SEDIMENT SOURCE MODELING - UNMIXING OF ARTIFICIAL MAGNETIZATION AND NATURAL RADIOACTIVITY MEASUREMENTS

A new method of sediment source modelling, using a maximum likelihood unmixing algorithm, has been applied to combined magnetic and radioactivity measurements on stream bedload sediments. Particles from an iron-ore mining site can be differentiated from those derived from catchment sources and their relative contributions to the stream bedload calculated. Upstream of the mine workings, high natural catchment components of over 97% are modelled in the stream sediments by the unmixing algorithm. Despite antipollution precautions, downstream of the mine outfall the average mine waste component increases dramatically and is modelled as 47% of the bedload. The general nature of the maximum likelihood method allows very different parameters such as artificial magnetisation and natural radioactivity to be incorporated in the unmixing procedure. Consequently the unmixing method is also applicable to other disciplines.