Atmospheric Nanoparticles - Environmental and Human Health Impacts of Nanotechnology - page 177

dominant class was that with elemental carbon internally mixed with calcium,
phosphate, sulfate and a lower abundance of organic carbon. The relative abun-
dance of organic carbon increased as the particle size increased (particles larger
than 50 nm aerodynamic diameter) and calcium and phosphate are likely to be from
lubricating oil additives. By number, the elemental carbon (combined with calcium,
PO 3− , SO 2− , OC) dominated the emissions of the lowest emitting vehicles; while
the highest emitting vehicles produced the highest number of particles, with the
dominant class being organic compounds including substituted monoaromatic com-
pounds and PAHs coupled with calcium and PO 3− . Considering both the work of
Sodeman et al. and that soot particles would be progressively removed by diesel
particle fi lters, it can be expected that the elemental carbon will soon no longer be
a tracer of diesel emissions.
Available research shows that the composition of NPs at urban locations is
strongly infl uenced by vehicular emissions. Fushimi et al. (2008) sampled NPs
(30-100 nm) with two low pressure impactors (Dekati) at a roadside site and at a
background site in Kawasaki, Japan (analyses using a thermal/optical carbon analy-
ser). The total carbon represented a signifi cant fraction of particles smaller than
100 nm and was more than 80% of the mass of 30- 60 nm (aerodynamic diameter)
particles. The smaller the particles (down to 30 nm), sampled closer to the vehicular
emissions, the larger the contribution of total carbon to the nanoparticle mass. At
the roadside site, the elemental carbon represented more than 70% of the total
carbon in the size fraction 30-60 nm and about 50% at the background site. At both
sites, the contribution of the elemental carbon was larger for particles ranging from
60 to 100 nm (about 80% of total carbon at the roadside site and 63% of total
carbon at the background site), in agreement with the contribution of soot mode
particles from diesel emissions. Note that a larger relative contribution of the
organic carbon is expected for particles smaller than 30 nm (not analysed at
Kawasaki). Fushimi et al. (2008) compared mass chromatograms of diesel exhaust
and roadside and urban background particles and concluded that the organic com-
position of roadside and urban background 30-60 nm particles was dominated by
lubricating oils (hopanes: fi ve - ring C 17 - C 35 hydrocarbons) and slightly affected by
unburned fuel (C 18 - C 26 n - alkanes).
Even though they make a much smaller contribution to the nanoparticle mass
(less than 1%), a number of metals have been found in NPs in concentrations that
may be relevant to health. Lin et al. (2005) made nanoparticle measurements with
a nano-MOUDI impactor beside a heavily-traffi cked road (10- 56 nm and 100 nm,

analyses by inductively coupled plasma-mass spectrometry). Respectively, 37%,
50%, 28%, 30%, 24%, 64%, 38% and 22% of the mass of silver, cadmiun, chro-
mium, nickel, lead, antimony, vanadium and zinc were present in the NP range.
Particles ranging from 10 to 56 nm contained more of the traffi c - related metals
(lead, cadmium, copper, zinc, barium and nickel) than particles of other sizes. Some
of them, considered as toxic (silver, cadmium and antimony), were found in much
larger proportions in particles ranging from 10 to 56 nm than in larger particles.
Around 95% of the total metal mass of NPs was thought to be from vehicular
emissions (exhaust and non - exhaust).

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