Behavior of platinum during estuarine mixing (Pontevedra Ria, NW Iberian Peninsula)

Abstract

The concentrations of Pt in sediments, water and suspended particulate matter (SPM) were determined in the Lérez river estuary (Pontevedra Ria, NW Iberian Peninsula) on two sampling dates in 2008 and 2011, by means of catalytic adsorptive stripping voltammetry. Average concentrations in sediments (1.2 ± 0.5 ng g -1 ; n=13) corresponded to an enrichment factor of 2-4 compared to background values, and were in the range of those found in the SPM during the 2011 sampling (2.1 ± 2.4 ng g -1 ; n=15), but significantly lower than in 2008 SPM (8.0 ± 4.4 ng g -1 ; n=15). Higher dissolved Pt concentrations were also found in 2008 (0.21 and 0.62 pM in the freshwater and seawater end-member) compared to the 2011 campaign (0.03 -freshwater -and 0.40 pM -seawater endmember). Concentrations in the seawater end-members exceed those of typical North Atlantic waters, suggesting inputs of this element within the estuary. The extremely low value for the freshwater end-member in 2011 appears to be among the lowest Pt concentrations ever reported in the literature. Non-conservative behaviour of Pt during estuarine mixing was observed on both sampling dates. Particle-water distribution coefficients (KD) show a decrease with salinity, in agreement with speciation calculations, which predict a transfer from neutral Pt(II) (as Pt(OH)2) in freshwater to negatively charged Pt(IV) (as PtCl5(OH) 2-) species in seawater. Such behaviour during estuarine mixing can play an important role in Pt mobilization from contaminated particles discharged into estuaries and coasts.

Precise determination of dissolved platinum in seawater of the Japan Sea, Sea of Okhotsk and western North Pacific Ocean

“…Cd and Ag strongly interact with marine biota (Martin and Knauer, 1973;Fisher and Wente, 1993;Ratte, 1998;Lane and Morel, 2000;Ho et al, 2003), which induces low concentrations of both elements in surface waters. Conversely, Pt exists as PtCl 4 2− and PtCl 5 OH 2− in seawater (Cosden and Byrne, 2003;Cobelo-García et al, 2013) as previously described, but there is little research concerning the relationship between Pt and organisms (Ravindra et al, 2004;Mulholland and Turner, 2011;Shams et al, 2014). The conservativetype vertical profile implies that there are relatively few interactions between Pt and biota.…”

“…Recently, Cobelo-García et al (2013) calculated Pt speciation in natural waters using thermodynamic data, and concluded that Pt 4 + (PtCl 5 OH 2 − ) predominates over Pt 2+ (PtCl 4 2 − ) in typical seawater (7.5-8.4). Therefore, it is important to compare the distributions of Pt, Ag, and Cd in seawater in different oceanic basins to understand the geochemical cycle of these elements in aquatic environments.…”

“…The conservativetype vertical profile implies that there are relatively few interactions between Pt and biota. The negatively charged anions, PtCl 4 2 − and PtCl 5 OH 2 − (Cosden and Byrne, 2003;Cobelo-García et al, 2013), might also have a relatively low particle affinity in seawater. However, the kinetics of the interaction between each chemical species of Pt and particles in seawater are not well known.…”

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

“…Platinum concentration in seawater is difficult to quantify precisely, in particular in less contaminated sites, because of the extremely low environmental levels (sub nanograms per litre; Mashio et al 2017). Existing studies on marine coastal areas, which include saline estuaries, report dissolved Pt concentrations ranging from 0.05 to 0.30 ng L À1 (Cobelo-García et al 2013, 2014aGoldberg et al 1986;Mashio et al 2016Mashio et al , 2017Obata et al 2006;Turetta et al 2003;van den Berg and Jacinto 1988). A small number of studies report Pt concentrations in suspended particulate matter (SPM) ranging from ,2 to 10 ng g À1 in the L erez Estuary and from ,0.2 to 1 ng g À1 in the Gironde Estuary (Cobelo-García et al 2013, 2014a.…”

“…Existing studies on marine coastal areas, which include saline estuaries, report dissolved Pt concentrations ranging from 0.05 to 0.30 ng L À1 (Cobelo-García et al 2013, 2014aGoldberg et al 1986;Mashio et al 2016Mashio et al , 2017Obata et al 2006;Turetta et al 2003;van den Berg and Jacinto 1988). A small number of studies report Pt concentrations in suspended particulate matter (SPM) ranging from ,2 to 10 ng g À1 in the L erez Estuary and from ,0.2 to 1 ng g À1 in the Gironde Estuary (Cobelo-García et al 2013, 2014a. Variations in Pt concentrations and possible Pt enrichment at those coastal sites have been attributed to Pt inputs from human activities, especially in systems receiving anthropogenically impacted freshwater inputs, as observed in the Tokyo Bay (e.g.…”