Upload
parikhit-sinha
View
213
Download
0
Embed Size (px)
Citation preview
Atmospheric Environment 37 (2003) 2139–2148
Emissions of trace gases and particles from two ships in thesouthern Atlantic Ocean
Parikhit Sinhaa, Peter V. Hobbsa,*, Robert J. Yokelsonb, Ted J. Christianb,Thomas W. Kirchstetterc, Roelof Bruintjesd
aDepartment of Atmospheric Sciences, University of Washington, Box 351640, Seattle, WA 98195 1640, USAbDepartment of Chemistry, University of Montana, Missoula, USA
cLawrence Berkeley National Laboratory, Berkeley, CA, USAdNational Center for Atmospheric Research, Boulder, CO, USA
Received 2 September 2002; accepted 9 January 2003
Abstract
Measurements were made of the emissions of particles and gases from two diesel-powered ships in the southern
Atlantic Ocean off the coast of Namibia. The measurements are used to derive emission factors from ships of three
species not reported previously, namely, black carbon, accumulation-mode particles, and cloud condensation nuclei
(CCN), as well as for carbon dioxide, carbon monoxide (CO), methane (CH4), non-methane hydrocarbons, sulfur
dioxide (SO2), nitrogen oxides (NOx), and condensation nuclei. The effects of fuel grade and engine power on ship
emissions are discussed. The emission factors are combined with fuel usage data to obtain estimates of global annual
emissions of various particles and gases from ocean-going ships. Global emissions of black carbon, accumulation-
mode particles, and CCN from ocean-going ships are estimated to be 19–26Gg yr�1, (4.4–6.1)� 1026 particles yr�1, and
(1.0–1.5)� 1026 particles yr�1, respectively. Black carbon emissions from ocean-going ships are B0.2% of total
anthropogenic emissions. Emissions of NOx and SO2 from ocean-going ships are B10–14% and B3–4%, respectively,
of the total emissions of these species from the burning of fossil fuels, and B40% and B70%, respectively, of the total
emissions of these species from the burning of biomass. Global annual emissions of CO and CH4 from ocean-going
ships are B2% and B2–5%, respectively, of natural oceanic emissions of these species.
r 2003 Elsevier Science Ltd. All rights reserved.
Keywords: Ship emissions; Particles from ships; Gases from ships; Emissions from ships; Pollution from ships
1. Introduction
Ships are among the world’s highest polluting
combustion sources per quantity of fuel consumed
(Corbett and Fischbeck, 1997). They account for up to
B14% of all nitrogen emissions from fossil fuel
combustion, and up to 4% of all sulfur emissions from
fossil fuel combustion (Corbett et al., 1999). Moreover,
ship emissions often take place in areas remote from
other sources of air pollution. Over large areas of the
northern hemisphere, and in some regions of the
southern hemisphere, sulfur emissions from ships are
comparable to natural biogenic emissions of dimethyl
sulfide (DMS) from the ocean (Corbett et al., 1999).
Emissions from ships may increase surface concentra-
tions of nitrogen oxides (NOx) in heavily traversed
ocean regions by more than 100-fold (Lawrence and
Crutzen, 1999).
Cloud condensation nuclei (CCN) in ship exhausts
can increase the albedo of stratiform marine clouds
by increasing the concentrations of cloud droplets
*Corresponding author. Tel.: +1-206-543-6027; fax: +1-
206-685-7160.
E-mail address: [email protected]
(P.V. Hobbs).
1352-2310/03/$ - see front matter r 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S1352-2310(03)00080-3
(Twomey, 1977; Radke et al., 1989; King et al., 1993;
Ferek et al., 1998). The resulting ‘‘ship tracks’’ appear in
satellite imagery as long-lived linear regions of enhanced
solar reflectivity in marine stratiform clouds downwind
of ships (Hobbs et al., 2000). Global radiative forcing
due to the emission of CCN from ships has been
estimated to be –0.11Wm�2 (Capaldo et al., 1999).
Emissions of NOx from ships increase tropospheric
ozone (O3) and the hydroxyl radical (OH) over their
background levels, thereby increasing the oxidizing
power of the troposphere, decreasing the atmospheric
lifetimes of reactive greenhouse gases, and increasing
aerosol production rates (Lawrence and Crutzen, 1999).
Since B70% of the emissions from ocean-going ships
occur within 400 km of land, ship emissions may also
affect air quality in many coastal and port regions
(Corbett et al., 1999).
A global inventory of ship emissions, based on
emission measurements at sea, fuel usage, and engine
characteristics, has been given by Corbett et al. (1999).
Emission factors (i.e., mass of a species emitted per unit
mass of fuel burned) based on emission tests from
Lloyd’s Register of Shipping are given by Carlton et al.
(1995). Emission factors for some species have been
obtained from airborne measurements in the plumes of
ships at sea (Hobbs et al., 2000).
In September 2000, the University of Washington
(UW) Cloud and Aerosol Research Group (CARG),
with its Convair-580 research aircraft, obtained in situ
measurements of a large number of gaseous and
particulate emissions, including several species not
previously measured, from two ships in the southern
Atlantic Ocean, off the coast of Namibia. These
measurements are described here and utilized to derive
estimates of emissions of a number of species from
ocean-going ships worldwide.
