scholarly journals Influence of measurement uncertainties on soluble aerosol iron over the oceans

2015 ◽  
Vol 12 (17) ◽  
pp. 14377-14400 ◽  
Author(s):  
N. Meskhidze ◽  
M. S. Johnson ◽  
D. Hurley ◽  
K. Dawson
Keyword(s):  
Transport Model ◽  
Mineral Dust ◽  
Operational Definition ◽  
Dust Aerosol ◽  
Global Ocean ◽  
Dust Particles ◽  
Chemical Transport Model ◽  
Water Leaching ◽  
Wide Range ◽  
Flow Through

Abstract. The atmospheric supply of dust iron (Fe) plays a crucial role in the Earth's biogeochemical cycle and is of specific importance as a micronutrient in the marine environment. Observations show several orders of magnitude variability in the fractional solubility of Fe in dust aerosols, making it hard to assess the role of mineral dust for global ocean biogeochemical Fe cycle. In this study we compare the operational solubility of dust aerosol Fe associated with one of the flow-through leaching protocols to the results of the global 3-D chemical transport model GEOS-Chem. In the protocol aerosol Fe is defined soluble by first deionized water leaching of mineral dust through a 0.45 μm pore size membrane followed by acidification and storage of the leachate over a long period of time prior to the analysis. To assess the concentrations of soluble Fe inferred by this flow-through leaching protocol we are using in situ measurements of dust size distribution with the prescribed of 50 % fractional solubility of Fe in less than 0.45 μm sized dust particles collected in the leachate. In the model, the fractional solubility of Fe is either explicitly calculated using complex dust Fe dissolution module, or prescribed to be 1 and 4 %. Calculations show that the fractional solubility of Fe derived through the flow-through leaching is typically higher compared to the model results. The largest differences (>30 %) are predicted to occur farther away from the dust source regions, over the areas where sub-0.45 μm sized mineral dust particles contribute a larger fraction of the total dust mass. This study suggests that inconsistences in the operational definition of soluble Fe could contribute to the wide range of the fractional solubility of dust aerosol Fe reported in the literature.

scholarly journals Atmospheric dissolved iron deposition to the global oceans: effects of oxalate-promoted Fe dissolution, photochemical redox cycling, and dust mineralogy

2013 ◽  
Vol 6 (1) ◽  
pp. 1901-1947 ◽  
Author(s):  
M. S. Johnson ◽  
N. Meskhidze
Keyword(s):  
Transport Model ◽  
Mineral Dust ◽  
Atmospheric Transport ◽  
Redox Cycling ◽  
Dust Particles ◽  
Dust Deposition ◽  
Chemical Transport Model ◽  
Cloud Processing ◽  
Form Model ◽  
Global Oceans

Abstract. Mineral dust deposition is suggested to be a significant atmospheric supply pathway of bioavailable iron (Fe) to Fe-depleted surface oceans. In this study, mineral dust and dissolved Fe (Fed) deposition rates are predicted for March 2009 to February 2010 using the 3-D chemical transport model GEOS-Chem implemented with a comprehensive dust-Fe dissolution scheme. The model simulates Fed production during the atmospheric transport of mineral dust taking into account inorganic and organic (oxalate)-promoted Fe dissolution processes, photochemical redox cycling between ferric (Fe(III)) and ferrous (Fe(II)) forms of Fe, dissolution of three different Fe-containing minerals (hematite, goethite, and aluminosilicates), and detailed mineralogy of wind-blown dust from the major desert regions. Our calculations suggest that during the yearlong simulation ~ 0.26 Tg (1 Tg = 1012 g) of Fed was deposited to global oceanic regions. Compared to simulations only taking into account proton-promoted Fe dissolution, the addition of oxalate to the dust-Fe mobilization scheme increased total annual model-predicted Fed deposition to global oceanic regions by ~ 75%. The implementation of Fe(II)/Fe(III) photochemical redox cycling in the model allows for the distinction between different oxidation states of deposited Fed. Our calculations suggest that during the daytime, large fractions of Fed deposited to the global oceans is likely to be in Fe(II) form, while nocturnal fluxes of Fed are largely in Fe(III) form. Model simulations also show that atmospheric fluxes of Fed can be strongly influenced by the mineralogy of Fe-containing compounds. This study indicates that Fed deposition to the oceans is controlled by total dust-Fe mass concentrations, mineralogy, the surface area of dust particles, atmospheric chemical composition, cloud processing, and meteorological parameters and exhibits complex and spatiotemporally variable patterns. Our study suggests that the explicit model representation of individual processes leading to Fed production within mineral dust are needed to improve the understanding of the atmospheric Fe cycle, and quantify the effect of dust-Fe on ocean biological productivity, carbon cycle, and climate.

