Inputs of Total and Labile Dissolved Metals from Six Facilities Continuously Discharging Treated Wastewaters to the Marine Environment of Gran Canaria Island (Canary Islands, Spain)

The presence of ten metals (Cd, Ni, Pb, Cr, Cu, Zn, Al, Fe, Mn, and Co) was investigated in the final discharge of six facilities, including four wastewater treatment plants, which were continuously discharging treated wastewater to the coastal environment in Gran Canaria Island. A four-day sampling campaign was carried out at each facility in July 2020, in which both the spot samplings technique and the diffusive gradient in thin-film technique (DGT) were carried out to measure total dissolved metals and the in situ labile metal fraction, respectively. After the necessary sample preparation steps, measurements were carried out by ICP-MS for both samplings. Raw data referred to the spot total dissolved and DGT-labile metal concentrations were reported. In general, the average metal concentrations were dispersed in a broad range. As expected, the highest metal contents were found in those facilities with larger industrial contributions. The values of annual average environmental quality standards (AA-EQS) were used to assess the total dissolved metal concentrations for every metal in every final discharge. In only one of the studied facilities, some metals (Ni and Zn) exceeded these EQS within the receiving waterbody, highlighting the need for more efficient treatment targeted towards a specific discharging-water quality. In addition, the total dissolved and labile metal daily fluxes of discharge were calculated to estimate the contribution of every effluent to the receiving water bodies

An international intercomparison exercise on passive samplers (DGT) for monitoring metals in marine waters under a regulatory context

In order to move forward in the acceptance of a novel contaminant monitoring technique (Diffusive Gradients in Thin-films: DGT) for assessment of marine water bodies, sensu the WFD, an Inter-Laboratories Comparison (ILC) exercise (nine Europeans laboratories) was organized in the framework of the Interreg Atlantic Area MONITOOL project, which focused on the use of the DGT technique for the measurement of WFD priority metals (Cd, Ni and Pb). Reproducible results were obtained for each metal by several laboratories, supporting the assertion that DGT analysis can be performed satisfactorily by laboratories experienced in measuring metals at trace levels in marine environments, even if they have limited practice in DGT analysis. According to the Z-score analysis, among the 9 participating laboratories, 3 had 100 % of satisfactory results for Cd, Ni, and Pb, 3 had >80 % satisfactory results and 2 had about 60 % satisfactory results. This work highlights the need to clearly describe the DGT method in order to control sources of contamination during analytical steps, in particular the resin gel retrieval and the elution steps. Such international intercomparison exercise is an important step to develop the laboratory network involved in DGT analysis and contributes to the improvement of data quality

Towards the use of DGT technique in a regulatory context for monitoring metals in marine water bodies : Results of an International Intercomparison Exercise

In order to move forward in the acceptance of a novel contaminant monitoring technique for the status assessment of marine water bodies, sensu the Water Framework Directive (WFD), an Inter-Laboratories Comparison (ILC) exercise was organized by Ifremer in the framework of the MONITOOL project - New tools for monitoring the chemical status in transitional and coastal waters under the EU WFD. This ILC focused on the use of DGT technique for the measurement of WFD priority metals (Cd, Ni and Pb). The objectives of this ILC were to test the performance of laboratories when analysing DGTs and to identify the critical handling (resin gel retrieval and elution) and analytical steps when working with DGT samplers, to establish recommendations to prevent misleading results

A Good Practice Guide for the Use of DGTs. Sampling of metals in transitional and coastal waters by Diffusive Gradient in Thin films (DGT) technique. MONITOOL project

This document provides guidance on best practice for the use of Diffusive Gradient in Thin films (DGT) passive samplers devices in sampling of transitional and coastal waters for water quality monitoring. The methodology1 to be addressed in this guide was developed by the consortium of the European Union’s Interreg MONITOOL Project in order to ensure comparability and reproducibility of the data obtained from each project Partner in different regions. The guide provides practical and detailed information on all the aspects to be considered before the deployment of these devices and the essential steps for their deployment, retrieval and subsequent sample processing for the analysis of trace metals. Although it is not aimed as a standard protocol, these guidelines address the need for a common approach and the intention to promote best practice

Guide des bonnes pratiques pour l’utilisation des DGTs. Échantillonnage des métaux dans les eaux de transition et côtières par la technique du Gradient de Diffusion en couche mince (DGT). Projet MONITOOL

Le présent document fournit des instructions pour les meilleures pratiques relatives à l’utilisation des échantillonneurs passifs à Gradient de Diffusion en couche mince (DGT) pour l’échantillonnage des eaux de transition et côtières à des fins de surveillance de la qualité de l’eau. La méthodologie définie dans ce guide a été développée par le consortium du projet Interreg MONITOOL de l’Union européenne afin d’assurer la comparabilité et la reproductibilité des données obtenues par chaque partenaire du projet dans les différentes régions. Le guide fournit des informations pratiques et détaillées sur tous les aspects à prendre en considération avant le déploiement de ces dispositifs et lors des étapes essentielles après leur déploiement, extraction et trai - tement ultérieur des échantillons pour l’analyse des métaux traces. Bien qu’il ne s’agisse pas d’un protocole standard, ces lignes directrices abordent la nécessité d’une approche commune et l’intention de promouvoir les meilleures pratiques

