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Fieldwork
Published in Ingrid Chorus, Martin Welker, Toxic Cyanobacteria in Water, 2021
Martin Welker, Heather Raymond
Sediment corers, usually simple sampling devices, can be made in-house or purchased in a variety of materials. They are preferred compared to samples collected using a dredge sampler, because corers can maintain a representative vertical profile of the sediment stratigraphy, create less disturbance by shock waves and can collect more highly consolidated deposits. Sediment corers are slowly lowered to the substrate (gravity corers are released at the water surface and allowed to fall freely); they then penetrate the sediment under the sampler’s own weight or are pushed or vibrated into the sediments. Commercial corers often contain core catcher inserts and one-way valves that allow the sample to enter the tube, but not exit and to hold it in place. Inserts should not be reused between sample locations unless properly cleaned. Inserts made of plastic should not be used when collecting samples for organic analysis. Upon retrieval, the corer can be disassembled (e.g., split spoons, some core tips unscrew) and the sample laid in a container or a prepared surface for further processing. Cores from simple tubes and most other corers often drop out or can be pushed out with a clean rod. Plastic or thin-walled metal corers (or core liners) can be cut, the ends capped and secured with tape, and the entire segment sent to the laboratory. This process and the split spoon sampler reduce contamination from one segment to another in vertically stratified samples (OEPA, 2018).
Monitoring and Assessment of Pesticides and Transformation Products in the Environment
Published in José L. Tadeo, Analysis of Pesticides in Food and Environmental Samples, 2019
Ioannis Konstantinou, Dimitra Hela, Dimitra Lambropoulou, Triantafyllos Albanis
Soils and sediments are typically very inhomogeneous media; thus, a large number of samples may be required to characterize a relatively small area. Sampling sites can be distributed spatially at points of impact, reference sites, areas of future expected changes, or other areas of particular interest. Selection of specific locations is subject to accessibility, hydraulic conditions, and other criteria. The devices used for soil and sediment sampling are usually grab samplers and corers. Grab samplers are available for operation at surficial depths. Box corers or multicorers can be employed if more data on the chronologies of accumulation rates of the analytes is needed.
Distribution of surficial sediments in the ocean around New Zealand/Aotearoa. Part A: continental slope and deep ocean
Published in New Zealand Journal of Geology and Geophysics, 2019
Helen Bostock, Chris Jenkins, Kevin Mackay, Lionel Carter, Scott Nodder, Alan Orpin, Arne Pallentin, Richard Wysoczanski
The sediment samples and data were collected using a range of methods. The most common methods for sampling surface sediments from the NIWA samples (n = 10,000) were grabs (20%), dredges (30%) and corers (25%). Other methods included trawls, sleds, diver samples and underwater camera observations and some methods were not recorded. A range of different types grabs, dredges and corers have been used over the last 60 years. For example for cores; gravity, piston, kasten, trigger, vibra-, multi- and box corers have all been used. All these methods may yield a biased sample. For example, cores struggle to admit shell, pebble and cobbles (Ferguson and Paola, 1997), dredges will usually not sample unconsolidated mud, and video does not discriminate the fine fractions. Grabs and dredges bite approximately 5 cm into the seabed, video and photo are strictly surficial, and cores sample through layers. Where multiple types of corers were used at one site the trigger, multicore or box core data were used preferentially to characterise the surface sediment. This is because large gravity and piston cores disturb the top few centimetres of surficial sediment with the “bow wave” (Lotter et al., 1997). Visual seabed descriptions (divers, submersibles, deep water cameras) are often more useful in some areas. We have used any data or descriptions from the top 10 cm of all types of corer to characterise the surface sediment. Undoubtedly as samplings and observations continue to be taken in coming years the density of the sample coverage will improve. The nzSEABED database will be updated with new datasets as they become available.