2. Sampling techniques and instrumentation
All of the measurements described in this paper were
obtained aboard the UW Convair-580 research aircraft.
A complete list of the instruments aboard this aircraft
for the present study is given in a technical appendix by
P.V. Hobbs in Sinha et al. (2003). Only the instruments
and techniques that provided the measurements pre-
sented in this paper are described here.
Aerosol samples collected on quartz filters (Pallflex
2500 QAT-UP) were used to determine the concentra-
tion of particulate carbon. Black carbon (BC) concen-
tration was measured with an optical transmission
technique similar to that described by Rosen and
Novakov (1983). This method compares the attenuation
of white light through a loaded filter relative to that of a
blank filter. The relationship between optical attenua-
tion (ATN) and the BC concentration (mg cm�2) is given
by ATN=sBC, where ATN ¼ 100� ln ðI0=IÞ; where I0and I are the transmitted light intensities through the
blank and loaded filters, respectively, and s the mass
absorption cross-section for BC deposited on quartz
(m2 g�1). A value of 20m2 g�1 was used for the mass
absorption cross-section (Gundel et al., 1984).
Measurements of SO2 were made using a Teco model
43S pulsed-fluorescence analyzer (precision of 7%,
detection limit of 1 ppbv). Calibration of this instru-
ment, both in flight and on the ground, was carried out
with commercial standard mixture (Scott-Marrin) of
18079 ppbv SO2 in ultra pure air. The instrument was
zeroed using ultra pure air (SO2o1 ppbv). Measure-
ments of O3 were obtained with a Teco model 49C UV
photometric analyzer (precision of 2%, detection limit
of 3 ppbv). Calibration of this instrument was carried
out prior to and following the field project using a
Columbia Scientific Instruments Photocal 3000 Version
080 Ozonator. Continuous measurements of O3 were
obtained using the Teco 49C in ambient air.
The total concentration of particles (CN) in the size
range B0.003–3mm diameter was measured with a TSI
3025A ultrafine condensation particle counter (precision
of 10%). A particle measuring systems (PMS) passive
cavity aerosol spectrometer probe (PCASP-100X) was
used for measuring particle size spectra from B0.10 to
3.00 mm. The PCASP-100X was mounted on the wing of
the aircraft. The sampling inlet was heated to dry the
particles, so that measurements from the PCASP could
be compared with those obtained on dried particles with
other instruments inside the aircraft cabin. The PCASP-
100X was regularly calibrated on the ground using
polystyrene latex spheres of known sizes. Concentra-
tions of cloud condensation nuclei (CCN) at 0.3%
supersaturation were measured with a University of
Wyoming thermal diffusion chamber.
The filters, SO2, and O3 measurements required
sampling times longer than it took the aircraft to cross
the widths of ship plumes (B30 s). Therefore, when
sampling the plumes, we employed a ‘‘grab-bag’’
technique, which consisted of a 2.5m3 electrically
conducting plastic (Velostat) bag that could be filled
with a sample of a plume in 12 s, to obtain samples for
the filters, SO2 and O3 measurements. Samples in the
grab-bag were drawn through the filters for subsequent
chemical analysis of the aerosol. The TSI 3025A was
also configured so it could sample from the grab-bag.
The grab-bag system had an aerosol 50% cut point
diameter of B4mm; larger particles were lost in the inletand on the walls of the grab bag. Grab-bag samples of
plumes were followed by grab-bag samples of ambient
air, which were compared to continuous sampling of
ambient air. There was no significant difference between
the two sampling techniques.
Evacuated electropolished stainless steel canisters
were used to sample the ship plumes, or ambient air
P. Sinha et al. / Atmospheric Environment 37 (2003) 2139–21482140
just upwind of the ships, using a stainless steel inlet that
passed through the aircraft fuselage. For each canister
sample, mixing ratios of selected C2–C11 non-methane
hydrocarbons (NMHC) were determined by gas chro-
matography (GC) with flame ionization detection (FID)
and electron capture detection (ECD). The precision of
the NMHC measurements was 3%, and the typical
NMHC detection limit was 3 pptv. Mixing ratios of CO2
(precision of 3%), CO (precision of 5%), and CH4
(precision of 0.1%) in the canisters were determined
using a second GC/FID. A detailed description of the
analytical procedure for the canister samples, including
quantification of the measurement precision for indivi-
dual compounds, is given by Colman et al. (2001).
An airborne Fourier transform infrared spectrometer
(AFTIR) was deployed onboard with a separate and
specially coated inlet that directed ram air through a
Pyrex multipass cell with an exchange time of 4–5 s. For
the ship plume penetrations, the AFTIR was used to
measure CO2, CO, nitric oxide (NO), nitrogen dioxide
(NO2), and O3. The AFTIR technique is described in
detail by Yokelson et al. (2003).
3. Calculation of emission factors
Emission factors for gases and particles were calcu-
lated using the carbon balance method (Radke et al.,
1988), which assumes that all carbon is emitted as CO2,
CO, CH4, non-methane organic compounds (NMOC),
and particulate carbon (PC). The emission factor
(EF(X)) of a species X is defined here as the ratio of
the excess mass concentration (DX ) of X emitted by a
source to the excess mass concentration of the total
carbon (DC) emitted by the source:
EF ðX Þ ¼
½DX �½DC�CO2
þ ½DC�CO þ ½DC�CH4þ ½DC�NMOC þ ½DC�PC
;
ð1Þ
where the excess mass concentration refers to the excess
in the plume over the concentration in the ambient air.
