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Influence of ship emissions on urban air quality: a comprehensive study using highly time-resolved online measurements and numerical simulation in Shanghai Zhanmin Liu, Xiaohui Lu, Junlan Feng, Qianzhu Fan, Yan Zhang, and Xin Yang Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b03834 • Publication Date (Web): 09 Dec 2016 Downloaded from http://pubs.acs.org on December 12, 2016
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Environmental Science & Technology
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Influence of ship emissions on urban air quality: a comprehensive study using
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highly time-resolved online measurements and numerical simulation in Shanghai
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Zhanmin Liu, Xiaohui Lu, Junlan Feng, Qianzhu Fan, Yan Zhang*, Xin Yang*
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Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention,
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Department of Environmental Science and Engineering, Fudan University, Shanghai
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200433, China
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( *Corresponding to: Handan 220, Yangpu District, Shanghai, China, 200433; Yan
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Zhang(
[email protected]); Xin Yang (
[email protected]) )
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Key words: Shanghai, vanadium-containing particles, ship emission, ATOFMS,
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numerical simulation
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Abstract: Shanghai has become an international shipping center in the world. In this
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study, the multi-year measurements and the high resolution air quality model with
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hourly ship emission inventory were combined to determine the influence of ship
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emissions on urban Shanghai. The aerosol time-of-flight mass spectrometer
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(ATOFMS) measurements were carried at an urban site from March 2009 to
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January 2013. During the entire sampling time, most of the hourly-averaged
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number fractions of primary ship emitted particles varied between 1.0 - 10.0%.
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However, the number fraction could reach up to 50% during the ship plume cases.
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Ship-plume-influenced periods usually occurred in spring and summer. The
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simulation of Weather Research and Forecasting/Community Multi-scale Air
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Quality model (WRF/CMAQ) with hourly ship emission inventory provided the
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highly time-resolved concentrations of ship-related air pollutants during a ship
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plume case. It showed ships could contribute 20 - 30% (2 - 7 µg/m3) of the total
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PM2.5 within tens of kilometers of coastal and riverside Shanghai during
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ship-plume-influenced periods. Our results showed that ship emissions have
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substantial contribution to the air pollution in urban Shanghai. The control 1
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measures of ship emission should be taken considering its negative environment
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and human health effects.
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Table of Contents (TOC)
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1 Introduction
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Ship emissions from the burning of heavy fuel oil contribute numerous gaseous and
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particulate matters into the atmosphere. The negative impacts on human health and
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the climate make ship emission a growing concern.1-4 In the past decade, the ship
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emission particles have been investigated by using laboratory engine experiments,
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on-board studies and aircraft measurements for plume tracking.5-10 Recently, more
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land-based measurements in the stationary sites affected by ship plumes have been
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reported.11-15 Mobile laboratories were usually deployed in the harbor or emission
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control area near the river to study the ship emission particles via extractive sampling
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of the passing ship emission plumes.12,13
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Land-based measurement in the urban area, when coupling with meteorological and
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ship traffic information, can be applied for statistical analysis to identify the
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contribution of ship emissions to the urban air pollutants. The direct contribution of
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ships traffic to PM2.5 and to PM10 in the urban area of Venice was found to be from 1%
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to 8%.14 Since heavy oil was combusted in the ship engines, vanadium (V), nickel (Ni)
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and iron (Fe) could be applied as reliable tracers for the ship emission particles.16-20
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Chemical composition analysis has also been the effective tool to determine the ship
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emission particles when land-based measurement was performed in a multi-source
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pollution area.15,21-23 The V/Ni ratio obtained in the off-line filter sampling analysis
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was usually applied for source apportionment in the areas with both ship emission and
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heavy oil combustion industry.21-23 In addition, non-sea salt sulfate is regarded as a
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marker for the secondary contribution of ship emission because ship-emitted gaseous
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pollutants (e.g. SO2) will be oxidized to be low-volatile compounds, and then form the
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secondary aerosols.15,24-26 The analysis of these signature elements and compounds
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could help pinpoint the primary and secondary contribution of ship emissions.15,26
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Compared with the off-line chemical analysis, aerosol time-of-flight mass
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spectrometer (ATOFMS) can provide on-line chemical information of ambient
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aerosols at single-particle level.27 ATOFMS has been applied in the land-based
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measurement for estimation of the influence of ship emissions to ports or coastal
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cities without heavy oil combustion industries.18-20 In these studies, vanadium was
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used as a typical signature for the primary ship emitted particles.
