Understanding Phosphorus Dynamics and Controls to Better Manage the Turbid Minnesota River System

Transcription

1 Understanding Phosphorus Dynamics and Controls to Better Manage the Turbid Minnesota River System William F. James US Army Corps of Engineers Engineer Research and Development Center Eau Galle Aquatic Ecology Laboratory Spring Valley, Wisconsin Catherine E. Larson Metropolitan Council Environmental Services 39 Robert St. North St. Paul, Minnesota 5511 David L. Smith US Army Corps of Engineers Engineer Research and Development Center Vicksburg, Mississippi 3918 July 29-3 rd National Conference on Ecosystem Restoration Los Angeles, California

2 Metropolitan Council Environmental Services U.S. Army Engineer District, St. Paul Engineer Research and Development Center System-Wide Water Resources Program

3 Most Polluted River System in the United States?

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5 Forage Crop 1% Forest 3% Urban 5% Minnesota River Water 3% Other 5% Land Use Practices Row Crop 74% Mississippi River St. Croix River Urban 8% Water 8% Other 12% Row Crop 21% Urban 5% Water 5% Other 1% Row Crop 15% Forage Crop 15% Forest 36% Forage Crop 15% Forest 5%

6 St. Croix R. Mississippi R. Minnesota R. TN Export (kg ha -1 y -1 ) TP Export (kg ha -1 y -1 ) TSS Export (kg ha -1 y -1 )

7 Flow Suspended Sediment ST. CROIX R. 23% MISSISSIPPI R. 38% ST. CROIX R. 2% MISSISSIPPI R. 12% MINOR INFLOWS 2% MINNESOTA R. 34% MINOR INFLOWS 4% MINNESOTA R. 84%

8 Minnesota R. Confluence with the Mississippi R. TSS (mg/l) 2 1 Upstream Downstream Tur rbidity (NTU) Total P (mg/l).2.1 SRP (mg/l).2.1 Mar Apr May Jun Jul Aug Sep Oct Nov 1996 Mar Apr May Jun Jul Aug Sep Oct Nov

9 Objectives Examine P loading and P dynamics as affected by biotic (phytoplankton) and abiotic (equilibrium) controls in relation to hydrology (i.e., travel time) Estimate the recycling potential of particulate P and impact on downstream eutrophication after deposition Use information for watershed and river TMDL modeling

10 Study site Station locations Minnesota River WWTPs Creeks Generating plant Lower Minnesota River Confluence with Mississippi River Downstream boundary River Mile 3.5 Riley Creek Purgatory Creek Seneca WWTP Chaska Creek Bluff Creek Blue Lake WWTP Nine Mile Creek Black Dog Power Generating Plant Willow Creek Eagle Creek Credit River Carver Creek Upstream boundary River Mile 39.4 Sand Creek Miles

11 Discharge (m3 s-1) 12 a) TSS (mg L-1) 1 b) RM 3.5 RM Particulate P (mg L-1) Viable chlorophyll (ug L-1) 3 c) d) Soluble reactive P (mg L-1).4 e) O D F A J 24 A O D F A J 25 A O D F A J 26 A

12 Particulate Phosphorus Dynamics

13 RM 3.5 RM Flow (m 3 s -1 ) Particulate P (mg g -1 ) Chlorophyll (mg g -1 ) Organic Matter (mg g -1 )

14 Allochthonous Particulate Phosphorus Equilibrium P characteristics Suspended sediment collected during high flow Subjected to soluble P concentrations ranging from to 1 mg L -1 Change in soluble P after 24 hours used to calculate P adsorption or P desorption Fractionation into biologically labile and refractory P components Loosely-bound, iron-bound, and labile organic P Aluminum-bound, calcium-bound, and refractory organic P

15 P Equilibrium Characteristics for Allochthonous Suspended Sediment 2 SRP (mg kg -1 ) Adsorption Desorption 1 Equilibrium P concentration Equilibrium SRP (mg L -1 )

