Impact of wildfire on interdune ecology and sediments: An example from the Simpson Desert, Australia

The stability of many sand dunes and their interdunes is dependent on vegetation and surface crust cover. When this cover is removed, the sand can be activated and fine sediments deflated making the dunefields into sources of dust. This paper reports the impact of devegetation by wildfire on an interdune in the Simpson Desert, Australia. The fire occurred in 2001 and six years after the event pronounced differences between a pair of burnt and unburnt sites was clearly discernible. The variables examined included vegetation assemblage, cyanobacteria abundance and sediment aggregation, particle-size distribution and colour; but whether they apply to all such situations is uncertain. Rate of recovery has been slow and the differences are likely to have been sustained by a combination of negative feedback processes and climate

A source-based model for describing dust concentrations during wind erosion events: an initial study

Wind erosion is a broad-scale process in inland Australia. When conditions are conducive to wind erosion, dust storms can entrain fine sediment over large areas of the continent, however closer examination indicates that the dust source areas are often spatially discrete. The fine sediment entrained from these sources, is transported as dust plumes, which may coalesce at some point downwind. While some progress has been made in estimating the dust load in these plumes (Knight, McTainsh & Simpson 1995), the accuracy of these estimates is limited by the size and shape of the source region assumed. In addition, soil loss per unit area is a more appropriate measure of soil erosion than total plume load, but estimating loss per unit area requires accurate estimation of source areas. The new model developed hopes to overcome these limitations by working from the source area downwind, rather than back-tracking to estimate the source area as done by Knight et al. (1995). As a result of this, the new model is quite distinct from that of Knight et al. (1995), in that it no longer assumes that entrainment is uniform across a single source area, and consequently that the concentration profile is uniform across the source area. The new model uses a Gaussian plume model (Zannetti 1990), with the dispersion parameters based on the Hanna, Briggs & Hosker (1982) estimates for rural areas. As a first approximation, the model describes dust loads emanating from sources of different strength and spacing along a crosswind line. This configuration is indicative of spatially discrete sources, with different soil erodibility and cover protection, producing different source strengths. Initial results from the model indicate that the nature of the downwind dust concentration profile is dependent on the following factors: downwind distance from source, source strengths,and crosswind source separation. A detailed discussion of the relationship between the above factors is presented. As a result of this discussion a number of conjectures are made about the nature of the physical system

Linked fluvial and aeolian processes fertilize Australian bioregions

The pattern of 137Cs-derived net (1950s–1990) soil redistribution over Australia, together with back-trajectory modeling of major dust storms, shows extensive areas of contemporary aeolian deposition. While the Cobar Peneplain and Gawler bioregions are the largest, the Wet Tropics is also a locus of deposition, consistent with the theory that dust is a source of nutrients for tropical rainforests growing on ancient weathered soils. Here we describe a new dust transport pathway over northeastern Australia and substantiate the link between fluvial and aeolian processes, and biogeochemical cycling between Australia’s arid interior and its coastal forest

Aeolian dust as a transport hazard

The effects of blowing dust on transport operations are often mentioned as one of the significant impacts of aeolian processes on human welfare. However, few studies have been presented to demonstrate this impact. This research examined official air traffic incident reports in Australia for inclusively 1969-2010 to characterise the hazard of blowing dust to aviation in the country, the first such study of its kind. For the 42 year record, 61 incidents were identified (mean 1.4 per annum), with the large majority occurring in the first half of the 1970s. Only 20% of incidents occurred from 1984 onwards. Australian dust activity has not decreased over time, and the reduction in incidents is partly explained by improvements in aviation technology. The centralisation of Air Traffic Control operations to major coastal cities may however have reduced pilot reporting of dust-induced aviation incidents. By type of dust activity, dust storms were associated with nearly half of the reported incidents and dust hazes produced around a quarter. Only 5% of incidents resulted in any physical damage to aircraft and only one case involving personal injury was reported. The majority of the adverse effects on aviation due to dust (nearly 60% of reported incidents) were related to difficulties for navigation and completion of scheduled journey. Since aircraft damage and bodily harm were rare, the impact of dust in Australia is mostly that of inconvenience and associated raised economic costs. From 1990, the temporal pattern of incidents does not show any significant increase despite several intensely dusty years associated with recent droughts. This suggests that Australian aviation safety may be relatively resistant to the adverse effects of atmospheric dust as a hazard

Aeolian abrasion and modes of fine particle production from natural red dune sands: an experimental study

A series of experiments was conducted to determine the potential for aeolian abrasion of natural dune sands to produce fine particles (< 125 µm) by (1) the release of resident fines; (2) spalling, chipping and breakage of particles; and (3) the removal of grain surface coatings. Parent samples were obtained from the surfaces of four active continental dunes and abraded using a glass 'test tube' chamber for up to 120h. The fine particles produced by this abrasion process were trapped at varying time intervals and subject to detailed particle-size analyses using a Coulter Multisizer. The abrasion of untreated parent samples produced fine particles in one of two main size classes, 50 µm, but when the parent sample was sieved to exclude particles <250 µm, relatively more material in the range 10–50 µm was produced. For unsieved parent samples, the size range associated with the dominant mode varied according to the length of the abrasion time. The coarsest mode (>63 µm) was dominant during the first 16 h of abrasion, then became less significant and is thought to be associated with the release of resident fines into suspension. The finest mode (<10 µm) was absent or very weak during the first 16h of abrasion, then became more significant and, in some instances, dominated the distribution as abrasion continued. Removal of grain surface coatings is the main source of fine material <10 µm, and this may be a significant source of fine material in areas where sands are dominated by subrounded and rounded particles. By comparison with previous studies of aeolian particle abrasion, these natural dune sands produced very low quantities of fine material (by weight), but their spatial extent makes them potentially a significant source of dust-sized particles at the global scale