Weathering rate influences

The influence that variations of temperature and levels of atmospheric CO2 and O2 have on chemical weathering are more subtle. Temperature appears to have a direct effect on weathering rate (White and Blum, 1995). The silica concentration of rivers (Meybeck, 1979, 1987) and the alkalinity of ground waters in carbonate terrains (Harmon et al., 1975) are both positively correlated with temperature variations. It is not clear, however, whether temperature-related variations in weathering rates are largely due to variations in vegetational activity that parallel temperature variations. 

Influence of Surface Area, Surface Characteristics, and Solution Composition on Feldspar Weathering Rates... 

Large differences in the proportion of silicate bedrock in catchments presented only weakly influenced the sihcate-weathering rate for the whole basin (see silicates bar in Fig. 13). In the Ticino basin, mostly covered with silicate bedrock, the rate increased to 100 mmol m y (40 g m y )- This value was in the range... 

Lake level could also influence silica levels. For example, the decline in lake level resulted in a large loss of surface area and decreased the amount of contact between lake water and sandy littoral areas that contain weath-erable silicate minerals. Rates of weathering are usually enhanced by acidification and would help to explain the interbasin differences observed at pH 4.7. However, weathering rates of LRL sediment are unknown (see Sediment Processes section). In addition, although the differences between the basins were significant, they were small (0.01-0.03 mg of Si02 per liter) and may be accounted for by small differences in hydrological factors. 

Velbel, M. A. (1986). Influence of surface area, surface characteristics, and solution composition on feldspar weathering rates. ACS Symp. Ser. 323, 615-634. 

In the present chapter, I will discuss the potential of EMF to influence weathering rates of soil minerals, and review experiments where the effects of EMF on dissolution of minerals have been investigated in axenic cultures, pot cultures and field experiments. I will then discuss the influence of the nutrient status of the trees on weathering induced by EMF and, finally, to what extent this process may influence the overall cycling of elements in forest ecosystems. 

Hodson M. E., Eangan S. J., and Wilson M. J. (1999) The influence of soil age on calculated mineral weathering rates. Appl. Geochem. 14, 387-394. 

Velbel M. A. (1990) Influence of temperature and mineral surface characteristics on feldspar weathering rates in natural and artificial systems a first approximation. Water Resour. Res. 26(12), 3049-3053. 

Wright R. F. (1987) Influence of acid rain on weathering rates. In Physical and Chemical Weathering in Geochemical... 

The marine strontium isotope record is the proxy record most commonly used to constrain the geologic history of chemical weathering. However, in recent years it has been widely criticized as a proxy indicator of past silicate weathering rates. The osmium isotope record is analogous to the strontium record in many respects, and can help to constrain interpretations of the marine strontium isotope record. In this section the geochemical factors that influence the osmium and strontium isotope compositions of seawater are reviewed, and the structure of these two records of Cenozoic ocean chemistry is discussed. 

Weathering, and subsequent deterioration of rock exposed to the environment, are slow processes. Weathering rates are influenced by temperature, the presence of moisture, the presence of organic acids, and the carbon dioxide partial pressure in the solution in contact with the rock surface. In contemporary industrial societies, natural weathering processes are accelerated by elevated pollutant concentrations. Acidic pollutants in particular, in both air and rainfall, are recognized as serious hazards to carbonate rock used in commerce and cultural resources... 

The last-mentioned factor influencing weathering rates of minerals in soils (see list above), efficiency of removal of soluble weathering products, warrants further comment. In confined soil environments, dissolved silica and base cations accumulate from weathering reactions. So, for example, the neoformation of kaolinite from smectite ... 

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