High Frequency Measurement of Metals: Steps Towards the Acceptance of Passive Samplers for Regulatory Monitoring

Abstract

Diffusive Gradient in Thin Films (DGT), and passive samplers (PS), in general, are already widely used in investigative monitoring and there is an increasing interest in their use for the environmental assessment of water bodies, within European policies requirements. The present work aimed to investigate the relationship between dissolved metal concentrations from spot sampling with DGT-labile metal concentrations and evaluate the reliability of the techniques for the measurement of metal concentrations in estuaries. Hence, in November, five samplings were carried out in the Oiartzun estuary (Basque Country, Bay of Biscay), an areawith high presence of industrial and port activities. DGTs (triplicates) were deployed and retrieved after 12 h. During that period, hourly spot water samples were taken, at the same depth than DGTs. Water samples were filtered for the posterior analysis of metals, dissolved organic carbon and the quantification of suspended particulate matter (SPM). Six trace metals (Co, Ni, Cu, Zn, Cd, Pb) were analysed in the 2 defined fractions (dissolved and DGT fraction) by ICP-MS. Hydrographic variables were measured at each sampling time. The relationships between dissolved and labile metal concentrations and the environmental factors influencing such correlations were studied. Our preliminary results show that for all the sampling period (12 h), except for Zn, there is no relationship between dissolved metal concentrations from spot sampling with labile metal concentration from DGT.