Module 2: Oxygen and Ozone (Lesson 2) PDF

D ULE 2 : MO OXYGEN AND OZONE LESS O N 2 DO, BOD, AND PH WHAT IS OXYGEN Oxygen is a chemical element – a substance that contains only one type of atom. Its official chemical symbol is O, and its atomic number is 8, which means that an oxygen atom has eight pr...

D ULE 2 : MO OXYGEN AND OZONE LESS O N 2 DO, BOD, AND PH WHAT IS OXYGEN Oxygen is a chemical element – a substance that contains only one type of atom. Its official chemical symbol is O, and its atomic number is 8, which means that an oxygen atom has eight protons in its nucleus. Oxygen is a gas at room temperature and has no colour, smell or taste. It is the third most abundant element in the universe after hydrogen and helium. QUIZ SURPRISE! How many percent does oxygen take on Earth’s Composition? WHAT IS OZONE Ozone is a minor component of the Earth’s Atmosphere. 0.02 to 0.1 ppm based on volume concentration. Ozone absorbs UV (UltraViolet) radiation. QUIZ SURPRISE! What is the purpose of the ozone layer? CHAPMAN’S REACTION CHAPMAN’S REACTION SOURCES OF FREE OXYGEN Free oxygen is a precursor to ozone. It originates from the stratosphere and troposphere. STRATOSPHERE Photochemical Reaction: UV photons below 242 nm cause a reaction, breaking O₂ into free oxygen atoms (O). Equation: O₂ + hν → O + O UV light production depends on season, latitude, and altitude. Greater photochemical O production occurs where solar radiance is highest (equator and high altitudes). TROPOSPHERE O₂-Dissociating UV Radiation: Depletes above 30 km. Ozone Formation: Ozone is produced at nearly the same rate as oxygen depletion. Photochemical Dissociation of NO₂: A key source of oxygen in the polluted troposphere. Equation: NO₂ + hν → NO + O OZONE VARIATION Ozone concentration increases with altitude, providing protection from harmful UV radiation. CONCEPT OF DISSOLVED OXYGEN Measures the amount of oxygen dissolved in water, essential for aquatic life. High dissolved oxygen in rapidly moving bodies of water, lower in stagnant water. Oxygen in water is required by fish and zooplankton for survival. FACTORS AFFECTING DISSOLVED OXYGEN Temperature: Dissolved oxygen is inversely proportional to water temperature. Lower in warm water, higher in cool, moving water. Organic Matter Decomposition: Consumes oxygen, reducing levels in eutrophic conditions, endangering aquatic life. Photosynthesis: Primary process producing oxygen in aquatic systems. Pass the Ball until the music stops WHAT IS BOD Biological Oxygen Demand is a measure of the oxygen used by microorganisms to decompose waste. At high BOD levels organisms such as macro invertebrates that are more tolerant of lower dissolved oxygen may appear and become numerous. Organisms that need higher oxygen will not survive.  ??? WHAT IS PH? WHAT IS PH pH is universally used to express the intensity of the acid or alkaline condition of a solution. It is a way of expressing the hydrogen ion concentration of water or solution. In 1909, Sorenson proposed to express pH values in terms of their negative logarithm. The pH scale is represented below as ranging from 0 - 14, with pH 7 representing absolute neutrality. THANK YOU!