Concentrations of nitrite in the Sargasso Sea near Bermuda were measured monthly for 3 years using a chemiluminescent analysis capable of precise determination of concentrations as low as 1 nM. Ammonium and dissolved primary amine concentrations-were also determined occasionally. The mean nitrite concentration over the entire period declined exponentially with depth between 300 and 1000 m (r(2) > 0.99) and then declined slightly from 1.9 nM to 1.3 nM at 2600 m. From 150 to 250 m, the data had a bimodal distribution, with more than one-third of the observations comprising higher concentrations (mean similar to 147 nM) during February-April that are characteristic of the ''classic'' primary nitrite maximum (PNM) and almost two-thirds comprising low concentration values (mean similar to 17 nM) that would not have been detected by colorimetric analysis. A rapid oscillation between the two modes was observed.Combining the exponential [NO2-]-depth relationship with Redfield ratio assumptions and apparent oxygen utilization (AOU) rates for the region (Jenkins, 1982), it was calculated that at steady state, nitrite turnover rates over the 150-1000 m depth interval range from 3 to 7 days. The depth integrated nitrite inventory reaches a maximum in the spring and is correlated with peaks in primary productivity and sediment flux.Ammonium concentrations were similar to, or higher than, nitrite concentrations and also increased dramatically during winter mixing with values of 50-100 nM in the 100-300 m depth interval before decreasing to 5-20 nM values at greater depths. During the remainder of the year, concentrations were relatively constant with depth compared to the nitrite concentration profile. Copyright (C) 1996 Elsevier Science Ltd

We describe a modified (GARSIDE, 1982. Marine Chemistry, 11, 159-167) nitrite method that permits measurements down to subnanomolar concentrations and present data from Atlantic and Caribbean deepwater profiles for comparison with a published Pacific section.This important intermediate in the nitrogen cycle was detected in all samples. Concentrations were consistently lowest (0.1-0.4 nM) in oligotrophic surface waters. Below 1 km. Caribbean and Southwest Sargasso sea nitrite concentrations were 0.4-1 nM, decreasing with increasing depth; reported Pacific [NO2-] averages are several times higher. Profiles in the upper kilometer beneath the classical primary nitrite maximum (PNM) were qualitatively similar, exhibiting a smooth supra-exponential drop with depth to values of approximately 1-4 nM at 1 km.The nitrite inventory in this "tail" of the PNM above 1 km with 1 nM less-than-or-equal-to [NO2-] less-than-or-equal-to 50 nM roughly equals that in the classical PNM. Significant differences among profiles in the 0.1-1 km region are observed, consistent with nitrite pool turnover times of 3-7 days estimated from Redfield stoichiometry and tritium-helium ages. Thus seasonal and/or regional variations in factors altering the nitrite production-consumption balance, rather than transport, seem to be responsible for nitrite variability.Nitrite profiles with anomalous midwater or near-bottom fine structure, including multi-point maxima and minima, were found along the Venezuelan continental margin and at approximately 13-degrees-N. These features are tentatively ascribed to boundary effects, as hydrographic and circumstantial evidence suggests that these waters interacted previously with the bottom.

Between July 1978 and July 1979, monthly samples of water collected near the mouth of the Columbia River were analyzed for Pu and Am to budget the annual quantity of these radionuclides exported to the adjacent coastal zone. During this period, approximately 70mCi of 239, 240Pu and 17 mCi of 241Am were carried by the river to the ocean. From the depositional history of a fine-grained sediment core raised from within the Columbia River estuary, an estimated 4–8 Ci of 239, 240Pu and 1–2 Ci of 241Am have entered the north-east Pacific Ocean by river transport since the late 1950s. This input would have increased the transuranic inventories in adjacent coastal sediments by at most 2·5 times those expected as a result of direct atmospheric fallout.