Source apportionment and risk assessment of PAHs in Brisbane River sediment,Australia

Sediment samples collected over a 3-year period from Brisbane River, Australia, were analysed for fifteen (15) polycyclic aromatic hydrocarbons (PAHs). The total PAH concentrations varied from 148 to 3079 ng/g with a mean concentration of 849 ± 646 ng/g. The study revealed that PAH input into the river was primarily dominated by pyrogenic sources as evidenced by the predominance of the high molecular weight (HMW) PAHs. Temporal variations of PAHs can be linked to the level of urbanization, with continuous input of combustion related PAHs in the commercial area of the river. Inherent deficiencies in using a single source identification/apportionment approach were overcome by using diagnostic ratios, principal component analysis/absolute principal component scores (PCA/APCS) and positive matrix factorization (PMF). Both, PCA/APCS and PMF resolved four (4) identical factors or sources of PAHs, namely: gasoline emissions, diesel emissions, biomass burning and natural gas combustion. Diagnostic ratios, PCA/APCS and PMF analysis indicated that vehicular emissions were the principal sources especially within the lower section of the river while biomass burning had moderate contribution. The distribution, temporal trend and source apportionment suggest the containment of industrial-derived sources of PAHs in the river. From an ecological point of view, the risk posed by PAHs in the Brisbane River sediment appears to be low. Nevertheless, when the investigated sites were ranked using multi-criteria decision making methods(MCDM) the commercial stratum was the most contaminated. Assessment of potential risks posed by incidental dermal exposure to PAHs revealed some degree of cancer risk, especially to children.