Pedogenic characterization of rare earth elements in humid subtropical soils on volcanic plateaus
Journal
CATENA
Journal Volume
244
Start Page
108256
ISSN
0341-8162
Date Issued
2024-09
Author(s)
Abstract
Volcanic plateaus commonly form in andesitic regions. Few pedological studies have explored the fractionation and mobility of rare earth elements (REEs) in andesite-derived soils. The present study clarified the pedogenic processes of soils on volcanic plateaus in northern Taiwan; this was achieved by analyzing the patterns and fractionation indices of REEs and performing mass balance calculations to determine their mobility. Four pedons were examined through physiochemical and mineral analyses and by taking REEs measurements from the plateaus surrounding Mt. Huangtsui. The four pedons were pedon VP1 from a lava plateau, pedons VP2 and VP3 from an epiclastic plateau, and pedon VP4 from the scarp of a lava plateau. The identified chondrites-normalized REEs patterns exhibited universal similarities with light REEs (LREEs) enrichment across all horizons of individual pedons, suggesting that their parent materials were uniform within the profile on the plateau. The signatures of REEs patterns differed among the four pedons because of their soil variations (e.g., clay and gibbsite). This study identified a considerable migration of REEs along with clay, Fe, and Al in the soil profiles. The mass gains of REEs, LREEs, and heavy REEs (HREEs) in the subsurface soils of pedon VP1 were greater than those in the other pedons because pedon VP1, classified as Typic Hapludult, exhibited the highest level of soil development. However, the REEs mass fluxes were low in pedon VP4 (classified as Typic Dystrudept) throughout the profile, where HREEs were preferentially leached in incipient soil. For pedons VP2 and VP3 (both classified as Oxic Dystrudepts), their profile distributions of REEs were similar because of their identical parent materials and pedological characteristics. A principal component analysis elucidated the differentiation of REEs distribution between pedons. Thus, the REEs characterization associated with the mass balance was applicable to the pedogenic tracers of soils on the plateaus. This study provides useful insights into the mobility of REEs in andesitic soils on volcanic plateaus and the potential of REEs as pedogenic tracers of these soil types globally.
SDGs
Publisher
Elsevier BV
Type
journal article