Access to this full-text is provided by Copernicus Publications on behalf of European Geosciences Union.
Content available from Atmospheric Chemistry and Physics
This content is subject to copyright.
Atmos. Chem. Phys., 19, 13611–13626, 2019
https://doi.org/10.5194/acp-19-13611-2019
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
Surveillance of SO2and NO2from ship emissions by MAX-DOAS
measurements and the implications regarding fuel sulfur content
compliance
Yuli Cheng1, Shanshan Wang1,2, Jian Zhu1, Yanlin Guo1, Ruifeng Zhang1, Yiming Liu1, Yan Zhang1,2,3, Qi Yu1,2,
Weichun Ma1,2, and Bin Zhou1,2,3
1Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science
and Engineering, Fudan University, Shanghai, 200433, China
2Shanghai Institute of Eco-Chongming (SIEC), No.3663 Northern Zhongshan Road, Shanghai, 200062, China
3Institute of Atmospheric Sciences, Fudan University, Shanghai, 200433, China
Correspondence: Shanshan Wang (shanshanwang@fudan.edu.cn) and Bin Zhou (binzhou@fudan.edu.cn)
Received: 17 April 2019 – Discussion started: 26 April 2019
Revised: 18 September 2019 – Accepted: 30 September 2019 – Published: 11 November 2019
Abstract. Due to increased concerns regarding air pollu-
tants emitted from shipping, feasible technology for the
surveillance of these pollutants is in high demand. Here,
we present shore-based multi-axis differential optical absorp-
tion spectroscopy (MAX-DOAS) measurements of SO2and
NO2emitted from ships under different traffic conditions in
China’s ship emission control areas (ECAs) in Shanghai and
Shenzhen, China. Three typical measurement sites were se-
lected in these two regions to represent the following emis-
sion scenarios: ships docked at berth, ships navigating in an
inland waterway and inbound/outbound ships in a deep-water
port. Using 2-D scanning, the observations show that SO2
and NO2hot spots can be quickly and easily located from
multiple berths. Although MAX-DOAS measurements can
not distinguish plumes from specific ships in the busy ship-
ping lanes of the inland waterway area, they certify that vari-
ations in the SO2and NO2levels are mainly impacted by
the ship traffic density and the atmospheric dispersion condi-
tions. In the open water area, which has a lower vessel den-
sity, MAX-DOAS measurements can capture the pulse sig-
nal of ship-emitted SO2and NO2very well; they can also
characterize the peak’s altitude and the insistent duration of
the individual ship plumes. Combined with the ship activ-
ity data, information on the rated power of the engine and
the fuel sulfur content, it was found that the SO2/NO2ra-
tio in a single plume is usually low (< 1.5) for inbound ves-
sels due to the usage of the auxiliary engine, which has less
power and uses “clean” fuel with a low sulfur content. Thus,
an unexpectedly high SO2/NO2ratio implies the use of fuel
with a sulfur content exceeding the regulation limits. There-
fore, the observed SO2/NO2ratio in the plume of a single
ship can be used as an index to indicate compliance (or non-
compliance) with respect to the fuel sulfur content, and the
suspicious ship can then be flagged for further enforcement.
Combining the ship emissions estimated by actual operation
parameters and the logical sulfur content, shore-based MAX-
DOAS measurements will provide a fast and more accurate
way to surveil ship emissions.
1 Introduction
Sulfur dioxide (SO2) and nitrogen dioxide (NO2) are impor-
tant air pollutants, and are also recognized as non-negligible
components of ship emissions (Corbett et al., 1999; Endresen
et al., 2003; Eyring et al., 2010; Matthias et al., 2010). Both
of these species can engage in atmospheric chemical reac-
tions to produce aerosols and acid rain, and also have neg-
ative effects on air quality, the climate system and human
health, as well as contributing to the acidification of terres-
trial and marine ecosystems (Berglen et al., 2004; Seinfeld
and Pandis, 2006; Singh, 1987). Moreover, NO2is also the
key substance involved in the formation of photochemical
smog (Dimitriades, 1972).
Published by Copernicus Publications on behalf of the European Geosciences Union.
13612 Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS
With the rapid growth of marine transportation, air pollu-
tion has become the most challenging environmental issue
in the shipping industry, specifically regarding the emission
of CO2, SO2, NOx, particulate matter and greenhouse gases.
CO2and NO are the main pollutants emitted by ships, and
NO is rapidly converted to NO2by reaction with O3(Eyring
et al., 2005; Becagli et al., 2012; Coggon et al., 2012; Diesch
et al., 2013; Lauer et al., 2007; Seyler et al., 2017). Eyring et
al. (2010) reported that ships contribute 15 % of global NOx
emissions and 4 %–9 % of SO2emissions.
Regarding the spatial distribution of these pollutants,
global hot spots with high SO2and NO2emissions have been
identified in the Eastern China Sea and the Southern China
Sea, in marine areas in southeastern and southern Asia, in the
Red Sea, in the Mediterranean, in the North Atlantic near the
European coast, and along the western coast of North Amer-
ica, among others (Johansson et al., 2017).
In China, ship-emitted pollutants play important roles re-
garding the air quality, human health and climate (Lai et al.,
2013; Liu et al., 2016; Yang et al., 2007). They not only af-
fect the air quality in coastal areas, but even influence inland
areas hundreds of kilometers from emission sources (Lv et
al., 2018). Port cities are most affected by ship pollution, fol-
lowed by cities along rivers. For example, ship-emitted SO2
and NOxwere shown to contribute 12.4% and 11.6 % of the
total emissions of the whole city of Shanghai in 2012, re-
spectively, while up to 64 % of primary PM2.5has been at-
tributed to ships at Shanghai Port; this pollution can then also
be transported to inland regions (Fan et al., 2016; Zhao et al.,
2013).
In order to reduce the negative impacts of ship emissions,
the EU and the US have implemented regulations in an ef-
fort to decrease ship emissions (Kattner et al., 2015); among
these regulations, fuel quality regulation has proven to be
the most effective measure for addressing the issue of sulfur
oxide (SOx) and particulate matter (PM) emission in many
countries. In addition, the International Maritime Organiza-
tion (IMO, 2009) has also set up multiple emission control
areas (ECAs) worldwide. By 2020, the maximum fuel sul-
fur content (FSC) is set to be 0.50 % S m/m worldwide; it is
worth noting that the current maximum FSC in ECAs on the
US coast and in Europe is 0.10 %S m/m, whereas in China’s
ECAs it is 0.50 % S m/m. The regulations also set limits re-
garding pollutant emissions, such as NOxand CO2, in ex-
haust gas. Thus, an exhaust gas treatment system could be
another option to reduce the emissions of these species. Since
1 January 2017, ships berthed at the core ports of three desig-
nated domestic emission control areas (DECAs) in the Pearl
River Delta (PRD), the Yangtze River Delta (YRD) and the
Bohai Rim (Beijing–Tianjin–Hebei area) in China have been
restricted to fuels with a sulfur content of less than or equal to
0.50 % S m/m (MOT, 2015). However, as of 1 January 2019
ships entering the ECAs are restricted to fuels with a sulfur
content of no more than 0.50 %S m/m, regardless of whether
they are sailing or docking. Currently, scrubbers are also an
alternative method of reducing ship emissions in China. As a
consequence, it is obvious that a reliable and practical moni-
toring system is urgently required for the implementation of
ECA regulations.
The most commonly used options for monitoring ship
emissions can be classified into two categories: estimates
based on activity data or written documentation, and mea-
surements of fuel samples and exhaust gas made onboard the
ship. Basically, the continuous online monitoring of fuel and
exhaust gas onboard is the most effective and accurate means
of supervision, but is much less feasible in practice. With re-
spect to the regulatory party, fuel sampling and document in-
spection are currently the most commonly used supervision
measures, and the sulfur content in the fuel is usually quickly
detected after a ship has docked (in roughly 10 min). Other
technical methods have also been developed to determine
both SO2and NOxemissions, including a new type of ship
exhaust gas detection technology that mounts a portable snif-
fer instrument to a ship or helicopter (Beecken et al., 2015;
Berg et al., 2012; Murphy et al., 2009; Villa et al., 2016). Al-
ternatively, shore-based remote sensing is another effective
way of measuring ship plumes and estimating the sulfur con-
tent in these plumes as ships pass in shipping lanes or dock
at berth (Kattner et al., 2015; Seyler et al., 2017).
Remote sensing techniques have the advantages of fast de-
tection, easy operation and high automation. In addition to
the passive “sniffing” method using in situ instrumentation,
optical remote sensing techniques, such as differential optical
absorption spectroscopy (DOAS), light detection and ranging
(LIDAR) and the ultraviolet camera (UV-CAM) technique,
can detect the variation of light properties after interaction
with the exhaust plume and, thus, the corresponding SO2
and NO2emission levels in the plume (Balzani Lööv et al.,
2014; Seyler et al., 2017). LIDAR systems can be used to re-
trieve a 2-D concentration distribution by scanning through
the ship plume and by combing the wind and concentration
profiles to obtain the ship emissions. McLaren et al. (2012)
employed an active long-path DOAS technique to measure
the SO2/NO2ratios in ship plumes and speculated on their
relationship with the sulfur content of fuels. A UV camera
has also been successfully applied to measure the SO2con-
centrations and emission rates of moving and stationary ship
plumes (Prata, 2014).
