ENVIRONMENTAL SCIENCE

BIOGEOCHEMICAL CYCLES

JOEMAR J. CABRADILLA,MSEInstructor I

Ilocos Sur Polytechnic State College

Objectives:

a. Identify and describe the flow of nutrients in each biogeochemical cycle.

b. Explain the impact that humans have on the biogeochemical cycles.

What Sustains Life on Earth?

Solar Energy

The Cycling of Matter

Gravity

Two Secrets of Survival: Energy Flow and Matter

Recycle

An ecosystem survives by a combination of energy flow and matter recycling.

MATTER CYCLING IN ECOSYSTEMS

Nutrient Cycles: Global Recycling

1. Global Cycles recycle nutrients through the earth’s air, land, water, and living organisms.2. Nutrients are the elements and compounds that organisms need to live, grow, and reproduce.

3. Biogeochemical cycles move these substances through air, water, soil, rock and living organisms.

describe the flow of essential elements from

the environment through living organisms and

back into the environment.

BIOGEOCHEMICAL CYCLES

WATER CYCLE (HYDROLOGICAL CYCLE)

Evaporation

Condensation

PrecipitationPrecipitation

Transpiration

Infiltration and

Percolation

Precipitation to land

Transpiration from plants

RunoffSurface runoff (rapid)

Groundwater movement (slow)

Evaporation from

landEvaporation from ocean

Precipitation to ocean

Surface

runoff (rapid

)

Ocean storage

Effects of Human Activities on Water Cycle

We alter the water cycle by:

Withdrawing large amounts of freshwater.

Clearing vegetation and eroding soils.

Polluting surface and underground water.

Contributing to climate change.

WATER CYCLE (HYDROLOGICAL CYCLE)

1. Reservoir – oceans, air (as water vapor), groundwater, lakes and glaciers; evaporation, wind and precipitation (rain) move water from oceans to land

2. Assimilation – plants absorb water from the ground, animals drink water or eat other organisms which are composed mostly of water

3. Release – plants transpire, animals breathe and expel liquid wastes

CARBON CYCLE

CARBON CYCLE

1. Reservoir – atmosphere (as CO2), fossil fuels (oil, coal), durable organic materials (for example: cellulose).

2.Assimilation – plants use CO2 in photosynthesis; animals consume plants.

3. Release – plants and animals release CO2 through respiration and decomposition; CO2 is released as wood and fossil fuels are burned.

Effects of Human Activities on Carbon Cycle

We alter the carbon cycle by adding excess CO2 to the atmosphere through:• Burning fossil fuels.• Clearing vegetation faster than it is replaced.

NITROGEN CYCLE

NITROGEN CYCLE(Nitrogen is required for the

manufacture of amino acids and nucleic acids)

1. Reservoir – atmosphere (as N2); soil (as NH4

+ or ammonium, NH3 or ammonia, N02

- or nitrite, N03- or

nitrate2. Assimilation – plants absorb nitrogen as either NH4

+ or as N03-,

animals obtain nitrogen by eating plants and other animals. The stages in the assimilation of nitrogen are as follows:

Nitrogen Fixation: N2 to NH4+

by nitrogen-fixing bacteria (prokaryotes in the soil and root nodules), N2 to N03

- by lightning and UV radiation.

Nitrification: NH4+ to N02

- and N02- to N03

- by various nitrifying bacteria.

3. Release – Denitrifying bacteria convert N03

- back to N2 (denitrification); detrivorous bacteria convert organic compounds back to NH4

+

(ammonification); animals excrete NH4

+ (or NH3) urea, or uric acid.

Effects of Human Activities on the Nitrogen Cycle

We alter the nitrogen cycle by:Adding gases that contribute to acid rain.

Adding nitrous oxide to the atmosphere through farming practices which can warm the atmosphere and deplete ozone.

Contaminating ground water from nitrate ions in inorganic fertilizers.

Releasing nitrogen into the troposphere through deforestation.

Effects of Human Activities on the Nitrogen Cycle

Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined.

QUICK REVIEW!!

Evaporation

Condensation

PrecipitationPrecipitation

Transpiration

Infiltration and

Percolation

Precipitation to land

Transpiration from plants

RunoffSurface runoff (rapid)

Groundwater movement (slow)

Evaporation from

landEvaporation from ocean

Precipitation to ocean

Surface

runoff (rapid

)

Ocean storage

PHOSPHORUS CYCLE

PHOSPHORUS CYCLE1. Reservoir – erosion transfers phosphorus to

water and soil; sediments and rocks that accumulate on ocean floors return to the surface as a result of uplifting by geological processes

2. Assimilation – plants absorb inorganic PO43-

(phosphate) from soils; animals obtain organic phosphorus when they plants and other animals

3. Release – plants and animals release phosphorus when they decompose; animals excrete phosphorus in their waste products

Effects of Human Activities on the Phosphorous Cycle

We remove large amounts of phosphate from the earth to make fertilizer.We reduce phosphorous in tropical soils by clearing forests.We add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers.