Experimental evaluation of the classical and alternative consolidation theories in predicting the volumetric change of contaminated and non-contaminated soil

Several regions in Brazil and the world suffer from the presence of collapsible soils. The development of theories for understanding the phenomenon is significant because the increase of water content is associated with several reasons (e.g., precipitation, rupture of sewage, and water systems). Although some theories explain the behavior of various types of soils, they fail to explain collapsible and structured soils. In this research, an alternative interpretation of the consolidation theory is verified and calibrated for collapsible soil. The alternative model was applied to experimental data from a latosol from southeastern Brazil, and comparisons with the classical theory showed a difference in the saturated hydraulic conductivity of around 100 times. The observation showed promising results compared with the saturated hydraulic conductivity of the field (Guelph Permeameter). Furthermore, consolidation tests verified the collapse potential, the variation of consolidation coefficient and saturated hydraulic conductivity, and the total settlement prevision due to the presence of bleach and washing powder.

Variability of topsoil hydraulic conductivity along the hillslope transects delineated in four areas strongly affected by soil erosion

Soil hydraulic conductivities of topsoils were studied at 5 points of the hillslope transects delineated at 4 geomorphologically diverse areas, where the original soil types (Chernozem, Luvisol and two Cambisols) were due to erosion transformed into different soil unites. Hydraulic conductivities of saturated soils and for a pressure head of –2 cm were measured directly in the field using a Guelph permeameter (K s,GP ) and mini disk tension infiltrometer (K h=– 2 ,MDI ), and in the laboratory using a multistep outflow method (K s,MSO , K h= – 2 ,MSO ). While K s,GP ≈ K s,MSO in the Chernozem and Cambisol (sandy loam) regions, and K s,GP < K s,MSO in the Luvisol and Cambisol (loam) regions. The K s values obtained using different methods showed different trends along the hillslope transects. The K h= – 2 values obtained using different methods showed similar trends along the transects in the Chernozem and Luvisol regions. These trends could be explained by the position within the transects (i.e., different stages of erosion/accumulation processes). No relationships were found between the K h=– 2 values in the Cambisol regions. The pressure head at an inflection point of the a soil-water retention curve was the main parameter, which appeared to associate (negative correlation) with K h=– 2 and K s,MSO in the Chernozem and Luvisol regions.

Peculiarities of Infiltration Measurements in Water-Repellent Forest Soil

The paper deals with measurements of water infiltration carried out on a well-developed forest floor formed by needle-leaf litter of Norway spruce. Three field methods (tension disk permeameter, single-ring infiltrometer and Guelph permeameter) were used to determine the soil hydraulic conductivity. The results were strongly influenced by the water repellency at the interface between the O- and A-horizons. This interface was severely water repellent during the hot and dry summer season, regardless of the generally humid mountain climate of the High Tatras foothill. The single-ring method paradoxically provided lower hydraulic conductivity (3.2 × 10−4 ± 1.3 × 10−4) compared to the tension disk permeameter (8.5 × 10−4 ± 3.3 × 10−4) due to the presence of the water-repellent O/A-interface. This effect was also observed with the Guelph permeameter method, which gave the lowest value (5.6 × 10−5 ± 4.3 × 10−5). Abrupt retardation of infiltration on the water-repellent interface may generate shallow subsurface runoff (as was proved by the irrigation experiment) or litter splash during extreme rainfall events and promote water flow to deeper soil horizons through preferential pathways. The observed effects of the forest floor on rainfall infiltration will depend on the seasonal variability of soil water repellency. Although the forest floor is a source of hydrophobic substances that cause water repellency at the O/A-interface and can trigger runoff generation, at the same time its cohesive duff layer protects the forest soil from erosion.

