4.4 Water pollution

• Sewage, agricultural run-off, industrial effluent

• Urban run-off, solid waste disposal, oil spills

• Marine environments

• Oceanic gyres, microplastics enter food chain

• Chemical, physical, biological characteristics

• Water quality index (WQI)

• Parameters: dissolved O₂, pH, temperature, turbidity, nitrates, phosphates, metals

• Dissolved oxygen required by microorganisms for decomposition

• mg O₂ per litre in 5 days at 20°C

• Mineral nutrient inputs (nitrates, phosphates)

• Excessive phytoplankton growth (algal blooms)

• Impacts and changes to aquatic system

• Eutrophication can substantially impact ecosystem services

• Eutrophication can affect services associated with fisheries, recreation, aesthetics and health

• Eutrophication can be addressed at three different levels of management

• These three levels of management are:

• the reduction of human activities that produce pollutants—e.g., alternatives to current fertilizers and detergents

• the reduction of the release of pollution into the environment—e.g., treatment of wastewater to remove nitrates and phosphates