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This research investigates the formation of free radical intermediates in an advanced oxidation processes (AOP) capable of destroying recalcitrant contaminants. The AOP studied is marketed as OxyZone® and relies on the premise of successful persulfate activation by peroxone (hydrogen peroxide plus ozone) and the formation of free radicals. The goal of this research was to determine which radicals are involved in the treatment of the model contaminant, 1,4-dioxane, which is a ubiquitous, recalcitrant organic groundwater pollutant difficult to destroy by conventional oxidants. In a parallel study, the peroxone activation persulfate (PAP) solution investigated herein rapidly degraded 1,4-dioxane. The degradation rates of 1,4-dioxane were measured as a function the oxidant:contaminant ratio. Its degradation products or mechanism were not investigated, however. Electron paramagnetic resonance (EPR) spectroscopy spin trapping was used to identify radicals produced in the oxidant solution, its active ingredients, and their possible interplay. The data presented herein indicate that the combination of hydrogen peroxide and dissolved ozone in the presence of persulfate results in the co-occurrence hydroxyl and sulfate radicals and possibly superoxide/hydroperoxyl radicals. These findings progress our understanding of the chemical radicals formed during PAP treatment of aqueous phase contaminants, such as 1,4-dioxane.
Michaela A. Cashman; Louis Kirschenbaum; Justin Holowachuk; Thomas B. Boving. Identification of hydroxyl and sulfate free radicals involved in the reaction of 1,4-dioxane with peroxone activated persulfate oxidant. Journal of Hazardous Materials 2019, 380, 120875 .
AMA StyleMichaela A. Cashman, Louis Kirschenbaum, Justin Holowachuk, Thomas B. Boving. Identification of hydroxyl and sulfate free radicals involved in the reaction of 1,4-dioxane with peroxone activated persulfate oxidant. Journal of Hazardous Materials. 2019; 380 ():120875.
Chicago/Turabian StyleMichaela A. Cashman; Louis Kirschenbaum; Justin Holowachuk; Thomas B. Boving. 2019. "Identification of hydroxyl and sulfate free radicals involved in the reaction of 1,4-dioxane with peroxone activated persulfate oxidant." Journal of Hazardous Materials 380, no. : 120875.
Little is known about the release of metal engineered nanomaterials (ENMs) from consumer goods including lumber treated with micronized copper. Micronized copper is a recent form of anti‐fouling wood preservative containing nano‐sized copper particles for use in pressure treated lumber. This study investigated the concentrations released and release rate of total copper over 133 days under freshwater, estuarine, and marine salinity conditions (0, 1, 10, and 30‰) for several commercially available pressure treated lumbers: micronized copper azole (MCA) at 0.96 and 2.4 kg/m3, alkaline copper quaternary (ACQ) at 0.30 and 9.6 kg/m3, and chromated copper arsenate (CCA) at 40 kg/m3. Lumber was tested as blocks and sawdust. Overall, copper was released from all treated lumber samples. Under leaching conditions, total release ranged from 2 to 55% of the measured copper originally in the lumber with release rate constants from the blocks of 0.03 to 2.71 in units of /day. Generally, measured release and modelled equilibrium concentrations were significantly higher in the estuarine conditions compared to freshwater or marine salinities while rate constants showed very limited differences between salinities. Further, organic carbon was released during the leaching and demonstrated a significant relationship with released copper concentrations as a function of salinity. This work indicates copper is released into estuarine/marine waters from multiple wood treatments including lumber amended with nanoparticle size copper. This article is protected by copyright. All rights reserved
Ashley N Parks; Mark G Cantwell; David R Katz; Michaela A Cashman; Todd P Luxton; Kay T Ho; Robert M Burgess. Assessing the release of copper from nanocopper-treated and conventional copper-treated lumber into marine waters I: Concentrations and rates. Environmental Toxicology and Chemistry 2018, 37, 1956 -1968.
AMA StyleAshley N Parks, Mark G Cantwell, David R Katz, Michaela A Cashman, Todd P Luxton, Kay T Ho, Robert M Burgess. Assessing the release of copper from nanocopper-treated and conventional copper-treated lumber into marine waters I: Concentrations and rates. Environmental Toxicology and Chemistry. 2018; 37 (7):1956-1968.
