Soil mapping at the local- (paddock), to continental-scale, may be improved through remote hyperspectral imaging of surface mineralogy. This opportunity is demonstrated for the semiarid Tick Hill test site (20 km2) near Mount Isa in western Queensland. The study of this test site is part of a larger Queensland government initiative involving the public delivery of 25,000 km2 of processed airborne hyperspectral mineral maps at 4.5 m pixel resolution to the mineral exploration industry. Some of the mineral maps derived from hyperspectral imagery for the Tick Hill area include the abundances and/or physicochemistries (chemical composition and crystal disorder) of dioctahedral clays (kaolin, illite-muscovite and Al smectite, both montmorillonite and beidellite), ferric/ferrous minerals (hematite/goethite, Fe2+-bearing silicates/carbonates) and hydrated silica (opal) as well as soil water (bound and unbound) and green and dry (cellulose/lignin) vegetation. Validation of these hyperspectral mineral products is based on field soil sampling and laboratory analyses (spectral reflectance, X-ray diffraction, scanning electron microscope and electron backscatter). The mineral maps show more detailed information regarding the surface composition compared with the published soil and geology (1:100,000 scale) maps and airborne radiometric imagery (collected at 200 m line spacing). This mineral information can be used to improve the published soil mapping but also has the potential to provide quantitative information suitable for soil and water catchment modeling and monitoring.

We describe the information content of soil visible-near infrared (vis-NIR) reflectance spectra and map their spatial distribution across Australia. The spectra of 4030 surface soil sample from across the country were measured using a vis-NIR spectrometer with a wavelength range between 350-2500 nm. The spectra were treated using a principal component analysis (PCA) and the resulting scores were mapped by ordinary point kriging. The largely dominant and common feature in the maps was the difference between the more expansive, older and more weathered landscapes in the centre and west of Australia and the generally younger, more complex landscapes in the east. A surface soil class map derived from the clustering of the principal components was similar to an existing soil classification map. We show that vis-NIR reflectance spectra: (i) provide an integrative measure to rapidly and efficiently measure the constituents of the soil, (ii) can replace the use of traditional soil properties to describe the soil and make geomorphological interpretations of its spatial distribution and (iii) can be used to classify soil objectively.

The use of airborne hyperspectral imagery for mapping soil surface mineralogy is examined for the semi-arid Tick Hill test site (20 km2) near Mount Isa in north-western Queensland. Mineral maps at 4.5 m pixel resolution include the abundances and physicochemistries (chemical composition and crystal disorder) of kaolin, illite-muscovite, and Al smectite (both montmorillonite and beidellite), as well as iron oxide, hydrated silica (opal), and soil/rock water (bound and unbound). Validation of these hyperspectral mineral maps involved field sampling (34 sites) and laboratory analyses (spectral reflectance and X-ray diffraction). The field spectral data were processed for their mineral information content the same way as the airborne HyMap data processing. The results showed significant spatial and statistical correlation. The mineral maps provide more detailed surface compositional information compared with the published soil and geology maps and other geoscience data (airborne radiometrics and digital elevation model). However, there is no apparent correlation between the published soil types (i.e. Ferrosols, Vertosols, and Tenosols) and the hyperspectral mineral maps (e.g. iron oxide-rich areas are not mapped as Ferrosols and smectite-rich areas are not mapped as Vertosols). This lack of correlation is interpreted to be related to the current lack of spatially comprehensive mineralogy for existing regional soil mapping. If correct, then this new, quantitative mineral mapping data has the potential to improve not just soil mapping but also soil and water catchment monitoring and modeling at local to regional scales. The challenges to achieving this outcome include gaining access to continental-scale hyperspectral data and models that link the surface mineralogy to subsurface soil characteristics/processes.

Recently, continental-scale geochemical surveys of Europe and Australia were completed. Thanks to having exchanged internal project standards prior to analysing the samples, we can demonstrate direct comparability between these datasets for 10 major oxides (Al2O3, CaO, Fe2O3, K2O, MgO, MnO, Na2O, P2O5, SiO2 and TiO2), 16 total trace elements (As, Ba, Ce, Co, Cr, Ga, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn and Zr), 14 aqua regia extracted elements (Ag, As, Bi, Cd, Ce, Co, Cs, Cu, Fe, La, Li, Mn, Mo and Pb), Loss On Ignition (LOI) and pH. By comparing these new datasets to one another, we can learn lessons about continental-scale controls on soil geochemistry and about critical requirements for global geochemical mapping. Although the median soil compositions of both continents are overall quite similar, the Australian median values are systematically lower, except for SiO2 and Zr. This reflects the generally longer and, locally more intense weathering in Australia (median Chemical Index of Alteration values are 72 and 60% for Australia and Europe, respectively). We found that element concentrations typically span 3 (and up to 5) orders of magnitude on each continent. The comparison of 2 continental geochemical surveys shows that the most critical requirement for global geochemical mapping is good analytical quality. Only where a comprehensive quality control program, including field and laboratory duplicates, internal project standards and Certified Reference Materials, is implemented and documented, are the results credible and comparable with other datasets.

