August 8, 2013 by Dean Leverett

In July I attended an expert group meeting ‘Linking Environmental Quality Standards and Passive Samplers’, organised by the Norman Network of Reference Laboratories and hosted by the Masaryk University, Research Centre for Toxic Compounds in the Environment (RECETOX) in Brno, Czech Republic.

The meeting was attended by a range of experts on passive sampling, environmental monitoring (water, biota, sediment) and in the derivation and implementation of Environmental Quality Standards for WFD Priority Substances.

The overall objectives of the meeting were to attempt to assess the feasibility of using passive samplers to monitor against water and biota-based EQS for the WFD, to identify and address issues and potential barriers to such approaches, and develop a way forward in investigating how passive samplers could provide most benefit in the implementation of EQS.

There was no doubt amongst attendees that latest revision of the EQS Directive, poses some extremely challenging targets. These include the extremely low concentrations of certain substances that must be measured in water to demonstrate EQS compliance (which are in some cases beyond the current limits of analytical capability) and the increase in the number of substances that must be measured in biota.

The group discussed biota standards in detail, and it was considered that passive samplers are likely to be most useful in implementation of monitoring schemes for biota. It was agreed that they could have a viable role in the screening of sites prior to actual biota monitoring (i.e. to demonstrate the presence or absence of a substance) in some form of tiered framework for biota monitoring.

A potential approach was proposed in which an initial ‘preparatory’ phase applied both biota monitoring and passive sampler devices in order that the overall relative difference between measurements made in biota and passive samplers for a range of substances could be resolved. There were some concerns that the relatively high affinity of passive samplers for many of the substances for which biota standards have been set may potentially result in them being unable to ‘screen-out’ substances based merely on the presence or absence of the substance in the water column. Therefore some efforts are probably required to develop a threshold passive sampler concentration below which exceedence in biota would not be expected (and therefore biota monitoring would not be required).

There also remain some critical gaps in the battery of available passive sampling devices, especially with regard to samplers for PFOS and mercury, both Priority Substances with biota standards, and these would need to be addressed before the screening approach could be widely implemented.

Overall, the meeting was successful in coming to a general consensus on the benefits of using passive samplers within WFD (biota) monitoring, and in developing a targeted plan of immediate actions to enable their use. The outcomes of the meeting and this plan are likely to be progressed further as part of the current initiatives at an EU-level to resolve the guidance on monitoring against biota EQS.