Nigeria's free digital learning hub. Videos, lecture notes, practice questions and leaderboards aligned with CCMAS, NBTE, NCCE, WAEC, NECO, IJMB and JAMB curricula.
Loading
Nigeria's free digital learning hub. Videos, lecture notes, practice questions and leaderboards aligned with CCMAS, NBTE, NCCE, WAEC, NECO, IJMB and JAMB curricula.
This is the complete lecture note for CHM 319 Environmental Chemistry. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: CHM 319 Course title: Environmental Chemistry Course unit: 2 Units Series 1: Elementary Cycles of Key Environmental Elements Part 1 Introduction to Biogeochemical Cycles 1.1.1 Definition and importance of biogeochemical cycles 1.1.2 General features of element cycling in the environment Part 2 The Oxygen Cycle 1.2.1 Sources and sinks of oxygen 1.2.2 Role of oxygen in atmospheric and aquatic systems Part 3 The Nitrogen Cycle 1.3.1 Nitrogen fixation and nitrification 1.3.2 Denitrification and human impacts on the nitrogen cycle Part 4 The Sulphur Cycle 1.4.1 Natural sources and transformations of sulphur 1.4.2 Anthropogenic influences and environmental effects Introduction Every living system on earth depends on the continuous cycling of elements such as oxygen, nitrogen, and sulphur. These cycles ensure that matter is reused and energy flows through the environment in a balanced way. Without them, ecosystems would collapse, and essential processes such as respiration, photosynthesis, and nutrient recycling would be disrupted. This Series will help you appreciate how these cycles operate and why they are central to environmental chemistry. The aim of this Series is to introduce you to the fundamental biogeochemical cycles of key environmental elements and to equip you with the ability to explain their processes, analyse their importance, and evaluate the impacts of human activity on them.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS We shall commence this Series by examining the concept of biogeochemical cycles, defining them and highlighting their general features. Next, we will explore the oxygen cycle, focusing on its sources, sinks, and role in atmospheric and aquatic systems. Following that, we will move on to the nitrogen cycle, considering processes such as nitrogen fixation, nitrification, and denitrification, as well as human influences. Finally, we will wrap up by studying the sulphur cycle, looking at its natural transformations and anthropogenic impacts. In conclusion, this Series will provide you with a clear understanding of how these cycles sustain life and maintain environmental balance. Series Learning Outcomes Upon completing this Series, you should be able to: define biogeochemical cycles and describe their general features, explain the importance of biogeochemical cycles in maintaining environmental balance, describe the sources and sinks of oxygen in the environment, analyse the role of oxygen in atmospheric and aquatic systems, explain the processes of nitrogen fixation and nitrification in the nitrogen cycle, describe denitrification and evaluate human impacts on the nitrogen cycle, describe natural sources and transformations of sulphur in the environment, and evaluate anthropogenic influences on the sulphur cycle and their environmental effects. 1.1 Introduction To Biogeochemical Cycles 1.1.1 Definition and importance of biogeochemical cycles Biogeochemical cycles are natural processes through which essential elements such as carbon, oxygen, nitrogen, and sulphur circulate between the atmosphere, lithosphere, hydrosphere, and biosphere. These cycles ensure that matter is reused and energy flows continuously, maintaining environmental balance. They are important because they sustain life by recycling nutrients and regulating ecological processes. Fill in the blank: Biogeochemical cycles involve the circulation of essential ______ between different spheres of the earth.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.1 General concept of biogeochemical cycles 1.1.2 General features of element cycling in the environment Element cycling is characterised by continuous movement, transformation, and reuse of matter. For example, oxygen cycles between photosynthesis and respiration, nitrogen cycles through fixation and denitrification, and sulphur cycles through volcanic emissions and microbial activity. Each cycle has reservoirs (storage areas) and fluxes (movement pathways). Human activities such as industrialisation and agriculture can disrupt these cycles, leading to environmental challenges. Fill in the blank: The continuous movement and transformation of matter in the environment is known as ______ cycling.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Plate 1.1 Examples of natural processes in element cycling Pilot questions 1.1 Define biogeochemical cycles. State one reason why biogeochemical cycles are important. Mention two spheres of the earth involved in biogeochemical cycles. Give one example of a natural process that contributes to element cycling. Explain how human activities can disrupt biogeochemical cycles. 1.2 The Oxygen Cycle 1.2.1 Sources and sinks of oxygen The oxygen cycle refers to the continuous movement of oxygen between the atmosphere, biosphere, and lithosphere. Oxygen is produced mainly through photosynthesis, a process in which green plants and algae convert carbon dioxide and water into glucose and oxygen using sunlight. Major sinks of oxygen include respiration, combustion, and oxidation reactions in rocks and minerals. The balance between sources and sinks ensures that oxygen levels remain relatively stable in the environment. Fill in the blank: The main source of oxygen in the environment is ______ carried out by green plants and algae.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Caption: Figure 1.2 Sources and sinks of oxygen in the environment 1.2.2 Role of oxygen in atmospheric and aquatic systems Oxygen plays a vital role in both atmospheric and aquatic systems. In the atmosphere, oxygen supports respiration, which is the process by which living organisms release energy from food molecules. It also enables combustion, which is the burning of fuels to release energy. In aquatic systems, dissolved oxygen is essential for the survival of fish and other aquatic organisms. The amount of dissolved oxygen depends on factors such as temperature, pressure, and the presence of pollutants. Low oxygen levels in water can lead to hypoxia, a condition that threatens aquatic life. Fill in the blank: The survival of fish and other aquatic organisms depends on the presence of ______ oxygen in water.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Plate 1.2 Role of oxygen in aquatic systems Pilot questions 1.2 Define the oxygen cycle. State the main source of oxygen in the environment. Mention two sinks of oxygen. Explain the role of oxygen in respiration. Why is dissolved oxygen important in aquatic systems? 1.3 The Nitrogen Cycle 1.3.1 Nitrogen fixation and nitrification The nitrogen cycle is the continuous movement of nitrogen between the atmosphere, soil, water, and living organisms. Nitrogen is essential for proteins and nucleic acids, yet most organisms cannot use atmospheric nitrogen directly. Nitrogen fixation is the process by which atmospheric nitrogen is converted into usable forms such as ammonia. This can occur biologically through bacteria like Rhizobium, or industrially through processes such as the Haber–Bosch method.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Nitrification is the conversion of ammonia into nitrites and then nitrates by specialised bacteria, making nitrogen available for plant uptake. Fill in the blank: The conversion of atmospheric nitrogen into usable forms such as ammonia is called ______ fixation. Figure 1.3 Nitrogen fixation and nitrification processes 1.3.2 Denitrification and human impacts on the nitrogen cycle Denitrification is the process by which nitrates are reduced back into nitrogen gas by bacteria, completing the nitrogen cycle. This ensures that nitrogen does not accumulate excessively in soils and water. However, human activities such as excessive use of fertilisers, burning of fossil fuels, and industrial emissions disrupt the natural nitrogen cycle. These activities increase nitrogen oxides and nitrates in the environment, leading to problems such as eutrophication, acid rain, and greenhouse gas emissions. Fill in the blank: The process that converts nitrates back into nitrogen gas is known as ______.
This is the opening of the note. Read the full note or download the PDF to continue.