scholarly journals Bioavailable atmospheric phosphorous supply to the global ocean: a 3-D global modelling study

2016 ◽  
Author(s):  
Stelios Myriokefalitakis ◽  
Athanasios Nenes ◽  
Alex R. Baker ◽  
Nikolaos Mihalopoulos ◽  
Maria Kanakidou
Keyword(s):  
Transport Model ◽  
Mineral Dust ◽  
Current Knowledge ◽  
Marine Ecosystem ◽  
Dust Aerosol ◽  
Anthropogenic Sources ◽  
Global Ocean ◽  
Spatial And Temporal Variability ◽  
Deposition Flux ◽  
P Mobilization

Abstract. The atmospheric cycle of phosphorus (P) is here parameterized in a global 3-D chemistry-transport model, taking into account primary emissions of total P (TP) and dissolved P (DP) associated with mineral dust, combustion particles of natural and anthropogenic sources, bioaerosols, sea-spray and volcanic aerosols. Global TP emissions are calculated to amount roughly 1.33 Tg-P yr−1 with mineral sources (about 1.10 Tg-P yr−1) contributing more than 80% to these emissions. Additionally, under acidic atmospheric conditions, for the present study we take into account the P mobilization from mineral dust, that is calculated to contribute about one third (0.14 Tg-P yr−1) to the global DP atmospheric source. The calculated global annual DP deposition flux equals to 0.43 Tg-P yr−1 (about 40 % enters the ocean), and shows a strong spatial and temporal variability. Considering that all bioaerosol P is bioavailable (BP) and accounting for all other sources of DP, a flux of 0.16 Tg-P yr−1 BP to the ocean is derived. Present day simulations of atmospheric P aerosol concentrations and deposition fluxes are satisfactory compared with available observations, indicating however a 50 % uncertainty of current knowledge on primary and secondary sources of P that drive its atmospheric cycle. Sensitivity simulations using preindustrial (year 1850) and future (2100) anthropogenic and biomass burning emission scenarios, showed a present-day increase of 75 % in the dissolution flux of P present in dust aerosol compared to the 1850 dissolution flux due to increasing atmospheric acidity over the last 150 years. Future reductions in air pollutants, due to the implementation of air-quality regulations, are expected to decrease P mobilization flux by about 30 % for the year 2100 compared to the present-day. A striking result is that more than 50% of the BP deposition flux to the ocean originates from biological particle and this contribution is found to maximize in summer when atmospheric deposition impact on the marine ecosystem is the highest due to ocean stratification. These findings reveal the largely unknown but important role of terrestrial bioaerosols as suppliers of bioavailable P to the ocean – with very important implications for past and future responses of ecosystems to global change. Therefore, our study provides new insights to the atmospheric P cycle by demonstrating that bioaerosols are as important carriers of bioavailable P as dust aerosol, that was up to now considered as the only large source of DP external to the open ocean.

scholarly journals Impacts of long-range-transported mineral dust on summertime convective cloud and precipitation: a case study over the Taiwan region

2021 ◽  
Vol 21 (23) ◽  
pp. 17433-17451
Author(s):  
Yanda Zhang ◽  
Fangqun Yu ◽  
Gan Luo ◽  
Jiwen Fan ◽  
Shuai Liu
Keyword(s):  
Long Range ◽  
Transport Model ◽  
Mineral Dust ◽  
Convective Cloud ◽  
Dust Particles ◽  
Chemical Transport Model ◽  
Dust Aerosols ◽  
Convective Clouds ◽  
Water Contents

