Discrimination between individual dust and bioparticles using aerosol time-of-flight mass spectrometry

Figures & data

Table 1. Summary of dust and biological samples.

Sample	Name	Description	Study	ATOFMS
Ethiopian soil dust	EVSD	Soil from vegetated area	FIN-1	A-ATOFMS
Argentinian soil dust	ASD	Top soil from arable area	FIN-1	A-ATOFMS
Moroccan soil dust	MSD	Saharan desert dust	FIN-1	A-ATOFMS
Bachli soil dust	BSD	Glacial sediment, no vegetation	FIN-1	A-ATOFMS
K-Feldspar	KF	K-rich feldspar sample	FIN-1	A-ATOFMS
Illite NX	INX	Mineral dust standard	FIN-1	A-ATOFMS
Snomax	SX	Irradiated, desiccated, ground Ps	FIN-1	A-ATOFMS
P. syringae	Ps	Gram-negative bacteria	FIN-1	A-ATOFMS
P. fluorescens	Pf	Gram-negative bacteria	FIN-1	A-ATOFMS
C. reinhardtii	Cr	Freshwater microalgae	UC SAN DIEGO	LP-ATOFMS
S. dimorphus	Sd	Freshwater microalgae	UC SAN DIEGO	LP-ATOFMS
D. tertiolecta	Dt	Marine microalgae	UC SAN DIEGO	LP-ATOFMS
C. vulgaris	Cv	Freshwater microalgae	UC SAN DIEGO	LP-ATOFMS
P. purpera	Pp	Marine microalgae	UC SAN DIEGO	LP-ATOFMS
S. elongates	Se	Freshwater cyanobacteria	UC SAN DIEGO	LP-ATOFMS
Arizona test dust	ATD	Mineral dust standard	UC SAN DIEGO	Nozzle-ATOFMS

Figure 1. Distribution of relative ion signals for (a) ²⁶CN⁻, (b) ⁴²CNO⁻, (c) ⁷⁹PO₃⁻ from a variety of soil and mineral dust samples. Warmer colors indicate higher relative intensities. The ATD sample was analyzed with a different ATOFMS than the other samples, and thus the relative ion distributions are not directly comparable.

Figure 2. (a) Individual mass spectra for all cellular standards (red) and dust standards (black) plotted in ⁷⁹PO₃⁻/⁶³PO₂⁻ versus ²⁶CN⁻/⁴²CNO⁻ space. The blue box in the inset highlights a region of high overlap between the two particle types. Individual (b) ASD and (c) Ps mass spectra in ⁷⁹PO₃⁻/⁶³PO₂⁻ versus ²⁶CN⁻/⁴²CNO⁻ space. (d) Individual mass spectra for all Cell-type (red) and Dust-CW (black) particles plotted in ⁷⁹PO₃⁻/⁶³PO₂⁻ versus ²⁶CN⁻/⁴²CNO⁻ space. The red box in the inset highlights a region of high overlap between the two particle types. Individual (e) Dust-CW and (f) Cell-type mass spectra in ⁷⁹PO₃⁻/⁶³PO₂⁻ versus ²⁶CN⁻/⁴²CNO⁻ space. Warmer shades indicate higher total positive ion intensities.

Figure 3. Representative mass spectra for ASD (dust) with relatively low (a) and high (b) TPII. Representative mass spectra for Ps (cellular) with relatively low (c) and high (d) TPII.

Figure 4. For each dust sample analyzed, number fraction of mass spectra with relative ion signals for (a) ³⁹K⁺ > 0.25, (b) ²³Na⁺ > 0.01, (c) ²⁷Al⁺ > 0.05, (d) and ⁴⁸Ti⁺,⁶⁴TiO⁺ > 0.05.

Figure 5. Temporal profiles of (a) ATOFMS hourly counts for Dust (divided by 10, brown) and Cell-type (green), (b) WIBS concentrations for FP (red, scaled by 1/5), FP3 (blue), and FBAP (black), and (c) INP_-15 (L⁻¹). Correlation coefficients (r²) between INP_-15 and WIBS or ATOFMS particle types are shown in their respective colors.