Fate of Certain Alkylphenol Ethoxylates in Soils Amended with Alkaline-Stabilized Biosolids.

Application of biosolids to soil is practiced for various beneficial purposes but also serves to transfer many contaminants to soils. Current understanding of the behavior of many contaminants is limited while a great void exists regarding others. Alkylphenol ethoxylates (APEO) are organic contaminants found to accumulate in biosolids which is often land-applied as a soil conditioner and organic fertilizer. They are surfactants widely used in industrial, commercial and household applications including detergents and have been identified as endocrine disruptors (ED). These ED compounds are non-polar and typically partition into soil organic matter. The fate and transport of selected APEOs -- Nonylphenol (NP), Octylphenol (OP), Nonylphenol Ethoxylates (NPEO) -- and Bisphenol A in soils ranging from upland clayey to coastal sandy soils amended with alkaline-stabilized biosolids were investigated in soil columns and batch experiments. Alkaline stabilization treatment process adds lime and/or other alkaline materials to sewage sludge thus altering the sludge matrix. Since land-application of biosolids is an established practice, 18 long-term cultivated fields were studied to assess the fate of the target compounds in the years since they received biosolids. Biosolids field application rates were between 13 and 269 Mg ha^-1 (6 and 120 wet ton/acre). The role of soil organic matter, colloidal movement and alkaline nature of the biosolids were assessed in the fate and transport of these contaminants. Results of transport/leaching experiments in soil columns, sorption studies and long-term field investigations will be discussed.