A new project in the EMSO Physical Access programme tackles marine persistent pollutants

The Mediterranean Sea is facing a threat from persistent organic pollutants (POPs), a class of synthetic chemicals which persist in the environment for years. They pose a significant danger to marine ecosystems and ultimately human health because they can build up in the tissues of living organisms as they move up the food chain (processes known as bioaccumulation and biomagnification).

To address this threat, a new research project, “Levels and air-sea exchange of persistent organic pollutants in the marginal sea of Europe: contribution to the global monitoring effort AQUA-GAPS/MONET” is currently underway in the Mediterranean Sea.

The project, led by the research centre RECETOX of Masaryk University (Brno, Czech Republic), makes use of the EMSO Physical Access Programme at the ERIC’s Regional Facility Cretan Sea, operated by the Hellenic Centre for Marine Research (HCMR).

This research aims to analyse the presence, seasonal variations, and air-sea exchange of a wide range of POPs, such as per- and polyfluoroalkyl substances (PFAS), DDT, polychlorinated biphenyls (PCBs), brominated flame retardants and others, using passive sampling. It will occur throughout four seasons, painting a complete picture of the Mediterranean’s pollution levels and their variations during one year.

Passive sampling for monitoring marine pollution

Unlike traditional methods for monitoring marine pollution that rely on analysing grab water samples or catching and analyzing fish, passive samplers are simple devices typically made of silicone sheet (or other polymer). These samplers are deployed in the water for extended periods, allowing POPs to passively accumulate within the polymer material. An equivalent process is also used to monitor airborne pollutants. The passive sampling method offers several advantages:

• Consistent Data: Passive samplers provide consistent data because their uptake rate is not influenced by variable biological factors affecting fish tissue concentrations, such as age, diet, or species variations
• Targeted Sampling: The polymer material in the samplers has a high affinity for POPs. This targeted approach ensures efficient capture and spontaneous accumulation (without external energy source) of these contaminants from the water environment.
• Simplified Monitoring: Deploying and retrieving passive samplers is significantly less labour-intensive compared to traditional fish sampling methods or active sampling of large volumes of water required to detect the ultra-trace concentrations of POPs present in seawater.
• Long-Term Trends: Passive samplers can be deployed for extended periods, allowing researchers to obtain representative time-integrative samples and track seasonal variations in POP concentrations and establish long-term monitoring trends.

Project objectives and impact

The project will involve four subsequent deployments of passive water and air samples in the Cretan Sea at the E1-M3A marine observatory to cover all four seasons. Each deployment will last three months, and the seasonality of aqueous and atmospheric concentrations of investigated compounds will be evaluated in one central laboratory, by the RECETOX team. The HCMR team successfully deployed the first set of passive samplers offshore in April at the M3A marine buoy of the Regional Facility operative site. The analysis of POPs will commence soon at the RECETOX Centre.

Passive sampling can conveniently be used for monitoring of POPs in the aquatic environment. The principle is very simple: POPs dissolve better in the passive sampler polymer than in water (or air) – thus, the chemical spontaneously diffuse to and accumulate in the sampler without the need of actively extracting them from water (or air). The time-integrating properties of passive sampling in combination with the application of a sampling matrix (silicone polymer or other suitable sorbents) with well-defined and constant properties make it possible to achieve a lower inherent variability of exposure information compared to traditional active sampling of water or air. Due to the time-integrative sampling design, limits of detection in the lower picogram per litre range of monitored POPs can be achieved, which is not feasible using conventional grab sampling. The samplers will be shipped from RECETOX, Brno, Czech Republic, and after exposure back to RECETOX for chemical analysis. Sample extraction and instrumental analysis using gas or liquid chromatography/tandem mass spectrometry will be performed in the RECETOX central laboratories, accredited for standard analysis methods CSN EN ISO/IEC 17025. The results will be used to derive aqueous and air concentrations of investigated POPs and other so-called emerging contaminants, and conclusions on air-sea exchange and pollution sources will be drawn.

The E1-M3A marine observatory has become a regular site for monitoring within the AQUA-GAPS/MONET global monitoring network of legacy POPs in surface waters at sites with background pollution. Besides providing a platform for mounting passive samplers at a remote location in the open sea, the infrastructure will provide valuable meteorological data (wind velocity, air temperature), salinity and water temperature (at or very close to deployment depth) to support the POPs aqueous and atmospheric data interpretation.

This project is a collaborative effort of RECETOX which will provide the expertise and samplers, and the HCMR team which will be instrumental in deploying and retrieving samplers from the designated location. This strategic placement ensures the samplers capture pollution representative for the marine background levels in the region.

Branislav Vrana, associated Professor of Environmental Chemistry at Masaryk University, who led the research, explains its significance: “This project will improve the understanding of investigated POPs in the Mediterranean, establishing baseline levels and identifying trends in their concentrations over time. It will also contribute valuable data to the Global Monitoring Plan of the Stockholm Convention on POPs and to the AQUA-GAPS/MONET, the global monitoring network focusing on various dissolved persistent organic pollutants and other emerging contaminants. This information will be crucial for guiding actions to protect the health of our oceans and ourselves.”