sedimenttraps

A sediment trap is a device used in oceanography, limnology, and environmental engineering to collect sinking particulate matter from a water column in order to quantify sediment flux. By capturing particles as they settle, traps provide a direct measure of the rate at which material is removed from the water column and deposited at depth or on the bottom.

A typical trap consists of an opening that defines a collection area and a sealed vessel or bottles that receive the settled material. It is deployed on a mooring at a chosen depth or used as a drifting unit. Over a defined deployment period, particles settle into the collection container, where the material can later be dried, weighed, and analyzed for composition, including organic carbon, inorganic carbon, calcium carbonate, nitrogen, phosphorus, and biogenic silica.

Two common configurations are moored gravity traps, which rely on gravity to guide particles into the collection bottles, and drift traps, which drift with currents to sample a broader area. Some designs use multiple sequential bottles to resolve time variation during a deployment, while others incorporate pumping or stirring mechanisms to modify collection efficiency.

Flux calculation commonly uses F = M/(A t), where M is the collected mass, A is the opening area, and t is the deployment time. The resulting flux represents the vertical transport of particulate matter through the sampled layer and is often used to estimate carbon export and deposition rates.

Interpretation of sediment trap data must consider hydrodynamic biases, resuspension, biofouling, leakage, and preservation effects. Calibration, replication, and complementary methods such as sediment cores, in situ optics, or tracers improve reliability and allow cross-validation of flux estimates.