The Lower Fox River is a thirty-nine mile section which supports approximately 270,000 rural inhabitants across eighteen counties, 303,000 metropolitan residents in Green Bay and Appleton, Wisconsin, and several large industrial complexes such as paper mills and power plants. The purpose of this study was twofold, a) to characterize aliphatic and aromatic hydrocarbon distribution and concentration in the Lower Fox River and b) to identify the sources of hydrocarbon contamination.
To quantify hydrocarbon contamination and distribution, nine cores were sampled downstream of the DePere Dam. Samples were analyzed for total organic carbon (TOC) using a Leco CR-412 total carbon analyzer and n-alkanes and polycyclic aromatic hydrocarbons using a gas chromatography - mass spectrometry (GC/MS).
Percent TOC values were between 0.73% and 19.9% with an average value of 6.79%. Total n-alkanes ranged from 3.96 ?g/g to 523 ?g/g and showed a strong presence of odd carbon-numbered n-alkane ratios (range of C25 to C35) which indicates the source input from terrestrial biomass. The mean polycyclic aromatic hydrocarbon (PAH) concentration was 24,800 ng/g. High molecular weight PAH (HWM PAH) concentrations dominated the distribution of hydrocarbon contaminants. River sediment samples nearest to the DePere dam contained the highest PAHs levels at 63,600 ng/g and 56,700 ng/g, respectively. Cross-plots of PAHs were used to compare diagnostic source ratios of: benzo[a]pyrene (BaA), chrysene (Chy), fluoranthene (Fl), pyrene (Py), anthracene (An), phenanthrene (Phe), indeno[1,2,3-cd]pyrene (PI), and benzo[g,h,i]pyrene (BgP) by depth and area. PAH ratios varied slightly with the core depth. Deeper core sections indicated presence of biomass combustion while the upper core sections indicated combustion of both petroleum and biomass. PAH distribution was irrespective of sampling zones. PAH and n-alkane data established primary influxes from both natural and anthropogenic pyrogenic activities. A toxicological evaluation quotient (TEQ) was calculated for the Lower Fox River core sections revealing the most elevated PAH concentrations at 2295 ng/g-dry (649 ng/g-wet), 1695 ng/g-dry (898 ng/gwet), and 2,438 ng/g-dry (829 ng/g-wet). Core section concentrations exceed the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Method B cleanup level for benzo(a)pyrene of 137 ng/g. A secondary evaluation, using the Wisconsin Department of Natural Recourses' (WDNR) threshold effect concentration (TEC), normalized sample concentrations to 1% TOC. After normalization, sample concentrations totaled 1520 ng/g-dry, 1073 ng/g-dry, and 492 ng/g-dry. PAH concentrations did not exceed WDNR TEC for PAHs at 1,610 ng/g at 1% TOC implying remediation is not presently required and river sediments currently have minimal adverse effects.
- Mcdonald, Thomas Professor