和转化对河口区乃至胶州湾的生物生产过程有重要的影响。本文通过现场观测、采样和分析，掌握了李村河口沉积物及其上覆水体中磷及其它主要生源要素的时空分布规律；通过模拟沉积物的再悬浮过程，研究了沉积物对侵蚀切应力的响应特征，探讨了再悬浮对上覆水体磷负荷和沉积物磷形态的影响机制；通过培养试验，研究了再悬浮条件下沉积物中有机磷的矿化机制，并在此基础上考察了沉积物性质和环境因素对矿化速率的影响；通过研究悬浮沉积物的光化学降解过程，探讨了再悬浮条件下內源有机磷的光降解特性，并进一步分析了不同因素对降解过程的影响。通过研究取得了以下新的认识和结论：1.监测研究区水-沉积物的理化性质和动态变化特征。（1）在不同季节中，上覆水体溶解性总磷（DTP）、溶解性无机磷（DIP）、NH+4-N和NO-2-N的含量均呈现出涨潮时降低，落潮时升高的趋势；而盐度、pH、溶解氧和氧化还原电位等指标的变化规律则与之相反，即涨潮高，落潮低。上覆水的物理化学性质受潮汐影响显著。（2）河口沉积物含水率、烧失量和营养盐含量在不同季节差别不大。沉积物含水率和无机磷含量随深度的增加总体上呈现逐渐减小的趋势，而NH+4-N和NO-3-N的含量随深度的变化范围较大，无明显的变化规律。间隙水中DTP和DIP的浓度均呈现出随深度的增大先增加后减小的分布规律。间隙水中的溶解性总氮和NO-x-N浓度在夏季随着深度的增加总体上是降低的，而其在春季的垂向分布规律不明显。此外，研究区内沉积物所受到的扰动切应力主要来源于潮汐流。2.模拟了李村河口潮间带沉积物的再悬浮过程，确定了沉积物发生再悬浮的临界切应力。不同季节中，细颗粒沉积物发生再悬浮的临界切应力介于0.117-0.156N/m2之间，而潮汐流产生的切应力可达到0.410N/m2，表明潮汐流的扰动可以使细颗粒沉积物发生再悬浮。研究区内具有再悬浮潜力的沉积物的厚度小于1mm，并且该厚度存在显著的季节性差异。此外，河口区的水动力扰动强度不足以使区内粗颗粒的砂质沉积物发生显著的再悬浮。3.分析了再悬浮对水体磷负荷和沉积物磷形态的影响机制。在冬季，沉积物再悬浮促进了上覆水体中DIP的去除；在春季、夏季和秋季，沉积物再悬浮有利于內源DIP向上覆水释放。一年四季中，沉积物再悬浮均可导致內源溶解性有机磷（DOP）的释放，其释放量随沉积物侵蚀深度的增大而增大。再悬浮过程中，內源DOP与內源DIP的释放量相当，但两者均比颗粒磷的释放量低一个数量级，表明该过程中内源磷主要以颗粒态释放。在冬季，再悬浮导致沉积物中弱吸附态磷含量升高，而在夏季则导致其降低。沉积物中弱吸附态磷含量的变化主要源于悬浮沉积物颗粒对DIP的吸附和解吸。除弱吸附态磷外，铁结合态磷、自生磷、碎屑磷和有机磷的含量与再悬浮之前相比均未出现明显差别，表明再悬浮并未对沉积物中磷形态的变化和相互转化产生显著地促进作用。4.探讨了水环境条件对沉积物中磷矿化的影响。水动力扰动能够促进內源磷的矿化。相对于间歇性扰动，持续扰动更有利于磷的矿化。随着沉积物有机质含量的增加，其矿化过程中的磷释放量增大；微生物活动和外加碳源均可显著促进沉积物中有机磷的矿化；盐度的降低对于矿化过程具有抑制作用。水动力扰动条件下，沉积物中有机磷的矿化速率随着时间的延长呈现出逐渐减小的趋势。5.研究了再悬浮条件下沉积物中有机磷的光化学降解特性及其影响因素。结果表明，沉积物中有机质的光化学降解作用可增加水体中DIP、DOP的含量。其中，DIP的生成可能直接来源于沉积物中的颗粒态有机磷的降解，也可能来源于光解作用所生成的DOP的进一步降解。光降解过程中，沉积物有机质中DIP、DOP的释放量随沉积物有机磷含量的增大而增大、随沉积物粒径的减小而增大。当悬浮沉积物的浓度较低时，磷的光解释放量随悬浮物浓度的增加而增加。然而，当悬浮物浓度达到一定值时，增大悬浮物浓度对光降解释磷的促进作用不再显著，无法生成更多的磷。沉积物中有机磷的光化学降解具有显著的光谱敏感性。光降解过程中，DIP的生成量主要来源于紫外波段的照射。紫外波段和可见光波段的照射对应的DOC和DOP生成量各占两者总生成量的50%左右。更多还原

【Abstract】 Estuaries are transition zones that link up terrestrial rivers and marineecosystems. The biogeochemical behavior of the nutrient elements in estuary zoneshas significant impact on their output to the ocean. Phosphorus is one of the nutrientsthat limiting the growth of phytoplankton in the water, and the release of internalphosphorus is an important factor leading to eutrophication. Due to the low depth ofwater, the sediments in estuary zones periodically undergo resuspension under theaction of bottom shear stress caused by waves and tides. The resuspension of estuarysediments is usually accompanied by the release of internal phosphorus to theoverlying water, which is an important way of migration and transformation ofinternal phosphorus. The sediments in the estuary of Licun River, a typicalpollutant-receiving municipal river in Qingdao, are heavily polluted. The migrationand transportation of the internal phosphorus during sediment resuspension events hassignificant effect on the biological production process in the estuary zone and evenJiaozhou Bay. Based on field monitoring, sampling and analysis, the temporal andspatial distribution patterns of the phosphorus, as well as other main biogenicelements, in sediment and its overlying water are obtained. By simulating theresuspension process of the sediments, the respond characteristics of the sediments toerosion shear stress are studied and the influencing mechanism of resuspension on thephosphorus load of the overlying water and sediment P fractions is discussed. Themineralization mechanism of sediment organic phosphorus is investigated bylaboratory culture experiment and the subsequent study on the impact of sedimentproperties and environmental factors on mineralization rate is conducted. Thephotolysis characteristics of the sadiment organic phosphorus and the influence ofdifferent factors on the degradation process are explored by studying the photolysis process of suspended sediments. The main conclusions of the study are as follows:1. The physico-chemical properties of sediment and over overlying water in thestudy area are obtained through field observation and laboratory measurement. Duringall seasons, the concentration of dissolved total phosphorus (DTP), dissolvedinorganic phosphorus (DIP), NH+4-N and NO-2-N in the over overlying waterdecreases as the tide rises, and increases as the tide ebbs. While salinity, pH，dissolvedoxygen and