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2.4.2 Total Organic Carbon 



Total organic carbon, a measurement of organic matter (both labile and refractory) in 

 sediments, was measured using protocols described in the Environmental Protection Agency's 

 (EPA's) Test Methods for Evaluating Solid Waste (SW-846) Method 9060 (USEPA 1986). 

 Organic carbon in the samples was converted by the analyzer to carbon dioxide (C0 2 ), which 

 was subsequently measured by an infrared detector. The amount of C0 2 is directly 

 proportional to the concentration of carbonaceous material in the sample. Inorganic forms of 

 carbon (carbonate and bicarbonate) are not included as part of the reported total organic 

 carbon value. 



Three PDS sediment samples from the reference areas were analyzed for TOC; results 

 were accompanied by one method blank which was below detection (<0.1% TOC). In 

 addition, eight EPA Standard Reference Material (SRM) sample results were submitted with 

 the TOC samples. The recovery of TOC from these samples ranged from 91.2 to 103.5%, 

 well within acceptable limits (80-120%). 



2.4.3 Metals and PAH Analysis 



Portland Disposal Site sediment samples were analyzed for a suite of eight trace 

 metals as well as aluminum and iron. All metals were analyzed using standard SW-846 

 procedures for metals analysis (Table 2-2; USEPA 1986). Sediment samples were digested 

 using nitric acid in a microwave oven (Method 3051) except for mercury analysis (Method 

 7471). Aluminum (Al), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), nickel (Ni), 

 and zinc (Zn) were analyzed by inductively coupled argon plasma emission 

 spectrophotometry (ICP, Method 6010). Digestates can be heated in several stages allowing 

 removal of unwanted matrix components. Analysis by ICP allows simultaneous or rapid 

 sequential determination of many different metals. Atomic adsorption determinations are 

 completed as single element analyses which allow for low detection limit thresholds. Arsenic 

 (As) and lead (Pb) were analyzed using graphite furnace atomic adsorption techniques 

 (GFAA), and mercury (Hg) was analyzed using cold vapor atomic adsorption (CVAA). 



The three PDS reference station samples were analyzed for polynuclear aromatic 

 hydrocarbons (PAHs) using SW-846 Method 8270 (Table 2-1; USEPA 1986). This method 

 determines the concentration of semivolatile organic compounds from a sample extract using 

 a gas chromatograph with a mass spectrometer detector (GC/MS). Detection limits for PAH 

 compounds were within limits recommended for the method. 



Each PAH sample was spiked with three system-monitoring or surrogate compounds 

 (2-fluorobiphenyl, nitrobenzene-D 5 , and terphenyl-D^) as a measure of accuracy. Surrogate 

 samples are analyzed as a check on the laboratory's ability to extract known concentrations 

 of compounds not found normally in the sample. All PAH surrogate recoveries were within 



Monitoring Cruise at the Portland Disposal Site, July 1992 



