A mobile air monitoring system is exhibited at the "Ecology of a Big City" international environmental forum in St. Petersburg, Russia, March 24, 2026. The forum kicked off here on Tuesday, attracting more than 6,000 participants. (Photo by Guo Feizhou/Xinhua)

An automated vehicle emissions testing device is exhibited at the "Ecology of a Big City" international environmental forum in St. Petersburg, Russia, March 24, 2026. The forum kicked off here on Tuesday, attracting more than 6,000 participants. (Photo by Guo Feizhou/Xinhua)

A model of a vessel designed to handle oil spills is exhibited at the "Ecology of a Big City" international environmental forum in St. Petersburg, Russia, March 24, 2026. The forum kicked off here on Tuesday, attracting more than 6,000 participants. (Photo by Guo Feizhou/Xinhua)

An acoustic detection system is exhibited at the "Ecology of a Big City" international environmental forum in St. Petersburg, Russia, March 24, 2026. The forum kicked off here on Tuesday, attracting more than 6,000 participants. (Photo by Guo Feizhou/Xinhua)

A biodegradation measurement system is exhibited at the "Ecology of a Big City" international environmental forum in St. Petersburg, Russia, March 24, 2026. The forum kicked off here on Tuesday, attracting more than 6,000 participants. (Photo by Guo Feizhou/Xinhua)