Sampling by sediment traps

The downward flux of particles in the water column is best determined with sediment traps (e.g., Honjo and Doherty, 1988 Kremling et al, 1996 Asper, 1996). For general review, major design objectives and restrictions of this technique we refer to Chapter 1 (Section 1.3.5.2). Here we outline a somewhat routine procedure with special regard to the collection and handling of particulate TE (e.g., Kuss and Kremling, submitted). 

Several studies have shown that poisoning of the sampling cups (e.g., by addition of formaldehyde or sodium azide) cannot entirely prevent the microbial and chemical degradation of biogenic material. Thus, large portions of certain constituents may be released from 

For reliable flux data both particles and supernatants, therefore, have to be analysed. For TE analyses a 1 % solution of sodium azide in seawater (Le., a 4 1 mixture of in situ seawater, collected by GoFlo-samplers, and 5 % sodium azide stock solution in high-purity distilled water) is recommended as a preservative. 

For determination of dissolved fractions, the samples are acidified (pH 1-2) and purged for 2 h with 100 mL/min of filtered high-quality nitrogen to remove the interfering preservation reagent (hydrogen azide) fi-om solution. 

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