Physical limnology WETA151 L6 Pollution transport

Physical limnologyWETA151

L6

Pollution transport

04/19/23 Timo Huttula

Contents• Pollution?• Modes of pollution

– point load and diffuse load– accidental and continuous

• (Turbulence, advection and dispersion)• Pollutant jets and near field• Large scale transport• Diffusion equation• Case studies


Pollution?

• Water pollution: ”any addition to fresh or sea water that disrupts biological processes or causes a health hazard.

• Common pollutants include nitrate, pesticides, and sewage (see sewage disposal), though a huge range of industrial contaminants, such as chemical byproducts and residues created in the manufacture of various goods, also enter water - legally, accidentally, and through illegal dumping.” Webster


Pollutting substances (Lillesand&Kipfer,

1999)• Organic wastes– consume oxygen through decomposition

• Infectious agents– transmit deceases

• Plant nutrients– promote nuisance growth of aquatic plants like algae and water weeds

• Synthetic organic chemicals – detergents and pesticides– toxic to aquatic life and potentially to humans

• Inorganic chemical or mineral substances– from mining, manufacturing processes, oil plant operations and

agricultural practices– interfere with natural stream purification, destroy aquatic life, cause

excessive hardness of water supplies, produce corrosive effects


Polluting substances..• Sediments

– fill streams, channels, harbours… – cause abrasion of hydroelectric power and pumping

equipment, affect fish and shellfish population by blanketing fish nests and spawn as well their food supplies

• Radioactive pollution – resulting from the mining and processing of radioactive ores,

fallout of nuclear test…

• Water temperature increases– by cooling waters– harmful effects on fish and aquatic life– reduce the capacity of the receiving water to assimilate

wastes


Modes of pollution entrainment: point source

•Ex: Municipal sewage plant, Industrial sewage plan, River mouth


Modes of pollution entrainment: diffuse load

•Large and dispersed entrainment area:

•Directly to lake with run off (agriculture, summer cottages, piers…) , Via small rivers and creeks around the lake, Atmospheric pollution directly to lake surface


Modes of pollution entrainment: continuous

• Treated waste water from treatment plants• In Finland the carrying capacity of recipient

water is assessed before the permit is given• The amount and content is controlled by actor

and occasionally by Environmental Administration

• Loading amount (=volume*concentration) is reported and can be traced


Modes of pollution entrainment: accidental

• From industry– purification chemicals– over filling of tanks

• From treatment plants– Sjas-river catastrophe in Russia– Sahalahti

• From traffic– cyanide lorry on the shore of Lake Issyk-Kul– oil spillage on Baltic


Turbulence, advection and

dispersion•Laminar flow:

– laminated structure

– small velocities

•Turbulent flow:– total velocity of water = mean

velocity + chaotically fluctuating part of the flow

– for each velocity component: f=f(mean)+f’

– most environmental flow outside micro scale are turbulent


Importance of turbulence

• Primary cause of mixing in lakes, molecular diffusion is about 9 orders of magnitude less than turbulent diffusion

• Turbulence intensity is dependent on wind velocity, water density and currents in the lake

• Turbulence spectrum consists of eddies of different sizes

• Largest eddies are wind driven currents• The smallest eddies are dissipated by viscosity

of the water


•3.1.a:

•-no flow in ambient water and incoming fluid lighter than ambient

•-momentum jet

•-rising plume

•-level of equal density horizontal spreading

•3.1.b:

•-main flow present

•-like 3.1.a but at the level of equal density advection downstream

•3.1.c:

•-phases in the entrainment of a momentum jet

•-development range

•-fully developed flow


Large scale (> 100 m and >1h)

• Processes there determine the fate and transport of pollutant

• Can be studied by map survey, measurements or numerical flow model application

• Data on wind and river discharge are needed• Data on pollutant

– temperature ?– density ?– aggregation ?– volatile ?


Diffusion equation: simplest solution of transport

DtutxeDt

Mtxc 4

4,

•Where: M=released mass (kg), u=velocity of ambient flow (=advection) (m/s) , D=turbulent dispersion coefficient (m2/s), t=time (s), x=spatial coordinate (m)

•Tracer concentration in (M=D=1 and u=0) at time t= 1 and 10 after release, which happened at origin.

•Distribution is shown with one standard deviation . It grows as a function of time2


Lake Jyväsjärvi flow and particle transport model

• Two dimensional simulation model for water currents

• Vertical integration = mean velocity over the computational cell

• Driving forces: wind, tributary flow• Resisting forces: internal and bottom friction• Bouyant particles (floating with currents)• Femflow2d.exe


STOCKHOLM

HELSINKI ST. PETERSBURG

Pärnu Tartu

Lake Võrtsjärv

NarvaTALLINN

RIGA

•Lake Võrtsjärv

•Present state and future fate of Lake Võrtsjärv. Results of Finnish-

Estonian joint project in 1993-1997 (Huttula and Nõges, eds., 1998)

•Master plan for restoration and protection of Lake Võrtsjärv (Bilaletdin and Arvonen, 2000)

04/19/23 Timo HuttulaName Location Area Mean depth Max depth ToTP ToTNLake Vörtsjärv Estonia 270 2,8 6 54 1600

•Lake Võrtsjärv


•Simulated flowfields of Lake Võrtsjärv with particle tracking applications. •Wind: (a) - 4 m/s S , (b) - 4 m/s W , (c) - 4 m/s N , (d) - 4 m/s E.

•Simulation time = 5 days, dispersion coefficient = 0.2 m2/s.

•Source for particles is in the deepest part of the lake.



Oil spillage on Baltic

• Ship traffic is increasing• Many companies try to

minimize harbour payments by leaking spillage water to sea

• Thin oil cover, floating on surface and transported by wind and currents

• International collaboration for tracking the oil floats– control from air– using mathematical models

Other examples

• Päijänne Keljonlahti-Poronselkä• Onkivesi

– Dem1– Dem2

• Kokemäenjoki


Documents

Physical limnology WETA151 L6 Pollution transport