Sample Pretreatment . 



i) Seawater and suspended matter 



No preparation was required for the filtrate. Tiio filtrate weight was 

 determined so tliat the particulate metal fraction could be normalized to volume 

 of sample filtered. 



Particulate matter on membranes was dried for 72 hours in a desiccator. 

 The dried filters were placed in vials, submerj^ed in 3 ml of 1 . ON Ultrex 

 HWO^, and leached for at least 48 hours at 70 C. 



2) Molluscs 



Individuals from replicate groups were shucked with acid-rinsed stainless 

 steel tools, rinsed with dis t i 1 led-deionized water, and homogenized with a 

 stainless steel and Teflon tissue grinder. The homogenate was dried for 72 

 hours at 80 C and ground with quartz mortar and pestle. 



Saiaple Analyses. 



1) Seawater and suspended matter 



Dissolved metal determinations were made on 250 ml aliquots of seawater 

 after preconcentrat ion and isolation of the metals of interest by organic 

 complexat ion/extract ion (Uanielsson et al., 1978). Instrumental determinations 

 were done by graphite-furnace atomic absorption spectrophotometry for Cr , Cu, 

 Fe, Pb , and Zn. Analytical precisions are listed in Table 3. One extraction 

 was done with each sample collected. Metal concentrations in the leachate of 

 particulate matter were determined directly by graphite-furnace atomic 

 absorption spectrophotometry. 



2) Molluscs 



Analyses were performed on three replicate samples from each collection 

 site. Approximately one gram (accurately weighed) of dried and ground 

 homogenate was covered with 5 ml Ultrex HNO^, and reflux digested at 70 C 

 for six hours. Digests were filtered through acid-rinsed glass fiber filters 

 and diluted to volume (50ml for oysters, 25inl for mussels). Duplicate one-gram 

 sairiples of NBS Standard Reference Oyster Tissue were included with each group 

 of digests for quality control demonstration. Table 4 summarizes the similar 

 results of the NBS Oyster Tissue determinations from the past two years, which 

 compare acceptably with limits given by NBS. Reagent blanks and procedural 

 blanks were run with each group, but were everywhere either less than 1% of the 

 analytical levels or below the level of detection. Instrumental determinations 

 for Cr, Cu, Fe , and Zn were made by flame atomic absorption spectrophotometry, 

 with an Instrumentations Laboratory Video 12 AAS. 



