Chemical characterization of ambient aerosol collected during the southwest monsoon and intermonsoon seasons over the Arabian Sea: Labile-Fe(II) and other trace metals

摘要: Atmospheric deposition of iron (Fe) to certain regions the oceans is an important nutrient source Fe biota, and ability biota uptake dependent on speciation Fe. Therefore understanding in atmosphere critical role as a surface ocean waters. Labile ferrous (Fe(II)) concentrations well total for other trace metals, cations, anions were determined over Arabian Sea two nonconsecutive months during 1995. Ambient aerosol samples collected Indian Ocean intermonsoon southwest monsoon seasons Sea. Sampling took place aboard German research vessel Meteor May (leg M32/3; intermonsoon) July/August M32/5; monsoon). Both cruise tracks followed 65th east meridian, traveling 30 days each (from north south leg M32/3 from M32/5). A high-volume dichotomous virtual impactor with aerodynamic cutoff size 3 μm was used collect fine coarse fractions metal analysis. low volume collector anion cation The analysis labile-Fe(II) done immediately after sample collection minimize any possible redox reactions which might occur storage. analytical procedure involved filter extraction formate/formic acid buffered solution at pH 4.2 by colorimetric quantification soluble Fe(II). Metals, anions, cations analyzed cruise. Total atmospheric aqueous-labile-Fe(II) between 4.75 80%) present fraction (<3.0 μm). During monsoon, consistently below detection limit (<0.34 <0.089 ng m^(−3), depending air sampled). Air mass back trajectories (5 day, three dimensional) showed that masses sampled had advected open Ocean, while northeast Africa, Saudi peninsula, southern Asia. These calculations consistent results statistical performed data set variance due crustal species greater than monsoon. factor scores components also when nearby continental masses. Principal component where aqueous labile Fe(II) above limit. Aqueous did not correlate indicating processing advection.