This emission factor is commonly converted to grams of
X emitted per kilogram of fuel burned using the mass
fraction of carbon in the fuel. Typically, the fuel burned
in large marine diesel engines is a mixture of hydro-
carbons with a ratio of hydrogen to carbon atoms of 1.8
(Tuttle, 1995), which corresponds to a mass fraction of
carbon in the fuel of B87%.
4. Ships studied
The UWs Convair-580 was used to sample emissions
from two ships: the tanker Royal Sphere, located at
26.25S and 13.49E, and the container ship MSC
Giovanna, located at 26.00S and 13.61E, both in the
southern Atlantic Ocean off the coast of Namibia
(Fig. 1). Plume samples of the Royal Sphere and the
MSC Giovanna were obtained at 1001 and 1033 UTC, 14
September 2000, respectively. Information on the two
ships is given in Table 1.
Diesel propulsion systems on large ships are designed
to run on two types of fuel, residual fuel and distillates.
Residual fuel refers to a broad category of low-grade
fuel, ranging from crude oil to a fuel where some of the
impurities have been removed from the oil, particularly
those that cause excessive engine wear. Residual fuels
are generally characterized by high density, high
viscosity, and high concentrations of impurities such as
sulfur (Corbett et al., 1999). The high viscosity fuel
carried on the Royal Sphere (2187 ton) is a residual fuel
that has only a few impurities removed. The inter-
mediate fuel oil carried on the MSC Giovanna (1906 ton)
is a higher grade of residual fuel with more impurities
removed. Distillates, such as the diesel oil carried on the
Royal Sphere (420 ton) and MSC Giovanna (309 ton), are
refined fuels of various grades that are more expensive
than residual fuels. Different engines require different
grades of distillates. Combustion of distillates results in
less non-CO2 emissions than the combustion of residual
fuels.
In general, ship operators use the lowest grade, lowest
cost fuel available that does not cause excessive engine
wear. When operating in the open ocean, ship operators
will generally use residual fuels. Due to their higher cost,
distillates are generally used only where air pollution
regulations require them (i.e., in harbors, on approaches
to major ports, and within certain distances from shore).
When ships make port visits only a few days apart, they
may continue to burn distillates during transit to avoid
switching between fuel systems. Based on their north-
northeast headings, both the Royal Sphere and the MSC
Giovanna appeared to be traveling toward the port at
Walvis Bay, Namibia (Fig. 1).
5. Results
5.1. Ambient conditions
Immediately prior to sampling the plumes from the
two ships, there were no clouds in the vicinity of the
ships, and there were no low-altitude stable layers to
limit the rise of the ship plumes. Surface wind speeds
were moderate at B10m s�1. The background air was
quite clean, with surface O3 mixing ratios below 30 ppbv,
surface SO2 mixing ratios of o1 ppbv, CN concentra-
tions of B500 cm�3, and CCN concentrations at 0.3%
supersaturation of B70 cm–3.
P. Sinha et al. / Atmospheric Environment 37 (2003) 2139–2148 2141
5.2. CN concentrations along the plumes
Measurements of CN concentrations along the length
of the two ship plumes are shown in Fig. 2a. The CN
concentrations in the plume from the Royal Sphere
peaked at B7� 104 cm�3 above the ship and dropped
off to ambient (B500 cm�3) concentrations B1 km
downwind of the ship. The CN concentrations in the
plume from the MSC Giovanna peaked atB1� 105 cm–3
above the ship and remained well above ambient
concentrations (5� 102 cm�3) up to at least 3 km down-
wind of the ship. The dense particulate emissions from
the MSC Giovanna were likely due to its use of residual
fuel.
5.3. Emission factors
Emission factors for selected gaseous and particulate
species were derived from the measurements obtained in
the plumes of the Royal Sphere and MSC Giovanna
(Table 2). As can be seen from Table 2, the SO2 emission
factor for the Royal Sphere was substantially less than
for the MSC Giovanna. We surmise from this that the
Royal Sphere had switched to distillate fuel as it headed
for port, but the MSC Giovanna was still burning
residual fuel.
In Table 2 the emission factors from this study are
compared with those for the ships discussed by Hobbs
et al. (2000) and Carlton et al. (1995). Hobbs et al.
derived emission factors for selected gases and particles
from in situ aircraft measurements of ship emissions off
the west coast of the United States. They sampled the
plumes of eight ships burning either low-grade marine
fuel oil or high-grade navy distillate fuel. Carlton et al.
(1995) describe the results of a study of ship emissions
from marine diesel propulsion engines conducted by
Lloyd’s Register of Shipping. Steady-state emissions at
various ship engine loads from 60 engines on 50 vessels
at sea were measured for medium- and slow-speed diesel
engines burning both distillate and residual fuel.
5.3.1. Carbon dioxide
Emissions of CO2 from ships are independent of
engine power and depend primarily on the carbon
Fig. 1. Locations of the Royal Sphere and MSC Giovanna when their plumes were sampled from the Convair-580 aircraft. The arrows
indicate the headings of the ships.
