Assessing the geochemical reactivity of inorganic phosphorus along estuaries by means of laboratory simulation experiments
✍ Scribed by Enrique García-Luque; Jesús M. Forja Pajares; Abelardo Gómez-Parra
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 156 KB
- Volume
- 20
- Category
- Article
- ISSN
- 0885-6087
- DOI
- 10.1002/hyp.6145
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✦ Synopsis
Abstract
Phosphate behaviour in natural estuarine systems can be studied by performing field measurements and by undertaking laboratory simulation experiments. Thus, in this paper we describe the use of a dynamic automated estuarine simulator to characterize the geochemical reactivity of phosphate in varying salinity gradients in order to study possible mechanisms of phosphate removal from the dissolved phase (e.g. formation of some kind of apatite) and how changes in pH and salinity values influence this removal. Six laboratory assays, representing various salinity and pH gradients (average pH values between 7 and 8), were carried out. The geochemical equilibrium model MINTEQA2 was employed to characterize removal of phosphate. Among the minerals from which dissolved phosphate can originate, it seems that hydroxyapatite is by far the mineral that shows the greatest saturation indexes in the experiments. Thus, there is evidence that a type of calcium phosphate (hydroxyapatite) is involved in phosphate removal in the assays. Phosphate removal by Ca^2+^ occurs sharply at salinity values of 1–2, whereas by Fe^3+^ it is relatively gradual, at least until a salinity value of 7. Copyright © 2006 John Wiley & Sons, Ltd.