Soil degradation due to the destruction of crystalline kaolinite and the formation of X-ray amorphous clays accompanying ephemerial saline groundwater discharge

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dc.contributor.authorTaylor, GRen_AU
dc.contributor.authorDay, Men_AU
dc.contributor.authorMeredith, KTen_AU
dc.date.accessioned2012-04-23T03:50:39Zen_AU
dc.date.available2012-04-23T03:50:39Zen_AU
dc.date.issued2012en_AU
dc.date.statistics2012-04-23en_AU
dc.description.abstractThe discharge of saline groundwater results in the formation of sodic soil scalds in irrigated, dryland and urban environments of southeastern Australia. Sodic soils are dispersive, and this leads to soil erosion and a loss in agricultural productive capacity. These sodic soils commonly show polygonal cracking and pressure ridges indicating the presence of swelling clays. Infrared spectroscopy of scald surfaces and XRD (X-ray diffraction) analyses of the clay fractions of the sodic soils show the presence of amorphous clays, smectite, illite or mixed smectite/illite layer clays. Non-salinised soils adjacent to the salt scalds are commonly predominantly kaolinitic. SEM images and normative EDS mineral analyses of the clay fractions of these soils show that crystalline particles, predominantly of kaolinite, are progressively replaced by poorly crystalline smectite, illite and amorphous material. Normative mineral analyses determined from the bulk soil composition, based on a derived composition of submicron clay particles, show that increased soil salinity correlates with a higher percentage of X-ray amorphous clays of a smectitic composition. By comparison with studies from elsewhere, we propose a mechanism by which kaolinite is transformed into smectite and illite or mixed layer smectite/illite, which proceeds by dissolution and subsequent crystallisation, rather than by solid-state transformation. We propose that the crypto-crystalline or amorphous nature of the clays produced is largely a function of cycles of varying mineral stability produced by alternating periods of saline water discharge and freshwater flushing. The transformation of primary kaolinite to smectite/illite within saline discharge zones explains the spectral changes that allow such saline discharge areas to be mapped with hyperspectral imagery. © 2012, Taylor & Francis Ltd.en_AU
dc.identifier.citationTaylor, G. R., Day, M., Meredith, K. (2012). Soil degradation due to the destruction of crystalline kaolinite and the formation of X-ray amorphous clays accompanying ephemeral saline groundwater discharge. Australian Journal of Earth Sciences, 59(1), 135-152. doi:10.1080/08120099.2012.621980en_AU
dc.identifier.govdoc4104en_AU
dc.identifier.issn0812-0099en_AU
dc.identifier.issue1en_AU
dc.identifier.journaltitleAustralian Journal of Earth Sciencesen_AU
dc.identifier.pagination135-152en_AU
dc.identifier.urihttp://dx.doi.org/10.1080/08120099.2012.621980en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/4181en_AU
dc.identifier.volume59en_AU
dc.language.isoenen_AU
dc.publisherTaylor & Francisen_AU
dc.subjectSoilsen_AU
dc.subjectGround wateren_AU
dc.subjectKaoliniteen_AU
dc.subjectClaysen_AU
dc.subjectX-ray diffractionen_AU
dc.subjectSalinityen_AU
dc.titleSoil degradation due to the destruction of crystalline kaolinite and the formation of X-ray amorphous clays accompanying ephemerial saline groundwater dischargeen_AU
dc.typeJournal Articleen_AU
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