Lecture

Nitrogen Cycle: Understanding Its Processes and Impacts

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Description

This lecture focuses on the nitrogen cycle, detailing its significance in biogeochemistry and the environment. The instructor begins by discussing the importance of nitrogen as a key element in biomass and its various oxidation states. The lecture outlines the five key processes involved in nitrogen cycling: nitrogen fixation, nitrification, denitrification, ammonification, and anammox. The instructor emphasizes the role of microorganisms in these processes and highlights the impact of human activities, particularly the use of chemical fertilizers, on nitrogen fluxes and groundwater contamination. The lecture also addresses the balance between natural nitrogen fixation and anthropogenic contributions, illustrating how industrial practices have altered the nitrogen cycle. The instructor presents data on nitrogen levels in groundwater and discusses the implications for agriculture and environmental health. The session concludes with a call for smarter agricultural practices to mitigate the negative effects of excess nitrogen in ecosystems, particularly in relation to eutrophication in aquatic environments.

Official source

Ontological neighbourhood

Biology

Ecology: Ecosystems

Related concepts (32)

Nitrogen cycle

The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is atmospheric nitrogen, making it the largest source of nitrogen.

Nitrification

Nitrification is the biological oxidation of ammonia to nitrite followed by the oxidation of the nitrite to nitrate occurring through separate organisms or direct ammonia oxidation to nitrate in comammox bacteria. The transformation of ammonia to nitrite is usually the rate limiting step of nitrification. Nitrification is an important step in the nitrogen cycle in soil. Nitrification is an aerobic process performed by small groups of autotrophic bacteria and archaea.

Nitrogen fixation

Nitrogen fixation is a chemical process by which molecular nitrogen (N2), which has a strong triple covalent bond, is converted into ammonia (NH3) or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. The nitrogen in air is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms. Biological nitrogen fixation or diazotrophy is an important microbe-mediated process that converts dinitrogen (N2) gas to ammonia (NH3) using the nitrogenase protein complex (Nif).

Agriculture

Agriculture encompasses crop and livestock production, aquaculture, fisheries and forestry for food and non-food products. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to live in cities. While humans started gathering grains at least 105,000 years ago, nascent farmers only began planting them around 11,500 years ago. Sheep, goats, pigs and cattle were domesticated around 10,000 years ago.

Eutrophication

Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytoplankton productivity". Water bodies with very low nutrient levels are termed oligotrophic and those with moderate nutrient levels are termed mesotrophic. Advanced eutrophication may also be referred to as dystrophic and hypertrophic conditions.

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