Authigenic apatite and octacalcium phosphate formation due to adsorption–precipitation switching across estuarine salinity gradients

Show simple item record Oxmann, JF en Schwendenmann, Luitgard en 2016-09-26T21:45:17Z en 2014-12-29 en 2015-02-06 en
dc.identifier.citation Biogeosciences, 2015, 12 (3), 723 - 738 en
dc.identifier.issn 1726-4170 en
dc.identifier.uri en
dc.description.abstract Mechanisms governing phosphorus (P) speciation in coastal sediments remain largely unknown due to the diversity of coastal environments and poor analytical specificity for P phases. We investigated P speciation across salinity gradients comprising diverse ecosystems in a P-enriched estuary. To determine P load effects on P speciation we compared the high P site with a low P site. Octacalcium phosphate (OCP), authigenic apatite (carbonate fluorapatite, CFAP) and detrital apatite (fluorapatite) were quantitated in addition to Al/Fe-bound P (Al/Fe-P) and Ca-bound P (Ca-P). Gradients in sediment pH strongly affected P fractions across ecosystems and independent of the site-specific total P status. We found a pronounced switch from adsorbed Al/Fe-P to mineral Ca-P with decreasing acidity from land to sea. This switch occurred at near-neutral sediment pH and has possibly been enhanced by redox-driven phosphate desorption from iron oxyhydroxides. The seaward decline in Al/Fe-P was counterbalanced by the precipitation of Ca-P. Correspondingly, two location-dependent accumulation mechanisms occurred at the high P site due to the switch, leading to elevated Al/Fe-P at pH < 6.6 (landward; adsorption) and elevated Ca-P at pH > 6.6 (seaward; precipitation). Enhanced Ca-P precipitation by increased P loads was also evident from disproportional accumulation of metastable Ca-P (Ca-Pmeta) at the high P site. Here, sediments contained on average 6-fold higher Ca-Pmeta levels compared with the low P site, although these sediments contained only 2-fold more total Ca-P than the low P sediments. Phosphorus species distributions indicated that these elevated Ca-Pmeta levels resulted from transformation of fertilizer-derived Al/Fe-P to OCP and CFAP in nearshore areas. Formation of CFAP as well as its precursor, OCP, results in P retention in coastal zones and can thus lead to substantial inorganic P accumulation in response to anthropogenic P input. en
dc.description.uri en
dc.language English en
dc.publisher European Geosciences Union en
dc.relation.ispartofseries Biogeosciences en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. Details obtained from en
dc.rights.uri en
dc.rights.uri en
dc.title Authigenic apatite and octacalcium phosphate formation due to adsorption–precipitation switching across estuarine salinity gradients en
dc.type Journal Article en
dc.identifier.doi 10.5194/bg-12-723-2015 en
pubs.issue 3 en
pubs.begin-page 723 en
pubs.volume 12 en
dc.description.version VoR - Version of Record en en
pubs.end-page 738 en
pubs.publication-status Published en
dc.rights.accessrights en
pubs.subtype Article en
pubs.elements-id 477122 en Science en School of Environment en
dc.identifier.eissn 1726-4189 en
pubs.record-created-at-source-date 2016-09-27 en

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