Chemical weathering indices applied to soils developed on old lake sediments in a semi-arid region of Turkey

Abstract

Climate is a major influence on weathering processes affecting soil parent materials. Important contributors to soil formation in arid and semi-arid climatic zones are the diurnal cycles of solar heating and cooling that cause mechanical or physical disintegration of rock or parent materials, and wind-blown sands that score and abrade exposed rock surfaces. By using the Soil Taxonomy classification system, the initial aim of this study was to carry out a pedological evaluation for four soil profiles, classified as Xeric Haplocalcid and Xeric Haplocambid, formed on different parent materials (limestone, marl and old alluvial deposits) under the same conditions, including topography and vegetation, in a semiarid region. The second stage was the exploration of the similarities and differences in the classifications resulting from either the pedogenic processes, or from other factors, by determining the degree of soil weathering using geochemical data. To achieve this, soil samples were collected from the horizons to investigate their mineralogical, geochemical and physiochemical properties. The study also considered other features, such as the pedogenic evolution of soils, through the use of weathering indices, namely the Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), Base/R2O3 Ratio, Weathering Index of Parker (WIP) and Plagioclase Index of Alteration (PIA). The results clearly showed that soil development at the Altınova State Farm at Konya in the Central Anatolia region of Turkey is due to slow pr ogressive weathering. For this case, the main indicators are secondary calcium carbonate illuviation and weak structural development with a weathering ratio of silicon to aluminium greater than two in all profiles.

Habitat specificity and co-occurrence network of bacterial communities in the Xincuntun Cave, Guilin, Guangxi

“…此外, 化学风化指数如Mg/Si、Ca/Si也是显著影响 新村屯洞穴微生物群落结构的重要因素. 化学风化通 常被用来衡量风化壳、土壤/古土壤和陆源碎屑沉积物 或岩石等的化学风化强度 [59] , Mg、Ca元素在风化作用 中易被溶出, 而Si则相对稳定, 因此, Mg/Si、Ca/Si比值 越大, 表明化学风化程度越剧烈 [60] . 微生物在岩石风化 以及成土作用中发挥着重要作用 [61] , 在对岩石进行风 化的过程中, 微生物分泌代谢产物如酸性物质促使矿 物分解 [62] , 或者通过电子传递对矿物中的变价元素进 行氧化/还原 .…”

Chemical weathering of the middle Vistula and Żuławy (Vistula delta) alluvial soils

“…Compared to the soils developed from old lake sediments containing carbonates in Turkey (Özaytekin et al, 2012;Tunçay et al, 2019) and from limestones (Dengiz et al, 2013), the studied soils showed similar values of weathering indices. However, the intensity of weathering in the cross-section of soil profiles from the area of Turkey was more diverse, and the values of chemical weathering indices decreased or increased with depth.…”

Soil weathering dynamics and erosion in a dry oceanic area of the southern hemisphere (Otago, New Zealand)

“…However, the role of tors in the context of providing fresh mineral materials is still in question. In regions having a dry climate with substantial diurnal changes in temperature can cause mechanical or physical disintegration of rocks or abrasion of rock surfaces 52 , which is the case in Otago 53 . The weathering indices show that the reference sites closest to the bedrock outcrops have the lowest soil weathering degree.…”