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Possible role of carbonate dissolution in estuarine phosphate dynamics
Author(s) -
de Jonge V. N.,
Villerius L. A.
Publication year - 1989
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1989.34.2.0332
Subject(s) - calcite , estuary , phosphate , environmental chemistry , dissolution , carbonate , adsorption , organic matter , mineralization (soil science) , chemistry , sediment , geology , mineralogy , oceanography , soil science , geomorphology , soil water , organic chemistry
Field observations on the phosphate distribution in the Ems estuary show a nonconservative concentration gradient, with high summer values in the middle reaches. Experiments indicate the existence of two antagonistic mechanisms that can regulate the phosphorus cycle. Calcite is formed at sea and in the estuary and transported onshore and to the upper reaches of the estuary like other suspended matter. During this transport, part of the phosphate adsorbs onto calcite. Because pH is lower in the upper reaches of the estuary, some of the calcite dissolves and consequently some of the phosphate desorbs. Other suspended matter components, such as clay minerals and iron oxyhydroxide can also adsorb phosphate. The conditions in the upper reaches of the estuary (lower salinities and pH) are particularly favorable for these minerals to adsorb the phosphate that is available there as a result of calcite dissolution. Thus, during transport upstream, part of the calcite‐bound phosphate fraction of the suspended matter switches to adsorption sites of suspended noncalcite minerals, producing the nonconservative concentration gradient in phosphate along the estuary. This process of phosphate release may be stimulated by high carbon dioxide production resulting from the biological mineralization of organic matter in the middle and upper reaches of the estuary. The processes of sediment transport and phosphate adsorption and desorption favor the accumulation of marine phosphates as well as retention of fluvial phosphates in the estuary.