The causes for the failure in enforcement of environmental regulations at the Giap Lai pyrite mine in northern Vietnam are considered and the environmental impacts that are associated with this mine are evaluated. It is shown that sulphide rich tailings and waste rock in the mining area represent significant sources of Acid Rock Drainage (ARD). The ARD is causing elevated metal levels in downstream water bodies, which in turn represent a threat to both human health and to aquatic ecosystems. Metal concentrations in impacted surface waters have increased after mine closure, suggesting that impacts are becoming progressively more serious. No post closure, remediation measures have been applied at the mine, in spite of the existence of environmental legislation and both central and regional institutions charged with environmental supervision and control. The research presented here provides further emphasis for the recommendation that, while government institutions may need to be strengthened, and environmental regulations need to be in place, true on the ground improvement in environmental quality in Vietnam and in many other developing countries require an increased focus on promoting public awareness of industrial environmental issues.

In some environmental situations, environmental effects caused by elevated metals resulting from past mining and smelting activities can be observed in nearby receiving water bodies several decades after mine and smelter closure. There is a growing need for managing the hazardous solid wastes such as mining wastes as well as for assessing water quality and for sustainable management of sediment quality. The work presented in this thesis examined the mobilization of metals from two metal sources: mining wastes from a mine site in Vietnam and sediments from a contaminated lake in Sweden in order to test the hypothesis that mobilization of metals will be increased, when the environmental conditions change by e.g. exposure of mining wastes to oxidative weathering, change of redox conditions at the water-sediment interface and resuspension of sediments. The results from this work under field and laboratory conditions have verified the hypothesis. The exposure of sulphidic mining wastes in oxidative weathering conditions may cause long-term production of ARD and the resultant long-term mobility of metals. The oxidation/resuspension of sediments is an important factor for the release of trace metals Zn, Cu and Cd into the solution and substantial amounts of particles and, hence, associated metals into overlying water. The concomitant changes in pH during oxidation/resuspension of sediment play a significant role in the metal release both to redox sensitive elements Fe and Mn and trace elements Zn, Cu and Cd. The concomitant change in DOC during oxidation/resuspension can also contribute to the increased mobility of study metals. The field study was coupled to intermittent operation of a hydropower plant. The mobility of the metals was higher under operation compared to non-operation and, thus, the potential impacts on dispersal of metal pollution to downstream aquatic environments. The sudden increase in water flow upon the hydropower plant upon shifts from inactive to active state could cause immediate release of particles and thus particulate metals in the overlying water. However, the magnitude and its integrated effects in fluxes of metals over the season call for further research. There is a need to further investigate the impacts of hydropower generation in a longer period of time and at a higher frequency of observations at the very start of the hydropower operation. The results from this multidisciplinary approach would give a basis for an optimal operation of the hydropower plant to minimize the metal pollution associated with the water flow.

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Water Resources Management is an international, multidisciplinary forum for the publication of original contributions and the exchange of knowledge and experience on the management of water resources. In particular, the journal publishes contributions on water resources assessment, development, conservation and control, emphasizing policies and strategies. Contributions examine planning and design of water resource systems, and operation, maintenance and administration of water resource systems.

Coverage extends to these closely related topics: water demand and consumption; applied surface and groundwater hydrology; water management techniques; simulation and modelling of water resource systems; forecasting and control of quantity and quality of water; economic and social aspects of water use; legislation and water resources protection. Water Resources Management is supported scientifically by the European Water Resources Association, a scientific and technical nonprofit-making European association

This study aimed to examine the consequent release of the metals Fe, Zn, Cu and Cd from the sediments under simulated redox changes. Two contaminated sediments, ‘A’ representing the top layer and ‘B’ representing the deeper layers taken from Lake Håcklasjön downstream of a hydropower plant in southern Sweden, were incubated in the lake water in flow-cells under both anoxic and aerated conditions. Under anoxic conditions, Fe was rapidly released from both sediments (A and B) into the solution, which was likely a result of diffusion from porewater along with the reductive dissolution of hydroxides, whereas the concentrations of dissolved Zn, Cu and Cd remained low. The opposite results occurred for all the studied metals during aeration: i.e. precipitation of Fe and a progressive release of Zn, Cu and Cd. The oxidation of ferrous to ferric Fe was the most likely process responsible for the removal of Fe from the water column from both sediments. Meanwhile the release of the trace metals was probably a result of the oxidation of sulphides, degradation of particulate organic matter or diffusion/advection. The water flow applied during the aeration period likely induced resuspension, which would be a contributing factor to the metal release by enhancing both porewater diffusion/advection and interactions between the resuspended sediments and the overlying water. The decrease in pH in overlying water of sediment A could be the reason for the faster increase in trace metal concentrations compared to that of sediment B. Copper was probably not affected by pH change, as Cu was complexed with dissolved organic carbon and carbonates using the Visual MINTEQ model. The results from the experiment show that aeration of the sediment samples is an important factor for the release of Zn, Cu and Cd into the water column. The low flow of water applied in the experiment compared to that generated by operation periods of the hydropower plant suggests that probably more metals will be released under field conditions.