ultrasonication for 1 hour. The filter is then removed and the solution analyzed 

 by flameless atomic absorption. 



The yields, as determined by addition for Ni and Cu and tracer experiments 

 for Cd, are 0.76±.06%, 0.75±.10, 0.70±.08 for Ni, Cu and Cd, respectively. The 

 precision is about ±10% at concentrations well above the detection limits of 

 0,1 ppb for Cd and 1 .0 ppb for Cu and Ni. 



Equipment and reagents are all carefully cleaned prior to Ni, Cu and Cd 

 analysis. Polypropylene vials are soaked in 6M HCl for 18 hours, rinsed with 

 deionized water, and ultrasonicated twice for three hours each time in 6M HCl. 

 They are rinsed at least three times and dried. CoCU 6H2O is purified using 

 Dowex-l-X8 anion exchange resin. It is put on in 9M HCl and eluted in 4M 

 HCl. The APIX solution is purified by filtration through a 0.4 /urn micron 

 Nuclepore filter followed by five extractions with 20 ml MIBK (methyl 

 isobutyl ketone). FUters are acid washed, as all glassware used in the filtration 

 is continuously soaked in acid. Blanks are below the detection hmits. 



Typical summer pore water profiles are shown in Figures 2-1 and 2-2 for a 

 long core and four short cores from the Jamestown North study site in 

 Narragansett Bay (located about 0.5 km north of Jamestown Island in 5-10 m 

 of water). These profiles are discussed in detail by McCaffrey et al (8). 

 Concentrations of all constituents are far higher in the top centimeter than in 

 bottom water (TCO2 increases from 2.0 to 2.8 mM, NH3 from ~5 to 100 idM, 

 PO4 = from 1-25 juM, etc.). From 1-20 cm the profiles are flat (TCO2, NH3, 

 H4Si04) or show decreasing concentrations with depth (PO4 ~, Mn''"''"). The 

 lack of a systematic increase is ascribed to transport of metabolites out of the 

 sediments by the pumping activity of organisms, rather than by ionic or 

 molecular diffusion. The sharp concentration decreases observed for Mn+ and 

 PO4 ~ are ascribed to inorganic reaction in the sediment column. Below 

 approximately 25 cm, SO4 ~ concentrations decrease and concentrations of 

 other metabohtes increase. Organisms are assumed to be absent, or at least 

 ineffective water transporters, below this depth. Metabolite concentrations 

 change sympathetically approximately as predicted by organic matter 

 decomposition: TCO2 increases twice as fast as SO4 ~ decreases NH3 increases 

 about 1/7 as rapidly as TCO2, and PO4 ~ increases about 1/150 as rapidly as 

 TCO2. 



An important point about the flat portion of the profiles is that the TCO2 

 value is considerably higlier than can be accounted for by O2 reduction, and 

 implies anoxic diagenesis. The bottom water TCO2 and O2 concentrations are 

 2.0 and 0.15 mM, respectively. Wlien all O2 is consumed, the TCO2 

 concentration will rise to 2.15 mM. NO3 reduction could conceivably increase 

 the value to 2.2 mM. 804" reduction must be postulated as the agent causing 

 the further increase to 2.8 mM. 



11 



