Impacts of Holding Time on the Analysis of Nonylphenol in Soil and Biosolids Samples

Data Quality, Management and Review
Poster Presentation

Prepared by , L. Zintek, G. Schupp

Contact Information:; 312-353-9771


Annually, over 3 million dry tons of treated sewage sludge (or biosolids) are applied on agricultural lands in the U.S. Nonylphenol is a degradation product of nonylphenol ethoxylate, a surfactant used in industrial detergents and other products, and often found in biosolids. While nonylphenol is aerobically degradable, it is persistent in aquatic environments, moderately bioaccumulative, and extremely toxic. To evaluate land application of anaerobically digested biosolids at agronomic levels, a pilot-scale field research project was conducted. Nonylphenol-containing biosolids were applied to a rye grass and fescue field in outdoor conditions for a year, and samples were collected periodically over the year and placed into storage for 11 to 18 months prior to analysis. Nonylphenol was observed in samples from the liquid and solid biosolids applications, as well as biosolids only controls, throughout the outdoor study period.

Holding time is an important issue in analytical evaluation of chemical constituents. The integrity of samples and the stability of chemicals in those samples may depend on storage conditions, storage time, chemical volatility, matrix interactions, biodegradation, and other factors. To assess the usability of the nonylphenol data acquired from the land application of biosolids field study, a long-term holding time study was conducted to examine the influence of holding time on stability of nonylphenol concentrations when refrigerated (<8oC). Samples were randomly selected from the outdoor sample set, including samples from all application types, and re-analyzed 8 to 14 months after the first analysis. From exploratory data analysis, the concentrations in solid application and biosolids-only samples appeared to be stable throughout the holding period. However, the concentrations in liquid application samples, which displayed much lower concentrations, appeared to change during the holding period. A more thorough probabilistic analysis is being developed to incorporate the influence of variability and uncertainty on holding time analysis interpretations.