What is Acid Leaching 5 and what is Acid Leaching

Leaching. Leaching refers to a kind of action that dissolves certain mineral salts or organic substances in the upper soil layer through natural infiltration rainwater or artificial irrigation, and moves them to the lower soil layer. In rainy areas, if the ground is poorly drained, rainwater will seep downward.

Since the rainwater absorbs carbon dioxide in the air, it has been slightly acidic, seeps into the soil, and then mixes with various acids produced by the decomposition of organic matter or minerals, its acidity is stronger, so the calcareous matter and other soluble salts in the soil can be dissolved and washed away, and some iron oxides and clays that are difficult to remove are alluvial in the B layer of the soil profile. In places where there is sufficient rainfall, leaching often leaves a more acidic and barren soil, which is called acidic soil. These include laterites, tropicalredsoils, redearths, graybrownsoils, podsols and tundrasoils.

Leaching is one of the most important weathering effects on the surface. Deposits can sometimes be formed. For example, the original surface rock, whose composition was silicate, after leaching, sometimes contains a large amount of hydrous iron oxide in the residual soil, which becomes an iron ore deposit; If it contains a large amount of alumina with a large amount of hydrous, it becomes an aluminium deposit, also known as bauxite deposits, which are collectively referred to as residualconcentration deposits.

In limestone areas, after long-term leaching, a large number of rock layers can disappear, and sometimes aluminium deposits remain.

Leaching includes acidic leaching, alkaline leaching, and neutral leaching. Acid leaching refers to the leaching of deferred iron and aluminum, and bleached soil is a typical soil formed by acid leaching. In addition, there are neutral leaching and alkaline leaching, the former is desilicated and aluminum-rich, and the representative soil is red soil; The latter refers to the removal of salt-based ions such as calcium and magnesium.

Leaching refers to the effect of dissolving certain mineral salts or organic substances in the upper soil layer and transferring them to the lower soil layer through natural infiltration or artificial irrigation of rainwater. In rainy areas, such as poor ground drainage, rainwater infiltrates more downward, and because rainwater absorbs carbon dioxide in the air, it has become slightly acidic; After infiltrating into the soil, it is mixed with various acids produced by the decomposition of organic matter or minerals, which is more acidic, and can dissolve and transfer the calcareous matter and other soluble salts in the soil, and some iron oxides and clays that are difficult to move are alluvial in the B layer of the soil profile. In places where there is sufficient rainfall, leaching often leaves behind strong acidic and barren soils, called acidic soils, including laterites, tropical redsoils, redearths, graybrownsoils, podsol, and tundrasoils.

Leaching is an important type of weathering on the earth's surface, which sometimes results in the formation of mineral deposits. If the main component of the original surface rock is silicate, after leaching, if the residual soil contains more hydrous iron oxide, iron ore deposits will be formed. If it contains more alumina with more hydrous content, it becomes an aluminum deposit, also known as bauxite. This type of deposit is collectively known as residualconcentration deposits.

In limestone areas, long-term leaching can cause a large number of rock formations to disappear, and sometimes to accumulate aluminium deposits.

Drenching is also known as elution. An important operational step in the ion exchange extraction and purification process, the purpose of which is to leach the metal (such as uranium) that has been adsorbed on the resin (support resin or saturated resin) from the resin phase into the aqueous solution. For the sulfuric acid leaching solution (or slurry) adsorption process of uranium, the commonly used eluents are acidic nitrate solution (e.g., Hno3+NH4NO3) or acidic chloride solution (e.g., H2SO4+NaCl).

For the adsorption process of uranium carbonate leaching solution (or slurry), it is advisable to use NaCl solution with a small amount of NaCO3 or NaHCO3 as an eluent. Elution is also a commonly used method for column chromatography. In ion-exchange chromatography, an appropriate solution is used as the mobile phase to desorb the ions adsorbed by the resin at a certain flow rate.

Those with small affinity will flow out first, and those with large affinity will flow out later.

Soil action is an aspect of soil formation. It refers to the effect of dissolving, hydration, hydrolysis, carbonation and other actions that cause some components in the soil surface layer to enter the water and be taken away.

According to its leaching strength, it can be divided into K and Na leaching, CA and Mg leaching, cohesis leaching and Fe and Al leaching. With the leaching process, the soil layer is gradually acidified. For example, in the upper part of the soil profile in humid areas, due to the long-term leaching of water from the surface downward, the soluble substances and fine soil particles in the upper soil layer are leached, and the soil layer with lighter soil color, coarser texture, increased acidity and lower fertility is gradually formed.

The leaching layer, also known as layer A, can be improved by tillage, fertilization, especially the application of organic fertilizer and clayey mud fertilizer.

Leaching: The action by which soil material moves from one layer of soil to another in a suspended or dissolved state.

Leaching: The action of soluble substances in the soil moving downward with the soil solution.

Acid rain is a direct result of air pollution. Industrial combustion discharges a large amount of sulfur dioxide and other gases into the atmosphere, resulting in the enrichment of sulfur dioxide in the atmosphere in local areas, which is dissolved in water to form sulfurous acid in the process of water condensation, and then produces sulfuric acid through the catalytic action of some pollutants, which falls with rain to form acid rain. In addition to sulfuric acid, there are nitric acid formed from NOx (mainly NO2), hydrochloric acid, carbonic acid, etc.

Acid rain is extremely harmful to people's health. Acidic air, which increases respiratory diseases. In the rainy season of 1975, the acid rain in the Kanto region of Japan, although it was a drizzle, caused unbearable pain to the eyes of tens of thousands of people.

Acid rain acidifies lakes, rivers and surface waters, seriously affecting the growth and survival of aquatic organisms. More than 20,000 of Sweden's more than 90,000 lakes have been harmed by acid rain, and 4,000 lakes have become fish-dead due to acidification. Canada's approximately 60,000 lakes are in danger of becoming "deserts" of water.

At the same time, acid rain destroys forests and vegetation and destroys soil fertility. On the one hand, acid rain leachates nutrients such as calcium, magnesium and potassium in the soil, resulting in soil acidification and barrenness, affecting plant growth, on the other hand, most soil microorganisms, especially nitrogen-fixing bacteria, grow in alkaline, neutral and slightly acidic soils, the addition of acid rain causes confusion in the soil microbial community, and affects the circulation of nutrients, seriously harming the growth of crops and other plants. In 1981, someone in the United States Senate testified that acid rain cost crops $1 billion and forestry billions of dollars.

On 8 March 1984, the Washington-based Worldwatch Institute published a study stating that the worldwide deforestation caused by acid rain was estimated to be worth billions of dollars in terms of timber loss. In our country, reports about acid rain have also been reported frequently. In mid-June 1982, an acid rain fell in Suzhou, causing all the watermelon seedlings planted in the suburbs to rot.

In addition, acid rain harms the city's buildings, harming machines, bridges, places of interest, and art. Ancient temples in Athens, Greece, and stone carvings in the Ruhr region of Germany have been corroded beyond recognition by acid rain. The white marble stone carvings in the Forbidden City in Beijing have a history of hundreds of years, and from the ** taken in 1925, the pattern of the relief is still very clear, but to this day, it has been blurred by the corrosion of acidic air and rain.

In general, the soil is acidic ......