Volume 14, No. 7, December 2014, Pages 1939-1949 PDF(652 KB)
Measurement of Soluble and Total Hexavalent Chromium in the Ambient Airborne Particles in New Jersey
Lihui Huang1,2, Chang Ho Yu3, Philip K. Hopke4, Paul J. Lioy3, Brian T. Buckley3, Jin Young Shin5, Zhihua (Tina) Fan3
1 Department of Building Science, Tsinghua University, Beijing, 100084, China
2 Key Laboratory of Eco Planning & Green Building, Ministry of Education (Tsinghua University), China
3 Rutgers Environmental and Occupational Health Science Institute, Piscataway, New Jersey 08854, USA
4 Center for Air Resource Engineering and Science, Clarkson University, Potsdam, New York 13699, USA
5 Meadowlands Environmental Research Institute, Lyndhurst, New Jersey, USA
- Ambient Cr(VI) may have soluble and insoluble forms with differential toxicity.
- A method was developed and evaluated to measure ambient total Cr(VI).
- The method detection limit: 0.33 ng/m3.
- The total Cr(VI) recoveries for two reference materials: 119.5 ± 10.4%, 106.3 ± 16.7%.
- Soluble/total ambient Cr(VI) in New Jersey: 14.3–42.7% (summer), 4.2–14.4% (winter).
Hexavalent chromium (Cr(VI)) in ambient airborne particulate matter (PM) is a known pulmonary carcinogen and may have both soluble and insoluble forms. The sum of the two forms is defined as total Cr(VI). Currently, there were no methods suitable for large-scale monitoring of total Cr(VI) in ambient PM. This study developed a method to measure total Cr(VI) in ambient PM. This method includes PM collection using a Teflon filter, microwave extraction with 3% Na2CO3-2% NaOH at 95°C for 60 minutes, and Cr(VI) analysis by 1,5-diphenylcarbazide colorimetry at 540 nm. The recoveries of total Cr(VI) were 119.5 ± 10.4% and 106.3 ± 16.7% for the Cr(VI)-certified reference materials, SQC 012 and SRM 2700, respectively. Total Cr(VI) in the reference urban PM (NIST 1648a) was 26.0 ± 3.1 mg/kg (%CV = 11.9%) determined by this method. The method detection limit was 0.33 ng/m3. This method and the one previously developed to measure ambient Cr(VI), which is soluble in pH ~9.0 aqueous solution, were applied to measure Cr(VI) in ambient PM10 collected from three urban areas and one suburban area in New Jersey. The total Cr(VI) concentrations were 1.05–1.41 ng/m3 in the winter and 0.99–1.56 ng/m3 in the summer. The soluble Cr(VI) concentrations were 0.03–0.19 ng/m3 in the winter and 0.12–0.37 ng/m3 in the summer. The summer mean ratios of soluble to total Cr(VI) were 14.3–43.7%, significantly higher than 4.2–14.4% in the winter. The winter concentrations of soluble and total Cr(VI) in the suburban area were significantly lower than in the three urban areas. The results suggested that formation of Cr(VI) via atmospheric chemistry may contribute to the higher soluble Cr(VI) concentrations in the summer.
Hexavalent chromium; Ambient particulate matter; Microwave extraction; IC-UV; ICPMS.