Data from: River banks and channels as hotspots of soil pollution after large-scale remediation of a river basin

Riparian areas are highly dynamic systems where the control of soil
pollution might be particularly challenging. Limited accessibility to
river banks and bed sediments makes reclamation operations particularly
difficult in these topographical positions, in comparison to floodplains.
This usually leads to the large-scale spread of pollutants following
pollution episodes in riparian areas. Here, we aimed to evaluate the
persistence of trace-element pollution in the soils of Guadiamar River
Valley (SW Spain), a large-scale remediation after a mine-spill. We
monitored topsoil along the river basin, and in different topographical
positions across the river section (river channel, river banks and
floodplain), 16 years after a pollution episode and subsequent remediation
program. River channels and banks were identified as hotspots of soil
pollution, where soluble concentrations of As, Cd and Zn were
significantly higher than in floodplains. Along the basin, soil pH and
carbonate content was highly variable as a result of contrasted geological
background, differential loads of sulfide deposition after the accident
and irregular effectiveness of the applied amendments. Cadmium and Zn
showed the highest levels of long-term re-distribution from the pollution
source. The results suggests that the stabilization and remediation of
soil pollution in river banks and channels, often overlooked when
achieving remediation works, should be a priority for land managers.