Post on 16-Apr-2018
© 2015 Picarro Inc.
Picarro G5131-i
d15N, d15Na, d15Nb, d18O in N2O
Mid-IR Isotopic N2O Analyzer
© 2015 Picarro Inc.
Why measure N2O isotopes?
• N2O is a potent GHG (~ 300x Global Warming Potential of CO2)
– Loss of N2O from soils
– Emissions from wastewater treatment plants
– Oceanographic productivity and nitrogen cycling
• N2O is a pre-cursor for NOx in the upper atmosphere and plays an important role in regulating stratospheric ozone
• Isotope of N2O can be used to probe sources and sinks in the global nitrogen cycle
– Identify nitrification and denitrification processes in soils and water
– Investigate terrestrial N2O cycles to improve predictive models and better understand human contributions to global warming
– Investigate oceanic N2O cycles
• Humans are impacting the global N cycle everyday.
– We now add more N to the environment than is naturally fixed.
© 2015 Picarro Inc.
Global Nitrogen Cycle
• Nitrification and denitrification occurs through many pathways
• Nitrogen isotopes, including site-specific isotopic information, can be used to
trace these pathways
– Different processes produce N2O with different isotopic composition
https://grdc.com.auhttp://www.whoi.edu
Marine N Cycle Terrestrial N Cycle
© 2015 Picarro Inc.
Introduction to N2O Isotopes
• Reference scale for N isotopes is Air
• Reference scale for O isotopes in N2O
is typically VSMOW (but can be Air)
d15Na = 14N-15N-16Od15Nb = 15N-14N-16O d18O = 14N-14N-18O
Isotope Abundance (%)
14N 99.636
15N 0.364
16O 99.757
17O 0.038
18O 0.205
𝛿18𝑂 = 18𝑂 16𝑂
𝑠𝑎𝑚
18𝑂 16𝑂𝑠𝑡𝑑
− 1 1000
𝛿15𝑁 = 15𝑁 14𝑁
𝑠𝑎𝑚
15𝑁 14𝑁𝑠𝑡𝑑
− 1 1000
Site Preference = d15Na - d15Nb
© 2015 Picarro Inc.
Atmospheric budget of N2O
• The budget of atmospheric N2O is controlled by three major components:
– Flux of N2O from soils
– Mixing from the stratosphere
– Flux of N2O from the oceans
• Human activity is impacting the
global N2O cycle:
– Intensive agriculture
– Positive feedbacks associated a
warming climate
• The Picarro Advantage:
– N2O concentration precision (< 0.05
ppb) can identify rising N2O in the
well-mixed atmosphere
– Low drift (< 0.1 ppb) decreases time
spent on calibration
– Isotopes can identify sources and
sinks of N2O
1. Ice core records show increasing N2O
concentrations from 270 ppb prior to the Industrial
Revolution to over 300 ppb today
2. Field sites around the global today show N2O is
well-mixed in the atmosphere and has increased by
about 5% since the late 1970s (~ 300 to 315 ppb)
Ka
iser
(20
02
), P
hD
Th
esis
,
Jo
ha
nnes G
ute
nb
erg
-Univ
ers
ität
1
2
© 2015 Picarro Inc.
Soils: a significant flux of N2O to the atmosphere
• Agricultural emissions and emissions from natural soils account of between
56 and 70% of all global N2O sources (Syakila and Kroeze, 2011, doi:10.3763/ghgmm.2010.0007)
• Isotopes (d15N, d18O, d15Na, d15Nb) can be used to distinguish sources of N2O
flux
– N2O produced during nitrification is more depleted in 15N and 18O relative to the initial
substrate than N2O produced during denitrification
– The site location of the heavy 15N isotope can also help as different microbial
processes exhibit different site preference
• Picarro G5131-i can be used for:
NATURAL ABUNDANCE STUDIES
• Used in natural or unfertilized
systems
• Bulk isotopes (d15N, d18O) and site
preference (d15Na, d15Nb)
TRACER STUDIES
• Distinguish between nitrification and
denitrification following addition of
enriched fertilizers, e.g., 15N-NH4+ or
15N-NO3-
• Coupled 15N/18O enrichment
approaches are also being developed
© 2015 Picarro Inc.
