Persistence and Migration of Alkylphenol Ethoxylate Degradation Products Associated with Land-applied Biosolids

Nonylphenol (NPs) and nonylphenol ethoxylates (NPEOs) enter the environment during the course of land-application of sewage sludge (biosolids). These xenoestrogens have been previously reported in biosolids at concentrations as high as parts per thousand, g/kg (dry weight). Here we examine their residence time and potential for migration during runoff events from pasturelands that received biosolids (anaerobic and aerobic/lime stabilized). Biosolid aggregates (> 0.5 cm) were randomly collected for analysis from these fields at 50 and 175 days after application. Concentrations from each set were compared to the original material. Minimal mineralization was observed 50 days after application, but was substantially greater at 175 days for NPs and NPEOs. Surface runoff created by means of applying artificial rainfall to the biosolids treated and control pasture-plots were compared. Greater levels (P < 0.05) of NPs and NPEOs were observed for the treated plots (range 1.69 to 5.35 μg/L). A stronger correlation (R =0.562) between NP concentrations and PtOC (particle organic carbon) was also observed compared to DOC (dissolved organic carbon) (R=0.125) and TOC (total organic carbon) (R=0.252), indicating that NPs were more associated with runoff solids. Although not conclusive, during the first 50-days after application grazing animals have the greatest potential to be exposed to NPs and NPEOs with burdens continuing at a minimum up to six months thereafter. (U.S. regulations restrict grazing up to 30 days after application.) It also appears that these xenoestrogens have the potential to migrate with runoff from biosolid-applied fields during rainfall events.