Sampling Errors Arising from Entrainment and Insufficient Flushing of Oceanographic Sampling Bottles
Paver, Christopher Raymond
Codispoti, Louis A
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Collection of representative water samples is important for accurately determining biological and chemical constituents. Modern carousel packages can permit bottle “soak times” to approach zero while increasing the impacts of entrainment due to their large size. In addition, some modern sampling bottles have relatively small openings relative to their volumes, a factor that inhibits flushing. Examination of qualitative evidence from various expeditions suggested that insufficient “soak times” can produce unrepresentative water samples. In this study, historical data are presented, but the emphasis is on field experiment data that better quantifies the errors that can arise from insufficient bottle flushing. The experiments suggest that under some conditions, soak times of more than 2 minutes may be required to collect representative water samples. The experiments also suggest the occurrence of stratification within bottles. The impact of insufficient soak times on some chemical gradients is discussed and improved sampling protocols are suggested.