Nutrient Sources and Fluxes in Narragansett Bay:

1
Nutrient Sources and Fluxes in Narragansett Bay
Have some significant factors been
overlooked? Symposium on Nutrients in
Narragansett Bay November 18, 2004

Robert W. Howarth Cornell University
2
My background

• Member, NAS Committee on Wastewater Management in
  Coastal Urban Areas (1990-1993)
• Co-chair, International SCOPE N Project on
  Transport and Transformation of Nitrogen
  (1994-2002)
• Chair, NAS Committee on Causes and Consequences
  of Coastal Nutrient Pollution (1998-2000)
• Consultant to the Pew Oceans Commission on
  nitrogen pollution (2001)
• Chair of federal interagency planning effort for
  integrated research on coastal nutrient pollution
  (2001-2003)
• Director, North American Nitrogen Center
  (2003-2008)

3
Nitrogen sources and fluxes inNarragansett Bay
very well studied,in comparison to most coastal
marine ecosystems.Still, some
uncertainties and questions (as elsewhere).Are
there overlooked and under-appreciated factors?

4
Factors to consider that may have altered the
nitrogen flux or availability in Narragansett Bay

• Change in wastewater treatment?
• Change in diet?
• Increase in near-source N deposition from
  vehicles?
• Saturation of sink sites in the landscape, or in
  groundwater storage? Or climate change, altering
  non-point source fluxes?

5
Inputs of Nitrogen to Narragansett Bay (g N m-2
yr-1) Direct Wastewater and CSOs 8.0 Direct
atmospheric deposition 1.3 Rivers (including
wastewater, deposition, and
agriculture) 17. (from Nixon et al.
1995) Ocean-source not included.
6
Inputs of Nitrogen to Narragansett Bay (g N m-2
yr-1) Direct Wastewater and CSOs
8.0 Direct atmospheric deposition
1.3 Rivers (including wastewater,
deposition, and agriculture) 17.
If Blackstone River is typical, 65 from
wastewater 25 from deposition 10
from agriculture (Boyer et al. 2002, and
Howarth et al. in prep.)
7
Inputs of Nitrogen to Narragansett
Bay Wastewater and CSOs -- directly to
Bay 30 -- indirectly to rivers 42
72 Atmospheric deposition --
directly to Bay 5 -- indirectly to
landscape 17 22 Agriculture 6

8
Inputs of Nitrogen to Narragansett
Bay Wastewater and CSOs -- directly to
Bay 30 -- indirectly to rivers 42
72 Atmospheric deposition --
directly to Bay 5 -- indirectly to
landscape 17 22 Agriculture 6

Not well monitored, and may be low, due to
near-source deposition from vehicles and
difficulty in measuring dry deposition
9
Factors to consider that may have altered the
nitrogen flux or availability in Narragansett Bay

• Change in wastewater treatment?
• Change in diet?
• Increase in near-source N deposition from
  vehicles?
• Saturation of sink sites in the landscape, or in
  groundwater storage? Or climate change, altering
  non-point source fluxes?

10
Significant improvements in wastewater treatment
occurred in Providence area between
1980-1992.(Fields Point POTW upgraded to 2o
treatment EPA ranked as one of worst plants in
US in 1980, and best 2o plant in US in
1995).Note that 2o treatment lowers organic C
releases (BOD), but has relatively little
effect on N discharges from the plant. Perhaps
a 15 decrease? (national average)
11
Significant improvements in wastewater treatment
occurred in Providence area between
1980-1992.(Fields Point POTW upgraded to 2o
treatment EPA ranked as one of worst plants in
US in 1980, and best 2o plant in US in 1995).
Paradoxical potential consequence Did improved
water quality in immediate receiving waters cause
a decrease in N losses from denitrification
there, increasing far-field delivery of N to
Narragansett Bay (as occurred in the Seine
River)? Two NAS committees urged caution in
upgrading to only 2o treatment plants in areas of
N-sensitive waters without evaluating potential
consequences on this far-field N transport.
N-reduction upgrades at the same time may be
appropriate (NRC 1993, 2000).
12
Factors to consider that may have altered the
nitrogen flux or availability in Narragansett Bay

• Change in wastewater treatment?
• Change in diet?
• Increase in near-source N deposition from
  vehicles?
• Saturation of sink sites in the landscape, or in
  groundwater storage? Or climate change, altering
  non-point source fluxes?

13
Average per capita N consumption in meat and meat
products in the USA
(Howarth 2003)
14
Average per capita N consumption in meat and meat
products in the USA
20 increase since 1980 nationally should this
lead to 20 increase in N discharges from POTWs?
(Howarth 2003)
15
Average per capita N consumption in meat and meat
products in the USA
20 increase since 1980 nationally should this
lead to 20 increase in N discharges from POTWs?
Nixon talk showed no change in wastewater
discharges over past few decades Why is there
no diet effect??
(Howarth 2003)
16
Factors to consider that may have altered the
nitrogen flux or availability in Narragansett Bay

• Change in wastewater treatment?
• Change in diet?
• Increase in near-source N deposition from
  vehicles?
• Saturation of sink sites in the landscape, or in
  groundwater storage? Or climate change, altering
  non-point source fluxes?

