【摘要】 基于经过验证的三维水动力-水质模型,对珠江口夏季有机碳进行海陆源区分,并对海陆源有机碳的分布特征、贡献比重及其通量过程进行研究.结果表明,水平方向上,珠江口夏季陆源(海源)有机碳浓度从口门到外海逐渐降低(升高),在表、底层海水中平均浓度分别为1.45和0.87mg/L(0.97和1.05mg/L);垂直方向上,在层化水域陆源(海源)有机碳浓度从上到下逐渐递减(升高),在非层化水域海陆源有机碳浓度垂向分布较为均匀.珠江口夏季海源有机碳贡献率表层海水低于底层海水,平均贡献率为48.26%,沿向海方向海源有机碳贡献率逐渐增加——从内伶仃洋水域的4.43%逐渐提升到外伶仃洋东侧水域的81.20%.珠江口水动力条件复杂,在径流、潮汐、季风等因素的作用下陆源有机碳向海输送且向海输送量逐渐递减;海源有机碳在不同水域动力输送特征不同,西南水域向海输送,向海输送量逐渐递增;东北水域向岸输送,向岸输送量逐渐递减.陆源有机碳生化反应活性较弱,只有小部分被生化过程消耗,其迁移转化主要由沉降过程控制,而海源有机碳的迁移转化,则由口门的动力输送过程主控向外海的生化耗碳过程主控过渡.此外,海源有机碳沉降作用明显低于陆源有机碳,生化作用明显高于陆源有机碳.更多还原

【Abstract】 Based on a well-validated three-dimensional hydrodynamic-water quality model, this paper isolated marine and terrestrial organic carbon during summer in the Pearl River Estuary(PRE) to investigate their spatial patterns, relative contributions, and associated fluxes. Results showed a gradually decreasing(increasing) trend of terrestrial(marine) organic carbon from the river outlets to the continental shelf with a mean concentration of 1.45 mg/L(0.97 mg/L) and 0.87 mg/L(1.05 mg/L) at the surface and bottom water, respectively. In stratified regions, the concentrations of terrestrial(marine) organic carbon decreased rapidly(increased slowly) with depth, whereas in non-stratified regions the marine and terrestrial organic carbon were both well mixed in the whole water column. The relative contribution of marine organic carbon increased gradually from 4.43% at the inner Lingdingyang Bay to 81.20% at the east of outer Lingdingyang Bay and was lower at the surface than the bottom water with a vertical integrated contribution being 48.26%. The hydrodynamic conditions in the PRE was complicated. Under the effects of river runoff, tides, and monsoon, terrestrial organic carbon was transported offshore with a gradual decrease in its transport fluxes. However, the transport fluxes of marine organic carbon have a large heterogeneity in their spatial patterns. Specifically, marine organic carbon was transported offshore with a gradual increase in its transport fluxes along the pathway at the southwest of the PRE and in contrast was transported onshore with a gradual decrease in fluxes at the northwest. The biochemical reactivity of terrestrial organic carbon was relatively weak, and thus only a small fraction was consumed through the biochemical processes, leading to a dominant role of sedimentation in the migration and transformation of terrestrial organic carbon. Marine organic carbon was mainly controlled by the physical transport near the river outlets and the biochemical consumption at the continental shelf. In addition, the sedimentation effect of marine organic carbon was less profound and the biochemical effect was significantly more important when compared to terrestrial organic carbon.更多还原