@inproceedings{fdi:010012917,
  title = {{D}issolution kinetics of silicon and aluminium in a mollic fragiudalf of central {I}taly, derived from a volcanoclastic sediment},
  author = {{L}orenzoni, {P}. and {Q}uantin, {P}aul and {S}padoni, {M}.},
  editor = {},
  language = {{ENG}},
  abstract = {{I}n the sedimentary basin of {R}ieti ({C}entral {I}taly) a {M}ollic {F}ragiudalf was studied in order to verify, through the analysis of differential dissolution kinetics of {S}i and {A}l, wether the presence of this two elements could be involved in determining the fragic characters of its deep horizons. {T}he reuslts of the main physico-chemical analysis confirmed the fragic features of the deep horizons {B}t3x and {C}tgx which have been already observed in the field study. {D}ifferential dissolution of {S}i and {A}l was performed using 0,5 {N} {N}a{OH} at 25°{C}, and the values of silica and alumina obtained after each of ten consecutive extractions were cumulated to trace the cumulative curves of dissolution. {S}lope changes of the curves, which indicate changes in dissolution rate, allowed os to recognize three mineralogical phases with different degree of solubility. {T}he total quantity of {S}i{O}2 and {A}l2{O}3 dissolved in all the extractions and relative to each of these three phases was estimated, by a graphic method, together with {S}i{O}2({A}l2{O}3 molar ratio. {T}his one was indicative of the mineralogical composition and behaviour of each horizon. {T}his study showed an accumulation of free silica which could be present in the form of phytoliths or diatoms as well as a fine precipitate of opal-{A} and silica-gel in the whole soil, mainly in teh {A}p and {C}tgx horizons. {M}oreover neogenesis of clay was more evident in {B}t3x horizon. {T}he volcanic origin of the parent material, a trachytic ash fall, probably deposited in a lacustrine environment, could have favoured the availability of {S}i and the authigenic formation of halloysitic clay from the weathering of galss and feldspars. {O}ur study therefore corroborates the findings of previous studies by {C}hadwick et al. (1987) and {K}arathanasis (1989) indicating the important role played by silica, probably as bonding agent, in contributing to produce characteristics of a fragipan. ({R}{\'e}sum{\'e} d'auteur).},
  keywords = {{CENDRE} {VOLCANIQUE} ; {HORIZON} ; {ALUMINIUM} ; {SILICE} ; {MINERALOGIE} ; {PYROCLASTITE} ; {FRAGIPAN} ; {ITALIE}},
  numero = {},
  pages = {121--127},
  booktitle = {{S}uelos volcanicos endurecidos},
  year = {1997},
  URL = {https://www.documentation.ird.fr/hor/fdi:010012917},
}