Thi Bolam, who leads work package 5 (Field sampling and analysis) of the Interreg funded MONITOOL project, is a marine chemist with over 18-year experience working on trace metal and organotin levels in the marine environment and she is currently based at the Cefas Lowestoft laboratory.
- What is the purpose of Work Package 5?
Work Package 5 deals with the methods that are applied for field sample collection and for laboratory sample processing and analysis. Partners employ the same processes according to a common strategy for sampling and analysis agreed in consortium. The aim of this common strategy is to avoid operational variability in field and in laboratory works in order to obtain comparable metal concentrations data to be used for correlation studies carried out under Work Package 4.
CEFAS, as leading partner of WP5, ensures that protocols are developed in consensus, and also that sampling campaigns are done accordingly to the timeframe and methodology established by all Partners.
- The EU coastline and estuarine waterways are vast, how were the various sampling sites selected?
Sampling sites are selected in such manner to have representativeness of the whole Atlantic region; samples from the Mediterranean area are also collected to gain European consistency for further EQS adaptation (under WP6).
Each participating partner ideally targets four sampling sites with different features, characteristics and contamination levels in each Partner region. The selection of the sites must take into account the level of pollution present (particularly for Cd, Ni and Pb) at those sites to obtain a representative sampling area displaying concentrations from pristine sites to contaminated sites.
- With such a large number of partners and samples, how is variability in sampling and laboratory analyses minimised?
One of WP5 objectives is to develop standardised protocols for field samples collection and sample processing and analysis that must be followed by all Partners. The protocols define series of guidelines that will guaranty the comparability and reproducibility of data obtained from in each Partner region.
Field sampling guidelines include details on sampling sites selection, the choice of passive sampler (Diffusive in Thin Film Gradient, DGT), DGT deployment and retrieval stages, spot sampling frequency, in situ parameters, vials and containers type, material acid wash process, samples delivery to expert lab, etc. On the other hand, processing and analysis protocol focuses on the analytical methods used by all Partners or by a designated expert Partner laboratory, e.g. the analysis of Suspended Particulate Matter in seawater, trace metals analysis in seawater by Seafast-ICP-MS/Voltammetry or metals analysis in DGT by ICP-MS. Additionally, visual supports such as short videos were produced to demonstrate passive sampler deployments.
To further minimise variability, all Partner acquire the DGTs from a single source (DGT Research Ltd, UK) and we ensure that the DGTs are manufactured from a single batch for each sampling campaign.
Finally, in order to reduce inter-laboratory operational variations, a designated Partner is responsible for one type of sample processing/analysis: Cefas is responsible for the filtration of all seawater samples that are subsequently sent to IPMA who carries out the analysis of trace metals analysis by ICP-MS, whereas IST is in charge of the analysis of trace metals in seawater by voltammetry and IFREMER the analysis of trace metals in DGT by inductively coupled plasma mass spectrometry (ICP-MS.)
- What do the sampling campaigns entail and what are the potential challenges/risks and how do you mitigate those risks?
Each Partner conducted two main sampling campaigns: they took place during the wet and dry season, respectively during January-March 2018 and July-September 2018. Each sampling campaign consisted of the co-deployment of DGT and spot water sampling along the Atlantic Region and in additional sites in the Mediterranean area at both estuarine and coastal sites.
The DGTs were deployed over a “nominal” period of 5 days where spot samples were collected each day during the deployment period at low/high tide at estuarine sites or every other day at coastal sites, wherever it was practicable to do so.
Potential challenges during the sampling campaigns include the passive samplers being damaged (if in contact with the sharp edge of any solid structure due to the current flow while being deployed), being eaten by fish or in a worse case, lost or vandalised. To mitigate these potential issues, the DGTs are secured in a solid plastic frame, which in turn are wrapped around by a net. This inventive approach protects the DGTs from being in direct contact with any sharp surrounding as well as deterring the fish from trying to make the DGTs gels as food.
Vandalism can be a potential risk during the deployment, therefore sites were chosen as such that DGTs deployment locations are away from the public curiosity (?) as practicable, and wherever possible, in a secure and safe area where access is restricted (or banned from the public).
Finally, the weather can play a major role during the sampling campaign. Flexible planning is required in case weather forecast hinders the deployment or collection of the samplers, or associated spot sampling from being effective (i.e. bad weather causing access to the sampling site difficult or impossible (icy, snowy conditions) and therefore resulting in spot sampling less frequent than anticipated).
- Can you elaborate the Inter-laboratory study that sits within Work Package 5?
The Inter-laboratory study aims to develop and validate a network of DGT expert labs across the Atlantic region with the capacity to analyse DGTs deployed in coastal and transitional waters and to determine if DGT-EQS are suitable for metals.
IFREMER leads this exercise by deploying sufficient DGTs at a single chosen site over a pre-determined period. Various DGT-sample types (blank DGTs, deployed DGTs, dry resins, eluted resins) are dispatched to participating partners to be analysed in their respective laboratory. The data will be submitted using a template produced by IFREMER for consistency and the results will be processed and analysed by IFREMER once all data are collated. The aim of this cross-checking exercise is to increase the capacity for DGT analysis across all participating territories and partner laboratories ability to accurately analyse deployed DGTs.