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Fate of 210 Pb ex fallout in soil under forest and scrub of the central Spanish Pre‐Pyrenees
Author(s) -
Gaspar L.,
Webster R.,
Navas A.
Publication year - 2017
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/ejss.12427
Subject(s) - radionuclide , environmental science , soil water , soil science , total organic carbon , hydrology (agriculture) , soil horizon , soil carbon , geology , environmental chemistry , mineralogy , chemistry , physics , geotechnical engineering , quantum mechanics
Summary The characteristics and distribution of unsupported radioactive lead‐210 ( 210 Pb ex ) in soil and the relations between the radionuclide and soil properties determine its fate within the environment. We have explored the distribution of 210 Pb ex in stony soil profiles near the edge of the Ebro basin in northern Spain, the role played by vegetation in that distribution, and the relation between the radionuclide and organic carbon. We describe in detail the profiles of 210 Pb ex at 23 sites, 10 under forest and 13 under scrub, which were sampled at 2‐cm intervals to a maximum depth of 14 cm. The theoretical distribution of 210 Pb ex follows an exponential decline with depth in undisturbed soil, assuming minimal surface slope and no evidence of erosion or deposition processes. Comparable distribution patterns of 210 Pb ex and organic C became evident from the analyses. There were significant correlations between the activity of 210 Pb ex and organic C under both forest and scrub, but the strongest were in the surface layers of soil under forest. More than 80% of the total activity of 210 Pb ex was adsorbed in the upper 6 cm, with an exponential decline with increasing depth. The decline was modelled with exponential functions fitted by non‐linear least‐squares regression to predict the depth distributions of 210 Pb ex and organic C in forest and scrub soils separately. The results confirm the viability of the use of 210 Pb ex in stony soil as an indicator of soil redistribution and show the significant effect of vegetative cover. These results provide useful information about sampling design for future research if the radionuclide 210 Pb ex is used for assessing soil redistribution in similar Mediterranean environments. Highlights Characterizing the vertical distribution of 210 Pb ex requires high resolution sampling (2 cm). In uncultivated soil of the Pre‐Pyrenees the fallout, 210 Pb ex , is retained in the uppermost 14 cm. The distribution of 210 Pb ex matches that of the organic matter down the profile. Vegetation affects the surface activity of 210 Pb ex in the soil, being greater under forest than under scrub.