Retention and Solute Transport Properties in Disturbed and Undisturbed Soil Samples

Abstract

Solute transport parameters can be determined in miscible displacement experiments, usually performed in columns with disturbed (sieved) soil samples. Experiments with undisturbed samples are uncommon, due to the difficulty of taking undisturbed samples at the size required for these experiments. Structural alteration of the disturbed material implies modifications in the pore geometry that determines hydraulic properties, including hydraulic conductivity and retention and properties related to miscible displacement. An existing model for prediction of breakthrough curves based on retention properties was tested using material from a medium-textured Ferralsol, and alterations caused by sample disturbance were investigated. Soil water retention curves and miscible displacement parameters were determined in breakthrough experiments with nitrate salts in columns filled with undisturbed and disturbed soil samples. Data obtained from the undisturbed samples showed a higher dispersion, suggesting homogenization of pore geometry and a reduction in the representative elementary volume by the disaggregation and sieving of the soil material. The transport parameters for nitrate determined in disturbed and undisturbed samples were significantly different and the model was able to simulate the observed breakthrough curves after fitting the pore connectivity parameter.

Dynamics of Ions in Soils Irrigated with Saline Reject

“…It is based on the principle of accommodation of previously treated soil with well-known physical characteristics, followed by the application of the solution to be studied in the soil, with subsequent infiltration, and the collection of the predetermined pore volumes. Importantly, the dimensions of the column are measured in order to calculate the pore volume to be collected (Silva et al, 2012;Matos et al, 2013;Pinho et al, 2014;Silva et al, 2016 , available phosphorus (P), sodium (Na + ) and potassium (K + ) extracted in Mehlich-1 and determined by spectrophotometry visualization (P) and detected by flame photometry (Na + and K + ), the potential acidity (H+Al)-quantified by titration with 0.025 mol L -1 NaOH after extraction with calcium acetate at a concentration of 0.5 mol L -1 with a pH of 7.0 and, soil organic matter (SOM) -as assessed by 0.005 mol L -1 ferrous ammonium sulfate titration after being heated in a uniform plate with 0.02 mol L -1 potassium dichromate (Table 3). -aluminum and, (H+Al) -potential acidity.…”

Reatores em bateladas sequenciais visando nitrificação/desnitrificação simultâneas de esgoto sintético sob baixa relação carbono/nitrogênio

“…A espuma de poliuretano que contém cerca de 90% de vazios (SILVA et al, 2016), tem resultados positivos para imobilização da biomassa aeróbia e anaeróbia (FAZOLO; ZAIAT, 2004), foi utilizada como material suporte em cubos de aproximadamente 1cm de aresta, com peso de 14 gramas e preenchendo cerca de 40% do volume do reator (LIM et al, 2011).…”

Scale effect on hydraulic conductivity and solute transport: Small and large-scale laboratory experiments and field experiments

“…Since the mineralogical and physicochemical characteristics of the soil cannot justify high R values, we argue that the soil structure and other physical characteristics, such as dual-porosity and particle aggregates, are playing an important role in the retention. For example, small pores can favor the formation of immobile domains where mass can temporarily be trapped, decreasing its velocity, in relation to the velocity of the flow, and increasing its R (Dousset et al, 2007;Jarvis, 2007;Silva et al, 2016).…”