Team members install a monitor in the roof lamp of a taxi.

A team from Tongji University have come up with some interesting findings after installing air quality monitors on city taxis more than a year ago.

“Government environmental monitoring stations are fixed in one place and collect information only once every couple of hours. That’s just not frequently for us,” said Tan Hongwei of Tongji’s green architecture and new energy research center.

“We need monitoring at street level and in communities. And we need to improve collection of real-time data. We are developing the idea of a citywide monitoring system with drones, taxis and fixed stations,” he said.

“The taxis carry our devices into the streets and back lanes where people live and work. They run around the clock bringing us real-time data every minute of the day.”

The devices were developed at Shandong University and use laser sensing technology to generate data every few seconds.

Tan’s team installed devices inside the roof lights of 30 Qiangsheng Taxi Co cabs in December 2017.

They are at head height and the lights’ covers protect them from heat, wind, rain and snow.

Mainly focused on PM2.5, each monitor produces about 27,000 pieces of data each day. Devices have been developed that can be installed on drones.

“Everyone believed that pollution was more serious downtown than in the suburbs, but we found that not to be the case,” said Tan. “We guess it’s because pollutants are carried into the city from outside, so it depends on factors such as wind and geography.”

They also found the eastern part of the city was less polluted than the west.

“The Pudong New Area is vast and close to the sea,” Tan explained.

It turned out that the busiest streets were not necessarily more polluted than surrounding roads, another counter-intuitive finding.

“Today’s cars do not discharge PM2.5 pollutants directly. Instead, they produce catalysts and raw materials for the formation of the pollutants,” said Tan. “So pollution is sometimes more serious on streets near the congested roads as the fumes spread.”

There are devices on 100 taxis in Jinan, capital of Shandong Province, and the data has been bought by the government, according to Tan.

“We are planning to add 70 more taxis to the program in Shanghai,” he said.

The team are looking for volunteers to install monitors in their homes to investigate how habits and architecture influence indoor air quality.