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 radioact ivity measurements on stream bedload sediments. Particles from an iron -ore mining site can be differentiated from those derived from catchme nt sources and their relative contributions to the stream bedload calc ulated. Upstream of the mine workings, high natural catchment componen ts of over 97% are modelled in the stream sediments by the unmixing al gorithm. Despite antipollution precautions, downstream of the mine out fall the average mine waste component increases dramatically and is mo delled as 47% of the bedload. The general nature of the maximum likeli hood method allows very different parameters such as artificial magnet isation and natural radioactivity to be incorporated in the unmixing p rocedure. Consequently the unmixing method is also applicable to other disciplines.