34 



Sediment Analysis. The samples were concentrated and then analyzed using a 

 modified version of EPA SW-846 Method 8270 (USEPA 1997). Analysis of PAHs by Gas 

 Chromatography/Mass Spectrometry with Selected Ion Monitoring Method 8270-PAH-SIM 

 (Revision 0; GC/MS-SIM) is a WHG standard operating procedure and a more rigorous 

 method than the standard method 8270. The sample extract containing the semi-volatile 

 compounds was injected into a gas chromatograph (GC) with a narrow-bore fused-silica 

 capillary column. The temperature-programmed GC_column separated the analytes, which 

 were detected with a mass spectrometer with selected ion monitoring. In this method of 

 analysis, qualitative identifications are confirmed by analyzing standards under the same 

 conditions used for samples and comparing mass spectra and GC retention times. The mass 

 spectra of the target analytes were compared with the electron-impact spectra of authentic 

 standards for identification. Quantification was based on a multi-level initial calibration. 



2.4.3.2 Metals 



Sediment Digestion. Sediments require acid digestion for extraction and detection 

 of trace metals. Both the MAXIM laboratory (1997) and WHG (1998) utilized EPA SW- 

 846 Method 3051 (USEPA 1997), which provides a rapid multi-element acid leach of 

 sediments. A representative sample of up to 0.5 g was placed in a fluorocarbon microwave 

 vessel with 10 ml of concentrated nitric acid. The vessel was capped and heated in the 

 laboratory microwave for 10 minutes. The acid digests the sample at high temperatures. 

 After cooling, the vessel contents were filtered, centrifuged, or allowed to settle and then 

 diluted to volume and analyzed. 



Sediment Analysis. To determine concentrations of Cr, Pb, Cu, Ni, and Zn, the 

 samples were analyzed using EPA SW-846 Method 6010 (USEPA 1997), which is 

 inductively coupled plasma-atomic emission spectrometry (ICP-AES). Arsenic (As) (Method 

 7060) and Cadmium (Cd) (Method 1731) were analyzed by graphite furnace atomic 

 absorption spectroscopy (GFAA) (USEPA 1997). 



For the short core samples, EPA SW-846 Method 7471 (USEPA 1997) was used to 

 detect Hg levels using cold vapor atomic absorption. The Hg was reduced to the elemental 

 state and aerated from solution in a closed system. The mercury vapor passed through a cell 

 positioned in the light path of an atomic absorption spectrometer. Absorbance (peak height) 

 was measured as a function of mercury concentration. 



Monitoring Cruise at the New London Disposal Site, Seawolf Mound 1995 - 1998 



