Biogeochemical Cycles CP Environmental Science

Biogeochemical Cycles The chemical interactions that exist between the atmosphere, hydrosphere, geosphere, and biosphere. Carbon Cycle Nitrogen Cycle Phosphorus Cycle Water Cycle

The Carbon Cycle The process by which carbon is cycled between the atmosphere, land, water, and organisms. Reservoirs – places where carbon is stored. – Oceans contain dissolved CO 2 – Limestone – over millions of years, carbonate deposits (comes from bones and shells) produce huge formations of limestone rock. Limestone is one of the largest carbon sinks = carbon reservoir.

Fossil Fuels Decomposition – the process by which dead tissues of an organism break down into simpler forms of matter. Fossil fuels are coal, oil, natural gas. They are made up of carbon compounds from the bodies of organisms that died millions of years ago. Combustion – the burning of fossil fuels.

The Nitrogen Cycle

Largest concentration of N 2 is in the atmosphere. Plants and animals cannot use nitrogen directly from the atmosphere. It must first be “fixed” – converted into a form that plants can use. Nitrogen fixation – nitrogen gas is captured from the air by species of bacteria that live in soil and in roots of legumes. Some nitrogen is fixed during electrical storms and is washed out of the atmosphere and into the soil during rainfall. Plants take up nitrogen so they can make proteins which are stored in their cells.

Nitrogen Cycle Nitrogen is added to soil when chemical fertilizers are applied to lawns, crops, or other areas. Nitrogen enters the food web when plants absorb nitrogen compounds from the soil and convert them into proteins. Consumers get nitrogen by eating plants or animals containing nitrogen.

Nitrogen is returned to the soil in several ways: When an animal urinates, nitrogen returns to the water or soil and is reused by plants. When organisms die, decomposers transform the nitrogen in proteins into ammonia. Organisms in the soil convert ammonia into nitrogen compounds that can be used by plants. Denitrification – some soil bacteria convert fixed nitrogen compounds back into nitrogen gas so it goes back into atmosphere.

TAKE OUT YOUR STUDY GUIDE! Turn to page 77 in ES Textbook and work on S.G. #15-19

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The Phosphorus Cycle Phosphorus is needed to form bones and teeth in animals. Plants get phosphorus from soil and water. Animals get phosphorus by eating plants or animals that have eaten plants. The phosphorus cycle is the movement of phosphorus from the environment to organisms and then back to the environment. A slow cycle. No phosphorus in the atmosphere.

How does phosphorus enter the cycle? When rocks erode, small amounts of phosphorus dissolve as phosphate in soil and water. Plants absorb phosphates in the soil through their roots. Phosphorus is also added to soil and water from the waste of organisms and from the decomposition of dead plants and animals.

Too Much Nitrogen and Phosphorus Causes Problems for Aquatic Ecosystems! Nitrogen and phosphorus are in fertilizers. Runoff washes these fertilizers into streams, rivers, ponds, lakes, oceans. This causes algal blooms – dense growth of algae. When the algae die, the bacteria that break them down rob the water of oxygen so fish die. Called eutrophication.

The Water Cycle