Determining Ideal Nitrogen Loads for Rerouted … · Rerouted Agricultural Drainage Water into Restored Forested Wetlands: ... Summer! Fall! Winter! Fall! Summer! ... DOC (mg L-1)

Determining Ideal Nitrogen Loads for Rerouted Agricultural Drainage Water

into Restored Forested Wetlands: A Experimental and Modeling Approach

Tiffany L. Messer, Dr. Michael R. Burchell, II, and Dr. François Birgand,

2014 WRRI Annual Conference March 20th, 2014

Background

Hyde County Wetland Restoration Project overview

Existing Farmland

Current Pumped Drainage

Proposed Rerouted Drainage

Restored Wetlands

Swan Lake

Pamlico Sound

Alligator River National Wildlife Refuge

Stakeholder Goals and Concerns v Hydrologic improvements to the

restoration and surrounding refuge lands v Reduce pumping to Pamlico Sound v Improve wetland ecosystem structure v Reverse subsidence v Reduce threat of fire v Combat SLR/salt water intrusion

v Concern: Water quality of diverting drainage water through wetlands towards nitrogen-limited receiving waters (Swan Lake)

Forested Wetland Studies v  Previous studies in the Albemarle-Pamlico peninsula have

reported wetlands that received agricultural drainage water effectively store water and reduce nutrients up to 97% (Ardόn et al., 2010; Bruland et al., 2006; Chescheir et al., 1991).

v Available studies have evaluated wetland performance at the field scale after pumping to those areas began, with little control of how the areas were loaded with drainage water

(Bruland et al., 2006; Chescheir et al., 1991).

v  Studies are necessary to allow for a mass balance approach to accurately predict N transformations and appropriate hydraulic loads within wetland systems (Kovacic et al., 2000).

Research Objectives

Research Objectives 1.  Utilize mesocosm-scale wetlands with restoration site

soils to determine the fate and assimilation potential of nitrate.

2.  Improve our understanding of the fate of applied nitrate in these systems with advanced analytical techniques

•  Continuous WQ probes

3.  Determine ideal volumes of water and associated nutrient loads that can be diverted away from the Pamlico Sound and into the restored wetland.

Focus: NO3

—N Reduction: Denitrification or Plant Uptake? ♦  Microbial denitrification allows for complete removal of NO3

--N from the system

♦  Denitrification requires: –  Anoxic conditions –  Nitrate source –  Suitable pH conditions

–  Carbon source –  Suitable temperature

DNRA

OrgN

N2

NO3-

NO N2O NO2

- NH4+

NH3

Mineralization

Dep

ositi

on

Immobilization

Nitrification

Den

itrifi

catio

n D

enitr

ifica

tion

NO3-

Materials and Methods

Wetland Nitrogen Fate Investigated Criteria

Soil redox & Antecedent Conditions

Carbon Availability

Temperature

Denitrification Plant Uptake/ Soil Retention

Plant Establishment Year

Luxury Uptake

Above and Below Ground Biomass

Beginning and End of Growing Season Soil

Sampling pH

Nitrogen Load

Mesocosm Experimental Setup Drainage Water

Mixing Tank

Organic Rep 1

Mineral Rep 1

Mineral Rep 2

Mineral Rep 3

Organic Rep 3

Organic Rep 2

Greenhouse

Perimeter

Spectro:lyser probe multiplexor system

Recirculation System

Control 1

Control 2

Control 3

Batch Run Plan

Run Types 1 2 3 4 5 6

Load 1X 2X 2X 4X 4X 8X NO3-‐N (mg L-‐1) 2.5 2.5 5 10 5 10 Water Depth (cm) 18 30 18 30 30 30 Antecedent Condition (cm) 1 1 1 7 1 1

Seasons Completed Winter Spring Fall

Fall Summer

Fall Winter Fall Summer Fall

Seasons Plan to Complete Summer Spring Summer Spring Summer Fall Summer

Spring

v Various hydraulic and nutrient loading rates v NO3-N concentrations 2.5-10 mg L-1 v Base load (1X) has 2.5 mg L-1 of NO3-N at depth of 18 cm v Runs last 7-10 days with depths of 18 and 30 cm

