@article{fdi:010063613,
  title = {{D}ominance of goethite over hematite in iron oxides of mineral dust from {W}estern {A}frica : quantitative partitioning by {X}-ray absorption spectroscopy},
  author = {{F}ormenti, {P}. and {C}aquineau, {S}andrine and {C}hevaillier, {S}. and {K}laver, {A}. and {D}esboeufs, {K}. and {R}ajot, {J}ean-{L}ouis and {B}elin, {S}. and {B}riois, {V}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}his paper reports on the {X}-ray absorption analysis of samples of mineral dust emitted from or transported to {W}estern {A}frica. {W}e found that iron oxides account, by mass, for 38% to 72% of the total elemental iron. {T}hey are composed of minerals in the {F}e({III}) oxidation state: goethite ({F}e{O} center dot {OH}) and hematite ({F}e2{O}3). {T}he apparent fraction of iron oxide attributed to goethite is higher than hematite regardless of the source region from which the dust originated. {T}he goethite percent content of iron oxides is in the range 52-78% (by mass), the highest values being measured for dust originating in the {S}ahel. {T}he limited number of samples analyzed and the sample-to-sample variability prevent us from concluding firmly on the regional variability of the goethite-to-hematite ratio. {B}ased on the experimental data on mineralogical composition and on concurrent measurements of the number size distribution, the optical properties of mineral dust have been calculated in a {M}ie approximation for homogeneous spherical particles. {A}t 550 nm, the single-scattering albedo omega(0) ranges between 0.89 and 0.93, the asymmetry factor g ranges between 0.76 and 0.8 and the mass extinction efficiency k(ext) varies between 0.5 and 1.1 m(2) g(-1); these values are all in the range of those from independent direct measurements. {N}eglecting the partitioning between hematite and goethite and the assimilation of iron oxides by hematite, as it is often done with models, lowers the single-scattering albedo and increases the asymmetry factor in the {UV}-visible spectral region below 550 nm. {T}he mass extinction efficiency is insensitive to the nature of the iron oxides but rather responds to variations in the number size distribution. {T}he mineralogy of iron oxides should therefore be taken into account when assessing the effect of mineral dust on climate and atmospheric chemistry, in particular via interactions involving photolysis.},
  keywords = {{AFRIQUE} {DE} {L}'{OUEST} ; {NIGER} ; {ZONE} {SAHELIENNE}},
  booktitle = {},
  journal = {{J}ournal of {G}eophysical {R}esearch : {A}tmospheres},
  volume = {119},
  numero = {22},
  pages = {12740--12754},
  ISSN = {2169-897{X}},
  year = {2014},
  DOI = {10.1002/2014jd021668},
  URL = {https://www.documentation.ird.fr/hor/fdi:010063613},
}