Measurement of soluble and insoluble hexavalerst chromium in ambient particulate matter

摘要

Background: Hexavaient chromium (Cr(Ⅵ)), a pulmonary carcinogen, can present as both soluble and insoluble forms in environment, which may have different toxicities. It is thus important to separately quantify ambient Cr(Ⅵ) in both soluble and insoluble forms. Aims: To determine soluble and insoluble Cr(Ⅵ) in NIST 1648a (a reference urban particulate matter (PM)), ambient PM10 collected from 3 urban areas in NJ, i.e. Meadowlands, NJ Turnpike Exit 13 in Elizabeth and Rahway, and ambient PM10 collected from the suburban area in NJ, i.e. Piscataway. Methods: We developed a method to measure total Cr(Ⅵ) in ambient PM, which comprised collection of PM usinga Teflon filter, microwave extraction with 3% Na2CO3-2% NaOH, and detection with IC-UV (1,5-diphenylcarbazide colorimetry at 540 nm). The method detection limit was 0.33 ng/m3. Soluble Cr(Ⅵ) in ambient PM was measured by previously established method in our lab. Insoluble Cr(Ⅵ) was determined to be the difference between total Cr(Ⅵ) and soluble Cr(Ⅵ). Results: The soluble and total Cr(Ⅵ) in NIST 1648a were 1.75±0.24 mg/kg (N = 6, %CV = 14%) and 26.0+3.1 mg/kg (N = 4, %CV = 11.996). The concentrations (mean±SD) of ambient soluble Cr(Ⅵ) in Meadowlands, Elizabeth, Rahway and Piscataway were 0.30±0.16, 0.21±0.13, 0.3310.36 and 0.20±0.18 ng/m3 in the summer sampling period, and 0.11±0.04, 0.19±0.09, 0.14±0.07 and 0.03±0.01 ng/m3 in the winter sampling period. The concentrations of ambient total Cr(Ⅵ) in Meadowlands, Elizabeth, Rahway and Piscataway were 1.25±0.58,1.56±0.48, 0.99±0.76 and 0.86±0.50 ng/m3 in the summer sampling period and 1.32±0.56,1.41±0.56,1.05±0.36 and 0.94±0.49 ng/m3 in the winter sampling period. Conclusions: Soluble and insoluble Cr(Ⅵ) co-existed in both NIST 1648a and collected ambient PM10. The soluble Cr(Ⅵ) in ambient PM10 accounted for 14.3 - 42.7% of total Cr(Ⅵ) in the summer, greater than 4.2 -14.4% in the winter.