Instrumentation and Sampling Daily Monitoring (Days 0, 1, 2, 3, 5, 7, and 10)

v  Grab samples for NO3--N, NH4

+-N, and PO4

-3-P v  Redox Potential v  pH v  Dissolved Oxygen v  Water Depth

Daily Monitoring (0, 5, 10) v  TKN, Cl-,

Hourly Monitoring v  NO3

--N and DOC using the Spectro:Lyzer Probe and multiplexor system

v  Air Temperature v  Water Temperature v  Air Relative Humidity

Yearly/Seasonal Monitoring (2011-2013) v  Beginning and end of growing season

soil samples v  End of growing season above and

below ground biomass samples

PLC Controller

Solenoid ValveManifold

5 mm Cuvette

12 DifferentSampling Sources

Peristaltic Pump

Data Offload

Spectro: Lyzer Probe

Statistical Analysis v Multivariate statistical

analyses have been used to determine differences between NO3-N reductions in the two wetland soil treatments and the controls over time in SAS.

v  Effects of treatment, season, and N loading, were assessed with Tukey honest significance tests in SAS.

v All statistical tests were considered significant at α=0.05.

v Removal rate constants (k) have been calculated utilizing a widely used first order process equation (Burchell et al., 2007a; Reed et al., 2005; Kadlec and Knight, 1996)

v Maximum NO3-N loads that can be pumped into the full-scale wetland will be determined.

C = concentrations at time t (mgL-1) C0 = initial concentrations (mgL-1) k = rate constant (hr-1) t = time (hr)

Preliminary Nitrogen Removal Modeling

!!!= !!!!"

k

Preliminary Results

Wetland Run Summary (to date) Season (Date)

Avg. Water Temp (ºC)

Monitoring Time (day)

Water Depth (cm)

Target Ci

(mgL-‐1)

Actual Avg. Ci (mgL-‐1)

Load Mean NO3-‐N % Removal

WetlandOrg WetlandMin

Fall (9/15-‐10/4) 21.7 9 30 2.5 2.07 2X 65% 93%

Fall (10/16-‐10/26) 17.2 10 18 5 5.25 2X 81% 81%

Fall (11/5-‐11/15) 10.6 10 30 10 6.55 4X 51% 47%

Fall (9/24-‐10/4) 20.6 10 30 10 12.52 8X 56% 70%

Fall (10/15-‐10/25) 16.7 10 18 2.5 2.76 1X 95% 97%

Winter (1/22-‐2/1) 8.9 10 18 2.5 2.11 1X 48% 55%

Winter (2/11-‐2/21) 10.6 10 18 5 4.80 2X 41% 43%

Spring (5/28-‐6/7) 25.0 10 18 2.5 2.42 1X 100% 100%

Summer (7/2-‐7/12) 27.2 10 30 2.5 2.43 2X 97% 99%

Summer (8/6-‐8/16) 26.7 10 30 5 5.36 4X 96% 99%

Summer (8/20-‐8/27) 25.6 7 30 2.5 2.97 2X 90% 89%

NO3-N Concentration Reductions v  1X Load (2.5 mg L-1, 18 cm water depth)

v  NO3-N removal rates positively affected by temperature, as expected.

v  Removal curves will be used to determine NO3-N removal rate constants for each wetland type and adjusted for temperature.

Organic Mineral

* Data presented is an average of the 3 mesocosm samples.

UV-Spectrometer Continuous WQ data

Soil Redox Potentials v Redox potentials stayed below 250 mV in both the mineral and organic

mesocosms in all batch runs.

v The mineral mesocosms had slightly lower overall redox potentials.

v The 15 cm redox potentials were consistently lower than the 5 cm redox potentials in both the mineral and organic mesocosms.

