Urea Release by Intermittently Saturated Sediments from a

Coastal Agricultural Landscape

1University of Maryland Eastern Shore, Princess Anne, MD 21853 2USDA-ARS, Pasture Systems and Watershed Management Research Unit, University Park, PA

16802

Thesis Advisory CommitteeDr. Eric B. May1, Co-advisorDr. Arthur L. Allen1, Co-advisorDr. Ray B. Bryant2

Dr. Fawzy M. Hashem1

Mason D. King1

1950 1960 1970 1980 1990 2000 2010 20200%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Ure

a-N

as a

% o

f Tot

al N

Data from USDA Economic Research Service Image adapted from WHOI Harmful Algal Bloom website

HABs pre-1972

Puerto Rico

Hawaii

Alaska

HABs present

Puerto Rico

Hawaii

Alaska

Year

Neurotoxic shellfish poisoningParalytic shellfish poisoning CiguateraBrown tide

Pfisteria complexFarmed fish killsAmnesic shellfish poisoning

Introduction

Urea

Why the concern about urea?ABCDEFGHIJKLMNOP

Microplankton Species

Nitrate

Dominant

Urea

Dominant

(Solomon et al., 2010; Glibert et al., 2001, 2005, 2006, 2014; Howard et al., 2007; Thessen, et al. 2009; Berman & Chava, 1999; Finlay et al. 2010)

• Some phytoplankton exploit urea > inorganic N

• Loading could shift community structureo HABs

• Can enhance growth rate or toxicityo Including mid-Atlantic coasts and

Chesapeake Bay

• High urea concentrations in agricultural watershedso Highest values reported in

agriculture-dominated tributaries to the Chesapeake Bay and the MD coastal baysChesapeake

BayCoastal

Bays

Delmarva Peninsula

(Glibert et al. 2005; Solomon et al. 2010)

• Agriculture is 48% of land use on the Delmarva Peninsula

• BUT urea hydrolyzes rapidly in soilo Fertilizero Manure

• Runoff and leaching losses are briefo About 1 week under normal

conditions

(Tzilkowski, 2013; Han et al., 2015; Kibet et al., in review)

Window when urea or poultry

litter would normally be

applied

• Urea concentrations under baseflowo Peak mid to late summero Wetland streams > agricultural streams o Highest concentrations in agricultural drainage ditches

0.14

0.12

0.10

0.08

0.06

0.04

0.02

0.00

Ure

a-N

(mg

L-1)

*

*

*

*

*

Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMonth

First and second order

streams

(Tzilkowski 2013)

• Urea–N in ditches up to 0.220 mg L-1

• High concentrations unexplained by external inputso Shallow groundwater

(leaching)o Surface runoffo Wet atmospheric

deposition• Apparently autochthonous

origin

Urea in shallow groundwater

Groundwater data courtesy of Leonard Kibet

0.00 0.01 0.02 0.03 0.04 0.05

Urea-N (mg L-1)

Objective:• Assess urea release by intermittent sediments

from an agricultural landscape

Hypothesis: • Higher urea concentrations would result from

1. Wetland and drainage ditch sediments2. N enriched conditions3. Higher temperature

Objectives & Hypothesis

Intermittent freshwater sediments for a mesocosm experiment were collected from a farm and a nearby wetland.

Methods

Washed, screened, autoclaved sand used as a control sediment

Mesocosm sediments were subsampled before and after experimental saturation and incubation

Sediment urea–N, NH4+–N, and NO3

-–N extracted with 2 M KCl

Mesocosms placed in water baths

Saturated with distilled water or N solution (NH4

+–N or NO3-–N)

Surface water samples were taken at time intervals

Surface water samples and sediment subsamples were analyzed colorimetrically for urea–N, NH4

+–N, and NO3

-–N

The experiment was replicated three times

Data analyzed o General linear model (GLM)o Linear mixed model (LMM) with

repeated measures, o Paired T tests

5 sites x 3 temperature treatments x 5 solution types = 75

conditionsControl 16°C Distilled water

Agriculture ditch 21°C NH4+–N 1.52mg L-1

Cleaned agriculture ditch 27°C NH4+–N 3.00 mg L-1

Forest NO3-–N 2.59 mg L-1

Wetland NO3-–N 5.07 mg L-1

Storms on Aug 10 & 11, 2015 filled dry ditches

Conditions analogous to mesocosm experiment

Automatic samplers deployed 18 h after first rainfall

Water drawn at same intervals as mesocosm experiment

Analyzed for urea–N, NH4+–N,

and NO3-–N

Results

Higher urea–N and NH4+–N in forest and wetland

Higher NO3-–N in uncleaned ditch and cleaned ditch

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.00

5.00

10.00

15.00

20.00

25.00

30.00

CBC B

AA

D

B

A

C CD

CB

A A

Urea-N Nitrate-N Ammonium-N

Ure

a–N

(m

g kg

-1)

NO

3-–N, N

H4+–N (m

g kg-1)

Initial sediment N concentration by site (n = 45, GLM).

