重金属是一类具有高毒性、持久性、生物富集性等特点的环境污染物。在工厂排污、农业面源流失以及城市污染背景下，大量含重金属的污染物以废水、废气等形式进入环境，并最终通过地表径流、大气沉降等方式到达河口，最终汇入海洋。近岸海域受人为活动影响较为显著，也是陆源污染物向外海输送的主要通道。海湾中污染物输移分布规律受陆源输入、理化环境、水动力因素、气象条件等诸多复杂因素的影响，半封闭海湾的地形特性也增加了污染物在海湾的蓄积风险，研究复杂环境条件下半封闭海湾重金属的输移分布行为具有重要的意义。

基于以上背景，本研究选取我国典型半封闭海湾胶州湾为研究区域，以重金属Pb为研究对象，分析河口和海湾水体与表层沉积物中Pb的时空分布特征，并初步识别理化因素的影响。建立SWAT模型，输出主要入湾河流各季节径流量，基于沉积物磷与铅定量关系估算各河流Pb输出通量，并在时空和量值上耦合MIKE21模型，建立起适应胶州湾的陆源-海湾水动力水质模型，分析不同季节陆源径流输入与海湾动力场作用下Pb的输移分布特征，并基于模型模拟和统计分析，揭示湾区Pb时空变异的主要影响因素。主要结论如下：

（1）水体中溶解态Pb在夏季大沽河口和冬季李村河口浓度较高，东部整体高于西部，有近岸>远岸的趋势，表明了陆源输入污染与海水的稀释作用。海湾Pb浓度水平为夏季>冬季>春季，受季节性径流与污染输入的影响。盐度、溶解氧、温度是影响海湾内溶解态Pb分布的主要理化环境因素。表层沉积物中Pb含量河口值高于海湾，西部大沽河和洋河河口沉积物Pb含量较高。湾内沉积物Pb含量无显著季节性差异。表层沉积物Pb与沉积物磷含量高度相关，体现了Pb的陆源污染输入来源。

（2）胶州湾动力场具有季节变化特征。河口区流场受径流、潮流动力和地形的影响。夏季河口区流场有利于Pb的扩散。东北角河口区流场不利于Pb的扩散。湾内涨潮流速大于落潮流速，湾口处流速最大，近岸区域流速较小。湾区西北部岸边，北部湾顶，主要河口区以及湾口处存在余环流，将增加Pb的停留时间，对其长期输移趋势产生影响。春夏主导风向分别为东风和东南风，秋冬主导风向为北风。

只有径流和潮流作用下，自河口释放的溶解态Pb扩散范围为夏季>春季>冬季>秋季。大沽河与洋河释放的溶解态Pb向南扩散，分布在湾区西部，夏季可达湾中甚至外海。墨水河与白沙河释放的溶解态Pb主要分布在东北角。李村河口释放的溶解态Pb向海湾西北部扩散。悬浮颗粒Pb扩散范围显著小于溶解态，主要分布在河口附近，夏季范围最大，细颗粒Pb扩散范围大于粗颗粒。风能扩大溶解态Pb的扩散范围。

湾区内溶解态Pb的运动轨迹与初始位置和初始潮位相有关，存在季节性差异。溶解态Pb在做往复运动的同时发生偏移，大部分向岸边输移，停留在湾区西北部、湾顶、西南部黄岛附近岸边。湾口处运动路径较为复杂，与此处半径较大的余环流有关。风力作用下，湾内溶解态Pb运动路径随风向发生不同程度的偏移。

（3）陆源河流输入至胶州湾的Pb通量在夏季最大，其中大沽河占比约为77%。夏季是陆源Pb输入胶州湾的主要污染季节。胶州湾溶解态Pb浓度高值区在落潮时向东南方向偏移，但分布位置相对稳定，具有季节性差异。春季北部湾顶有向西南呈舌状分布的高浓度带，夏季浓度高值区自西北河口向东南呈舌状分布，秋季浓度高值区位于西南黄岛向北部湾顶一带，冬季浓度高值区位于海湾东北部。胶州湾沉积物中Pb时空差异不大，主要分布在沿岸区域，与沿岸流和较弱的水流速度导致的颗粒物停留沉积有关。西部高值区位于离岸约5km处，与大沽河河口释放细颗粒Pb的扩散范围一致。东部高值区主要位于东北角西部靠近红岛岸边，与此处余环流位置相符。