The DOAS technique allows for the identification and
quantification of the absorption of a variety of species
that show characteristic absorption features in the measured
wavelength range (Platt and Stutz, 2008). It has been widely
used for trace gas measurements over several decades, es-
pecially for very mature NO2and SO2(Edner et al., 1993;
Mellqvist and Rosén, 1996; Platt et al., 1979). As an ex-
panded apparatus, multi-axis differential optical absorption
spectroscopy (MAX-DOAS) measurements are highly sensi-
tive to aerosols and trace gases in the lower troposphere, as
the instrument observes scattered sunlight at different view-
ing angles close to the horizontal and zenith directions (Hön-
Atmos. Chem. Phys., 19, 13611–13626, 2019 www.atmos-chem-phys.net/19/13611/2019/
Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS 13613
ninger et al., 2004; Ma et al., 2013; Sinreich et al., 2005;
Wang et al., 2014). Due to its portability, the MAX-DOAS
instrument can be carried onto ships to observe the verti-
cal column densities (VCDs) of NO2and SO2during the
cruise, as high levels of pollutants have been found close
to busy ports and dense shipping lanes (Hong et al., 2018;
Schreier et al., 2015; Takashima et al., 2012; Tan et al., 2018).
In addition, MAX-DOAS has been successfully employed
for the direct monitoring of shipping emissions. Premuda et
al. (2011) used ground-based MAX-DOAS measurements to
evaluate the NO2and SO2levels in ship plumes discharged
from individual ships in the Giudecca Strait of the Venetian
Lagoon. Seyler et al. (2017) utilized MAX-DOAS to per-
form long-term measurements of NO2and SO2from ship-
ping emissions in the German Bight, and evaluated the re-
duction in SO2levels after the implementation of stricter fuel
sulfur limits.
In this study, shore-based MAX-DOAS measurements
were employed to measure the NO2and SO2in ship plumes
in different ship traffic environments in Shanghai and Shen-
zhen, China. Combined with photographs taken by the in-
strument’s camera and AIS (Automatic Identification Sys-
tem) information, it was verified that the emissions of ships
at berth, those from ships passing through an inland water-
way and those from ships in open-sea areas can be success-
fully detected. The measurements can also provide fuel sul-
fur content information for individual ships by comparing the
NO2and SO2emitted in the plume (considering the effects
of plume age) with fuel sample analysis and the ship ac-
tivity data. This suggests that the shore-based MAX-DOAS
method is a feasible and reliable method for surveilling ship-
emitted SO2and NO2and, further, enables compliance or
noncompliance to be established with respect to fuel sulfur
content regulations.
2 Measurements and method
2.1 Instrument setup and sites
In this study, the MAX-DOAS instrument was designed and
assembled by the authors (Zhang et al., 2018). It mainly con-
sists of a receiving telescope, a spectrometer (Ocean Op-
tics, QE65 Pro) and a computer to control the measurements.
Driven by a 2-D stepper motor system, the telescope can col-
lect scattered sunlight from different elevation angles in the
vertical direction and different azimuth angles in the horizon-
tal direction. The lens then converges the scattered light onto
the fiber bundle connected to the spectrometer. Following
this, the sunlight received is dispersed by a grating, detected
by a CCD detector and recorded by the spectrometer cover-
ing the wavelength range from 300 to 480nm with a reso-
lution about 0.5 nm full width at half maximum (FWHM).
As a new design feature, a camera has been configured on
the MAX-DOAS apparatus that moves coaxially with the re-
Figure 1. The YRD and PRD domestic emission control areas (DE-
CAs) in China, and the locations of the MAX-DOAS measurements
in the coastal cities of Shanghai and Shenzhen: Waigaoqiao Port
and Wusong Wharf in Shanghai, and Yantian Port in Shenzhen. The
viewing direction of instrument azimuth angle is indicated using a
red arrow. Panels (b) to (d) are sourced from ©Google Earth.
ceiving telescope and can record the scene and sky conditions
viewed by the telescope. The scanning of the telescope can
be set in a sequence of several elevation angles that begins
close to horizontal and at 90◦and then moves to next az-
imuth angle for another vertical scanning sequence. Due to
the different ship traffic conditions, the types of ship passing
in inland waterways and at seaside ports are different with
respect to size and tonnage. Therefore, the configuration of
the observing geometric angles was adjusted depending on
the ship conditions (see Table 1).
The MAX-DOAS measurements of ship emissions were
performed in two typical port cities – Shanghai and Shen-
zhen – in China. As shown in Fig. 1a, sea areas surround-
ing Shanghai and Shenzhen are located in the Yangtze River
Delta and Pearl River Delta ECAs, respectively. In Shanghai,
two different ship traffic scenarios were considered: ships
at berth in the Waigaoqiao container port area (31.36◦N,
121.58◦E; Fig. 1b), and ships passing through the inland wa-
terway in the downstream region of Huangpu River around
Wusong (31.37◦N, 121.50◦E; Fig. 1c). In Shenzhen, the
measurements were carried out in the deep-water port of
Yantian (114.29◦E, 22.56◦N; Fig. 1d). More details about
the environments and operational configurations with respect
to the measurements are given in Table 1.
www.atmos-chem-phys.net/19/13611/2019/ Atmos. Chem. Phys., 19, 13611–13626, 2019
13614 Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS
Table 1. Measurement details and the operational configurations of the MAX-DOAS.
Sites Locations and periods Operations∗Environment types
Waigaoqiao, 31.36◦N, 121.58◦E; AZ: 26 to 34◦Viewing the berths.
Shanghai 28/08/2017 ELE: 3, 4, 5, 6 and 7◦Ships: container ships
Spectrum temporal resolution: 15–30 s
Completed scanning cycle: 15 min
Wusong, 31.37◦N, 121.50◦E; AZ: 85◦Viewing the inland waterway
Shanghai 30/12/2017–18/05/2018 ELE: 0, 1, 2, 3, 4, 5, 6, 8 and 65◦with a high traffic volume.
Spectrum temporal resolution: 40 s Ships: a wide variety of ships
Completed scanning cycle: 7 min and small in size
Yantian, 114.29◦E, 22.56◦N; AZ: 75◦Viewing open-sea areas
Shenzhen 23/05/2018–30/06/2018 ELE: 2, 3, 5, 7, 10, 15, 30 and 90◦with a lower traffic volume.
Spectrum temporal resolution: 60 s Ships: primarily container ships
Completed scanning cycle: 9 min
∗AZ denotes the azimuth angle in the horizontal direction; ELE denotes the elevation angle in the vertical direction.
2.2 DOAS spectral analysis
The DOAS algorithm is basically based on the Beer–Lambert
law, which describes the extinction of radiation through the
atmosphere (Platt and Stutz, 2008). The MAX-DOAS instru-
ment observes scattered sunlight from various viewing direc-
tions and records the spectrum (e.g., Hönninger et al., 2004;
Sinreich et al., 2005). The spectral analysis generates the
measured SCD (slant column density), defined as the integral
of the trace gas concentration along the entire optical path
including the SCDs in the troposphere and the stratosphere
(e.g., Platt and Stutz, 2008; Wagner et al., 2010). The strato-
spheric absorption is assumed to be at the same level in all
spectra taken within one scan cycle; therefore, we generally
choose the spectrum with the lowest less trace gas absorption
as the reference (such as the spectrum measured in zenith
direction). The slant column concentration of the trace gas
measured at each lower elevation angle (α) is represented by
the DSCD (differential SCD), which is the gas information
of the measured slant column densities minus background
densities in the reference spectrum:
DSCD(α) =SCD(α) −SCD(ref)
=SCD(α)trop +SCDstrat −SCD(ref)trop
−SCDstrat
=SCD(α)trop −SCD(ref)trop.(1)
Based on the DOAS principle, the measured scattered sun-
light spectra are analyzed using the QDOAS spectral fit-
ting software, which was developed by the Royal Belgian
Institute for Space Aeronomy (BIRA-IASB) (http://uv-vis.
aeronomie.be/software/QDOAS/, last access: 1 Novem-
ber 2019). The strong absorption band of SO2is below
325 nm, where NO2absorption are relatively weak. There-
fore, the fitting wavelength intervals for SO2and NO2are
307.5–320 nm and 338–370 nm, respectively. Although the
DSCDs generated are related to the wavelength of the fit-
ting interval, the usage of the SO2/NO2ratios of DSCDs re-
trieved at different spectral ranges will not be impacted by the
effect of wavelength dependency. Trace gases with absorp-
tions in the relevant fitting windows and ring spectrum were
included. The details of the spectral fitting configuration are
listed in Table 2. Wavelength calibration was performed us-
ing a high-resolution solar reference spectrum (Chance and
Kurucz, 2010). The offset and the signal of the dark current
were measured every night and were automatically extracted
from the measured spectra before spectral analysis. Conse-
quently, the DSCDs of SO2and NO2were acquired by tak-
ing the measured spectrum at 90◦as the Fraunhofer reference
spectrum.
Figure 2 shows the typical spectral fitting of measured
spectra with and without ship plume contamination. The ob-
vious absorbing structures of SO2and NO2as well as fairly
low residuals can be observed in both clean (collected at el-
evation angle of 5◦at 10:39LT on 22 June 2018) and pol-
luted spectrum (collected at elevation angle of 5◦at 09:53 LT
on 22 June 2018). By contrast, the retrieved SO2and NO2
DSCDs of 8.11×1016 and 3.08×1016 molec cm−2in the pol-
luted case are significantly higher than those of 2.24 ×1016
and 1.61 ×1016 molec cm−2under clean conditions. This
demonstrates the high sensitivity of the measurements to ship
plumes and the good performance of the spectral fitting. In
this study, a threshold of the residual of <1 ×10−3was used
to screen out any cases of unsatisfactory spectral fitting; fol-
lowing this screening process 94.57 % of the NO2DSCDs
and 76.26 % of SO2fitting results remained for further dis-
cussion. The uncertainties in the spectral analysis of SO2
were higher due to the weak scatter intensity of sunlight and
lower signal-to-noise ratio at shorter wavelengths.
