Biogeochemical Cycles Explanation PDF

Biogeochemical Cycles By Teacher Jorge  Water Carbon Phosphorus Nitrogen  Terms to be familiar with Reservoir o Any part or component of the cycle, living or not, that contains the matter at hand. It can be either a source or a sink.  Source o A type of reservoir w...

Biogeochemical Cycles By Teacher Jorge  Water Carbon Phosphorus Nitrogen  Terms to be familiar with Reservoir o Any part or component of the cycle, living or not, that contains the matter at hand. It can be either a source or a sink.  Source o A type of reservoir where the matter leaves to go to another part of the cycle.  Sink o A type of reservoir where the matter goes to, from another part of the cycle. Water Why is water important? Essential for life. Makes up for half of the weight of all organisms. Allows the transport of molecules and waste materials within the body. Water can be found in all 3 states (solid, liquid, gas) in nature. Solar Energy Provides energy for evaporation to occur. Provides energy for photosynthesis and, in turn, also triggers transpiration from plants. Water goes up as vapor, condenses, and then falls back down. After precipitation, 3 routes can occur: Evaporate back again, or be taken by plants to be transpired again. Total evaporation + transpiration is known as evapotranspiration Move as runoff back to rivers, lakes and eventually the ocean. Percolate the ground and sink into groundwater. How do humans impact the cycle? Earth is a closed system, so the total amount of water never changes. Cutting trees increases runoff and percolation, decreases transpiration and provoke flooding or erosion. Use water for irrigation, drinking, etc. Carbon Why is carbon important? Base for everything “organic” and everything we use as building blocks for our body. Makes up for 20% of the weight of all organisms.  There are 7 steps involved in the carbon cycle. These processes are considered fast (if they occur on the living side, or with the exchange of CO2 between air and water) or slow (if they occur in the geological side, where they turn into hydrocarbons or petroleum).  Photosynthesis and Respiration CO2 + H2O > C6H12O6 + O2 O2 + C6H12O6 > CO2 + H2O + ATP Carbon cycles through the food web whenever organisms are consumed or die. Exchange Carbon from the air to the sea is almost the same as the one from the sea to the air. Some get used by algae or phytoplankton for photosynthesis. Some stays and combines with Ca to form CaCO3. Sedimentation and Burial CaCO3 is used by organisms or precipitates to form carbon- containing rocks such as limestone. When animals die they also go to the bottom and fossilize over thousands or millions of years. The carbon removed by burial is the same as the one released by erosion or volcanic activity.  Extraction and Combustion Everything that burns has the following reaction products: CO2 + H2O + energy Discovery of fossil fuels as an energy source has accelerated the process. How do humans impact the cycle? The slow part of the cycle is accelerated, increasing the presence of CO2 in the atmosphere. Removing forest for farmland increase atmospheric CO2 and remove the ability to continue the cycle. CO2 levels have gone from 200ppm (1600-1800) to 420ppm (1800+) from the industrial revolution. Phosphorus Why is phosphorus important? Major component of RNA and DNA and energy molecules. Very important in agriculture. Limiting nutrient with nitrogen in aquatic environments.  Occurs in land and water. Has no gas phase. Mostly in the form of phosphate (PO4 3-) Because soils retain so much phosphate, it is a limiting nutrient in aquatic environments.  Assimilation: Plants take phosphate from the soil and use it to create organic phosphorus within its their tissue. Animals consume plants or plant-eating animals to get phosphorus. Mineralization: Waste products and dead bodies are decomposed by bacteria and fungi, which causes organic phosphorus to turn into phosphate.  Sedimentation: phosphate accumulates in layers in the soil and eventually creates phosphate rocks in the ocean or soil. Geologic uplift: Due to plate tectonics, the rocks get exposed back again in the surface within mountains. Weathering: Being exposed to the elements like rain and wind, rocks get weathered down, and the sediments get back into the ocean or soil. How do humans affect the cycle? Fertilizer and detergents are prone to provoke algal blooms, creating anoxic conditions in bodies of water and threatening wildlife. Some waste products of these algal blooms can be toxic to the rest of the trophic chain, or even to people. Altering composition of plant communities because of phosphorus availability. Nitrogen  78% of the atmosphere is nitrogen gas. Has a lot of chemical changes throughout the cycle. Highly important for agriculture. Nitrogen Fixation Can occur through biotic or abiotic processes. Biotic: Bacteria (Rhizobium, Azotobacter, Azospirillum, etc.) transform atmospheric nitrogen into ammonia (NH3) which is rapidly transformed into ammonium (NH4+). Excess ammonium is excreted, and then used by other organisms. Abiotic: it can occur in 2 different ways, by fires or lightning. Both essentially break N2 bonds and combine with oxygen to form nitrate (NO3-). Nitrification Specialized bacteria transform ammonium (NH4+) into nitrite (NO2-) and subsequently into nitrate (NO3-). The most common way for nitrogen to be used by plants is nitrate. Nitrite is barely used as it is. Assimilation Integrating nitrogen into the food web. Some is used and the excess is excreted. Mineralization Also called ammonification. Living organisms once they die are decomposed and decomposers transform the organic nitrogen tissues and waste products back into ammonium. The ammonium can be used again by plants and algae, or used by bacteria to be transformed into nitrites and nitrates. Denitrification Nitrate transforms into nitrous oxide (N2O) and eventually into atmospheric nitrogen. It’s a process done by specialized bacteria in anoxic conditions. How do humans affect the cycle? Change in plant composition on the environment. Plants who were used to live in low nitrogen environments cannot compete with bigger species with larger nitrogen requirements. Increase of atmospheric nitrogen in certain areas, rising probabilities for acid rain to occur. Leaching allows to insert nitrogen along different levels of soil and different environments thanks to water. Math problem In Haiti, farmers are being encouraged to plant mango trees to help reduce runoff and increase the uptake of water by the soil and the trees. Consider a group of Haitian farmers that decides to plant mango trees. Mango saplings cost $10 each. Once the trees become mature, each tree will produce $75 worth of fruit per year. A village of 225 people decides to pool its resources and set up a community mango farm. Their goal is to generate a per capita income of $300 per year for everyone in the village. How many mature trees will the village need to meet the goal? Each tree requires 25 m2 of space. How many hectares must the village set aside for the mango farm? Each tree requires 20 L of water per day during the 6 hot months of the year (180 days). The water must be pumped to the farm from a nearby stream. How many liters of water are needed each year to water the farm of 900 trees? Phosphorus