Abstract. As one of the most abundant atmospheric aerosols and effective ice nuclei, mineral dust affects clouds and precipitation in the Earth system. Here numerical experiments are carried out to investigate the impacts of dust aerosols on summertime convective clouds and precipitation over the mountainous region of Taiwan by acting as ice-nucleating particles. We run the Weather Research and Forecasting model (WRF) with the Morrison two-moment and spectral-bin microphysics (SBM) schemes at 3 km resolution, using dust number concentrations from a global chemical transport model (GEOS-Chem-APM). The case study indicates that the long-range-transported mineral dust, with relatively low number concentrations, can notably affect the properties of convective clouds (ice and liquid water contents, cloud top height, and cloud coverage) and precipitation (spatial pattern and intensity). The effects of dust are evident during strong convective periods, with significantly increased ice water contents in the mixed-phase regime via the enhanced heterogeneous freezing. With both the Morrison and SBM schemes, we see the invigoration effects of dust aerosols on the convective intensity through enhanced condensation and deposition latent heating. The low-altitude dust particles are uplifted to the freezing level by updrafts, which, in turn, enhance the convective cloud development through immersion freezing and convective invigoration. Compared to the Morrison scheme, the SBM scheme predicts more realistic precipitation and different invigoration effects of dust. The differences are partially attributed to the saturation adjustment approach utilized in the bulk scheme, which leads to a stronger enhancement of condensation at midlatitudes to low altitudes and a weaker deposition increase at the upper level.

scholarly journals Atmospheric dissolved iron deposition to the global oceans: effects of oxalate-promoted Fe dissolution, photochemical redox cycling, and dust mineralogy

2013 ◽  
Vol 6 (4) ◽  
pp. 1137-1155 ◽  
Author(s):  
M. S. Johnson ◽  
N. Meskhidze
Keyword(s):  
Transport Model ◽  
Mineral Dust ◽  
Atmospheric Transport ◽  
Redox Cycling ◽  
Dust Particles ◽  
Dust Deposition ◽  
Chemical Transport Model ◽  
Cloud Processing ◽  
Form Model ◽  
Global Oceans

Abstract. Mineral dust deposition is suggested to be a significant atmospheric supply pathway of bioavailable iron (Fe) to Fe-depleted surface oceans. In this study, mineral dust and dissolved Fe (Fed) deposition rates are predicted for March 2009 to February 2010 using the 3-D chemical transport model GEOS-Chem implemented with a comprehensive dust-Fe dissolution scheme. The model simulates Fed production during the atmospheric transport of mineral dust, taking into account inorganic and organic (oxalate)-promoted Fe dissolution processes, photochemical redox cycling between ferric (Fe(III)) and ferrous (Fe(II)) forms of Fe, dissolution of three different Fe-containing minerals (hematite, goethite, and aluminosilicates), and detailed mineralogy of wind-blown dust from the major desert regions. Our calculations suggest that during the year-long simulation ~0.26 Tg (1 Tg = 1012 g) of Fed was deposited to global oceanic regions. Compared to simulations only taking into account proton-promoted Fe dissolution, the addition of oxalate and Fe(II)/Fe(III) redox cycling to the dust-Fe mobilization scheme increased total annual model-predicted Fed deposition to global oceanic regions by ~75%. The implementation of Fe(II)/Fe(III) photochemical redox cycling in the model also allows for the distinction between different oxidation states of deposited Fed. Our calculations suggest that during the daytime, large fractions of Fed deposited to the global oceans is likely to be in Fe(II) form, while nocturnal fluxes of Fed are largely in Fe(III) form. Model sensitivity simulations suggest Fed fluxes to the oceans can range from ~50% reduction to ~150% increase associated with the uncertainty in Fe-containing minerals commonly found in dust particles. This study indicates that Fed deposition to the oceans is controlled by total dust-Fe mass concentrations, mineralogy, the surface area of dust particles, atmospheric chemical composition, cloud processing, and meteorological parameters and exhibits complex and spatiotemporally variable patterns. Our study suggests that the explicit model representation of individual processes leading to Fed production within mineral dust are needed to improve the understanding of the atmospheric Fe cycle, and quantify the effect of dust-Fe on ocean biological productivity, carbon cycle, and climate.

