Environmental Studies

IDC3O3

Ms. Nguyen

* 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

*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

* 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