Chemicals can be transported through the air, groundwater, surface water, and soil. In the air, chemicals disperse and deposit based on their properties and wind patterns. Groundwater transports chemicals slowly through permeable soil. Surface water carries dissolved chemicals long distances while non-dissolved chemicals sink and concentrate near the source. Chemicals also leach through soil, with the rate affected by soil composition.

1. Transporting
Chemicals

2. Transporting Chemicals
1. Transport in Air
◦ 3 stages: release, dispersion,
deposition. Release of the chemical at
the source, dispersion or scattering of
the chemical in the atmosphere,
deposition of chemical in soil or water.
◦ direction and distance determined by
pollutants' properties, wind speed,
direction of the prevailing
winds, precipitation.

3. Transporting Chemicals
2. Transport in Groundwater
◦ Ground water: zone where all spaces are filled with water
◦ groundwater can move sideways and up/down.
◦ moves 1 m/year - 1 m/day.
◦ Moves slow so does not spread out and may become concentrated
over time.
◦ number and connection of pores in the soil affects how fast water moves
◦ permeable soil: is one with interconnected pores or spaces.
◦ Pollutants will be transported farther by groundwater that flows through
permeable soil.

4. Transporting Chemicals

5. Transporting Chemicals

6. Transporting Chemicals
3. Transport in Surface Water
◦ chemicals enter water from air, groundwater, runoff from agricultural
fields and industrial sites and outflow from storm sewers and sewage
treatment plants.
◦ substance that dissolve easily in water may be carried a long way and
dispersed.
◦ substance that does not easily dissolve, attaches to solids and do not
travel as far. - they sink and become concentrated closer to source - builds
up at the bottom of the lake/river.

7. Transporting Chemicals
4. Transport in the Soil
◦ leachate - liquid that dissolves and carries substances as it passes through
soil.
◦ composition of soil can affect the rate at which a liquid moves through it.
◦ packed clay - impermeable - fluids cannot move through it because soil
grains are packed too closely.
◦ organic material can slow the movement of chemicals. Hazardous
materials can be changed by chemical reactions that occur in the soil.
◦ Hydrocarbon - spread over wide area, does not dissolve, coats soil grains
and fills pores.

8. Transporting Chemicals
Dispersion: scatterings of a substance
away from its sources.
ie: scattering fertilizer.
Dilution: reducing concentration of a
pollutant by mixing the polluting
substance with large quantities of air
or water.
ie: drop of bleach into a tub of water.

9. Transporting Chemicals
Biodegradation: breakdown of materials by
organisms such as earthworms, bacteria, fungi, and
microorganisms. ("Bio" = living things "degrade" =
break up)
aerobic biodegradation: oxygen present for bacteria
to grow andreproduce.
anaerobic biodegradation: environment
without oxygen.
ie: anaerobic bacteria that removes chlorine
from PCB's, replaces it with H atoms. Affected
by temperature, soil moisture, pH, oxygen supply,
and nutrient availability.

10. Transporting Chemicals
Phytoremediation: technique that can be
used to reduce the concentration of
harmful chemicals in soil
or groundwater, using plants. ("phyto" =
plant "remediation" = clean up)
plants have been used to clean up
metals, hydrocarbons, solvents,
pesticides, radioactive materials,
explosives, and landfill leachates.

11. Transporting Chemicals
Photolysis: breakdown (lysis) of
compounds by the sunlight (photo).
ie: formation of ozone. Nitrogen dioxide in
the presence of light breaks down to form
nitrogen monoxide and oxygen atoms.
Oxygen atoms then combine with
oxygen to form ozone.