Pollution & Toxins Pollutant Substance in the environment that produces a condition that is harmful to living things Toxin Substances that produce serious health problems or death

How can chemicals be introduced into the environment? 1. Agriculture Fertilizer Pesticides 2. Wastes Solid Waste-water

3. Fuel combustion Fossil fuels When burned – release CO2 and H2O 4. Industry

Effects of Chemicals on Environment Biological magnification Increase in concentration of a substance as it moves up the food chain / web Eg. DDT

Measuring Toxicity LD50 Amount used to compare the effects of different toxins LD = lethal dose 50 = 50% Amount of a substance that causes 50% of a group of test organisms to die if given a specific dose The lower the LD50 The less needed to kill test organisms The more toxic the substance Ex. LD50 of 150 is more toxic than LD50 of 200

Concentration Amount of a substance in a given volume Ways to measure g / L % PPM (parts per million) mg / L 1 part substance in 1 000 000 parts of H2O 1 mg substance / 1 L H2O 1 ppm = 1 drop of food coloring in a bathtub half full of water

How to calculate ppm: Eg. If you add 0.1 ml of DDT to 2000 ml of water, what is the concentration in ppm? Set up an equivalent ratio 0.1ml DDT x = 2000ml water 1 000 000ml 0.1 (1 000 000) = 2000x 100 000 = 2000x x = 50

PPB (parts per billion) 1 ppb = 1 drop of food coloring in a swimming pool PPT (parts per trillion) 1 ppt = 1 drop of food coloring in 1000 swimming pools

Disposal of Solid Wastes Incineration Burn wastes @ very high temperatures Emissions may contribute to air pollution Dump Open hole in the ground where trash is buried Substances are able to leach (leak) into surrounding soil and ground water

Removal of materials by dissolving them away from solids Leaching Removal of materials by dissolving them away from solids Leachate (liquid that dissolves and carries substances) can contaminate water supplies Landfill Carefully designed structure built into/on top of ground Trash is isolated from the surrounding environment by the use of a bottom liner and daily coverings of soil Prevents leaching http://www.galaxy.net/~k12/recycle/leaching.shtml

Disposal of Liquid Wastes Septic tank Underground container where bacteria break down organic materials Often used when households are not connected to municipal sewer (eg. acreages, farms) Storm sewers Water directly enters rivers or lakes without treatment or cleaning

Sewage treatment plant Treat wastewater with several steps including filtration, chemical treatment and biological treatment Treated wastewater = effluent Can be released into rivers or lakes May still contain N, P and other substances not removed by filtration