The influence of spatiality on shipping emissions, air quality and potential human exposure in the Yangtze River Delta/Shanghai, China

With the increase in international maritime trade, shipping emissions and
their impacts have attracted increased attention globally over the past
decades (Capaldo et al., 1999; Cooper, 2003; Eyring et al., 2010; Sofiev et
al., 2018). Shipping emits air pollutants that contribute to adverse impacts
on climate, on air quality and on the health of people living near ports (Li
et al., 2018; H. Liu et al., 2016). Globally,
about 50 000 deaths in 2010 and about 90 000 deaths in 2012
due to cardiopulmonary diseases and lung cancer were
attributed to exposure to particulate matter emitted from shipping (Corbett et al., 2007; Partanen et al., 2013; Winebrake et al., 2009), and
403 300 premature mortalities per year due to shipping are predicted in 2020
under business-as-usual assumptions (Sofiev et al., 2018). In Europe, ozone
pollution caused by international ships led to around 3.6 % of the total
estimated years of life lost and 2.6 % of premature deaths in 2005
(Campling et al., 2013). In East Asia, around 14 500 to 37 500 premature
deaths per year have been primarily attributed to PM2.5 from shipping;
about one-third of those deaths were in the area surrounding the East China
Sea, with the largest impacts seen in mainland China (H. Liu et al., 2016).

As of 2016, China was home to 7 of the top 10 container ports, and the size
of these ports has been rapidly growing to serve the increased trade via
international shipping (UNCTAD, 2017). The Yangtze River Delta (YRD) is one
of the economic centers and is also home to the busiest port cluster, which
is comprised of more than 15 ports, including Shanghai Port, Ningbo–Zhoushan
Port, Zhenjiang Port, Nantong Port, Lianyungang Port, Taizhou Port and
Wenzhou Port. In 2016, the YRD generated a gross domestic product (GDP) of
RMB 17.72 trillion (USD 2.76 trillion) – about 20 % of China’s
national GDP (Preen, 2018). Shanghai megacity itself is an important economic
center, accounting for about 22 % of the total GDP in the YRD. Shanghai
Port lies at the intersection of the East China Sea and the Yangtze River and
has been the largest container port in the world since 2010 (Z. Liu et al.,
2016).

Shanghai and the YRD are also among the most densely populated regions of
China. The YRD is home to 239.1 million people; Shanghai is one of the
largest cities and houses about 12.1 % of the total population of the YRD
(Bright et al., 2016).

This region has suffered from severe air pollution over the past decade due
to anthropogenic emissions from multiple sources. In December 2013, for
example, the YRD experienced a haze episode, during which the maximum observed
PM2.5 concentration in the region exceeded 590 µg m−3 (Sun et
al., 2016). As severe air pollution episodes have continued and ports have
grown, the shipping sector, a subset of the transportation pollution sources,
has received more attention.

The high ship traffic density in Shanghai and the YRD has led to high
emissions of ship-related air pollutants in this region (Fan et al., 2016).
Ship-related sources of air pollution in Shanghai comprise coastal ships,
inland-water ships, cargo trucks and port terminal equipment. Because some of these
emissions sources are also close to densely populated areas, in particular
those from ships traveling in inland waterways and from container trucks
transporting cargo in and around the city, there is greater potential for
higher population exposure to ship-related air pollution.

The International Maritime Organization (IMO) regulates emissions of marine
pollution on a global scale. Current rules limit fuel sulfur content (FSC)
to 3.5 % globally and this limit will be reduced to 0.5 % in 2020. The IMO
has also designated several regional Emission Control Areas (ECAs) to
benefit the atmospheric environment and human health in port and coastal
communities that establish more stringent emission limits up to 200 NM from
the coast in the Baltic Sea (SOX), the North Sea (SOX), North America
(SOX, NOx and PM), and the US Caribbean Sea area
(SOX, NOx and PM) (Viana et al., 2015). Fuel sulfur content is
limited to 0.1 % in the ECAs.

