Water column, sampling techniques

Our water-column sampling techniques include in-line filtration using an all-Teflon sampling device with quartz fiber filters (0.7- xm nominal size cutoff) to differentiate between dissolved and particulate phases (21). Particulate concentrations (nanograms per gram) and subsequent calculations of partitioning between particle and aqueous phases (log KD) are based on this particle size division. This fractionation scheme precludes direct estimates of colloidal influences on Hg transport. 

Differences in integration time scales may also affect our perception of key derived parameters such as the ThE ratio (Cochran et al. 2000). This ratio (see above) compares the POC flux derived from water column " Th profiles (and thus integrating into the past) with present primary production. As classically measured using incubation techniques, primary production is an instantaneous measurement representing the phytoplankton community as sampled at a single time. Under bloom conditions, the export of POC may lag the production of fresh organic matter and ThE ratios calculated late in a bloom may be overestimates. 

The separation performance and sensitivity of a capillary electrophoresis system coupled to a phosphorous-specific flame photometric detector (FPD) has been reported for the detection of alkylphosphonic acids l20 221. The liquid junction used to decouple the electric field from the FPD showed a negligible influence on the performance of the system as compared with online UV detection. The use of an on-column sample stacking preconcentration technique allowed for injection of 900 nL. With the large injection, the detection limits for the alkylphosphonic acids in water were 0.1-0.5 xgmL 1. 

Several chemical reactions, including calcium carbonate and hydroxyapatite precipitation, have been studied to determine their relationship to observed water column and sediment phosphorus contents in hard water regions of New York State. Three separate techniques have been used to Identify reactions important in the distribution of phosphorus between the water column and sediments 1) sediment sample analysis employing a variety of selective extraction procedures 2) chemical equilibrium calculations to determine ion activity products for mineral phases involved in phosphorus transport and 3) seeded calcium carbonate crystallization measurements in the presence and absence of phosphate ion. 

At a location in the Sargasso Sea (Station 5 of EN-073, 33° N, 72° W) a series of samples through the water column was processed to compare the solution-phase 8-HQ chelation shipboard analyses with the cobalt-APDC coprecipitation technique ashore after 2.5-months storage of the samples... 

The UK National Marine Monitoring Programme (NMMP), in which samples of seawater, sediment and biota are collected for chemical analysis and application of a number of biological effects techniques, including water column and sediment bioassays and the measurement of biomarkers in fish. 

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