1st Febuary lec : atmosphere

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University of Toronto St. George
School of Environment
Jack Parkinson

• Fossil fuel = decomposition of living organisms --> liquid or gas, they’re actually fossils made through millions of years We use them very quickly. Water cycle: slide7 The earth = 97% water = ocean • Moves water around the globe, • water from ocean evaporates b/c of solar energy ends up in atmosphere • Makes up clouds • Precipitate in the form of rain/snow • Makes way back to the ocean Complete recycle of water back to the eco system. Nitrogen cycle: slide 8 Proteins and DNA, what makes who we are, requires nitrogen which is an important element 78% of the atmosphere is made out of We’d think that nitrogen wouldn’t run out or have a shortage, but nitrogen in our atmosphere is not in a biologically useable forms • Nitrogen in our atmosphere cannot be changed into proteins for us to use it, biological useable form Nitrogen cannot be used unless converted into useable forms , after it goes through ammonification then it can be used in a biological way. It has to go through a complicated five steps, details will be in the text book go check it In the past, b/c nitrogen in the atmosphere isn’t in a biologically useable form we relied on bacteria to convert the nitrogen into the biological useable form which is called nitrogen fixation There’re some plants that had this bacteria in their root structures that were able to do this miraculous chemical transformation to convert it to ammonia, a more usable form, which would take it through other four stages of chemical transformation. Lots of nitrogen in the air, but not in useable form unless it’s converted. Understand how atmosphere affect nitrogen, go through the nitrogen fixation and how it goes back to the cycle and how it gets back into the atmosphere. www.notesolution.com Human activities significantly altered the nitrogen cycle , we saw how nitrogen could be incorporated to our agricultural system. From rarly 20th cen, our chemical advance allowed us to do what bacteria was doing for us before , that is converting nitrogen into useable forms This altered the landscape and how nitrogen was incorporated to the system --> great growth in agriculture, fertilizers have high percentage of nitrogen b/c it’s needed for growth to happen Nitrogen in the atmosphere will be doubled in 25 yrs, this is an enormous amount Impact? Concept of Eutrophication, richness in the water body, an excessive nutrition Many plants will grow, which will decompose and cause the problem creating oxygen sucked up by decomposition process. Makes water less easy to clean up or consume Smog, acid rain and formation of green house gases, would also be a factor other than carbon dioxide. Phosphorus cycle (another fertilizer) • Big diff b/t this and nitrogen, phosphorus is not in our atmosphere nor can be altered to be created Yet still an imp. Element in our dna and atp (chemical energy). Basic understanding of how phosphorus works through food chain is, we don’t get it from atmosphere instead, we find it in the land. It’s in the earth’s systems. Phosphates move through the food chain Organism eat plant -> organism eat other organism -> -> organism dies -> phosphorus goes back into the land = Organisms making an access to phosphate b/c it’s not in our atmosphere it’s in a patchy distribution There’re areas that doesn’t have so much phosphorous this is why plants grow abundantly when it has phosphorus in fertilizer When it’s trapped in the lithosphere it won’t move like nitrogen that’s in the atmosphere but will stay there Once it ends up in ocean, seabed that’s very deep that phosphorus will be tied up So the cycle can take a very long geological time Although having an abundance of phosphorus is a good thing, over-abundance causes\ similar things as things caused by over abundance of nitrogen. www.notesolution.com MESSAGE: All these Cycles cycle through, they have varying length of time but humans have disturbed these cycles and destroyed it The atmosphere • Gaseous envelope surrounding the earth Oxygen and nitrogen combined together makes up 99% of our atmosphere Think of multi layer cake, it consists of four layers. Troposphere (closes to us) Average distance ground -> 12km above it Thickness depends on where you are on the earth 16km thick in equator while 8km thick at the pole As we go up troposphere it goes cold up to -52, this is why it gets colder in the mountains Ozone in troposphere is identified as smog, bad Stratosphere ozone resides, jets fly Layer of atmosphere that absorbs the most of sun’s Damaging ultra violet ray Starts roughly 11km and 50km up Temp. Actually increases up, you’d think the that it Will go colder as we go up, but it’s not Natural protective ozone layer, good: Blocks out nasty uv radiation, ozone holes -> uv radiation come through Mesosphere 50-80km sea level You can see meteor Very low density, very thin Thermosphere • Temp. diff do not allow atmosphere layers to become mixed As you go up, it goes closer to the sun = higher temp • Although same chemicals could appear in each layer
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