- Atmospheric Protection/Air Quality Control/Air Pollution 12
- Environment, general 12
- Environmental Chemistry 10
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- Waste Water Technology / Water Pollution Control / Water Management / Aquatic Pollution 10
- Ecotoxicology 9
- Biotechnology 5
- Microbiology 5
- Soil Science & Conservation 5
- Catalysis 3
- Climate Change/Climate Change Impacts 3
- Hydrogeology 3
- Inorganic Chemistry 3
- Physical Chemistry 3
- Water Quality/Water Pollution 3
- Biochemistry, general 2
- Environmental Engineering/Biotechnology 2
- Geochemistry 2
- Industrial Chemistry/Chemical Engineering 2
- Microbial Genetics and Genomics 2