Enhanced techniques for determining changes to soils receiving wastewater irrigation for over forty years

It is the goal of the present study to use the framework set out by the emerging hydropedology concepts and techniques to better understand a real world practice, wastewater irrigation. The objectives are twofold, (1) to evaluate and modify selected hydraulic conductivity measurement techniques to enhance their reliability and accuracy; and (2) to comprehensively evaluate the changes in soil properties after receiving over forty years of wastewater irrigation, including the use of improved methodologies addressed in the first objective.; The tension infiltrometer is a standard tool for measuring near-saturated soil hydraulic properties. We examined the dynamics of the supply tension at the interface between the tension infiltrometer and the measured soil using a pressure transducer under different soil conditions and raised some cautions needed for proper use of this standard device. Infiltration experiments were conducted on a tension table, a large sand column, and in two field soils of contrasting textures and structures to test the performance of the standard two-piece infiltrometer. Results showed that during high flow rates (>200 cm3 min-1) the tension at the infiltrometer/soil interface started to deviate by as much as 15 mm from the desired tension. However, during field experiments the high flow rates were not experienced, and thus no deviation was observed between the pre-set desired tension and the actual measured tension at the infiltrometer/soil interface. To alleviate the problem of tension deviation under high flow, the water supply tubing and fitting diameters of the standard infiltrometer were successfully increased to yield a higher flow rate (∼300-400 cm3 min-1 ) without elevated tensions.; The constant head method for determining saturated hydraulic conductivity is a classical laboratory method for measuring the soil's ability to conduct water. One error commonly associated with this technique occurs when there is flow between the edge of the soil sample and the cylindrical ring holding the soil sample. We developed a method to minimize the effects of this artificial boundary flow. A new simple permeameter was constructed to separate flow between the outer and inner portions of the soil core. Intact core samples from the surface and subsurface Hagerstown silt loam series were analyzed to quantify the edge flow phenomenon. Outer saturated hydraulic conductivity (associated with possible edge flow) was found to be significantly higher than the inner saturated hydraulic conductivity (p = 0.038, n = 153). The A-horizon surface samples were found to have significant edge flow (n = 110, p = 0.049), whereas the subsurface soil samples did not experience significant edge flow because of possible clay expansion. In addition, brilliant blue dye was used to visually confirm the edge flow phenomenon. This study also investigated the length of saturation time needed to saturate the soil cores, and found that the heavier textured cores should be saturated for at least a week. A long term experiment was conducted for eight days to determine if and when the outflow volume reaches steady-state. The results indicated that, although the core appeared to be at steady-state during short time periods, true steady-state conditions were not achieved until approximately five days into the experiment. Furthermore, the new permeameter's results were compared with in situ hydraulic conductivity methods. Taken altogether, these results suggest that the hydraulic conductivity values from the inner portion of the soil core are more comparable to the in situ tension and double ring infiltrometer conductivity values observed in the field.; For over 40 years, The Pennsylvania State University (PSU) has irrigated its wastewater onto both cropped and forested lands. While this method of wastewater disposal has gained popularity in water-deficit regions, it is not widely used in areas that have a surplus of water. Despite local weather co...