What you’ll learn8 learning objectivesChoose one objective for a focused lesson, or study the complete topic.4.4.1Water pollution sources• Sewage, agricultural run-off, industrial effluent• Urban run-off, solid waste disposal, oil spillsSyllabus objective4.4.2Plastic debris accumulation• Marine environments• Oceanic gyres, microplastics enter food chainSyllabus objective4.4.3Water quality measurement• Chemical, physical, biological characteristics• Water quality index (WQI)• Parameters: dissolved O₂, pH, temperature, turbidity, nitrates, phosphates, metalsSyllabus objective4.4.4Biochemical oxygen demand (BOD)• Dissolved oxygen required by microorganisms for decomposition• mg O₂ per litre in 5 days at 20°CSyllabus objective4.4.5Eutrophication• Mineral nutrient inputs (nitrates, phosphates)• Excessive phytoplankton growth (algal blooms)Syllabus objective4.4.6Eutrophication sequence• Impacts and changes to aquatic systemSyllabus objective4.4.7Eutrophication and ecosystem services• Eutrophication can substantially impact ecosystem services• Eutrophication can affect services associated with fisheries, recreation, aesthetics and healthSyllabus objective4.4.8Eutrophication management levels• Eutrophication can be addressed at three different levels of management• These three levels of management are:• the reduction of human activities that produce pollutants—e.g., alternatives to current fertilizers and detergents• the reduction of the release of pollution into the environment—e.g., treatment of wastewater to remove nitrates and phosphatesSyllabus objective