CHAPTER 16.docx

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Western University
Environmental Science
Environmental Science 1021F/G
Geoff Stewart

CHAPTER 16: WATER POLLUTION WHEN POLLUTANTS INFILTRATE WATER BODIES, THINGS GO AWRY -WATER POLLUTION: the addition of anything that might degrade the quality of the water -unprotected farm fields lose topsoil as well as farm fertilizers and other potential pollutants when heavy rains occur -garbage, oil, pesticides, fertilizers, and sediments wash into water with runoff -contaminants such as mercury, sulphur, and other air pollutants from fossil fuel combustion, enter lakes with rainwater -POINT SOURSE POLLUTION: pollution that can be traced back to discrete sources such as wastewater treatment plants or industrial sites – sewage treatment plant overflow, animal feedlot and waste lagoon, and industrial waste discharged into water -STORMWATER RUNOFF: water from precipitation that flows over the surface of the land -NON-POINT POLLUTION: runoff that enters the water from overland flow and can come from any area in the watershed – no single discharge point – open mines, cropland animal pasture, construction sites, industrial air pollution from smoke stacks falls back to Earth -stormwater runoff is an increasing contributor of nutrients and other chemicals, as more land surfaces that used to absorb water got paved over – these impermeable landscapes are more likely to be sources of problematic substances -fossil fuel combustion also releases sulphur and nitrogen pollution – which can lead to acid rain and lake acidification -calcium carbonates can neutralize acids -high latitude areas face an accumulation of toxic compounds that are transported in the upper atmosphere to the polar region – where they enter ecosystems (and food chains) as particles that fall to the ground NUTRIENT ENRICHMENT CAN LEAD TO OXYGEN DEPLETION -EUTROPHICATION: nutrient enrichment of water bodies, which typically leads to algal overgrowth and oxygen depletion, and which can occur natural or via human activities -CULTURAL EUTROPHICATION: eutrophication specifically caused by human activities (most eutrophication is caused by humans) -because nutrients – especially phosphorus and nitrogen – fuel plant growth, excess amounts triggers explosion of algae -pollution that adds nutrients to a body of water can throw its natural ecosystem out of balance – spurring the growth of some organisms and reordering the entire ecological community -algae blooms also contain one or more species of cyanobacteria (blue-green algae) – a type of photosynthetic bacteria -algae releases some oxygen into the water as a by-product of photosynthesis but thick layers of surface algae also block sunlight from reaching underwater plants – causing them to die -DISSOLVED OXYGEN (DO): the amount of oxygen in the water -HYPOXIA: a situation in which the level of oxygen in the water is inadequate to support life -an influx of nutrients or an algal bloom also cause an explosion of bacterial decomposers that consume these nutrients and dead algae – as part of this process, bacteria consume even more oxygen, which reduces DO levels even further THE SOURCE OF POLLUTION CAN BE HARD TO PINPOINT -POLLUTION STANDARDS: allowable levels of pollutant that can be released over a certain time period -SHARED RESPONSIBILITY: each level of government has the ability to create laws that protect the environment IDENTIFYING THE TYPES AND SOURCES OF THE POLLUTION IS THE FIRST STEP TO CLEANING UP OUR WATE
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