Chemistry /chemical weathering

Fig. 9-3 Conceptual model to describe the interaction between chemical weathering of bedrock and down-slope transport of solid erosion products. It is assumed that chemical weathering is required to generate loose solid erosion products of the bedrock. Solid curve portrays a hypothetical relationship between soil thickness and rate of chemical weathering of bedrock. Dotted lines correspond to different potential transport capacities. Low potential transport capacity is expected on a flat terrain, whereas high transport is expected on steep terrain. For moderate capacity, C and F are equilibrium points. (Modified with permission from R. F. Stallard, River chemistry, geology, geomorphology, and soils in the Amazon and Orinoco basins. In J. I. Drever, ed. (1985), "The Chemistry of Weathering," D. Reidel Publishing Co., Dordrecht, The Netherlands.)...

Dalai TK, Krishnaswami S, Sarin MM (2002) Major ion chemistry in the headwaters of the Yamuna river system chemical weathering, its temperature dependence and C02 consumption in the Himalaya. Geochim Cosmochim Acta 66(19) 3397-3416... 

The concept of disorder and solubility windows is discussed in G. Sposito, Chemical models of weathering in soils, pp. 1-18 in The Chemistry of Weathering, ed. by J. I. Drever, D. Reidel, Dordrecht, The Netherlands, 1985. 

The on-line implementation of environmental processes in the GEM model allows running in global uniform, global variable, and limited area configurations, allowing for multiscale chemical weather forecasting (CWF) modelling. This approach provides access to all required dynamics and physics fields for chemistry at every time step. The on-line implementation of chemistry and aerosol processes... 

Kaminski JW, Neary L, Struzewska J, McConnell JC, Lupu A, Jarosz J, Toyota K, Gong SL, Cote J, Liu X, Chance K, Richter A (2008) GEM-AQ, an on-line global multiscale chemical weather modelling system model description and evaluation of gas phase chemistry processes. Atmos Chem Phys 8 3255-3281. doi 10.5194/acp-8-3255-2008 Kuo HL (1974) Eurther studies on the parametrization of the influence of cumulus convection on largescale flow. J Atmos Sci 31 1232-1240... 

The Atmospheric Chemistry Transport modelling system used is based on the off-line coupled CAMx and HIRLAM models has been developed to simulate particulate and gas-phase air pollution on different scales. It has been used to simulate short and longterm releases of different chemical species and air pollution episodes. At present it is run in a pre-operational mode 4 times per day based on 3D meteorological fields produced by the HIRLAM NWP model. Currently this modelling system is setup to perform chemical weather forecasts for a series of chemical species (such as O3, NO, NO2, CO and SO2) and forecasted 2D fields at surface are available for each model as well as an ensemble of models (based on 12 European regional air quality models). The simulated output is publicly available and it is placed at the ECMWF website (http //gems.ecmwf.int/d/products/raq/forecasts/) of the EC FP6 GEMS project. 

Attempts to model chemical weathering of catchments have used a variety of approaches and were originally designed to understand acidification processes. The BIRKENES code (Christophersen et al., 1982) was one of the first developed to model catchment stream chemistry. It used cation-anion charge balance, a gibbsite equilibrium solubility control for aluminum concentrations, a Gapon ion exchange for metals sorption, and rates for sulfate adsorption/ desorption in a two-reservoir model. The model was calibrated by input mass fluxes and output mass fluxes for the Birkenes catchment in Norway to provide the water flux information and to fit empirical parameters. 

Bricker O. P., Godfrey A. E., and Cleaves E. T. (1968) Mineral-water interactions during the chemical weathering of silicates. In Trace Inorganics in Water, Advances in Chemistry Series 73 (ed. R. E. Gould). American Chemical Society, Washington, DC, pp. 128-142. 

Chemical weathering and lithologic controls of water chemistry in a high-elevation river system Clark s fork of the Yellowstone River, Wyoming and Montana. Water Resour. Res. 35, 1643-1656. 

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. 

In this chapter we discuss the rates of adsorption, paying special attention to those few cases where information on the rate of specific adsorption (reaction of an adsorbate in the adsorption layer) is available. Furthermore, we elaborate on the chemical processes involved in the dissolution of minerals and concentrate on the dissolution of oxides, silicates, and carbonates, which play an enormous rx)le in the chemical weathering and erosion. We try to demonstrate that in most cases the rate-determining step in the dissolution is a chemical reaction at the surface of the mineral. Thus we have here an excellent example of the relationship between surface stracture and reactivity. Surface chemistry plays an equally important role in the formation of the solid phase (precipitation, nucleation, and crystal growth). Nature s selectivity is reflected in the creation of a crystal and its growth. 

Feist WC and Hon DNS (1984) Chemistry of weathering and protection. In Rowell RM (ed), The chemistry of solid wood, ACS S)Tnposium Series 207. American Chemical Society, Washington DC... 

For a variety of practical reasons, great effort has been expended in recent years to understand controls on and to predict rates of chemical weathering in soils. A principle reason has been a need to assess the effects of acid precipitation on the chemistry of soils and thus on the health of affected plants and trees. Soil acidification from acid precipitation has been a serious problem in industrialized areas where soils are thin or absent and bedrock and resultant soils lack carbonate or reactive silicate minerals (cf. Likens et al. 1977 Berner and Berner 1996). Soil acidification in such areas has caused the acidification of adjacent streams and even underlying groundwaters (cf. Bottcher et al. 1985 Hansen and Postma 1995). 

Cronan, C. S. 1985. Chemical weathering and solution chemistry in acid forest soils Differential influence of soil type, biotic processes and H" deposition. In The... 

Sposito, G. 1985. Chemical models of weathering in soils. In The chemistry of weathering, ed J. 1. Drever, pp. 1-18. NATO ASl Scr. C Mathematical Physical Sciences. Boston D. Reidel Publ. Co. 

In environmental chemistry we can include such topics as chemical weathering, pollution, effects of fertilizers on the land and in the water etc. Some attention to colloidal chemistry and surface chemistry, nuclear chemistry will help to keep student interested in chemistry. 

---