Modeling of soil phosphorus sorption and control of phosphorus pollution with acid mine drainage floc

• Main Author: Sekhon, Bharpoor Singh
• Format: Dissertation
• Language: English
• Subjects: agriculture, soil science
• ISBN: 9780549751298; 0549751297

The study was conducted to investigate and model phosphorus sorption in soils and to study the effectiveness of acid mine drainage (AMD) floc in controlling phosphorus (P) loss to surface runoff from soils. Phosphorus sorption capacity of surface and subsurface horizons of four benchmark soil series - Berks, Huntington, Lindside, and Monongahela - of West Virginia was measured. The soils of these four series were loaded with increasing amounts of P up to 60% of their P retention capacity. Though amount of P released to the solution increased with increase in degree of P saturation, most of the soils did not release considerable amounts of P. Phosphorus sorption capacity of surface and subsurface horizons of these soil series was predicted by using the standard characterization data on the amounts of Fe and Al oxides, pH, organic carbon, clay content, exchangeable Al and Mn, extractable acidity, and basic cations. Various statistical modeling techniques involving variable selection through stepwise ordinary least-squares regression (OLSR), and the principal components regression (PCR) were used for individual soils and for all soils in common. Models developed using the PCR technique performed the best. Use of AMD floc, an Fe and Al rich waste product generated after neutralization of AMD with chemicals like ammonium hydroxide, calcium hydroxide, and sodium hydroxide, in attenuating P in runoff or in soils was examined. AMD floc attenuated more inositol hexaphosphate (IHP)-P, which is a major organic-P form in poultry and swine manure, than it attenuated inorganic-P. Higher retention of IHP-P suggested that soils could receive more organic P than inorganic P. AMD floc did not catalyze the hydrolysis of IHP-P appreciably. Citrate and oxalate, companion anions of inorganic and IHP-P in manures, competed with both inorganic- and IHP-P for sorption sites onto AMD flocs only at low pH. Sorption of inorganic P was more affected by citrate and oxalate than the IHP-P sorption. Citrate impaired P sorption more than did oxalate, but with increase in pH (range 4-9) citrate competed less with P than did oxalate. Incorporation of AMD floc into soils lowered soil-test P, and degree of P saturation levels significantly in four different soils, and increased their P retention capacity. Results of the present study indicate that P retention capacity of the soils can be predicted from the data collected routinely as a part of soil survey or classification program, and AMD floc can be effectively used in controlling loss of P from soil to the water bodies.