Smog, heat can be channeled away by network of parks, rivers and structures

As the Beijing city government enters the final stage of its relocation to new offices in the east-side Tongzhou district, experts have proposed building "ventilation corridors" to prevent the kind of smog seen in downtown areas.

The corridors are envisioned as a network of parks, rivers, highways, bridges and low buildings, which together allow air to travel more freely.

Urban planning chiefs are now considering a proposal by the Beijing Meteorological Service to build 17 such corridors in Tongzhou, which will house all municipal agencies and tens of thousands of government employees by 2020.

One goal is to prevent expansion of the capital's urban heat island, an area where the temperature is significantly warmer than surrounding rural areas because of materials like concrete and asphalt, as well as other things related to human activity.

Beijing's heat island is already 1,175 square kilometers, involving about 80 percent of the six downtown districts－Dongcheng, Xicheng, Haidian, Chaoyang, Fengtai and Shijingshan－according to Du Wupeng, deputy director of the meteorological service.

Du said images from weather satellites show that temperatures within the island are 3 degrees higher on average than in the surrounding countryside.

Using the ventilation corridors, wind blowing from the north will disperse airborne pollutants in central Tongzhou by improving circulation, as well as have a cooling effect, which would reduce electricity usage, Du said.

The relocation of Beijing's city government is aimed at reducing overcrowding and congestion in downtown areas, which also house the headquarters of many State agencies, universities, major corporations and foreign embassies.

It also aims to create a world-class livable zone in Tongzhou that emphasizes environmental protection and cultural heritage, according to Wei Chenglin, director of the Beijing Urban Planning and Land Resources Committee.

"With wind carried from outside the capital," Du said, "residents in Tongzhou will enjoy a more comfortable environment."

The service has proposed 10 corridors with a width of more than 1 kilometer and seven with a width of up to 200 meters. Those would be in addition to the corridors proposed in a separate plan for downtown Beijing that was submitted in September. That plan suggests building more than 15 corridors, the widest about 500 meters, by 2035.

Du added that as the city center expands southeast, large ecological defenses such as greenbelts and shrubs should also be created to prevent new heat islands in the Beijing-Tianjin-Hebei region.

Environmental expert Shi Guoliang said the corridors can play a potentially significant role in dispersing small polluting particles, including PM2.5－particulate matter with a diameter of less than 2.5 microns that can penetrate the lungs and seriously harm health.

"It's a good way to create a clear channel between the urban area and suburbs to reduce the heavy pollution of the Beijing-Tianjin-Hebei area," said Shi, associate professor of environmental sciences at Tianjin's Nankai University.

Xiongan New Area, a newly established economic zone neighboring Beijing in Hebei province, also plans to build ventilation corridors.

A number of Chinese cities have similar ambitions. Last year, Chengdu unveiled plans for eight large ventilation corridors and several smaller ones.