Source: International Atomic Energy Agency – IAEA
Sediment that accumulates in the seagrasses, mangroves and marshes can be analysed to help indicate changes in the environment over periods of time, ranging from the past few years to millions of years ago. The capacity of vegetated coastal ecosystems to sequester and store carbon in their sediments can be measured by nuclear and isotopic techniques.
The IAEA Marine Environment Laboratories in Monaco use these elements to determine the rates at which organic carbon accumulates in marine sediments using sediment core samples from vegetated coastal ecosystems. Sediment cores are collected by using long plastic tubes that during sampling are able to preserve the layers of sediment accumulated over time.
The naturally occurring radioactive isotope lead-210 (210Pb), in combination with some artificial radionuclides such as caesium-137 (137Cs) are used to determine the sedimentation rates in the sediments at timescales of decades – up to around 100 years, a period during which human induced impacts on the environment have dramatically increased.
These techniques encompass radiochemical separation and measurements by alpha and gamma spectrometry adapted to each isotope. This is then combined with the measurement of organic carbon contents and its isotopes along the sedimentary record by mass spectrometry methods to assess the organic carbon stocks and burial rates.