珠江口夏季有机碳的分布特征及其收支模拟研究

基于三维水质模型对珠江口夏季有机碳的分布特征及其收支进行了研究,量化了各动力学过程对有机碳分布的影响,这对于深入了解珠江口碳循环过程有重要意义.同时,采用2006年7—8月观测数据对模型进行了验证,结果显示模型模拟效果良好.研究表明,珠江口夏季有机碳呈明显的空间变化,其浓度总体上从口门向外海逐步降低,底层递减幅度大于表层;表层平均浓度为2.42 mg·L~(-1),底层平均浓度为1.91 mg·L~(-1).此外,有机碳在垂向上的分布与水体层化紧密相关,层化水域中的有机碳浓度随水深迅速下降,非层化水域上、下层的浓度差异不大.有机碳收支结果则表明,珠江口不同水域有机碳的物理、生化过程差异明显.在内伶仃洋,有机碳分布由物理过程主控,其主要来源与消耗分别为径流输送和沉降,两者分别约占该区域有机碳输入总量的83.80%、83.18%;在中伶仃洋,有机碳分布受物理和生化因素共同调控,其来源以生化产碳为主,动力输送为辅,主要耗碳项为沉降;在外伶仃洋,其西侧水域的有机碳主要来源与消耗分别为径流输送和沉降,有机碳分布受物理和生化过程共同调控,其中,物理过程占优势,而在其东侧水域,有机碳主要来源与消耗分别为生化产碳和生化耗碳,有机碳分布由生化过程主控.另外,捕食产碳和氧化耗碳分别是珠江口各生化过程中最重要的产、耗碳过程.

Simulation of organic carbon distribution and budgets during summer in the Pearl River Estuary

A three-dimensional water quality model is applied to study the distribution and flux budgets of organic carbon during summer in the Pearl River Estuary (PRE) and to quantify the influence of kinetic processes on the distribution of organic carbon, which is of great significance for understanding the carbon cycle in the PRE. The model is validated using observation data from July to August 2006 and shows a good performance in the simulation. Our results show that the organic carbon in the PRE exhibits significant spatial variations in summer with concentrations gradually decreasing from the river outlets to the open sea, and the declining amplitude is greater at the bottom than at the surface. The average concentration of organic carbon is 2.42 mg·L^-1 at the surface and 1.91 mg·L^-1 at the bottom. Moreover, the vertical distribution of organic carbon is closely related to the water stratification. In the stratified waters the concentrations of organic carbon decrease rapidly with the water depth, whereas in the non-stratified waters the concentrations at the upper and the lower layers are similar. The flux budgets of organic carbon indicate that its physical and biochemical processes are remarkably different in different areas of the PRE. At the inner Lingdingyang, the distribution of organic carbon is controlled by physical processes, and its main source and consumption are runoff transport and deposition, respectively, which account for 83.80% and 83.18% of the total organic carbon input in the region. At the middle Lingdingyang, the distribution of organic carbon is regulated by both physical and biochemical factors. The organic carbon is primarily contributed by biochemical carbon production, followed by physical transport, while it is largely consumed by deposition. At the outer Lingdingyang, the main source and consumption of organic carbon on the western side are runoff transport and deposition, and its distribution is controlled by both physical and biochemical processes, in which the physical ones are predominant. On the other hand, the organic carbon on the eastern side is primarily contributed by biochemical carbon production and consumed by biochemical carbon consumption, indicating that its distribution is largely controlled by biochemical factors. In addition, carbon production by predation and consumption by oxidation are the most important carbon production and consumption processes in the biochemical processes in the PRE, respectively.