Development of a Wet-Chemical Method for the Speciation of Iron in Atmospheric Aerosols
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- 作者：Brian J. Majestic ; James J. Schauer ; Martin M. Shafer ; Jay R. Turner ; Philip M. Fine ; Manisha Singh ; and Constantinos Sioutas
- 刊名：Environmental Science & Technology
- 出版年：2006
- 出版时间：April 1, 2006
- 年：2006
- 卷：40
- 期：7
- 页码：2346 - 2351
- 全文大小：151K
- 年卷期：v.40,no.7(April 1, 2006)
- ISSN：1520-5851
文摘
The ability to quantify the chemical and physical forms oftransition metals in atmospheric particulate matter (PM)is essential in determining potential human health andecological effects. A method for the speciation of iron inatmospheric PM has been adapted which involves extractionin a well-defined solution followed by oxidation statespecific detection. The method was applied to a suite ofenvironmental aerosols. Ambient atmospheric aerosols in anurban area of St. Louis (the St. Louis-Midwest Supersite)were collected on Teflon substrates and were leachedin one of four different solutions: (1) >18.0 M
water; (2)140 
M NaCl solution; (3) pH = 7.4 NaHCO3 solution;and (4) pH = 4.3 acetate buffering system. Fe(II) wasdetermined directly using the Ferrozine method as adaptedto liquid waveguide spectrophotometry using a 1 m path-length cell. Fe(III) was determined similarly after reductionto Fe(II). It was found that, at low ionic strength, pH exerteda major influence on Fe(II) solubility with the greatestFe(II) concentration consistently found in the pH = 4.3acetate buffer. Soluble Fe(III) (as defined by a 0.2 m filter)varied little with extractant, which implies that most ofthe Fe(III) detected was colloidal. To characterize well-defined materials for future reference, NIST standardreference materials were also analyzed for soluble Fe(II)and Fe(III). For all SRMs tested, a maximum of 2.4% of thetotal iron (Urban Dust 1649a) was soluble in pH = 4.3acetate buffer. For calibration curves covering the rangesof 0.5-20 g/L Fe(II), excellent linearity was observed inall leaching solutions with R 2 values of >0.999. Co-locatedfilters were used to test the effect of storage time oniron oxidation state in the ambient particles as a functionof time. On two samples, an average Fe(II) decay rateof 0.89 and 0.57 ng Fe(II) g-1 PM day-1 was determinedfrom the slope of the regression, however this decrease wasdetermined not to be significant over 3 months (95%confidence). As an application of this method to mobilesource emissions, size-resolved PM10 samples were collectedat the inlet and outlet of the Caldecott Motor VehicleTunnel in northern California. These samples indicate thatthe coarse fraction (PM10-PM2.5) contains almost 50%of the total soluble Fe(II) in the aerosol.
water; (2)140 M NaCl solution; (3) pH = 7.4 NaHCO3 solution;and (4) pH = 4.3 acetate buffering system. Fe(II) wasdetermined directly using the Ferrozine method as adaptedto liquid waveguide spectrophotometry using a 1 m path-length cell. Fe(III) was determined similarly after reductionto Fe(II). It was found that, at low ionic strength, pH exerteda major influence on Fe(II) solubility with the greatestFe(II) concentration consistently found in the pH = 4.3acetate buffer. Soluble Fe(III) (as defined by a 0.2 m filter)varied little with extractant, which implies that most ofthe Fe(III) detected was colloidal. To characterize well-defined materials for future reference, NIST standardreference materials were also analyzed for soluble Fe(II)and Fe(III). For all SRMs tested, a maximum of 2.4% of thetotal iron (Urban Dust 1649a) was soluble in pH = 4.3acetate buffer. For calibration curves covering the rangesof 0.5-20 g/L Fe(II), excellent linearity was observed inall leaching solutions with R 2 values of >0.999. Co-locatedfilters were used to test the effect of storage time oniron oxidation state in the ambient particles as a functionof time. On two samples, an average Fe(II) decay rateof 0.89 and 0.57 ng Fe(II) g-1 PM day-1 was determinedfrom the slope of the regression, however this decrease wasdetermined not to be significant over 3 months (95%confidence). As an application of this method to mobilesource emissions, size-resolved PM10 samples were collectedat the inlet and outlet of the Caldecott Motor VehicleTunnel in northern California. These samples indicate thatthe coarse fraction (PM10-PM2.5) contains almost 50%of the total soluble Fe(II) in the aerosol.