title: Seawater induced release and transformation of organic and inorganic phosphorus from river sediments.
abstract: This paper reports an investigation of the release of organic and inorganic phosphorus from a riverine sediment subjected to salinity conditions typical of estuarine mixing. Freshwater sediment was mixed with filtered river water in a thermostatted reactor, and allowed to equilibrate under aerobic conditions for 3 days. Salinity was then increased in a stepwise manner by addition of filtered low-nutrient seawater over a period of 4 days. A control experiment was performed in a second reactor by substituting ultrapure water for seawater. Using a flow injection analysis method for measurement of filterable reactive phosphorous (FRP, the so-called inorganic fraction) and filterable organic phosphorous (FOP), it was found that rapid releases of both FOP and FRP occurred at salinities of >/=10 per thousand. Over the 4-day experimental period, sediment release increased the filterable P concentration by approx. 50 microgL(-1), and of this, nearly half was initially present as FOP, which subsequently underwent rapid mineralisation to FRP. The observed behaviour may be explained by a combination of salinity induced plasmolysis of sediment bacteria and ion exchange by suspended sediment particles.
authors.affiliation: Laboratório de Biogeoquímica Ambiental, Departamento de Oceanografia e Limnologia, Universidade Federal do Rio Grande do Norte, Natal-RN 59014-100, Brazil.
authors.forename: Paulo C F C
authors.initials: PC
authors.lastname: Gardolinski
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Worsfold
authors.forename: Ian D
authors.initials: ID
authors.lastname: McKelvie
mesh_terms: D001419:Bacteria; D001682:Biological Availability; D004784:Environmental Monitoring; D005374:Filtration; D019015:Geologic Sediments / Q000737:chemistry*; D010100:Oxygen; D010758:Phosphorus / Q000032:analysis* / Q000378:metabolism*; D045483:Rivers; D012623:Seawater / Q000737:chemistry*; D012965:Sodium Chloride
chemical_list: D010758:Phosphorus; D012965:Sodium Chloride; D010100:Oxygen