Monitoring contaminants in Lac Bay water samples by applying passive samplers : A combination of target and non-target screening approach

Samenvatting

This study applied passive samplers made from polydimethylsiloxane (PDMS) to measure time-integrated concentrations of hydrophobic organic compounds in Lac Bay, a shallow, semi-enclosed bay on the eastern side of Bonaire in the Dutch Caribbean. Characterised by mangroves, seagrass, Halimeda algal beds, and
corals, Lac Bay is a popular tourist destination and is vulnerable to anthropogenic stressors, including chemical exposure from human activities.
PDMS samplers offer several advantages: they are cost-effective, require minimal maintenance, and can detect trace levels of contaminants without the need for frequent water sampling. The study primarily targets environmental pollutants such as Polycyclic Aromatic Hydrocarbons (PAHs), Polybrominated Diphenyl Ethers
(PBDEs), and Organochlorine Pesticides (OCPs) while also gathering baseline data through non-target screening (NTS). NTS enhances the detection of emerging contaminants.
Samplers were deployed at two strategic locations within Lac Bay—near the fishermen’s pier and the public toilets at Sorobon and within a coral nursery area—to assess variations in contamination influenced by proximity to human activity. The samplers remained in situ from January to March 2023. Upon retrieval, they
were extracted and analysed using Gas Chromatography-Mass Spectrometry (GC-MS) at Wageningen Marine Research in Ijmuiden.
Despite the 'pristine' perception tourists may have of the Lac Bay environment, our analysis detected a diverse array of chemical contaminants influenced by human activities. Non-target screening highlighted emerging concerns, particularly the residues of personal care products, including a UV filter, often overlooked in routine
water quality assessments. These chemicals are likely introduced into the water primarily through swimming and grey water influence at Lac Bay. Additionally, higher levels of DEHP, a chemical associated with plastic pollution, were detected in the nursery area, suggesting potential regional contamination.
The targeted analysis identified four contaminants (8.7%) above quantification limits at the Sorobon site and only one in the nursery area. The expansive range of substances identified through non-target screening and the consistent detection of Benzo[a]anthracene confirm the proximity to a point pollution source. Although
detected levels were below the Maximum Permissible Concentration (MPC) for seawater, they highlight potential risks by being at similar levels to those at Dutch marine locations and reinforce the need for ongoing monitoring.
Since passive sampling indicates the bioavailable fraction, applying thresholds designed for grab samples (as used in the current study) to assess risks identified through passive sampling might not yield a reliable risk assessment. Analysing these compounds in matrices with established thresholds (e.g., fish, shellfish, sediment)
will provide more precise information.
Overall, the findings in this study suggest further investigation into the specific emission rates from pollution sources and their potential risks to aquatic life.