redox potential of the over overlying water change in the opposite trend.The quality of the over overlying water is significantly affected by tide. The watercontent, loss on ignition and nutrient content of estuarine sediment do not exhibitsignificant seasonal variation. Sediment water content and inorganic phosphoruscontent decrease with depth，while the content of NH+4-N and NO-3-N in sedimentfluctuates strongly with depth. The concentration of DTP and DIP in porewaterincreases firstly and then decreases with depth. In summer, the concentrations of totaldissolved nitrogen and NO-x-N in porewater decrease with depth, while they fluctuatestrongly with depth in spring.2. The resuspension process of intertidal sediments is simulated and the shearstress of tide scouring on the sediment surface is calculated based on field monitoringdata. The critical shear stress for the resuspension of fine sediments ranges between0.117N/m2and0.156N/m2in different seasons. Yet the shear stress induce by tidalcurrent could reach0.4N/m2, indicating that fine sediments could be eroded under thedisturbance of tidal current. The thickness of the sediments with enough resuspensionpotential in the study area is less than1mm and fluctuated wildly with the seasons. Inaddition, the intensity of the hydrodynamic disturbance in the estuary area wasinsufficient for the resuspension of coarse sediments.3. The influencing mechanism of resuspension on phosphorus load of water bodyand sediment phosphorus speciation is analyzed. In winter, sediment resuspensionfacilitates scavenging of DIP from overlying water, while it benefits the release ofinternal DIP to overlying water in other seasons. During all seasons, resuspension ofsediment leads to release of internal dissolved organic phosphorus (DOP). Theamounts of DIP and DOP released via resuspension are comparable. However, they are all an order of magnitude lower than the release of particulate phosphorus. Beforeand after resuspension, no significant differences in the content of Fe-bound P,authigenic P, detrital P and organic P are observed, indicating resuspension do notpromote the transformation of sediment phosphorus speciations.4. The effects of environmental conditions on the mineralization process ofsediment organic phosphorus are investigated. Hydrodynamic disturbances canpromote the mineralization of intrenal phosphorus. Relative to intermittentdisturbance, continuous disturbance is more conducive to phosphorusmineralization.The release of phosphorus from sediment increases with the increaseof sediment organic matter content during the mineralization process.Bothmicrobialactivities and external carbon source can significantly promote the mineralization ofsediment organic phosphorus. Reduced salinity inhibited the mineralization process.Under hydrodynamic disturbances, the mineralization rate of sediment organicphosphorus decreases with time.5. The photolysis characteristics of the sediment organic phosphorus areinvestigated along with its influencing factors. The results show that the photolysisprocess of the organic matter in the sediments can increase the contents of DIP andDOP in the water. The increment of DIP might derive directly from the degradation ofthe particulate organic phosphorus in the sediment, or originate from the furtherdegradation of DOP, which is one of the photolysis products. The release amount ofDIP and DOP from sediment increases with the increase of sediment organicphosphorus content and the decrease of the sediment grain size. The photolysisrelease amount of phosphorus increases with the increase of suspended sedimentconcentration when its concentration was relatively low. However, the promotioneffect of increasing suspended sediment concentration on the photolysis release ofphosphorus is no more when the suspended sediments come to a certain concentration.The photolysis of the sediment organic phosphorus is highly spectrum-sensitive.During the process of photolysis, the generation of DIP is mainly due to theirradiation of ultraviolet. Ultraviolet and visible light both account for about50%ofthe total generation amount of DOC and DOP.更多还原