1. Salt water and contaminants

2. On earth there is a lot of water, about 70% of the earth's surface is made up of water. Unfortunately only 3% is fresh water. Most of this water is either deep underground or frozen in glaciers and polar ice. It's down to about 0.4% of earths water is fresh water and attainable. Even then, fresh water doesn't mean drinkable.

3. Let's compare fresh water and salt water. Salt water has salt dissolved in it, this makes salt water denser. The amount of salt in the water is called the salinity as we know from our project.

4. Salinity is measured in g/L. We can also write salinity as a concentration, which is a percent. For instance the dead sea is 30% salt solution. (3/10 to become 300g/L) This is why in the dead sea, it is very easy for a human to float on the top of the water.

5. So how are we still alive with all this salt in the water? We are able to get salt out of water because salt doesn't evaporate. The process of separating salt and water is a process called desalination.

6. One process is to use thermal energy to make the water evaporate, then collecting the water vapour to be cooled down into liquid water leaving behind. This takes a lot of energy, so some technologies harness energy from the sun or geothermal energy (heat from the earth) to evaporate water. Another process is the reverse osmosis method because salt is bigger than water particles.

7. Salt isn't the only thing in water that we don't want in there. Many other things called contaminants are in the water that make it un-drinkable. Salt is one example of a contaminant. Road salt, melting ice/snow has salt in it that can runoff into the water systems.

8. Minerals from rocks have a similar effect as salt in the water. They dissolve in water making it undrinkable usually. Fertilizers are used by farmers to help their plants to grow bigger, stronger, faster, smarter. The problem is, when fertilizers get in the water, they cause tiny water plants called algae to grow bigger, stronger, faster, smarter. This disrupts the ecosystem which influences the water quality.

9. Herbicides and pesticides are also used by farmers to kill off unwanted weeds and insects. The problem is, if those herbicides and pesticides don't get used they can stay around for up to 5 years. They can dissolve into ground water. These substances are designed to kill other living things which makes them not good for humans to drink either. One big example of this was the pesticide DDT. This really hurt the bird population by causing the eggs to have very thin shells. These eggs would often hatch too early/ break before they could hatch which greatly decreased the bird population. We no longer use DDT as it is illegal. Herbicides and Pesticides

10. Our pollution in the air has lead to acid rain. The acid in the acid rain is not good for us to drink. So our pollution is ending up putting acid in our water which is hurting us. Other chemicals that accidentally end up in our water such as garbage and heavy metals (lead, zinc, mercury) from various sources such as ships crashing that carry these items. Pollution

11. Biological contaminants: Living things also need water, so they often live in or near water and can end up getting mixed in with our water supply. Salmonella, E. Coli, Giardia are micro-organisms that can cause humans and other animals to become very sick. Even waste from cattle can wash into water. This uses up oxygen as it decomposes which will then kill aquatic life leading to more bad things floating around in the water. Not to mention the waste itself is gross in the water.

12. Conclusion pg 291 # 1,3,4 pg 295 # 1,3,4