Post on 04-Jan-2016
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