Exploration of the soil physical, chemical, morphological, and solute transport properties of 12 soils in Arkansas

A study was initiated to characterize the soil physiochemical, morphological and solute transport properties of 12 soils found in Arkansas. The soils had varying textures, mineralogies, parent materials, water restricting horizons, landuse/landcovers, and landscape positions. Plots of 100 m2 were delineated in the field and the sod vegetation mowed and killed. KBr was uniformly applied to the soil surface and soil samples for physiochemical and Br were taken to a depth of 1 m in 10 cm increments on a modified grid system from three to five times with increasing amounts of rainfall and time. Significant statistical correlations were found among the soil physical and chemical properties, which led to the development of pedotransfer functions for soil water retention and K_sat. Rapid Br loss occurred at the time of the first sampling and then Br loss rates decreased depending on the soil. After the initial influx of Br into the soil profile, Br moved out of the macropores and into dead end pores, micropores, and the soil matrix. Classical and geostatistical procedures were used to identify the transport mechanisms within the 12 soils and these methods were potentially able to discriminate between preferential flow and classical convective flow. Soils were grouped by several site-specific and Natural Resource Conservation Service (NRCS) methods and the monomolecular equation was fit to mass balance reference depths. The most economical method of grouping soils into transport categories was the NRCS's designation of drainage class. The mechanistic convective dispersive equation (CDE) and the stochastic convective lognormal transfer function (CLT) were used to predict the Br concentration distributions for the 12 field soils at each sampling time. The CDE slightly overpredicted and the CLT slightly underpredicted the transport of Br. Although the model fitting was not perfectly accurate, the two models relatively accurately predictors of Br transport given the wide variation of soil properties within and between the 12 field soils. Final conclusions from this study are that soils can be separated into different solute transport groups from existing data and the CDE and CLT can be used to predict the transport of chemicals through field soils.