title: Interconversion of chromium species during air sampling: effects of O3, NO2, SO2, particle matrices, temperature, and humidity.
abstract: The interconversion between Cr(VI), a pulmonary carcinogen, and Cr(III), an essential human nutrient, poses challenges to the measurement of Cr(VI) in airborne particles. Chamber and field tests were conducted to identify the factors affecting Cr(VI)-Cr(III) interconversion in the basic filter medium under typical sampling conditions. In the chamber tests, isotopically enriched (53)Cr(VI) and (50)Cr(III) were spiked on diesel particulate matter (DPM) and secondary organic aerosol (SOA) that were precollected on a basic MCE filter. The filter samples were then exposed to clean air or the air containing SO2 (50 and 160 ppb), 100 ppb O3, or 150 ppb NO2 for 24 h at 16.7 LPM flow rate at designated temperature (20 and 31 °C) and RH (40% and 70%) conditions. Exposure to 160 ppb SO2 had the greatest effect on (53)Cr(VI) reduction, with (53)Cr(VI) recovery of 31.7 ± 15.8% (DPM) and 42.0 ± 7.9% (SOA). DPM and SOA matrix induced (53)Cr(VI) reduction when exposed to clean air while reactive oxygen species in SOA could promote (50)Cr(III) oxidation. Deliquescence when RH increased from 40% to 70% led to conversion of Cr(III) in SOA, whereas oxidized organics in DPM and SOA enhanced hygroscopicity and thus facilitated Cr(VI) reduction. Field tests showed seasonal variation of Cr(VI)-Cr(III) interconversion during sampling. Correction of the interconversion using USEPA method 6800 is recommended to improve accuracy of ambient Cr(VI) measurements.
authors.affiliation: Department of Building Science, Tsinghua University, Beijing, 100084, China.
authors.forename: Lihui
authors.initials: L
authors.lastname: Huang
authors.forename: Zhihua Tina
authors.initials: ZT
authors.lastname: Fan
authors.forename: Chang Ho
authors.initials: CH
authors.lastname: Yu
authors.forename: Philip K
authors.initials: PK
authors.lastname: Hopke
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Lioy
authors.forename: Brian T
authors.initials: BT
authors.lastname: Buckley
authors.forename: Lin
authors.initials: L
authors.lastname: Lin
authors.forename: Yingjun
authors.initials: Y
authors.lastname: Ma
mesh_terms: D000388:Air; D002857:Chromium / Q000737:chemistry*; D006813:Humidity; D009585:Nitrogen Dioxide / Q000737:chemistry*; D010126:Ozone / Q000737:chemistry*; D013458:Sulfur Dioxide / Q000737:chemistry*; D013696:Temperature
chemical_list: D002857:Chromium; D013458:Sulfur Dioxide; D010126:Ozone; D009585:Nitrogen Dioxide
references.citation: J Toxicol Clin Toxicol. 1999;37(2):173-94
references.pmid: 10382554
references.citation: Environ Sci Technol. 2003 May 1;37(9):1811-21
references.pmid: 12775052
references.citation: Environ Sci Technol. 2011 Jan 1;45(1):276-82
references.pmid: 21121662
references.citation: Environ Sci Technol. 2007 Jul 15;41(14):4919-24
references.pmid: 17711203
references.citation: Am Ind Hyg Assoc J. 1992 Jan;53(1):57-68
references.pmid: 1590220
references.citation: J Environ Monit. 2009 Jan;11(1):153-9
references.pmid: 19137151
references.citation: Anal Chem. 2000 Oct 15;72(20):5047-54
references.pmid: 11055727
references.citation: Indoor Air. 2010 Aug;20(4):320-8
references.pmid: 20557377
references.citation: Environ Sci Technol. 1995 Jan 1;29(1):222-31
references.pmid: 22200223
references.citation: Environ Sci Technol. 1988 Aug 1;22(8):972-7
references.pmid: 22195722
references.citation: Environ Sci Technol. 2008 Oct 1;42(19):7260-6
references.pmid: 18939556
references.citation: J Occup Environ Hyg. 2004 Sep;1(9):613-9
references.pmid: 15559333
references.citation: J Environ Monit. 2008 Aug;10(8):966-74
references.pmid: 18688467
references.citation: Aerosol Sci Technol. 2009 Jan;43(1):60-70
references.pmid: 20046215
references.citation: Talanta. 2002 Jul 19;57(6):1143-53
references.pmid: 18968720
references.citation: J Hazard Mater. 2008 Oct 30;158(2-3):491-8
references.pmid: 18329168