Selecting fuzzy connectives to represent heavy metal distribution in Liverpool Bay

It is known that metals and their combinations can be toxic to certain species in the aquatic environment. Heavy metal concentrations are measured annually in Liverpool Bay, UK. Each metal concentration is associated with a fuzzy set called "contaminated", defined over the set of sites where the measurements have been taken. Fuzzy aggregating operators are used to construct a set of loading indices accounting for the overall contamination of Liverpool Bay. We design and compare 10 loading indices, two of which are based on a fuzzy integral. To select a useful subset of loading indices, we calculate the similarities between them and run a relational data clustering. The final set of indices is found by nominating one representative from each cluster. The fuzzy aggregation operations chosen for the final set of loading indices are: minimum, product, maximum and arithmetic mean.