The HTH sediment corer

Gravity corers have been in use for a long time and in many different configurations. There are, however, reasons for improvements since new manufacturing materials have become available, and demands for accurate coring and sub-sampling in both research and environmental monitoring have increased. The HTH-coring equipment, which has been tested for > 10 years by several users, is a further development of the Kajak-corer concept and has some unique features which are described here. To avoid contamination in pollution studies, the equipment is made of stainless steel and plastic (polyoxymethylene and polyethylene), and the use of these materials also makes the equipment more durable. The extruding device is the main improvement over previous versions. It consists of a piston that seals perfectly to the core tube wall, a threaded rod that can be mounted on a foot plate, and an extruder head with a stationary upper-half and a rotatable lower-half that is screwed along the rod. One 360 degrees-turn gives a 5-mm thick sediment increment that is scraped off using the sectioning tray. Sub-sampling is quick and accurate and can be performed by one person. The equipment is constructed to allow coring and sub-sampling both in summer and winter.