P. Sinha et al. / Atmospheric Environment 37 (2003) 2139–21482142
content of the fuel burned (Carlton et al., 1995). As
such, the emission factors for CO2 from the Royal
Sphere and MSC Giovanna (3135 and 3176 g kg�1 of
fuel, respectively) agree within 1% even though the
engine power of the MSC Giovanna exceeds that of the
Royal Sphere by B60% (Table 1). The CO2 emission
factors from this study are consistent with the value of
3170 g kg�1 of fuel reported by Carlton et al. (1995). The
CO2 measurements in this study were obtained by
AFTIR from plume samples collected at altitudes of
B90 and B60m above the Royal Sphere and MSC
Giovanna, respectively. The CO2 measurements from
Carlton et al. were obtained using a non-dispersive
infrared analyzer with a sample line directly attached to
the exhaust stack of the ship being studied.
The CO2 emission factors from this study can be
compared to the value of 1700760 g kg�1 of fuel
obtained by Sinha et al. (2003) for savanna fires in
southern Africa using the same instrumentation and
sampling strategies used in the present study. The much
higher CO2 emission factor for ships is primarily a result
of the higher carbon fraction in ship fuels (B87%)
compared to biomass (B50%).
5.3.2. Carbon monoxide
Unlike CO2, emissions of CO from ships are
dependent on engine power with higher CO emissions
resulting from ship engines with less power (Carlton
et al., 1995). As such, the CO emission factor for the
Royal Sphere (19.5 g kg�1 of fuel) exceeds that of the
MSC Giovanna (3.0 g kg�1 of fuel) whose engine is
B60% more powerful than that of the Royal Sphere.
Carlton et al. (1995) reported an average CO emission
factor of 7.4 g kg�1 of fuel, which is between the two
values measured in this study. Carlton et al. studied
ships with engine power ranging from 0.364 to
21.643MW, compared to the range of 8.2–13.4MW in
this study.
5.3.3. Hydrocarbons
As with CO, emissions of hydrocarbons (HC) from
ships depend on engine power, with lower power engines
emitting more HC. This trend is evident in the emission
factors for CH4 and NMHC, since the emission factors
for CH4 and NMHC for the Royal Sphere (5.4 and
2.4 g kg�1 of fuel, respectively) exceed those for the MSC
Giovanna (2.6 and 0.4 g kg�1 of fuel, respectively).
The emission factor for total hydrocarbons
(CH4+NMHC) reported by Carlton et al. (1995) of
2.4 g kg�1 of fuel is comparable to our measurement for
the MSC Giovanna (3.0 g kg�1 of fuel) but lower than
that of the Royal Sphere (7.8 g kg�1 of fuel). However,
hydrocarbon emissions depend not only on engine
power but also on the percentage utilization of engine
power. Carlton et al. (1995) showed that hydrocar-
bon emissions could be increased by B50% when theTable1
Propulsionsystem
parametersfortheships
Ro
ya
lS
ph
ereand
MS
CG
iova
nn
afrom
Lloyd’sRegisterofShipping(2002)
Ship
Ship
type
Gross
tonnage
Engine
type
Number
of
cylinders
Length
(m)
Beam
(m)
Draft(m
)Power
(MW)
Fuelaboard
Fuel
consumption
rate(kgs�
1)
Servicespeed
(ms�
1)
Ro
ya
l
Sp
her
e
Tanker
21,893
Diesel
6182.6
29.6
10.6
8.2
Dieseloil(420ton),
highviscosity
fuel
(2187ton)
0.35
7.9
MS
C
Gio
van
na
Container
27,103
Diesel
6177.6
32.2
10.7
13.4
Dieseloil(309ton),
interm
ediatefueloil
(1906ton)
0.49
9.4
P. Sinha et al. / Atmospheric Environment 37 (2003) 2139–2148 2143
percentage utilization changes from 85% to 25%. Since
the Royal Sphere was heading to port at Walvis Bay,
Namibia, it may well have slowed its speed and
decreased its percentage utilization of engine power,
resulting in higher hydrocarbon emissions.
5.3.4. Nitrogen oxides
Emissions of NOx from ships have been estimated to
account for up to B14% of nitrogen emissions from
fossil fuel combustion (Corbett et al., 1999), and hence
they are of global importance. Since NOx emissions
from ships are temperature-dependent, and more power-
ful combustion systems operate at higher temperatures,
the emission rate of NOx depends on the power of the
ship engine. The Royal Sphere and MSC Giovanna both
have six cylinder diesel engines, but since the MSC
Giovanna’s engine has 60% more power than the
Royal Sphere, the NOx emission factor for the MSC
Giovanna was greater than that from the Royal Sphere
(Table 2).
The high concentrations of NOx in the plumes from
the Royal Sphere and MSC Giovanna are consistent with
the much lower concentrations of O3 in the exhaust
directly above the ships (5–8 ppbv) than ambient O3
concentrations (23–27 ppbv), as measured by the Teco
49C. In the ship plumes, NO can react with O3 to form
NO2 and O2, thereby lowering O3 concentrations.
