SOIL AND ACID PRECIPITATION

Soil is what sustains plants.

Plants are what sustains ecosystems

What is Soil?

Soil… It is more than just dirt!! Soil has many life forms within it, and this

life is crucial for the health of the ecosystem it is in.

Soil is a loose covering over the ground that contains organic matter, minerals (rocks), and moisture.

To assess soil quality, we must look at Soil profile Soil Type Acidity

Soil ProfileThere are three distinct layers to the composition

of soil:1) Topsoil – O and A layers.

It is composed mostly of humus, which is decaying organic matter. It has rocks and many organisms like bacteria, fungi, insects and worms.

2) Subsoil – B layerIt is very compact and has little or no organic matter except roots of very large trees and bacteria

3) Regolith and bedrock – C and R layersThe regolith is composed of large chunks of rock, and the bedrock is solid rock. Water cannot pass through bedrock, so it pools here. This is where aquifers (groundwater) are located.

50% pore space

50% solid

material

25% air

25% water

45 to 48%

mineral matter

2 to 5% organic matter

Volume composition of a desirable surface soil

Not all soil has this balance – only the most desirable soil. For example, C layer soil is mostly mineral matter. It has little water and air, and no organic matter.

Soil Particles All soil originated from bedrock,

therefore all soil is made up minerals (weathered rock)

The weathered rock is known as soil particles. The soil particles are classified from largest to smallest as sand, silt, and clay

Types of Soil

1) Sand: Relatively large

particles Feels coarse and

gritty Creates large

spaces that permit root growth and air pockets for plants

Water drains too easily, taking nutrients away from roots of plants

Types of Soil2) Silt:

Fine particles, a muddy texture

Easily transported by water, so it is found in and along rivers and wetlands

Soil drains slowly, so it facilitates plant growth. However, the soil also erodes easily.

Human activities such as logging and bad farming practices result in unwanted silt being washed into rivers, which is a pollutant

Types of Soil

3) Clay: Very fine particles Particles are

packed tight together, so there are no air pockets. It is dense.

Clay traps water so it is often very wet and sticky.

Plant growth is difficult.

Types of Soil

4) Loam Has rock particles of

different sizes (sand, silt, and clay) and pockets that hold air or water

Has lots of humus Drains well without

drying out Plants grow easily Has a dark brown or

black colour

Types of Soil

Which soil type do you think is best for agriculture?

Human Impacts on Soil Soil Erosion: The loss of soil when water or

wind blows it away. This occurs when soil is ploughed or tilled and the

topsoil is exposed to wind and water which causes it to erode.

Occurs due to overgrazing by livestock or too much ploughing for farming

If the top soil is gone, the nutrients are gone.

Human Impacts on Soil Fertilization: The process of a farmer adding

extra nutrients to the soil to make plants grow bigger and faster Without fertilizers, many farmers would not be able to

grow as much food Manure is a natural fertilizer Artificial fertilizers are common nowadays – they are

synthetic chemical compounds of nitrogen, phosphorus, etc.

This fertilizers wash away from the soil and pollute local water bodies. It results in excessive algae growth (eutrophication).

Human Impacts on Soil

Leaching: The process by which soil receives a lot of water, and the nutrients in the topsoil wash downward, making them unavailable to plants. In wet environments, such as

rainforests, this occurs naturally. This is why rainforests are not good for farming.

When humans overly water soils, nutrients are leached from the topsoil. Sandy soil gets leached easily. Why is this?

Humans Impacts on Soil Crop Rotation: The

practice of planting a different crop in a field each year. This is good for the soil. This replenished the

nutrients in soil Crops such as legumes,

help put nitrogen in the soil since they have nitrogen-fixing bacteria

If crops are not rotated, the nutrients in the soil get used up and crops will no longer grow well.

Acidity of Soil Acidity is another factor in soil quality We use the pH scale to assess the acidity

level of soil

Acidity of Soil If soil has a low pH (0-7) it is considered acidic If soil has a high pH (7-14) it is considered

alkaline Most plants and organisms prefer a neutral

environment If soil is too acidic or alkaline it can harm plants:

The roots that absorb the plants’ nutrients are damaged

The waxy coating on plants’ leaves that prevents it from infection is damaged

However, some plants do require slightly acidic or alkaline pH levels

Earthworms in the soil are also harmed because their skin gets burned

You will also have an opportunity to do you Soil Lab ISU on acidity

Acid Precipitation Acidic soil is the result of

Acid Precipitation Acid precipitation

describes any form of rain or snow with high levels of nitric and sulfuric acids.

It is 40 times more acidic than normal rain

When humans burn fossil fuels, sulfur dioxide and nitrogen oxides are released into the atmosphere, which react with water, oxygen, and other substances to form mild solutions of sulfuric and nitric acid.

Sources of Acid Precipitation

• Emissions come from coal burning plants, cars, metal smelters and oil refineries

• However, Cars are the biggest cause of acid rain by burning fuels

• Although countries have emission standards on cars there are more and more cars being driven.

A forest affected by acid precipitation

Aquatic Impacts

In addition to soil, acid precipitation affects aquatic ecosystems: lakes, streams, wetlands, and other aquatic environments

Acid rain makes waters acidic and causes them to absorb the aluminum that makes its way from soil into lakes and streams. This combination makes waters toxic to crayfish, clams, fish, and other aquatic animals.

Shellfish are particularly sensitive because the acid dissolves their shell

Action on Acid Precipitation

When scientists discovered the damaging effects of acid precipitation, governments put limits of emissions

Factories have installed scrubbers in their smoke stacks, which remove a large proportion of the damaging chemicals from the emissions before they’re released into the air

Acid precipitation has been reduced, but countries that have not implemented emission standards continue to produce pollution – which is carried by wind. Therefore, acid precipitation is a global problem.

Homework

Read pages 70-75

Soil Page 75 #1-5 Page 85 #3, 13, 14

Acid Precipitation Page 85 #11, 15, 16