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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Biomagnetic Characterization of Air Pollution Particulates in Lahore, Pakistan. / Sheikh, H.A.; Maher, B.A.; Karloukovski, V et al.
In: Geochemistry, Geophysics, Geosystems, Vol. 23, No. 2, e2021GC010293, 28.02.2022.Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Biomagnetic Characterization of Air Pollution Particulates in Lahore, Pakistan
AU - Sheikh, H.A.
AU - Maher, B.A.
AU - Karloukovski, V
AU - Lampronti, G.I.
AU - Harrison, R. J.
PY - 2022/2/28
Y1 - 2022/2/28
N2 - We report the characterization of anthropogenic magnetic particulate matter (MPM) collected on leaves from roadside Callistemon (bottlebrush) trees from Lahore, Pakistan, and on known sources of traffic-related particulates to assess the potential of first-order reversal curve (FORC) diagrams to discriminate between different sources of anthropogenic magnetic particles. Magnetic measurements on leaves indicate the presence of surface-oxidized magnetite spanning the superparamagnetic (<30 nm) to single domain (∼30–70 nm) to vortex size range (∼70–700 nm). Fe-bearing particles are present both as discrete particles on the surface of larger mineral dust or carbonaceous particles and embedded within them, such that their aerodynamic sizes may be decoupled from their magnetic grain sizes. FORC diagrams of brake-pad residue specimens show a distinct combination of narrow central ridge, extending from 0 to 200 mT, and a low-coercivity, vertically spread signal, attributed to vortex and multi-vortex behavior of metallic Fe. This is in agreement with scanning electron microscopy results that show the presence of metallic as well as oxidized Fe. Exhaust-pipe residue samples display a more conventional “magnetite-like” signal comprising a lower coercivity central ridge (0–80 mT) and a tri-lobate signal attributed to vortex state and/or magnetostatic interactions. The FORC signatures of leaf samples combine aspects of both exhaust residue and brake-pad endmembers, suggesting that FORC fingerprints have the potential to identify and quantify the relative contributions from exhaust and non-exhaust (brake-wear) emissions. Such measurements may provide a cost-effective way to monitor the changing contribution; of future particulate emissions as the vehicle fleet is electrified over the coming years.
AB - We report the characterization of anthropogenic magnetic particulate matter (MPM) collected on leaves from roadside Callistemon (bottlebrush) trees from Lahore, Pakistan, and on known sources of traffic-related particulates to assess the potential of first-order reversal curve (FORC) diagrams to discriminate between different sources of anthropogenic magnetic particles. Magnetic measurements on leaves indicate the presence of surface-oxidized magnetite spanning the superparamagnetic (<30 nm) to single domain (∼30–70 nm) to vortex size range (∼70–700 nm). Fe-bearing particles are present both as discrete particles on the surface of larger mineral dust or carbonaceous particles and embedded within them, such that their aerodynamic sizes may be decoupled from their magnetic grain sizes. FORC diagrams of brake-pad residue specimens show a distinct combination of narrow central ridge, extending from 0 to 200 mT, and a low-coercivity, vertically spread signal, attributed to vortex and multi-vortex behavior of metallic Fe. This is in agreement with scanning electron microscopy results that show the presence of metallic as well as oxidized Fe. Exhaust-pipe residue samples display a more conventional “magnetite-like” signal comprising a lower coercivity central ridge (0–80 mT) and a tri-lobate signal attributed to vortex state and/or magnetostatic interactions. The FORC signatures of leaf samples combine aspects of both exhaust residue and brake-pad endmembers, suggesting that FORC fingerprints have the potential to identify and quantify the relative contributions from exhaust and non-exhaust (brake-wear) emissions. Such measurements may provide a cost-effective way to monitor the changing contribution; of future particulate emissions as the vehicle fleet is electrified over the coming years.
KW - environment
KW - magnetism
KW - air pollution
KW - particulate
KW - microscopy
KW - Lahore
U2 - 10.1029/2021gc010293
DO - 10.1029/2021gc010293
M3 - Journal article
VL - 23
JO - Geochemistry, Geophysics, Geosystems
JF - Geochemistry, Geophysics, Geosystems
SN - 1525-2027
IS - 2
M1 - e2021GC010293
ER -