A time-averaged inventory of subaerial volcanic sulfur (S) emissions was compiled primarily for the use of global S and sulfate modelers. This inventory relies upon the 25-year history of S, primarily sulfur dioxide (SO2), measurements at volcanoes. Subaerial volcanic SO2 emissions indicate a 13 Tg/a SO2 time-averaged flux, based upon an early 1970s to 1997 time frame. When considering other S species present in volcanic emissions, a time-averaged inventory of subaerial volcanic S fluxes is 10.4 Tg/a S. These time-averaged fluxes are conservative minimum fluxes since they rely upon actual measurements. The temporal, spatial, and chemical inhomogeneities inherent to this system gave higher S fluxes in specific years. Despite its relatively small proportion in the atmospheric S cycle, the temporal and spatial distribution of volcanic S emissions provide disproportionate effects at local, regional, and global scales. This work contributes to the Global Emissions Inventory Activity.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/98JD02091

A time‐averaged inventory of subaerial volcanic sulfur emissions

The accumulation of secondary acids and am- monium on individual mineral dust particles during ACE- Asia has been measured with an online single-particle mass spectrometer, the ATOFMS. Changes in the amounts of sul- phate, nitrate, and chloride mixed with dust particles cor- relate with air masses from different source regions. The uptake of secondary acids depended on the individual dust particle mineralogy; high amounts of nitrate accumulated on calcium-rich dust while high amounts of sulphate accumu- lated on aluminosilicate-rich dust. Oxidation of S(IV) to S(VI) by iron in the aluminosilicate dust is a possible expla- nation for this enrichment of sulphate, which has important consequences for the fertilization of remote oceans by solu- ble iron. This study shows the segregation of sulphate from nitrate and chloride in individual aged dust particles for the first time. A transport and aging timeline provides an expla- nation for the observed segregation. Our data suggests that sulphate became mixed with the dust first. This implies that the transport pathway is more important than the reaction ki- netics in determining which species accumulate on mineral dust. Early in the study, dust particles in volcanically influ- enced air masses were mixed predominately with sulphate. Dust mixed with chloride then dominated over sulphate and nitrate when a major dust front reached the R. V. Ronald Brown. We hypothesize that the rapid increase in chloride on dust was due to mixing with HCl(g) released from acidi- fied sea salt particles induced by heterogeneous reaction with volcanic SO2(g), prior to the arrival of the dust front. The amount of ammonium mixed with dust correlated strongly with the total amount of secondary acid reaction products in the dust. Submicron dust and ammonium sulphate were internally mixed, contrary to frequent reports that they ex- ist as external mixtures. The size distribution of the mixing state of dust with these secondary species validates previ- ous mechanisms of the atmospheric processing of dust and generally agrees with simulated aerosol chemistry from the STEM-2K3 model. This series of novel results has important implications for improving the treatment of dust in global chemistry models and highlights a number of key processes that merit further investigation through laboratory and field studies.

/pdf/direct-observations-of-the-atmospheric-processing-of-asian-31qsdhk74b.pdf

Direct observations of the atmospheric processing of Asian mineral dust

Tropospheric aqueous-phase chemistry: kinetics, mechanisms, and its coupling to a changing gas phase.

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/pdf/transition-metals-in-atmospheric-liquid-phases-sources-23erdad8w0.pdf

Transition Metals in Atmospheric Liquid Phases: Sources, Reactivity, and Sensitive Parameters

. We use a 3-D global chemical transport model (GEOS-Chem) to interpret aircraft observations of nitrate and sulfate partitioning in transpacific dust plumes during the INTEX-B campaign of April–May 2006. The model includes explicit transport of size-resolved mineral dust and its alkalinity, nitrate, and sulfate content. The observations show that particulate nitrate is primarily associated with dust, sulfate is primarily associated with ammonium, and Asian dust remains alkaline across the Pacific. This can be reproduced in the model by using a reactive uptake coefficient for HNO3 on dust (γ(HNO3) ~10−3) much lower than commonly assumed in models and possibly reflecting limitation of uptake by dust dissolution. The model overestimates gas-phase HNO3 by a factor of 2–3, typical of previous model studies; we show that this cannot be corrected by uptake on dust. We find that the fraction of aerosol nitrate on dust in the model increases from ~30% in fresh Asian outflow to 80–90% over the Northeast Pacific, reflecting in part the volatilization of ammonium nitrate and the resulting transfer of nitrate to the dust. Consumption of dust alkalinity by uptake of acid gases in the model is slow relative to the lifetime of dust against deposition, so that dust does not acidify (at least not in the bulk). This limits the potential for dust iron released by acidification to become bio-available upon dust deposition. Observations in INTEX-B show no detectable ozone depletion in Asian dust plumes, consistent with the model. Uptake of HNO3 by dust, suppressing its recycling to NOx, reduces Asian pollution influence on US surface ozone in the model by 10–15% or up to 1 ppb.

