Saturday, 15 July 2006

Pedotransfer Functions for Mineralization and Retention of Waste Waters.

Francisco Bautista, Depto de Ecología, FMVZ. Univ Autónoma de Yucatán, km 15.5 carretera Mérida-Xmatkuil, Mérida, 97000, Mexico and Yameli Aguilar, Univ Autónoma de Yucatán, km 15.5 carretera Mérida-Xmatkuil, Mérida, 97000, Mexico.

Soils can function as reactors in which waste water can be naturally purified, depending on the soil's physical and chemical properties. A soil's buffering power, and thus the possibility of successful purification interaction, depends both on waste characteristics and the properties of each soil, such as Organic Matter (OM) content, Cation Exchange Capacity (CEC) and Clay content (CLY). Pedotransference functions allow estimation of a certain phenomenon based on a soil's physical and chemical properties (Imnhoff et al., 2004). Based on the above, the study aim was generation of pedotransference functions to estimate Dissolved Organic Matter (DOM) retention and mineralization of Porcine Waste Water (PWW) in karst zone soils. Soil profiles were described for seven geomorphological landscapes in the state of Yucatan, Mexico. Epidon samples were taken and their texture, OM content, CEC and exchangeable cations analyzed (Okalebo et al., 1993). To measure DOM retention, soil columns were built using 10.5 cm wide polyvinyl chloride (PVC) pipe cut into 30 cm sections and each section filled with 20 cm of dry, screened (4mm mesh) soil. Three volumes of PWW (395 mL + 785 mL +1180 mL) were applied to each soil column. Quantification of DOM concentration, measured as Chemical Oxygen Demand (COD), was done for the lixiviate. The DOM mineralization was measured by applying 250 mL PWW to 500g of soil in pots and measuring CO2 evolution and Potential Anaerobic Nitrogen Mineralization (PANM) (Anderson & Ingram, 1993). Experimental design was completely random and included four replicates. Multiple regressions were done with STATGRAPHICS Plus 4.1 using soil clay content, OM content and CEC as independent variables, and DOM mineralization and retention as dependent variables. A multicriteria analysis was done to evaluate the effects of PWW with DOM retention and CO2 evolution as environmental variables, PANM as fertility criterion and CEC as degradation criterion (Antoine et al., 1996). The pedotransference function for DOM retention was calculated with the equation: DOM retention = 47.1 + 2.8*CEC - 0.85*CLY - 3.7*OM, with an r2= 0.64. The pedotransference equation CO2 evolution = 115.4 + 5.8*OM + 0.65*CEC - 1.07*CLY, with an r2= 0.86, showed OM content to have the most influence on CO2 evolution. The PANM pedotransference equation, PANM = -8.98012 + 3.53429*OM + 1.12484*CLY - 2.20188*CEC, showed soil OM content to have the most weight in the model. Use of the pedotransference functions applied only to the soil units and study zone, as is the case in other studies. However, once the parcel map was made and soil units identified it was shown that these functions can be very useful in making decisions about PWW application because they allow estimation of application volumes. The studied properties are also easy to measure and the technical analyses are conventional. The studied soils can be grouped into three classes according to the measured properties: 1) Cambisols and Lixisols, with higher PWW receptive aptitude; 2) Leptisols and Luvisols, with intermediate aptitude; 3) Regosols and Vertisols, at greater risk of degradation from agricultural use of PWW. Clay relative content (%), OM content (%) and CEC influence DOM retention and mineralization processes and can be used to calculate pedotransference functions aimed at choosing soils for PWW application.

Back to 2.5B Interactions between Clays and Organic Matter and Their Impact on Sorption and Availability of Organic Compounds in Soil Environments - Poster
Back to WCSS

Back to The 18th World Congress of Soil Science (July 9-15, 2006)