scholarly journals Impacts of long-range transported mineral dust on summertime convective cloud and precipitation: a case study over the Taiwan region

2021 ◽  
Author(s):  
Yanda Zhang ◽  
Fangqun Yu ◽  
Gan Luo ◽  
Jiwen Fan ◽  
Shuai Liu
Keyword(s):  
Long Range ◽  
Transport Model ◽  
Mineral Dust ◽  
Convective Cloud ◽  
Dust Particles ◽  
Chemical Transport Model ◽  
Dust Aerosols ◽  
Low Altitude ◽  
Water Contents

Abstract. As one of the most abundant atmospheric aerosols and effective ice nuclei, mineral dust particles affect clouds and precipitation in the Earth system. Here numerical experiments are carried out to investigate the impacts of dust aerosols on summertime convective clouds and precipitation over the mountainous region in Taiwan. We run the Weather Research and Forecasting model (WRF) coupled with the spectral-bin microphysics (SBM) and Morrison two-moment (Morr2) schemes at 3 km resolution, with the dust number concentrations from a global chemical transport model (GEOS-Chem-APM). The case study indicates that the long-range transported dust, with relatively low number concentrations, can notably affect the properties of convective cloud (ice/liquid water contents, cloud top height, and cloud coverage) and precipitation (spatial pattern and intensity). The dust effects are evident during the strong convective periods, significantly increasing the ice water contents in the mixed-phase regime via the enhanced heterogeneous freezing. With both the Morr2 and SBM schemes, we see invigoration effects of dust aerosols on the convective intensity through enhanced condensation and deposition latent heating. In this process, the low-altitude dust particles are uplifted to the freezing level by updrafts which, in turn, enhance the convective cloud development through immersion freezing and convective invigoration. Comparing to the Morr2 scheme, the SBM scheme predicts more realistic precipitation and different invigoration effects of dust. The differences are partially attributed to the saturation adjustment approach utilized in the bulk scheme, leading to the stronger enhancement of condensation at mid-low altitude and weaker deposition increase at the upper level.

scholarly journals Hygroscopicity of Different Types of Aerosol Particles: Case Studies Using Multi-Instrument Data in Megacity Beijing, China

2020 ◽  
Vol 12 (5) ◽  
pp. 785 ◽  
Author(s):  
Tong Wu ◽  
Zhanqing Li ◽  
Jun Chen ◽  
Yuying Wang ◽  
Hao Wu ◽  
...  
Keyword(s):  
Enhancement Factor ◽  
Mineral Dust ◽  
Aerosol Particles ◽  
Dust Aerosol ◽  
Dust Particles ◽  
Chemical Components ◽  
Hygroscopic Growth ◽  
Microphysical Properties ◽  
Fine Mode ◽  
Fine Mode Aerosol

Water uptake by aerosol particles alters its light-scattering characteristics significantly. However, the hygroscopicities of different aerosol particles are not the same due to their different chemical and physical properties. Such differences are explored by making use of extensive measurements concerning aerosol optical and microphysical properties made during a field experiment from December 2018 to March 2019 in Beijing. The aerosol hygroscopic growth was captured by the aerosol optical characteristics obtained from micropulse lidar, aerosol chemical composition, and aerosol particle size distribution information from ground monitoring, together with conventional meteorological measurements. Aerosol hygroscopicity behaves rather distinctly for mineral dust coarse-mode aerosol (Case I) and non-dust fine-mode aerosol (Case II) in terms of the hygroscopic enhancement factor, f β ( R H , λ 532 ) , calculated for the same humidity range. The two types of aerosols were identified by applying the polarization lidar photometer networking method (POLIPHON). The hygroscopicity for non-dust aerosol was much higher than that for dust conditions with the f β ( R H , λ 532 ) being around 1.4 and 3.1, respectively, at the relative humidity of 86% for the two cases identified in this study. To study the effect of dust particles on the hygroscopicity of the overall atmospheric aerosol, the two types of aerosols were identified and separated by applying the polarization lidar photometer networking method in Case I. The hygroscopic enhancement factor of separated non-dust fine-mode particles in Case I had been significantly strengthened, getting closer to that of the total aerosol in Case II. These results were verified by the hygroscopicity parameter, κ (Case I non-dust particles: 0.357 ± 0.024; Case II total: 0.344 ± 0.026), based on the chemical components obtained by an aerosol chemical speciation instrument, both of which showed strong hygroscopicity. It was found that non-dust fine-mode aerosol contributes more during hygroscopic growth and that non-hygroscopic mineral dust aerosol may reduce the total hygroscopicity per unit volume in Beijing.

