ABSTRACT
Aquatic environments often develop a vertical density gradient due to thermal stratification. The bottom may become anaerobic because organic matter produced through photosynthesis in the surface layer sinks to the bottom, where heterotrophic bacteria degrade it and consume oxygen.
The sources of water pollution are as follows: agriculture (fertilizers, pesticides, solid wastes), farms (wastewater, manure, insects), soil (chemical and biological pollutants), wildlife (biowaste, dead biomass), domestic wastewater (organic and inorganics pollutants, viruses, microorganisms), industrial effluent (organic and inorganic pollutants), solid wastes (organic and inorganic pollutants if not properly managed and disposed of), and air (sulfur and nitrogen oxides, dust). Steps of eutrophication are as follows: increase of water turbidity, concentration of microorganisms, concentration of toxic, allergic, or bad-smelling microbial products, decrease of dissolved oxygen concentration, decrease of biodiversity in aquatic system. A tutorial with solutions and a quiz bank are added to this chapter.
