On Jan 1, 2006, the regional government imposed a permanent ban on the mining of gold dust, and on Jan 1, 2008, extended it to placer iron, he said.
"The government has taken an extremely prudent approach to development planning," Zhang said.
"There are bans on high-polluting and high-energy-consuming industries such as papermaking and chemicals. During the 10th Five-Year Plan (2001-05) period, we closed down nine cement production facilities, five small iron works and four paper mills," he said.
Three small cement factories in Lhasa's north suburb have been closed down and the one remaining plant in the west suburb is operating without releasing smoke or dust. It will later be moved away from the city, he said.
"You just don't see industrial chimneys in Lhasa these days," he said.
Prominent on Zhang's list of achievements is the leading role Lhasa played in prohibiting the use of disposable plastic bags and coal-burning boilers.
"We were the first of the provincial capitals to ban plastic bags," he said.
"In the past, on windy winter days in particular, you could see all colors and sizes of plastic bags waving from tree branches and in bushes. Now, they are gone."
Now, when you return from shopping trips in Lhasa, your purchase will no longer come with plastic bags. Instead, you get reusable non-woven fabric bags.
The latest pollution-control moves include the building of garbage and sewage treatment facilities in major cities and towns, which were simply nonexistent in the past, he said.
Money is no problem, he said.
During the 10th Five-Year Plan (2001-05) period, the central and regional governments spent 2.4 billion yuan ($343 million) on environmental protection. Last year, the spending was 480 million yuan, Zhang said.
Also, of the 180 projects the State Council has endorsed for Tibet's 11th Five-Year Plan (2006-10) period, 23 relate to environmental protection, he said.
The central government will spend more than 10 billion yuan during the 11th Five-Year Plan (2006-10) period on environmental protection in Tibet, he said.
"Tibet cannot afford not to develop, but neither can we afford to damage the fragile environment, which may prove irreparable once done," Zhang said.
"But we can manage it pretty well as long as we exert strict monitoring and control."
When asked if he thought the development of the Qinghai-Tibet railway had had a negative impact on the environment, he said such a claim was "pure nonsense".
"You can see for yourself anywhere you go," he said.
"The intact vegetation and undisturbed wild animals, like Tibetan antelopes, to be found along the railway, as well as the migratory birds you can see at the Dragon King Pond and on the Lhasa River tell you all you need to know."