2.1. 

>span class="s7">>span class="s7"> addresses a general environmental problem such as: acid rain, green house effect, ozone layer, radioactive waste, radon gas, heavy metals, eutrophication, pesticides, chlorinated organic compounds, dioxin, smog etc.

Also it is possible to focus on possible solutions of environmental problems. For instance:

Alternative energy forms, alternative production processes, waste recirculation, sewage or waste water treatment etc.

Here there is often unlimited literature, and it will be quietnecessary to choose only a small part of these issues. In case of acid rain one could for example choose a subject such as fish dea>span class="s7"> the problem geographically to China, southern Asia or specific area in the world.

2.2. Case study

>span class="s7"> study that concerns a specific emission source or recipient. Examples for such studies are Daya Bay Nuclear Power Plant, coal relied factories like steel, glass and petrochemicals, diesel trucks, a limited oil leakage from oil carrier or a platform, Dong River, Landfill sites, air pollutants in Hong Kong etc.

In a case study >span class="s7">extent of the problem is often restricted by its context. >span class="s7">and therefore become more treatable. We have seen many good reports based on case studies.