Seafloor sediment sampler

To obtain as much data as possible, the system needed a continuous sampling capability. Also, to fulfill the requirement of rapid data analyses while at sea, nondestructive elemental analysis was selected for the method of shipboard analysis. A sampling and analysis system called the continuous seafloor sediment sampler (CS ) was developed from this work. 

The CS system is made up of three major components a seafloor sediment sampler, shipboard sample processor, and nondestructive elemental analysis instrumentation. It was described in detail previously (8). Design requirements for the seafloor sediment sampler are that it be in constant contact with the seafloor while being towed at speeds up to 6 knots, agitate only the upper surficial seafloor sediment and create a plume, contain a pumping means to sample the sediment slurry plume, and be capable of transporting the sediment slurry to a surface ship. These conditions were achieved by designing a towable sled that contained, within its structure, a submersible pump that was hose-connected to the surface ship. 

Sediment sampling of the seven stations using the CS equipment was carried out by running transects with the survey vessel parallel to, and as close as possible to, the marker buoys. The CS underwater seafloor sediment sampler was pulled at a speed of three knots and, when abreast of each buoy, the sediment collected was recorded as being from that station. The sediment wafers prepared aboard ship from the collected slurries were immediately analyzed by XRF for three elements (Mn, Fe, and Ti) and were stored for further land-based analyses of other elements. A comparison of the elemental content of the sediments collected from the seven stations by box coring and with the use of the CS equipment constituted the basis for ground-truth evaluation of the CS system. 

Platform samplers differ from gravity-driven devices in that they are lowered to the seafloor by a cable or driven to a specified location by a submersible. These systems can be either manned or unmanned. The advantages of this type of sample system are accurate positioning, pistons that are truly fixed relative to the seafloor, and less destructive sample retainers (Demars and Taylor, 1971). The sample is taken by either pushing or vibrating the sampler into the sediment. A selection of typical piston corers is presented in Table 5.2. 

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