China does not have an ECA designated by the IMO, but in December 2015 it
designated three Domestic Emission Control Areas (DECAs) that operate in a
similar manner. These DECAs limited fuel sulfur content to 0.5 % for
ocean-going vessels (OGV) in three regions: the YRD, the Pearl River Delta
(PRD) and the Bohai Sea. The DECA implementation timeline encouraged
qualified ports to be in compliance from 1 April 2016, and specified that all
ships at berth in 11 core ports within these regions would be in compliance
by 1 January 2017 and that all ocean-going vessels (OGV) or coastal vessels
within 12 NM of the shoreline would be in compliance by 1 January 2019.
These areas would also be in compliance with the IMO requirements for fuel
sulfur content. A study reported that the average reduction of PM2.5 and
SO2 mass concentrations over land in the PRD due to the DECA policy
were 2.7 % and 9.54 %, respectively (Liu et al., 2018a).
China is currently considering additional DECA restrictions for the period
beyond 2019. On 1 October 2018, 3 months earlier than originally planned, the
Shanghai Maritime Safety Administration (MSA) enforced the DECA policy
limiting the fuel sulfur content to 0.5 % for ocean-going vessels and
domestic coastal vessels in Shanghai Port. However, the DECA policies for
fuel sulfur content currently make no distinction between coastal ships that
enter inland waterways and other ships. Ships such as those in Shanghai and
the YRD that enter inland waterways bring emissions sources closer to
population centers, resulting in a greater potential for exposure and health
impacts.

Shipping emission inventories for the YRD, the PRD, and the Bohai Rim area and their
major ports indicate that shipping is an important pollution source
surrounding port regions (Chen et al., 2016; Fan et al., 2016; Li et al.,
2016; Yau et al., 2012). Several studies have investigated the contribution
of shipping emissions to the ambient air quality using different methods. Zhao et
al. (2013) analyzed aerosol samples in Shanghai Port and reported that ship
traffic contributed 0.63 to 3.58 µg m−3 (or 4.2 % to
12.8 %) of the total PM2.5 in the port. Primary ship-emitted
particles measured by an aerosol time-of-flight mass spectrometer were
typically 1.0 % to 10.0 % of the measured particle number
concentration, with the contribution rising to as high as 50.0 % in
spring and summer (Z. Liu et al., 2016). In Guangzhou and Zhuhai, shipping
emissions were among the top contributors to PM2.5 and accounted for
more than 17 % of PM2.5 mass concentrations (Tao et al., 2016).
Using WRF-CMAQ, which combines the Weather Research and Forecasting model (WRF)
and the Community Multi-scale Air Quality (CMAQ) model,
Chen et al. (2017b) found that the contribution of shipping
emissions to the PM2.5 mass concentrations in Qingdao was highest in
summer (13.1 %) and lowest in winter (1.5 %). Chen et al. (2019)
reported that ship traffic sources could contribute 4.0 % of the annual
PM2.5 mass concentrations over land in YRD and that the maximum
could reach up to 35.0 % in port regions in 2014.

In China, few studies have reported the contribution from shipping in different offshore
coastal areas or different types of ship-related sources to air pollution.
For example, Mao et al. (2017) estimated primary emissions from OGVs at
different boundaries in the PRD region, and concluded that further expansion
of the emission control area to 100 NM from shore would provide even greater
benefits. However, the impacts of shipping emissions at varying distances
from shore on air quality and potential human exposure, which are important
when considering ECA policy, have not been rigorously studied. Mao and
Rutherford (2018) studied NOx emissions from three
categories of merchant vessels – OGVs, coastal vessels (CVs) and river
vessels (RVs) in China’s coastal region. However, less attention was paid to
the impacts of inland waterway traffic and port-related sources, such as
cargo trucks and terminal port equipment, on air quality and potential human
exposure.

To fill this gap, the overall goal of this study was to characterize the
spatial distribution of ship-related emissions and their impacts on air
quality and human exposure in the YRD and Shanghai for the baseline year of
2015, which was prior to the implementation of China’s DECAs in 2016. We modeled
shipping emissions in different offshore areas in the YRD region and
emissions from different types of ship-related sources in Shanghai city for each
month of the year. To identify which offshore areas in the YRD region and
which ship-related sources in Shanghai contributed the most to ambient air
pollution, and human population exposure, we modeled the impacts of shipping
emissions in different offshore areas (within 12 NM of the coast including inland
waters and within 12–24, 24–48, 48–96 and 96–200 NM of the coast, respectively) in the YRD region as well as
coastal ships, inland-water ships, and cargo trucks and port
terminal equipment in and near the port areas under the jurisdiction of
Shanghai MSA in 2 representative months (January and June). The results of
this study could be informative regarding the consideration of the distance of
regulated emissions in the design of future emissions control areas for
shipping in the YRD, or regulations on the sulfur content of fuels for
different types of ship-related sources in Shanghai.