Downwind of the ships, the NOx, hydrocarbons, and
CO from ships (and other sources) react photochemi-
cally to form O3. Since O3 is an OH precursor, elevated
0 1 2 3 4 5 6 7
0
2
4
6
8
10 Royal SphereMSC Giovanna
CN
co
nce
ntr
atio
n (
in u
nits
of 1
04
cm-3)
Distance downwind of ship (km)
0.1 10.1
1
10
100
1000
10000
0.5
Royal SphereMSC GiovannaAmbient air
dN
/d(lo
gD
) (c
m-3)
Particle diameter D (micrometers)(b)
(a)
Fig. 2. (a) Condensation nucleus concentrations along the length of the plumes from the Royal Sphere, and the MSC Giovanna. (b)
Particle size distributions in the plumes directly above the Royal Sphere and MSC Giovanna and in the ambient marine air.
P. Sinha et al. / Atmospheric Environment 37 (2003) 2139–21482144
O3 downwind of ships will result in elevated OH and
increase the oxidation potential of the troposphere.
5.3.5. Sulfur dioxide
Sulfur dioxide emissions from ships are primarily
determined by the sulfur content of the fuel burned, so
that residual fuels produce higher SO2 emissions than
distillate fuels. Since the SO2 emission factor that we
derived for the MSC Giovanna (52.2 g kg�1 of fuel)
greatly exceeds that of the Royal Sphere (2.9 g kg�1 of
fuel), we conclude that at the time we sampled their
exhausts the Royal Sphere and MSC Giovanna were
burning distillate and residual fuels, respectively.
Carlton et al. (1995) reported SO2 emission factors for
ships in the form:
Emitted SO2 ðin g kg�1 of fuelÞ
¼ 20� ðpercentage of sulfur by weight in the fuelÞ: ð2Þ
Since marine fuel specifications require that residual
fuels have a maximum sulfur content of 5% by weight,
and that distillate fuels have a maximum sulfur content
of 2% by weight (IOS, 1987), typical upper limits for
SO2 emission factors for the burning of residual and
distillate fuel from Eq. (2) are: 100 and 40 g kg�1 of fuel,
respectively. Also, from (2) and the SO2 emission factors
measured in this study for the Royal Sphere and MSC
Giovanna, the percentage of sulfur by weight in the fuels
of the Royal Sphere and MSC Giovanna are deduced to
be 0.1% and 2.4%, respectively. The derived sulfur
fraction of the fuel used by the MSC Giovanna (2.4%)
exceeds the maximum specified sulfur content of
distillate fuels (2%) which further confirms our deduc-
tion that the MSC Giovanna was burning residual fuel at
the time of our measurements.
Hobbs et al. (2000) also found SO2 emission factors
from ships burning distillate fuel (6–24 g kg�1 of fuel) to
be substantially lower than for those burning residual
fuel (62725 g kg�1 of fuel). Substituting the SO2
emission factors given by Hobbs et al. (2000) into
Eq. (1), the percentages of sulfur by weight in distillate
and residual fuels used by the ships studied by Hobbs
et al. are deduced to be 0.3–1.1% and 2.871.1%,
respectively.
5.3.6. Black carbon
A single quartz filter was exposed to the exhausts from
both the Royal Sphere and MSC Giovanna. Analysis of
this filter yielded an average emission factor for black
Table 2
Emission factors of some gases and particles from the ships Royal Sphere and MSC Giovanna. Emission factors have units of grams of
species emitted per kilogram of fuel burned, except for CN, CN0.1–3mm, and CCN which have units of number of particles emitted per
kilogram of fuel burned
Fuel type Technique used for
measurement in this
studya
Royal Sphereb
(assumed to be
distillate fuel)
MSC Giovannac
(assumed to be
residual fuel)
Hobbs et al. (2000) Carlton et al. (1995)
Distillate fuel Residual fuel Residual and distillate
fuels
CO2 AFTIR 3135794 3176795 3170
CO GC/C 19.571.0 3.070.2 7.4
CH4 GC/C 5.470.1 2.67o0.1
NMHC GC/C 2.470.1 0.47o0.1
HC GC/C 7.870.2 3.070.1 2.4
NOx (as NO) AFTIR 22.371.1 65.573.3 2375 57–87
SO2 Teco 43S/GB 2.970.2 52.273.7 6–24 62725 20� (percentage of
sulfur by weight in
fuel)d
Black carbon Filter/GB (0.1870.02)e
CN TSI-3025A/GB (4.070.4)� 1016 (6.270.6)� 1016 (0.4–1.3)� 1016 (1.670.5)� 1016
CN0.1–3mm PMS PCASP-100X (1.170.1)� 1015 (5.170.5)� 1015
CCN (at 0.3%
supersaturation)
Thermal diffusion
chamber
(7.670.8)� 1014 (1.170.1)� 1015
aAFTIR=Airborne Fourier Transform Infrared Spectrometer; GC/C=gas chromatography via canisters; GB=grab bag.bEmission factors for the Royal Sphere are based on excess concentrations in the plume of 2.97 ppmv CO2, 29 ppbv CO, 14 ppbv
CH4, 6 ppbv NMHC, 31 ppbv NOx, 1.9 ppbv SO2, 0.6 mgm–3 black carbon, 7.18� 1010m�3 CN, 1.93� 109m–3 CN0.1�3 mm, and
1.35� 109m–3 CCN.cEmission factors for the MSC Giovanna are based on excess concentrations in the plume of 2.71 ppmv CO2, 4 ppbv CO, 6 ppbv
CH4, 1 ppbv NMHC, 82 ppbv NOx, 30.6 ppbv SO2, 0.6 mgm–3 black carbon, 9.94� 1010m–3 CN, 8.14� 109m–3 CN0.1–3mm, and
1.75� 109m–3 CCN.d In units of g kg�1 of fuel.eOne filter for black carbon analysis was exposed to the plumes from both ships.
