Cation leaching

The ability of polyvalent cations leached from the glass to suppress the free-fluoride ion concentration in basalt ground water is difficult to assess. Fluoride definitely enhances leaching and is the primary cause of the high concentrations of dissolved plutonium in the basalt ground-water leachate. Once the plutonium is dissolved, however, it is not possible to determine what fraction is stabilized by fluoride as opposed to other species leached from the glass. 

Damage to epicuticular waxes Altered photosynthesis Increased water loss Accumulation of acidic anions Leaching of ions, sugars, etc. Mineral imbalances Altered metabolism Increased susceptibility to winter freezing injury Death of fine roots Destabilization of trees Reduced water/mineral uptake Reduced water uptake Cations leached below roots Accumulation of acidic anions Altered structure/texture Altered microflora Reduced litter decomposition Altered N transformations Solubilization of metal ions... 

Biological exposure pathway of sulfur movement in soils of forest ecosystems is related to microbial transformation of sulfolipids. Back conversion of sulfate-S into organic matter immobilizes the anion and potentially reduces soil cation leaching. Processes of sulfur mineralization and incorporation proceed rapidly in response to several factors, including temperature, moisture, and exogenous sulfate availability in soils and water. 

A concept of anion mobility may be considered a useful paradigm for explaining the net retention and loss of cations from soils, and thus exposure pathways. This paradigm relies on the simple fact that total cations must balance total anions in soil solution (or any other solution), and, therefore, total cation leaching can be thought of as a function of total anion leaching. The net production of anions within the soil (e.g., by oxidation or hydrolysis reactions) must result in the net production of cations (normally H+), whereas the net retention of anions (by either absorption or biological uptake) must result in the net retention of cations. 

Hartikainen H. 1996. Soil processes and chemical transport. Soil response to acid percolation Acid-base buffering and cation leaching. J Environ Qual 25 638-645. 

Table 7.1 Glucose conversion, selectivity to fructose, percentage of cation leaching and pseudo first-order rate constants for the disappearance of glucose (5 g of glucose in 50 ml of...

Catalyst Glucose conversion (%) Fructose selectivity (%) Cation leaching (%) Glucose disappearance rate (x 104 s-1)... 

Geochemical constraints on acid deposition come from the foram record of a spike in Sr/ Sr across the K/T boundaiy and from base cation leaching at terrestrial K/T sites in eastern Montana. A statistical analysis of the foram data of Martin and Macdougall [1] yields an enhancement in Sr/ Sr of 25 x 10 9x10 We considered two sources of this enhancement Sr leaching from impact ejecta and increased continental weathering due to acid deposition. Impact ejecta with the Sr concentration and ratio of Chiexulub melt rock, 300... 

Cation leaching (Dorn and Krinsley, 1991) from varnish provides materials for redeposition within the weathering rind - thus case hardening the outer shell of rock (Haberland, 1975)... 

Dorn, R.L Krinsley, D.H. (1991) Cation-leaching sites in rock varnish. Geology 19, 1077-1080. 

According to Curtis (1977), the products of chemical weathering which are the soils (or any altered parent-rock regardless of depth) and aqueous solutions form mainly as a result of three processes (1) acid-induced metal-cation leaching (2) hydration and (3) oxidation of ferrous to ferric iron. 

Yet, many forest ecosystems are exposed to acid deposition far exceeding their critical loads. Although these forest ecosystems appear healthy, there may be a sudden detrimental change once the current buffering capacity is depleted. Cation leaching... 

Van Miegroet, H. and D. W. Cole (1984). The impact of nitrification on soil acidification and cation leaching in a red alder ecosystem. /. Environ. Qual. 13, 586-590. 

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