/pdf/impact-of-mineral-dust-on-nitrate-sulfate-and-ozone-in-2ovz90na6g.pdf

Impact of mineral dust on nitrate, sulfate, and ozone in transpacific Asian pollution plumes

The role of free fall atmospheric dust in catalysing autoxidation of aqueous sulphur dioxide

Iron, manganese and copper concentrations in wet precipitations and kinetics of the oxidation of SO2 in rain water at two urban sites, Jaipur and Kota, in Western India

Kinetics of atmospheric oxidation of nitrous acid by oxygen in aqueous medium

Role of cuprous oxide in the autoxidation of aqueous sulphur dioxide and its atmospheric implications

For getting an insight into the mechanism of atmospheric autoxidation of sulfur(IV), the kinetics of this autoxidation reaction catalyzed by CoO, Co2O3 and Ni2O3 in buffered alkaline medium has been studied, and found to be defined by Eqs. I and II for catalysis by cobalt oxides and Ni2O3, respectively.

$$ - {\text{d}}\left[ {{\text{S}}\left( {{\text{IV}}} \right)} \right]/{\text{d}}t = AK_{ 2} \left[ {{\text{Catalyst}}} \right]\left[ {{\text{S}}\left( {{\text{IV}}} \right)} \right] \left[ {{\text{O}}_{ 2} } \right] /\left( { 1+ K_{ 2} \left[ {{\text{O}}_{ 2} } \right]} \right) $$

(I)



$$ - {\text{d}}\left[ {{\text{S}}\left( {{\text{IV}}} \right)} \right]/{\text{d}}t = k_{ 1} K_{ 1} \left[ {{\text{Ni}}_{ 2} {\text{O}}_{ 3} } \right]\left[ {{\text{S}}\left( {{\text{IV}}} \right)} \right]\left[ {{\text{O}}_{ 2} } \right]/\left\{ { 1+ K_{ 1} \left[ {{\text{S}}\left( {{\text{IV}}} \right)} \right]} \right\} $$

(II)

The values of empirical rate parameters were: A{0.22(CoO), 0.8 L mol−1s−1 (Co2O3)}, K1{2.5 × 102 (Ni2O3)}, K2{2.5 × 102(CoO), 0.6 × 102 (Co2O3)} and k1{5.0 × 10−2(Ni2O3), 1.0 × 10−6(CoO), 1.7 × 10−5 s−1(Co2O3)} at pH 8.20 (CoO and Co2O3) and pH 7.05 (Ni2O3) and 30 °C. This is perhaps the first study in which the detailed kinetics in the presence of ethanol, a well known free radical scavenger for oxysulfur radicals, has been carried out, and the rate laws for catalysis by cobalt oxides and Ni2O3 in the presence of ethanol were Eqs. III and IV, respectively.

$$ - {\text{d}}\left[ {{\text{S}}\left( {{\text{IV}}} \right)} \right]/{\text{d}}t = AK_{ 2} \left[ {{\text{CoO}}} \right]\left[ {{\text{S}}\left( {{\text{IV}}} \right)} \right]\left[ {{\text{O}}_{ 2} } \right]/\left\{ {\left( { 1+ C\left[ {{\text{Ethanol}}} \right]} \right)\left( { 1+ K_{ 2} \left[ {{\text{O}}_{ 2} } \right]} \right)} \right\} $$

(III)



$$ - {\text{d}}\left[ {{\text{S}}\left( {{\text{IV}}} \right)} \right]/{\text{d}}t = {k_1}{K_1}\left[ {{\text{Ni}}_{ 2} {\text{O}}_{ 3} } \right]\left[ {{\text{S}}\left( {{\text{IV}}} \right)} \right]\left[ {{\text{O}}_{ 2} } \right]/\left\{ {\left( { 1+ {K_1}\left[ {{\text{S}}\left( {{\text{IV}}} \right)} \right]} \right)\left( { 1+ C\left[ {{\text{Ethanol}}} \right]} \right)} \right\} $$

(IV)

For comparison, the effect of ethanol on these catalytic reactions was studied in acidic medium also. In addition, alkaline medium, the values of the inhibition factor C were 1.9 × 104 and 4.0 × 103 L mol−1 s for CoO and Co2O3, respectively; for Ni2O3, C was only 3.0 × 102 only. On the other hand, in acidic medium, the values of this factor were all low: 20 (CoO), 0.7 (Co2O3) and 1.4 (Ni2O3). Based on these results, a radical mechanism for CoO and Co2O3 catalysis in alkaline medium, and a nonradical mechanism for Ni2O3 in both alkaline and acidic media and for cobalt oxides in acidic media are proposed.

K. S. Gupta

Papers

The role of free fall atmospheric dust in catalysing autoxidation of aqueous sulphur dioxide

Iron, manganese and copper concentrations in wet precipitations and kinetics of the oxidation of SO2 in rain water at two urban sites, Jaipur and Kota, in Western India

Kinetics of atmospheric oxidation of nitrous acid by oxygen in aqueous medium

Role of cuprous oxide in the autoxidation of aqueous sulphur dioxide and its atmospheric implications

Kinetics of the uninhibited and ethanol-inhibited CoO, Co2O3 and Ni2O3 catalyzed autoxidation of sulfur(IV) in alkaline medium