Organic Mineral


Carbon Availability and pH


Batch Run Average Temperature

(ºC) Day of Run pH

DOC (mg L-1)

Mineral

Winter 8.9 0 7.31 10.25 10 7.38 9.38

Spring 25 0 8.16 11.92 10 6.52 7.5

Fall 16.7 0 7.47 6.38 10 6.83 8.89

Organic

Winter 8.9 0 6.36 60.43 10 6.62 48.80

Spring 25 0 7.65 28.67 10 5.64 54.25

Fall 16.7 0 7.21 15.31 10 6.5 48.52

Other Preliminary Results: v  Significant NO3-N reduction in wetland

mesocosms compared to the control mesocosms (α=0.05).

v Differences in NO3-N removal between soils, season, and N load are significant (α=0.05).

v  Preliminary mass balance estimates indicate denitrification could account for 44-65% and 60-80% of NO3-N removal in the Organic and Mineral wetland systems, respectively.

Rate Constants (k)


Preliminary Conclusions

Conclusions v  Significant NO3-N reductions were observed in the wetland

mesocosms with both organic and mineral soils.

v  Rates are greatest in the warmer seasons and limited in the winter, as expected, exhibiting the importance of temperature and season on NO3-N reduction.

v  Conditions are favorable for denitrification to occur within these

systems, but we remain uncertain to the percent removal that can be contributed to denitrification.

Future Evaluations

Important Future Evaluations v More batch runs are planned for the spring and summer

seasons of 2014 to fully assess seasonal variability.

v Rate constants and temperature coefficients will be further developed using more complex methodology to create a more robust NO3-N reduction predictive model.

v These models will be used to determine the seasonal NO3-N loads that can be applied and assimilated by the future full-scale restored wetland.

Acknowledgements

This presentation was developed under STAR Fellowship Assistance Agreement no. FP91748301-0 awarded by the U.S. Environmental Protection Agency (EPA). It has not been

formally reviewed by EPA. The views expressed in this presentation is solely those of Tiffany L. Messer and EPA does not endorse any products or commercial services mentioned in this

presentation.

♦  Committee: Dr. Michael R. Burchell II, Dr. François Birgand, Dr. George Chescheir, and Dr. Steven Broome

♦  US EPA, WRRI, NC Sea Grant ♦  Assistance in Field: Maggie Rabiipour, Kathleen Bell, James Blackwell, Kris Bass,

Randall Etheridge, Jacob Wiseman, Dr. Robert Lagacé, Mark Fernandez, and Yo-Jin Shiau

♦  BAE Environmental Analysis Lab: Rachel Huie and Heroshi Tajirir

♦  Soil Science Environmental & Agricultural Testing Service: Dr. Wayne Robarge, Guillermo Ramirez, and Lisa Lentz

References Ardόn, M., J. L. Morse, M.W. Doyle, and E.S. Bernhardt. 2010. The water quality consequences of restoring wetland hydrology to a large agricultural watershed in the southeastern coastal plain. Ecosystems, 13: 1060-1078. Bruland, G.L., C.J. Richardson, and S.C. Whalen. 2006. Spatial variability of denitrification potential and related soil properties in created, restored, and paired natural wetland. Wetlands, 26(4): 1042-1056. Burchell, M.R., R.W. Skaggs, C.R. Lee, S. Broome, G.M. Chescheir, and J. Osborne. 2007. Substrate organic matter to improve nitrate removal in surface flow constructed wetlands. Journal of Environmental Quality, 36(1):194-207. Chescheir, G.M., J.W. Gilliam, R.W. Skaggs, and R.G. Broadhead. 1991. Nutrient and sediment removal in forested wetlands receiving pumped agricultural drainage water. Wetlands, 11(1): 87-103. Harrison, M.D., P.M. Groffman, P.M. Mayer and S.S. Kaushal. 2012. Nitrate removal in two relict oxbow urban wetlands: a 15N mass-balance approach. Biogeochem. 111:647-660. Kadlec, R. H. and S.D. Wallace. 2009. Treatment Wetlands, 2nd ed. CRC Press, Boca Raton, FL, USA. Reed, S.C., R.W. Crites, and E.J. Middlebrooks. 1995. Natural systems for waste management and treatment. McGraw-Hill, Washington, DC.

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Determining Ideal Nitrogen Loads for Rerouted … · Rerouted Agricultural Drainage Water into Restored Forested Wetlands: ... Summer! Fall! Winter! Fall! Summer! ... DOC (mg L-1)