''Whenever I travel abroad,'' said Ren Zhenying wryly, ''my foreign colleagues say to me, 'Oh yes, you come from Lanzhou. How is the pollution there these days?' ''
Mr. Ren, a bustling, chunky man, is deputy mayor and chief architect of Lanzhou, a city of petrochemicals and heavy industry that has been called China's second most polluted city, after Shenyang in the northeast.
Mr. Ren admits that the city is still in the early stages of its campaign against pollution. As in other developing nations, lack of sufficient funds is a serious bottleneck. ''We have so many competing claims against our limited resources,'' he said, ''that we have to set an order of priorities and follow it strictly.''
Large factories have been equipped with filters to reduce emission of sulfur dioxide and other noxious gases into the atmosphere. Two municipal waste-water treatment plants have been set up to purify the effluvia from chemical plants, and a third is planned. Some factories have been closed or moved out of town. An iron foundry recently was been turned into a shoe factory.
But as yet Lanzhou, which means city of orchids, can scarcely be praised for its blue skies or its sparkling water. Its geographic location is unfortunate: It sprawls belt-like for 37 miles, mostly along the southern side of the Yellow River, hemmed in north and south by mountains.
The older residential and administrative part of the city is in the east. The new industrial part is in the west. This was a deliberate choice, of which Mr. Ren is proud. But during the 10-year turmoil that began with the Cultural Revolution of 1966, ''There was a lot of disorder,'' Ren said, and factories were scattered about indiscriminately in the east.
Because Lanzhou sits in such a long, narrow riverside valley, the winds sweeping down from the Mongolian steppes cannot reach it, and pollution from the petrochemical and other plants in the city hangs perpetually overhead, frequently turning the sun into a moonlike wraith.
''We used to emit three flames, which citizens used to call the black dragon, the yellow dragon, and the red dragon - from their colors,'' said Zhang Liancheng, manager of the executive offices of the mammoth Lanzhou Petrochemical Corporation, which has spent more than 30 million yuan (roughly $20 million) since 1979 to solve the problem. ''Now the only dragon we have to slay is the red one - caused by leftovers from oil cracking (refining).''
Ren, meanwhile, is energetically tackling Lanzhou's other problems, such as the lack of housing. ''In the beginning we emphasized both production and housing, but soon we stressed only production at the expense of the citizens' livelihood,'' Ren said. ''We are paying the price now.'' The city's population has grown from 172,000 when the People's Republic was founded in 1949 to nearly a million.
Park building and afforestation are other goals - the surrounding hills are nearly bare. What hilltop trees one does see crown the ridges of White Pagoda Park on the Yellow River's north bank.
The park's 14th-century pagoda is one of Ren's delights, as are the other classical buildings scattered throughout the park - here a temple, there a mosque's gate. These were carefully gathered by Ren from construction sites in the city and brought here to remind citizens of their long cultural heritage. For this and other so-called crimes, Ren was branded an advocate of ''back to the ancients,'' during the Cultural Revolution. He was dismissed from office, stripped of his party membership, and imprisoned.
But what Ren says he remembers instead is seeing thousands of Lanzhou citizens, on the morrow of victory over Kuomintang troops in 1949, hauling blocks of ice from the frozen Yellow River to the hilltops, so that in the spring trees could be planted and survive. ''With the restoration of that spirit , in 20 years' time we should be flying into the 21st century.''