N-way exploration of environmental data obtained from sequential extraction procedure

The Tucker method, extended to cope with five-way data, was considered to study the effectiveness of a chosen remediation procedure and the effect of so-called ‘aging’ on the fractionation of heavy metals like Cu, Cd, Zn, Al, Pb, Fe and Mn in contaminated soil. Specifically, the goal was to understand the influence of soil pH (way 1) on the process of immobilization of those heavy metals (way 2) supposedly bound in different forms (way 3) in heavily contaminated soil samples amended with different amounts of organic matter (way 4) over time (way 5). The huge amount of data collected can be seen as a five-way array as — pH × heavy metals × extractions × organic content × time. The results obtained through the use of the five-mode Tucker model of definite complexity showed that the changes in mobility and bioavailability of metals over time are beneficial. In general, the potentially toxic elements that were analysed became less ‘available’ over time. The same tendency was observed with an increase in soil pH. It is worth noting that the amendment of soil with organic matter seems to have no influence on the mobility reduction of heavy metals in this case. This effect was probably masked by the predominant changes in mobility of metals over time.