Biogeochemical reduction processes in a hyper-alkaline leachate affected soil profile

Hyperalkaline surface environments can occur naturally or because of contamination by hydroxide-rich wastes. The high pH produced in these areas has the potential to lead to highly specialised microbial communities and unusual biogeochemical processes. This paper reports an investigation into the geochemical processes that are occurring in a buried, saturated, organic–rich soil layer at pH 12.3. The soil has been trapped beneath calcite precipitate (tufa) that is accumulating where highly alkaline leachate from a lime kiln waste tip is emerging to atmosphere. A population of anaerobic alkaliphilic bacteria dominated by a single, unidentified species within the Comamonadaceae family of β-proteobacteria has established itself near the top of the soil layer. This bacterial population appears to be capable of nitrate reduction using electron donors derived from the soil organic matter. Below the zone of nitrate reduction a significant proportion of the 0.5N HCl extractable iron (a proxy for microbial available iron) is in the Fe(II) oxidation state indicating there is increasing anoxia with depth and suggesting that microbial iron reduction is occurring

Artificial reefs: Using coal-fired power station wastes constructively for fishery enhancement

Large quantities of pulverised fuel ash (PFA) are produced by coal-fired power stations, some of which is currently dumped into the sea. The planned fitting of flue gas desulphurisation (FGD) plant in the UK would produce comparable quantities of gypsum. While a fraction of both these wastes may be used commercially, an alternative, environmentally acceptable, use for the surplus material, the construction of artificial reefs, is being investigated. Possible leaching of heavy metal ions from the reef material is being investigated by direct analysis of the blocks. Additionally there is monitoring of metal levels in reef epibiota and mobile species in comparison to concrete control and natural reef organisms