P. Sinha et al. / Atmospheric Environment 37 (2003) 2139–2148 2145
carbon for the two ships of 0.18 g kg�1 of fuel. To our
knowledge, this is the first measurement of the emission
factor of black carbon from ocean-going ships. Carlton
et al. (1995) reported emission factors for total parti-
culate matter (TPM) from ships of 1.3 and 8.4 g kg�1 of
fuel burned for distillate fuel and residual fuel,
respectively. Taking the ratio of emission factors for
black carbon from this study and TPM given by Carlton
et al. we see that B4% of the particle mass released by
ships consist of black carbon. Using the same instru-
mentation and sampling strategies as in the present
study, Sinha et al. (2003) derived black carbon and TPM
emission factors for savanna fires in southern Africa of
0.3970.19 and 10.077.5 g kg�1 of fuel, respectively. As
was the case for ship exhausts,B4% of the particle mass
released by African savanna fires consisted of black
carbon.
5.3.7. Particles
Emission factors for three classes of particles are given
in Table 2: total number of particles with diameters
>0.003mm (CN), number of particles with diameters
from 0.1 to 3mm (CN0.1–3 mm), and number of cloud
condensation nuclei (CCN) at 0.3% supersaturation.
Emission factors from ships of CN0.1–3 mm and CCN
have not been reported previously.
Hobbs et al. (2000) found that the CN emission factor
for ships burning residual fuel ((1.670.5)� 1016 parti-
cles per kilogram of fuel) is higher, on average, than for
ships burning distillate fuel ((0.4–1.3)� 1016 particles per
kilogram of fuel). This is consistent with our measure-
ments on the Royal Sphere and MSC Giovanna (Table
2). The higher emission factors for CN reported here
((4–6.2)� 1016 particles per kilogram of fuel) than by
Hobbs et al. is consistent with the fact that our CN
measurements were made with a TSI 3025A ultrafine
condensation particle counter with a diameter range of
0.003–3mm, whereas, the CN measurements of Hobbs
et al. were made with a TSI 3760 condensation particle
counter with a diameter range of 0.011–3 mm.Shown in Fig. 2b are particle size distributions
measured in the plumes from the Royal Sphere, the
MSC Giovanna, and in the ambient marine air. The
number concentration of particles with diameters of
B0.1mm was over three orders of magnitude greater in
the plumes of the ships than in the ambient marine air.
The particle diameter mode of the effluents from the
diesel-powered Royal Sphere burning distillate fuel was
0.10mm and for the diesel-powered MSC Giovanna
burning residual fuel it was 0.12mm. Hobbs et al. (2000)measured a particle mode diameter of 0.04 mm in the
plume from a steam-turbine powered ship burning
distillate fuel and particle mode diameter from 0.06 to
0.1mm for diesel-powered ship burning residual fuel.
The ratios of CCN (at 0.3% supersaturation) to CN
for the Royal Sphere and MSC Giovanna are 19% and
18%, respectively. Hobbs et al. (2000) obtained a CCN/
CN ratio of 1877% for a ship burning residual fuel by
measuring DNd=DNtot; where DNd is the increase (above
ambient) in cloud drop concentrations in the ship track
and DNtot the sum of the increases (above ambient) of
cloud droplet and cloud interstitial aerosol concentra-
tions in the ship track. The CCN can nucleate cloud
droplets, and thereby increase the reflection of solar
radiation by clouds (Hobbs et al., 2000).
The SO2 and NOx emitted by ships may react
heterogeneously on particles to form SO42� and NO3
�.
Most heterogeneous reactions take place on accumula-
tion-mode particles (B0.1–3mm diameter), since these
particles account for most of the surface area of
atmospheric aerosol (Seinfeld and Pandis, 1998). The
CN0.1–3 mm emission factors for the Royal Sphere and
MSC Giovanna reported here (1.1� 1015 and 5.1� 1015
particles per kilogram of fuel, respectively) provide an
estimate of accumulation-mode particle emissions. If it
is assumed that all particles in the accumulation-mode
are spherical and have a diameter of 0.1 mm, the
emission factors for the surface area of these particles
are 34.6 and 160.2m2 kg�1 of fuel burned for the Royal
Sphere and MSC Giovanna, respectively.
6. Global implications
We can estimate the global emissions of various
species from ocean-going ships from the emission factors
given in Table 2 and annual world marine fuel usages of
(100–110)� 109 kg of residual fuel and (30–40)� 109 kg
of non-residual fuel (Corbett et al., 1999). In arriving at
these estimates, we assumed (based on the justifications
given above) that the MSC Giovanna was burning
residual fuel and the Royal Sphere was burning distillate
fuel when we sampled their plumes. The results are
shown in Table 3.
