Source apportionment of PAHs in sediments using factor analysis by time records: application to Lake Michigan, USA.

Apportionment of sources of polycyclic aromatic hydrocarbons (PAHs) by a factor analysis model based on time records for seven sediment cores from central Lake Michigan is reconsidered to provide a more quantitative treatment, and one additional factor (source). The effect of mixing depth was observed on the unmixed fluxes, and a computer program was developed for estimation of the average PAH fluxes from the reconstructed PAH records. The new factor analysis model with nonnegative constraints includes not only scaling but also back scaling which improved the source apportionment significantly. One core, CLM-A, was an outlier and was omitted from the analysis. Wood burning was identified as a third major source of PAHs in the area (20% of the total PAH flux). The other two sources petroleum (traffic), 45%, and coal (coke oven emissions), 35%, became more apparent, where the contributions are based on the sum of concentrations of 16 PAH compounds. A reduced mixing depth (1.0-1.5cm) was found to be more appropriate than the originally estimated mixing depth (1.5-2.0cm).