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Eutrophication for a Biology class/Chemistry class. Unit 1.4.9 of biology syllabus and Section 9.3 of chemistry syllabus. Eutrophication. Definition of Eutrophication. • Eutrophication is the addition of nutrients to water which results in excessive growth of algae. (Algal bloom) • The nutrients are phosphates (PO43-) and nitrates (NO3-). • When the algae die, their breakdown by aerobic bacteria results in deoxygenation (removal of dissolved O2 from the water) • Oxygen loss results in the death of fish. Eutrophication Natural Artificial Natural Eutrophication. • Natural eutrophication occurs when nitrates and phosphate are added, slowly and over long periods of time, to rivers and lakes. Artificial Eutrophication • • • • • Happens much faster than natural. Is a result of human activity. Is caused by untreated sewage. Detergents that are high in phosphates. Is also caused by fertilisers being leached from farms into lakes. • Nitrates and phosphates are present in these pollutants. Some Questions. • Q. What is a form of water pollution that causes an algal bloom in the water? • A. Eutrophication. • Q. Identify ions which are responsible for eutrophication. • A. Nitrates (NO3-) and phosphates (PO43-). • Q. Name any pollutant that contains either of these ions. • A. Untreated sewage or fertilisers. Some revision questions for chemistry. • Q. What is the name giving to the test for the nitrate anion? • A. The brown ring test. • Q. When testing for the phosphate ion in aqueous solution, what is the colour of the positive result? • A. Yellow. • Q. At what stage of sewage treatment are nitrate and phosphate ions removed? • A. Tertiary. Some revision questions for biology. • Q. Define pollution. • A. Pollution is the addition of harmful material to the natural environment, usually as a result of human activity. • Q. Name any one water pollutant. • A. Untreated sewage or slurry from farms. • Q. How may either of these forms of pollution be controlled? • A. Sewage is treated in modern treatment plants before its discharge into a river or lake. Some revision questions for biology. • Q. How may pollution caused by slurry run off from farms be controlled? • The slurry is stored in leak proof pits until there are dry weather conditions. It is spread onto fields where it is less likely to be leached by rain. • The slurry is broken down and nutrients recycled back into the soil. Describe the ecological impact of the addition of fertilisers or farm slurry to a river or lake. • Excessive amounts of nitrates and phosphates are added. • Massive growth in algae. • Less light reaching plants living at deeper levels in the lake. • Aerobic bacteria remove dissolved oxygen as they break down the algae. • Many species of fish die. • Coarse fish can survive and their numbers increase to levels where they should not be. • An imbalance in fish and plant numbers results.