Selection of metric for indoor‐outdoor source apportionment of metals in PM2.5: mg/kg versus ng/m3. (21st August 2021)

• Record Type: Journal Article
• Authors: Rasmussen, Pat E.; Levesque, Christine; Butler, Owen; Chénier, Marc; Gardner, H. David
• Is Part Of: Indoor air. Volume 32:Number 1(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-21
• Subjects: metal exposure -- buoyancy correction -- spurious correlation -- sulfur infiltration factor -- uncertainty; Indoor air pollution -- Periodicals; Sick building syndrome -- Periodicals; Ventilation -- Periodicals; 613.5
• DOI: 10.1111/ina.12924
• Languages: English
• ISSNs: 0905-6947

Abstract

Abstract: Trends in the elemental composition of fine particulate matter (PM2.5 ) collected from indoor, outdoor, and personal microenvironments were investigated using two metrics: ng/m 3 and mg/kg. Pearson correlations that were positive using one metric commonly disappeared or flipped to become negative when the other metric was applied to the same dataset. For example, the correlation between Mo and S in the outdoor microenvironment was positive using ng/m 3 ( p < 0.05) but negative using mg/kg ( p < 0.05). In general, elemental concentrations (mg/kg) within PM2.5 decreased significantly ( p < 0.05) as PM2.5 concentrations (µg/m 3 ) increased—a dilution effect that was observed in all microenvironments and seasons. An exception was S: in the outdoor microenvironment, the correlation between wt% S and PM2.5 flipped from negative in the winter ( p < 0.01) to positive ( p < 0.01) in the summer, whereas in the indoor microenvironment, this correlation was negative year‐round ( p < 0.05). Correlation analyses using mg/kg indicated that elemental associations may arise from Fe‐Mn oxyhydroxide sorption processes that occur as particles age, with or without the presence of a common anthropogenic source. Application of mass‐normalized concentration metrics (mg/kg or wt%), enabled by careful gravimetric analysis, revealed new evidence of the importance of indoor sources of elements in PM2.5 .