The Role of Dust in Biogeochemical Cycles

Here is an exploration of three interesting papers on dust and biogeochemical cycling. I will attempt to describe dust’s involvement in major biogeochemical cycles and then focus in on a specific example.  We have already discovered the powerful impact dust can have on the global climate system and the consideration of their impacts on biogeochemical cycling is imperative to enhance our understanding of earth systems science.

Harrison et al (2000) suggests that changing dust fluxes and depositional rates through time can have a significant consequence for productivity of marine and terrestrial ecosystems because of their nutrient carrying capacities. In turn, changes in biospheric productivity have a direct impact on atmospheric composition (e.g. CO₂ and N₂O) potentially resulting in the initiation of widespread and various feedback mechanisms.

Dust also makes up a god proportion of oceanic sediments downwind of major desert regions. In the North Pacific, for example, it is estimated that around 75-98% of sediments have aeolian origin. Marine ecosystems can thus be significantly affected by the mineral composition of dust loadings, most notably silicon, iron and phosphorus.

Like sediments, soils can also be strongly influenced by desert-originated dust flows. Once again, key nutrients are sourced from this aeolian activity and, as outlined in a previous post on Amazonian dust deposition, can considerably alter ecosystem equilibrium. Saharan dust is attributable to the addition of key trace species such as K, NH₄ and NO₂. Mineral dust is also particularly important where leaching predominates to maintain a healthy nutrient balance.

Whilst we can recognise the importance of aeolian dust in affecting global biogeochemical cycles, Lawrence and Neff (2009) show that it is also important to consider past changes in the global dust cycle. Ice-core and sediment data show dust deposition was greatest during glacial maxima. This evidence only adds to the complexity of changing feedbacks and resultant environmental changes. Geochemical fluxes resulting from dust deposition are most potent in close proximity to source regions, but have these source regions changed over time? Hsu et al (2009) reinforce this important aspect of changing geochemical flux by highlighting the reduction in the quantity of dust deposited with distance from the source.