Transcript IDC3O3 Intro.Hydropshere part 3 - MCI

Environmental Studies
IDC3O3
Ms. Nguyen
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* Amount of oxygen dissolved in water is a
good indicator of water quality and the
kinds of life it will support
* Oxygen with a water content above 6
parts per million (ppm) will support many
forms of aquatic life
* Less than 2ppm, oxygen will only support
worms, bacteria, fungi and other detritus
feeders and decomposers
*
* Oxygen is added to water by diffusion from the air,
especially when turbulence and mixing rates are high
* By photosynthesis of green plants, algae and cyanobacteria
(blue –green bacteria)
* Oxygen is removed from water by respiration and
chemical processes that consume oxygen
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*Organic waste such as sewage, paper pulp or food
waste rich in nutrients, especially nitrogen or
phosphorus
*Stimulates the growth of oxygen demanding
decomposing bacteria
*Biochemical oxygen demand (BOD)
*The affects of oxygen-demanding wastes on rivers
depends to a great extent on the volume, flow and
temperature of the river water
*
* Oxygen decline downstream is called the oxygen
sag
*
* Phosphates and nitrates are generally present in
very limited amount in unpolluted freshwater and
algae
*Limited factor is a necessary material that is in
short supply, and because of the lack of it, an
organism cannot reach its full potential growth)
* the excessive growth of algae and aquatic plants
due to added nutrients is called eutrophication
*As the organic matter decays, oxygen levels
decreases, and fish and other aquatic species die
*
* Creates Dead Zones
*E.g. seasonal hypoxia occurring at the outflows
of the Mississippi River.
*http://www.scivee.tv/node/14602
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* the sources of groundwater pollution span from
every facet of social, agricultural and industrial
activities
*Once groundwater pollution have occurred, it is
extremely difficult to treat
* Very slow and costly
* Difficult to know when all of the contaminated water
has been removed
*
*Agricultural products: seventy three different
pesticides have been detected in groundwater
in Canada and the United States
*Accidental spills or leaks of pesticides
*Animal-feeding operations
*Fertilizer applications
*Irrigation practices
*Underground storage tanks: in the past, a large
number of underground storage tanks containing
gasoline and other hazardous substance have leaked
* Four liters (1 gallon) of gasoline can contaminate the
water supply of a community of 50 000 people
*Landfills: 90% of landfills in North America have no
liners to stop leaks of underlying groundwater
* 96% have no system to collect the leachate that seeps
from the landfills
* 60% of landfills place no restrictions on the waste
accepted
* Many are not inspected
* Septic tanks: Poorly designed and inadequately
maintained septic systems leak nitrates, bacteria and
toxic cleaning agents
*
over 20 millions used in the United States and up to a
third have been found to be operating improperly
* Surface impoundments: over 225,000 pits, ponds and
lagoons used to store or treat waste
* 71% are unlined and only 1 percent use a plastic or other
synthetic, nonsoil liner
* 99% of these do not have leak detention systems
* 73% have no restriction on the waste placed in the
impoundment
* 60% are not inspected annually
* Located near groundwater supplies
* Other sources of groundwater contamination:
* mining waste
* salting for controlling road ice
* land application of treated wastewater
* open dumps
* cemeteries
* radioactive disposal sites
* urban runoff
* construction excavation
* fallout from atmosphere
* animal feedlots