High resolution liquid chromatography (LC-TOF) used to identify emerging organic pollutants. © BRGM - C. Bruneau

Water quality: advanced techniques to track down "emerging" pollutants

12.20.2016
So-called "emerging" pollutants - micro-pollutants that vary widely in nature and in the hazards they raise - are a new challenge for water resource management. For several years, the BRGM has been developing innovative processes to identify and characterise these "new" pollutants that are being released into the environment at the molecular level by industrial and wastewater plants and agricultural spraying. Some of these molecules, as well as their degradation products, have already been identified and are subject to regulations, but many others are not. These compounds degrade water quality and are a danger to human and environmental health.

"The EU Framework Water Directive", says the BRGM's Laurence Amalric, "was the launch pad for research in this area. Since 2008, under the national action plan for pharmaceutical residues, the BRGM and the Loire-Brittany Water Agency have been sampling for some thirty drug residues in surface and groundwater. The BRGM has since been contributing to an exceptional national sampling campaign for 411 "emerging" contaminants. But even before this concern emerged, the BRGM was already looking into the presence of pesticide residues and degradation products in water".

The LC-Tof, a liquid-phase chromatograph coupled with a high-resolution mass spectrometer, is used in the detection of hitherto unknown compounds. © BRGM - Philippe Négrel

A highly innovative analytical tool: the LC-TOF

Improving the detection and characterisation of organic compounds is a priority in tackling new forms of pollution. The BRGM recently acquired a high-resolution mass spectrometer for this purpose, which operates on the basis of ion acceleration and analysis of their speed. The LC-TOF (Liquid chromatography/time-of-flight/mass spectrometry) has two major advantages: the capacity to detect - even in very small quantities - not only known compounds, but also molecules that are unknown and therefore potentially of interest, and subsequently to characterise them.

"We are currently involved in numerous research programmes focusing on these substances", says Laurence Amalric, "particularly as part of the French Aquaref network, through our work on methodology development and the analysis capacities of high-resolution mass spectrometry, or the use and development of passive samplers (see Box).  Many other initiatives also draw on the BRGM's expertise and the possibilities of the LC-TOF, such as the European Norman network, in which we are taking part in the development of a methodological tool for the prioritisation of emerging pollutants".

Other approaches are also used specifically to detect nanoparticles (European NanoHeter and NanoRem projects) or polar contaminants, which are organic molecules that dissolve in water, via bio-indicators (InterEau and MIP WQT projects). All the knowledge acquired is providing essential input for the development of regulations, remedial measures and policies for sustainable water management in general.

A passive sampler developed under the ANR Origami project. © BRGM

Metrology: developments in passive sampling

Passive samplers are placed in rivers, streams and at various levels in water tables where they absorb and accumulate compounds in the water for analysis in the laboratory. Thanks to their flexibility, low cost and ability to detect substances at very low doses, passive samplers are a highly promising research tool, to which the BRGM is devoting considerable efforts. Under several different projects, it has calibrated and validated POCIS-type integrating samplers that target polar compounds, such as phytosanitary and pharmaceutical molecules.

Under the ANR Origami project, the BRGM and its partners developed a new passive sampler based on a molecular imprint polymer (MIP) that can measure concentrations of glyphosate (herbicide) and AMPA, a glyphosate degradation compound. A methodology for metals analysis was developed, which combines passive sampling with isotope measurements (from samples taken at depth) to improve the stratification of pollution and optimise identification of its source(s) compared to the classic approach.

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