ENSP101Chapter 18 - Water Pollution18.1 Water Pollution- While pollution from factory pipes has been vastly reduced in the past 40 years, erosion from farm fields, construction sites, and streets has gotten worse since 1972o Airborne mercury, sulfur, and other substances are increasingly contaminating lakes and wetlandso Concentrated livestock production and agricultural runoff, threaten underground water a well as surface water systemso Increasing industrialization in developing countries has led to widespread water pollution in impoverished regions with little environmental regulation- Water pollution is anything that degrades water qualityo Factories, power plants, sewage treatment plants, underground coal mines, and oil wells are classified as point sources because they discharge pollution from specific locations, such as drain pipes, ditches, or sewer outfallso Nonpoint sources of water pollution are scattered or diffuse, having no specific location where they discharge into a particular body of water Nonpoint sources include runoff from farm fields and feedlots, golf courses, lawns and gardens, construction sites, logging areas, roads, streets, and parking lots Atmospheric deposition – sedimentation of solids, liquids, or gaseous materials from the air- The nearest sources for many of these chemicals are sometimes thousands of kilometers away- Amounts of these pollutants can be quite large18.2 Types and Effects of Water Pollutants- The most serious water pollutants in terms of human health worldwide are pathogenic organismso The main source of these pathogens is from untreated or improperly treated human wasteso Animal wastes from feedlots or fields near waterways and food processing factories with inadequate waste treatment facilities also are sources of disease-causing organismso Coliform bacteria – bacteria that live in the intestines of humans and other animals; used as a measure of the presence of feces in water or soil Most common  E.coli- Bacteria are detected by measuring oxygen levelso Biochemical oxygen demand (BOD) – a standard test for measuring the amount of dissolved oxygen utilized by aquatic microorganismso An alternative method, called the chemical oxygen demand (COD), uses a strong oxidizing agent to completely break down all organic matter in a water sampleo A third method of assaying pollution levels is to measure dissolved oxygen (DO) content directly, using an oxygen electrode- The effects of oxygen-demanding wastes on rivers depends to a great extent on the volume, flow, and temperature of the river watero The oxygen decline downstream is called the oxygen sag- Water clarity is affected by sediments, chemicals, and the abundance of plankton organisms, and is a useful measure of water quality and water pollution - Oligotrophic – condition of rivers and lakes that have clean water and low biological productivity; are usually clear, cold, infertile headwater lakes and streams- Eutrophic – rivers and lakes rich in organisms and organic materialo Some amount of eutrophication is a normal part of successional changes in most lakeso Eutrophication often results from nutrient enrichment sewage, fertilizer runoff, even decomposing leaves in street gutters can produce a human-caused increase in biological productivity called cultural eutrophicationo Cultural eutrophication can also result from higher temperatures, more sunlight reaching the water surface, or a number of other changeso Eutrophication has undesirable results  “blooms” of algae, increase in bacterial populations, and in extreme cases plants and algae die and decomposers deplete oxygen in the water (collapse of the aquatic ecosystem can result)- Eutrophication can cause toxic tides and “dead zones”o Red tide – a population explosion or blood of minute, single-celled marine organisms called dinoflagellates. Billions of these cells can accumulate in protected bays where the toxins they contain can poison other marine lifeo Have become increasingly common in slow-moving rivers, brackish lagoons, estuaries, and bays, as well as near-shore ocean waters where nutrients and wastes wash down our riverso Extensive “dead zones” often form where rivers dump nutrients into estuaries and shallow seaso It appears that fish and other marine species die in these hypoxic zones not only because oxygen is depleted, but also because of high concentrations of harmful organisms including toxic algae, pathogenic fungi, parasitic protists, and other predators- In many areas, toxic, inorganic chemicals introduced into water as a result of humanactivities have become the most serious form of water pollution- Because metals are highly persistent, they can accumulate in food webs and have a cumulative effect in top predators – including humanso Most widespread toxic metal contamination  Mercury released from coal-burning power plants Problem: mercury in fisho Mine drainage and leaching of mining wastes are serious sources of metal pollution in water- Some soils contain high concentrations of soluble salts, including toxic selenium andarsenico Irrigation and drainage of desert soils can mobilize these materials on a larger scale and result in serious pollution problemso Salts, such as sodium chlorine (table salt), that are nontoxic at low concentrations also can be mobilized by irrigation and concentrated by evaporation, reaching levels that are toxic for many plants and animals- Acids are released as by-products of industrial processes, such as leather tanning, metal smelting and plating, petroleum distillation, and organic chemical synthesiso Coal mining is an especially important source of acid water pollutiono Sulfur compounds in coal react with oxygen and water to make sulfuric acido Coal and oil combustion also leads to formation of atmospheric sulfuric and nitric acidso If acidification is severe enough, aquatic life is limited to a few resistant species of mosses and fungio Increased acidity may result in leaching of toxic metals, especially aluminum, from soil and rocks, making water unfit for drinking or irrigation, as well- Organic pollutants include drugs, pesticides, and other industrial substanceso Many of these chemicals are highly toxico Some can persist in the environment because they are resistant to degradation and toxic to organisms that ingest themo Contamination of surface waters and groundwater by these chemicals is a serious threat to human healtho The 2