Dramatic increase in reactive volatile organic compound (VOC) emissions from ships at berth after implementing the fuel switch policy in the Pearl River Delta Emission Control Area

• Main Authors: Z. Wu, Y. Zhang, J. He, H. Chen, X. Huang, Y. Wang, X. Yu, W. Yang, R. Zhang, M. Zhu, S. Li, H. Fang, Z. Zhang, X. Wang
• Format: Article
• Language: English
• Published: Copernicus Publications 2020-02-01
• Series: Atmospheric Chemistry and Physics
• Online Access: https://www.atmos-chem-phys.net/20/1887/2020/acp-20-1887-2020.pdf
• ISSN: 1680-7316; 1680-7324

<p>Limiting fuel sulfur content (FSC) is a widely adopted approach for reducing ship emissions of sulfur dioxide (<span class="inline-formula">SO₂</span>) and particulate matter (PM), particularly in emission control areas (ECAs), but its impact on the emissions of volatile organic compounds (VOCs) is still not well understood. In this study, emissions from ships at berth in Guangzhou, southern China, were characterized before and after the implementation of the fuel switch policy (IFSP) with an FSC limit of 0.5&thinsp;% in the Pearl River Delta ECA (ECA-PRD). After IFSP, the emission factors (EFs) of <span class="inline-formula">SO₂</span> and PM<span class="inline-formula">_2.5</span> for the coastal vessels decreased by 78&thinsp;% and 56&thinsp;% on average, respectively; however, the EFs of the VOCs were <span class="inline-formula">1807±1746</span>&thinsp;mg&thinsp;kg<span class="inline-formula">⁻¹</span>, approximately 15 times that of <span class="inline-formula">118±56.1</span>&thinsp;mg&thinsp;kg<span class="inline-formula">⁻¹</span> before IFSP. This dramatic increase in the emissions of the VOCs might have been largely due to the replacement of high-sulfur residual fuel oil with low-sulfur diesel or heavy oils, which are typically richer in short-chain hydrocarbons. Moreover, reactive alkenes surpassed alkanes to become the dominant group among the VOCs, and low-carbon-number VOCs, such as ethylene, propene and isobutane, became the dominant species after IFSP. As a result of the largely elevated EFs of the reactive alkenes and aromatics after IFSP, the emitted VOCs per kilogram of fuel burned had nearly 29 times greater ozone formation potential (OFP) and approximately 2 times greater secondary organic aerosol formation potential (SOAFP) than those before IFSP. Unlike the coastal vessels, the river vessels in the region used diesel fuels consistently and were not affected by the fuel switch policy, but the EFs of their VOCs were 90&thinsp;% greater than those of the coastal vessels after IFSP, with approximately 120&thinsp;% greater fuel-based OFP and 70&thinsp;%–140&thinsp;% greater SOAFP. The results from this study suggest that while the fuel switch policy could effectively reduce <span class="inline-formula">SO₂</span> and PM emissions, and thus help control PM<span class="inline-formula">_2.5</span> pollution, it will also lead to greater emissions of reactive VOCs, which may threaten ozone pollution control in harbor cities. This change for coastal or ocean-going vessels, in addition to the large amounts of reactive VOCs from the river vessels, raises regulatory concerns for ship emissions of reactive VOCs.</p>