Reactions and Biological Interactions

Once a chemical is released to the environment, biotic and abiotic reactions may degrade or transform the substance. 

Biodegradation may be aerobic or anaerobic. Aerobic degradation can occur when sufficient oxygen is available to serve as the terminal electron 

Some compounds break down partially to form other organic compounds. Those degradation products may persist or undergo further degradation. Ultimate biodegradation, sometimes referred to as mineralization, means that a substance degrades to carbon dioxide, water, biomass, and inorganic substances such as ammonia. 

Engineers typically model the progression of biodegradation over time as a first-order reaction, that is. 

An organic substance resists biodegradation in two general cases if it is hydrophobic or if the chemical bonds in the substance cannot be readily broken. Each case is briefly described below. 

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