Impact of nonuniform treated wastewater application on spatial and temporal variability of soil properties.

摘要

A spatial variability study was performed to obtain the semivariograms, kriged maps of EC and study area was divided into five classes with EC increasing from class Ito V. According to the coefficient of variation (CV), during 2009 and 2010, EC1:1 value for different classes were low to moderately variable at each depth. Semivariogram analysis showed that EC1:1 displayed both short and long range variability. Similarly correlogram analysis produced significant autocorrelation at 25 m lag distances for 0-20 cm depth and 50 m lag distances for 20-40 cm depth during 2009 and 2010. Area coverage of classes I and II were much higher than classes III, IV and V during 2009. However, during 2010 area coverage decreased from 26 % to 14.91% for class II, increased from 12.11 % to 22.97 %, and 10.95 % to 20.55 for classes IV and V respectively. Overall area under EC1:1≥ 4 dS/m increased during 2009. Soil EC map showed EC classes IV (4.1-5 dS/m) and V (> 51 dS/m) were concentrated at northeast and southwest side of the field and classes I and II were at the center of the study plot (Chapter 1).;To determine and quantify the effect of wastewater application on soil thermal properties (thermal conductivity, lambda; thermal diffusivity, alpha; thermal resistivity, R; and volumetric heat capacity, C) core and bulk soil samples were collected from different locations of Dona Ana County, New Mexico. The soil water retention curves were obtained using pressure plate apparatus at 0, -0.3, -1. -3,-5, -10, and -15 bar suctions. Soil thermal properties were determined once a core was equilibrated to an applied pressure using KD2 pro (Decagon Devices, Inc.). Results showed that higher moisture content was observed in the soil irrigated with wastewater for 14 and 8 years than in control at lower pressure. However lower lambda was observed for the soils irrigated with treated wastewater for 8 and 14 years than control might be due to presence of salt layer between the soil particles. Sandy soils showed higher lambda and lower R than the loam and clay texture soils when treated with both tapwater and wastewater. (Abstract shortened by UMI.).;A recent study (Chapter 2) reported higher and lower patches of SAR and other chemical properties in the study site which could impact the hydraulic properties and macroporosity of soil. To the best of our knowledge no information is available on the change in infiltration properties of soil irrigated with treated wastewater in the semi-arid ecosystem. In situ infiltration tests were conducted for an hour at the center of 50 x 50 m sampling grid at pressure heads "psi" = -30, -20, -10, -5, and 0 cm during March-April 2009 using tension infiltrometer. Wooding's equation was used to calculate saturated "KS" and unsaturated hydraulic conductivity "Kpsi" from the steady state infiltration rate. Coefficient of variation (CV) for KS in each of the five KS classes was low to moderate and semivariogram displayed both short and long range variability. Kriged maps of KS showed classes I, II and III were concentrated at northeast and southwest portion of the study site where higher Na+ was detected and classes IV and V were at the center of the study site corresponding to lower Na+ levels. Significantly lower macroporosity was observed in the area where KS was lower and Na+ content was higher Therefore, additional increases in Na+ could further decrease the KS and macroporosity and affect water available for uptake by the native vegetation (Chapter 3).