Introduction

Anthropogenic pollution enters the marine environment through a variety of sources (industry and agriculture, atmospheric deposition, offshore oil and gas production, sewage from wastewater treatment activities via rivers,...) and may have a severe impact on health and functioning of the marine ecosystem. These compounds can persist for long times in the environment and may be resistant to environmental degradation. Many of these compounds are toxic and may bio-accumulate in the marine food chain. Examples found in the marine environment are pesticides, anti-foulants, pharmaceuticals and heavy metals. Compliance monitoring of these pollutants is required under the Water Framework Directive (WFD/2000/60/EC) and the Marine Strategy Framework Directive (MSFD/2008/56/EC). The MSFD aims to protect more effectively the marine environment across Europe by achieving and maintaining Good Environmental Status (GES) of the EU marine waters by 2020. It defines Good Environmental Status (GES) as: "The environmental status of marine waters where these provide ecologically diverse and dynamic oceans and seas which are clean, healthy and productive". Descriptor 8 recommends that "Contaminants are at a level not giving rise to pollution effects" and that monitoring programs include the assessment of concentrations of contaminants in the environment (water, sediment, biota). Traditional monitoring taken by spot sampling is presently accepted as the general technique of choice but may be costly and time-consuming. They provide a snapshot of the environment at a specific time and place and may miss episodic changes in the water composition. Sensitivity is often an analytical challenge because of the low concentrations in the water column. Additionally, the marine ecosystem is very complex and influenced by tides, currents and point source impacts so that these traditional ways are often not adequate in the context of environmental risk assessment. One way to overcome this problem is the use of passive samplers (PS).

Passive Sampling

Silicone rubber sheets passive samplers can be used for the analysis of a broad range of environmental contaminants including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and organochlorines (OCs). More information on the different groups of toxic substances and their effects on the marine environment can be found in the Marine Ecotoxicology Portal.
The silicone rubber sheets are deployed in seawater for a period during which they absorb the hydrophobic organic chemicals (passive diffusion) from the water at a rate directly proportional to their aqueous concentration providing integrative sampling. As the sampling continues, the less hydrophobic contaminants gradually approach their equilibrium concentration in the sampler, i.e. their maximum amount determined by the aqueous concentration and the polymer-water partition coefficients (Kpw). Except for the Kpw, the final amount absorbed depends on the physical dimensions of the rubber sheets, the temperature and salinity of the water and its physical movement, and deployment time. After retrieval, the rubber sheets are analyzed to determine the concentrations of the hydrophobic organics. The sheets are spiked with performance-reference compounds (PRCs) prior to deployment and their dissipation is used to quantify the amount of water that the sheets have effectively sampled. This allows to calculate freely dissolved aqueous concentrations from the contaminant amounts absorbed during deployment.

References

  • Law R., Hanke Georg, Angelidis Michael, Batty J., Bignert A., Dachs J., Davies I., Denga Y., Duffek A., Herut B., Hylland K., Lepom Peter, Leonards P., Mehtonen J., Piha Henna, Roose J., Tronczynski Jacek, Velikova V., Vethaak D. (2010). Marine Strategy Framework Directive. task group 8 : report contaminants and pollution effects.

  • Monteyne E, Roose P, Janssen CR. Application of a silicone rubber passive sampling technique for monitoring PAHs and PCBs at three Belgian coastal harbours. Chemosphere. 2013; 91:390–398. [PubMed: 23290177]

  • White, Philip: Passive Sampling for Quality Monitoring of Irish Marine Waters, Doctoral Thesis. Dublin Institute of Technology, 2014.

  • Smedes, F., and Booij, K. 2012. Guidelines for passive sampling of hydrophobic contaminants in water using silicone rubber samplers. ICES Techniques in Marine Environmental Sciences No. 52 .20 pp.