Marine Air Quality Monitoring Cooperation between EPA and OAC


In 2022, the EPA cooperated with the Ocean Affairs Council to monitor the air quality over the ocean, extending the scope of Taiwan’s air quality monitoring from land to sea. The primary monitoring results show that the low-sulfur vessel fuel policy implemented since 2020 has yielded good results. Sulfur dioxide concentration has been significantly reduced. It was also discovered that vessels that reduced speed when entering or leaving ports also led to reduced pollution emission. Relevant results will be gradually applied in the drafting and promotion of marine air pollution prevention policies.      

Currently, standard air quality monitoring equipment has been installed on Coast Guard ships stationed at Tamsui in New Taipei, Taichung and Tainan and has been monitoring PM2.5, sulfur dioxide and nitrogen dioxide since October 2022. Taking the Tamsui flotilla as an example, the average sulfur dioxide concentration measured onboard was 0.68 ppb, better than the 1.37 ppb measured at the nearby land-based Tamsui monitoring station. This shows that the better diffusion conditions at sea made air quality over the ocean better than that in land areas.

In addition, looking at the changes in sulfur dioxide concentration at four coastal land-based monitoring stations in Tamsui, Keelung, Mailiao and Xiaogang, the average was 1.93 ppb in 2021 and 1.52 ppb in 2022, which are better than the 3.5 ppb recorded in 2021 of neighboring Busan port in South Korea. In addition, they were also better than 3.51 ppb, the average concentration measured at the four stations in 2018, a 60% drop. The reason is likely due to measures implemented in Taiwan since 2019, including the promotion of “use of low-sulfur fuel only by vessels on international routes between international commercial ports” and the “tightening of restrictions on the composition of fuels used by mobile and stationary pollution sources.” These measures comprehensively reduced the sulfur content of the fuels used by both vehicles on land and vessels at sea from 3.5% to 0.5%, resulting in significant environmental improvement after their implementation.

The general traveling speed of vessels is about 20 knots. But according to studies, the energy consumption and air pollution emission are at the lowest if the average speed of vessels is reduced to 12 knots. Hence, the EPA has been cooperating with port authorities in recent years to promote the reduction of vessel speeds when entering or leaving ports. However, according to data, vessels only reduced speed by 56% and 43% when entering or leaving ports, respectively, showing that there is still room for improvement. In addition, according to the monitoring results of this project, the concentration of nitrogen dioxide measured in October by the Tamsui flotilla at the port exit was 15.32 ppb, higher than the average 9.55 ppb measured five nautical miles off the shore. One of the reasons was that vessels did not reduce speed when entering or leaving the port. All these information will serve as reference for the EPA when formulating incentive or prevention measures to promote the reduction of vessel speeds when entering or leaving ports.            

Taiwan is a maritime country with living environments prone to both land-based and marine pollution sources. Understanding the air quality in marine areas will help policy makers form more effective prevention strategies targeted at various pollution sources. It is hoped that the cross-field cooperation will continue, leading to an improvement in environmental quality.  

Excerpt from Major Environmental Policies, December 2022
Environmental Protection Administration, R.O.C.(Taiwan)
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