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A pore‐scale model based on measured particle size distributions has been used to quantify the changes in pore space geometry of packed soil columns resulting from a dilution in electrolyte concentration from 500 to 1 mmol l?1 NaCl during leaching. This was applied to examine the effects of particle release and re‐deposition on pore structure and hydraulic properties. Two different soils, an agricultural soil and a mining residue, were investigated with respect to the change in hydraulic properties. The mining residue was much more affected by this process with the water saturated hydraulic conductivity decreasing to 0·4% of the initial value and the air‐entry value changing from 20 to 50 cm. For agricultural soil, there was little detectable shift in the water retention curve but the saturated hydraulic conductivity decreased to 8·5% of the initial value. This was attributed to localized pore clogging (similar to a surface seal) affecting hydraulic conductivity, but not the microscopically measured pore‐size distribution or water retention. We modelled the soil structure at the pore scale to explain the different responses of the two soils to the experimental conditions. The size of the pores was determined as a function of deposited clay particles. The modal pore size of the agricultural soil as indicated by the constant water retention curve was 45 µm and was not affected by the leaching process. In the case of the mining residue, the mode changed from 75 to 45 µm. This reduction of pore size corresponds to an increase of capillary forces that is related to the measured shift of the water retention curve. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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T. Mosekiemang O. Dikinya 《International Journal of Environmental Science and Technology》2012,9(1):129-134
This paper presents an evaluation of different chelating agents for their effectiveness in removing Cu, Co and Zn in three distinctly different types of sludge-amended soils. Soil types (Luvisol, Arenosol and Vertisol) were each mixed with an anaerobically digested sludge at a 1:1 ratio followed by leaching with three types of chelating agents, namely: ethylenediamine tetra acetic acid, nitrilotriacetic acid and acetic acid. Aqua regia method was used to quantify pseudo total metal before and after treatment. Generally, chelating agents can be out competed by soil colloids in attracting cations. The efficiency of chelating agents was found to follow this order ethylenediamine tetra acetic acid?<?nitrilotriacetic?=?acetic acid in all the three metals, with ethylenediamine tetra acetic acid being the most effective chelating agent. More heavy metals were removed in Luvisol and Arenosol than in Vertisol implying that soils rich in clay fraction retain more cations than soils with minimal clay fraction. Similarly, copper responded positively to chelation than zinc and cobalt in Luvisols and Arenosols, although the results were not conclusive for Vertisols. 相似文献
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Comparative analysis of heavy metal concentration in secondary treated wastewater irrigated soils cultivated by different crops 总被引：4，自引：4，他引：0
O. Dikinya Ph.D. O. Areola Ph.D. 《International Journal of Environmental Science and Technology》2010,7(2):337-346
The use of treated urban wastewater for irrigation is a relatively recent innovation in Botswana and knowledge is still limited on its impact on soil heavy metal levels. The aim of this study is to analyze and compare heavy metal concentration in secondary wastewater irrigated soils being cultivated to different crops: olive, maize, spinach and tomato in the Glen Valley near Gaborone City, Botswana. The studied crop plots have been cultivated continuously under treated wastewater irrigation for at least 3 years. Most crop farms have sandy loam, loamy sand soils. Based on food and agriculture organization, heavy metal threshold values for crop production have been studied. Results showed that the wastewater irrigated soils in the Glen Valley have higher cadmium, nickel and copper than desirable levels, while the levels of mercury, lead and zinc are lower than the maximum threshold values recommended for crop production. The control sites show that the soils are naturally high in some of these heavy metals (e.g copper, zinc, nickel) and that crop cultivation under wastewater irrigation has actually lowered the heavy metal content. Comparing between the crops, mercury and cadmium levels are highest in soils under maize and decline linearly from maize to spinach to olive to tomato and control site. By contrast, concentrations of the other metals are at their lowest in maize and then increase from maize to spinach to olive to tomato and to control site. 相似文献
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