Global-scale mapping of surface mineralogy is now becoming possible using remote hyperspectral sensing technologies. Global-scale mineral maps have now been generated for Mars using thermal infrared hyperspectral data collected from the Mars-orbiting Thermal Emission Spectrometer (TES- http://jmars.asu.edu/data/), including maps of feldspar, pyroxene, olivine and quartz contents. Other mineral maps of Mars are now being assembled using the recently launched Compact Reconnaissance Imaging Spectrometer (CRISM - http://crism.jhuapl.edu/), including sulphates, kaolinite, illite/muscovite, chlorites, carbonate and water (www.lpi.usra.edu/meetings/7thmars2007/pdf/3270.pdf). In contrast, even though mapping the mineralogy of the Earth's land surface can improve understanding and management of Earth's resources, including: - monitoring of soils (acid sulphate soils, salinity, soils loss and soil carbon); - better characterisation of regolith materials (e.g. transported versus in situ); - discovery of new mineral deposits using alteration vectors; and - more accurate environmental assessments during resource exploitation (baseline mapping, monitoring and closure)

Iron (Fe) oxide mineralogy in most Australian soils is poorly characterised, even though Fe oxides play an important role in soil function. Fe oxides reflect the conditions of pH, redox potential (Eh), moisture and temperature in the soil environment. The Fe oxide mineralogy exerts a strong control on soil colour. Visible-near infrared (vis-NIR) spectroscopy can be used to identify and measure the abundance of certain Fe oxides in soil as well as soil colour. The aims of this paper are to: (i) measure the hematite and goethite content of Australian soils from their vis-NIR spectra, (ii) compare these results to measurements of soil colour, and (iii) describe the spatial variability of hematite, goethite and soil colour, and map their distribution across Australia. The spectra of 4606 surface soil sample from across Australia were measured using a vis-NIR spectrometer with a wavelength range between 350-2500 nm. We determined the Fe oxide content from characteristic absorptions of hematite (near 880 nm) and goethite (near 920 nm) and derived a normalised iron oxide difference index (NIODI) to better discriminate between them. The NIODI was generalised across Australia with its spatial uncertainty using sequential indicator simulation. We also derived soil RGB colour from the spectra and mapped its distribution and uncertainty across the country using sequential Gaussian simulations. The simulated RGB colour values were made into a composite true colour image and were also converted to Munsell hue, value and chroma. These colour maps were compared to the map of the NIODI and both were used for interpretation of our results. The work presented here was evaluated using existing studies on the distribution of Fe oxides in Australian soils.

Geoscience Australia and the CO2CRC have constructed a greenhouse gas controlled release facility at an experimental agricultural station maintained by CSIRO Plant Industry at Ginninderra, Canberra. The facility is designed to simulate surface emissions of CO2 (and other greenhouse gases) from the soil into the atmosphere. CO2 is injected into the soil is via a 120m long slotted HDPE pipe installed horizontally 2m underground. This is fitted with a straddle packer system to partition the well into six CO2 injection chambers with each chamber connected to its own CO2 injection line. CO2 was injected into 5 of the chambers during the first sub-surface release experiment (March - May 2012) and the total daily injection rate was 100 kg/d. A krypton tracer was injected into one of the 5 chambers at a rate of 10 mL/min. Monitoring methods trialled at the site include eddy covariance, atmospheric tomography using a wireless networked array of solar powered CO2 stations, soil flux, soil gas, frequency-domain electromagnetics (FDEM), soil community DNA analysis, and krypton tracer studies (soil gas and air). A summary of the findings will be presented. Paper presented at the 2012 CO2CRC Research Symposium, Sunshine Beach, 27-29 November 2012.

