Water

• Ice caps and glaciers
• Groundwater

One-sixth of world's population

1 gallon a day

• Point sources: Sewer outlet, steel mill or septic tank
• Nonpoint sources: Fertilizer runoff from a farm, acid drain from a strip mine

• Human and animal waste - causes diseases - bacteria, virus
• Sewage, inorganic fertilizers - cause excessive growth of algae - nitrates
• Industry, farms, households - add toxins to aquatic systems
• Land erosion - disrupt photosynthesis, food webs, other processes

• Typhoid fever
• Cholera
• Bacterial dysentery
• Enteritis

Passing of elements through a series of reservoirs

How much time each element spends in a reservoir such as river stream, lake or ocean

• If a specific chemical has a residence time of 20 years, then after 20 years about half of the chemical should be gone from the reservoir.
• We can apply this concept to toxic chemicals that are introduced into nature as human-created pollution

Chlorine and sodium

Iron

• Biochemical Oxygen Demand (BOD)
• Amount of oxygen needed to break down the organic matter (sewage) aerobically
• Measures the rate of uptake of oxygen by microorganisms in the sample of water at a fixed temp (20C) and over 5 days in the dark

Dissolved oxygen - unit is ppm

• If it has a DO of 8-9
• If the DO is below 4, the water is gravely polluted

Less than 1 ppm

More than 10 ppm

A graph of dissolved oxygen content as a function of distance from the waste source

Organic matter from human and animal wastes that are dumped into water

• Organic matter is broken down by microorganisms if there is ample oxygen in the water
• Aerobic decomposition occurs until oxygen is used up
• Releases methane and hydrogen sulfide

The breakdown of excess organic matter not only consumes oxygen but also releases a variety of compounds such as nitrates, phosphates and sulfates

Plant nutrients that encourages the rapid and excessive growth of aquatic plants like algae

• The exuberant algal growth and appears as slimy green scum floating on the water
• Worsen the water quality
• The scum blocks out the sunlight and the aquatic plants begin to die

• They behave as plant nutrients and are harmful to the environment
• Were added to laundry detergents to enhance cleaning ability by softening the water

• A neurotoxin that acts on the central nervous system of the human body
• Causes loss of sight, feeling and hearing

Adverse effects to nervous system caused by methylmercury

• Lethal and can cause skin and bladder cancer
• Dissolved out of soils and rocks and can enter the groundwater

Set at 50 ppb

• Chlorine
• Acid mine drainage

• Causes water to be murky and unpleasant to look at, swim in or drink
• Reduces the light available to underwater plants and covers food supplies of aquatic animals
• Clogs water filter and damages power-generating equipment

15%

• Crude oil - 3 years
• Refined oil - 10-20 years

Sewage treatment - using wetlands to treat sewage