PARENT SESSION
2C Advances in life cycle impact assessment; water and other issues
9:00 AM to 7:00 PM, Wednesday, 09 May 2001

(W/MC262) The Development of a Salinity Indicator for LCIA of Minerals Projects.

Hansen, Yvonne¹, Stewart, Mary ¹, Petrie, James¹, ¹

ABSTRACT- Assessment of the environmental stability of solid wastes and slurries in minerals' projects is compounded by the complexity of leachate generation and mobility processes, and, in particular, by the difficulty in predicting the chemical speciation of soluble species mobilised by this activity. Apart from the lack of good thermodynamic information for hydrometallurgical processes, the temporal and spatial dimensions of such impacts are difficult to ascertain. In this work, we propose a methodology for quantifying the environmental impact associated with solid wastes generated by this industry, based on the use of mid-point LCIA indicators. This methodology involves a consideration of leachate generation processes, and subsequent mobility of leached components into ground-water, with due attention given to an analysis of pertinent physico-chemical phenomena. This analysis results in the identification of a time-dependent concentration profile of mobile constituents at the interface between the waste deposit and the surrounding environment. The integration of leachate prediction modelling with plume dispersion modelling tools provides a measure of the extent to which a land mass is affected by any subsequent leachate migration. In this way it is possible to obtain a time dependent footprint of affected land which could be used as a semi-site specific indicator of the environmental impact of solid waste management practices. We explore this approach for the specific case of salinity plumes from fly-ash impoundments. A salinity mid-point LCIA indicator is developed, based on predictions of ionic strength of the leachate plume. Some comment is offered on the use of reference compounds, the calculation of equivalency factors for other species, and the exploration of the link between salinity and metals' toxicity.

Key words: Life Cycle Impact Assessment, Salinity, Solid Waste Management, Water Management