Study Guide

Environmental Chemistry - Common Mistakes

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Common Mistakes

The Air Up There

To remember thelayers of the atmosphere in order, remember that the squirrel monkey took everything = troposphere, stratosphere, mesosphere, thermosphere, exosphere.

Aerosols are fickle and their effects on climate, clouds, and atmospheric chemistry depend on location and type of aerosol.

All aerosols serve as seeds for clouds. No aerosols = no clouds.

A layer of aerosols in the stratosphere (mostly made of sulfur) affects the amount of sunlight absorbed and reflected.

Dark aerosols decrease albedo and lead to warmer temperatures, while light aerosols reflect light and have a cooling effect. To remember this, think about the hottest day in the summer and which color t-shirt would keep you cooler: black or white? You'd choose the white t-shirt (unless you were concerned about sunburn) because it would keep you cooler. Lighter colors = cooler temperatures. CIRES has an explanation on the effect of aerosols on climate. It's not as fun as reading our translation of this scientific topic, but it's only 2 minutes and those NOAA scientists are reasonably intelligent.

Biogeochemical Cycles

The easiest way to understand any of the biogeochemical cycles is to study the diagrams. It would be helpful to print out blank versions of the diagrams and practice filling them in. If you understand the diagram, you understand the cycle.

For the nitrogen cycle: nitrogen fixation = N2 → NH3 (ammonia)

nitrification = ammonia → nitrite → nitrate (nitrify is changing the names to ones that include nitr.)

denitrification = terrestrial nitrogen → atmospheric nitrogen (N2)

This probably would be a good cycle to try out memory tricks or mnemonic devices.

More About Biogeochemical Cycles

It's easy to mix up the players in this ozone smack down. The Round 1 run-down is designed to help you remember who is a friend and who is a foe.

Round 1 Run-Down:

Team Dr. Jekyll, also known as stratospheric ozone:

1. NO2: removes Cl as a contender by reacting with ClO to form ClONO2
2. OH: reacts with NO to form HNO3
3. Rain: many ozone opponents are removed via rainfall
4. O2: no O2, no O3

Team On the Fence:

1. Chapman Reaction Sequence: synthesize, decompose, synthesize, decompose
2. UV Radiation (see #1)

Team Hyde
1. Free Radicals: must destroy ozone…must destroy ozone
2. Chlorine: cause of the infamous hole in the ozone layer as proven by Captain Data's brave flight through the Antarctic ozone hole

More About Ozone

Round 2 Run-Down:

Team Hyde

1. Hydrocarbons, VOCs: both react with ozone to form smog
2. NOx: both NO and NO2 contribution to the formation of tropospheric ozone
3. Motorized vehicles: in addition to taking you to the library to pick up the newest vampire/werewolf/timid girl who changes the world while falling in love trilogy, cars also release chemicals that contribute to smog and tropospheric ozone

Team On the Fence:

1. Sunlight: and let there be light. Without sunlight, ozone can neither be created nor destroyed

Team Jekyll

1. NO2 to NO ratio: if no other reactants contribute, ozone production is low because it's equivalent to this ratio
2. OH: the scrubbing brush of the atmosphere. OH removes NO2 within a day, decreasing tropospheric ozone production

More About Tropospheric Ozone

Most of the time, rain is acidic, but it is not called acid rain until the pH dips below 5.5.

Soils buffer acidic rain, either by exchanging cations in the soil, mobilizing aluminum, or releasing OH- ions.

Rain in different places has a different composition and we can use its composition to determine its origin.

More About Rain

It's easy to think that the greenhouse effect and global warming are one and the same. The greenhouse effect is what makes earth livable. Without it, earth would be so cold that all water would be frozen. It would be hard to live like that.

Global warming is the increase in the earth's average temperature, mostly due to the emission of greenhouse gases. The greenhouse effect is important for life on earth, but the problem occurs when too many greenhouse gases are added to the atmosphere and the earth heats up too quickly, not giving life the time to adapt. The key is the rate of warming.

The earth has always gone through natural cycles of interglacial (warm) and glacial (cold) periods, but earth's temperature is increasing at a rate that is too high for most life. Global warming is like the greenhouse effect on anabolic steroids.

So about those greenhouse gases…

The GWP gives you the "strength" of a greenhouse gas. Scientists use the atmospheric lifetime and the gas's ability to absorb infrared radiation to determine the GWP. Like a visiting family member, the longer the gas sticks around, the higher the GWP.

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