Heavy metals are a class of environmental pollutants with high toxicity, persistence, and bioaccumulation. Under the background of factory discharge, agricultural non-point source loss and urban pollution, a large number of pollutants containing heavy metals enter the environment and finally reach the estuary and finally enter the ocean. The coastal waters are significantly affected by human activities, and are also the main channel for the transport of land-based pollutants to the sea. The transport and distribution of pollutants in the bay is affected by many complex factors such as terrestrial input, physical and chemical environment, hydrodynamic factors, and meteorological conditions. The topographic characteristics of the semi-closed bay also increase the risk of pollutant accumulation in the bay. The study of transport and distribution behavior of heavy metals in semi-closed bays is of great significance.

Based on the above background, this study selected Jiaozhou Bay, a typical semi-enclosed bay, as the research area, and took Pb as the research object to analyze the temporal and spatial variation characteristics in water and surface sediments.The SWAT model is established to output the seasonal runoff of the main rivers entering the bay, and the MIKE21 model is coupled in time, space and magnitude to establish a land-gulf hydrodynamic water quality model suitable for Jiaozhou Bay to analyze the distribution characteristics of Pb transport under the action of terrigenous runoff input in different seasons and the dynamic field of the bay. Based on model simulation and statistical analysis, the main influencing factors of the temporal and spatial variation of Pb in the Bay Area were revealed. The main conclusions are as follows :

(1) The concentration of dissolved Pb in the water is higher in the Dagu estuary in summer and the Licun estuary in winter, and the eastern part is generally higher than the western one, and there is a trend of near-shore > far-shore. The Pb concentration level in the bay is summer>winter>spring, which is affected by seasonal runoff and pollution input. Salinity, dissolved oxygen and temperature are the main physical and chemical environmental factors that affect the distribution of dissolved Pb in the bay. The estuary value of Pb content in the surface sediment is higher than that of the bay, and the Pb content in the estuary of the Dagu River and Yanghe River in the west is higher. There was no significant seasonal difference in Pb content in the sediments of the bay. Surface sediment Pb is highly correlated with sediment phosphorus content.

(2) The dynamic field of Jiaozhou Bay has seasonal variation characteristics. The flow field in the estuary area is affected by runoff, tidal dynamics and topography. The flow field in the estuary area in summer is conducive to the diffusion of pollutants. The flow field in the estuary area in the northeast corner is not conducive to the diffusion of pollutants. There are residual circulation on the northwestern shore of the bay area, the top of the Beibu Bay, the main estuary area and the bay mouth, which will increase the residence time of pollutants and affect the long-term transport trend of pollutants. The prevailing wind directions in spring and summer are easterly and southeasterly, while in autumn and winter the prevailing wind direction is northerly.

Under no wind conditions, the diffusion range of dissolved particles released from the estuary is summer>spring>winter>autumn. The diffusion range of suspended particulate matter is significantly smaller than that of dissolved state, mainly distributed near the estuary, the largest in summer, and the diffusion range of fine particles is larger than that of coarse particles. Wind can expand the diffusion range of dissolved Pb.There are seasonal differences in the movement trajectories of dissolved Pb in the Bay Area. While the dissolved Pb is reciprocating, most of it is transported to the shore, staying in the northwest of the bay, the top of the bay, and the shore near Huangdao in the southwest, and the rest either stay in the Qianwan of Huangdao, or return to the bay Reciprocating movement, or migration to the Yellow Sea outside the bay. The movement path at the mouth of the bay is more complicated. Under the action of wind, the movement path of dissolved Pb in the bay is shifted to different degrees with the wind direction.

(3) The high-value area of dissolved Pb concentration in Jiaozhou Bay shifted to the southeast at low tide, but the distribution position was relatively stable with seasonal differences. The temporal and spatial difference of Pb in the sediments of Jiaozhou Bay is not large, and it is mainly distributed in the coastal area. The western high-value area is located about 5 km offshore, which is consistent with the diffusion range of fine particles released from the Dagu River estuary. The eastern high-value area is mainly located in the west of the northeast corner near the shore of Hongdao.