The importance of N in the oceans
• The world’s oceans contribute about 30% of the atmospheric N2O budget
making them a significant source of this important GHG
– Nitrification dominates production of N2O
– Denitrifcation contributes only 7-35 % of N2O produced in the water column
– Amount of N2O produced in world’s ocean is dependent on dissolved O2
concentrations (enhanced under low O2)
• N2O emissions from the ocean will likely increase in the future due to:
1. Climate change, and the associated warming ocean temperatures, is expected to
expand the open ocean’s Oxygen Minimum Zones
2. Enhanced continental run-off and input of nutrients to the ocean will expand coastal
anoxic zones
© 2015 Picarro Inc.
Measure dissolved N2O with a Picarro G5131-i
• Oceanographers are typically interested in measuring N and O isotopes in
two forms:
Dissolved N2OBiologically-available N via
the denitrifier method
• Compatible with the compact
Picarro G5131-i
• Measure dissolved N2O and d15N
and d18O using an equilibration
device or head-space analysis
• Denitrifier methods produce only
a small amount of concentrated
N2O
• Dedicate your IRMS to the
denitrifier method and analyze
dissolved N2O with your Picarro
Dissolved gas set-up used by Erler et al.
(2015) with Picarro G5101-i
© 2015 Picarro Inc.
Picarro G5131-i: i-N2O in the air, water and soil
• The Picarro G5131-i is:
– Compact: the most compact analyzer on
the market for high-precision d15N, d15Na,
d15Nb and d18O.
– Precise and stable: Stability on the Picarro
platform allows you to average data for
longer and improve the precision of your
N2O concentration and isotope
measurements.
– Engineered for high performance: Tight
temperature and pressure control with a
small cavity enables superior performance in
the lab or in the field. Time-based
measurements avoid challenges associated
with laser fluctuations.
– Maximum versatility: measure small,
discrete gas samples, dissolved gases or
ambient atmospheric measurements.
© 2015 Picarro Inc.
Interfacing the G5131-i with Picarro Peripherals
Small Sample Introduction Module 2 16-Port Valve Manifold
The G5131-i is not compatible with Closed Systems operation (A0701, A0702).
© 2015 Picarro Inc.
Technical Specifications &
Performance of the Picarro G5131-i
© 2015 Picarro Inc.
Performance Specifications for G5131-i
© 2015 Picarro Inc.
G5131-i Spectroscopy
N2O peak
a and b peaks on wings
of large N2O peak
Distinct, separate
N218O peak
Area of weak water absorption & weak interference from CO2
© 2015 Picarro Inc.
Allan Deviation for Picarro G5131-i
stable to > 1 hour
0.5 ‰
0.02 ppb
© 2015 Picarro Inc.
Testing Precision on G5131-i
[N2O] (ppb) 1s Precision(100 sec)
1s Precision (10 min; 600 sec)
G5131-i 0.028 0.018
Specification 0.1 0.05
N2O @ 340 ppb
N2O
co
ncen
trati
on
(p
pb
)
© 2015 Picarro Inc.
Testing Precision on G5131-i
d15Na / d15Nb (‰) 1s Precision(100 sec)
1s Precision (10 min; 600 sec)
G5131-i 0.7 / 0.8 0.3 / 0.4
Specification 1.0 0.5
N2O @ 340 ppb
d1
5N
a(‰
)
d1
5N
b(‰
)
© 2015 Picarro Inc.
Testing Precision on G5131-i
d18O (‰) 1s Precision(100 sec)
1s Precision (10 min; 600 sec)
G5131-i 0.8 0.35
Specification 1.0 (300 sec) 0.7
N2O @ 340 ppb
d1
8O
(‰
)
© 2015 Picarro Inc.