Our estimates of global emissions can be compared
with those of Corbett et al. (1999) for CO2, NOx, and
SO2 (Table 3). In view of the inherent uncertainties of
the estimates, the global emissions of CO2 and NOx (as
N) obtained in this study (97–124 and 3.3–4.2 Tg yr–1,
respectively) are not significantly different from those
obtained by Corbett et al. (123 and 2.66–4.00 Tg yr–1,
respectively). However, the annual flux of SO2 from
ships estimated by us (B2.5 Tg S yr�1) is significantly
lower than Corbett et al.’s estimate of 4.24Tg S yr�1.
However, since the sulfur fraction of the distillate fuel
(B0.1%) burned by the Royal Sphere, which is implied
by our SO2 emission factor for the Royal Sphere, is well
below the maximum legal sulfur content of distillate
fuels (2%) specified by IOS (1987), our estimate of
global SO2 emissions from ships is likely an under-
estimate.
P. Sinha et al. / Atmospheric Environment 37 (2003) 2139–21482146
Emissions from ocean-going ships are compared with
those from some other anthropogenic sources and from
natural sources in Table 3. Two major anthropogenic
emission sources are fossil fuel combustion and biomass
burning; major natural sources include the oceans and
vegetation. For several of the species measured in this
study (e.g., CO2, CO, CH4), emissions from ships are
minor compared to fossil fuel combustion. However, since
ship emissions occur primarily over relatively unpolluted
oceanic regions, they may have significant local and
regional impacts, particularly in the Southern Hemisphere.
In the case of NOx and SO2, ocean-going ships
constitute a globally important emission source: they
emit B10–14% of the NOx emissions from fossil fuel
combustion and B3–4% of SO2 emissions from fossil
fuel combustion. Ship emissions of NOx are B40% of
those from biomass burning, and emissions of SO2 from
ships are B70% of those from biomass burning. Using
Carlton et al.’s (1995) emission factor for NOx (which is
in reasonable agreement with our measurements—see
Table 2), Lawrence and Crutzen (1999) concluded that
emissions from ships produce NOx enhancements of
more than 100-fold in busy ship lanes, and by more than
a factor of two over most of the North Atlantic, North
Pacific, and Indian Oceans. Kasibhatla et al. (2000)
reassessed the effects of ship emissions on NOx
concentrations in the marine boundary layer using
Carlton et al.’s emission factor but updated information
on ship positions. The impact of ships on NOx were
found to be more widespread, but the peak enhance-
ments less than those suggested by Lawrence and
Crutzen. However, Kasibhatla’s model-simulated con-
centrations of NOx over the central Atlantic Ocean were
much greater than in situ measurements. The reason for
this discrepancy is unclear.
We have reported here the first measurements of
emissions of black carbon, CN0.1–3 mm, and CCN (at
0.3% supersaturation) from ships. The black carbon
emissions from ships (B0.02 Tg yr�1) are small in
relation to both fossil fuel combustion (B6–8Tg yr�1)
and biomass burning (B4.8Tg yr�1). However, since
there are no oceanic sources of black carbon, emissions
of black carbon from ships could be important in direct
radiative forcing over the oceans. Also, particle emis-
sions from ships can affect cloud structures and cloud
radiative properties over major shipping lanes (Hobbs
et al., 2000).
Acknowledgements
We thank all members of the UW-CARG and the
pilots of the Convair-580 for help in obtaining
measurements, Dan Jaffe for help in calibrating the
gas instruments, Donald Blake for analyses of the GC/C
samples, and Richard Gasparovic for help in the
identification of ships.
This study was carried out as part of the SAFARI
2000 Southern African Regional Science Initiative.
Research supported by grants NAG5-9022 and
NAG5-7675 from NASA’s Radiation Science Program,
and grants ATM-9901624 and ATM-9900494 from
NSF’s Division of Atmospheric Sciences.
References
Andreae, M.O., Merlet, P., 2003. Emission of trace gases and
aerosols from biomass burning. Global Biogeochemistry
Cycles 15, 955–966.
Table 3
Global emissions from ocean-going ships compared with some other anthropogenic sources and natural sources. Units are Tg yr–1
except for CN, CN0.1–3mm and CCN, which are numbers of particles per year
Ocean-going ships Fossil fuela Biomass
burningbOceansa Natural
Vegetationa
This study Corbett et al.
(1999)
CO2 (as C) 97–124 123.46 63007400 3655
CO 0.76–1.06 650 690 50 150
CH4 0.37–0.47 75–110 39 10–15 115–237
NMHC 0.09–0.14 49
NOx (as N) 3.3–4.2 3.08 (2.66–4.00) 33.0 9.7
SO2 (as S) 2.2–2.9 4.24 (3.29–5.61) 76 3.5
Black carbon 0.019–0.026 6–8 4.8
CN (6.0–8.4)� 1027 2.9� 1028
CN0.1–3mm (4.4–6.1)� 1026
CCN (at 0.3%
supersaturation)
(1.0–1.5)� 1026 1.7� 1028
a IPCC (2001).bAndreae and Merlet (2003).
P. Sinha et al. / Atmospheric Environment 37 (2003) 2139–2148 2147
Capaldo, K., Corbett, J.J., Kasibhatla, P., Fischbeck, P.,
Pandis, S.N., 1999. Effects of ship emissions on sulphur
cycling and radiative climate forcing over the ocean. Nature
400, 743–746.
