Phosphorus and Eutrophication

1. Phosphorus and Eutrophication Why these are bad for water quality

2. Phosphorus molecule is negatively charged, as is clay Fe Fe Fe Fe Fe H O O O O H H H H O O O H O + P Clay mineral (Holford and Patrick, 1981; Sallade and Sims, 1997; Stumm and Morgan, 1996)

3. Phosphorus molecule bound to clay with Fe+3 bridges Fe Fe Fe Fe Fe Fe P H O O O O O O O O H H H H H H O O Fe O e- H O P Clay mineral (Holford and Patrick, 1981; Sallade and Sims, 1997; Stumm and Morgan, 1996)

4. Reductive dissolution of Fe3+ oxides releases P in wetlands Fe Fe H O O O H H P O O Fe2+ O H Clay mineral Increases Fe2+ and dissolved reactive P (Holford and Patrick, 1981; Sallade and Sims, 1997; Stumm and Morgan, 1996)

5. Points • Cation bridges hold P onto clay particles • Sediment, with P bound to it, eroded into wetlands • P on sediment (clay) can be released if Fe is the bridge holding P to clay • If Fe is reduced and dissolves, P is released to water and can move out of wetland into river.

6. P can also be released by another process Involving dissolved organic carbon (DOC) “Wetland Conditions” were created using this reactor. Soils were kept anaerobic and water was analyzed over time P dissolved from organic and mineral soils was determined

7. 1.2 Organic Soils 1 0.8 Dissolved P (ppm) 0.6 0.4 0.2 10 20 30 40 50 60 Dissolved Organic Carbon (ppm) Organic Soil materials from organic soils will release P to groundwater when converted to wetland

8. O2 - - - - - - - - - - - - - - - - - - • In saturated wetland soils, • bacteria “eat” organic matter (dead roots), and • 2) release “dissolved organic carbon” (DOC) materials into • soil water. • The DOC has a negative charge Saturated organic soil

9. Al3+ P O O O O Fe3+ Ca2+ H Phosphorus Reactions in Soils Phosphorus molecule is also negatively charged Soil colloid is negatively charged, and holds cations

10. Al3+ P O O O O Fe3+ Ca2+ H Phosphorus can be held in soils by attaching itself to cations on soil colloids When held like this P is stays in soil, and does not move with water This is common in fertilized soils. The P is held onto soil until taken up by plant

11. Al3+ P O O O O Fe3+ Ca2+ H When DOC produced in large amounts, it displaces P off soil Particle, and P goes into solution

12. Al3+ P O O O O Fe3+ Ca2+ H The dissolved P can leach from soil in groundwater

13. Dissolved P levels >0.1 ppm can cause eutrophication of surface waters and lead to fish kills in rivers 1.2 Organic Soils 1 0.8 Dissolved P (ppm) 0.6 0.4 0.2 10 20 30 40 50 60 Dissolved Organic Carbon (ppm) P concentrations Potentially Harmful To surface waters

14. Juniper Bay has large areas of organic soil that has high P levels Organic soil Mineral soil

15. P may be released here • Results suggest P may be released in organic soil • and move to perimeter ditch. • Mineral soil may re-adsorb P.

16. Eutrophication: Occurs when excess amounts of N and P enter rivers and lakes Results in excess growth of plants in waters, and leads to fish kills

17. O2 O2 O2 O2 O2 O2 O2 Good water quality Fish have plenty of O2 O2 O2 O2 O2 O2 River

18. O2 O2 O2 O2 O2 O2 O2 When P and N are added to water, algae and other Weeds grow because P and N are plant nutrients Algae bloom N N P P P O2 N P P P N N River

19. O2 O2 O2 O2 O2 When algae die, they sink to bottom and are eaten by Bacteria. Bacteria consume oxygen (electron acceptor) And eventually there is no oxygen left for fish. The fish Then die P N N Dead algae being eaten by bacteria