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Sediment Fingerprinting

Teagasc research is using forensic geoscience to determine the source of sediment in our watercourses.

Delivery of sediment to watercourses can have environmental and economic impacts. Elevated suspended sediment in rivers, as a result of enterprises such as agriculture and forestry, can result in decreased light penetration in rivers, affecting aquatic flora and fauna. Excessive sediment in a river bed can smother aquatic habitats for species such as the Freshwater Pearl Mussel and Atlantic salmon.

Dr. Daire Ó hUallachain (Teagasc Johnstown Castle) highlighted that “it is important to identify sediment sources in order to target cost-effective watercourse management”.

Sediment fingerprinting is a novel technique for quantifying the relative contribution of sediment from different sources in a catchment. The approach collects soil samples from potential sediment source areas (e.g. channel banks, tillage fields, forestry). The distinctive signature from each source area can then be identified from natural properties such as geochemistry, radionuclides, magnetics and colour. Sediment collected in a stream is a mixture of sediments from each of the source areas. Sediment fingerprinting involves separating stream sediment out into the different source area sediments, thus allowing each source to be quantified.

Dr. Ó hUallacháin said that “research on sediment fingerprinting is being undertaken in three catchments from the Teagasc Agricultural Catchments Programme. The technique offers valuable insight into the relative importance of different sources within agricultural landscapes. It helps identify source areas and facilitates targeting of mitigation measures, in turn helping to achieve water quality objectives under the EU Water Framework Directive”.