Atmos. Chem. Phys., 19, 13611–13626, 2019 www.atmos-chem-phys.net/19/13611/2019/
Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS 13615
Table 2. The configuration of spectral fitting for SO2and NO2.
Parameters SO2NO2
Fitting window 307.5–320 nm 338–370 nm
NO2298 K (Vandaele et al., 1998) 298 K (Vandaele et al., 1998)
SO2293 K (Bogumil et al., 2003) /
O4/ 293 K (Thalman and Volkamer, 2013)
O3223 and 243 K (Serdyuchenko et al., 2014) 223 K (Serdyuchenko et al., 2014)
BrO / 293 K (Fleischmann et al., 2004)
CH2O 298 K (Meller and Moortgat, 2000) 298 K (Meller and Moortgat, 2000)
Ring Calculated by QDOAS Calculated by QDOAS
Polynomial degree 3 5
Intensity offset Constant Constant
Figure 2. Typical DOAS spectral fitting for SO2and NO2. Panels (a) and (b) show spectrum collected at an elevation angle of 5◦at 10:39 LT
on 22 June 2018 under clean conditions, whereas panels (c) and (d) are spectrum measured at an elevation angle of 5◦at 09:53 LT on
22 June 2018 under the influence of ship plume pollution. Black lines show the measured atmospheric spectrum, and the red line shows the
reference absorption cross section.
2.3 MAX-DOAS measurements for ship emissions
For ship emission measurements, the DSCDs of pollutants
at low elevation angles should express the change in the
integrated concentrations along the light path after con-
tamination by the exhaust plume, which collects scattered
sunlight passing through ship plumes. Figure 3a depicts a
schematic diagram of ground-based MAX-DOAS measure-
ments of ship emissions. The telescope is pointed towards
the shipping lanes or in the direction of a ship that is passing
through. Consequently, the spectra measured at a low eleva-
tion angle will be impacted by the plumes of ship emissions.
In order to better demonstrate the background concentra-
tion of NO2and SO2, several typical observation cycles from
29 June were selected as examples. Figure 3b and c show the
vertical distributions of NO2and SO2DSCDs with elevation
angle when there is a ship passing through and when no ship
is present, respectively. It can be observed that the DSCDs of
NO2and SO2decreased slowly with increasing angle under
clean conditions, during which the maximum values of the
NO2and SO2DSCDs are 5.03 ×1016 molec cm−2at an ele-
vation of 3◦and 1.78×1016 molec cm−2at an elevation of 2◦,
respectively. In contrast, the NO2and SO2DSCDs increased
significantly when ships passed through, showing maximum
NO2and SO2DSCD values of 7.36 ×1016 molec cm−2and
www.atmos-chem-phys.net/19/13611/2019/ Atmos. Chem. Phys., 19, 13611–13626, 2019
13616 Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS
4.15 ×1016 molec cm−2at an elevation of 5◦, respectively;
the highest value of SO2generally appeared between an ele-
vation angle of 5 and 10◦.
3 Results and discussion
3.1 Identifying ship emissions at berth
The measurement site at the Waigaoqiao container terminal
is located on the southern bank of the Yangtze River, close to
the confluence of the Yangtze and Huangpu rivers. The ter-
minal has a total quay length of more than 1 km, and its three
container berths are able to accommodate fifth- and sixth-
generation container ships. The terminal’s location means
that it is an important traffic route for ships entering or leav-
ing the Yangtze River, the Shanghai Port and the Waigaoqiao
Wharf. Ship emission are also the only obvious source of
SO2or NO2in this area.
In order to detect the emissions of ship at berths, the MAX-
DOAS instrument is placed on a fifth floor of the Pudong
MSB (Maritime Safety Bureau) building. The distance be-
tween the instrument and the berths is about 1.4 km. As the
view from the building is not obscured, multiple berths are in
the MAX-DOAS instrument’s direct field of view. Consider-
ing the size and chimney height of berthed ships, the MAX-
DOAS telescope was set to scan vertically in sequence at 3,
4, 5, 6 and 7◦(indicated by angle αin Fig. 4). In the horizon-
tal direction, the telescope ranged from 26 to 34◦(the view-
ing angle from north in the clockwise direction) and yielded
a range of angle β. After completing one full scanning se-
quence in both the vertical and horizontal, a 2-D distribution
of DSCDs in the instrument’s field of view can be generated.
To avoid interference from pollutants’ absorptions in the ref-
erence spectrum, the spectrum measured at azimuth angle of
10◦was considered as the reference background spectrum
(no direct pollution from ship emissions).
Figure 5a and b show the respective spatial distributions
of the SO2and NO2DSCDs in the horizontal and vertical
directions during a complete scanning sequence. Large spa-
tial gradients can be observed for both SO2and NO2levels,
and the pollutant concentrations are generally higher at lower
elevation angles and decline with an increase in height. The
highest SO2levels, i.e., DSCDs up to 2.5×1016 molec cm−2,
appeared at a horizontal azimuth of 31◦and an elevation of 3◦
and attenuated toward the upper left (see Fig. 5a). Similarly,
hot spots of NO2with DSCDs of 7.0–8.0×1016 molec cm−2
were centered between 31◦and 33◦in the horizontal at an
elevation of 3◦, and decreased in the periphery. It should be
noted that the hot spots of the SO2and NO2distributions are
shifted to the left accordingly, whereas the height is raised.
This implies that plumes containing SO2and NO2emitted
at the bottom of the observational field of view, disperse and
dilute in an upper-left direction, during which the wind at
this test site mainly came from the south. Combined with the
real scene, shown in Fig. 5c, the dashed rectangle indicates
the range of the MAX-DOAS telescope scanning sequence.
It can be seen that there are smoke clusters discharged by
a ship in the right-hand section of the picture, which corre-
sponds to the azimuth angle between 31 and 33◦; under the
action of the wind, the plume then spreads to the left of the
observational view.
As a full 2-D scanning sequence in the horizontal and ver-
tical directions took about 15 min, more than 10 cycles could
be performed in total during an afternoon. In view of the pre-
viously identified emission source position, and considering
that the NO2and SO2hot spots in each 2-D distribution are
related to the azimuth of the berth where the ship is docked
and the corresponding ship’s operation status, the DSCDs of
NO2and SO2observed at an elevation of 4◦and an azimuth
angle of between 31 and 33◦were selected to display the
temporal pattern of emissions at berth without averaging. In
general, the level of the NO2DSCDs was much higher than
that of SO2; this is due to the fact that there were consider-
able NOxemissions from port trucks between the berth and
the instrument, whereas there were no other obvious emis-
sion sources of SO2in the area. In order to show the vari-
ations in the DSCDs with less interference due to changes
in the light path, we used a mathematical method to remove
the steady change from the trend lines of the NO2and SO2
DSCDs, and kept the residual after background subtraction
(see Fig. 6). The baseline is modeled as a low-pass signal,
whereas the series of peaks is modeled sparsely with sparse
derivatives. Moreover, to account for the positivity of peaks,
both asymmetric and symmetric penalty functions were uti-
lized (Ning et al., 2014). Following this process, four signif-
icant increases in the SO2levels can be observed during the
afternoon, accompanied by NO2enhancements at approxi-
mately the same moments, which can be verified by the real
scene photographs that evidently show the plumes emitted
from the expected exhaust position.
Therefore, it can be concluded that the concentration of
NO2and SO2gases contained in the plumes emitted by the
container ships and the corresponding discharge position at
berth were identified and monitored remotely by the 2-D
MAX-DOAS observations. This application of 2-D MAX-
DOAS is similar to the imaging differential optical absorp-
tion spectroscopy (IDOAS) technique, which is also used to
map the 2-D spatial distribution of polluted gases, such as the
distribution of SO2in plumes from industrial point sources
(General et al., 2014; Pikelnaya et al., 2013). This suggests
that the 2-D DOAS technique has the potential to measure
the polluted gases mapping from the ships.
3.2 Ship emissions in an inland waterway
In addition to ocean-going ships, vessels in inland waterways
also significantly contribute to the amount of ship emissions
present in a region (Kurtenbach et al., 2016; Pillot et al.,
2016; Zhang et al., 2017). In order to consider emissions
Atmos. Chem. Phys., 19, 13611–13626, 2019 www.atmos-chem-phys.net/19/13611/2019/
Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS 13617
Figure 3. (a) A schematic diagram of the MAX-DOAS measurement geometry for monitoring ship emissions, and the distributions of
(b) NO2and (c) SO2DSCDs with elevation angle on 29 June 2018.
Figure 4. The observational geometry of the MAX-DOAS for iden-
tifying the emissions of ships at berth in the Waigaoqiao port,
Shanghai: (a) top view and (b) side view.
from an inland waterway, the MAX-DOAS instrument was
installed on the external windowsill on the third floor of the
Wusong MSB building (121◦290E, 31◦220N) from 30 De-
cember 2017 to 18 May 2018. The measurement site is lo-
cated in the downstream region of the Huangpu River, close
to its confluence with the Yangtze River. It is the only chan-
nel with access to the upstream region of the Huangpu River.
