Chemical Recycling

Biogeochemical Cycles

• The cycling of nutrients in an ecosystem involves both the biotic and abiotic parts.

Macronutrients

• Elements required in large amounts– Carbon– Hydrogen– Oxygen– Nitrogen – Phosphorous– Calcium– Sulfur– Water

Micronutrients

• Elements needed on small amounts– Zinc– Molybdenum– Iron– Selnium– Iodine

• For enzymes

Reservoirs

• Storage sites of nutrients

The Cycles

• Water• Carbon• Nitrogen• Phosphorous• Calcium

The Water Cycle

Why Water?

• Best natural solvent• Most chemical reactions in body take

place in water• Main transport medium• Stable• Ionise into hydrogen and hydroxyl (pH)• Resists rapid temperature changes

The Cycle

Precipitation

• Movement of water from atmosphere to Earth

Evaporation

• Sun’s energy turns water to vapour

• Vapour rises to the atmosphere

• Greatest amount of evaporation from the sea

Transpiration

• Water stored in plant tissues moves up the plant to the leaves

• Carries nutrients with it to the leaves

• Leaves the plant as water vapour through stomata

Metabolic Water

• Cycled by– Photosynthesis and respiration– Drinking and excretion– Burning fossil fuels– Decay by micro-organisms

Humans

• Deplete surface and ground water

• Wasteful use of water

• Pollution

Carbon Cycle

Carbon

• Key compound in – Carbohydrates– Fats– Proteins

Reservoir

• Limestone (CaCO3)• Atmospheric carbon dioxide• Carbon compounds dissolved in water• Fossil fuels

The Cycle

Humans

• Burn forests– Stop photosynthesis– Increase CO2

released by compustion

• Burn fossil fuels– Coal and wood– Petrol, diesel

Global Warming

• Ozone layer reflects some radiation

• CO2 + water vapour reflect radiation back to Earth

• Causes general warming of Earth

Nitrogen Cycle

Nitrogen

• For proteins– Body structure– Enzymes– Hormones– Haemoglobin

Reservoir

• Air 78% nitrogen but largely unusable• Used as nitrate ion dissolved in soil

water• Must be fixed by

– Lightening– Bacteria in legumes– Free-living bacteria– cyanobacteria

The Cycle

• Nitrate absorbed by plant roots and turnid into proteins

• Animals eat proteins• Leaves body as waste (urine, faeces)• Decomposers turn into ammonia

(aminification)• Ammonia turned into nitrate by nitrifying

bacteria (nitrification)

• Nitrite absorbed by plants

• Nitrogen in air fixed by lightening or Rhizobium

• Rhizobium in mutualistic relationship with legumes

• Denitrifying bacteria break down nitrates to nitrogen

Humans

• Use nitrogenous fertilisers• Add compost or sewage• Plant legumes• Remover plants or animals (remove nitrogen)• Plant removal causes nitrates to be released

(leaching)• Remove oxygen (no nitrification)• Burn fossil fuels (nitrous oxide released)

Phosphorous Cycle

Phosphorous

• For DNA, RNA, ATP, phospholipids, bones, teeth, photosynthesis, respiration

Calcium Cycle

• Similar to phosphorous cycle• Calcium for

– Cell membranes– Enzymes– Bones, teeth, exoskeletons

Humans

• Fertilisers add phosphorous and increase the rate of calcium recycling

• Seabird deposits accumulated over years mined for fertiliser

• Fishing returns calcium from sea to land