As of 1st January 2020, International Maritime Organization (IMO) enforced the Sulphur Emission Regulations which require that all ships shall reduce their Sulphur emissions from 3,5 % to 0,5% in all of the world's seas.

The implementation of the global 0.50% Sulphur limit has not changed the requirements applicable to the four ECAs designated under Regulation 14 of MARPOL Annex VI. So in the North American, US Caribbean, the North Sea, and the Baltic 0,10% Sulphur limit continue to apply.
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To access ECA / SECA zones, just go to the right menu and choose the Map Layers icon from there.

China introduced its own domestic ECA regulations requiring max 0,50 % Sulphur content in September 2015. In November 2018 a new Coastal ECA was introduced which includes all sea areas and ports within China’s territorial sea including the province of Hainan and two inland ECAs being parts of the Yangtze and the Xi Jiang River. Ships must currently use fuel with a 0.5% Sulphur content limit when entering into the ECA

The three ECAs are the Pearl River Delta, the Yangtze River Delta, and Bohai Bay.

Inland ECA regulations require max 0,10 % Sulphur content and include the navigable waters of the Yangtze River and the main lines (from Shuifu in Yunnan Province to Liuhe Estuary in Jiangsu Province) and the Xijiang River main lines (from Nanning in Guangxi Province to Zhaoqing in Guangdong Province).

From 1 September 2020, all vessels berthing or at anchorage in the Korean ECAs must burn fuel with a maximum sulfur content of 0.10%. The Korean ECAs cover Korea’s five major port areas: Incheon, Pyeongtaek-Dangjin, Yeosu-Gwangyang, Busan, and Ulsan.

Read more about Designation of SOX Emission Control Area in the Republic of Korea.

Australia

From the 1st of January 2020 the Sulphur content of fuel used for propulsion or operation onboard a vessel must not exceed 0,50 %. Local regulations enforce 0.10% to cruise ships in Sydney harbor. Regulation 4 also applies, and EGCS can be used as an alternative means of compliance if at least as effective in terms of SOX emissions reduction as the fuel Sulphur limit.

View Emissions Regulation & EGCS Guidance in Australia.

EU’s Sulphur Directive says all ships berthing inside an EU port have to use marine fuels with a Sulphur content not exceeding 0,10%. If they arrive at a berth with fuel oil onboard with a higher Sulphur content the vessel needs to start a fuel changeover operation as soon as possible after arrival at a berth and as late as possible before departure.

From the 1st of January 2020, the Sulphur content was reduced to 0,10 % in Icelandic territorial waters – along with fjords and bays . Vessels will be banned from using heavy fuel within Icelandic territorial waters unless employing authorized methods to reduce Sulphur dioxide emissions.

From 1 March 2019, the Norwegian world heritage fjord area, including the Nærøyfjord, Aurlandsfjord, Geirangerfjord, Sunnylvsfjord, and Tafjord in Western Norway, were included in the ECA 0.10% Sulphur limit.

From the 1st of January 2020, Norway adopts to the EU’s Sulphur Directive (0,10 % Sulphur content) and all ships berthing inside a Norwegian port have to use marine fuels with a Sulphur content not exceeding 0,10%. The Norwegian environmental instruction also states that as a minimum the vessels need to document they comply with operational and technical measures for reducing particle matter emissions and visible smoke, and speed as a measure for reducing emissions and discharges.

January 1, 2020, when the limit will be reduced to 0,50%. The Irish Seas exemption from the EU Sulphur Directive comes to an end, in January 2020, and from the 1st of January 2020 the Irish Sea will be included in the EU Directive and limit the vessels trading in this area reducing the Sulphur content to 0,10%.

Read press release from European Commission to learn more.

Has its own Sulphur emission regulations, thus aligned with the regulations in EU ports (Sulphur content not exceeding 0,10 %) for all ships berthing in Turkish ports or operating in Turkish inland waterways. The regulations do not apply for vessels transits in Bosporus and Dardanelles and Marmara Sea unless these vessels in transit have anchored in the area for more than 2 hours.

On your mobile phone, you will access the information about ECA / SECA zones under Map styles. Click on the layer in the map to find info on the specific zone.

http://www.gard.no/web/updates/content/29212584/regional-sulphur-emission-limits-at-a-glance

https://britanniapandi.com/2020/01/low-sulphur-regulations-after-1-january-2020/

Seems that there is a "new" industry growing up due to these relatively new environmental requirements in the maritime industry discussing how to comply with these environmental regulations: