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Sources of Oxygen Demand in the Lower San Joaquin River, California

Sources of Oxygen Demand in the Lower San Joaquin River, California. P. W. Lehman, J. Sevier, J. Giulianotti & M. Johnson. California Department of Water Resources. 122 20’ N. 122 00’ N. 121 40’ N. 121 20’ N. Sacramento. CALIFORNIA. 38 20’ W. River. o. e. River. m. a. r. c. a.

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Sources of Oxygen Demand in the Lower San Joaquin River, California

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  1. Sources of Oxygen Demand in the Lower San Joaquin River, California P. W. Lehman, J. Sevier, J. Giulianotti & M. Johnson California Department of Water Resources

  2. 12220’ N 12200’ N 12140’ N 12120’ N Sacramento CALIFORNIA 3820’ W River o e River m a r c a S San Stockton 3800’ W Antioch Carquinez straight Mossdale San Francisco Bay

  3. Current situation: There has been little change in dissolved oxygen concentration in the channel despite enhanced management and a decrease in phytoplankton biomass

  4. Frequency of values below 5 mg l-1

  5. Chlorophyll a decreased over time in the channel

  6. Question: What are the primary sources of oxygen demand in the Deep Water Channel near Stockton?

  7. Study Methods biweekly or monthly sampling July - November 2000 & 2001 discrete variables: Primary productivity : in situ dissolved oxygen light and dark bottle technique Nutrient concentrations chlorophyll a and phaeophytin concentration BOD tests continuous variables vertical profiles with YSI 6600 sonde continuous flow continuous water quality

  8. MC DONALD MC DONALD o 121 20 ’ N ISLAND ISLAND Calaveras River Calaveras River TC TC o 80 00 ’ W STOCKTON STOCKTON San Joaquin River San Joaquin River L48 L48 TB TB RR RR Deep Water Channel Deep Water Channel CP CP Water Treatment Plant Rough and Ready Rough and Ready Island Island ROBERTS ROBERTS ISLAND ISLAND Middle River N N MD MD 4 km 4 km TC Turner Cut RR Rough and Ready Island L48 Navigation Light 48 San Joaquin River San Joaquin River TB Turning Basin CP Channel Point MD Mossdale VN Vernalis VN o 121 20 ’ N o 80 00 ’ W Water Treatment Plant Middle River N N 4 km VN

  9. Findings

  10. Dissolved oxygen in DWSC

  11. Dissolved oxygen upstream

  12. Oxygen depletion was not caused by stratification

  13. Oxygen demand was not caused by phytoplankton respiration

  14. Oxygen demand was caused by nitrification

  15. Pearson Correlation Coefficients(n=103) TBOD & NBOD 0.86 NBOD & ammonia0.93 NBOD & organic N0.34 TBOD & ammonia 0.78 TBOD & CBOD 0.62 TBOD & chlorophyll 0.59

  16. Stepwise Regression Dissolved ammonia + carbonaceous BOD 60% 30% Year n R2 2000 100 0.91 2001 85 0.73 2000 + 2001 185 0.83

  17. Where does the ammonia come from ?

  18. NBOD was correlated with ammonia load from treatment plant

  19. NBOD at Rough and Ready varied with the ammonia load from the treatment plant

  20. Total nitrogen load was higher from upstream

  21. Mass Balance Model Object: Determine the largest source of dissolved ammonia in the channel

  22. Simple mass balance model Daily dissolved ammonia load into the ship channel from the treatment plant and upstream = 1) daily load of dissolved ammonia from each source + 2) daily load of dissolved ammonia from the oxidation of the organic nitrogen load from each source + 3) daily load of dissolved ammonia from the oxidation of residual organic nitrogen from previous day from each source

  23. Ammonification rate

  24. Upper boundary condition: all organic nitrogen oxidized at ammonification rate for chlorophyll (highest rate)

  25. Chlorophyll was a small percent of the organic nitrogen load

  26. Lower boundary condition: only the organic matter associated with live chlorophyll was oxidized

  27. Summary • Oxygen demand in the channel was primarily caused by nitrification • The treatment plant could be the primary cause of nitrification in the channel on a daily basis even though it had a small ammonia load because it was a direct source of dissolved ammonia for bacterial oxidation • The relative contribution of ammonia from the treatment plant and upstream to ammonia in the channel was a function of residence time, ammonification rate, direct loads and load composition

  28. Take home message The oxygen demand produced from the direct load of dissolved ammonia from the treatment plant could have a greater impact on daily oxygen demand in the channel than the oxidation of organic nitrogen from upstream because of the slow oxidation rate and low reactivity of upstream organic matter

  29. Net transport of phytoplankton mass decreased downstream

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