Nutrients Cycle Lecture PDF

BUITEMS Department of Environmental science Nutrients Cycle  Nutrient Cycle Definition HBCD 主要用作塑料工业中阻燃添加剂 “A nutrient cycle is defined as the cyclic pathway by which nutrients pass-through, in order to be recycled and reutilized. The pathway comprises cells, organisms, co...

BUITEMS Department of Environmental science Nutrients Cycle  Nutrient Cycle Definition HBCD 主要用作塑料工业中阻燃添加剂 “A nutrient cycle is defined as the cyclic pathway by which nutrients pass-through, in order to be recycled and reutilized. The pathway comprises cells, organisms, community and ecosystem.” 2  Nutrient Cycle HBCD 主要用作塑料工业中阻燃添加剂  In the process, nutrients get absorbed, transferred, released and reabsorbed. It is a natural recycling system of mineral nutrients.  Nutrients consumed by plants and animals are returned to the environment after death and decomposition and the cycle continues.  Soil microbes play an important role in nutrient recycling. They decompose organic matter to release nutrients. They are also important to trap and transform nutrients into the soil, which can be taken up by plant roots.  Nutrient cycling rate depends on various biotic, physical and chemical factors.  Examples of a nutrient cycle: carbon cycle, nitrogen cycle, water cycle, oxygen cycle, etc. Recycling of Carbon, Hydrogen, Nitrogen and Oxygen occurs in water, air and soil, whereas calcium, phosphorus, potassium, etc. are recycled mainly in soil and are available locally. The 4 main nutrient cycles are 3  Carbon Cycle HBCD 主要用作塑料工业中阻燃添加剂  Carbon is the main constituent of all the living cells. All the organic matter and biomolecules contain carbon.  Carbon is present mainly as carbon dioxide (CO2) and methane (CH4) in the atmosphere  There is a continuous exchange of carbon between biotic and abiotic components by the process of photosynthesis and respiration  Atmospheric carbon dioxide is fixed by plants in the process of photosynthesis  All the living organisms release carbon dioxide during respiration  Carbon is released into the atmosphere by burning of fossil fuels and auto emissions  Organic carbon from dead and decaying organisms and waste products is released into the atmosphere after decomposition 4  How Carbon Changes Form: HBCD 主要用作塑料工业中阻燃添加剂 1. Photosynthesis (in plants, algae and cyanobacteria) CO2 + H2O + sunlight C6H12O6 + O2 2. Cellular respiration (in cells of all living things) C6H12O6 + O2 CO2 + H2O + ENERGY (energy is used for growth, repair etc.) 3. Decomposition (rotting) – done by bacteria/fungi cellulose  CO2 5  1.Carbon Cycle HBCD 主要用作塑料工业中阻燃添加剂 4. : Ocean mixing: moves CO2 around the world - CO2 sinks in cold ocean waters  flows to the warm equator and evaporates into the air. 5.Combustion: (burning, engines, volcanoes, forest fires) fossil fuels + O2  CO2 + H2O + ENERGY (oil, gas, natural gas, coal) 6  Nitrogen Cycle HBCD 主要用作塑料工业中阻燃添加剂  Nitrogen is also an essential component of life.  Nitrogen cannot be directly utilized by living organisms and has to be converted to other forms.  By the process of nitrogen fixation, nitrogen-fixing bacteria fix atmospheric nitrogen to ammonia and nitrifying bacteria convert ammonia to nitrate. It is then taken up by plants  Atmospheric nitrogen is converted to nitrates directly by lightning and assimilated by plants  Decomposers break down proteins and amino acids of dead and decaying organic matters and waste product  Denitrifying bacteria convert ammonia and nitrates to nitrogen and nitrous oxide by the process of denitrification. In this way, nitrogen is released back into the atmosphere. 7  How Nitrogen Changes Form: HBCD 主要用作塑料工业中阻燃添加剂 - N2 is not usable by plants or animals, so it has to be converted to other forms. - Plants can use NO3- (nitrate) and NH4+ (ammonium) 1. Nitrogen Fixation Lightning changes N2 (nitrogen gas)  NO3- (nitrate). Rain washes nitrate into soil. (small amount) Bacteria in soil (rhizobium) & cyanobacteria in water change N2 (nitrogen gas)  NH4+ (ammonium). 8 HBCD 主要用作塑料工业中阻燃添加剂 2. Nitrification (done by nitrifying bacteria). NH4+ (ammonium)  NO2- (nitrite)  NO3- (nitrate) 3. Uptake NO3- is sucked into plants & used for growth. Herbivores eat plants & use N for making proteins & DNA. 4. Denitrification (done by denitrifying bacteria & volcanic eruptions) NO3-  N2 9  Human activities affect the nitrogen cycle. HBCD 主要用作塑料工业中阻燃添加剂 The amount of nitrogen in the ecosystem has doubled in 50 y. due to: 1. Burning fossil fuels & sewage treatment. NO & NO2 are byproducts 2. Land-clearing by burning. acid rain is formed which contains nitric acid (HNO3). 