The major proton consumption was through chemical weathering. Weathering rates in the basin and thereby their proton consumption, were deduced from the base cation discharges to the ocean. Each divalent base cation i.
S9 , while silicate weathering uses 2. Literature studies indicate that silicate weathering only contributes ca. Carbonate weathering W Carb was therefore set as the divalent base cation flux at Datong station, after subtracting the contribution from silicate weathering eq.
The flux of monovalent base cations was calculated from the riverine discharge after correction for the contribution from dissolution of evaporates and sea salt deposition, using chloride as tracer.
The remaining important proton depletion mechanism is the protonation of bicarbonate. The amount of protons consumed by protonation of bicarbonate was thus approximated as the difference between external proton input and proton consumption by chemical weathering eq. Basin budget for DIC was obtained through assessing the difference between the fluxes of its input sources and output sinks eq. In these calculations two sources of DIC were considered.
One was atmospheric CO 2 Carbon Atm captured during carbonic weathering. The other was sedimentary paleocarbon in carbonate minerals, mobilized by natural carbonic acid Paleocarbon Nat and anthropogenic strong acids Paleocarbon Ant. Delivered DIC was either discharged directly to the ocean or processed in the river.
The former was calculated based on DIC fluxes at Datong station, while the latter flux was estimated as the difference between DIC input and riverine discharge. There are two pathways for the riverine processed DIC. One is CO 2 outgassing due to protonation of bicarbonate, which was set as equal to the amount of protons consumed by bicarbonate in the proton budget.
The other is fixation into organic carbon through photosynthesis. Most of this terrestrially derived organic carbon will be oxidized to CO 2 again in river, estuary and coastal regions within one year 23 , 24 , 25 , 26 , 27 ; therefore the net assimilation of DIC i. S15 is considered as rather small. Detail rationales for above calculations can be found in the Supplementary Information. How to cite this article : Guo, J. Anthropogenically enhanced chemical weathering and carbon evasion in the Yangtze Basin.
Berner, R. The carbonate-silicate geochemical cycle and its effect on atmospheric carbon dioxide over the past million years. Suchet, P. Global Biogeochem. Cycles 17, , Gaillardet, J. Global silicate weathering and CO2 consumption rates deduced from the chemistry of large rivers.
Influence of acid rain on CO2 consumption by rock weathering: local and global scale. Water Air Soil Pollut. Raymond, P. Long term changes of chemical weathering products in rivers heavily impacted from acid mine drainage: Insights on the impact of coal mining on regional and global carbon and sulfur budgets. Earth Planet. Perrin, A. Impact of nitrogenous fertilizers on carbonate dissolution in small agricultural catchments: Implications for weathering CO2 uptake at regional and global scales.
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Press, Beijing, Vogt, R. Water chemistry in forested acid sensitive sites in sub-tropical Asia receiving acid rain and alkaline dust. Rice, K. Rust forms when the iron or steel in your car reacts with the oxygen in the air to form iron oxide. The resulting red substance can be quite brittle, so much so that you could literally poke a hole in it with your finger. Rocks with iron can go through the same process, too. Minerals with high iron content are affected by oxidation including pyroxene and amphibole.
The oxidation gives these rocks a reddish look, very similar to the patina on a car. Hydration is a type of chemical weathering where water reacts chemically with the rock, modifying its chemical structure. It changes from anhydrite to gypsum. The addition of the water to the anhydrite chemically reacts to create a totally new compound in gypsum.
Hydration has led, in part, to the gypsum sand dunes at White Sands National Monument. Water can add to a material to make a new material, or it can dissolve a material to change it. In hydrolysis , the acid in the water works to dissolve minerals within specific rocks. Examples of hydrolysis in action include turning feldspar into clay and making sodium minerals into saltwater solutions.
Remediation work has since been carried out at the mine and the situation has improved. The hydrolysis of feldspar and other silicate minerals and the oxidation of iron in ferromagnesian silicates all serve to create rocks that are softer and weaker than they were to begin with, and thus more susceptible to mechanical weathering.
Some weathering processes involve the complete dissolution of a mineral. Calcite, for example, will dissolve in weak acid, to produce calcium and bicarbonate ions. The equation is as follows:. Limestone also dissolves at relatively shallow depths underground, forming limestone caves. This is discussed in more detail in Chapter 14, where we look at groundwater.
The main processes of chemical weathering are hydrolysis , oxidation , and dissolution. Complete the following table by indicating which process is primarily responsible for each of the described chemical weathering changes:. Skip to content Chapter 5 Weathering and Soil. Exercise 5. Complete the following table by indicating which process is primarily responsible for each of the described chemical weathering changes: Chemical Change Process?
Both of these acids are capable of attacking certain kinds of rocks in much the way that carbonic acid does. Hydrolysis is a chemical reaction by which a compound reacts with water to form one or more new substances. A number of rock-forming minerals readily undergo hydrolysis, especially in acidic conditions.
For example, the common mineral feldspar will undergo hydrolysis to produce a clay-type mineral known as kaolinite and silicic acid.
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