Micropollutants and metal contaminants: two case studies in the Centre-Val de Loire region
The Transenv project will use a device subsidised by the Centre-Val de Loire Region, for measuring known and unknown micropollutants.
Search for organic micropollutants using two complementary measurement techniques
Organic micropollutants are often residues from pesticides, pharmaceutical compounds and personal care products. These substances, in very low concentrations, can have a toxic effect but are difficult to measure and some are not currently subject to regulations. The Region's “young researcher” project entitled “Transenv” aims to better understand how they are transferred from surface water to groundwater. There is little data available on this, particularly as concerns the effectiveness of plant-based wastewater treatment facilities for dealing with these pollutants. Measurement campaigns will be conducted at a plant-based filtering facility, from the inlet of the water being treated to the outlet into surface water and its infiltration into groundwater.
The originality of the project lies in the coupling of two complementary measurement techniques. The first stage is carried out by passive samplers: these are devices that retain and accumulate the pollutants present in the environment during the sampling period (2 to 3 weeks), so that the passive samplers will be capable of detecting them even at very low levels. The devices, deployed directly in the river or in the groundwater table for several days, make it possible to obtain a mean value of the pollutants.
The second step requires a more specific laboratory apparatus, which combines chromatography and high-resolution mass spectrometry. This tool can be used to find and study known molecules in water samples, but also to identify those that we do not know and to define the most relevant ones to take into account. At least two measurement campaigns have been planned for the project period.
A closer look at metal transfers in a catchment basin
Metal contaminants, whether of natural or human origin, tend to become trapped in stream sediments. However, after being retained in the sediment, they may be dissolved again (i.e. remobilised) when the sediment is stirred up.
BRGM has already identified the main sources of polluting metals on the scale of the Loire catchment basin; the objective is now to refine this knowledge of their transfer process on a smaller scale. The Ramses project (Remobilisation of metals in sediments) will thus be devoted to a catchment area of a few square kilometres in the Centre-Val de Loire Region. The sediments collected will be precisely characterized, with laboratory monitoring of lead, copper and zinc concentrations in particular. The Neptune, a multi-collection, plasma-source mass spectrometer, will be used to measure the isotopic composition of these metals, which is a kind of fingerprint of the pollutants. These measures will make it possible to determine their origin and also to understand how they are transferred.
The Neptune, the first plasma source mass spectrometer installed in France, has been used at BRGM since 2002.
The Transenv project, coordinated by BRGM (the French geological survey), is being conducted in partnership with the Institute of Organic and Analytical Chemistry (ICOA) and the OPURE plant-based wastewater treatment company, for a period of 36 months. With a shorter duration (24 months), the Ramses project is also being coordinated by BRGM, in partnership with ISTO (Institut des Sciences de la Terre d'Orléans) and the consultancy firm, Geo-Hyd. Each of these two projects has a budget of around 400 k€, with a subsidy from the Centre-Val de Loire Region of almost 50%. They have also been awarded a label by the DREAM (Sustainability of water resources associated with the environment) competitiveness cluster.