Abstract

Quantification of soil plasticity is usually based on Atterberg limits or indices, which are then used for engineering and agricultural purposes on clay soils. Because these limits/indices are seldom analyzed during routine soil surveys, they are sometimes estimated from available soil properties using pedotransfer functions (PTFs). Main aim of this study was to test if two robust PTFs, previously created by other authors for other soils/areas, may be used for predicting plasticity of typical clay soils on fluvial deposits in Croatia. We analyzed mineralogy, plasticity, and related physicochemical properties of four representative soil profiles along Sava and Drava, two longest Croatian rivers. Particle size distribution patterns pointed to more uniform sedimentation along Sava, compared to Drava. Also, more clay was found within Sava profiles. Soil texture was finer farther away from the sources of both rivers. Soil cation exchange capacity (CEC) was almost fully positively correlated to clay content. On the other hand, C_org content showed no correlation to CEC. This is attributed to the significant presence of smectite across all studied soils. Clay was recognized as the main factor influencing soil plasticity. When compared to the measured values, the predicted values of plasticity index and liquid limit were heavily underestimated. Hence, region-specific PTFs should be developed for more accurate prediction of plasticity in these soils. According to the WRB-2015, the soils were classified as Eutric Reductigleyic Stagnic Gleysols (Clayic, Humic, Protovertic). Because soils were not dry during field description, shrink-swell cracks were not prominent, and therefore soils were not classified as Vertisols. We suggest that field criteria for classification of Vertisols should not depend on actual soil moisture. Instead, plastic limits/indices could be used.

中文翻译：

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克罗地亚两条主要河流沿线的一些典型粘土的可塑性，矿物学和WRB分类

摘要

土壤可塑性的量化通常基于Atterberg极限或指数，然后将其用于黏土的工程和农业目的。由于在常规土壤调查过程中很少分析这些限度/指标，因此有时会使用pedotransfer函数（PTF）根据可用的土壤性质估算它们。这项研究的主要目的是测试以前由其他作者为其他土壤/地区创建的两种坚固的PTF是否可用于预测克罗地亚河床沉积物上典型粘土的可塑性。我们分析了两条最长的克罗地亚河流萨瓦河和德拉瓦河沿线的四种代表性土壤剖面的矿物学，可塑性和相关的理化特性。与德拉瓦河相比，粒度分布模式表明沿萨瓦河的沉积更加均匀。另外，在萨瓦剖面中发现了更多的粘土。远离两条河源的土壤质地都更好。土壤阳离子交换容量（CEC）与粘土含量几乎完全正相关。另一方面，C_组织含量与CEC无相关性。这归因于在所有研究过的土壤中均存在蒙皂石。粘土被认为是影响土壤可塑性的主要因素。当与测量值比较时，可塑性指数和液体极限的预测值被大大低估了。因此，应开发针对特定区域的PTF，以更准确地预测这些土壤中的可塑性。根据WRB-2015，土壤被分类为Eutric Reductigleyic Stagnic Gleysols（粘土，腐殖质，质子化）。由于在田间描述过程中土壤并不干燥，因此膨胀裂缝并不明显，因此土壤未归类为Vertisols。我们建议对Vertisols进行分类的现场标准不应取决于实际的土壤湿度。相反，可以使用塑料限位/指示。