Sinkage and Stokes law of atmospheric pollutants

1. Bangabandhu Sheikh Mujibur Rahman
Science & Technology University
Tohmina Khatun Md. Mottakin
ID: 20140107021 Lecturer
Dept. of ACCE Dept. of ACCE
BSMRSTU BSNRSTU
My Presentation Topic is
Sinkage and Stokes law of atmospheric pollutants

2. Sinkage of natural and anthropogenic pollutants
Sink is a medium which is capable of retaining and interacting with
a long-lived pollutants.
During natural processes the atmosphere interacts continuously
with other spheres (e.g. biosphere, lithosphere, hydrosphere), and
these spheres can be sinks of atmospheric pollutants.
 Ocean surface : Ocean are the sink for gases those dispersed in the
troposphere and absorbed or diffuse to the ocean surface.
 Vegetation :Plants have the ability to absorb atmospheric gases
without metabolism.
 Upper layer of soil: Soil micro-organism are the important sink for
CO.
 Lime stone acts as the sink for atmospheric gases.
CaCO3+H2SO4=CaSO4+H2O+CO2.

3. Stokes’ Law
 The forces acting on a spherical particle settling through a
fluid under the influence of gravity.
Fig: The forces acting on a particle in a fluid

4.  Writing Newton’s law for the particle, we obtain
 The three terms on the right represent, respectively, the
gravity, buoyant, and drag forces acting on the particle.
 The drag (or air resistance) forces increase with increasing
speed and are zero for zero speed.
 At this terminal settling velocity, the sum of the forces acting
is zero, so the particle continues to move at a constant
velocity

5. continuous
 To find this velocity, we set the acceleration to zero in Eq. (1)
and find,
 To find the velocity, we need the relation between Fd and the
velocity.
 Stokes worked this out mathematically for a set of
assumptions that are quite good for most of the problems in
this course, finding
 If we substitute Eq. (3) into Eq. (2) and solve for v, we find
which is commonly referred to Stokes’ law.