There are some non-container terminals near the measure-
ment site, which mainly handle goods related to domestic
trading. As a consequence, a large number of ships enter
and leave the wharf area every day, and the shipping lanes in
the downstream region of Huangpu River suffer from dense
ship traffic. By checking the synchronized photographs taken
by the camera attached to the instrument, it was found that
the types of vessels passing through were diverse, includ-
ing medium and small container ships, passenger vessels,
Figure 5. Distributions of the measured DSCDs of (a) SO2and
(b) NO2from emissions of a ship at berth from 12:04 to 12:20 on
28 August 2017, and (c) a live photo captured by the MAX-DOAS
instrument’s camera. The dashed rectangle indicates the observa-
tional view of the MAX-DOAS.
bulkers and cargo ships. In addition, the traffic volume in
the area is quite high, even as high as hundreds of ships
per hour. As shown in Fig. 1c, the viewing direction of the
MAX-DOAS instrument in the Wusong area was perpendic-
ular to the river’s shipping lane. Thus, the pollutant signals
observed mainly came from the emissions of ships navigat-
ing the shipping channel. Nevertheless, a small dock and a
station for transport containers are located opposite the river,
and may slightly influence the measurements. The elevation
angles were set in a scanning sequence of 0, 1, 2, 3, 4, 5,
6 and 8◦. The spectrum measured at 65◦was utilized as the
reference, as the zenith direction was blocked to some extent
by the MSB building.
www.atmos-chem-phys.net/19/13611/2019/ Atmos. Chem. Phys., 19, 13611–13626, 2019
13618 Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS
Figure 6. Time series of DSCDs of (a) NO2and (b) SO2measured
at a 4◦elevation angle at three azimuths on 28 August 2017.
In order to illustrate the impact of the volume of ship
traffic and the meteorological conditions, the 30 min aver-
aged wind speed data, the observed NO2and SO2DSCDs
on 2 representative days (1 January, and 9 March 2018),
and the corresponding number of passing ships are shown
in Fig. 7. It can be seen from Fig. 7a that 1 January and
9 March were selected to represent days with stabile and
unstable atmospheric conditions, respectively. On 1 Jan-
uary, the average SO2DSCDs changed from 1.8×1016 to
3.0×1016 molec cm−2, whereas the average NO2DSCDs
varied between 4.0×1016 and 1.1×1017 molec cm−2. On
9 March, the SO2and NO2average DSCDs ranged from
1.0×1016 to 2.7×1016 molec cm−2and from 2.5×1016 to
1.0×1017 molec cm−2, respectively. According to the ship
traffic density shown in Fig. 7b, the diurnal variations of the
SO2and NO2DSCDs were obviously closely related to the
flow of ships (quantitative information). Although the aver-
aged SO2and NO2DSCD levels are comparable during these
2 days, the ship traffic flow on 9 March was 50% higher over-
all than on 1 January, which may imply the important role of
the meteorological conditions. Considering the dense ship-
ping lanes, the ship-emitted pollutants are easily accumu-
lated under unfavorable conditions with lower wind speeds
(less than 2 m s−1) on 1 January. On the contrary, the ship
emissions along the lanes can be spread and more effectively
diffused when the averaged wind speed is around 5m s−1on
9 March.
In order to investigate the impacts of wind on the ob-
served DSCDs, the wind rose diagrams of NO2and SO2
DSCDs at an elevation of 5◦from January to March 2018 are
shown in Fig. 8a and b, respectively. It can be seen that the
wind mainly comes from north-northwest during the obser-
Figure 7. The 30 min averaged wind speed, ship traffic volume, ob-
served NO2and SO2DSCDs from 10:00 to 13:00 LT on 1 January
and 10:00 to 14:00 LT on 9 March at the Wusong Wharf measure-
ment site. The hollow squares in the middle of the boxes represent
the mean values, and the solid lines in the middle of the boxes rep-
resent the medians. The whiskers extend from each end of the box
to the internal and external limits. “–” represents the maximum and
minimum, and the “×” symbols are the 1 % and 99 % quantiles. The
upper and lower edges of the boxes are the 25 % and 75% quantiles,
respectively.
vation period. The average of the NO2DSCDs is low under
northerly wind conditions. When the wind direction is paral-
lel to the observation direction (i.e., easterly and westerly, as
the viewing direction of the telescope is pointing to the east),
the average of the NO2DSCDs is significantly higher. Simi-
larly, the averaged SO2DSCDs are higher under easterly and
westerly wind conditions than under southerly and northerly
conditions. This suggests that the optical length inside the
polluted air and, therefore, the response signal is probably
increased when the wind transports the polluted air parallel
to the DOAS viewing direction. In Fig. 8c and d, the per-
pendicular direction for north and south is considered to be
wind from 0◦±15◦to 180◦±15◦, and the parallel direction
for east and west is considered to be wind from 90◦±15◦
to 270◦±15◦. It can be seen that the NO2and SO2DSCDs
are quite different under these two types of wind conditions.
When the wind is parallel to the observation direction (east
and west), 34 % of NO2DSCDs and 31 % of SO2DSCDs
are greater than 3.00×1016 and 1.50 ×1016 molec cm−2, re-
spectively. However, under perpendicular direction condi-
tions (north and south), the occurrence of high DSCDs of
Atmos. Chem. Phys., 19, 13611–13626, 2019 www.atmos-chem-phys.net/19/13611/2019/
Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS 13619
Figure 8. The dependence of NO2(a, c) and SO2(b, d) DSCDs at
an elevation of 5◦on wind directions from January to March 2018.
NO2and SO2significantly decreased compared with the par-
allel direction.
Based on the real-time photographs taken by the instru-
ment, we manually counted the ship density in order to dis-
cuss its relationship to the observed DSCDs of NO2and SO2
at an elevation of 5◦, as shown in Fig. 9. It is obvious that
the hourly means of the NO2and SO2DSCDs show an up-
ward trend as the ship density increases. As the fuels used
by ships are inconsistent, and the wind speed and direction
also affect the DSCDs, it is difficult to find a clear linear re-
lationship between the hourly data of ship density and the
DSCDs in this busy inland waterway environment. From a
statistical prospective, the averaged NO2and SO2DSCDs
of the binned ship density group (the hollow squares in the
middle of the boxes in Fig. 9) show a strong positive cor-
relation with the ship density, with a correlation coefficient
(R) of 0.86 and 0.97, respectively. The relatively higher Rof
SO2suggests that the main impacts of SO2stem from ship
emission sources; however, the Rvalue of NO2suggests that
there may be a more complex NO2source nearby.
In general, it can be concluded from the several months of
continuous measurements at the Wusong MSB site that the
ship density and meteorological conditions are the two ma-
jor factors influencing the observed NO2and SO2levels in
this typical inland waterway environment. For similar diffu-
sion situations, the MAX-DOAS instrument can accurately
detect elevated pollutants concentrations with an increased
number of ships. However, due to the busy shipping lanes in
front of the instrument, the MAX-DOAS instrument usually
observes pollutant signals in plumes from multiple ships con-
Figure 9. Relationship between the DSCDs of (a) NO2and (b) SO2
at an elevation of 5◦and ship density. The hollow squares in the
middle of the boxes represent the mean values, and the solid lines
in the middle of the boxes represent the medians. Whiskers extend
from each end of the boxes to the internal and external limits. “–”
represents the maximum and minimum, and the “×” symbols are
the 1 % and 99% quantiles. The upper and lower edges of the boxes
are the 25 % and 75% quantiles, respectively.
currently, and the navigation speed of the ships is relatively
faster than the period of a completed scan sequence. There-
fore, it is very hard to distinguish a single plume from the
mixture. Another shortcoming of this measurement method
is that the MAX-DOAS measured NO2levels are consider-
ably impacted by emission sources in the surrounding area,
such as nearby main roads and highways, which make non-
negligible contributions to the amount of ambient NO2. As
it is not practical for regulatory authorities to undertake fuel
detection for each ship in this busy inland waterway environ-
ment, MAX-DOAS measurements present a more pragmatic
opportunity to surveil ship emissions. Based on the legally
permitted sulfur content and ship activity data, the theoreti-
cal NO2an SO2concentrations of a plume exhausted from
a chimney can be calculated. By combining this calculation
with the diffusion model of the plume, the theoretical con-
centration of SO2on the light path of the MAX-DOAS ob-
servations can be obtained. Following this, suspicious ships
thought to be using fuel with an excess sulfur content can be
identified.
3.3 Ocean-going ship emissions
Another shipping traffic scenario was also considered with
respect to the MAX-DOAS measurements at Yantian Port
(114◦290E, 22◦560N), which is located on the east side of
Shenzhen in the Pearl River Delta emission control zone (see
Fig. 1). Yantian Port is one of the largest container ports in
China and even in the world, and has 20 large deep-water
berths with a quay length of 8212 m and a water depth along-
side the quay of 17.4 m, which is beneficial for docking
ocean-going vessels with a length of more than 300 m. Un-
like the measurement sites discussed above, a distinct fea-
ture of shipping traffic in the Yantian Port is the huge size
of inbound and outbound vessels and the much lower traf-
www.atmos-chem-phys.net/19/13611/2019/ Atmos. Chem. Phys., 19, 13611–13626, 2019
13620 Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS
fic density. The MAX-DOAS instrument was installed on the
shore in the central operation zone of the Yantian Port from
23 May 2018 to 30 June 2018. As can be seen in Fig. 1d, the
viewing direction of the MAX-DOAS was pointed toward
the shipping lanes in the eastward sea area. Due to the lack
of other emission sources in the instrument’s field of view,
the MAX-DOAS observations could easily capture the pol-
lutants in a single plume from individual inbound and out-
bound ships (as shown in Fig. 10).