0.00

0.02

0.04

0.06

0.08

BB

C B BB

B BCCD BC

B BA

AB A

AA

AA

A AA

A

B CD C C C

Control Cleaned ditch Uncleaned ditch Forest Wetland

Urea

–N (m

g L-

1)

0.00

0.50

1.00

1.50

2.00

2.50

AB BC CD BC B BCA A

A A A A

A AB BC ABAB

ABA A

AB A AA

B C D C C C

NH4

+–N

(mg

L-1)

0 12 24 36 48 60 720.00

3.00

6.00

9.00

12.00

15.00

BC BC C C B BB B B B B B

A

AA

A

A A

A

A AA

A A

C C C C B B

Hours

NO

3-–N

(m

g L-

1)

Effect of site on surface water N(n = 15, LMM).

Higher urea–N in ditch mesocosms, not wetland mesocosms

Also higher NO3-–N in ditch mesocosms

Rapid NO3-–N loss

0 12 24 36 48 60 720.00

5.00

10.00

AA A

A

A AB

B B AAB AC C C B BC BC

C C B BC BC C C BC B

Hours

NO

3-–N

(mg

L-1)

Effect of N enriched saturating solution(n = 15, LMM).

Higher urea–N in ditch mesocosms, not wetland mesocosms

Increase and loss of NO3-–N

0.00

0.02

0.04

0.06

0.08

B BBB

BBA A

B B

Distilled water Ammonium- low Ammonium- highNitrate- low Nitrate- high

Urea

-N (m

g L-

1)

0.00

1.00

2.00

3.00

C C C C BC C

C C C CBC C

A A A A A A

B B B B BB

C C C C CC

NH4

+–N

(mg

L-1)

No consistent and clear effect on urea–N

0.00

0.02

0.04

0.06

0.08

AA

AA

A

BAB B B B

BB B

B B

16°C 21°C 27°C

Urea

-N (m

g L-

1)

0.00

1.00

2.00

3.00

AA

A

AB B BB B B

NH4

+–N

(mg

L-1)

0 12 24 36 48 60 720.00

2.00

4.00

6.00

8.00

AA

C B

ABAB

B BB

B A A

Hours

NO

3-–N

(mg

L-1)

Effect of temperature on surface water N (n = 25, LMM).

More urea–N at high temperature

More NH4+–N at high temperature

NO3-–N dynamics increase with temperature

-0.25

0.00

0.25

0.50

0.75

Ditch 1 (soy, uncleaned) Ditch 2 (soy, uncleaned)Ditch 3 (soy, uncleaned) Ditch 4 (corn, cleaned)Ditch 5 (soy & corn, cleaned)

Urea

-N (m

g L-

1)

0.00

2.00

4.00

6.00

8.00

NH4

+–N

(mg

L-1)

6 18 30 42 54 66 78 90 102 114 126 1380.00

1.00

2.00

3.00

4.00

Hours after first rainfall

NO

3-–N

(m

g L-

1)

N in farm ditches after Aug 10 & 11, storms

High urea–N concentrations

NH4+–N related to ditch cleaning and/or urea–N?

NO3-–N rapidly lost

0.00

0.50

1.00

A

B

B

ASeries1 0.36 0.41 0.33 0.97 1.00

Ure

a–N

(mg

kg-1

)0.00

10.00

20.00

30.00

B

A

A

A AA

B BB B

NO

3-–N

(mg

kg-1

)

0.00

10.00

20.00

30.00

NH

4+–N

(mg

kg-1

)

Sediment N by site before and after mesocosm experiment (n = 45, paired t test).

Before After

Change in urea–N is variable

NO3-–N

decreased

Main controls on urea (Bogard et al., 2012)Discussion• Results reflect active cycling, not simple diffusion from inert urea pool in sediments

• Bacterial metabolism and decomposition of organic matter produce urea in sedimentso Low C:No Warm temperatures

• In ditch sediments urea may cycle rapidly. Some is lost to surface water where it accumulates due to low transformation rates

• Agricultural watersheds can have 9 m of ditch for every 1 m of stream length

• Urea release by ditch sediments explains high concentrations well after fertilizationo Indirect role of agricultural management (lowered

sediment C:N ratio)

(Tzilkowski, 2013)

Conclusions

• Urea in stagnant farm ditches may be exported by stormflow ando Shift phytoplankton

communitieso Trigger HABs and/or toxin

production

(Glibert et al., 2006, 2014; Finlay et al., 2010)

AcknowledgementsKevin Miller, Lou Saporito, Terry Troutman, Janice Donohoe, Peter Sang, Joan Weaver, Curt Dell, Anthony Buda, Lindsey Hughes, Nancy Chepketer, Tedra Booker, Nelson Kimutai, Derrick Cheruiyot, Wahed Abdullah, Peter Kim, Solomon Kirongo, Don Mahan, Tracie Bishop, Earle Canter, Jennifer Ossai, Caitlin LaComb, Wilmelie Cruz-Marrero, the UMES Department of Food, Agriculture, and Resource Science, the UMES Department of Natural Sciences, and the NRCS-USDA CIG Program.

