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1 - 2.3 – NUTRIENTS
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2 Chapter 3.4 in Chapman et al. Gretchen Gettel/Peter Kelderman UNESCO-IHE Institute for Water Education Online Module Water Quality Assessment
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3 CONTENTS 1. Nitrogen a) Forms b) Sources number c) Reactions and cycle 2. Phosphorus a) Forms b) Sources c) Reactions and cycle
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4 CONTENTS 1. Nitrogen a) Forms b) Sources c) Reactions and cycle 2. Phosphorus a) Forms b) Sources c) Reactions and cycle
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5 Forms of Nitrogen Dissolved Forms (<0.45 µm): Ammonia (NH 3 ) and Ammonium (NH 4 + ) Nitrate (NO 3 - ) and Nitrite (NO 2 - ) Dissolved organic nitrogen (DON) Total N = all Dissolved + Particulate forms in a water sample Gaseous Forms: N 2 (in air: 78%) Nitric oxide (NO) and nitrous oxide (N 2 O) Particulate Forms (> 0.45 µm): Detritus (dead), and living matter (algae; zooplankton,..), usually organic N
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6 In aerobic waters converted to nitrate (nitrification: NH 4 + NO 3 - ) Indicator of (domestic) pollution; values may be > 5 mg NH 4 -N/L for polluted streams Ammonium/ammonia (NH 4 + / NH 3 ) Equilibrium between NH 4 + / NH 3 NH 4 + NH 3 +H + pH < 9.5: dominantly (non-toxic) NH 4 + pH > 9.5 dominantly as (toxic) NH 3, which tends to volatilize (goes to the atmosphere) and become a source of atmospheric deposition
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7 Multiple states of N -30+1+3+5 NH 4 + N2N2 N2ON2ONO 2 - NO 3 - Organic N Ammonium Gas NitriteNitrate REDUCED`N:”Kjeldahl N”OXIDIZED
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Industrially fixed (mainly fertilizer) Total reactive N N-fixing crops Fossil fuel combustion Period of explosive increase of coastal eutrophication Human activities have greatly altered the N cycle, accelerating the rate of N 2 fixation in landscapes (Galloway et al. 2004)
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9 Illustration: Worldwide Growth in Fertilizer Use
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10 Sources of Nitrogen to Aquatic Ecosystems Anthropogenic N sourcesNatural N sources Natural runoff and inputs from natural sources (e.g. leaves, soil leachates) Biological Nitrogen Fixation Atmospheric deposition, N- fixation Wastewater (“point sources”) Urban &agricultural runoff Import of food and animal feed to basins Atmospheric deposition from fossil fuel burning, NH 3 loss to the atmosphere from “bioindustry” Weathering Rocks
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Immobilization
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12 CONTENTS 1. Nitrogen a) Forms b) Sources c) Reactions and cycle 2. Phosphorus a) Forms b) Sources c) Reactions and cycle
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13 Sources of Phosphorus Weathering Rocks Major natural source of P is from rock weathering and locally important guano sources
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14 Forms of Phosphorus Dissolved Phosphorus (< 0.45 µm) - Soluble Reactive Phosphorus (SRP) ≈ Ortho-phosphate (PO 4 3-, HPO 4 2- …) - Dissolved organic phosphorus (DOP) Particulate Phosphorus - Particulate organic phosphorus (POP) - Particulate inorganic Phosphorus (PIP) Total Dissolved P = Sum of organic and inorganic phosphorus Total P = Includes dissolved and particulate forms, including phytoplankton and smaller zooplankton
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16 Anthropogenic effects on the P cycle Increased inputs from: - Wastewater, including detergents - Fertilizers - Animal livestock - Erosion from poor soil management
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17 Phosphorus in the press
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18 External Inputs: Example of Chesapeake Bay, USA most nutrients input from agriculture or point sources almost 50 % of P comes from agriculture Point sources (discharge pipes houses, industries,..): 23-34% for N and P, respectively Other
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