Search

Sediment diagenesis through microbial sulfate reduction is considered a critical process in the pH amelioration of acidic mine lakes, but is often limited by the availability of organic carbon. Organic substrates are therefore frequently added to mine lake sediments to stimulate sulfate reduction. Dissolved organic carbon (DOC) was added to sediment collected from three mine lakes, one (in Germany) with typically high concentrations of Fe and SO4and another two (in Australia) with unusually low concentrations of Fe and SO4. After the DOC additions caused the dissolved oxygen concentrations in the overlying waters to fall below 50 μmol L-1, the sediment porewater at all sites progressed through the expected anaerobic respiration sequence. The paucity of Fe and SO4in the Australian lakes did not appear to constrain microbial iron and sulfate reduction. Indeed, the low Fe concentrations appeared to promote microbial sulfate reduction in the Australian sites. In the German site, there was little evidence of sulfide production in the porewater and no changes in porewater pH profiles. In contrast, the sediment porewater from the two Australian sites exhibited sulfide production and increased porewater pH. Bioremediation of acidic lakes must consider the need to treat iron-rich water before attempting pH amelioration. [ABSTRACT FROM AUTHOR]

Pore water of sediments plays an important role in aquatic systems as mediator and as the reactive zone between the sediment and surface water. Sediment pore waters with high ionic strength from acidified pit lakes were investigated to obtain information about the influence on the lake water quality. The analysis of soluble reactive phosphorus, nitrate, ammonium, silica, dissolved organic carbon, ferrous iron, sulfate, chloride, sodium, potassium, calcium, magnesium, manganese, and total dissolved iron was predetermined as the dataset required for evaluation of water quality. The data collection procedure was optimised by designing a methodology for stabilisation, dilution of pore water samples and adaptation of analytical methods. The developed methodology was evaluated with respect to the effort required in the laboratory under routine conditions. In the first round of analyses, 72% of 638 individual analyses from a random selection of pore water profiles were found to be within the calibration ranges. Remedial actions to handle the remaining 28% of invalid analytical results are exemplified. Differences between comparative analyses of some ions by continuous flow analysis, ion chromatography, and atomic emission spectroscopy were evaluated. The majority of results measured by ion chromatography differed on a highly significant level from results measured by atomic emission spectroscopy. Possible reasons, originating from the extreme sample matrix, are discussed. Finally, the designed methodology and the results of the method comparison are used to recommend the selection of analytical methods under specific conditions. [ABSTRACT FROM AUTHOR]