A new approach to using Diffusive Gradient in Thin-films (DGT) labile concentration for Water Framework Directive chemical status assessment: adaptation of Environmental Quality Standard to DGT for cadmium, nickel and lead

Integrative passive samplers, such as DGT (Diffusive Gradients in Thin-films), are identified in European Technical Guidance Documents as promising tools to improve the quality of the assessment, in the context of the WFD (EU Water Framework Directive). However, DGT results cannot yet be used directly in a regulatory framework to assess the chemical status of water bodies, as DGT labile concentrations cannot be directly compared to the metal AA-EQSmarine water (Annual Average Environmental Quality Standard) established by the WFD, which are defined in the dissolved concentration. Therefore, prior to using DGT results in a regulatory context, for cadmium, nickel and lead, an adaptation of existing AA-EQSmarine water for DGTs should be pursued, ensuring at least the same level of protection. In this sense, in the framework of the MONITOOL project, a robust database of dissolved and labile metal concentrations in transitional and coastal waters, for adapting the existing AA-EQSmarine water for DGT technique, was obtained. Building on these results, this study proposes a methodology and provides values and equations for using DGT results for the chemical status assessment of marine waters, by adapting the EQSmarine water to adapted EQSDGT or predicting dissolved concentrations from DGT results. Based on available dataset, a first simulation of “chemical status” assessment per MONITOOL sampling site using DGT measured labile concentrations was carried out and the results were compared to an assessment based on dissolved concentration to check their compliance. These results demonstrate that the use of DGT passive samplers is appropriate for the metal concentrations level encountered in the marine environment. Further work is recommended to test the effectiveness of the methodology proposed in this study under WFD conditions on more sites and to establish common strategy guidelines for the use of DGT passive samplers in monitoring

A Good Practice Guide for the Use of DGTs. Sampling of metals in transitional and coastal waters by Diffusive Gradient in Thin films (DGT) technique

This good practice guide is focused on the DGT devices, which are the most widely used passive sampler for metals, covering the following aspects:■ Principle■ Handling passive sampling devices for metals■ Estimation of appropriate field deployment time■ A Good Practice Guide for the Use of DGTs■ Passive sampling device preparation and assembly■ Selection of sampling site and safety precautions■ Passive sampling device deployment and retrieval■ Extraction of analytes from passive sampling devices■ Analysis■ Calculation

New tools for monitoring the chemical status in transitional and coastal waters under the Water Framework Directive

El presente volumen de la serie Perspectivas del Agua trata diversos aspectos sobre la investigación, la planificación de usos, la gestión y los valores socioculturales de los sistemas acuáticos en la época contemporánea. Las contribuciones incluidas analizan la relación entre el agua y las comunidades humanas en el mundo actual desde perspectivas científicas, políticas, sociales y culturales. El agua es un bien natural indispensable para cualquier actividad humana cuyo valor debe ser investigado, conocido y difundido (Consejo de Europa, 1968) reafirmando su función como recurso para el bienestar en el marco internacional de los derechos humanos (World Health Organization, 2003;.

Assessing variability in the ratio of metal concentrations measured by DGT-type passive samplers and spot sampling in European seawaters

The current study evaluates the effect of seawater physico-chemical characteristics on the relationship between the concentration of metals measured by Diffusive Gradients in Thin films (DGT) passive samplers (i.e., DGT-labile concentration) and the concentrations measured in discrete water samples. Accordingly, Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to measure the total dissolved metal concentrations in the discrete water samples and the labile metal concentrations obtained by DGT samplers; additionally, lead and cadmium conditional labile fractions were determined by Anodic Stripping Voltammetry (ASV) and total dissolved nickel was measured by Cathodic Stripping Voltammetry (CSV). It can be concluded that, in general, the median ratios of DGT/ICP and DGT/ASV(CSV) were lower than 1, except for Ni (median ratio close to 1) and Zn (higher than 1). This indicates the importance of speciation and time-integrated concentrations measured using passive sampling techniques, which is in line with the WFD suggestions for improving the chemical assessment of waterbodies. It is the variability in metal content in waters rather than environmental conditions to which the variability of the ratios can be attributed. The ratios were not significantly affected by the temperature, salinity, pH, oxygen, DOC or SPM, giving a great confidence for all the techniques used. Within a regulatory context such as the EU Water Framework Directive this is a great advantage, since the simplicity of not needing to use corrections to minimize the effects of environmental variables could help in implementing DGTs within monitoring networks