Figure 10a and b present the altitude dependence of
the observed SO2and NO2DSCDs around noontime on
26 May 2018. During the observational period, there were
three apparent peaks in the SO2and NO2DSCDs, i.e., 13:00,
13:30 and 14:10 LT. The increases of both pollutant levels
occurred simultaneously. For the first pulse around 13:00 LT,
the higher SO2DSCD levels are distributed above a 10◦ele-
vation, whereas the strong signals of NO2are concentrated
below an elevation angle of 5◦. This can be explained by
the fact that ocean-going container vessels and tugboats be-
have differently with respect to emissions and operations.
Figure 10c shows that a large container ship is outbound at
12:55 LT with the assistance of two tugboats. It is obvious
that the exhaust outlet height is very high for large container
ships, but quite low for tugboats. As tugboats are usually op-
erated within the port area, their fuel usage is always in accor-
dance with ECA regulations and is of high quality. Thus, the
stronger SO2signals that appeared at a higher altitude were
attributed to container ship emissions, whereas NO2hot spots
close to the sea surface were contributed by tugboat emis-
sions. During the period around 13:30 LT, the DSCDs of both
SO2and NO2were slightly increased and were located below
an elevation of 7◦. According to the live photo in Fig. 10d,
there was only a small container ship passing through at a
distance of about 1 km (in the front view) from the instru-
ment during this time. Considering the distance between the
ship and instrument, the height of the exhaust outlet should
be related to a lower elevation angle, where the correspond-
ing strong signals of the emitted pollutants are expected to be
observed. Additionally, obvious SO2and NO2signals were
found at around 14:10 LT, during which high SO2levels were
distributed from an elevation angle of 10 to 15◦, but strong
signals of SO2and NO2were both found near the sea sur-
face; however, no ship was captured in the live photographs.
It can be inferred from the AIS information that the signal
observed was a dispersed plume from a ship in another ship-
ping lane, and was not from the front view of the instrument.
In addition, the AIS information also confirmed that there
were no other ship emission disturbances for the two earlier
measurements.
In general, the characteristics of the observed SO2and
NO2DSCD distributions with respect to height are to some
extent related to the ship size, its distance from the instru-
ment and operational status, as well as the atmospheric sta-
bility. Based on the example discussed above, the MAX-
DOAS measurements at Yantian Port can detect pollutants
Figure 10. Measured DSCDs of (a) SO2and (b) NO2from 12:55
to 14:20 LT, and live photographs taken by the camera at (c) 12:56
and (d) 13:22 LT on 26 May 2018.
Figure 11. A typical distribution of SO2DSCDs in the smoke
plume of a ship on 22 June 2018.
in a single plume from an individual ship and can provide
information regarding the vertical distribution of the pollu-
tants under low ship traffic volume conditions. Considering
the large discrepancies of SO2signals with altitude, we try to
analyze the plumes detected in more detail and obtain a rep-
resentative observation elevation. According to the live pho-
tographs, a large container ship entered the field of view at
09:51 LT on 22 June 2018 and moved very slowly, emitting a
distinct black smoke plume. Figure 11 shows the distribution
of the SO2DSCDs in plumes at different elevation angles.
The SO2DSCDs peaked at 8.17×1016 molec cm−2between
an elevation angle of 5 and 7◦, and decreased with height.
It was found that the DSCDs observed at an elevation angle
of 7◦are suitable to represent the peak concentrations in the
plumes considering the chimney height of ship and its hori-
zontal distance from the MAX-DOAS instrument.
Atmos. Chem. Phys., 19, 13611–13626, 2019 www.atmos-chem-phys.net/19/13611/2019/
Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS 13621
Figure 12. Diurnal variations of (a) NO2and (b) SO2DSCDs mea-
sured at a 7◦elevation angle on 26 June 2018.
Rather than scanning the full range of elevations, it is pos-
sible to individually resolve the plume signal of passing ships
using high temporal resolution measurements (60 s) at a sin-
gle (7◦) elevation. Thus, the diurnal profiles of the SO2and
NO2DSCDs at a 7◦elevation for 26 June 2018 were further
investigated, and are presented in Fig. 12. The multiple peaks
of SO2and NO2, with the highest DSCDs of SO2and NO2
exceeding 6.00×1016 molec cm−2, occurred due to the emis-
sions of the occasional passing ship. By applying a mathe-
matical method, a baseline (the blue dotted line in Fig. 12)
can be extracted from the DSCD trend lines (the black solid
line in Fig. 12). The baseline represents the diurnal variations
in the DSCDs, mostly due to the change in the light path
caused by the solar zenith angle and the background emis-
sions. Finally, it can be seen that seven synchronous peaks of
SO2and NO2levels higher than 2.00 ×1016 molec cm−2are
present in the trend line (the red solid line in Fig. 12). Val-
idated by the live photographs from the instrument and the
AIS information, these sharp pollutant concentration peaks
originated from the ship plumes of passing ships. This em-
phasizes the high sensitivity of MAX-DOAS measurements
to the change in SO2and NO2levels in the atmosphere. The
increases in the pollutant levels lasted from 10min to 30 min,
which is related to the duration of the ship movement in the
instrument’s field of view.
Moreover, it should be noted that the amplitude of each
peak varied differently, which implies that the DSCDs’
SO2/NO2ratio for each peak may reveal emission infor-
mation regarding the fuel sulfur content of individual ves-
sels (Seyler et al., 2017; Mellqvist et al., 2017; Van Roy
and Scheldeman, 2016). However, it is important to note
that NO2is formed by the reaction of NO and O3in the
plume; thus, the SO2/NO2ratio depends to a certain extent
on the age of the plume. The ambient O3between 08:00 and
17:00 LT averaged at 63.7ppb in Yantian during the cam-
paign. Considering the abundance of ozone, the NO emitted
by the ship would have rapidly (within a few minutes or even
faster) reacted with O3to form NO2(Seyler et al., 2017).
In addition, the conversion between NO and NO2is very
fast and maintains a dynamic balance with sunlight during
the daytime considering the photolysis of NO2(Singh et al.,
1987). Therefore, the SO2/NO2ratio in an observed plume
would be less impacted by the freshly emitted NO. Thus, a
linear regression analysis between the SO2and NO2DSCDs
was performed to infer the fuel sulfur content.
Figure 13 presents the analysis results for 24 different
vessels. The strong correlation between the SO2and NO2
DSCDs is obvious evidence of the significant homologies of
emission sources between SO2and NO2. Nevertheless, the
slope of different vessels varied greatly from 0.28 to 2.90,
indicating the diversity of the SO2emission intensity in the
ship plumes. In general, SO2emissions are directly related
to the fuel sulfur content and engine operation status of the
ships, according to the emission model estimation, e.g., the
power, activity time and the speed of ship (Fan et al., 2016;
Zhang et al., 2019). Outbound vessels usually leave the shore
slowly with the help of tugboats, and then speed up when
sailing into the sea. During the latter process, the main engine
is utilized to power navigation, and the fuel used by the main
engine has a higher sulfur content than that utilized by the
auxiliary engine. In contrast, the main engine of a vessel is
usually shutdown during the inbound process. Therefore, the
ratio of SO2/NO2in the DSCDs in plumes emitted by out-
bound vessels could be higher than that those in the plumes
of inbound ships.
During the MAX-DOAS observations, we also carried out
some fuel sample analyses in addition to the investigation of
the activity data and engine parameters of vessels, and five
of the vessels in question are shown in Fig. 12. We also indi-
cate the different status of nine individual vessels in Fig. 14,
along with information regarding their fuel sulfur content
and the rated power of their engines (“inbound” and “out-
bound” in this figure refer to the rated power of the main
and auxiliary engines, respectively). Vessel II is a tugboat
that was operating in the port area; thus, it used fuel with
the lowest fuel sulfur content of 0.001 % and showed a low
SO2/NO2ratio in the DSCDs. Furthermore, the inbound ves-
sels I, VI and VII (indicated by diamonds in Fig. 14) had
switched off their main engines when they entered the MAX-
DOAS instrument’s field of view, and were moved by tug-
boats before finally docking by inertia. As previously stated,
the sulfur content of fuels used to power auxiliary engines
are much lower than those utilized to power main engines;
thus, SO2/NO2ratios of inbound vessels are much lower
than those of outbound vessels. The other vessels, indicated
www.atmos-chem-phys.net/19/13611/2019/ Atmos. Chem. Phys., 19, 13611–13626, 2019
13622 Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS
Figure 13. The relationship between SO2and NO2emitted by several typical vessels.”O” indicates outbound vessels, ”I” indicates inbound
vessels and ”T” indicates tugboats.
by circles in Fig. 14, are all in outbound ships. As these
outbound vessels launched their main engine, and, thus, uti-
lized high sulfur fuels, the vessels exhibited relatively higher
SO2/NO2ratios (over 2.0), except for vessel IV. Due to the
use of much cleaner fuel (with a sulfur content of 1.28 %),
vessel IV presented the lowest SO2/NO2ratio among all of
the outbound vessels. Compared with vessel III, which had a
similar engine power rating but used fuel with a higher sul-
fur content, it can be observed that the SO2/NO2ratio in the
plume increased with the increase in the fuel sulfur content
used by the vessels (Fig. 14). This phenomenon is also no-
table with respect to vessels V and VIII. It is worth noting
that outbound cargo vessel IX deviates from the results seen
for the other vessels, as it has very low rated power but a
very high SO2/NO2ratio ( > 2.0). Therefore, vessel IX can
be flagged as a suspicious ship that is probably using fuel
with a sulfur content exceeding the regulation limit.