Introduction Low-density geochemical surveys provide a cost-effective means to assess the composition of near-surface materials over large areas. Many countries in the world have already compiled geochemical atlases based on such data. These have been used for a number of applications, including: - establish baselines from which future changes can be measured - design geologically sensible targets for remediation of contaminated sites - support decision-making regarding appropriate land-use - explore for natural resources - study links between geology and plant/animal health (geohealth) A first pilot project was initiated to help establish sampling and analytical protocols relevant to Australian landscapes and climates. The Riverina region was chosen for this study because of its crucial economic, environmental and societal importance within the Murray-Darling basin. The region is a prime agricultural area, is bordered to the south by the Victorian goldfields, and is home to 11% of the Australian population. Results of this study are presented here. Methods Using a hydrological analysis, 142 sites near the outlets of large catchments were selected within the 123,000 km2 survey area (1 site per 866 km2 on average). At each site, two 10-cm thick overbank sediment samples were taken, one at the surface ('top overbank sediment', TOS) and the other between 60 and 90 cm depth (`bottom overbank sediment', BOS). These were described, dried, sieved (<180 m) and analysed chemically for 62 elements. Exploratory data analysis was undertaken and geochemical maps (various styles are shown here) were prepared. Results and discussion The geology of the area is dominated by Cainozoic sediments found in low-relief plains over the vast majority of the Riverina. The eastern and southern fringes of the area form higher relief landforms developed on outcropping or subcropping Palaeozoic sedimentary, mafic and felsic volcanic and felsic intrusive rocks. The geochemical results of the survey are independently corroborated by the good match between the distributions of K, U and Th concentrations in TOS and airborne gamma-ray maps. The distribution of Ca in BOS indicates generally higher concentrations in the northern part of the study area, which is also reflected in higher soil pH values there. Such data have implications for soil fertility and management in agricultural areas. In terms of applications to mineral exploration, dispersion trains of typical pathfinder elements for gold mineralisation, like As and Sb are clearly documented by the smoothly decreasing concentrations from south (near the Victorian goldfields) to north (over sediments from the Murray basin). Chromium is an element that can be associated with ill-health in animals and humans when present over certain levels. There is a smooth increase in Cr concentration from north to south, and the two sites with the highest values can be correlated with a ridge of Cambrian mafic volcanics. High total Cr concentrations in the Riverina are unlikely, however, to lead to serious health problems as only a very small proportion of Cr will be bioavailable. Conversely, some elements can be present at concentrations that are too low for optimum plant growth, such as potentially Mo. The distribution map for this element shows a general decrease from south to north. Given its lower bioavailability in acid soils, Mo is likely to be deficient in the south of the region, despite higher total concentrations here. Farmers report the necessity to use Mo-enriched fertilisers in this area. Conclusions Low-density geochemical surveys can be conducted in Australia using common regolith sampling media. They provide a cost-effective, internally consistent dataset that can be used by to support a variety of critical economic, environmental and societal decisions.

Spectral data from airborne and ground surveys enable mapping of the mineralogy and chemistry of soils in a semi-arid terrain of Northwest Queensland. The study site is a region of low relief, 20 km southeast of Duchess near Mount Isa. The airborne hyperspectral survey identified more than twenty surface components including vegetation, ferric oxide, ferrous iron, MgOH, and white mica. Field samples were analysed by spectrometer and X-ray diffraction to test surface units defined from the airborne data. The derived surface materials map is relevant to soil mapping and mineral exploration, and also provides insights into regolith development, sediment sources, and transport pathways, all key elements of landscape evolution.

The ability of thermal and shortwave infrared spectroscopy to characterise composition and textural was evaluated using both particle size separated soil samples and raw soils. Particle size analysis and separation into clay, silt and sand sized soil fractions was undertaken to examine possible relationships between quartz and clay mineral spectral signatures, and soil texture. Spectral indices, based on thermal infrared specular and volume scattering features, were found to discriminate clay mineral-rich soil from mostly coarser quartz-rich sandy soil, and to a lesser extent, from the silty quartz-rich soil. Further investigations were undertaken using spectra and information on 51 USDA and other soils within the ASTER Spectral Library to test the application of shortwave, mid- and thermal infrared spectral indices for the derivation of clay mineral, quartz and organic carbon content. A non linear correlation between quartz content and a TIR spectral index based on the 8.62 im was observed. Preliminary efforts at deriving a spectral index for the soil organic carbon content, based on 3.4 - 3.5 im fundamental H-C stretching vibration bands were also undertaken with limited results.