Spatial Variation in Sediment-Water Exchange of Phosphorus in Florida Bay: AMP As a Model Organic Compound

摘要

Dissolved organic phosphorus (OOP) has been recognized as dominant components in total dissolved phosphorus (TDP) pools in many coastal waters, and its exchange between sediment and water is an important process in biogeochemical cycle of phosphorus. Adenosine monophosphate (AMP) was employed as a model DOP compound to simulate phosphorus exchange across sediment-water interface in Florida Bay. The sorption data from 40 stations were fitted to a modified Freundlich equation and provided a detailed spatial distribution both of the sediment's zero equilibrium phosphorus concentration (EPC_(0-T) and of the distribution coefficient (k_(d-T)) with respect to TDP. The K_(d-T) was found to be a function of the index of phosphorus saturation (IPS), a molar ratio of the surface reactive phosphorus to the surface reactive iron oxide content in the sediment across the entire bay. However, the EPC_(0-T) was found to correlate to the contents of phosphorus in the eastern bay only. Sediment in the western bay might act as a source of the phosphorus in the exchange process due to their high EPC_(0-T) and low K_(d-T), whereas sediments in the eastern bay might act as a sink because of their low EPC_(0-T) and high K_(d-T) These results strongly support the hypothesis that both phosphorus and iron species in calcareous marine sediments play a critical role in governing the sediment-water exchange of both phosphate and DOP in the coastal and estuarine ecosystems.