Plasticizers are plastic additives used to enhance the physical properties of plastic and are ubiquitous in the environment. A class of plasticizer compounds called phthalate esters that are not fully eliminated in wastewater treatment facilities are relevant to the ecological health of downstream ecosystems and urban areas due to their ecotoxicity, tendency for soil accumulation, and the emerging concern about their effects on public health. However, plasticizer concentrations in a constructed wetland environment have rarely been studied in the United States, prompting the need for a method of plasticizer quantification in the Tres Rios Constructed Wetlands which are sustained by the effluent of the 91st Avenue Wastewater Treatment Plant in Phoenix, Arizona. The concentrations of four common plasticizer compounds (dimethyl: DMP, diethyl: DEP, di-n-butyl: DnBP, and bis(2-ethylhexyl): DEHP phthalate) at five sites across the wetland surface water were quantified using solid-phase extraction followed by gas chromatography coupled with mass spectrometry (GC/MS). The sampling period included four sample sets taken from March 2022 to September 2022, which gave temporal data in addition to spatial concentration data. Quantification and quality control were performed using internal standard calibration, replicate samples, and laboratory blanks. Higher molecular weight phthalates accumulated in the wetland surface water at significantly higher average concentrations than those of lower molecular weight at a 95% confidence level, ranging from 8 ng/L to 7349 ng/L and 4 ng/L to 27876 ng/L for DnBP and DEHP, respectively. Concentrations for dimethyl phthalate and diethyl phthalate were typically less than 50 ng/L and were often below the method detection limit. Average concentrations of DnBP and DEHP were significantly higher during periods of high temperatures and arid conditions. The spatial distribution of phthalates was analyzed. Most importantly, a method for successful ultra-trace quantification of plasticizers at Tres Rios was established. These results confirm the presence of plasticizers at Tres Rios and a significant seasonal increase in their surface water concentrations. The developed analytical procedure provides a solid foundation for the Wetlands Environmental Ecology Lab at ASU to further investigate plasticizers and contaminants of emerging concern and determine their ultimate fate through volatilization, sorption, photodegradation, hydrolysis, microbial biodegradation, and phytoremediation studies.

The integration of Urban Ecological Infrastructure (UEI) has gained attention as cities seek to address challenges posed by urbanization. Constructed treatment wetlands (CTWs), commonly used for removing pollutants from wastewater effluent and storm water runoff, have been proposed as a solution to address challenges posed by rising water challenges. CTWs serve as a unique type of UEI and provide a range of ecosystem services in urban landscapes. With current global concerns over water scarcity and sustainable resource management, wetlands emerge as key components, providing vital ecosystem services, one of which is nutrient filtration. Nitrogen pollution in water bodies poses significant environmental and public health concerns, emphasizing the need for effective mitigation strategies. CTWs present a promising solution for addressing nitrogen pollution in urban settings. However, there are gaps in understanding wetland functioning within arid environments, necessitating arid climate studies to explain nitrogen dynamics. This study, conducted in the Tres Rios Wetland in Phoenix, Arizona, aims to examine nitrogen content in soils. Soil nitrogen content trends from 2019 to 2023 were investigated, with a focus on understanding nitrogen dynamics from inflow to outflow points and comparison from water to shore. There were no trends seen in nitrogen content over time from 2019 to 2023. Additionally, nitrogen levels tended to be higher at the shorelines compared to the open water, likely due to the accumulation of organic matter and soil nitrogen absorption. However, there were no trends observed in nitrogen content from the inflow to outflow points.