i) Geological Matters- These are basically suspended dust particles and primarily constitute the cores fraction of particulates. It consists of oxides of metals such as Al, Si, Ca, Ti, Fe- Heavy metals are also emitted into the atmosphere by industrial processes such as steel making, mining, smelting etc.
ii) Sulphates- Primarily ammonium sulphates ammonium bi sulphates and sulphuric acid constitute chemical species of secondary particulates. These compounds are water soluble and primarily found in fine particle range. So2 which is released from power plant & industrial processes are the primary precursor to sulphate formation.
iii) Nitrates- These are basically secondary particles which are formed by the reaction of Nox with ammonia gas. Nitrates are also primarily in fine particle range.
iv) Elemental Carbon- This is pure black carbon also known as soot which is formed through pyrolysis of organic carbon in the combustion of fossil fuels. It is black and thus absorbs light significantly affecting visibility.
v) Organic Carbon- It is all known carbon & none light absorbing carbon. It includes hundreds of different compound containing greater than 20 carbon molecules. Organic carbon mostly belonging to fine particulate fraction is both released directly from sources such as motor vehicles & is formed through atmosphere reaction.
vi) Liquid Water- Water in the atmosphere gets absorbed to nitrates, sulphates and other compounds particularly when relative humidity is greater than 70%.
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