Carlton, J.S., Danton, S.D., Gawen, R.W., Lavender, K.A.,
Mathieson, N.M., Newell, A.G., Reynolds, G.L., Webster,
A.D., Wills, C.M.R., Wright, A.A., 1995. Marine exhaust
emissions research programme. Lloyd’s Register Engineer-
ing Services, London, p. 63.
Colman, J.J., Swanson, A.L., Meinardi, S., Sive, B.C., Blake,
D.R., Rowland, F.S., 2001. Description of the analysis of a
wide range of volatile organic compounds in whole air
samples collected during PEM-tropics A and B. Analytical
Chemistry 73, 3723–3731.
Corbett, J.J., Fischbeck, P., 1997. Emissions from ships. Science
278, 823–824.
Corbett, J.J., Fischbeck, P.S., Pandis, S.N., 1999. Global
nitrogen and sulfur inventories for ocean-going ships.
Journal of Geophysical Research 104, 3457–3470.
Ferek, R.J., Hegg, D.A., Hobbs, P.V., Durkee, P., Nielsen, K.,
1998. Measurements of ship-induced tracks in clouds off the
Washington coast. Journal of Geophysical Research 103,
23199–23206.
Gundel, L.A., Dod, R.L., Rosen, H., Novakov, T., 1984. The
relationship between optical attenuation and black carbon
concentrations for ambient and source particles. The
Science of the Total Environment 36, 197–202.
Hobbs, P.V., Garrett, T.J., Ferek, R.J., Strader, S.R., Hegg,
D.A., Frick, G.M., Hoppel, W.A., Gasparovic, R.F.,
Russell, L.M., Johnson, D.W., O’Dowd, C., Durkee, P.A.,
Nielsen, K.E., Innis, G., 2000. Emissions from ships with
respect to their effects on clouds. Journal of Atmospheric
Sciences 57, 2570–2590.
Intergovernmental Panel on Climate Change (IPCC), 2001.
Climate Change 2001: The Scientific Basis. Cambridge
University Press, Cambridge, UK, p. 881.
International Organization for Standardization (IOS), 1987.
International Standard, Petroleum Products, Fuels (Class
F), Specifications of Marine Fuels. IOS, Geneva, Switzer-
land, p. 14.
Kasibhatla, P., Levy II, H., Moxim, W.J., Pandis, S.N.,
Corbett, J.J., Peterson, M.C., Honrath, R.E., Frost, G.J.,
Knapp, K., Parrish, D.D., Ryerson, T.B., 2000. Do
emissions from ships have a significant impact on concen-
trations of nitrogen oxides in the marine boundary layer?
Geophysical Research Letters 27, 2229–2232.
King, M.D., Radke, L.F., Hobbs, P.V., 1993. Optical proper-
ties of marine stratocumulus clouds modified by ships.
Journal of Geophysical Research 98, 2729–2739.
Lawrence, M.G., Crutzen, P.J., 1999. Influence of NOx
emissions from ships on tropospheric photochemistry and
climate. Nature 402, 167–170.
Lloyd’s Register of Shipping, 2002. Sea-Web, http://www.sea-
web.org.
Radke, L.F., Hegg, D.A., Lyons, J.H., Brock, C.A., Hobbs,
P.V., 1988. Airborne measurements on smoke from bio-
mass burning. In: Hobbs, P.V., McCormick, M.P. (Eds.),
Aerosols and Climate. A. Deepak, Hampton, VA,
pp. 411–422.
Radke, L.F., Coakley Jr., J.A., King, M.D., 1989. Direct and
remote sensing observations of the effects of ships on
clouds. Science 247, 1146–1149.
Rosen, H., Novakov, T., 1983. Optical-transmission through
aerosol deposits on diffusely reflective filters—a method for
measuring the absorbing component of aerosol-particles.
Applied Optics 22, 1265–1267.
Seinfeld, J.H., Pandis, S.N., 1998. Atmospheric Chemistry and
Physics. Wiley, New York, p. 1326.
Sinha, P., Hobbs, P.V., Yokelson, R.J., Bertschi, I.T., Blake,
D.R., Simpson, I.J., Gao, S., Kirchstetter, T.W., Novakov,
T., 2003. Emissions of trace gases and particles from
biomass burning in southern Africa. Journal of Geophysical
Research 108, doi: 10.1029/2002JD002325, in press.
Tuttle, K.L., 1995. Combustion-generated emissions in marine
propulsion systems. Proceedings of the SNAME 1994
Environmental Symposium—Ship Design and Operation
in Harmony with the Environment. Society of
Naval Architects and Marine Engineers, Jersey City, NJ,
pp. 311–323.
Twomey, S., 1977. Influence of pollution of the short-wave
albedo of clouds. Journal of Atmospheric Sciences 34, 1149–
1152.
Yokelson, R.J., Bertschi, I.T., Christian, T.J., Hobbs, P.V.,
Ward, D.E., Hao, W.M., 2003. Trace gas measurements
in nascent, aged, and cloud-processed smoke from
African savanna fires by airborne Fourier transform
infrared spectroscopy. Journal of Geophysical Research
108, 8478.
P. Sinha et al. / Atmospheric Environment 37 (2003) 2139–21482148