Development and evaluation of a novel monitor for online measurement of iron, manganese, and chromium in ambient particulate matter (PM)

Dongbin Wang; Mohammad H Sowlat; Martin M Shafer; James J Schauer; Constantinos Sioutas

doi:10.1016/j.scitotenv.2016.04.164

Development and evaluation of a novel monitor for online measurement of iron, manganese, and chromium in ambient particulate matter (PM)

Sci Total Environ. 2016 Sep 15:565:123-131. doi: 10.1016/j.scitotenv.2016.04.164. Epub 2016 May 7.

Authors

Dongbin Wang¹, Mohammad H Sowlat¹, Martin M Shafer², James J Schauer², Constantinos Sioutas³

Affiliations

¹ Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA, USA.
² Environmental Chemistry and Technology Program, University of Wisconsin-Madison, Madison, WI, USA; Wisconsin State Laboratory of Hygiene, University of Wisconsin-Madison, Madison, WI, USA.
³ Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA, USA. Electronic address: sioutas@usc.edu.

PMID: 27161133
DOI: 10.1016/j.scitotenv.2016.04.164

Abstract

A prototype atmospheric aerosol monitor was developed for online measurement of three toxicologically relevant redox-active metals (Fe, Mn, and Cr) in ambient fine particulate matter (PM2.5). The monitor has the unique ability to quantify these metals in specific chemical oxidation states in addition to both their total and water-soluble fractions in the ambient PM2.5. This information is critical for advancing our understanding of mechanisms of PM-induced toxicity as well as chemical processing of aerosol in the atmosphere. The metal monitor utilizes a high flow rate aerosol-into-liquid collector to collect ambient PM2.5 directly as concentrated aqueous slurry samples. The concentrations of target metals in the collected slurries are subsequently measured in a aerosol-into-liquid collector, micro volume flow cell (MVFC) using spectrophotometry to quantify the light absorption of colored complexes resulting from the reaction between the target metals and added analytical reagents. Our experimental evaluation indicated that, overall, this novel monitor can achieve accurate and reliable measurements over long sampling periods (i.e. at least several weeks). The online measurements for all three target elements were in good agreement (i.e., with slopes of the linear regression lines ranging between 0.90 and 1.07, and R(2) values between 0.76 and 0.95) with time-integrated filter samples collected in parallel and analyzed by magnetic sector inductively coupled plasma mass spectrometry (SF-ICPMS). Moreover, this metal monitor can provide semi-continuous measurements (i.e., every 2h) for at least 5 consecutive days without obvious shortcomings in its field operation. The online monitor measured total concentrations of Fe that ranged between 4.8 and 65.6ng/m(3), for Mn from below detection limit to 10.0ng/m(3), and for Cr from below detection limit to 6.6ng/m(3), respectively. Our results indicate that the developed metal monitor is a promising technology for online measurement and chemical speciation of important redox-active metals in ambient PM2.5.

Keywords: Aerosol-into-liquid collector; Cr; Fe; Mn; Online metal measurement; Spectrophotometry.

Publication types

Evaluation Study

MeSH terms

Aerosols / analysis*
Air Pollutants / analysis*
Chromium / analysis*
Environmental Monitoring / instrumentation
Environmental Monitoring / methods
Internet*
Iron / analysis*
Manganese / analysis*
Particulate Matter / analysis*
Spectrophotometry / instrumentation
Spectrophotometry / methods

Substances

Aerosols
Air Pollutants
Particulate Matter
Chromium
Manganese
Iron