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The air quality model simulation with ship emission inventory is also an
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important tool to evaluate the contribution of ship traffic to air quality on global and
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regional scale.24,28,29 The previous simulation of air pollution related to ship traffic
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were usually based on annual or monthly averaged ship emission inventories.30,31
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With the application of ship automatic Identification System (AIS) data in building
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ship emission inventory, the resolution of ship emission map has been revolutionarily
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improved.32 With the improvement, the numerical air quality models could combine
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with high–resolution ship emission inventory to simulate the impact of ship emissions
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simultaneously.
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Megacity Shanghai, located in the Yangtze River Delta (YRD) region in East China,
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is an area of 99,600 square kilometers with a population of 75 million people and has
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the fastest growing economy, the largest total economic output, and the most
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development potential of the economy sector in China. Shanghai Port, surpassing
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Singapore Port, has become the world’s largest container shipping port for five
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consecutive years (2010-2014) (www.portshanghai.com.cn). Urban Shanghai, located
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in a river to sea delta, has been experiencing the combined influence of ship emissions
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from the Yangtze River, the Huangpu River and East China. This may have caused
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substantial atmospheric pollution and worsened the current air-pollution situation in 3
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megacity Shanghai. Recent studies have reported on ship emissions and their potential
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impacts in the YRD in China. Yang et al33 first reported about the ship emissions in
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Shanghai. Zhao’s study34, utilizing conventional filter aerosol sampling techniques,
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indicated that ship traffic had a non-negligible impact on the air quality in Shanghai
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and the YRD region. Fan et al35 presented the seasonal variation of the simulated ship
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emissions in the YRD and the East China Sea and estimated the potential influence of
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ship emissions on air quality. However, there are few reports about the direct
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measurement of ship-related aerosols in the urban region in the YRD or in China. In
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particular, there is little combination of high-resolution measurements and simulations
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to analyze the temporal characteristics of ship plumes and their impact on fine
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particles in urban or port areas in China.
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This study involves a long-term land-based field observation for ship emission
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particles in urban Shanghai. The object of this work is to evaluate the ship emission
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impacts on the urban air quality with high time resolution. We focus more on the ship
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plume periods than the annually average contribution. The methods and data analysis
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of measurements, modeling system and ship emission inventory were listed in Section
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2. The highly time-resolved primary contribution of ship emission to the urban
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atmospheric particulate matter was investigated by screening out the V-containing
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particles and presented in Section 3.1. Additionally, the high-resolution ship emission
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inventory and air quality simulation during ship plume events were made to apportion
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the ship traffic sources and comprehensively assess the influence of ship traffic on air
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quality in urban Shanghai.
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2. Methods and Data Sources
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2.1 Single Particle Measurement and Data Analysis
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Real-time single particle chemical measurement by an ATOFMS (TSI3800,
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Shoreview, MN, USA)27 was carried out at the campus of Fudan University (31°19’N,
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121°30’E). The campus is located in the northeast of downtown Shanghai and within
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approximately 7 km downstream of the Huangpu River. To the northeast of the 4
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sampling site is the Yangtze River Estuary that connects to the East China Sea. The
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main ports of Shanghai are labeled in the map (Figure 1). In order to reveal the
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possible seasonal variation of ship emission particles, a long-term measurement
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covering different seasons and years was carried. The sampling months were April
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2010, October 2010, October 2011, March - June 2012, September - October 2012,
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and January 2013.
