Abstract
The intensification of agricultural production to meet the growing demand for agricultural commodities is increasing the use of chemicals. The ability of soils to transport dissolved chemicals depends on both the soil’s texture and structure. Assessment of the transport of dissolved chemicals (solutes) through soils is performed using breakthrough curves (BTCs) where the application of a solute at one site and its appearance over time at another are recorded. Obtaining BTCs from laboratory studies is extremely expensive and time- and labour-consuming. Visible–near-infrared (vis–NIR) spectroscopy is well recognized for its measurement speed and for its low data acquisition cost and can be used for quantitative estimation of basic soil properties such as clay and organic matter. In this study, for the first time ever, vis–NIR spectroscopy was used to predict dissolved chemical breakthrough curves obtained from tritium transport experiments on a large variety of intact soil columns. Averaged across the field, BTCs were estimated with a high degree of accuracy. So, with vis-NIR spectroscopy, the mass transport of dissolved chemicals can be measured, paving the way for next-generation measurements and monitoring of dissolved chemical transport by spectroscopy.
Highlights
Understanding the leaching of dissolved chemicals to groundwater and being able to measure and model it is important for health and the environment
Breakthrough curves (BTCs) obtained from column experiments in the laboratory are usually used for deriving estimates of the parameters for solute transport models
There have been only few attempts to develop pedotransfer functions to estimate the parameters for solute transport models using basic soil properties[13,15]
Summary
Flow and transport processes are often studied in the laboratory on soil columns using BTCs. For the Estrup field with a gradient in OC (0.018–0.084 kg kg−1) and a clay content similar to Faardrup, the BTCs were characterized by a lower degree of preferential transport than the Faardrup soils. Soils with high clay content can contain cracks and fissures due to wetting-drying and freeze-thaw cycles which can result in heterogeneity of soil structure and preferential transport[24]. Besides clay content[25,26], organic carbon content[27], water saturation[28] and bulk density[29] influence the degree of preferential transport through soils. The presence of macropores in soils with a high clay content (i.e., less conductive soil matrix) directs water and solutes towards the macropores, resulting in preferential flow. On the other hand, promotes soil aggregation and increases homogeneity in the soil structure, reducing preferential transport through soils[27], which was represented by the BTCs of the Estrup soil
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