Phosphorus adsorption and desorption behavior on sediments of different origins

Purpose The aim of this study was to assess phosphorus-retention (P-ret) capacities via P adsorption (P-ads) and desorption (P-des) by sediments collected from six different sources associated with various origins, physical, and chemical characteristics. Materials and methods Sediment samples were collected in the State of Florida, the USA, from estuary, marine, wetland, canal, river, and lake, respectively. Phosphorus adsorption and desorption for each sediment were evaluated in three types of ambient water, i.e., marine, wetland, and canal, with different rates of phosphate added and then desorbed by chloride (Cl-). Capacities in adsorption and desorption of P by various sediments were evaluated with different isotherm models to compare their potentials and stabilities in P retention. Results and discussion Sediments from the canal and lake had the greatest native adsorbed P and the highest zero equilibrium P concentration. Sediment from the estuary had the highest P adsorption and followed by those from wetland and marine origins, respectively. Phosphorus desorption from sediments by replacing exchangeable P with Cl- (20 mmol L-1 KCl) was obtained from an excellent fit of the data by an exponential growth model of desorption kinetics. The fractions of retained P (P-ret = P-ads -aEuro parts per thousand P-des) were as high as 85-98% in the studied sediments, which displayed strong P retention capacities by all these sediments. Conclusions High capacities to retain P by sediments from estuary and wetland may play a critical role in buffering some chemical and ecological changes and benefit aquatic eco-environments by preventing P rapid release to the overlying water column.