| Bioavailable iron is one of the most important micronutrien for phytoplankton blooms, it has been suggested that 30%～50% of the oceans are comprised of high-nutrient low-chlorophyll (HNLC) regions where phytoplankton primary productivity is limited by the amount of bioavailable iron. Atmospheric dust deposition is a major external iron source for remote surface ocean waters,while it has a low solubility due to its stable chemical bonds in sea water. Anthropogenic source aerosol can not only provide the higher soluble iron, but also supply a variety of acid precursors such as SO2, NOX and organic substances,which react with the mineral dust aerosol and change iron structure in particulate matter, thus increases the rate of dissolution of iron,so reduce the amount of CO2 in the atmosphere, so it indirectly controls the global climate change, hinder the "greenhouse effect". It follows that study mechanism of atmospheric iron dissolution has a vital significance for CO2 air-sea exchange and the global cycle.For a long time, little attention having been focused on anthropogenic sources when study atmospheric iron solubility as a result of iron from mineral aerosols is accounted for 95% of the global atmospheric circulation of iron while iron from anthropogenic source(mainly for fossil fuels and biomass burning emissions) accounts for only 5% of global atmospheric circulation of iron. But recently,the study found that the dissolution rate of iron with black carbon concentrations were positively correlated, so conjecture about anthropogenic source aerosols containing a large number of soluble iron, so we choose the dust containing iron (this experiment selects the goethite) to observe the role of organic matter playing on the dissolution of iron. Finally,a dust storm, for instance,study the rule of iron solubility from April 16, 2011 to May 15,2011 (containing a dust storm),and analyzes various factors affecting iron dissolution.The Major results got from this study are as follows:llron dissolution rate is related to the source of particulate matter, although both as a anthropogenic sources, due to the amount of iron particles, chemical bonds, particle size are different, the iron dissolution rate also has a big difference.Under dark and light conditions, the combustion source particles dissolved faster and to a greater extent relative to CL. Oil fly ash (FA) yielded the highest soluble iron as compared to the other samples, followed by biomass combustion particles BP) Corn, Coal fly ash (Coal FA) has the lowest dissolubility of iron.Mossbauer measurements and TEM analysis revealed that Fe in oil FA was commonly presented as nanosized Fe3O4 aggregates and Fe/S -rich particles. Highly labile source of Fe in corn BP could be originated from amorphous Fe form mixed internally with K-rich particles. However, Fe in coal FA was dominated by the more insoluble forms of both Fe-bearing alumino-silicate glass and Fe oxides.2.Organic acids have a positive impact on iron solubility of goethite.The results are as follows:oxalic acid> malonic> succinic acid> mesylate; there are the higher solubility of iron under light conditions, and the Fe (Ⅱ) accounts for more than 90% in content dissolution of iron. Compared with oxygen existing, under anaerobic conditions it is more conducive to the dissolution of iron;By analyzing single factor of promoting effect of iron solubility, the dissolution of iron in promoting effect:some of the organic ligand> illumination>anaerobic condition.3.During dust storms, there will be rich iron in plenty of dust particles,but during the sandstorm, iron solubility are very low; And the quantity of iron dissolution are positively related with (SO2 and NOx), and CO concentration, the correlation coefficients were 0.60,055; During the sandstorm, affected by the strong wind speed and relative humidity, SO2, NOx, CO and other pollutants had been diluted.and had a low concentration. So the dissolution of iron not only be affected by their chemical bonds, but also be influenced by external chemical substance. |
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