Dissolved silver in European estuarine and coastal waters

Silver is one of the most toxic elements for the marine microbial and invertebrate community. However, little is known about the distribution and behaviour of dissolved silver in marine systems. This paper reports data on dissolved and sediment-associated silver in European estuaries and coastal waters which have been impacted to different extents by past and present anthropogenic inputs. This is the first extended dataset for dissolved silver in European marine waters. Lowest dissolved silver concentrations were observed in the Gullmar Fjord, Sweden (8.9 ± 2.9 pM; x ± 1σ), the Tamar Estuary, UK (9.7 ± 6.2 pM), the Fal Estuary, UK (20.6 ± 8.3 pM), and the Adriatic Sea (21.2 ± 6.8 pM). Enhanced silver concentrations were observed in Atlantic coastal waters receiving untreated sewage effluent from the city of A Corũna, Spain (243 ± 195 pM), and in the mine-impacted Restronguet Creek, UK (91 ± 71 pM). Anthropogenic wastewater inputs were a source of dissolved silver in the regions studied, with the exception of the Gullmar Fjord. Remobilisation of dissolved silver from historically contaminated sediments, resulting from acid mine drainage or sewage inputs, provided an additional source of dissolved silver to the estuaries. The ranges in the log particle-water partition coefficient (Kd) values of 5–6 were similar for the Tamar and Mero estuaries and agreed with reported values for other estuaries. These high Kd values indicate the particle reactive nature of silver with oxic sediments. In contrast, low Kd values (1.4–2.7) were observed in the Fal system, which may have been due to enhanced benthic inputs of dissolved silver coupled to limited scavenging of silver on to sediments rich in Fe oxide.