Industrial and Municipal Byproducts Effects on Leachable Arsenic from Phosphorus Amended Orchard Soil.

There are concerns of arsenic leaching from orchard soils with a history of lead arsenate use when phosphorus is applied. Research has shown that reagent grade calcium and iron salts sequester arsenic. The objective of this study was to determine the effectiveness of calcium, iron and organic byproducts on leachable arsenic from an orchard soil amended with phosphorus. One rate (17.5 g) of phosphorus as potassium phosphate and two rates of each byproduct (20 and 40 g) were mixed with 800 g of an orchard soil. Treatments were replicated three times and de-ionized water was added to achieve field capacity.  The amended soil was incubated for four weeks. After four weeks, the amended soil was placed into 45×8 cm polypropylene tubes and leached three times at three weeks interval with 300 ml de-ionized water. Bed ash, byproducts and phosphorus application reduced pH and increased electrical conductivity in the leachate.  At the low rate, calcium bed ash and iron water treatment residual were more effective in reducing arsenic in the leachate compared to the organic byproduct. At the higher rate, all three byproducts reduced arsenic in the leachate.  Even though, the arsenic concentrations were reduced with increased byproduct application rate, the arsenic concentrations in the third leachate (9 weeks) were much higher than the10 µg/L recommended for drinking water.