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The size range of particles measured by ATOFMS is 200nm-2µm. Although the
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particles smaller than 200nm and larger than 2µm could account for certain parts of
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ship emission12, the size range of ATOFMS covers a major part of ship emitted
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particles with relatively long atmospheric residence time. Detailed ATOFMS
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measurements are described in the supporting information.
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Figure 1
Map of the sampling sites and the ports around the site
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The vanadium (V) component in particles is a good marker of heavy fuel oil
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combustion.18,36 Heavy fuel oil containing a high fraction of V is mainly used by
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marine vessels passing by, entering or leaving the Shanghai ports.37 V-containing 5
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particles could be a reliable indicator of ship traffic source because the ratio of V/Ni
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in ambient aerosol in Shanghai port was calculated to be 3.4, very close to the ratio of
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averaged V and Ni content in ship heavy fuel oils.34 Ship emission particles were
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screened using the markers of vanadium peaks ([V]+ and [VO]+) at m/z+51 and
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m/z+67 with a threshold of the peak area greater than 0.10% of the total peak areas of
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the mass spectrum. To distinguish the vanadium peaks from other OC fragment peaks
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at the same m/z, the ion peak at m/z+51 (or m/z+67) was not identified as [V]+ (or
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[VO]+) unless its peak area was larger than the area of the peaks at m/z+50 and
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m/z+49 (or m/z+66 and m/z+68). In this study, a total of 194,564 ship emission
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particles were observed (Table 1) and separated into half-hour segments for time
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resolution. We divided the half-hour screened V-containing particle counts by the
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corresponding half-hour effectively measured particle counts to obtain the half-hour
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number fraction of V-containing particles (NFV). It should be noted that NFv is an
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indicator of the contribution of primary ship emission to the ambient particles.
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2.2 Meteorological data, modeling system and ship emission data The
meteorological
data
were
obtained
from
Weather
Underground
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(http://www.wunderground.com) and the Chinese National Ordinary Weather Station
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in Baoshan. The Hybrid Single Particle Lagrangian Integrated Trajectory Model
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(HYSPLIT-4), the Weather Research and Forecasting (WRF) model (version 3.3)38
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and the Community Multi-scale Air Quality (CMAQ) model39 were used for the
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meteorological analysis from April 20th–22nd, 2010. The vertical layers of models
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were set to be 24, with 19 meters for the first layer. The more detailed meteorological
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data and model setup of WRF/CMAQ are described in the supporting information
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Text S3.
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2.3 Ship emission and land-based emission data
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Hourly ship emission inventories for air pollutants such as SO2, NOx, HC, CO, and
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PM2.5 during this period were estimated based on Automatic Identification System
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(AIS) data using an emission model.35 Generally, the ship emission was built as an
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activity-based marine vessels emission inventory. The equations to estimate ship
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emission was described in supporting Text S4. The actual speed and operation time of
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ship involved in estimation of ship emissions can be obtained accurately from AIS
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data. AIS data lacks information such as the installed power of main engines and total
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power of the auxiliary engines etc. The maximum speed designed for ships were
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supplemented from Lloyd's database. The sulfur content of HFO used by main
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engines is assumed as 2.7% for international ships and as 1.5% for domestic ships.35
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The stack heights of ships were assumed as 35 m and located in the second vertical
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level in numerical simulation. The other land sources were included in the emission
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inventory including power plants, industry, transportation, residential and agriculture
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etc. The land-based emission database was combined from the Transport and
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Chemical Evolution over the Pacific (TRACE-P), the Multi-resolution Emission
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Inventory for China (MEIC) and the fine-resolution Emission Inventory for Shanghai
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(SEMC) and for Baoshan.40,41
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3. Results and discussion
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3.1 Variation of ship-emission related aerosol by ATOFMS in urban Shanghai
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The measurement results contained 8,172 half-hour sets of data. Overall, the
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half-hour number fractions of V-containing particles (NFv) in all sampling hours
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varied over a wide range (
