37 



The recommended maximum holding times between sampling and extraction for the 

 compounds analyzed for this study are 14 days for PAHs, 28 days for Hg, and 6 months for the 

 remaining trace metals. PAHs must be analyzed within 40 days of extraction (USEPA, 1997). 

 The 1997 sediment cores were collected on 25-26 September 1997 and stored under 

 refrigeration at the GSO in PVC tubing. The cores were split on 15-16 October 1997 and 

 sectioned for sampling. The samples were stored under refrigeration until they could be shipped 

 to the laboratory on 20 October 1997. The laboratory received the samples on 22 October 1997. 



All sample holding times were met except for the re-analyzed samples for PAHs. 

 After sample data from MAXIM were rejected, the resealed samples were sent to the WHG 

 laboratory. The WHG personnel reported that the containers arrived in good condition and 

 were almost full of material, supplying adequate sediment for the PAH analysis with limited 

 oxidation. The samples were re-extracted, resulting in a total holding time of 1 18 days • 

 between sampling and extraction. Following extraction, the samples were re-analyzed 

 within three days. Storage of the samples in airtight containers under refrigerated 

 conditions; helped to preserve data quality; previous work with PAHs has shown little 

 change in concentration in sediments held in refrigerated conditions. 



The 1998 cores were collected from the 22 to 24 July 1998 and stored under 

 refrigeration at the GSO in PVC tubing. The cores were split from 27 to 29 July 1998 and 

 sectioned for sampling. The samples were stored under refrigeration until they could be 

 shipped to the laboratory on 29 July 1998. The laboratory received the samples on 30 July 

 1998. All of the samples were extracted for PAHs on 31 July 1998 and analyzed for metals by 

 12 August. Therefore, all samples were processed well within the maximum holding times. 



2.4.4.2 Assessment of Analytical Accuracy 



Analytical accuracy is determined by the percent recovery of a known concentration 

 of a compound that is spiked to the environmental sample before analysis. The closer that 

 the numerical value of the measurement approaches the actual concentration of the 

 compound, the more accurate the measurement. The percent recovery values are calculated 

 using the following equation: 



where: A, = total compound concentration detected in the spiked sample 



A = concentration of the compound detected in the unspiked sample 

 A, = concentration of the spike added to the sample 



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



