Spatial variability and sources of platinum in a contaminated harbor – tracing coastal urban inputs

Environmental context Emerging contaminants such as platinum are continuously released into aquatic environments. Analytical challenges, however, have restricted information on their geochemical cycles. We examine the potential use of platinum as a tracer of anthropogenic inputs in a model industrial/urban site (Genoa Harbor, Italy), and provide a first estimate of dissolved platinum baseline concentrations in the northern Mediterranean coast. Biogeochemical cycles that include processes to control platinum (Pt) distribution remain widely unknown in aquatic environments, especially in coastal systems. Dissolved Pt concentrations in coastal seawater (Pt-D) and in suspended particulate matter (SPM, Pt-P) were measured, together with master variables comprising dissolved oxygen, dissolved and particulate organic carbon, chlorophyll-a, turbidity, and ammonium levels, along two longitudinal profiles in the industrial Genoa Harbor (north-west Italy). Concentrations and spatial distribution of Pt-D and Pt-P levels reflect distinct concentration gradients that were attributed to different Pt sources such as hospital, domestic and industrial wastewater, atmospheric deposition, and/or road runoff. Concentrations reaching up to 0.18 ng L-1 Pt-D and 14 ng g(-1) Pt-P reflect the impact of Pt urban inputs to coastal sites. These first data highlight considerable anthropogenic contamination in a confined harbor compared with the proposed reference value for the western Mediterranean surface seawater measured at external sites. Identified correlations between Pt levels and human pollution signals suggest the potential use of Pt as a new tracer of anthropogenic inputs that can be applied to other urbanised coastal systems. Biogeochemical processes that induce changes in the partitioning and fate of Pt in coastal seawater reflect a spatial variability and highlight the need for comprehensive environmental monitoring at an appropriate spatial scale.