the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
The impact of inland ship emissions on air quality
- 1KNMI-NUIST Center for Atmospheric Composition, Nanjing University of Information Science and Technology (NUIST), Nanjing 210044, China
- 2Royal Netherlands Meteorological Institute (KNMI), Department of Satellite Observations, De Bilt, the Netherlands
- 1KNMI-NUIST Center for Atmospheric Composition, Nanjing University of Information Science and Technology (NUIST), Nanjing 210044, China
- 2Royal Netherlands Meteorological Institute (KNMI), Department of Satellite Observations, De Bilt, the Netherlands
Abstract. Despite the large number of domestic inland river vessels in China, information on inland river vessel emissions is very limited, because limited legislation exists for emission control and there is no monitoring infrastructure. Taking the Yangtze River in the region of Nanjing as research area, we compiled a ship emission inventory based on real-time information received from Automatic Identification System (AIS) signals and ship-related basic data provided by China Classification Society (CCS) database. The total estimated ship emissions in the Jiangsu section of the Yangtze River from September 2018 to August 2019 for NOx, SO2, PM10 and PM2.5 were 83.5, 41.8, 3.8 and 3.3 kton, respectively. These ship emissions were highest in the summer. From these estimates an inventory was constructed for ship emissions in the Yangtze River Delta (YRD) in Jiangsu. This ship emission inventory was compared with the Multi-resolution Emission Inventory for China (MEIC), the Shipping Emission Inventory Model (SEIM) and the satellite-derived emissions using the Daily Emissions Constrained by Satellite Observations (DECSO) algorithm. The result shows a consistent spatial distribution with riverine cities having higher NOx pollution than non-riverine cities. With this comparison we analyzed the relative impact of ship emissions on densely populated regions along the river. Inland ship emissions of NOx and SO2 are shown to contribute significantly, with each accounting for at least 40 %, to air pollution along the river.
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Xiumei Zhang et al.
Status: open (until 11 Feb 2023)
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RC1: 'Comment on egusphere-2022-1411', Anonymous Referee #1, 27 Jan 2023
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The study of Zhang et al. built a ship emission inventory based on AIS signals and basic ship-related data for YRD region. The results were compared with several other emission inventories to verify reliability of the proposed approach and demonstrate the impact inland ship emissions on densely populated regions along the river.
The topic is interesting, but the publication has major deficiencies, is difficult to follow. In my view it cannot be published in the present form but will need substantial improvements.
Major issues:
- The title is completely inappropriate. It’s named ‘The impact of inland ship emissions on air quality’. The title exaggerates the actual research scope seriously. The manuscript is almost entirely about emissions (Introduction, Methods and Discussion) rather than air quality. And the only description of air quality in Line 424-425 seems not correct, because the air pollution such as PM2.5 induced by ship emission also affected by other emission sources and meteorological condition. Therefore, the title should be modified at least. Otherwise, more quantitative study on air quality should be carried out. This study only investigated the Yangzi river- Jiangsu section, which is a short section, also can NOT represent YRD region as well. The title needs to honestly reflect the scope of the work done. The title is too big at present.
- There are many mistakes in the review of the research status and the current situation of ship emission control. The authors need to re-write the literature review to include the most advanced and high quality research.
- The control policy of inland ships is different from that of oceangoing ships. Even for oceangoing ships, China's current control policy is not only in the three major control areas, but for the coastal waters of 12 nautical miles. The author has not quoted the latest research on inland river-related ship emissions.
- This study assumed that the average sulfur content of marine distillates (MD) of 1.5 % in the study area according to Xu et al. (2019), which was based on the data of 2014. However, this study was implemented from 2018 to 2019. The sulfur content for inland ships was totally different, which makes the results wrong.
- The author mentioned "We set up an AIS receiver in Nanjing University of Information Science and Technology (NUIST) to collect ship information including ship position, speed and heading, ship name, ship length and ship type”. What’s the power threshold for this receiver can receive from ships? What is the percentage of missing signals? With the distance getting farther, there are more missing signals. How to evaluate the emissions of lost ships? More details of the AIS receiver should be presented.
- Ship emission is not only related to the length of the river. For example, in some major ports, the emission is large while the length may not high. The author should present more proofs to prove the proposed method that estimates the emission to larger regions based on the length of the river per grid cell. Such as plotting the relationship of emission and the length for the observational area or listing some references.
- It was not clear that how the 3-4% underestimation in Line 327 be calculated, and except for the emission from the auxiliary engine, the emission from the boiler was also not considered. How much did the boiler emission account for?
- Almost any sources of emission will account for a large share ratio in the grid where they emit. To illustrate the importance of emissions for inland vessels, the author should compare emissions in specific cities or regions (coastal cities, YRD …) rather than the selected river grid cells.
- The author should explain why there was a big difference between JESI and SEIM, especially for SO2 and PM2.5 in Section 4.1. Additionally, in the latest version of SEIM (Wang et al., 2021. Ship emissions around China under gradually promoted control policies from 2016 to 2019), the emissions over inland rivers are all included.
Smaller issues:
- Line 183, it should be Figure S1 rather than S2.
- In Figure 9 and Figure 11, why the sharing ratio of JESI is low in some grid of which most part is river?
- Line 379, why the author said “The MEIC grid cells cover a larger area than for DECSO and include more emissions than DECSO”.
- In Line 402, the author said “ship emissions accounted for more than 40 % of the total emissions in February, which shows that the pollution caused by ship activities during Spring Festival is quite significant in a time period of lower emissions in general”. However, according to MEIC, the changes in NOx emission caused by the Spring Festival is not significant. Thus, which share is more reasonable, JESI/(JESI+SEMI) or JESI/DECSO. The author should give more proofs to support this sentence.
- The format of references should be unified. (Such as in Line 237)
Xiumei Zhang et al.
Xiumei Zhang et al.
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