ENVI CHEM

• Troposphere below an altitude of 12 km

  The temperature decreases from 290 K to 215 K as altitude increases.
• Stratosphere 10 km – 50 km

  The temperature increases from 215 K to 275 K.
• Mesosphere (50 km – 85 km)

  The temperature decreases (275 K to 190 K).
• Thermosphere (>85 km)

  The temperature increases
• Photoionization is the ionization of molecules (and atoms) caused by radiation.
• Photochemical smog is the result of photochemical reactions on pollutants.
• Eutrophication is the increase in dead and decaying plant matter resulting from excessive plant growth.
• Seawater has a salt concentration too high for drinking
• Desalination is the removal of salts from seawater or brackish water.
• Use of Renewable Feedstocks - A raw material or feedstock should be renewable whenever technically and economically practical
• Prevention - It is better to prevent waste than to clean it up after it has been created
• Atom Economy - Methods to make chemical compounds should be designed to maximize the incorporation of all starting atoms into the final product.
• Less Hazardous Chemical Syntheses - Wherever practical, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment.
• Designing Safer Chemicals - Chemical products should be designed to minimize toxicity and yet maintain their desired function.
• Safer Solvents and Auxiliaries - The use of auxiliary substances (e.g., solvents, separation agents, etc.) should be eliminated wherever possible and, if used, should be as nontoxic as possible.
• Design for Energy Efficiency - Energy requirements of chemical processes should be recognized for their environmental and economic impacts and should be minimized. If possible, chemical reactions should be conducted at room temperature and pressure.
• Reduce Derivatives - Unnecessary derivatization should be minimized or avoided if possible, because such steps require additional reagents and can generate waste.
• Catalysis - Catalytic reagents (as selective as possible) improve product yields within a given time and with a lower energy cost compared to noncatalytic processes and are, therefore, preferred to noncatalytic alternatives.
• Design for Degradation - Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment.
• Real-Time Analysis for Pollution Prevention - Analytical methods need to be developed that allow for real time, in-process monitoring and control prior to the formation of hazardous substances.
• Inherently Safer Chemistry for Accident Prevention - Reagents and solvents used in a chemical process should be chosen to minimize the potential for chemical accidents, including releases, explosions, and fires.
• Water containing a high concentration of Ca2+ and Mg2+ and other divalent cations is called hard water
• Aeration - Air hastens the oxidation of any organic material that may be present.
• Coarse filtration - This occurs as water is taken from a lake, river, or reservoir and passed through a screen.
• Sedimentation - Water is allowed to stand so that solid particles (e.g., sand) can settle out.
• Sand filtration - Water is filtered through a sand bed to remove Al(OH)3 and anything it trapped in it.
• The salinity of seawater is defined as the mass (in grams) of dry salts present in 1 kg seawater.
• Dissolved oxygen is one of the most vital indicators of water quality.
• Groundwater: accounts for about 20% of the world’s freshwater.
• Freshwater : natural waters that have low concentrations of dissolved salts and solids.

  (includes waters of lakes, rivers, ponds, and streams)