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GSC 1620 Chapter 17 Water Pollution
Water Pollution • We obviously need to exchange water and air with the surrounding environment to survive – the quality of that water and air can have profound impact on our health and the ecosystems that support us • To understand the next two chapters better we need to understand the concept of “geochemical cycles”
Geochemical Cycles • Geochemical cycle – a description of the processes governing the passage of a chemical substance through various reservoirs (e.g., soil water air soil) • All chemical substances participate in geochemical cycles of varying complexity and time length • See slides; note the definition of “Residence Time” and tell me the other primary factors which determine a substance’s potential to pollute a reservoir
Simplified Calcium Cycle Residence Time = Capacity of reservoir for a substance Rate of influx of substance into the reservoir
Geochemical Cycles • The three primary factors that determine a substance’s potential to pollute a reservoir: • Substance residence time • Substance’s degree of toxicity in the reservoir • Substance concentration
Residence Times Of Selected Elements In Seawater With Respect To Influx From Modern Runoff
Pollution Sources • Pollution can be characterized as originating from Point or Nonpoint sources • Point source – a readily identifiable site of pollution; example – factory smokestack • Nonpoint source – a diffuse, not readily pinpointed source; example – urban or agricultural land runoff resulting in stream pollution • See slide
Examples of point and nonpoint pollution sources
Pollution Types • Pollution types can be broadly classified as inorganic or organic • Inorganic pollutants include inorganic compounds or chemical elements; examples: metals; coal ash; mine tailings; acid mine drainage; asbestos (see slide and table)
Acid mine drainage
Principal Trace Metals in Industrial Wastewaters(abridged – see complete table in text)
Inorganic Pollutants (Heavy Metals) • Why should we care about certain metals in waters? • Heavy metals – once ingested, metals which are extraordinarily difficult to eliminate via urine, feces or perspiration • These metals bioaccumulate (typically in fat cells) and are especially toxic to the Central Nervous Systems (see slide) • Examples: arsenic, lead, mercury, cadmium, thallium
Inorganic Pollutants (Heavy Metals) • Possible symptoms of heavy metal poisoning? • Some improvements have been achieved in reducing heavy metal emissions (e.g., lead removed from gasoline and paint; mercury removed from most paints and batteries)
Inorganic Pollutants (Heavy Metals) • Be aware of fish consumption advisories for the U.S. especially the Great Lakes region, due to heavy metal (mostly mercury) contamination of the fish (source: mercury vapors released from coal-fired electric power plants) (see slides)
Fish Consumption Advisories Due to Polluted Waters % of lake acres/river miles under fish consumption advisories
Inorganic Pollutants (Heavy Metals) • Remember the e-waste we briefly discussed last chapter? • A cathode ray tube (CRT) computer monitor might contain two pounds of lead, while a big-screen CRT television might contain eight pounds of lead! • E-waste also contains some other heavy metals (e.g., antimony, arsenic) in varying amounts
Inorganic Pollutants (Heavy Metals) • Also be aware that there are natural sources of pollution – this is especially true of certain heavy metals like arsenic (see slides)
Inorganic Pollutants (Heavy Metals) • The arsenic contamination in Oakland and surrounding counties is usually caused by groundwaters that contain dissolved arsenic, leached from minerals in the Marshall sandstone, flowing back to our near-surface sand and gravel aquifers and contaminating them
Inorganic Pollutants ( Examples of Other Sources) • Tons of asbestos-containing solid wastes were dumped into the Great Lakes in the mid twentieth century! • Possible consequences? • Illegally or improperly disposed waste can be a source of inorganic, and organic, pollution and can create environmental health and economic problems (see slides)
Inorganic Pollutants (Saltwater Intrusion) • Saltwater intrusion – a contamination of groundwater when saline waters are drawn into a well • Typically occurs in marine coastal settings or on oceanic islands when groundwaters are pumped faster than they recharge (see slide) • May occur in noncoastal areas where groundwaters pass through certain rock types (e.g., rock salt) under the surface
Pollution Types • Organic pollutants include natural or synthetic organic compounds (compounds whose structural framework is based on the element carbon); examples – human and other animal waste; petroleum products; pesticides (see slides)
Pollution Types • Remember – to properly assess the pollution hazards associated with polluted groundwater it is essential to establish: the direction of groundwater flow; the rate of groundwater flow; and the concentration and toxicity of the contaminants (see slide)
Organic Pollutants (Organic Compounds) • More than 10,000,000 synthetic organic compounds (e.g., polyester, chlorofluorocarbons (CFCs); polyvinyl chloride (PVC), nylon, Teflon) created since the 1930s • A prior survey of 66,000 organic compounds (drugs, pesticides, industrial chemicals) by the National Resources Council (NRC) found that there is no published toxicity data for 70% of these substances and that complete health evaluation data existed for only 2% of these substances!
Organic Pollutants (Organic Compounds) • Additional problem: short-term (hours, weeks) versus long-term (months, years) exposure consequences • See slide – be aware that many organic pollutants (e.g., benzene, polychlorinated biphenyls (PCBs), formaldehyde) are likely carcinogens and that there are ongoing problems with organic pollutants in the Great Lakes region even though some successes have been achieved
2005 National Study; DDT and Dieldrin was banned in the US in 1974!
Organic Pollutants (Organic Compounds) Detection of Pesticides in Urban and Agricultural Areas, 2007 • There’s a growing concern over the concentrations of agrochemicals (e.g., pesticides, fertilizers) in our waterways (and on our foods) – many of these substances are possible or probable carcinogens (see slide)
Organic Pollutants (Organic Compounds) • Another recent concern: disposal of pharmaceuticals by manufacturers or consumers (e.g., flushed down a drain) which may not be removed by wastewater treatment and enter our surface or groundwaters (“pharmawater”) (see slide)
Organic Pollutants (Organic Matter) • Natural organic matter (e.g., human and animal waste, decaying vegetation) can also be a source of water pollution • The decay of organic matter in water consumes what substance vital to the health of aquatic ecosystems?
Organic Pollutants (Organic Matter) • Biochemical Oxygen Demand (BOD) – quantity of oxygen required for aerobic decomposition of organic matter • As the organic matter concentration in water increases, the BOD increases – this can result in the depletion of dissolved oxygen in the water (an “oxygen sag”) • How much (ppm) dissolved oxygen is typically required for a healthy aquatic ecosystem? • See slides illustrating typical “oxygen sag curves” associated with organic matter pollution of waterways
Organic Pollutants (Organic Matter) • Major sources of organic matter pollution: human sewage, animal wastes, food-processing plant (e.g., poultry, cattle) discharges • An increasing concern: organic matter water pollution caused by discharges from CAFOs (concentrated animal farming operations) (e.g., perhaps tens of thousands or more swine or cattle concentrated onto a small feedlot)
Organic Pollutants (Organic Matter) • Example: in 1995, 35 million gallons of animal waste flowed into North Carolina waterways • Related problems: • Increased area of anoxic (severe oxygen depletion) “dead” zones along U.S. coastal margins (see slide) • Rapid expansion in North Carolina coastal waters of a dangerous protozoan that releases a potent neurotoxin into its host • Status of CAFOs in Michigan?
Dissolved-Oxygen in U.S. Surface Waters A 2008 article published in the journal Science reports the presence of nearly 400 “dead zones” of various sizes in the world’s oceans– a definite threat to the ocean ecosystem Source: After U.S. Geological Survey Water Supply Paper 2400.
Organic Pollutants (Organic Matter) • Remember that leaking septic tanks and malfunctioning leach fields may also be sources of organic matter pollution for ground and surface waters