Testing Drift on G5131-i
G5131-i Prototype Typical
[N2O] (ppb) 0.012 0.1
d15Na, d15Nb (‰) 0.4 / 0.3 2
d18O (‰) 0.3 2
© 2015 Picarro Inc.
Ability to measure small samples using the SSIM2
G5131-i
SSIM2
20 ml gas samples
for i-N2O analysis
© 2015 Picarro Inc.
Example Applications and Customer
Data
© 2015 Picarro Inc.
Picarro i-N2O for studying emissions from crop residue
• Soil incubations with crop residue (wheat, pea, canola, flax) spiked with 15N
and 13C
• Headspace analysis of evolved N2O (d15N) for daily and cumulative emission
from each treatment
• Under conditions of nitrification, the N source (crop residue type) had a
significant effect on N2O emissions while under denitrification there was
considerable potential for N2O emissions from crop residue
0 0.1 0.2 0.3 0.40.00
0.05
0.10
0.15
0.20
0.25
0.30
Re
sid
ue-d
eri
ved
N2O
em
iss
ion
(mg
N)
Urea Wheat Pea Flax Canola
0 2 4 6 8 10 120.00
2.00
4.00
6.00
8.00
Total N2O emission (mg N)
Re
sid
ue-d
eri
ve
dN
2O
em
issio
n(m
gN
)
0 0.1 0.2 0.3 0.40.00
0.05
0.10
0.15
0.20
0.25
0.30
Re
sid
ue-d
eri
ved
N2O
em
iss
ion
(mg
N)
Urea Wheat Pea Flax Canola
y = 0.585x - 0.0126
R2 = 0.937***
y = 0.675x + 0.099
R2 = 0.997***
0 2 4 6 8 10 120.00
2.00
4.00
6.00
8.00
Total N2O emission (mg N)
Re
sid
ue-d
eri
ved
N2O
em
issio
n(m
gN
)y = 0.244x + 0.037
R2 = 0.906***
Result from denitrification
experiment
G5101-i (d15N only) in Professor Rich
Farrell’s lab at University of Saskatchewan
Headspace
samples
For more information, see the Picarro webinar with Prof. Farrell.
© 2015 Picarro Inc.
Recent dissolved N2O results with Picarro
• For environments with variable
concentrations of O2, CO, CO2 and CH4 and
H2S care should be taken to limit or correct
spectral interference on d15N-N2O.
• However, with the appropriate chemical
removal or correction, an excellent
comparison to GC-IRMS can be achieved.
• Picarro recommends physical traps for the
removal of:
– H2O vapor (Drierite)
– H2S (Cu trap)
– CO (Pt catalyst)
– CO2 (Ascarite)
• For environments with variable O2 mixing
ratios, an instrument specific correction is
recommended. Erle
re
t a
l. (
20
15
), d
oi: 1
0.1
002/lom
3.1
00
32
© 2015 Picarro Inc.
Other resources for learning about N2O
• Picarro Webinar
– Using Nitrogen Isotopes to Partition N2O Emissions in Agriculture
• Professor Richard Farrell, University of Saskatchewan and Dr. Nabil Saad, Picarro
• http://www.picarro.com/resources/webinars/using_nitrogen_isotopes_to_partition_n2o_emission
s_in_agriculture
• Publications
– Peng et al. (2014), “The effect of dissolved oxygen on N2O production by ammonia-
oxidizing bacteria in an enriched nitrifying sludge”, Water Research,
doi:10.1016/j.watres.2014.08.009
• http://www.picarro.com/resources/literature_publications/the_effect_of_dissolved_oxygen_on_n2
o_production_by_ammonia_oxidiz
– Erler et al. (2015) “Applying cavity ring-down spectroscopy for the measurement of
dissolved nitrous oxide concentrations and bulk nitrogen isotopic composition in
aquatic systems: Correcting for interferences and field application”, Limnology and
Oceanography: Methods, doi:10.1002/lom3.10032
• http://www.picarro.com/resources/literature_publications/applying_cavity_ring_down_spectrosco
py_for_the_measurement_of_diss
© 2015 Picarro Inc.
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