By taking Guiyang City as a case study, the indices for the natural ecosystem, society economy system and cropland pollution system were chosen and the land resource evaluation model was established.

以贵阳市区为例，选取自然生态系统指标、社会经济系统指标和农田污染系统指标，建立了土地资源评价模型。

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But he hopes to raise billions through a system in which businesses that release greenhouse gases would buy and trade pollution permits.

VOA: special.2009.02.27

most sweeping emissions trading system companies would have to buy permits for every ton of carbon they emit, a system designed to provide financial incentives for those that reduce their pollution.

VOA: standard.2009.05.03

The Beijing News backs a proposal by the capital's mayor to follow the example of the Yangtze River Delta and Pearl River Delta regions and set up a joint air pollution control system between Beijing, Tianjin and Hebei.

BBC: China media: Death of Chavez

The story beginning overleaf assesses the implications for marine biodiversity of transgressing planetary boundaries, due to human-induced changes to the climate system, pollution and ocean acidification, as well as more direct threats like invasive species, overfishing and habitat destruction.

UNESCO: Open Access to Scientific Information

As chief executive, Mr. Leung will have to confront a raft of issues currently facing the city, including high levels of pollution, an overstretched education system and global economic headwinds.

WSJ: Leung Chun-Ying Selected as Hong Kong Chief Executive