Does anyone know the process by which acid rain is formed?

When sulfur- and nitrogen-containing substances burn, they produce sulfur dioxide/nitrogen oxides, which spread into the atmosphere. In clouds, these substances dissolve in water droplets to form acids; when the water droplets grow large enough, it rains

Sulfur dioxide emitted from coal combustion in industrial production and domestic use, as well as nitrogen oxides released from petroleum combustion and vehicle exhaust, go through a \"rain formation process within clouds\" – that is, water vapor condenses on condensation nuclei such as sulfate and nitrate ions, leading to liquid-phase oxidation reactions that result in sulfuric acid raindrops and nitric acid raindrops； After going through the \"downward washing process,\" acid-containing raindrops continuously merge and absorb other acid-containing raindrops and acidic gases as they fall, forming larger raindrops that eventually reach the ground and constitute acid rain.

The main causes of acid rain are related to pollutants such as sulfur dioxide and nitrogen oxides released into the atmosphere from the burning of coal and oil, as well as industrial activities. In the atmosphere, sulfur dioxide and ammonia oxides are converted into sulfuric acid and nitric acid respectively through chemical reactions; these acids then end up in rainwater or snowmelt, increasing their acidity. At the same time, the formation of acid rain is also related to many other alkaline substances in the atmosphere, such as calcium oxide in fly ash and calcium carbonate in soil; these alkaline substances can undergo neutralization reactions with acids. The acidity of acid rain is actually the result of acid-base reactions between cations and anions in the atmosphere, involving complex atmospheric chemical and physical processes.

Sulfur dioxide, an exhaust gas produced industrially, rises into the air where it reacts with moisture in the air to form sulfurous acid; when the temperature is appropriate, sulfuric acid is then formed. Other gases may also cause rainwater to become acidic

Acid rain is rainwater with a pH value of less than 5.6. It forms when acidic gases present in the atmosphere are carried down to the ground by rainfall. Acidic gases fall into two main categories: sulfur oxides and nitrogen oxides; therefore, acid rain can be of sulfuric acid type or nitric acid type. The main source of sulfur dioxide (SO2) in the air is the burning of sulfur-containing fuels. It is estimated that 70% of SO2 in the atmosphere comes from industrial coal combustion, 12% from industrial fuel use, and the remainder from domestic coal burning and other sources. SO2 gas that enters the atmosphere is partially oxidized by oxygen in the air, etc., into sulfur trioxide (SO3), under the catalysis of certain transition metal elements combined with nitrogen oxides or suspended particles; this results in the formation of sulfuric acid (H2SO4) when precipitation occurs, leading to acid rain. The high-temperature combustion of fuel is the main source of nitrogen oxides in the atmosphere. It mainly comes from automobile exhaust and the products of burning fuel for heating and power generation. At temperatures of 1200°C or higher (temperatures that can be reached inside internal combustion engines exceed 2000°C), N2 (nitrogen) and O2 (oxygen) in the air can produce detectable amounts of NO (nitric oxide). This latter substance slowly reacts with oxygen to form NO2 (nitrogen dioxide), which, when it falls as precipitation, turns into HNO3 (nitric acid), thereby causing acid rain.

Water vapor in the air combines with acidic gases in the air. It’s raining. This is the simplest

Sulfuric acid and nitric acid in acid rain are formed from sulfur dioxide and nitrogen oxides emitted by human activities, with SO2 being one of the main substances that contribute to the formation of acid rain. S02 and N0x can be locally emitted or transported from distant sources. Acid rain is the product of a comprehensive process in which atmospheric pollutants are emitted, transported, transformed, condensed into clouds, and precipitate as rain under certain meteorological conditions. S02 released into the atmosphere from the combustion of coal and oil, as well as from metal smelting, is converted into sulfuric acid through gas-phase or liquid-phase oxidation reactions. This chemical process can be simplified as follows: Gas-phase reactions: 2S02 + O2 → 2S03; S03 + H2O → H2SO4. Liquid-phase reactions: S02 + H2O → H2S03; 2H2S03 + O2 → 2H2SO4. It was previously believed that sulfur oxides entering the atmosphere needed to react with at least 200 water molecules in order to form acid rain. In recent years, experiments conducted by scientists at the University of Manchester in the UK have shown that acid rain can be formed simply through a reaction with 12 water molecules. This shows that if sulfur pollution is not reduced, acid rain will still form in dry atmospheres. High-temperature combustion produces nitric oxide, which is converted into nitrogen dioxide in large part once released into the atmosphere; upon contact with water, it forms nitric acid and nitrous acid. This chemical process can be roughly represented as follows: 2NO + O2 → 2NO2; 2NO2 + H2O → HNO3 + HNO2. Human activities and natural processes also introduce many gaseous or solid substances into the atmosphere, which in turn affect the formation of acid rain. Atmospheric particulates such as Fe, Mn, Cu, Mg, V, etc., act as catalysts for acid-forming reactions. Ozone and hydrogen peroxide, produced by atmospheric photochemical reactions, are oxidants that oxidize SO2.

It should be gases such as nitrogen dioxide, sulfur dioxide, and carbon dioxide that reach the broader atmosphere, dissolve in water vapor to form acidic water, and then reach the ground through rainfall

Acidic gases dissolve in rainwater, reducing its pH value.

It refers to precipitation with a pH value of less than 5.65. Acid rain in our country is primarily caused by the extensive burning of coal with high sulfur content; in addition, exhaust gases emitted by various motor vehicles are also a significant factor contributing to acid rain. In recent years, some regions in our country have become areas prone to acid rain, and the extent and severity of acid rain pollution have drawn considerable attention. What is an acid? Pure water is neutral and has no taste ； Lemonade and orange juice are sour; vinegar has an even stronger sour taste. All of them are weak acids ； Baking soda water has a slightly astringent alkalinity, while sodium hydroxide solution is very astringent and has a strong alkaline taste; sodium hydroxide is an alkali, whereas baking soda, although alkaline, belongs to the category of salts. Scientists have discovered that the intensity of acidity is related to the concentration of hydrogen ions in an aqueous solution ； And the alkaline taste is related to the concentration of hydroxide ions in the aqueous solution ； Then a parameter was established: the negative of the logarithm of the hydrogen ion concentration, called pH value. Therefore, the pH value of pure water (distilled water) is 7 ； The greater the acidity, the lower the pH value ； The greater the alkalinity, the higher the pH value. (The pH value is generally between 0 and 14.) Unpolluted rain and snow are neutral, with a pH value close to 7 ； When it is saturated with carbon dioxide in the atmosphere, it becomes slightly acidic (water and carbon dioxide combine to form carbonic acid), with a pH of 5.65. Rain with a pH value of less than 5.65 is called acid rain ； Snow with a pH value of less than 5.65 is called acidic snow ； The fog that prevails at high altitudes or on mountains (such as Emei Mountain) is called acid fog when its pH value is less than 5.65. 　　There are several tools that can be used to test the acidity or alkalinity of water: litmus solution, phenolphthalein solution, pH test strips (which provide high accuracy for measuring pH values), and pH meters (which allow for even more precise measurement of pH values).