17
A little background on deposition

• NOx emissions for US relatively constant over
  past several decades (through 2000) most
  stations show relatively constant wet deposition

18
USA atmospheric NOx emissions
Howarth et al. 2002
19
A little background on deposition

• NOx emissions for US relatively constant over
  past several decades (through 2000) most
  stations show relatively constant wet deposition
• Dry deposition very hard to measure, and poorly
  monitored includes nitrogen particles and
  gases, none of which are fully included in any
  monitoring program in US

20
A little background on deposition

• NOx emissions for US relatively constant over
  past several decades (through 2000) most
  monitoring stations show relatively constant wet
  deposition
• Dry deposition very hard to measure, and poorly
  monitored includes nitrogen particles and
  gases, none of which are fully included in any
  monitoring program in US
• NOx emissions to atmosphere in US exceed
  estimates of deposition by 20

21
A little background on deposition

• NOx emissions for US relatively constant over
  past several decades most stations show
  relatively constant wet deposition
• Dry deposition very hard to measure, and poorly
  monitored includes nitrogen particles and
  gases, none of which are fully included in any
  monitoring program in US
• NOx emissions to atmosphere in US exceed
  estimates of deposition by 20

One reason may be deposition near sources, not
included in monitoring networks.
22
Near-source deposition of N from vehicle
emissions

• New studies suggest that significant amounts of N
  emissions from vehicles are deposited near roads,
  and not accounted for in deposition monitoring
  networks (Stuart Weiss Howarth, Bettez, Marino,
  Davidson).
• Our preliminary data for Falmouth, MA
  deposition within 100 m of two major roads is
  1.5- to 2-fold elevated.
• Both NOx and NH3 are significant vehicle
  sources. NH3 sources may be growing rapidly, due
  to modern catalytic converters. Not included in
  any N budget for coastal systems.
• Increased traffic by high N emitting vehicles,
  such as SUVs?

23
Inputs of Nitrogen to Narragansett
Bay Wastewater and CSOs -- directly to
Bay 30 -- indirectly to rivers 42
72 Atmospheric deposition --
directly to Bay 5 -- indirectly to
landscape 17 22 Agriculture 6

24
Factors to consider that may have altered the
nitrogen flux or availability in Narragansett Bay

• Change in wastewater treatment?
• Change in diet?
• Increase in near-source N deposition from
  vehicles?
• Saturation of sink sites in the landscape, or in
  groundwater storage? Or climate change, altering
  non-point source fluxes?

25
Anthropogenic nitrogen sources and relationships
to riverine nitrogen export in the northeastern
USA
Boyer et al. 2002
26
NE region watershed nitrogen inputs
Boyer et al. 2002
27
Moderate-sized Watersheds, Northeastern US (Boyer
et al 2002)
28
Best guestimates of N sinks for northeastern US
watersheds (Van Breemen et al 2002)
Very poorly known! Will sinks saturate or change
over time?
29
Some research priorities

• Continuing and expanding efforts at historical
  analysis of eutrophication trends (from sediment
  records), as a check on our understanding of
  historical trends in N delivery to the Bay (did
  2o sewage treatment have an effect, for example?)
• Better estimating rates of atmospheric deposition
  across the watershed (particularly dry deposition
  both gases and particles, and both oxidized and
  reduced N including near-source deposition)
• Better evaluating sinks and storage of N in the
  landscape (including area not in major river
  drainages) rejuvenation of USGS monitoring is a
  part of this.

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Thank you!
31
North American Nitrogen Center
The North American Nitrogen Center is one of five
continental-scale centers of the International
Nitrogen Initiative sponsored by the
International Council of Science (ICSU) through
the Scientific Committee on Problems of the
Environment (SCOPE) and the International
Geosphere-Biosphere Program (IGBP).

• To better assess the sources of N pollution and
  the drivers of change in N cycling across the
  regions of North America, with an emphasis on
  evaluating trends in fluxes and environmental
  exposure.
• To comprehensively and quantitatively assess
  both the ecological and human-health consequences
  of N pollution in North America.
• To develop policy options for reducing N
  pollution and to encourage large-scale pilot
  studies to test potential policies and technical
  solutions.
• To communicate the issues of human acceleration
  of the N cycle to the public and to decision
  makers, and to facilitate communication and
  interaction among the scientific community.

http//www.eeb.cornell.edu/biogeo/nanc/nanc.htm
32
Riverine N flux (kg N km-2 yr-1)
Net Anthropogenic N inputs (kg N km-2 yr-1)
33
Wetter climates export more N. In dry climates,
10 of N inputs exported. In wet climates,
45.
Residual (kg N m-2 yr-1)
Discharge (mm yr-1)
34
Riverine N fluxes very well predicted from net
anthropogenic N inputs, attenuated by
discharge-predicted fractional delivery.
Riverine N flux (kg N km-2 yr-1)
(5 x 10-4 Discharge) (NANI) 115 kg N km-2
yr-1
35
So climate variation in Narragansett Bay probably
not important in change in N fluxes from
landscape, or may have decreased fluxes some.