PAHs in Sediments: Unmixing and CMB Modeling of Sources

Abstract

A chemical mass balance (CMB) model, applied to polycyclic aromatic hydrocarbon (PAH) compounds, is used to apportion PAH sources in a group of seven sediment cores in the Milwaukee Basin of the central Lake Michigan area. PAH apportionment results indicate the dominance of coke oven emissions from 1925–1976, and of highway inputs from 1983–1992 for most of the seven cores. This is consistent with results of carbon particle analysis from the same basin. Milwaukee and Port Washington appear to be primary contributors of point source inputs of PAHs from coke ovens and highway dust. Wood burning is a minor source (<13%). These findings are supported by an independent factor analysis study. Historical PAH records are also determined for the seven sediment cores. The records are unmixed and averaged over the basin. The resulting average record is then used as measured profile in a CMB model to determine PAH sources. Source profiles are historical records of the consumption of coal, petroleum, and wood, including coal used for coke production. A cubic spline technique is developed and applied for the curve fitting of original data points for all of the cores. Unmixed profiles reveal a number of features that are not seen in the original data. Wood burning, coke oven emissions, and highway dust profiles are found to resemble the national consumption records. Coal burning is a very small PAH source (<1%).