Applied Soil Chemistry. Группа авторов

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Название Applied Soil Chemistry
Автор произведения Группа авторов
Жанр Химия
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Издательство Химия
Год выпуска 0
isbn 9781119711506



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Sustainability, 9, 4, 578, 2017.

      * Corresponding author: [email protected]

      A Brief Insight on Factors Controlling Rate of Chemical Weathering of Minerals Existing in Soil

      Tejaswini Sahoo1, Rashmirekha Tripathy1, Jagannath Panda1,3, Madhuri Hembram1, Saraswati Soren1, Deepak Kumar Senapati1, C.K. Rath1, Sunil Kumar Sahoo2 and Rojalin Sahu1*

       1School of Applied Sciences, Kalinga Institute of Industrial Technology, Deemed to be University, Bhubaneswar, India

       2Health Physics Division, BARC, Mumbai, India

       3CSIR-IMMT, Bhubaneswar, India

       Abstract

      Mineral weathering relative to soil has two parts: weathering happened previously where hard rocks have been broken down into clay which ultimately forms soil, loams, and unconsolidated sands both chemically and physically and other is soil and mineral weathering happening currently which acts as vital source of crop nutrients. This chapter discusses background of chemical weathering of minerals, sequence of weathering of minerals from soil, mainly throwing light on the factors which controls the rate of chemical weathering like temperature and time factor, biotic process, oxidation, reduction, water, leaching, acidity, and many more.

      Keywords: Chemical weathering, time factor, temperature factor, leaching, oxidation, reduction

      Physical weathering was referred as disintegration, whereas chemical weathering referred to as decomposition. As already discussed, in case of physical weathering, large masses of rock get converted into elastic or unconsolidated state, owing to the hydrospheric and atmospheric factors. Polynov et al., in the year 1937 [5–7], states that weathering is a cyclic, complicated procedure which involves breakdown of solid structure of rock and production of enhanced interfacial interaction between the rock and nearby surrounding.

      By mechanical conditions, in case of disintegration or physical weathering process, rocks break down into smaller form which retain both its composition as well its originality. For example, even though basalt gets broken down via physical weathering or mechanical means into its smaller form, it could be identified as basalt. Physical weathering of rock occurs either in place or by the media like wind, gravity displacement at steep slopes, moving water and glacial ice which carries the rock and then grind it. In place physical weathering is driven by five factors as stated by Rieche et al. in the year 1950 [8–10]. The factors include unloading, thermal expansion, crystal growth, colloid plucking, and pressure and abrasion due to animals and plants. When there is reduction in confining pressure due to joints, cracks, erosion, and uplift, unloading causes rock masses expansion. According to Polynov et al., in the year 1937 [5], thermal contraction and expansion is vital factor, but as per Origgs et al. and Blaclrwelder et al. [11, 12], it is comparatively not important. Crystal growth causes production of prying action on minerals and rocks. This involves activity due to frost and also up to some extent formation of crystals due to chemical weathering, for example, as per Humbert and Marshall, in the year 1943 [13–15], quartz physical weathering occurred due to films of iron oxides. Colloid plucking refers to the physical damage occurred owing to the reduction of colloidal matter, resulting in peeling of the rock surface. According to Kellog et al., in the year 1943 [16–18], destruction of rocks occurs due to overgrowth of roots of the plants.

       2.1.1 Weathering Similar to Hydrothermal and Diuretic Alteration of Minerals

      Depending on the factors initiating the chemical weathering process, weathering of minerals depends on their stability. Owing to the stability some gets weathered slower and some faster in comparison to other minerals. The process of weathering of minerals depending upon their stability is occurring in a sequence, often referred as weathering sequence. Establishment of sequence of weathering process occurs on the basis of certain criteria, comparative persistence with depth of formation, age of formation, size of particle, intensity factors of weathering, and geographical factors.

       2.2.1 Heavy Minerals

      According to Pettijohn