Electrical mobility “when a charged particle is
exposed to an electric field, it will migrate at a
velocity that is determined by a balance
between the resulting electrostatic force and
aerodynamic drag that resists its motion. This
characteristic migration velocity is described
as the electrical mobility of the particle” [5].
Definition
This chapter will review the properties and behavior of nanoparticles suspended in air and measurement technologies for monitoring, characterizing,
and controlling them, to reduce their adverse
effects on the environment and human health.
A huge variety of particles is found in the atmosphere and built environment. Many environments include unwanted gases and particles that
can originate from primary emissions or from
secondary transformations in the atmosphere. In
addition there is significant processing within the
atmosphere including condensation and evaporation, multiple cycles of activation into a droplet
followed by dehydration, coagulation, photolysis,
and chemical reaction. Research has shown that
aerosol particles in the indoor and outdoor environments have significant detrimental impacts on
health. The word aerosol was introduced in
ca. 1920, in analogy to “hydrosol,” a liquid colloidal suspension of solid particles. Aerosols are
particulate matter, either liquid or solid or a combination, suspended in a gaseous medium. “Aerosol particle” refers to the suspended particles
themselves and can be divided into two groups,
primary and secondary, depending on their origin.
The former is generated by a source at the surface,
for example, abrasion or combustion. The latter is
often produced from gas-to-particle conversion or
agglomeration of primary aerosols. Primary and
secondary aerosol particles are characterized by
their shape, size, and chemical composition.
A spherical shape is often assumed, to simplify
calculations. Aerosol particles are commonly
classified by their “aerodynamic diameter,” that
is, the diameter of a spherical particle with the
same aerodynamic behavior. These classifications
divide particulate matter (PM) into coarse (PM 10 ),
fine (PM 2.5 ), and ultrafine (PM 0.1 ) fractions. The
subscripted number is a cutoff size, for example,
PM 2.5 is the total mass density of all aerosol
particles with an aerodynamic diameter less than
2.5 mm. Airborne nano-sized particles, i.e., nanoparticles, belong to the ultrafine class of particles;
they are often solid phase and have a dimension
less than 100 nm. Nanoparticles are commonly
emitted during combustion and are formed
through gas-to-particle conversion.
Introduction
There is a growing interest in airborne nanoparticles (NPs) because of their unique properties
for health and climate and the increasing development of nanomaterials. NPs can easily enter
the body and be distributed due to their small
size. In addition NPs cause serious environmental problems including changing the dynamics of
cloud formation, thereby contributing to drought
and global warming and impacting the radiation
balance of the Earth, as reported in the literature
[6]. Recent studies have reported the harmful
effects of NPs on human health including
mortality [7–9] and their association with pulmonary disease, cancer, incident wheezing, asthma,
lower spirometric values, and increased asthmarelated emergency in children [10, 11]. Toxicological studies show that NPs possess unique
physicochemical impacts due to their high
number concentration, ultrahigh reactivity, and
high surface area to mass ratio relative to other
particle size classes [7], resulting in elevated
bioavailability and toxicity [12]. Because of
their small size, nanoparticles can enter into the
bloodstream from the alveolar region of the
respiratory tract or through the skin. Consequences include cardiopulmonary effects, oxidative stress, and cancer [13].
Because of their weak light scattering ability
and extremely small size, NPs are often not visible. In addition they follow the streamlines of the
carrier gas making them more difficult to control
and measure than fine and coarse particles. Some
common and effective technologies for removing
coarse particles, such as centrifugation or settling,
86
Airborne Nanoparticles: Control and Detection
exposed to an electric field, it will migrate at a
velocity that is determined by a balance
between the resulting electrostatic force and
aerodynamic drag that resists its motion. This
characteristic migration velocity is described
as the electrical mobility of the particle” [5].
Definition
This chapter will review the properties and behavior of nanoparticles suspended in air and measurement technologies for monitoring, characterizing,
and controlling them, to reduce their adverse
effects on the environment and human health.
A huge variety of particles is found in the atmosphere and built environment. Many environments include unwanted gases and particles that
can originate from primary emissions or from
secondary transformations in the atmosphere. In
addition there is significant processing within the
atmosphere including condensation and evaporation, multiple cycles of activation into a droplet
followed by dehydration, coagulation, photolysis,
and chemical reaction. Research has shown that
aerosol particles in the indoor and outdoor environments have significant detrimental impacts on
health. The word aerosol was introduced in
ca. 1920, in analogy to “hydrosol,” a liquid colloidal suspension of solid particles. Aerosols are
particulate matter, either liquid or solid or a combination, suspended in a gaseous medium. “Aerosol particle” refers to the suspended particles
themselves and can be divided into two groups,
primary and secondary, depending on their origin.
The former is generated by a source at the surface,
for example, abrasion or combustion. The latter is
often produced from gas-to-particle conversion or
agglomeration of primary aerosols. Primary and
secondary aerosol particles are characterized by
their shape, size, and chemical composition.
A spherical shape is often assumed, to simplify
calculations. Aerosol particles are commonly
classified by their “aerodynamic diameter,” that
is, the diameter of a spherical particle with the
same aerodynamic behavior. These classifications
divide particulate matter (PM) into coarse (PM 10 ),
fine (PM 2.5 ), and ultrafine (PM 0.1 ) fractions. The
subscripted number is a cutoff size, for example,
PM 2.5 is the total mass density of all aerosol
particles with an aerodynamic diameter less than
2.5 mm. Airborne nano-sized particles, i.e., nanoparticles, belong to the ultrafine class of particles;
they are often solid phase and have a dimension
less than 100 nm. Nanoparticles are commonly
emitted during combustion and are formed
through gas-to-particle conversion.
Introduction
There is a growing interest in airborne nanoparticles (NPs) because of their unique properties
for health and climate and the increasing development of nanomaterials. NPs can easily enter
the body and be distributed due to their small
size. In addition NPs cause serious environmental problems including changing the dynamics of
cloud formation, thereby contributing to drought
and global warming and impacting the radiation
balance of the Earth, as reported in the literature
[6]. Recent studies have reported the harmful
effects of NPs on human health including
mortality [7–9] and their association with pulmonary disease, cancer, incident wheezing, asthma,
lower spirometric values, and increased asthmarelated emergency in children [10, 11]. Toxicological studies show that NPs possess unique
physicochemical impacts due to their high
number concentration, ultrahigh reactivity, and
high surface area to mass ratio relative to other
particle size classes [7], resulting in elevated
bioavailability and toxicity [12]. Because of
their small size, nanoparticles can enter into the
bloodstream from the alveolar region of the
respiratory tract or through the skin. Consequences include cardiopulmonary effects, oxidative stress, and cancer [13].
Because of their weak light scattering ability
and extremely small size, NPs are often not visible. In addition they follow the streamlines of the
carrier gas making them more difficult to control
and measure than fine and coarse particles. Some
common and effective technologies for removing
coarse particles, such as centrifugation or settling,
86
Airborne Nanoparticles: Control and Detection