Analysing spatiotemporal changes in sediment contamination

Coastal environments are subjected to anthropogenic threats, of which pollution by trace elements (TEs). They remain chemicals of concern because of their toxicity, their ability to be concentrated in biota and their persistence in sediment. Aware of these threats, monitoring agencies perform large environmental surveys. However, the databases generated often remain underexploited, even though they represent an important source of information for scientists. As a case study, we focused on the highly industrialized and developed coastal area of the Solent, south coast of the UK, which is also a European Marine site with protected habitats and species. To date, no scientific-based spatiotemporal trend has been published regarding its pollution in TEs. But mining of existing databases requested from the Environmental Agency and the Marine Environment Monitoring and Assessment National database showed that sediment from 32 sites were/are indeed monitored for that purpose, covering a 22 years period (1992-2013). Temporal trend analysis showed that sediment contamination significantly decreased during that time interval (45 % decrease in median). However, all TEs still show concentrations above Sediment Quality Guidelines. Important spatial variability is also present, presumably linked to the distribution of pollutant anthropogenic sources. Taken together, these data have been used to provide stakeholders with relevant scientific based tools, i.e. GIS maps of the contamination in TEs in the Solent. This regional-level assessment enables local stakeholders to create bridges between environmental scientists and local authorities and valorizes the existing databases, for future governance at the regional and national scales.