Agregação de solo em pastagens sob diferentes índices de qualidade e sua influência na infiltração de água

In Brazil, extensive livestock farming predominates, often in soils with low agricultural potential and susceptible to degradation, mainly in terms of physical aspects and water infiltration. Thus, this work aims to analyze the impact caused by the succession process in soil of different pasture areas, with an emphasis on their physical quality and physical-hydric characteristics, relating them to the role played by naturally observed ecosystem services. For this, 4 grazing areas were selected, in Red Ultisol, under different levels of natural succession: grazing in good visual conditions (PB); pasture under low scrub (CB); pasture under high scrub (CA); pasture under “capoeirão” (CAO), in the Ribeirão José Pereira microbasin (Itajubá - MG). The physical attributes were determined: soil density, porosity, size and stability of aggregates, as well as their classification as to the formation path. The infiltration analysis was carried out with the aid of a Guelph permeameter and the resistance to mechanical penetration of the soil with an impact penetrometer. For analysis of the results, analysis of variance and Tukey test at 5%, Pearson's correlation and multivariate statistics of main components were used. The natural succession in abandoned pastures improves the physical quality of the soil, with the production of larger, more stable aggregates and of biogenic formation over time. The areas could be classified according to their quality, in the following increasing order: PB < CB < CA < CAO, which respected the action of natural succession and, therefore, of ecosystem services.

INFILTRASI DAN PERMEABILITAS PADA TANAH REKLAMASI TAMBANG EMAS

ABSTRACT Infiltration and permeability are soil parameters that can be used to describe the extent of land damage caused by the mining process. In accordance with Law No. 4.of 2009 on Mineral and Coal Mining, that reclaiming mining land is obligatory for every company that manages it. This study aims to determine the rate of infiltration and permeability on the reclaimed gold mined land. The research was conducted at the gold mining location of Bakan and Lanut. Infiltration measurements were carried out on straight line transect along the foot slope to the top slope. Measurements were made at two meter distance in 5 cm depth along the transect line direction using the Guelph Permeameter. Hydraulic conductivity was calculated from infiltration data. This research revealed that reclamation has positive effect in increasing of infiltration rate and permeability. Crop dan root growth should have contributed in increasing soil organic matter, root and microbial activities, which leads to improve soil texture and soil structure.Keywords: infiltration, permeability, reclaimed

Variación espacio-temporal de los procesos hidrológicos del suelo en viñedos con elevadas pendientes (Valle del Ruwer-Mosela, Alemania)

The vineyards of Ruwer-Mosel valley (Germany) cultivated on steep slopes showed a high spatial and temporal variability of hydrological dynamics. Forty two experiments were carried out using a Guelph permeameter in old and young vines to measure the infiltration rates, the hydraulic conductivity and the soil matrix flux potential. The essays were performed before (spring-summer) and after (autumn) the harvest with dry soil conditions and without soil tillage signals, and with humid soil conditions, signals of soil farming (wheel traffic and footprints) and a decrease of organic matter, respectively. In general, the results of the young vineyards were higher than the values of the old vineyards. Furthermore, all the rates increased after the harvest. For the young vineyards, the most elevated values were registered on the middle slope (398.5 mm h-1 infiltration rate, 89.2 mm h-1 hydraulic conductivity and 62.8 mm2 h-1 soil matrix flux potential). For its part, a decrease of the infiltration from the upper slope to the foot slope was observed (from 42.5 to 16.8 mm h-1). Hydraulic conductivity and soil matrix flux potential showed the same hydro-dynamic: from 13.2 to 5.4 mm h-1 and from 5.5 to 2.5 mm2 h-1, respectively. Finally, it was observed that the most correlated factor with these hydrological processes was the soil moisture content and the soil tillage practices.

Research on the infiltration processes of lawn soils of the Babao River in the Qilian Mountain

Using a Guelph Permeameter, the soil water infiltration processes were analyzed in the Babao River of the Qilian Mountain in China. The results showed that the average soil initial infiltration and the steady infiltration rates in the upstream reaches of the Babao River are 1.93 and 0.99 cm/min, whereas those of the middle area are 0.48 cm/min and 0.21 cm/min, respectively. The infiltration processes can be divided into three stages: the rapidly changing stage (0–10 min), the slowly changing stage (10–30 min) and the stabilization stage (after 30 min). We used field data collected from lawn soils and evaluated the performances of the infiltration models of Philip, Kostiakov and Horton with the sum of squared error, the root mean square error, the coefficient of determination, the mean error, the model efficiency and Willmott's index of agreement. The results indicated that the Kostiakov model was most suitable for studying the infiltration process in the alpine lawn soils.