1. Panama is in the industrial phase of transition. Describe the expected trends in the country’s birth and death rates. 2. Describe one advantage and one disadvantage of nuclear energy.

How do our water sources become polluted, and how can we prevent and treat water pollution?

 Water pollution is defined as the contamination of a water sources through the infiltration of chemical, physical or biological agents. ◦ Water pollution degrades the water source’s quality, preventing it from being used. ◦ Water pollution also harms the organisms that may inhabit the water.

 Water pollution can be classified by the source of pollution. ◦ Point-source pollution occurs when pollution can be traced to a single source. This includes mainly leakage (such as septic tanks or landfills), but also includes industrial discharge. ◦ Nonpoint-source pollution occurs when pollution occurs from several different sources (often difficult to isolate). This primarily includes runoff from roads, landscapes, and agricultural fields. It also includes motor oil and gasoline leakage.

 Note that nonpoint- source pollution is much more difficult to contain and treat.  In the U.S., runoff is the single largest water polluter. Prevention often requires public awareness campaigns.

Type of PollutantAgentMajor Sources PathogensDisease causing organisms Primarily nonpoint, such as sewage, feces and runoff Organic MatterAnimal/plant matter, feces, food waste Nonpoint sources Organic ChemicalsPesticides, fertilizers, detergents, petroleum compounds Nonpoint sources, especially farms, lawns, landfills, and waste storage Inorganic ChemicalsAcids, bases, salts, etc. Industrial waste, roads and precipitation Heavy MetalsLead, mercury, cadmium and arsenic Industrial discharge, landfills, mining, household chemicals Physical AgentsHeat, suspended solids Industrial processes (heat), soil erosion (solids)

 Wastewater is water that is carrying waste products from homes or industry. Wastewater must be treated and filtered before it can be returned to a water source.  Water filtration is not perfect, and treated water may still contain some toxic substances. Government regulations are used to maintain the safety of water. ◦ For instance, the EPA puts limits on the minimum safe concentration of metals and chemicals in drinkable water.

 Wastewater treatment is divided into primary and secondary treatment.  In primary treatment, solid materials are separated out to form sewage sludge.  In secondary treatment, the water is first treated with oxygen and bacteria. The bacteria is removed before chlorination occurs.

 The solid material that is isolated from wastewater is sewage. Sewage MUST be disposed of in a secure landfill, since it has dangerous concentrations of toxins.  Often, this involves incinerating sewage, and burning the ash in a secure landfill. ◦ If sewage can be successfully treated, it can later be used as a fertilizer, or even mixed with clay to make bricks.

 Natural nutrients in water often come from organic matter (such as plant remains and animal waste). Nutrients are carried by flowing water, resulting in their deposition.  The deposition of nutrients in the soil can result in eutrophication, when a body of water is slowly converted to a marsh. ◦ As a water becomes saturated with nutrients, those nutrients decay, which removes the oxygen from the water. Plants begin to grown and fill in the waters, and the ecosystem changes over time.

 Artificial eutrophication occurs when this process is started or accelerated due to the infiltration of plant nutrients (especially from sewage and fertilizer).  Algal blooms often develop from artificial eutrophication. As we learned earlier in the year, algal blooms remove oxygen in the water (through decomposition), can poison the water, and destroy local ecosystems.

 Thermal pollution occurs when heated water is discharged into natural water sources.  Power plants are common sources of thermal pollution, because water is drawn from those sources to cool down reactors. ◦ Coal and especially nuclear reactors require water for cooling purposes.  Thermal pollution can directly kill organisms due to excessive heat, but it also removes dissolved oxygen from the water.

 Groundwater pollution usually occurs through polluted surface water.  Pesticides, herbicides, fertilizers and petroleum products are common pollutants.  Groundwater pollution can occur from single sources, such as leaking storage or septic tanks. It can also occur from nonpoint sources, such as runoff.

 At least 85% of ocean pollution results from land sources. Runoff, oil spills, algal blooms and sewage are all serious hazards to ocean ecosystems.  Dead zones – regions with dangerously low oxygen levels – result due to an overabundance of nutrients.