Determining trace element and PCB concentrations in surface sediments from the Savannah River and Little Back River in Savannah, GA, USA.

摘要

Trace elements released into the aquatic environment eventually settle in the sediments of estuaries and coastal zones (Bellas et al., 2007). These pollutants do not remain in the sediments indefinitely but are released again to the water column by biological, chemical, and physical processes (Fichet et al., 1998). The purpose of this study was to determine trace element concentrations in surface sediments from the Little Back River (LBR) and Savannah River (SR), Georgia prior to the Savannah Harbor Expansion Project (SHEP). Surface sediment samples were collected using a Petersen or Van Veen grab aboard the R/V Margaret C. Robinson. Ten stations were sampled in both the LBR and the SR. Three grabs were collected at each station: left bank (L-bank), right bank (R-bank), and main channel (Channel). Grain size distributions were determined by wet sieving and loss on ignition was used to determine organic content. Chromium, manganese, iron, nickel, copper, zinc, cadmium, and lead were analyzed using a Perkin Elmer Optima 8000 ICP-OES. Samples were analyzed for mercury using USEPA Method 7473 on a Direct Mercury Analyzer (DMA-80). The concentration levels of all the metals in the LBR and SR decreased in the order Fe> Mn> Zn> Cr> Cu> Pb> Ni> Cd> Hg. The major finding of this study was that the Little Back River contained greater mean concentrations of all of the elements compared to the Savannah River but, manganese was the only metal with concentrations that were significantly different between the two rivers (p=0.0109) (398.61+/-71.39 ppm and 217.52+/-42.51 ppm, respectively). There were no detectable levels of the 7 PCBs analyzed in the sediment samples. Percent organic content and mean grain size significantly affected overall metal concentrations (p=0.001 for both). Because most trace elements and PCBs have a strong affinity to sediment, benthic organisms are more susceptible to PCB exposure. Once dredging begins, buried sediments may be resuspended and may have high concentrations of hazardous trace element and organic contaminants.