Excess Isoprene: A Curse for Air Quality

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Context (TWC): Due to global warming, plants like oaks and poplars will emit more isoprene, which will worsen the air quality.

Isoprene

Isoprene is a colourless, volatile liquid hydrocarbon.
It is the most abundant non-methane VOC emitted into the atmosphere.
Sources:
1. Biogenic Sources: Most isoprene is produced by plants and by some algae and bacteria. It is also produced in small amounts by humans and other animals.
2. Anthropogenic sources: It is also released by activities like the combustion of fossil fuels, production of petroleum products and synthetic rubber, etc.
Uses: Isoprene is used in natural and synthetic rubber, adhesives, pharmaceuticals, and fragrances.
It is the main component of natural rubber.

Isoprene from plants is the second-highest emitted hydrocarbon on Earth, after methane emissions from human activity.

VOCs are organic compounds with a high vapour pressure at room temperature.
This means that they readily evaporate into the air at room temperature.
They are found in paints, solvents, cleaning products, air fresheners, fuels, etc.
They can also be emitted from natural sources, such as plants and trees.
Concern: They can cause air pollution (by contributing to the formation of ground-level ozone, smog, etc.), which leads to various health and environmental problems.

Pests and Disease Resistance: Isoprene defends plants against pests and diseases. It can be toxic to some insects and attract beneficial insects that prey on pests.
Heat Tolerance: It can protect plants from high heat by safeguarding their photosynthetic systems.
Atmospheric chemistry: It helps to remove specific pollutants from the air. It reacts with chemicals in the atmosphere to create secondary organic aerosols, which act as cloud condensation nuclei.

Ground-level ozone formation: Ground-level ozone forms when sunlight reacts with nitrogen oxides and VOCs. It leads to health problems, crop damage, and reduced visibility.
Secondary organic aerosol formation: Isoprene also reacts with other atmospheric chemicals to form secondary organic aerosols, which reduces air quality and visibility.
Climate change: Increased isoprene emissions raise tropospheric ozone and methane levels, which are significant greenhouse gases. Thus contributing to global warming.

Global warming has two implications for isoprene emissions from plants:
1. Increasing carbon dioxide in the atmosphere slows the rate of isoprene emissions.
2. Increasing temperatures accelerate the rate of isoprene emissions.
However, the temperature effect trumps the carbon dioxide effect.