A multi-year quantitative study of the influence of ship emissions on urban air quality by a team from Fudan University found that ships could contribute 20–30% (2–7 μg/m3) of the total PM2.5 within tens of kilometers of coastal and riverside Shanghai during ship-plume-influenced periods. A paper on the study is published in the ACS journal Environmental Science & Technology.
In the study, multiyear measurements and a high-resolution air-quality model with hourly ship emission inventory were combined to determine the influence of ship emissions on urban Shanghai. The aerosol time-of-flight mass spectrometer (ATOFMS) measurements were carried out at an urban site from April 2009 to January 2013.
|Credit: ACS, Liu et al. Click to enlarge.|
During the entire sampling time, most of the half-hourly averaged number fractions of primary ship emitted particles varied between 1.0–10.0%. However, the number fraction could reach up to 50% during the ship plume cases. Ship-plume-influenced periods usually occurred in spring and summer.
Megacity Shanghai, located in the Yangtze River Delta (YRD) region in East China, is an area of 99,600 km2 with a population of 75 million people and has the fastest growing economy, the largest total economic output, and the most development potential of the economy sector in China. Shanghai Port, surpassing Singapore Port, has become the world’s largest container shipping port for five consecutive years (2010−2014). Urban Shanghai, located in a river-to-sea delta, has been experiencing the combined influence of ship emissions from the Yangtze River, the Huangpu River and East China Sea. This may have caused substantial atmospheric pollution and worsened the current air-pollution situation in megacity Shanghai.
Recent studies have reported on ship emissions and their potential impacts in the YRD in China. … However, there are few reports about the direct measurement of ship-related aerosols in the urban region in the YRD or in China. In particular, there is little combination of high-resolution measurements and simulations to analyze the temporal characteristics of ship plumes and their impact on fine particles in urban or port areas in China.
… This study involves a long-term land-based field observation for ship emission particles in urban Shanghai. The object of this work is to evaluate the ship emission impacts on the urban air quality with high time resolution. We focus more on the ship plume periods than the annually average contribution.—Liu et al.
The measurement results contained 8,172 half-hour sets of data. Overall, the half-hour number fractions of vanadium-containing particles (NFv) (vanadium is a good marker for heavy fuel oil combustion) in all sampling hours varied over a wide range (<0.1−52.5%) but mainly were between 1% and 10%. These contribution values are consistent with studies in other cities.
East and southeast winds dominated during the high ship-emission-influenced periods, while the winds mainly blew from the north and northwest in the low ship-emission- influenced periods.
When wind speed is less than 0.5 m/s, the air mass is usually stagnant and indicative of the local emission particle pollution. The more frequent occurrence of extremely low speed winds during the high ship-emission-influenced periods than in the low ship-emission-influenced periods suggests that ship emissions are a source for local haze pollution, which corresponds with the large cargo throughput in Shanghai shipping lanes, the researchers said.
The contribution of ship emissions on air quality showed great variability in the spatial and temporal scales. With the combined influence of ship lanes in rivers and the sea, ship traffic emissions have contributed greatly to aerosols in coastal urban Shanghai. The impact of ship emissions on the environment and human health should be taken into serious consideration in the future.—Liu et al.
Zhanmin Liu, Xiaohui Lu, Junlan Feng, Qianzhu Fan, Yan Zhang, and Xin Yang (2016) “Influence of Ship Emissions on Urban Air Quality: A Comprehensive Study Using Highly Time-Resolved Online Measurements and Numerical Simulation in Shanghai” Environmental Science & Technology doi: 10.1021/acs.est.6b03834