Mine Water Treatment with a Pilot Scale RAPS-System
In 1985, economic reasons caused the closure of the fluorspar mine “Hohe Warte” near Gernrode in the German Harz Mountains. Though remediation works were conducted in the preceding years, mine water is currently flowing out freely of the dewatering adit and is impacting the environment and the receiving brook. The mine water is characterised by low pH-values, high conductivities and contains considerable amounts of iron, manganese, and arsenic. Annually, the mine discharges 0.7 Mio m of mine water with 7.8 tons of iron, 3.8 tons of manganese and 13 kg of arsenic. Therefore, the discharging mine water has a great potential to affect the quality of the receiving streams and resulted in a decrease of biological diversity. Based on hydrogeological and hydrochemical investigations, a passive treatment system would be able to treat the mine water. In February 2003 a pilot system was installed near the dewatering adit consisting of a settlement pond, a RAPS system and a constructed wetland. It could be shown that this passive system was able to treat an aliquot of the mine water down to ecologically acceptable standards.
PASSIVE TREATMENT OF COAL MINE DRAINAGE 1
Passive treatment systems utilize chemical and biological processes to neutralize acidity and decrease concentrations of metals. These systems have been successfully applied at numerous coal mine discharges over the past 20 years. The three most commonly applied passive unit operations are aerobic ponds/wetlands, anoxic limestone drains (ALDs), and reducing and alkalinity producing systems (RAPS). The selection of the most effective unit operation, or combination of unit operations, is based on water quality. The unit operations are sized based on flow or contaminant loads. Net alkaline water is treated with ponds and aerobic wetlands that promote iron oxidation, precipitation, and settling. Empirical data have shown that 10 - 20 grams of iron is typically removed per square meter of surface area of the pond or wetland. Net acidic water with low ferric iron and aluminum levels can be treated with ALDs, which are used to add bicarbonate alkalinity (typically 100 - 300 mg/L of alkalinity as CaCO3). To attain near maximum levels of alkalinity, ALDs are sized to maintain a 12 -15 hour detention time. Net acidic water containing ferric iron or aluminum is treated using RAPS, which add bicarbonate alkalinity via sulfate reduction and limestone dissolution. The amount of alkalinity generated is dependant on influent water quality, but empirically has been found to range from 15 - 60 grams of alkalinity (as CaCO3) per square meter of pond surface. Many of these systems are constructed to facilitate flushing of retained metals, however, the ability of these systems to maintain adequate permeability has not been determined.
Low dose radiation and intercellular induction of apoptosis: potential implications for the control of oncogenesis
Purpose: This review is focused on the potential impact of low dose radiation effects on intercellular induction of apoptosis and the underlying reactive-oxygen species (ROS)-mediated signaling pathways. Results: Transformed cells are subject to ROS-mediated apoptosis induction by non-transformed cells (‘intercellular induction of apoptosis’) and by ROS-mediated autocrine self-destruction. Sensitivity to intercellular induction of apoptosis and autocrine self-destruction are strictly correlated to the expression of the transformed state. Extracellular superoxide anions generated by transformed target cells drive the selectivity and sensitivity of this signaling system which is based on four different signaling pathways. Low dose irradiation of non-transformed cells enhances intercellular induction of apoptosis in transformed cells. This process is controlled by TGF-beta and seems to depend on the induction of peroxidase release. In addition, low dose radiation enhances superoxide anion generation of transformed target cells. Conclusions: Low dose radiation-triggered enhancement of intercellular induction of apoptosis and autocrine selfdestruction might represent a potential control system during carcinogenesis. It might be the underlying mechanism for the well-known inhibitory effect of low dose radiation on detectable transformation events. However, modifications of the complex intercellular ROS-based signaling system may also lead to configurations in which low dose radiation attenuates ROS-mediated apoptosis induction.