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Reference Terms
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Tropospheric ozone

Ozone (O3) is a key constituent of the troposphere. Photochemical and chemical reactions involving it drive many of the chemical processes that occur in the atmosphere by day and by night. At abnormally high concentrations brought about by man's activities (largely the combustion of fossil fuel), it is a pollutant, a constituent of smog. Many highly energetic reactions produce it, ranging from combustion to photocopying. Often laser printers will have a smell of ozone, which in high concentrations is toxic. Ozone is a powerful oxidizing agent readily reacting with other chemical compounds to make many possibly toxic oxides. The majority of tropospheric ozone formation occurs when nitrogen oxides (NOx), carbon monoxide (CO) and volatile organic compounds (VOCs), such as xylene, react in the atmosphere in the presence of sunlight. NOx and VOCs are called ozone precursors. Motor vehicle exhaust, industrial emissions, and chemical solvents are the major anthropogenic sources of these chemicals.

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September 12, 2025

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Researchers in Germany and Australia have created a simple but powerful tool to detect nanoplastics—tiny, invisible particles that can slip through skin and even the blood-brain barrier. Using an "optical sieve" test strip viewed under a regular ...
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New research has revealed that East Antarctica’s vast and icy interior is heating up faster than its coasts, fueled by warm air carried from the Southern Indian Ocean. Using 30 years of weather station data, scientists uncovered a hidden climate ...
Cambridge scientists discovered that thin, weak zones in Earth’s plates helped spread Iceland’s mantle plume across the North Atlantic, explaining why volcanic activity once spanned thousands of kilometers. These ancient scars not only shaped ...
Every year, Panama’s Pacific coast benefits from powerful seasonal winds that drive nutrient-rich waters to the surface, sustaining fisheries and protecting coral reefs. But in 2025, for the first time in at least four decades, this crucial ...
A sweeping new study reveals that humanity has already pushed 60% of Earth’s land outside its safe biosphere zone, with 38% in a high-risk state. By analyzing centuries of data, researchers mapped how human demands on biomass—from farming to ...

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