Basically, the SO2/NO2ratios in the plumes discharged
from inbound vessels and tugboats are usually lower than
1.5 under normal conditions, which are much smaller values
than those of outbound vessels using high rated power en-
gines and high sulfur content fuels. For outbound vessels, the
SO2/NO2ratios are more related to the fuel sulfur content.
Figure 14. The relationship between the SO2/NO2ratio and the
fuel sulfur content and engine rated power of all nine vessels, ob-
tained by linear regression. Tugboats, and inbound and outbound
vessels are represented by a star, diamonds and circles, respectively.
Atmos. Chem. Phys., 19, 13611–13626, 2019 www.atmos-chem-phys.net/19/13611/2019/
Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS 13623
An irregular observed SO2/NO2ratio can flag a vessel as
possibly not being in conformance with the enforced sulfur
content limitation. Therefore, the MAX-DOAS measurement
provides promising technology for the compliance monitor-
ing of fuel sulfur content by investigating the SO2/NO2ratio
in ship plumes, in addition to more accurate estimation of
ship emissions during operation due to the inclusion of the
load and emission factors. During the course of this study,
the statistical analysis of SO2/NO2ratios in the plumes of
55 ships were performed. The frequency distribution of the
slope of the SO2/NO2ratio is shown in Fig. 15. It can be seen
that the SO2/NO2ratios were mostly less than 1.5 (72.7 % of
observations). Ships with SO2/NO2ratios between 0.6 and
0.9 comprised the highest proportion of observations. This
indicates that most of the fuels used by ships in Yantian Port
could be qualified. However, there are still some ships that
may be using noncompliant fuels, as 27 % of the ships ob-
served were found to have a SO2/NO2ratio greater than 1.5.
4 Conclusions
In this study, we performed MAX-DOAS measurements to
observe ship emissions of SO2and NO2in Shanghai and
Shenzhen, China, under three different typical ship traffic
conditions. At Waigaoqiao container terminal in Shanghai,
the SO2and NO2exhausted by ships at berth could be easily
identified using 2-D MAX-DOAS observations with respect
to the locations and intensities of the emissions. In the in-
land waterway area at Wusong Wharf it was difficult to deter-
mine individual ship emissions due to the dense traffic vol-
ume and complex background environment. The long-term
MAX-DOAS measurements showed that the changes in SO2
and NO2were correlated with the ship traffic density under
stable and unstable atmospheric conditions. However, better
dispersion under unstable atmospheric condition was favor-
able for the decrease of pollutant levels. For open-sea waters
in the Yantian deep-water port, the DSCDs of SO2and NO2
measured by MAX-DOAS were highly sensitive to the emit-
ted plumes of vessels passing through the shore-based instru-
ment’s field of view, which showed a significant increase in
the pollutant concentrations as well as a 10–30 min duration
of the emission signals. Considering the distance and the size
of the vessels, the DSCDs observed at an elevation angle of
7◦are hot spots of the concentration in altitude; thus, these
values were further selected to investigate the fuel sulfur con-
tent. According to the linear regression of the SO2and NO2
DSCDs, the SO2/NO2ratios are found to be very helpful to
infer the levels of sulfur emission. Combined with fuel sam-
ple analysis and vessel data, the SO2/NO2ratio in plumes
is usually lower than 1.5 for inbound vessels and tugboats,
and is much smaller than that of other vessels. The abnor-
mally high SO2/NO2ratio in a plume usually implies that a
vessel is not in compliance with the enforced sulfur content
limitation.
Figure 15. Frequency distribution of the slope of SO2/NO2from
samples of 55 vessels.
In summary, optical remote sensing using the MAX-
DOAS technique is highly beneficial for measurements of
ship-emitted NO2and SO2. These applications under dif-
ferent ship traffic conditions demonstrated the feasibility of
shore-based MAX-DOAS to observe SO2and NO2emitted
from vessels docked at berth, vessels navigation in riverine
shipping lanes and inbound and outbound operations. Nev-
ertheless, the main ship-emitted pollutants – NO and CO2
– cannot be monitored due to the limitation of the observed
wavelength range. As MAX-DOAS uses solar scattered light
as a source, it cannot be utilized at night when there is no sun-
light, and there is also large error for observations carried out
during twilight and under rainy conditions. In the future, the
combination of MAX-DOAS remote sensing of ship plumes
and the estimation of emissions using theoretical fuel sulfur
contents and actual operation data will provide a promising
approach for ship emission surveillance in the future.
Data availability. Data are available for scientific purposes upon
request from the corresponding authors.
Author contributions. YC, SW and BZ designed and implemented
the research, and prepared the paper. JZ, YG and RZ contributed
to the MAX-DOAS measurements at different sites. YC and SW
carried out the MAX-DOAS retrieval and the combined analysis
involving other auxiliary data. YL, YZ, YQ and WM provided con-
structive comments and support for the ship emissions research por-
tion of this study.
Competing interests. The authors declare that they have no conflict
of interest.
www.atmos-chem-phys.net/19/13611/2019/ Atmos. Chem. Phys., 19, 13611–13626, 2019
13624 Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS
Special issue statement. This article is part of the special issue
“Shipping and the Environment – From Regional to Global Perspec-
tives (ACP/OS inter-journal SI)”. It is not associated with a confer-
ence.
Acknowledgements. This research was supported by the Na-
tional Key Research and Development Program of China (grant
nos 2016YFC0200401 and 2017YFC0210002), the National Natu-
ral Science Foundation of China (grant nos. 41775113, 21777026
and 21677038), the Shanghai Pujiang Talent Program (grant
no. 17PJC015) and the Pudong Science and Technology commit-
tee of Shanghai (grant no. PKJ2018-C05). We would like to thank
the Shenzhen Maritime Safety Administration and the Wusong and
Pudong Maritime Safety Bureau of Shanghai for the coordination
of field measurements.
Financial support. This research has been supported by the Na-
tional Key Research and Development Program of China (grant
nos. 2016YFC0200401 and 2017YFC0210002), the National Natu-
ral Science Foundation of China (grant nos. 41775113, 21777026,
and 21677038), the Shanghai Pujiang Talent Program (grant no.
17PJC015) and the Pudong Science and Technology committee of
Shanghai (grant no. PKJ2018-C05).
Review statement. This paper was edited by Markus Quante and
reviewed by Andreas Weigelt and one anonymous referee.
References
Balzani Lööv, J. M., Alfoldy, B., Gast, L. F. L., Hjorth, J., Lagler,
F., Mellqvist, J., Beecken, J., Berg, N., Duyzer, J., Westrate, H.,
Swart, D. P. J., Berkhout, A. J. C., Jalkanen, J.-P., Prata, A. J., van
der Hoff, G. R., and Borowiak, A.: Field test of available methods
to measure remotely SOxand NOxemissions from ships, Atmos.
Meas. Tech., 7, 2597–2613, https://doi.org/10.5194/amt-7-2597-
2014, 2014.
Becagli, S., Sferlazzo, D. M., Pace, G., di Sarra, A., Bommarito,
C., Calzolai, G., Ghedini, C., Lucarelli, F., Meloni, D., Mon-
teleone, F., Severi, M., Traversi, R., and Udisti, R.: Evidence
for heavy fuel oil combustion aerosols from chemical analyses
at the island of Lampedusa: a possible large role of ships emis-
sions in the Mediterranean, Atmos. Chem. Phys., 12, 3479–3492,
https://doi.org/10.5194/acp-12-3479-2012, 2012.
Beecken, J., Mellqvist, J., Salo, K., Ekholm, J., Jalkanen, J.-P., Jo-
hansson, L., Litvinenko, V., Volodin, K., and Frank-Kamenetsky,
D. A.: Emission factors of SO2, NOxand particles from ships
in Neva Bay from ground-based and helicopter-borne measure-
ments and AIS-based modeling, Atmos. Chem. Phys., 15, 5229–
5241, https://doi.org/10.5194/acp-15-5229-2015, 2015.
Berg, N., Mellqvist, J., Jalkanen, J.-P., and Balzani, J.: Ship
emissions of SO2and NO2: DOAS measurements from
airborne platforms, Atmos. Meas. Tech., 5, 1085–1098,
https://doi.org/10.5194/amt-5-1085-2012, 2012.
Berglen, T. F., Bernsten, T. K., Isaksen, I. S. A., and Sundet, J. K.:
A global model of the coupled sulfur/oxidant chemistry in the
troposphere: the sulfur cycle, J. Geophys. Res., 109, D19310,
https://doi.org/10.1029/2003JD003948, 2004.
Bogumil, K., Orphal, J., Homann, T., Voigt, S., Spietz, P., Fleis-
chmann, O. C., Vogel, A., Hartmann, M., Bovensmann, H.,
Frerik, J., and Burrows, J. P.: Measurements of Molecular
Absorption Spectra with the SCIAMACHY Pre-Flight Model:
Instrument Characterization and Reference Data for Atmo-
spheric Remote-Sensing in the 230–2380 nm Region, J. Photoch.
Photobio. A., 157, 167–184, https://doi.org/10.1016/S1010-
6030(03)00062-5, 2003.
