192
5 Electrodynamics of Aqueous Media
because of the wall of the confining material. As the ionic atmosphere is broken,
there is no corresponding polarization, and, thus, results in the low dielectric constant i ≈ 2. However, the ionic atmosphere, destroyed by the boundary, prevents
the formation of an electrostatic restoring force, thus, the interfacial water layer possesses enhanced protonic conductivity. This interpretation of the enhanced protonic
conductivity of the interfacial water layer and the suppressed dielectric is in a very
good agreement with the experimental results discussed above.
In conclusion, there are many other interesting properties of interfacial water,
which, however, go beyond the current book. From the viewpoint of electrodynamics,
water in nanoconfinement exhibits properties of two types: that of bulk water and
interfacial water, which differ in their protonic conductivity. Near the interface, the
protons have higher mobility and are responsible for the enhanced conductivity in
an external electric field. The intrinsic protonic conductivity of interfacial water, σ i
= 0.02 S/cm, is five orders of magnitude larger than what is observed for bulk water.
This result provides a new insight into the fundamental properties of water and helps
to better understand the general electrodynamic effects in porous membranes and
other water-based systems in geological, biological, and engineered environments.
5.3 Atmospheric Electrodynamics and Aqueous Interfaces
The dielectric properties of water play an important role in atmospheric phenomena.
The microscopic charge separation mechanism in clouds is laterally responsible for
the weather on Earth. About 2,000 thunderstorms are active around the Earth right
now. They cover an area of about 5×10
5 km
2 , which is equal to the area of Spain.
Figure 5.10 shows the global electric circuit. Thunderstorms behave like a voltage
generator (or a battery) which is connected with the highly conducting ionosphere
and Earth by the barely conducting lower and middle atmosphere. The potential
difference between the Earth and the ionosphere is very high, and the strength of
the electric field depends on the altitude. The typical electric field strength near
the surface (in the environment where people spend most of their time) is about
120 V/m. The electric current flows back to Earth outside the thunderstorm region
(see green arrows). Although the global circuit involves many interesting objects to
study, the most exciting events appear in thunderstorms, which serve as an area of
charge separation, lightning, and precipitation. All these effects are determined by
the electrodynamic properties of water.
Let us consider the distribution of water in the atmosphere of Earth. The majority
of atmospheric water is located in its lowest layer, the troposphere, where water exists
as a gas, a liquid, or a solid. Atmospheric water vapor consists of molecular species
but also contains small charged clusters H 3 O
+
·(H 2 O) n and OH
−
·(H 2 O) n , where n ≈
4–12 with typical radii about 1 nm (nanodroplets), which exist even below saturation
point. Interestingly, electrical conductivity measurements [44] show that moist air
contains up to 10
15 ions per liter of air, or about 10 parts per billion (ppb), which is
high enough to affect the electrical properties of the atmosphere. If moist air becomes
5 Electrodynamics of Aqueous Media
because of the wall of the confining material. As the ionic atmosphere is broken,
there is no corresponding polarization, and, thus, results in the low dielectric constant i ≈ 2. However, the ionic atmosphere, destroyed by the boundary, prevents
the formation of an electrostatic restoring force, thus, the interfacial water layer possesses enhanced protonic conductivity. This interpretation of the enhanced protonic
conductivity of the interfacial water layer and the suppressed dielectric is in a very
good agreement with the experimental results discussed above.
In conclusion, there are many other interesting properties of interfacial water,
which, however, go beyond the current book. From the viewpoint of electrodynamics,
water in nanoconfinement exhibits properties of two types: that of bulk water and
interfacial water, which differ in their protonic conductivity. Near the interface, the
protons have higher mobility and are responsible for the enhanced conductivity in
an external electric field. The intrinsic protonic conductivity of interfacial water, σ i
= 0.02 S/cm, is five orders of magnitude larger than what is observed for bulk water.
This result provides a new insight into the fundamental properties of water and helps
to better understand the general electrodynamic effects in porous membranes and
other water-based systems in geological, biological, and engineered environments.
5.3 Atmospheric Electrodynamics and Aqueous Interfaces
The dielectric properties of water play an important role in atmospheric phenomena.
The microscopic charge separation mechanism in clouds is laterally responsible for
the weather on Earth. About 2,000 thunderstorms are active around the Earth right
now. They cover an area of about 5×10
5 km
2 , which is equal to the area of Spain.
Figure 5.10 shows the global electric circuit. Thunderstorms behave like a voltage
generator (or a battery) which is connected with the highly conducting ionosphere
and Earth by the barely conducting lower and middle atmosphere. The potential
difference between the Earth and the ionosphere is very high, and the strength of
the electric field depends on the altitude. The typical electric field strength near
the surface (in the environment where people spend most of their time) is about
120 V/m. The electric current flows back to Earth outside the thunderstorm region
(see green arrows). Although the global circuit involves many interesting objects to
study, the most exciting events appear in thunderstorms, which serve as an area of
charge separation, lightning, and precipitation. All these effects are determined by
the electrodynamic properties of water.
Let us consider the distribution of water in the atmosphere of Earth. The majority
of atmospheric water is located in its lowest layer, the troposphere, where water exists
as a gas, a liquid, or a solid. Atmospheric water vapor consists of molecular species
but also contains small charged clusters H 3 O
+
·(H 2 O) n and OH
−
·(H 2 O) n , where n ≈
4–12 with typical radii about 1 nm (nanodroplets), which exist even below saturation
point. Interestingly, electrical conductivity measurements [44] show that moist air
contains up to 10
15 ions per liter of air, or about 10 parts per billion (ppb), which is
high enough to affect the electrical properties of the atmosphere. If moist air becomes