Field dissipation of 4-nonylphenol, 4-t-octylphenol, triclosan and bisphenol A following land application of biosolids.

The persistence of contaminants entering the environment through land application of biosolids needs to be understood to assess the potential risks associated. This study used two biosolids treatments to examine the dissipation of four organic compounds: 4-nonylphenol, 4-t-octylphenol, bisphenol A and triclosan, under field conditions in South Australia. The pattern of dissipation was assessed to determine if a first-order or a biphasic model better described the data. The field dissipation data was compared to previously obtained laboratory degradation data. The concentrations of 4-nonylphenol, 4-t-octylphenol and bisphenol A decreased during the field study, whereas the concentration of triclosan showed no marked decrease. The time taken for 50% of the initial concentration of the compounds in the two biosolids to dissipate (DT50), based on a first-order model, was 257 and 248 d for 4-nonylphenol, 231 and 75 d for 4-t-octylphenol and 289 and 43 d for bisphenol A. These field DT50 values were 10- to 20-times longer for 4-nonylphenol and 4-t-octylphenol and 2.5-times longer for bisphenol A than DT50 values determined in the laboratory. A DT50 value could not be determined for triclosan as this compound showed no marked decrease in concentration. The biphasic model provided a significantly improved fit to the 4-t-octylphenol data in both biosolids treatments, however, for 4-nonylphenol and bisphenol A it only improved the fit for one treatment. This study shows that the use of laboratory experiments to predict field persistence of compounds in biosolids amended soils may greatly overestimate degradation rates and inaccurately predict patterns of dissipation.

Degradation of 4-nonylphenol, 4-t-octylphenol, bisphenol A and triclosan following biosolids addition to soil under laboratory conditions.

Land application of biosolids is common practice in many countries, however, there are some potential risks associated with the presence of contaminants within the biosolids. This laboratory study examined the degradation of four commonly found organic compounds, 4-nonylphenol, 4-t-octylphenol, bisphenol A, and triclosan, in soil following the addition of two biosolids over 32 weeks. The pattern of degradation was assessed to determine if it followed a standard first-order decay model or if a biphasic model with a degrading and a recalcitrant fraction better described the data. The time taken for the initial concentrations to decrease by 50% (DT50), based on a first-order model, was 12-25 d for 4-nonylphenol, 10-14 d for 4-t-octylphenol, 18-102 d for bisphenol A, and 73-301 d for triclosan. For 4-nonylphenol, bisphenol A and triclosan, the biphasic model fitted the degradation data better than the first-order model, indicating the presence of a degrading fraction and a non-degrading recalcitrant fraction. The recalcitrant fraction for these three compounds at the completion of the 32 week experiment was 17-21%, 24-42%, and 30-51% of the initial concentrations, respectively. For 4-t-octylphenol, the first-order model was sufficient in explaining the degradation data, indicating that no recalcitrant fraction was present. This study showed that biphasic degradation occurred for some organic compounds in biosolids amended soil and that the use of standard first-order degradation models may underestimate the persistence of some organic compounds following land application of biosolids.

Aquatic hazard assessment for pharmaceuticals, personal care products, and endocrine-disrupting compounds from biosolids-amended land.

Reuse of biosolids on agricultural land is a common practice. Following the application of biosolids to land, contaminants in the biosolids have the potential to migrate offsite via surface runoff and/or leaching and pose a hazard to aquatic ecosystems. The aim of this screening-level assessment study was to determine the relative hazard posed to aquatic ecosystems by pharmaceuticals, personal care products, and endocrine-disrupting compounds (EDCs) that have been detected and quantified in biosolids. This involved estimating maximum possible runoff water concentrations of compounds, using an equilibrium partitioning approach and then comparing these with the lowest available aquatic toxicity data, using the hazard quotient (HQ) approach. A total of 45 pharmaceuticals, personal care products, and EDCs have been detected in biosolids. Ten of these compounds (tonalide, galaxolide, 17ß-estradiol, 17α-ethinylestradiol, ciprofloxacin, doxycycline, norfloxacin, ofloxacin, triclosan, and triclocarban) posed a high (HQ >1.0) hazard to aquatic ecosystems relative to the other compounds. This hazard assessment indicated that further research into potential offsite migration and deleterious effects on aquatic ecosystems is warranted for the 10 organic contaminants identified, and possibly for chemicals with similar physicochemical and toxicological properties, in biosolids-amended soils. Because many antibiotic compounds (e.g., ciprofloxacin, norfloxacin, and ofloxacin) have ionic properties, the methods used may have overestimated their predicted aqueous concentrations and hazard. Further research that includes site-specific variables, e.g., dilution factors in waterways, rain intensity, slope of land, degradation, and the use of management strategies such as buffer zones, is likely to decrease the hazard posed by these high hazard compounds.