Chance, K. and Kurucz, R.: An improved high-resolution solar ref-
erence spectrum for earth’s atmosphere measurements in the ul-
traviolet, visible, and near infrared, J. Quant. Spectrosc. Ra., 111,
1289–1295, https://doi.org/10.1016/j.jqsrt.2010.01.036, 2010.
Coggon, M. M., Sorooshian, A., Wang, Z., Metcalf, A. R., Frossard,
A. A., Lin, J. J., Craven, J. S., Nenes, A., Jonsson, H. H., Rus-
sell, L. M., Flagan, R. C., and Seinfeld, J. H.: Ship impacts on
the marine atmosphere: insights into the contribution of shipping
emissions to the properties of marine aerosol and clouds, At-
mos. Chem. Phys., 12, 8439–8458, https://doi.org/10.5194/acp-
12-8439-2012, 2012.
Corbett, J. J., Fischbeck, P. S., and Pandis, S. N.: Global nitrogen
and sulfur inventories for oceangoing ships, J. Geophys. Res.,
104, 3457–3470, https://doi.org/10.1029/1998JD100040, 1999.
Diesch, J.-M., Drewnick, F., Klimach, T., and Borrmann, S.: In-
vestigation of gaseous and particulate emissions from vari-
ous marine vessel types measured on the banks of the Elbe
in Northern Germany, Atmos. Chem. Phys., 13, 3603–3618,
https://doi.org/10.5194/acp-13-3603-2013, 2013.
Dimitriades, B.: Effects of hydrocarbon and nitrogen oxides on
photochemical smog formation, Environ. Sci. Tech, 6, 253–260,
1972.
Edner, H., Ragnarson, P., Spännare, S., and Svanberg, S.: Differ-
ential optical absorption spectroscopy (DOAS) system for ur-
ban atmospheric pollution monitoring, Appl. Opt., 32, 327–333,
https://doi.org/10.1364/AO.32.000327, 1993.
Endresen, Ø., Sørgård, E., Sundet, J. K., Dalsøren, S. B., Isaksen,
I. S. A., Berglen, T. F., and Gravir, G.: Emissions from Interna-
tional Sea Transportation and Environmental Impact, J. Geophys.
Res.-Atmos., 108, 4560, https://doi.org/10.1029/2002JD002898,
2003.
Eyring, V., Köhler, H. W., van Aardenne, J., and
Lauer, A.: Emissions from international shipping: 1.
The last 50 years, J. Geophys. Res., 110, D17305,
https://doi.org/10.1029/2004JD005619, 2005.
Eyring, V., Isaksen, I. S., Berntsen, T., Collins, W. J., Cor-
bett, J. J., Endresen, O., Grainger, R. G., Moldanova, J.,
Schlager, H., and Stevenson, D. S.: Transport impacts on atmo-
sphere and climate: Shipping, Atmos. Environ., 44, 4735–4771,
https://doi.org/10.1016/j.atmosenv.2009.04.059, 2010.
Fan, Q., Zhang, Y., Ma, W., Ma, H., Feng, J., Yu, Q., Yang, X., Ng,
S. K. W., Fu, Q., and Chen, L.: Spatial and seasonal dynamics of
ship emissions over the Yangtze River Delta and East China Sea
and their potential environmental Influence, Environ. Sci. Tech-
nol., 50, 1322–1329, https://doi.org/10.1021/acs.est.5b03965,
2016
Fleischmann, O. C., Hartmann, M., Burrows, J. P., and Orphal,
J.: New ultraviolet absorption cross-sections of BrO at at-
mospheric temperatures measured by time-windowing Fourier
Atmos. Chem. Phys., 19, 13611–13626, 2019 www.atmos-chem-phys.net/19/13611/2019/
Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS 13625
transform spectroscopy, J. Photoch. Photobio. A, 168, 117–132,
https://doi.org/10.1016/j.jphotochem.2004.03.026, 2004.
General, S., Pöhler, D., Sihler, H., Bobrowski, N., Frieß, U., Ziel-
cke, J., Horbanski, M., Shepson, P. B., Stirm, B. H., Simp-
son, W. R., Weber, K., Fischer, C., and Platt, U.: The Hei-
delberg Airborne Imaging DOAS Instrument (HAIDI) – a
novel imaging DOAS device for 2-D and 3-D imaging of
trace gases and aerosols, Atmos. Meas. Tech., 7, 3459–3485,
https://doi.org/10.5194/amt-7-3459-2014, 2014.
Hong, Q., Liu, C., Chan, K. L., Hu, Q., Xie, Z., Liu, H., Si, F., and
Liu, J.: Ship-based MAX-DOAS measurements of tropospheric
NO2, SO2, and HCHO distribution along the Yangtze River, At-
mos. Chem. Phys., 18, 5931–5951, https://doi.org/10.5194/acp-
18-5931-2018, 2018.
Hönninger, G., von Friedeburg, C., and Platt, U.: Multi axis dif-
ferential optical absorption spectroscopy (MAX-DOAS), At-
mos. Chem. Phys., 4, 231–254, https://doi.org/10.5194/acp-4-
231-2004, 2004.
International Maritime Organization (IMO): Second GHG study
2009: Prevention of Air Pollution from Ships, IMO, London,
2009.
Johansson, L., Jalkanen, J. P., and Kukkonen, J.: Global as-
sessment of shipping emissions in 2015 on a high spa-
tial and temporal resolution, Atmos. Environ., 167, 403–415,
https://doi.org/10.1016/j.atmosenv.2017.08.042, 2017.
Kattner, L., Mathieu-Üffing, B., Burrows, J. P., Richter, A.,
Schmolke, S., Seyler, A., and Wittrock, F.: Monitoring com-
pliance with sulfur content regulations of shipping fuel by in
situ measurements of ship emissions, Atmos. Chem. Phys.,
15, 10087–10092, https://doi.org/10.5194/acp-15-10087-2015,
2015.
Kurtenbach, R., Vaupel, K., Kleffmann, J., Klenk, U., Schmidt,
E., and Wiesen, P.: Emissions of NO, NO2and PM from
inland shipping, Atmos. Chem. Phys., 16, 14285–14295,
https://doi.org/10.5194/acp-16-14285-2016, 2016.
Lai, H. K., Tsang, H., Chau, J., Lee, C. H., McGhee, S. M., Hed-
ley, A. J., and Wong, C. M.: Health impact assessment of ma-
rine emissions in Pearl River Delta region, Marine Pollut. Bull.,
66, 158–163, https://doi.org/10.1016/j.marpolbul.2012.09.029,
2013.
Lauer, A., Eyring, V., Hendricks, J., Jöckel, P., and Lohmann, U.:
Global model simulations of the impact of ocean-going ships on
aerosols, clouds, and the radiation budget, Atmos. Chem. Phys.,
7, 5061–5079, https://doi.org/10.5194/acp-7-5061-2007, 2007.
Liu, H., Fu, M., Jin, X., Shang, Y., Shindell, D., Faluvegi, G., Shin-
dell, C., and He, K.: Health and climate impacts of ocean-going
vessels in East Asia, Nat. Clim. Change., 6, 1037–1041, 2016.
Lv, Z., Liu, H., Ying, Q., Fu, M., Meng, Z., Wang, Y., Wei, W.,
Gong, H., and He, K.: Impacts of shipping emissions on PM2.5
pollution in China, Atmos. Chem. Phys., 18, 15811–15824,
https://doi.org/10.5194/acp-18-15811-2018, 2018.
Ma, J. Z., Beirle, S., Jin, J. L., Shaiganfar, R., Yan, P., and Wag-
ner, T.: Tropospheric NO2vertical column densities over Bei-
jing: results of the first three years of ground-based MAX-
DOAS measurements (2008–2011) and satellite validation, At-
mos. Chem. Phys., 13, 1547–1567, https://doi.org/10.5194/acp-
13-1547-2013, 2013.
Matthias, V., Bewersdorff, I., Aulinger, A., and Quante, M.:
The contribution of ship emissions to air pollution in
the North Sea regions, Environ. Pollut., 158, 2241–2250,
https://doi.org/10.1016/j.envpol.2010.02.013, 2010.
McLaren, R., Wojtal, P., Halla, J. D., Mihele, C., and Brook, J. R.: A
survey of NO2: SO2emission ratios measured in marine vessel
plumes in the Strait of Georgia, Atmos. Environ., 46, 655–658,
https://doi.org/10.1016/j.atmosenv.2011.10.044, 2012.
Meller, R. and Moortgat, G. K.: Temperature dependence of the ab-
sorption cross sections of formaldehyde between 223 and 323 K
in the wavelength range 225–375nm, J. Geophys. Res.-Atmos.,
105, 7089–7101, https://doi.org/10.1029/1999JD901074, 2000.
Mellqvist, J. and Rosén, A.: DOAS for flue gas monitoring – II, De-
viations from the Beer-Lambert law for the UV/visible absorp-
tion spectra of NO, NO2, SO2and NH3, J. Quant. Spectrosc.
Ra., 56, 209–224, https://doi.org/10.1016/0022-4073(96)00043-
X, 1996.
Mellqvist, J., Beecken, J., Conde, V., and Ekholm, J.: Surveil-
lance of Sulfur Emissions from Ships in Danish Waters.
Report to the Danish Environmental Protection Agency,
https://doi.org/10.17196/DEPA.001, 2017.
MOT: Implementation of the Ship Emission Control Area in Pearl
River Delta, the Yangtze River Delta and the Bohai Rim (Beijing-
Tianjin-Hebei area), Ministry of Transport, China, 8, 2015.
