Total organic carbon (TOC)

TOC, Kol organiskt, totalt

 TOC (Total Organic Carbon) is a direct measure of dissolved and particular organic matter in water.¹

 
Uses

TOC is not a substance, but a way of measuring organic matter and has therefore no applications.

Sources and transportation pathways

Organic matter is present naturally in water as living and dead plants and animals. However, human activity contributes to increased concentrations through for example wastewater treatment plants, industries and discharge from agriculture.² In addition, emissions of the nutrients nitrogen and phosphorous result in increased growth of algae in water, a process termed eutrophication, which in turn results in increased TOC values. The largest sources of nutrients are agriculture, municipal and industrial wastewater, forestry, road traffic and shipping.³

Effects on environment and health

Organic matter in water is degraded by aquatic microorganisms. During degradation, microorganisms consume dissolved oxygen present in the water. High levels of organic matter result in a high oxygen demand, which may create areas with oxygen deficiency. Oxygen deficiency can result in the death of for example fish.⁴ Humans can also be affected by high levels of organic matter in water if drinking water becomes contaminated by microorganisms.⁵

Extensive growth of toxic cyanobacteria (algal bloom) can occur due to high levels of nutrients in the water. These algae can be directly toxic both to aquatic organisms and to humans.⁶

International agreements and regulations

The UN Protocol on PRTRs and the EU E-PRTR regulation regulate how data on TOC emissions is made available.

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¹  http://www.matavatten.se/Mata_Vatten_3.pdf
² https://www.eea.europa.eu/data-and-maps/indicators/oxygen-consuming-substances-in-rivers/oxygen-consuming-substances-in-rivers-7 
³ https://www.havochvatten.se/hav/fiske--fritid/miljopaverkan/overgodning.html/
⁴ WWF Breathless Coastal seas engl.pub

⁵https://www.un.org/esa/sustdev/natlinfo/indicators/methodology_sheets/freshwater/biochemical_oxygen_demand.pdf
⁶ http://www.wwf.se/source.php/1183906/wwf_breathless_coastal_seas_engl.pdf