Iron-rich Groundwater Research Articles

The restoration of species-rich heathland communities in the Netherlands

The wet heathland communities of the Ericetum tetralicis and the Cirsio-Molinietum have declined in the Netherlands due to acidification, eutrophication and lowering of the water table. To investigate the prospects of restoration of both communities, the effects of sod cutting and hydrological measures on vegetation and soil chemistry were studied in two nature reserves where these plant communities occurred decades ago. The combination of sod cutting and hydrological measures has restored several rare, groundwater dependent heathland communities. Sod cutting has restored the Ericetum tetralicis, but not the Cirsio-Molinietum. This might be due to the absence of viable seeds of characteristic species of the Cirsio-Molinietum and/or the absence of optimal site conditions, especially high phosphorus concentrations in the top soil. The high phosphorus concentrations might be a consequence of high mineralization rates and/or prolonged inundation with iron-poor water and the decreased flux of iron-rich groundwater into the topsoil. Restoration of the Cirsio-Molinietum only seems possible when sod cutting is carried out together with hydrological measures that counter prolonged inundation and reinforce the discharge of base and iron-rich groundwater.

Epigenetic pyrite in a low-sulphur, sub-bituminous coal from the central Alberta Plains

Pyrite of epigenetic origin occurs locally within the Highvale No. 2 coal seam of the central Alberta Plains. Discrete pyrite crystals appear as euhedral octahedrons (10–20 μm in size) which may coalesce and from sheets which are present on the cleat face of the coal. Iron-rich groundwaters have reacted with reduced sulphur, on and near the surface of the coal cleat and precipitated this sulphide. The source of the reduced sulphur is probably the coal itself. Distribution of pyrite within this seam is governed by cleat frequency, which, in turn, is governed by coal petrography and geochemistry. In the lower part of this seam the coal is bright, ash content is low (< 10%), the cleat is well developed and pyrite is present. In contrast, in the upper part of this seam the coal is predominantly dull, due to high intertinite maceral content and high ash (15–20%), the cleat is poorly developed and pyrite is not observed. Timing of formation of this pyrite is undetermined, but is post-cleat development.

Clogging Problems in Groundwater Heat Pump Systems in Sweden

A number of groundwater heat pump systems have been investigated to determine the extent of problems caused by the chemistry of the groundwater used. The main purpose was to investigate sites using iron rich groundwater. Fifteen facilities were studied regularly for three years. Ten of these facilities had some kind of problem caused by iron precipitation. Four of the sites were rebuilt because of severe plugging due to iron sludge in wells, pumps and pipes. In all facilities with severe problems, iron bacteria were found. Low redox potential, indicated by hydrogen sulphide in the groundwater, seems to protect from iron bacteria. In some of the systems using groundwater with H2S the problems were corrosion and sludge formation caused by sulphur oxidizing bacteria. Rapid clogging was caused by aeration of the groundwater due to improper design of the system. Knowledge of the water composition, design of the systems to minimize aeration, and control of clogging turned out to be important factors to maintain operation safety.

Simultaneous determination of iron(II) and iron(III) in aqueous solution by kinetic spectrophotometry with tiron

A kinetic spectrophotometric method that requires no prior measurement of rate constants is developed for the simultaneous determination of iron(II) and iron(III). The method is based on the aerial oxidation of iron(II) in the presence of tiron and acetate ions. The iron(III) formed is subsequently complexed with tiron and the absorbance/time relation is evaluated. The concentrations of iron(III) and iron(II) are obtained from the absorbance values at the start and at equilibrium, respectively, calculated by non-linear least-squares fitting. A linear calibration graph is obtained up to 12 μg ml −1 iron(II)/iron(III). The method is applied to iron-rich ground water.

The fate of sewage phosphorus input to a subarctic lake chain

The subarctic iron-mining town of Schefferville, Quebec discharges some 6.6 t P annually from sewage into a lake chain. P concentrations in the receiving lake build up during the winter, ice-cover period and the lake waters become anoxic. Spring flushing is rapid and pronounced, and throughout the summer lake P concentrations remain relatively low. Iron-rich groundwater inflow to the lakes promotes sedimentation of P as Fe-phosphates in the spring when lake waters are re-oxygenated. Sedimentation in the receiving lake accounts for 80% of the annual sewage P load, and only 12% passes out of the three-lake chain studied.

Geochemistry of Iron-Rich Ground Water of Southern Maryland

Field measurements of redox potential (Eh) and pH have been made on iron-rich (up to 35 p.p.m.) ground water of southern Maryland, and iron concentrations have been determined by laboratory analysis. The data obtained can be interpreted in terms of equilibrium being obtained between the ground waters and ferric minerals intermediate in properties between freshly precipitated ferric hydroxide and hematite. Apparently significant measurements of Eh and pH can be made, and thus two quasi-independent controls on iron concentrations and well-casing corrosion can be separated.