Unit C Section 3.1 Flashcards
the three stages of transport of substances in the air:
- Release of the chemical at the source
- Dispersion of the chemical in the atmosphere (the chemicals scatter in various directions)
- Deposition of the chemical in soil or water
What are the factors that determine the direction and distance that airborne chemicals travel?
- pollutant’s properties,
- the wind speed,
- the direction of the prevailing winds.
EX. in Alberta, prevailing winds are from the west, so airborne substances are carried eastward.
What factors affect the distribution of airborne chemicals?
- wind (distribution of airborne pollutants may be limited by lack of wind)
- Precipitation (An airborne pollutant will be deposited closer to its source if it is carried to the ground by rain or snow.)
is it possible to find the source of airborne pollutants?
- The source of a chemical that has traveled thousands of kilometers is usually impossible to identify.
- Often chemicals travel across borders, so the deposition of airborne pollutants is an international problem.
First zone for the water that soaks into the soil:
- Water that soaks into soil moves first into a zone near the surface.
- Here the spaces between the soil grains contain both air and water.
Second zone for the water that soaks into the soil:
- As the water moves deeper, it enters the next zone where all the spaces are filled with water
- This water is called groundwater
What is groundwater:
all the spaces in the soil are filled with water.
- Groundwater can move sideways, up, and down.
- It can move as slowly as 1 m per year or as quickly as 1 m per day
What is a water table:
The top of the groundwater zone is called the water table
Why is groundwater not always safe for drinking, agricultural purposes, or industrial use?
- Because of groundwater’s slow movement, contaminants such as lead cannot be quickly dispersed.
- They may become concentrated over time.
The factor that affects the movement of groundwater:
-number and connection of pores in the soil
What are pores?
Pores are the tiny spaces between soil grains.
What is permeable soil?
- A permeable soil is one with connected pores.
- Lets water move through easily
- Soil grain are not packed too tightly
(Sand)
How are pollutants transported in permeable soil?
-Pollutants will be transported farther by groundwater that flows through permeable soils.
The substances that contaminate groundwater occur:
(Contaminants)
1.Minerals in rocks and soil-Iron, calcium, selenium
2.Organic substances occurring naturally or produced by humans-Pesticides, solvents
3.Substances leached from landfill sites and mine waste-Heavy metals
4.Substances that leak from underground storage tanks and pipelines-Gasoline, natural gas, oil
5.Inorganic substances-Salt,fertilizers, acidic deposition
6.Micro-organisms from improperly designed or
maintained septic tanks and sewage treatment ponds,
and improper storage and disposal of livestock wastes
7.Household chemicals-Nitrates, phosphorus compounds, detergents, chlorine compounds
Sources that hazardous chemicals can enter surface water systems:
air,
groundwater,
runoff from agricultural fields and industrial sites, outflow from storm sewers
sewage treatment plants.
Why can chemicals in surface water systems be a problem?
-Chemicals from these sources may not be a
the problem if their concentrations are very low.
If they are dispersed or carried away.
-they may become a problem if the chemicals do not disperse, and the concentrations increase locally
The landing of water can do four things:
- some evaporate
- some soaks into the soil and is taken up by plants
- some runs onto the street or into a stream
- some soaks through the soil and moves downward.
What is leachate?
As this water moves in the soil, it dissolves substances in the soil and carries them along. Such a liquid is called leachate.
What is impermeable soil?
- the soil in which water does not moves more easily
- There are no connected pores.
- soil grains are packed too closely
(clay)
What is the purpose of clay liners in sanitary landfills:
The clay prevents leachate containing harmful chemicals from moving into the soil and contaminating groundwater
What can slow down the movement of the chemicals in leachate?
- Organic material such as decayed leaves
- This can slow down the movement because they can be absorbed by the organic material.
-Sometimes the chemicals become attached to the soil particles, and their movement is slowed or stopped.
How can hazardous substances be changed by chemical reactions in the soil?
For example, acids can be neutralized by substances
such as calcium carbonate (limestone) in soil.