scholarly journals Heterogeneous reactions of mineral dust aerosol: implications for tropospheric oxidation capacity

2017 ◽  
Author(s):  
Mingjin Tang ◽  
Xin Huang ◽  
Keding Lu ◽  
Maofa Ge ◽  
Yongjie Li ◽  
...  
Keyword(s):  
Mineral Dust ◽  
Dust Aerosol ◽  
Heterogeneous Reactions ◽  
Dust Particles ◽  
Laboratory Studies ◽  
Research Strategies ◽  
Aerosol Composition ◽  
Oxidation Capacity ◽  
Open Questions ◽  
Modelling Studies

Abstract. Heterogeneous reactions of mineral dust aerosol with trace gases in the atmosphere could directly and indirectly affect tropospheric oxidation capacity, in addition to aerosol composition and physicochemical properties. In this article we provide a comprehensive and critical review of laboratory studies of heterogeneous uptake of OH, NO3, O3, and their directly related species as well (including HO2, H2O2, HCHO, HONO, and N2O5) by mineral dust particles. Atmospheric importance of heterogeneous uptake as sinks for these species are assessed (i) by comparing their lifetimes with respect to heterogeneous reactions with mineral dust to lifetimes with respect to other major loss processes and (ii) by discussing relevant field and modelling studies. We have also outlined major open questions and challenges in laboratory studies of heterogeneous uptake by mineral dust and discussed research strategies to address them in order to better understand the effects of heterogeneous reactions with mineral dust on tropospheric oxidation capacity.

scholarly journals Bioavailable atmospheric phosphorous supply to the global ocean: a 3-D global modeling study

2016 ◽  
Vol 13 (24) ◽  
pp. 6519-6543 ◽  
Author(s):  
Stelios Myriokefalitakis ◽  
Athanasios Nenes ◽  
Alex R. Baker ◽  
Nikolaos Mihalopoulos ◽  
Maria Kanakidou
Keyword(s):  
Transport Model ◽  
Mineral Dust ◽  
Current Knowledge ◽  
Marine Ecosystem ◽  
Anthropogenic Sources ◽  
Global Ocean ◽  
Spatial And Temporal Variability ◽  
Deposition Flux ◽  
P Solubilization ◽  
Global Study

Abstract. The atmospheric cycle of phosphorus (P) is parameterized here in a state-of-the-art global 3-D chemistry transport model, taking into account primary emissions of total P (TP) and soluble P (DP) associated with mineral dust, combustion particles from natural and anthropogenic sources, bioaerosols, sea spray and volcanic aerosols. For the present day, global TP emissions are calculated to be roughly 1.33 Tg-P yr−1, with the mineral sources contributing more than 80 % to these emissions. The P solubilization from mineral dust under acidic atmospheric conditions is also parameterized in the model and is calculated to contribute about one-third (0.14 Tg-P yr−1) of the global DP atmospheric source. To our knowledge, a unique aspect of our global study is the explicit modeling of the evolution of phosphorus speciation in the atmosphere. The simulated present-day global annual DP deposition flux is 0.45 Tg-P yr−1 (about 40 % over oceans), showing a strong spatial and temporal variability. Present-day simulations of atmospheric P aerosol concentrations and deposition fluxes are satisfactory compared with available observations, indicating however an underestimate of about 70 % on current knowledge of the sources that drive the P atmospheric cycle. Sensitivity simulations using preindustrial (year 1850) anthropogenic and biomass burning emission scenarios showed a present-day increase of 75 % in the P solubilization flux from mineral dust, i.e., the rate at which P is converted into soluble forms, compared to preindustrial times, due to increasing atmospheric acidity over the last 150 years. Future reductions in air pollutants due to the implementation of air-quality regulations are expected to decrease the P solubilization flux from mineral dust by about 30 % in the year 2100 compared to the present day. Considering, however, that all the P contained in bioaerosols is readily available for uptake by marine organisms, and also accounting for all other DP sources, a total bioavailable P flux of about 0.17 Tg-P yr−1 to the oceans is derived. Our calculations further show that in some regions more than half of the bioavailable P deposition flux to the ocean can originate from biological particles, while this contribution is found to maximize in summer when atmospheric deposition impact on the marine ecosystem is the highest due to ocean stratification. Thus, according to this global study, a largely unknown but potentially important role of terrestrial bioaerosols as suppliers of bioavailable P to the global ocean is also revealed. Overall, this work provides new insights to the atmospheric P cycle by demonstrating that biological materials are important carriers of bioavailable P, with very important implications for past and future responses of marine ecosystems to global change.

