Abstract. The patterns of variation in water quality for an acidic stream draining plantation forest overlying acidic and acid sensitive gley soils with shale and slate bedrock changed following the introduction of a 45 m deep borchole near to the stream. During drilling, air flushing of debris from the borehole cleared fracture routes for groundwater penetration to the stream via the stream bed. Consequently, there were and there remain marked increases in pH, alkalinity and calcium concentrations in the stream water. The extent of this water quality improvement varies according to flow. Under extreme highfiow conditions, most of the stream water is supplied from near surface soil water sources and acidic stream waters (pH about 4.2) result. Under baseflow conditions, the stream water pH is about 7.0 upstream and about 7.5 downstream of the borehole. Under intermediate flow conditions, the improvement in pH is most marked and values increase from around 5 to around 6.3. For acid sensitive "hard rock" areas such as those studied here, the bedrock has frequently been assumed to be both impermeable and low in base cations. This study illustrates that this view may be incorrect, and that groundwater may provide an important modifier of streamwater quality, at least for slate and shale dominated hard rock areas. Indeed, the work demonstrates clearly the potential for water quality remediation through groundwater manipulation.
The safe disposal of material considered hazardous is a natural part of good housekeeping for any industrial development. This is particularly so for the mining industry which has historically not always been so well managed in this aspect and as such has a high political profile today. Typical problems associated with mineral processing and mine waste are:9 poor water quality, through the release of sulphate, acidic waters, metals, metalloids and other undesirable substances 9 poor air quality, through the release of mineral dust and gases such as SO2, As203, Hg vapour and CO2 amongst others 9 contamination of land by the above with elevated levels of metals, sulphate and metalloids.
Recent closure of a zinc mine in southwestern France has resulted in flooding of workings and discharge of contaminated minewater from the workings, polluting a small stream. The minewater discharge is of near neutral pH and is contaminated with high levels of zinc, cadmium, manganese, iron and sulphate. With the exception of iron, concentrations of these contaminants have fallen dramatically since the discharge arose. The main source of recharge to the mine is likely to be overlying aquifers associated with near-surface weathering. A classification is proposed to explain the hydrogeochemical sources of contaminants and the changes in discharge water quality with time. Primary sources related to active sulphide oxidation dominate the minewater chemistry in the unflooded workings, whilst secondary sources related to remobilization of secondary minerals dominate in the flooded workings. Prediction of contaminant flushing rates has been carried out on the basis of this classification. Zinc and cadmium levels are expected to reach stable medium-term levels within 2–5 years of the discharge first occurring. Potential remediation strategies include plugging of the discharging mine portal and flooding of upper workings, coupled with conventional chemical and wetland treatment.
The United Kingdom emitted 628 Mt CO2 equivalent (CO2e) as greenhouse gases in 2008. United Kingdom (UK) policy is to decrease these emissions to 154 Mt by 2050. This paper investigates the role that wood construction products and wood-based panels may play in mitigating these greenhouse gas emissions. In this paper, we have concentrated on production and consumption in 2005: all solid wood products and wood based panels consumed in the UK in 2005 contained almost 16 Mt CO2e. Using established international methodologies and the ‘stock change approach’ to carbon storage, the net increase in CO2e stored in all UK wood products in 2005 was calculated to be 7·1 Mt CO2e. Applying the newer UNFCCC ‘production approach’ gave a net increase in CO2e stored in wood based panels and solid wood of 3·4 Mt CO2e in 2005, approximately half of this storage was in wood based panels. The focus of previous UK studies of carbon in construction has been new housing. We estimate that only 10% of CO2e contained in all UK solid wood and wood based panel products consumed went into new housing in 2005. We have modelled the storage of CO2e in solid wood and wood based panels for other construction sectors and used this to model changes in construction methods: if current trends in UK housing construction methods continue and are extended to other construction sectors, there is the potential to increase the annual increment of CO2e stored in wood products in construction from 9 Mt CO2e to 14 Mt CO2e (more than 2% of the total annual UK greenhouse gas emissions).
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