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Farmer, John G.; Graham, Margaret C.; Eades, Lorna J.; Lilly, Allan; Bacon, Jeffrey R., E-mail: J.G.Farmer@ed.ac.uk2016
AbstractAbstract
[en] Some 644 individual soil horizons from 169 sites in Scotland were analyzed for Pb concentration and isotopic composition. There were three scenarios: (i) 36 sites where both top and bottom (i.e. lowest sampled) soil horizons were classified as organic in nature, (ii) 67 with an organic top but mineral bottom soil horizon, and (iii) 66 where both top and bottom soil horizons were mineral. Lead concentrations were greater in the top horizon relative to the bottom horizon in all but a few cases. The top horizon "2"0"6Pb/"2"0"7Pb ratio was lesser (outside analytical error) than the corresponding bottom horizon "2"0"6Pb/"2"0"7Pb ratio at (i) 64%, (ii) 94% and (iii) 73% of sites, and greater at only (i) 8%, (ii) 3% and (iii) 8% of sites. A plot of "2"0"8Pb/"2"0"7Pb vs. "2"0"8Pb/"2"0"6Pb ratios showed that the Pb in organic top (i, ii) and bottom (i) horizons was consistent with atmospherically deposited Pb of anthropogenic origin. The "2"0"6Pb/"2"0"7Pb ratio of the organic top horizon in (ii) was unrelated to the "2"0"6Pb/"2"0"7Pb ratio of the mineral bottom horizon as demonstrated by the geographical variation in the negative shift in the ratio, a result of differences in the mineral horizon values arising from the greater influence of radiogenic Pb in the north. In (iii), the lesser values of the "2"0"6Pb/"2"0"7Pb ratio for the mineral top horizon relative to the mineral bottom horizon were consistent with the presence of anthropogenic Pb, in addition to indigenous Pb, in the former. Mean anthropogenic Pb inventories of 1.5 and 4.5 g m"−"2 were obtained for the northern and southern halves of Scotland, respectively, consistent with long-range atmospheric transport of anthropogenic Pb (mean "2"0"6Pb/"2"0"7Pb ratio ~ 1.16). For cultivated agricultural soils (Ap), this corresponded to about half of the total Pb inventory in the top 30 cm of the soil column. - Highlights: • Pb isotope ratios were determined for 644 soil horizons from 169 sites across Scotland • Pb in organic soil horizons was essentially atmospherically deposited anthropogenic Pb • Pb in mineral top soil horizons was a mixture of anthropogenic and indigenous soil Pb • ~ 50% Pb in cultivated agricultural soils (Ap) to a depth of ~ 30 cm was anthropogenic • The anthropogenic Pb soil inventory was ~ 3 times greater in the south than the north
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S0048-9697(15)31110-4; Available from http://dx.doi.org/10.1016/j.scitotenv.2015.11.127; Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
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