scholarly journals Response of acid mobilization of iron-containing mineral dust to improvement of air quality projected in the future

2013 ◽  
Vol 13 (10) ◽  
pp. 28173-28223 ◽  
Author(s):  
A. Ito ◽  
L. Xu
Keyword(s):  
Air Quality ◽  
Environmental Changes ◽  
Transport Model ◽  
Mineral Dust ◽  
Chemical Transport Model ◽  
Iron Solubility ◽  
The Future ◽  
Northeastern Pacific ◽  
Combustion Aerosols ◽  
Quantitative Understanding

Abstract. Acidification of dust aerosols may increase aerosol iron (Fe) solubility, which is linked to mineral properties. Combustion aerosols can also elevate aerosol iron solubility when aerosol loading is low. Here, we use an atmospheric chemical transport model to investigate the deposition of filterable iron and its response to changes in anthropogenic emissions of both combustion aerosols and precursor gases. By introducing three classes of iron-containing minerals into the detailed aerosol chemistry model, we provide a theoretical examination of the effects of different dissolution behaviors on the acid mobilization of iron. Comparisons of modeled Fe dissolution curves with the measured dissolution rates for African (Tibesti) and Asian (Beijing) dust samples show overall good agreement under acidic conditions. The improved treatment of Fe in mineral dust and its dissolution scheme results in reasonable predictive capability for iron solubility over the oceans in the Northern Hemisphere. Our model results suggest that the improvement of air quality projected in the future will lead to a decrease of the filterable iron deposition from iron-containing mineral dust to the northeastern Pacific due to less acidification in Asian dust, which is mainly associated with the reduction of nitrogen oxides (NOx) emissions. These results could have important implications for iron fertilization of phytoplankton growth, and highlight the necessity of improving the process-based quantitative understanding of the response of the chemical modification in iron-containing minerals to environmental changes.

scholarly journals A new dust cycle model with dynamic vegetation: LPJ-dust version 1.0

2011 ◽  
Vol 4 (1) ◽  
pp. 85-105 ◽  
Author(s):  
S. Shannon ◽  
D. J. Lunt
Keyword(s):  
Transport Model ◽  
Surface Concentration ◽  
Reanalysis Data ◽  
Dust Particles ◽  
Dust Deposition ◽  
Chemical Transport Model ◽  
Cycle Model ◽  
Dynamic Global Vegetation Model ◽  
Cloud Scavenging ◽  
Global Vegetation

Abstract. This paper presents a new offline dust cycle model which uses the Lund-Potsdam-Jena dynamic global vegetation model (Sitch et al., 2003) to calculate time varying dust sources. Surface emissions are calculated by simulating the processes of saltation and sandblasting using an existing model (Tegen et al., 2002). Dust particles are transported using the TOMCAT chemical transport model (Chipperfield, 2006). Dust particles are removed from the atmosphere by dry deposition and sub-cloud scavenging. The model is designed so that it can be driven using reanalysis data or GCM derived fields. To improve the performance of the model, threshold values for vegetation cover, soil moisture, snow depth and threshold friction velocity, used to determine surface emissions are tuned. The effectiveness of three sub-cloud scavenging schemes are also tested. An ensemble of tuning experiments are evaluated against dust deposition and surface concentration measurements. Surface emissions which produce the best agreement with observations range from 1600 to 2400 Mtyr−1.

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