water pollution case studies
TRANSCRIPT
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WATER POLLUTION CASE STUDIESChesapeake Bay and Bangladesh
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CHESAPEAKE BAY
Largest estuary in US 64,000 sq.-mi watershed,
with human population of 15 million
Important for fisheries, recreation, shipping
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NUTRIENTS IN THE BAY: MAJOR POLLUTION PROBLEM
Nitrogen (primarily sewage and atmospheric deposition)
Phosphorus (primarily sewage) Oxygen-demanding wastes
Organic matter that is a substrate for aerobic decomposition
Sources are both point sources and non-point sources.
All these add to the eutrophication of the Bay, and the ultimate result: decreased oxygen Eutrophication: ecosystem change due to increased
nutrients; can be cultural or natural
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NITROGEN TRENDS
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OXYGEN
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SEDIMENTS IN THE BAY
Top water pollutant in terms of weight. Problems caused by sediment:
Smother benthic (bottom-dwelling) organisms Decrease light transmission therefore reduce
benthic photosynthesis Carry toxins and nutrients
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SEDIMENT TRENDS
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TOXIC CONTAMINANTS (METALS, SYNTHETIC ORGANIC COMPOUNDS)
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Solid red: region of concern; probable adverse impactDashed red: area of emphasis, potential adverse impact Dashed lines: low probablity of impactDotted: little information
From: http://www.mdsg.umd.edu/CB/toxics/map.html
Toxic Impacts
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From: http://www.mdsg.umd.edu/CB/toxics/map.html
Toxic Impacts: Potomac
Solid red: region of concern; probable adverse impactDashed red: area of emphasis, potential adverse impact Dashed lines: low probablity of impactDotted: little information
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SUSQUEHANNA: PREVENTION OF A PROBLEM
Cooling towers move heat to the air rather than to the River and Bay
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BANGLADESH
Surface water unsafe to drink; large amount mortality from of waterborne disease.
1970s: UN Health and Development Agencies dropped 10 million deep tube wells to provide ‘safe’ drinking water.
Now 35-77 million Bangladeshis (up to half the population) drink water contaminated with arsenic at concentrations greater than 50 ug/l
WHO standards: 10 ug/lArsensic causes: skin lesions (early signs of
poisoning) skin cancer, bladder, kidney, lung cancer… (takes 7-10 years to appear)
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ARSENIC POISONING: THE VISIBLE EFFECTS
Lesions on hands, feet, chest or head
Lesions can become cancerous:
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ARSENIC MITIGATION Monitoring wells: which are safe?
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ARSENIC MITIGATION Boy pumps
from well marked with green paint: “safe to drink”
Arsenic filter is possible on contaminated wells: $1500 per well.