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21 Cards in this Set
- Front
- Back
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Ground Water Contamination
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Often only detected once contamination is widespread. The extent of the problem is poorly quantified and it is the function of awareness. Once contaminated, an aquifer may be unusable for long periods of time. For example, 2 weeks to 10 000 years. E.g DDT is still found 35 years after having been banned
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Point-source pollution
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is a specific spot where a large quantity of pollutants are discharged.
e.g like sewage being dropped into the ocean and you can see it. |
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Non-point source
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is used to describe a diffuse source of pollutants. It is often consisting of small point-sources.
e.g If the farmers use pesticides you can’ really point out the exact spot where you see it get into the river, there are a bunch of farmers using pesticides and so you don’t really see a direct source but a bunch of little sources which affect the cleanliness of the river. |
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Potential sources of ground water contamination include:
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on-site septic systems, leaky tanks or pipelines containing petroleum products, leaks or spills of industrial chemicals at factories, municipal land fills, fertilizers dispersed on agricultural land, pesticides sprayed on agricultural land and forests contaminats in wet and dry atmposheric fallout
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Groundwater contaminates include :
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- pesticides
-insecticides such as DDT and paratherin -Herbicides such as triazine - fungicides - dry-cleaning agents -and solvents such as toluene and tricholorethylene (TCE) - heavy metals such as zinc, lead, arsenic, cadmium, chromium - Radioactive compounds such as uranium - gas and oil and other hydrocarbons such as benzene and toluene -fertilizers such as nitrates -and pathogens like e-coli |
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How do contaminants move?
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Contaminants move in soil as plumes which are bodies of contaminated ground water flowing from a specific source. Their movement is influenced by local ground water flow patterns, the density of the aquifer and the density of the contaminants.
The type of material in the aquifer also plans a role… is it sand? silt? clay? gravel? this influence the movementand also the types of contaminats? are they dense? light? do they have the same density of water??/ |
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What is the issue with ground well contamination?
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Ground water contamination is a severe problem in Bangladesh and the problem has its origin in an extensive program lead by Unicef in the 1970s to dig ARTESIAN wells to extend water supplies for agriculture. By the mid 1990s, the wells were found to be contaminated with arsenic which can cause skin disorders and cancer. Haitians started to show up in hospitals with signs of arsenic poisoning. Large-scale testing of the ground water was conducted by the British Geological Survery. 3524 wells were tested. Max level exposure to arsenic: 10 microgram/ L46% of wells that were tested were less than 150 M deep with concentrations exceeding 10 Mg/L. Based on these results, it estimated that 2.5 million wells are contaminated and that they are being used by 57 millions people. The source of the contamination was found to be of natural origin.
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How do you treat contaminated ground water?
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The best way to restrict pollutants into ground water is to prevent it from happening. De-polluting the ground water is much more expensive and complicated.
-Pumping ground water and treating it ( high cost)Filtering atrazine out of ground water in the MIDWEST United states costs up to 400 million dollars a year. Pumping water, treating it, and injecting it back takes a long time and it is impractical and the estimated costs of this in the united states are 1 trillion dollars. Restricting pollutants away from certain sights may shift the problem elsewhere |
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What is Pollution?
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human-caused addition of any material or heat energy in amounts that case undesired alterations to the environment. It is a byproduct to social and economic activities.
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What does pollution include?
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Pathogens,
organic wastes ( like sewage) chemical pollutants ( like pesticides) sediments nutrients ( like nitrates and phosphorous) Heat<--- has effects on indigenous populations of fish |
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A non-persistant pollutant is
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-can be broken down by chemical reactions or by bacteria into simple substances. The damage that it causes is reversible. It can lead to Eutrophication if the pollution load is high. For instance from domestic sewage or fertilizers.
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Eutrophication
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is the enrichment of an ecosystem with chemical nutrients, typically compounds containing nitrogen, phosphorus, or both. Eutrophication can be a natural process in lakes, occurring as they age through geological time.
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Persistent pollutants
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are substances that degrade very slowly or cannot be broken down at all. They may remain in the aquatic environment for many years. The damage that they cause is irreversible or can be repaired only over decades or centuries.
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What are some examples of persistent pollutants?
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Pesticdes such as DDT ( still used for mosquito control in some parts of the world)
Petroelum compounds Dioxins ( produced unintentionally at times from the industrial processes of combustion... like burning of municipal waste and medical waste) Polyaromatic Hydrocarbons Methyls Polychlorinated biphenyls ( useful in a variety of industrial applications e.g., in electrical transformers and large capacitors, as hydraulic and heat exchange fluids, and as additives to paints and lubricants) These compounds could have been created intentionally for agricultural, disease control or manufacturing/ industrial purposes. |
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What are some pathogens involved in water pollution?
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Salmonella bacteria
Cholera bacteria E-coli bacteria Parasite Cryptosporidium Hepatitis A virus Giardia parasite Round worm |
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Biochemical Oxygen Demand
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-is a measure of the amount of oxygen consumed by microbes as they break down organic matter within water samples.
- It is routinely measured as part of water quality testing. - Dead organic matter is added to streams and rivers from natural sources for example: dead leaves from forest agricultural runoff and urban sewage - 33% of all BOD in streams results from agricultural activities -Urban areas increase the BOD in streams |
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Assimilative Capacity
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-- Is used to describe that all streams have some capability to degrade organic waste.
--- Problems arise when the stream is overloaded with biochemical oxygen-demanding waste and exceeds this capacity. This overpowers the stream's natural cleaning function. --When the biochemical oxygen demand is high, dissolved oxygen content of the water becomes too low to support the life in the water. This is when the dissolved oxygen content of the water is less than 5mg per litre. Then a formal pollution alert may be issued. |
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Sediments
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Sediments can contribute to water pollution.
Sediments are rock and mineral fragments from gravel particles above 2mm in diameter to finer sand, silt, and clay and finer even particles. By volume and mass, sediments are the greatest water pollutants. |
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Why does sediment pollution pose such a threat?
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A) Threatens the water body its in and reduces the quality of the water
B)It's a sign of erosion C) It means soil is being depleted at the origin |
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When does sediment pollution cause a problem?
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A study North of Toronto in an expanding zone of population found that there is 100x more sediment released during construction than under normal urban conditions. There were also other pollutants IN the sediments.
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What are some strategies to deal with pollution ?
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Strategies to deal with pollution are:- 1)identifying the material causing the pollution 2) identifying the sources and parties responsible for the pollution
3) developing and implementing strategies for preventing pollutants to get into the environment. e.g through controls such as stormwater retention pumps 4) Developing and implementing alternative methods to reach societal needs 5) monitoring |
