Galloway et al 2013

1. Nitrogen Cycle Overview

  • Nitrogen discovered in 18th century; linked to agriculture in 19th century.

  • 20th century: Haber-Bosch process invented, leading to increased reactive nitrogen (Nr) for various uses.

  • Human-created Nr 2-3 times higher than natural sources by 21st century.

2. Historical Understanding of Nitrogen

2.1 Early Agricultural Practices

  • Initial food sources from hunting and gathering; domestication of plants/animals ~10,000 years ago.

  • Use of manure and legumes recognized for higher crop yields.

2.2 Key Discoveries in Nitrogen Chemistry

  • 1563: Bernard Palissy connected fertilizers to crop growth.

  • 1772: Daniel Rutherford discovered nitrogen.

  • 1790: Jean Antoine Claude Chaptal coined "nitrogen."

2.3 Advances in Nitrogen Science

  • Late 18th century: Chemical forms and various nitrogen compounds recognized.

  • 19th century: Nitrification, biological nitrogen fixation, and denitrification discovered.

  • 1909: Fritz Haber synthesizes ammonia; 1913: Carl Bosch scales it industrially.

3. Impacts of Human Activities on the Nitrogen Cycle

3.1 Agriculture and Nitrogen Production

  • Global reliance on synthetic fertilizers increased food production.

  • Haber-Bosch process now feeds approximately 50% of the world’s population.

3.2 Negative Environmental Effects

  • Excess Nr leads to:

    • Acid rain (1852 by Robert Angus Smith)

    • Smog (1953)

    • Coastal eutrophication and algal blooms (1950s onward).

    • Stratospheric ozone depletion.

4. Regulatory Responses to Nitrogen Impacts

4.1 United States Legislation

  • 1948: Federal Water Pollution Control Act; 1972: Clean Water Act.

  • 1974: Safe Drinking Water Act set limits on nitrate/nitrite.

  • Air Pollution Control Act and Clean Air Act regulate nitrogen oxides.

4.2 European Initiatives

  • UN Conference on the Human Environment (1972) raised awareness.

  • Legal frameworks like UNECE's Convention on Long-range Transboundary Air Pollution.

  • Nitrates Directive (1991) aims to improve water quality by limiting nitrate from agriculture.

5. Conclusion

  • Understanding of nitrogen’s role has evolved over 300 years through curiosity, scientific advances, and societal concern.

  • Ongoing challenges include optimizing nitrogen use while minimizing its negative impacts on ecosystems and human health.