AbstractsChemistry

Rapid urbanization and associated ever-increasing motor-traffic density have led to escalating amounts of pollution along road-ways in the form of aerosols and road-deposited sediments (RDS) in many parts of the world. RDS contain many pollutants such as heavy metals, metalloids and polycyclic aromatic hydrocarbons (PAHs) which are derived from vehicle exhaust emissions, vehicle tyres, brakes, body frames, asphalt road surfaces, deicing salt, paint markers, and pesticides and herbicides added to the pavement. During heavy rain, these pollutants are washed into stormwater and transported into natural water bodies and this can cause potentially toxicity to aquatic organisms. Road-deposited sediments (RDS), water baseline sediments (WBS) and baseline soil (BLS) samples from major urban roads in Kogarah Bay area, Sydney, were analyzed for several heavy metals/metalloids and polycyclic aromatic hydrocarbons (PAHs). RDS had elevated concentrations of Pb, Cd, Cu, Cr, Ni, Zn, Fe and PAHs. Both correlation and principal component analysis showed that Zn, Cu, Cr, and Sb in RDS probably originated from vehicle brakes and tyre wear while V originated mainly from road asphalt surface. The heavy metal concentrations were similar in WBS and BLS. Heavy metal fractionation data showed that potential mobility, an indication of their transportation by stormwater, decreased in the order Fe > Mn, Zn > Cu, Pb > Cr, Ni, V, Cd, Sb. Ecological risk as assessed by ISQG (Interim Sediment Quality Guidelines) and the method developed by Hakanson (1980) was low to medium in RDS and low in BLS and WBS. Of the heavy metals in RDS, Cu had the highest potential risk, whereas Zn had the lowest. The concentrations of sixteen polycyclic aromatic hydrocarbons (PAH mg/kg) in the RDS, WBS and BLS ranged from 0.40 to 7.49 (mean 2.80), 1.65 to 4.00 (mean 2.91), and 0.46 to 1.41 (mean 0.84), respectively. PAH compounds had higher concentrations of high molecular weight compounds with three or more fused benzene rings indicating that high temperature combustion processes were their predominant sources. The proportions of high molecular weight PAHs were higher in BLS than in RDS, whereas the low molecular weight PAHs were higher in RDS. All PAH compounds were observed to be the lowest in WBS. All PAHs (except naphthalene) were significantly correlated in BLS suggesting a common PAH source. The ratios of individual diagnostic PAHs showed that the primary source of PAHs in WBS and BLS was pyrogenic (combustion of petroleum (vehicle exhaust), grass, and wood) and in RDS was petrogenic (unburned or leaked fuel and oil, road asphalt) as well as pyrogenic. The potential toxicities of PAHs calculated using toxicity equivalent quotients were all low but higher for BLS than for WBS and RDS. This study also investigated the toxic effects of RDS and BLS in a range of bioassays, using water elutriates of sediments from different sites to simulate contaminated receiving waters, and solvent extracts to represent the total contaminant levels. Chemical analyses showed that…