– NUTRIENTS

2 Chapter 3.4 in Chapman et al. Gretchen Gettel/Peter Kelderman UNESCO-IHE Institute for Water Education Online Module Water Quality Assessment

3 CONTENTS 1. Nitrogen a) Forms b) Sources number c) Reactions and cycle 2. Phosphorus a) Forms b) Sources c) Reactions and cycle

4 CONTENTS 1. Nitrogen a) Forms b) Sources c) Reactions and cycle 2. Phosphorus a) Forms b) Sources c) Reactions and cycle

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

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

7 Multiple states of N NH 4 + N2N2 N2ON2ONO 2 - NO 3 - Organic N Ammonium Gas NitriteNitrate REDUCED`N:”Kjeldahl N”OXIDIZED

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)

9 Illustration: Worldwide Growth in Fertilizer Use

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

Immobilization

12 CONTENTS 1. Nitrogen a) Forms b) Sources c) Reactions and cycle 2. Phosphorus a) Forms b) Sources c) Reactions and cycle

13 Sources of Phosphorus Weathering Rocks Major natural source of P is from rock weathering and locally important guano sources

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

16 Anthropogenic effects on the P cycle Increased inputs from: - Wastewater, including detergents - Fertilizers - Animal livestock - Erosion from poor soil management

17 Phosphorus in the press

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