Weathering, agent

This transitory behavior was observed to arise from all the weathering agents considered in this study except ozone. Instead, test coupons exposed to ozone exhibited an initial decline in the crosslink density of the silicone with the formation of surface cracks, which were difficult to distinguish with the naked eye. With continued exposure to ozone, however, the material would begin to crosslink. We proposed that ozone s greatest affinity... 

Corrosion is the process of gradual waste and degradation undergone by most metals and alloys exposed to weathering agents in the environment. The products of the process are chemical compounds in which the corroded metals are combined mainly with oxygen but also with other elements or ions, such as sulfur, carbonate, and sulfate. The composition of the corrosion products is often almost identical to that of the metalliferous ores from which the metals are extracted. 

Because sulfuric acid is a strong acid, it is a more potent weathering agent than carbonic acid. By serving as a source of H (aq), sulfuric acid is transformed into SO Caq). The oxidation of pyrite is responsible for 11% of the sulfete in river water, with pollution now contributing 54%. The latter is largely associated with the burning of sulfur-rich coal. 

Eckhardt, F. E. W. (1985). Solubilisation, transport, and deposition of mineral cations by microorganisms - efficient rock-weathering agents. In The Chemistry of Weathering, ed. J. Drever, Nato Asi Ser C, 149, 161-73. 

The Battle Creek, Wyoming outcrop sample has substantial amounts of vanadyl porphyrins, indicating that petroporphyrins may be preserved even after prolonged exposure to weathering agents. 

Finally, humic and fulvic acids can act as chemical weathering agents by complexing reactions. Early work was carried out on metal oxides and the differential leaching of cations leading to the decomposition of rocks and minerals is frequently cited. Many early experiments on the role of humic and fulvic acids in the breakdown of rocks and minerals are summarized by Ong et... 

Biogeochemical weathering agents of silicate rocks and minerals B = biological O = organic acids FA = fulvic acids HA = humic acids. 

Use Weathering agent in paints and plastics, fixative in perfumes, dyes, resin intermediate, cosmetics, especially suntan preparations, flavoring. 

Continental water contains dissolved species that render it acidic. The acidity comes from a variety of sources from the dissociation of atmospheric C02 in rainwater—and particularly from dissociation of soil-zone C02 (Section 4.4.2)— to form H2C(and natural and anthropogenic sulphur dioxide (S02) to form H2S03 and H2S04 (see Boxes 3.7 3.8). Reaction between a mineral and acidic weathering agents is usually called acid hydrolysis. The weathering of CaCO, demonstrates the chemical principle involved ... 

The effect of temperature is linked to the availability of water. The dry air of hot, arid environments is an ineffective weathering agent. Vegetation and hence soil organic matter are sparse, and this reduces the concentration of organic acids. Moreover, close contact between rock particles and acid is prevented by the lack of water. Short-lived rainfall events may move surface salts into the soil, but the... 

O, A, E General Comments O, A, and E horizons may together be a few cm to 1.2 m thick. Humic and fulvic acids and COj produced in the O and A horizons are the chief weathering agents. The A horizon overall is strongly chemically weathered and so depleted of materials that have been carried downward as suspended or dissolved substances,... 

Metamorphic rocks are either igneous or sedimentary rocks that have been altered by the action of pressure or heat. Marble is an example of a metamorphic rock, being limestone whose crystalline structure has been altered by pressure or heat. Metamorphic rocks tend to be more resistant to weathering agents than the original sedimentary rocks. The almost total loss of pore space and structure reduces the ability of weathering agents to enter the material. 

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