Murphy, S. M., Agrawal, H., Sorooshian, A., Padro, L. T.,
Gates, H., Hersey, S., Welch, W. A., Jung, H., Miller, J. W.,
Cocker, D. R., Nenes, A., Jonsson, H. H., Flagan, R. C.,
and Seinfeld, J. H.: Comprehensive simultaneous shipboard
and airborne characterisation of exhaust from a modern con-
tainer ship at sea, Environ. Sci. Technol., 43, 4626–4640,
https://doi.org/10.1021/es802413j, 2009.
Ning, X., Selesnick, I., and Duval, L.: Chromatogram
baseline estimation and denoising using sparsity
(BEADS), Chemom. Intell. Lab. Syst., 139, 156–167,
https://doi.org/10.1016/j.chemolab.2014.09.014, 2014.
Pikelnaya, O., Flynn, J. H., Tsai, C., and Stutz, J.: Imaging DOAS
detection of primary formaldehyde and sulfur dioxide emissions
from petrochemical flares, J. Geophys. Res.-Atmos., 118, 8716–
8728, https://doi.org/10.1002/jgrd.50643, 2013.
Pillot, D., Guiot, D., Le Cottier, B., Perret, P., and Tassel,P.: Exhaust
emissions from in-service inland waterways vessels, J. Earth Sci.
Geotech. Eng., 6, 205–225, 2016.
Platt, U., and Stutz, J.: Differential Optical Absorption Spec-
troscopy, Springer, Berlin-Heidelberg, 2008.
Platt, U., Perner, D., and Patz, H. W.: Simultaneous Mea-
surement of Atmospheric CH2O, O3and NO2by Differ-
ential Optical Absorption, J. Geophys. Res., 84, 6329–6335,
https://doi.org/10.1029/JC084iC10p06329, 1979.
Prata, A. J.: Measuring SO2ship emissions with an ultravi-
olet imaging camera, Atmos. Meas. Tech., 7, 1213–1229,
https://doi.org/10.5194/amt-7-1213-2014, 2014.
Premuda, M., Masieri, S., Bortoli, D., Kostadinov, I., Petri-
toli, A., and Giovanelli, G.: Evaluation of vessel emis-
sions in a lagoon area with ground based Multi axis
DOAS measurements, Atmos. Environ., 45, 5212–5219,
https://doi.org/10.1016/j.atmosenv.2011.05.067, 2011.
Schreier, S. F., Peters, E., Richter, A. Lampel, J., Wittrock,
F., and Burrowsa, J. P.: Ship-based MAX-DOAS mea-
surements of tropospheric NO2and SO2in the South
China and Sulu Sea, Atmos. Environ., 102, 331–343,
https://doi.org/10.1016/j.atmosenv.2014.12.015, 2015.
www.atmos-chem-phys.net/19/13611/2019/ Atmos. Chem. Phys., 19, 13611–13626, 2019
13626 Y. Cheng et al.: Surveillance of SO2and NO2from ship emissions by MAX-DOAS
Seinfeld, J. H. and Pandis, S. N.: Atmospheric chemistry and
physics: From air pollution to climate change, 2nd edn., John
Wiley and Sons, Hoboken, NJ, 2006.
Serdyuchenko, A., Gorshelev, V., Weber, M., Chehade, W., and
Burrows, J. P.: High spectral resolution ozone absorption cross-
sections – Part 2: Temperature dependence, Atmos. Meas. Tech.,
7, 625–636, https://doi.org/10.5194/amt-7-625-2014, 2014.
Seyler, A., Wittrock, F., Kattner, L., Mathieu-Üffing, B., Pe-
ters, E., Richter, A., Schmolke, S., and Burrows, J. P.: Mon-
itoring shipping emissions in the German Bight using MAX-
DOAS measurements, Atmos. Chem. Phys., 17, 10997–11023,
https://doi.org/10.5194/acp-17-10997-2017, 2017.
Singh, H. B.: Reactive nitrogen in the troposphere, Environ. Sci.
Technol., 21, 320–327, https://doi.org/10.1021/es00158a001,
1987.
Sinreich, R., Frieß, U., Wagner, T., and Platt, U.: Multi axis
differential optical absorption spectroscopy (MAX-DOAS) of
gas and aerosol distributions, Faraday Discuss., 130, 153–164,
https://doi.org/10.1039/b419274p, 2005.
Takashima, H., Irie, H., Kanaya, Y., and Syamsudin, F.: NO2ob-
servations over the western Pacific and Indian Ocean by MAX-
DOAS on Kaiyo, a Japanese research vessel, Atmos. Meas.
Tech., 5, 2351–2360, https://doi.org/10.5194/amt-5-2351-2012,
2012.
Tan, W., Liu, C., Wang, S., Xing, C., Su, W., Zhang, C., Xia, C.,
Liu, H., Cai, Z., and Liu, J.: Tropospheric NO2, SO2, and HCHO
over the East China Sea, using ship-based MAX-DOAS observa-
tions and comparison with OMI and OMPS satellite data, Atmos.
Chem. Phys., 18, 15387–15402, https://doi.org/10.5194/acp-18-
15387-2018, 2018.
Thalman, R. and Volkamer, R.: Temperature dependent absorption
cross-sections of O2-O2collision pairs between 340 and 630 nm
and at atmospherically relevant pressure., Phys. Chem. Chem.
Phys., 15, 15371–15381, https://doi.org/10.1039/C3CP50968K,
2013.
Van Roy, W. and Scheldeman, K.: Best Practices Airborne
MARPOL Annex VI Monitoring, Royal Belgian Institute of
Natural Sciences, OD Nature, Scientific service MUMM (Man-
agement Unit of the Mathematical Model of the North Sea),
Brussels, Belgium, https://www.trafi.fi/filebank/a/1482762219/
d80cdd7de80e58885ce5a4dd0af86c02/23541-Best_Practices_
Airborne_MARPOL_Annex_VI_Monitoring.pdf (last access:
1 November 2019), 2016.
Vandaele, A. C., Hermans, C., Simon, P. C., Carleer, M.,
Colin, R., Fally, S., Merienne, M.-F., Jenouvrier, A., and
Coquart, B.: Measurements of the NO2absorption cross-
section from 42 000 cm−1to 10 000 cm−1(238–1000 nm) at
220 K and 294 K, J. Quant. Spectrosc. Ra., 59, 171–184,
https://doi.org/10.1016/S0022-4073(97)00168-4, 1998.
Villa, T. F., Salimi, F., Moryon, K., Morawska, L., and Gomza-
lez, F,: Development and balidation of a UAV based sys-
tem for air pollution measurements, Sensors, 16, 2202,
https://doi.org/10.3390/s16122202, 2016.
Wagner, T., Ibrahim, O., Shaiganfar, R., and Platt, U.: Mobile
MAX-DOAS observations of tropospheric trace gases, Atmos.
Meas. Tech., 3, 129–140, https://doi.org/10.5194/amt-3-129-
2010, 2010.
Wang, T., Hendrick, F., Wang, P., Tang, G., Clémer, K., Yu, H.,
Fayt, C., Hermans, C., Gielen, C., Müller, J.-F., Pinardi, G.,
Theys, N., Brenot, H., and Van Roozendael, M.: Evaluation of
tropospheric SO2retrieved from MAX-DOAS measurements
in Xianghe, China, Atmos. Chem. Phys., 14, 11149–11164,
https://doi.org/10.5194/acp-14-11149-2014, 2014.
Yang, D., Kwan, S., Lu, T., Fu, Q., Cheng, J., Streets, D. G.,
Wu, Y., and Li, J.: An emission inventory of marine vessels
in shanghai in 2003, Environ. Sci. Technol., 41, 5183–5190,
https://doi.org/10.1021/es061979c, 2007.
Zhang, J., Wang, S., Guo, Y., Zhang, R., Qin, X., Huang,
K., Wang, D., Fu, Q., Wang, J., and Zhou, B.: Aerosol
vertical profile retrieved from ground-based MAX-DOAS
observation and characteristic distribution during winter-
time in Shanghai, China, Atmos. Environ., 192, 193–205,
https://doi.org/10.1016/j.atmosenv.2018.08.051, 2018.
Zhang, Y., Gu, J., Wang, W., Peng, Y., Wu, X., and Feng, X.: In-
land port vessel emissions inventory based on Ship Traffic Emis-
sion Assessment Model–Automatic Identification System, Adv.
Mech. Eng., 9, 1–9, https://doi.org/10.1177/1687814017712878,
2017.
Zhang, Y., Deng, F., Man, H., Fu, M., Lv, Z., Xiao, Q., Jin, X., Liu,
S., He, K., and Liu, H.: Compliance and port air quality features
with respect to ship fuel switching regulation: a field observation
campaign, SEISO-Bohai, Atmos. Chem. Phys., 19, 4899–4916,
https://doi.org/10.5194/acp-19-4899-2019, 2019.
Zhao, M., Zhang, Y., Ma, W., Fu, Q., Yang, X., Li, C., Zhou, B., Yu,
Q., and Chen, L.: Characteristics and ship traffic source identifi-
cation of air pollutants in China’s largest port, Atmos. Environ.,
64, 277–286, https://doi.org/10.1016/j.atmosenv.2012.10.007,
2013.
Atmos. Chem. Phys., 19, 13611–13626, 2019 www.atmos-chem-phys.net/19/13611/2019/
Available via license: CC BY 4.0
Content may be subject to copyright.
