Modelling the fate of alkanes in rivers

We consider the complete set of 35 acyclic alkanes ranging from C5H12 to C8H18 isomers as pollutants and analyse their fate in two river scenarios: Hilly regions and lowland rivers. We estimated the values of the deposition flux, concentrations in fluid phase, and in sediments of each alkane making use of the module EXWAT from the model package E4CHEM (Exposure Estimation for Potentially Ecotoxic Environmental Chemicals). Afterwards we developed a ranking of the chemicals using the DELPHI-program WHASSE, which is based on the concept of partially ordered sets (posets) and draws a Hasse diagram showing the order relationships among the chemicals considering the fate descriptors calculated. We classified the set of alkanes into four groups of isomers (C5H12, C6H14, C7H16 and C8H18) and we introduce a novel structural parameter of a Hasse diagram called the dominance degree of two groups of elements A and B in the diagram. In our case this parameter measures the degree in which A, one group of isomers. has its fate descriptors higher than the ones of the other group B (A dominates B). By the application of the dominance degree we found that heavy alkanes dominate light ones in both scenarios.