16 Allochthonous Particulate P Equilibrium Characteristics and Fractions Variable Mean SE Ambient SRP (mg L -1 ) EPC (mg L -1 ) k d (mg kg -1 ) S o (mg kg -1 ) 5 9 S max (mg kg -1 ) Loosely-bound P (mg kg -1 ) Iron-bound P (mg kg -1 ) Labile organic P (mg kg -1 ) 6 3 Aluminum-bound P (mg kg -1 ) 59 5 Calcium-bound P (mg kg -1 ) 2 13 Refractory organic P (mg kg -1 )

17 .4 RM 3.5 a) b) SR P (mg L -1 ) RM TSS loading (Mg d -1 ) PP loading (kg d -1 )

18 Equilibrium P Concentration System EPC (mg L -1 ) lower Minnesota River (USA).117 Present study Reference Lake Pepin sediment (USA).155 James and Barko (24) Redwood River (USA).7 James et al. (22) Eau Galle River (USA).129 James and Barko (25) Colorado River (USA).4 Mayer and Gloss (198) Bermejo River (Argentina).6 Carignan and Vaithiyanathan (1999) Paraguay River (Argentina).2-.9 Carignan and Vaithiyanathan (1999) Paraná River (Argentina) Carignan and Vaithiyanathan (1999) Bear Brook (USA).2 Meyer (1979) NY wooded streams (USA) <.2 Klotz (1985) Lower Mississippi River (USA).18 Wauchope and McDowell (1984) Xiangxi River (China).1 Chang-Ying et al. (26)

19 Sequential Extraction Loosely-bound PP Iron-bound PP Variable Extractant Recycling Potential 1 M ammonium chloride.11 M sodium bicarbonate-dithionate Biologically labile; can be recycled via eh and ph reactions and equilibrium processes. Biologically labile; can be recycled via eh and ph reactions and equilibrium processes. Biologically labile; recycled via bacterial Labile organic/ polyphosphate PP Persulfate digestion of the NaOH extraction mineralization of organic P and mobilization of polyphosphates stored in cells. Aluminum-bound PP Calcium-bound PP Refractory organic PP.1 N sodium hydroxide.5 N hydrochloric acid Persulfate digestion of remaining particulate P Biologically refractory; generally unavailable for biological use and subject to burial. Biologically refractory; generally unavailable for biological use and subject to burial. Biologically refractory; generally unavailable for biological use and subject to burial.

20 P Fractionation Characteristics for Allochthonous Suspended Sediment Refractory organic P (mg kg -1 ) 16% Loosely-bound P (mg kg -1 ) 18% Calcium-bound P (mg kg -1 ) 25% Aluminum-bound P (mg kg -1 ) 8% Labile organic P (mg kg -1 ) 7% Iron-bound P (mg kg -1 ) 26%

21 Implications of Allochthonous Particulate P Transport Influences aqueous soluble P concentration via equilibrium reactions 2 Nürnberg (1988) Transport and deposition of biologically labile PP to navigation pools of the UMR Potential for high rates of diffusive P flux after deposition 17 mg m -2 d -1 Anoxic release rate (mg m -2 d -1 ) Iron-bound P (ug g WW -1 )

22 Soluble Phosphorus Dynamics

23 Relative WWTP contribution Total P load at RM 3.5 (Mg d -1 ) a) b) lnchla = -.44 lndischarge r 2 =.43 P <.1 RM 3.5 RM Discharge (m 3 s -1 ) Viable chlorophyll (µg L -1 )

24 Ch hlorophyll (ug L -1 ) lnchla = SRP r 2 =.35 P <.1 RM 3.5 RM SRP (mg L -1 )

25 Soluble P Budget Low Versus High Flow Discharge Input Output Uptake Chlorophyll (m 3 s -1 ) Load (kg d -1 ) Conc. (mg L -1 ) Load (kg d -1 ) Conc. (mg L -1 ) Load (kg d -1 ) Efficiency (%) Conc. (ug L -1 ) 8/16/ /16/ /9/ /6/ Biotic Versus Abiotic Control of SRP Concentration

26 Conclusions Allochthonous TSS buffers soluble P at a high equilibrium concentration during runoff and high flow A high percentage of the allochthonous particulate P is biologically labile and transported to navigation pools of the Upper Mississippi River where it can become deposited and recycled As flows decline, P dynamics become regulated more by point source inputs of soluble P, algal uptake, and transformation to particulate P