3. Over fertilization NH4+ & NO3- leach into soil & waterways. huge growth in aquatic algae = eutrophication These algal blooms use up all CO2 & O2, block sunlight & produce neurotoxins which poison and kill many aquatic organisms. 10  Oxygen Cycle HBCD 主要用作塑料工业中阻燃添加剂  Oxygen is essential for life. Aquatic organisms are dependent on oxygen dissolved in water. Oxygen is required for decomposition of biodegradable waste products.  Photosynthesis is the main source of oxygen present in the atmosphere  Atmospheric oxygen is taken up by living organisms in the process of respiration and release carbon dioxide which is used for photosynthesis by plants. 11  Hydrologic or Water Cycle HBCD 主要用作塑料工业中阻燃添加剂  Water is an essential element for life to exist on earth.  Water from oceans, lakes, rivers and other reservoirs is continuously converted to vapour by the process of evaporation and transpiration from the surface of plants  Water vapours get condensed and return by precipitation and the cycle continues  The water falling on the ground is absorbed and stored as groundwater. 12  Hydrologic or Water Cycle HBCD 主要用作塑料工业中阻燃添加剂 1. Water cycles between the oceans, atmosphere and land. All living organisms require water. A. Water enters the atmosphere as water vapor, a gas, when water evaporates from the ocean or other bodies of water. Evaporation—the process by which water changes from a liquid to a gas. Water can also enter the atmosphere by evaporating from the leaves of plants— Transpiration. 13  Hydrologic or Water Cycle HBCD 主要用作塑料工业中阻燃添加剂 Precipitation--rain, snow, sleet, or hail a. The sun heats the atmosphere. b. Warm, moist air rises and cools. c. Eventually, the water vapor condenses into tiny droplets that form clouds. d. When the droplets become large enough, the water return to Earth’s 14  Hydrologic or Water Cycle HBCD 主要用作塑料工业中阻燃添加剂 Run-off—Precipitation runs along the surface of the ground until it enters a river or a stream that carries the run- off back to an ocean or lake. Seepage—Rain also seeps into the soil, some of it deeply enough to become ground water. Water in the soil enters plants through the roots, and the water cycle begins anew. 15  Hydrologic or Water Cycle HBCD 主要用作塑料工业中阻燃添加剂 The path of water through our environment, known as the hydrologic cycle, is perhaps the most familiar material cycle. Most of the earth’s water is stored in the oceans, but solar energy continually evaporates this water, and winds distribute water vapor around the globe. Water that condenses over land surfaces, in the form of rain, snow, or fog, supports all terrestrial (land-based) ecosystems. 16  Hydrologic or Water Cycle HBCD 主要用作塑料工业中阻燃添加剂 As it moves through living things and through the atmosphere, water is responsible for metabolic processes within cells, for maintaining the flows of key nutrients through ecosystems, and for global-scale distribution of heat and energy. Water performs countless services because of its unusual properties. Water is so important that when astronomers look for signs of life on distant planets, traces of water are the key evidence they seek. 17  Hydrologic or Water Cycle HBCD 主要用作塑料工业中阻燃添加剂 What happens to the surplus water on land—the difference between what falls as precipitation and what evaporates? Some of it is incorporated by plants and animals into biological tissues. A large share of what falls on land seeps into the ground to be stored for a while (from a few days to many thousands of years) as soil moisture or groundwater. 18  Importance of Nutrient Cycling HBCD 主要用作塑料工业中阻燃添加剂  All living organisms, biomolecules and cells are made up of carbon, hydrogen, oxygen, nitrogen, sulphur and phosphorus. These elements are essential for life. It is important to recycle and continuously replenish nutrients into the environment for life to exist. Nutrient cycling is important for:  It is required for the transformation of nutrients from one form to another so that it can be readily utilised by different organisms, e.g. plants cannot take atmospheric nitrogen and it has to be fixed and converted to ammonium and nitrate for uptake.  Transfer of nutrients from one place to another for utilization, e.g. air to soil or water  Nutrient cycles keep the ecosystem in equilibrium and help in storing nutrients for future uptake  Through nutrient cycling, living organisms interact with the abiotic components of their surroundings. 19 Thanks ！