Håkanson Lars
Department of Earth Sciences, Uppsala University, Villav. 16, 752 36 Uppsala, Sweden.
J Environ Radioact. 2005;78(2):217-45. doi: 10.1016/j.jenvrad.2004.05.005.
This paper presents a general, process-based dynamic model for coastal areas for radionuclides (metals, organics and nutrients) from both single pulse fallout and continuous deposition. The model gives radionuclide concentrations in water (total, dissolved and particulate phases and concentrations in sediments and fish) for entire defined coastal areas. The model gives monthly variations. It accounts for inflow from tributaries, direct fallout to the coastal area, internal fluxes (sedimentation, resuspension, diffusion, burial, mixing and biouptake and retention in fish) and fluxes to and from the sea outside the defined coastal area and/or adjacent coastal areas. The fluxes of water and substances between the sea and the coastal area are differentiated into three categories of coast types: (i) areas where the water exchange is regulated by tidal effects; (ii) open coastal areas where the water exchange is regulated by coastal currents; and (iii) semi-enclosed archipelago coasts. The coastal model gives the fluxes to and from the following four abiotic compartments: surface water, deep water, ET areas (i.e., areas where fine sediment erosion and transport processes dominate the bottom dynamic conditions and resuspension appears) and A-areas (i.e., areas of continuous fine sediment accumulation). Criteria to define the boundaries for the given coastal area towards the sea, and to define whether a coastal area is open or closed are given in operational terms. The model is simple to apply since all driving variables may be readily accessed from maps and standard monitoring programs. The driving variables are: latitude, catchment area, mean annual precipitation, fallout and month of fallout and parameters expressing coastal size and form as determined from, e.g., digitized bathymetric maps using a GIS program. Selected results: the predictions of radionuclide concentrations in water and fish largely depend on two factors, the concentration in the sea outside the given coastal area and/or adjacent coastal areas and the ecological half-life of the radionuclide in the sea. Uncertainties in these factors generally dominate all other uncertainties, e.g., concerning the surface water retention time, the settling velocity of the particulate fraction, the distribution coefficient regulating the fluxes in dissolved and particulate phases, the catchment area influences and the factors regulating biouptake and excretion of the radionuclide in fish. This means that the conditions in the sea are of paramount importance for the conditions in the coastal area, even for relatively enclosed coastal areas. This coastal model may be regarded as a tool for testing working hypotheses on the relative roles of different processes in different coastal areas. Such information is essential for getting realistic expectations of various remedial measures, such as coastal dredging discussed in this work.
本文提出了一个基于过程的通用动态模型，用于模拟沿海地区放射性核素（金属、有机物和营养物质）在单次脉冲沉降和持续沉降情况下的情况。该模型给出了整个定义沿海区域水中（总相、溶解相和颗粒相）以及沉积物和鱼类中的放射性核素浓度。该模型给出了月度变化情况。它考虑了来自支流的流入、直接沉降到沿海区域、内部通量（沉积、再悬浮、扩散、埋藏、混合以及鱼类的生物摄取和滞留）以及与定义沿海区域之外和/或相邻沿海区域的海洋之间的通量。海洋与沿海区域之间的水和物质通量根据海岸类型分为三类：（i）水交换受潮汐影响调节的区域；（ii）水交换受沿岸流调节的开阔沿海区域；（iii）半封闭群岛海岸。沿海模型给出了与以下四个非生物区室之间的通量：地表水、深水、ET区（即细颗粒沉积物侵蚀和输运过程主导底部动态条件且出现再悬浮的区域）和A区（即细颗粒沉积物持续积累的区域）。给出了以操作术语定义给定沿海区域向海边界以及定义沿海区域是开放还是封闭的标准。该模型易于应用，因为所有驱动变量都可以从地图和标准监测计划中轻松获取。驱动变量包括：纬度、集水面积、年平均降水量、沉降量和沉降月份，以及通过例如使用GIS程序的数字化测深图确定的表示沿海规模和形态的参数。选定结果：水中和鱼类中放射性核素浓度的预测很大程度上取决于两个因素，即给定沿海区域之外和/或相邻沿海区域海洋中的浓度以及放射性核素在海洋中的生态半衰期。这些因素的不确定性通常主导所有其他不确定性，例如关于地表水停留时间、颗粒部分的沉降速度、调节溶解相和颗粒相通量的分配系数、集水面积影响以及调节鱼类中放射性核素生物摄取和排泄的因素。这意味着海洋状况对沿海区域状况至关重要，即使对于相对封闭的沿海区域也是如此。这个沿海模型可被视为一种工具，用于检验关于不同过程在不同沿海区域相对作用的工作假设。此类信息对于对各种补救措施形成现实期望至关重要，例如本文讨论的沿海疏浚。