References available upon request

mking@umes.edu

Berman, T., & Chava, S. (1999). Algal growth on organic compounds as nitrogen sources. Journal of Plankton Research, 21(8), 1423–1437.

Bogard, M. J., Donald, D. B., Finlay, K., & Leavitt, P. R. (2012). Distribution and regulation of urea in lakes of central North America. Freshwater Biology, 57(6), 1277–1292.

Finlay, K., Patoine, A., Donald, D. B., Bogard, M. J., & Leavitt, P. R. (2010). Experimental evidence that pollution with urea can degrade water quality in phosphorus-rich lakes of the Northern Great Plains. Limnology and Oceanography, 55(3), 1213–1230.

Glibert, P. M., Harrison, J., Heil, C., & Seitzinger, S. (2006). Escalating worldwide use of urea – A global change contributing to coastal eutrophication. Biogeochemistry, 77(3), 441–463.

Glibert, P. M., Magnien, R., Lomas, M. W., Alexander, J., Fan, C., Haramoto, E., … Kana, T. M. (2001). Harmful Algal Blooms in the Chesapeake and Coastal Bays of Maryland, USA: Comparison of 1997, 1998, and 1999 Events. Estuaries, 24(6), 875–883.

Glibert, P. M., Maranger, R., Sobota, D. J., & Bouwman, L. (2014). The Haber Bosch–harmful algal bloom (HB–HAB) link. Environmental Research Letters, 9(10), 105001.

Han, K., Kleinman, P. J. A., Saporito, L. S., Church, C., McGrath, J. M., Reiter, M. S., … Bryant, R. B. (2015). Phosphorus and nitrogen leaching before and after tillage and urea application. Journal of Environmental Quality, 44, 560–571.

Howard, M. D. A., Cochlan, W. P., Ladizinsky, N., & Kudela, R. M. (2007). Nitrogenous preference of toxigenic Pseudo-nitzschia australis (Bacillariophyceae) from field and laboratory experiments. Harmful Algae, 6, 206–217.

Kibet, L., Bryant, R., Buda, A., Kleinman, P., Saporito, L., Allen, A., … May, E. (2015). Persistence and surface transport of urea-nitrogen in a coastal plain soil. Journal of Environmental Quality, In review.

Solomon, C. M., Collier, J. L., Mine Berg, G., & Glibert, P. M. (2010). Role of urea in microbial metabolism in aquatic systems: a biochemical and molecular review. Aquatic Microbial Ecology, 59(1), 67–88. 7

Thessen, A. E., Bowers, H. A., & Stoecker, D. K. (2009). Intra- and interspecies differences in growth and toxicity of Pseudo-nitzschia while using different nitrogen sources. Harmful Algae, 8(5), 792–810.

Tzilkowski, S. S. (2013). Watershed scale controls on urea transport in a coastal plain river network. Pennsylvania State University Thesis.

References

Extra material

Control Cleaned ditch

Uncleaned ditch Forest Wetland Distilled

waterNH4

+–N low

NH4+–N

highNO3

-–N low

NO3-–N

high16°C 21°C 27°C

N typeUrea–N

Min <0.015 <0.015 <0.015 <0.015 <0.015 <0.015 <0.015 <0.015 <0.015 <0.015 <0.015 <0.015 <0.015Max 0.182 0.477 0.332 0.374 0.248 0.256 0.477 0.334 0.332 0.209 0.133 0.334 0.477

NH4+–NMin <0.10 <0.10 <0.10 <0.10 <0.10 <0.10 <0.10 0.14 <0.10 <0.10 <0.10 <0.10 <0.10Max 4.32 14.22 8.53 8.16 7.57 14.22 11.08 8.53 10.13 7.55 5.56 8.53 14.22

NO3-–NMin <0.20 0.33 0.45 0.31 <0.20 0.22 <0.20 <0.20 0.47 0.24 <0.20 <0.20 <0.20Max 7.81 106.10 81.36 9.67 21.32 81.36 73.40 73.21 75.44 106.10 37.25 73.21 106.10

…..……………………………………………………………………………………….. mg L-1 ……………………………………………………………………………………………………………..

Sediment Saturating solution Temperature