Modeling the global emission, transport and deposition of trace elements associated with mineral dust

Abstract

Abstract. Trace element deposition from desert dust has important impacts on ocean primary productivity, the quantification of which could be useful in determining the magnitude and sign of the biogeochemical feedback on radiative forcing. However, the impact of elemental deposition to remote ocean regions is not well understood and is not currently included in global climate models. In this study, emission inventories for eight elements primarily of soil origin, Mg, P, Ca, Mn, Fe, K, Al, and Si are determined based on a global mineral data set and a soil data set. The resulting elemental fractions are used to drive the desert dust model in the Community Earth System Model (CESM) in order to simulate the elemental concentrations of atmospheric dust. Spatial variability of mineral dust elemental fractions is evident on a global scale, particularly for Ca. Simulations of global variations in the Ca / Al ratio, which typically range from around 0.1 to 5.0 in soils, are consistent with observations, suggesting that this ratio is a good signature for dust source regions. The simulated variable fractions of chemical elements are sufficiently different; estimates of deposition should include elemental variations, especially for Ca, Al and Fe. The model results have been evaluated with observations of elemental aerosol concentrations from desert regions and dust events in non-dust regions, providing insights into uncertainties in the modeling approach. The ratios between modeled and observed elemental fractions range from 0.7 to 1.6, except for Mg and Mn (3.4 and 3.5, respectively). Using the soil database improves the correspondence of the spatial heterogeneity in the modeling of several elements (Ca, Al and Fe) compared to observations. Total and soluble dust element fluxes to different ocean basins and ice sheet regions have been estimated, based on the model results. The annual inputs of soluble Mg, P, Ca, Mn, Fe and K associated with dust using the mineral data set are 0.30 Tg, 16.89 Gg, 1.32 Tg, 22.84 Gg, 0.068 Tg, and 0.15 Tg to global oceans and ice sheets.

The Effect of Atmospheric Acid Processing on the Global Deposition of Bioavailable Phosphorus From Dust

“…Regional trends show good agreement with other studies: The North Atlantic Ocean is the globally dominant region for deposition, with the North Pacific Ocean and Indian Ocean also important regions for deposition. Our results show good agreement with Zhang et al (), who similarly only considered mineral dust, in all regions except for the North Atlantic for which the authors estimate an additional 40% deposition of TP. Okin et al () and Myriokefalitakis et al () estimate similar fluxes for the Atlantic Ocean but estimate a factor of ~2 to 3 greater deposition to the Pacific and Indian oceans.…”

Impact of snow deposition on major and trace element concentrations and elementary fluxes in surface waters of the Western Siberian Lowland across a 1700 km latitudinal gradient

“…In order to assess a snapshot of snow deposition across a 1700 km latitudinal profile and collect the freshest snow that was subject to minimal transformation, we chose to sample only the upper layer of the snow cover. This technique, in contrast to traditional sampling of entire snow columns (i.e., Guéguen et al, 2016;Niu et al, 2017), allows an adequate representation of the upper fresh snow layer that had minimal transformation at the soil, and frequently used in remote regions (Kang et al, 2007;Zhang et al, 2015). The isotope composition of collected snow proved its fresh character, not subject to any metamorphism (Vasil'chuk et al, 2016).…”

“…In boreal and subarctic regions, both dissolved and particulate fractions of snow water reflect the air chemistry in winter, when the land is covered by snow and the water surfaces are frozen. During winter, the input of mineral compounds from adjacent regions is minimal and the main factor controlling chemical composition of snow is long-range, over hundreds and thousands of kilometers, atmospheric transport (Franzén et al, 1994;Huang et al, 2015;, Shevchenko et al, 2000, 2010Welch et al, 1991;Zdanowicz et al, 1998Zdanowicz et al, , 2006Krachler et al, 2005;Zhang et al, 2015).…”

Spatial variability of ocean fertilizing nutrients in the dust‐emitting ephemeral river catchments of Namibia

“…Similarly, the bioavailable fractions of P (Mehlich P) and N (nitrate (NO 3 − ) and ammonium (NH 4 + )) were determined with the addition of total P (TP) and total N (TN) to consider relationships between the bioavailable and total portions of the P and N cycles. It is important to note that bioavailable nutrient concentrations measured in source sediments are considered conservative in comparison to deposition‐captured sediment that has undergone atmospheric processing during aeolian transport, known to increase nutrient bioavailability (Nenes et al, ; Zhang et al, ).…”