Trace elements in the soil-plant interface: Phytoavailability, translocation, and phytoremediation–A review

Aquatic chemistry—An introduction emphasizing chemical equilibria in natural waters: By Werner Stumm and James J. Morgan. Second Edition, John Wiley and Sons, 1981, 780 pp. $45.00 (cloth), $27.50 (paper)

The occurrence, identification and environmental relevance of vivianite in waterlogged soils and aquatic sediments

Vivianite as the main phosphate mineral in digested sewage sludge and its role for phosphate recovery

Many physical, chemical, and biological processes in freshwater ecosystems mobilize the nutrient phosphorus (P) from sediments, which in turn may contribute to the formation of harmful algal blooms...

Internal phosphorus loading in Canadian fresh waters: a critical review and data analysis

. Vivianite, Fe3(PO4)2 · 8 H2O, is a ferrous iron phosphate mineral which forms in waterlogged soils and sediments. The phosphorus (P) bound in its crystal lattice is considered to be immobilised because vivianite is stable under anoxic, reducing, sedimentary conditions. Thus, vivianite formation can make a major contribution to P retention during early diagenesis. Much remains unknown about vivianite in sediments, because technical challenges have rendered direct identification and quantification difficult. To identify vivianite and assess its significance for P burial during early diagenesis we studied the consequences of a 1992/1993 in-lake application of FeCl3 and Fe(OH)3 aimed at restoring Lake Gros-Glienicke (Berlin, Germany). In a novel approach, we firstly applied a heavy-liquid separation to the iron-rich surface sediments which allowed direct identification of vivianite by X-ray diffraction in the high-density (ρ > 2.3 g cm−3) sediment fraction. Secondly, we assessed the contribution of vivianite to P retention, combining results from chemical digestion with magnetic susceptibility data derived from magnetic hysteresis measurements. Scanning electron microscopy revealed that the dark blue spherical vivianite nodules were 40–180 μm in diameter, and formed of platy- and needle-shaped crystal aggregates. Although equilibrium calculations indicated supersaturation of vivianite throughout the upper 30 cm of the sediment, the vivianite deposits were homogeneously distributed within, and restricted to, the upper 23 cm only. Thus, supersaturated pore water alone cannot serve as a reliable predictor for the in situ formation of vivianite. In Lake Gros -Glienicke, vivianite formation continues to be triggered by the artificial iron amendment more than 20 yr ago, significantly contributing to P retention in surface sediments.

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Evidence for vivianite formation and its contribution to long-term phosphorus retention in a recent lake sediment: a novel analytical approach

An increasing number of studies constrain the importance of iron for the long-term retention of phosphorus (P) under anoxic conditions, i.e. the formation of reduced iron phosphate minerals such as vivianite (Fe3(PO4)2⋅8H2O). Much remains unknown about vivianite formation, the factors controlling its occurrence, and its relevance for P burial during early sediment diagenesis. To study the occurrence of vivianite and to assess its relevance for P binding, surface sediments of two hydrologically contrasting waters were analysed by heavy-liquid separation and subsequent powder X-ray diffraction. In Lake Arendsee, vivianite was present in deeper sediment horizons and not in the uppermost layers with a sharp transition between vivianite and non-vivianite bearing layers. In contrast, in lowland river Lower Havel vivianite was present in the upper sediment layers and not in deeper horizons with a gradual transition between non-vivianite and vivianite bearing layers. In both waters, vivianite occurrence was accompanied by the presence of pyrite (FeS2). Vivianite formation was favoured by an elevated iron availability through a lower degree of sulphidisation and was present at a molar ratio of total sulphur to reactive iron smaller than 1.1, only. A longer lasting burden of sediments by organic matter, i.e. due to eutrophication, favours the release of sulphides, and the formation of insoluble iron sulphides leading to a lack of available iron and to less or no vivianite formation. This weakening in sedimentary P retention, representing a negative feedback mechanism (P release) in terms of water quality, could be partly compensated by harmless Fe amendments.

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Matthias Rothe

Papers

The occurrence, identification and environmental relevance of vivianite in waterlogged soils and aquatic sediments

Evidence for vivianite formation and its contribution to long-term phosphorus retention in a recent lake sediment: a novel analytical approach

Sedimentary Sulphur:Iron Ratio Indicates Vivianite Occurrence: A Study from Two Contrasting Freshwater Systems.