Soil metal pollution assessment in Sarcocornia salt marshes in a South American estuary

Highlights: • Metal pollution level in two South American Sarcocornia salt marshes was evaluated. • Pseudo-total and bioavailable metal levels and soil conditions were measured. • Percentage of bioavailability was higher than 60% for Zn, Cu and Pb. • Organic matter ruled the distribution of pseudo-total and bioavailable metals. • The enrichment factor and the Igeo and PLI indexes denoted null to moderate pollution. Soil metal pollution in two Sarcocornia salt marshes within the Bahía Blanca estuary (Argentina, South America) was evaluated through pseudo-total and bioavailable metal levels and pollution indexes. Soil conditions were also studied. The pseudo-total metal concentrations were similar in both salt marshes and followed the same decreasing order: Fe > Zn > Cu > Cr > Ni > Pb > Cd. Bioavailable metals presented different patterns between salt marshes. The percentages of the bioavailable fraction varied between 28 and 80%, being higher than 60% for Cu, Zn and Pb. Organic matter ruled the distribution of all metals, except Pb. Using shale average concentration as background level, indexes did not show pollution nor enrichment, whereas using as background levels local values, anthropogenic enrichment was found for all metals and most metals showed moderate metal pollution. Our results showed that bioavailable metals levels and indexes using local background values provide an adequate assessment of metal pollution in salt marsh soils.