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Impact of Soil Physicochemical and Biological Reactions on Transport of Nutrients and Pollutants in the Critical Zone

Authored by: Jon Chorover

Handbook of Soil Sciences Resource Management and Environmental Impacts

Print publication date:  November  2011
Online publication date:  November  2011

Print ISBN: 9781439803073
eBook ISBN: 9781439803080
Adobe ISBN:

10.1201/b11268-12

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Abstract

The fate of nutrients and pollutants in soil and other porous geo-media in the Earth’s surface depends on feedbacks and intimate couplings among physical, chemical, and biological processes. At small distances in this realm are the molecular-scale interactions that occur when nutrients and pollutants are introduced to a rich soil geochemistry of lithogenic solutes, organics, and particle surfaces, including those that are formed from organic and inorganic weathering processes. A premise of this chapter is that the fate and transport of nutrients and pollutants in the environment is highly dependent on the structure, dynamics and interactions of organic and inorganic secondary products of biogeochemical weathering. If that premise is correct, then once introduced to a soil environment, the fate of nutrients and pollutants must depend on the dynamic behavior of these secondary products. Since aqueous geochemical conditions in soils change on a hydrologic event basis as well as along fluid flow paths, one expects that the metastability and reaction kinetics of these secondary products and co-associated nutrients and pollutants will likewise behave dynamically in time and space. Physicochemical processes that occur along flow paths in soil include (1) aqueous complexation, (2) redox, (3) sorption and flocculation, (4) nucleation and growth of inorganic and organic weathering products, (5) hetero-aggregation to form micro-aggregates, and (6) pore structure formation and associated limitations on advection and diffusion. These nano- to microscale interactions are then superimposed in the field by consolidation of hetero-aggregates into a macro-structured porous media with emergent properties of pedon- to field-scale heterogeneity and preferential fluid flow.

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