ARCHIVED CONTENT: In December 2020, the CZO program was succeeded by the Critical Zone Collaborative Network (CZ Net) ×

MS Thesis Defense


Natural Attenuation of EDC-PPCPs in the Critical Zone

Marshall 539

Rachel Maxwell, Soil Water and Environmental Science, will present her MS thesis research.


Trace organic contaminants of emerging concern include chemicals known as endocrine disrupting compounds, pharmaceuticals, and personal care products (EDC-PPCPs). For cases where wastewater discharge is coupled with ecosystem irrigation, it is essential to understand the extent to which these associated contaminants are attenuated through biogeochemical processes in the critical zone (CZ). We hypothesized that soil biogeochemical processes affect the fate and transport of trace organic contaminants through near surface soils and into surface waters in a way that should be predictable from knowledge of a compound’s physico-chemical properties. This hypothesis was tested in the Santa Catalina Mountains Critical Zone Observatory (SCM-CZO). In this CZO, the Summerhaven wastewater treatment plant delivers secondary-treated wastewater (at 1.1 MGY) into a forested hillslope system for tertiary “polishing” prior to discharge to surface water in Oracle Ridge. Samples were interrogated for thirteen different EDC-PPCPs and normalized percent removal was correlated with compound (i) aqueous solubility, (ii) octanol-water partition coefficient, (iii) charge, and (iv) biodegradability. Overall, a compound’s physico-chemical properties do not yield enough information to correctly predict how EDC-PPCPs are attenuated in the CZ; a larger knowledge of environmental factors, such as stream flow rate, organic matter content, and solar radiance are needed to fully understand how these trace organic contaminates are transported. Although attenuation was unable to be predicted it was still determined that soils with in the spray field diminish EDC-PPCP concentrations by 44-99% prior to discharge into surface waters, and that surface waters further decrease EDC-PPCP concentrations by 67-99%.


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