Accessions of atmospheric dust east of Adelaide, South Australia, and the implications for pedogenesis

Abstract

Atmospheric dust and rainfall were collected at 19 locations within a 90 x 10 km study area extending eastwards from the coast near Adelaide, South Australia. Monthly collections for up to 3 years established seasonal and regional trends in fallout of particulate matter. Fallout was highest in the area of highest rainfall, but correlation of monthly rainfall with fallout was generally not statistically significant. The amount of dust collected was higher under tree foliage than in adjacent open space. Annual accession of atmospheric dust within this urban-rural transect was in the range of 5-10 t km-2 but the occasional severe dust storm could contribute about half the annual rate. These accretions of dust to the landscape, 2.5-5 mm per 1000 years, were about one hundredth of the recommended soil loss tolerance adopted in many studies of soil erosion, and thus unlikely to contribute significantly to models developed for soil loss on that basis. Dust accessions were, however, similar to estimates of rates of soil formation or profile deepening on resistant rocks of 1-5 mm per 1000 years which may be appropriate to conditions in southern Australia. Incorporation of such accessions into existing soils would be difficult to identify yet may provide a significant factor in pedogenesis in the higher rainfall areas. The low rates of soil development in many Australian landscapes, with contribution from both weathering and eolian dust inputs, would encourage the adoption of soil loss tolerances in soil erosion management that are orders of magnitude lower than those commonly accepted.