Polycyclic aromatic hydrocarbons in a small eastern siberian river: sources, delivery pathways, and behavior

The sources of polycyclic aromatic hydrocarbons (PAHs) and sources of water that deliver PAHs to an investigated river were apportioned using an end-member mixing approach. The identification of sources and tracers was based on bounding the samples by end-member sources on the mixing diagram using coordinates of source tracer concentrations. The sums of PAHs with the same molecular weight were used as PAH source tracers, and the dissolved organic carbon to base cations ratio was used as a tracer for water sources. The source contributions were evaluated by solving systems of linear equations. Most of the water samples were bound by a triangle formed by wood combustion, oil-fired boilers, and aluminum smelters in the mixing space defined by the concentrations of the principal mass 178 and 228 PAHs. There were notable seasonal variations in the PAH source contributions at each sampling site due to different contributions of groundwater, surface flow, and interflow to stream water. The differences in the PAH source contributions among sites were due to both different proportions of the flow components and different positions of the sites relative to the emission sources. Most of the bottom sediment samples were bound by a triangle formed by the same sources, but in the mixing space defined by the principal mass 252 and 276 PAHs. There were no spatial or temporal differences in the PAH source proportions among the samples because the PAH composition of the bottom sediments at each location represents the time- and space-weighted average of all the sediment loads from upstream.