Chicago/Turabian StyleAshley N Parks; Mark G Cantwell; David R Katz; Michaela A Cashman; Todd P Luxton; Kay T Ho; Robert M Burgess. 2018. "Assessing the release of copper from nanocopper-treated and conventional copper-treated lumber into marine waters I: Concentrations and rates." Environmental Toxicology and Chemistry 37, no. 7: 1956-1968.
Nonpoint source nitrogen pollution is difficult to effectively model in groundwater systems. This study aims to elucidate anthropogenic nonpoint source pollution discharging into Potowomut Pond and ultimately Narragansett Bay. Hydrologic modeling with Soil and Water Assessment Tool (SWAT) and SWAT Calibration and Uncertainty Program (SWAT-CUP) was used to simulate streamflow and nitrogen levels in the Hunt River with and without onsite wastewater treatment systems (OWTS). The objective of this study was to determine how input of OWTS data impacts nitrogen loading into the Hunt River Watershed in Rhode Island, USA. The model was simulated from 2006 to 2014, calibrated from 2007 to 2011 and validated from 2012 to 2014. Observed streamflow data was sourced from a US Geological Survey gauge and nitrogen loading data from University of Rhode Island Watershed Watch (URIWW). From the results, adding OWTS data to the SWAT simulation produced a better calibration and validation fit for total fit (Nash–Sutcliffe Efficiency (NSE) = 0.50 calibration, 0.78 validation) when compared with SWAT simulation without OWTS data (NSE = −1.3 calibration, −6.95) validation.
Supria Paul; Michaela A. Cashman; Katelyn Szura; Soni M. Pradhanang. Assessment of Nitrogen Inputs into Hunt River by Onsite Wastewater Treatment Systems via SWAT Simulation. Water 2017, 9, 610 .
AMA StyleSupria Paul, Michaela A. Cashman, Katelyn Szura, Soni M. Pradhanang. Assessment of Nitrogen Inputs into Hunt River by Onsite Wastewater Treatment Systems via SWAT Simulation. Water. 2017; 9 (8):610.
Chicago/Turabian StyleSupria Paul; Michaela A. Cashman; Katelyn Szura; Soni M. Pradhanang. 2017. "Assessment of Nitrogen Inputs into Hunt River by Onsite Wastewater Treatment Systems via SWAT Simulation." Water 9, no. 8: 610.
To understand their fate and transport in estuarine systems, the aggregation, sedimentation, and dissolution of CdSe quantum dots (QDs) in seawater were investigated. Hydrodynamic size increased from 40 to 60 nm to >1 mm within 1 h in seawater, and the aggregates were highly polydispersed. Their sedimentation rates in seawater were measured to be 4–10 mm/day. Humic acid (HA), further increased their size and polydispersity, and slowed sedimentation. Light increased their dissolution and release of dissolved Cd. The ZnS shell also slowed release of Cd ions. With sufficient light, HA increased the dissolution of QDs, while with low light, HA alone did not change their dissolution. The benthic zone in estuarine systems is the most probable long-term destination of QDs due to aggregation and sedimentation. The bioavailability of was evaluated using the mysid Americamysis bahia. The 7-day LC50s of particulate and dissolved QDs were 290 and 23 μg (total Cd)/L, respectively. For mysids, the acute toxicity appears to be from Cd ions; however, research on the effects of QDs should be conducted with other organisms where QDs may be lodged in critical tissues such as gills or filtering apparatus and Cd ions may be released and delivered directly to those tissues.
Yao Xiao; Kay T. Ho; Robert M. Burgess; Michaela Cashman. Aggregation, Sedimentation, Dissolution, and Bioavailability of Quantum Dots in Estuarine Systems. Environmental Science & Technology 2016, 51, 1357 -1363.
AMA StyleYao Xiao, Kay T. Ho, Robert M. Burgess, Michaela Cashman. Aggregation, Sedimentation, Dissolution, and Bioavailability of Quantum Dots in Estuarine Systems. Environmental Science & Technology. 2016; 51 (3):1357-1363.
Chicago/Turabian StyleYao Xiao; Kay T. Ho; Robert M. Burgess; Michaela Cashman. 2016. "Aggregation, Sedimentation, Dissolution, and Bioavailability of Quantum Dots in Estuarine Systems." Environmental Science & Technology 51, no. 3: 1357-1363.
In many coastal watersheds and ecosystems, rivers discharging to estuaries receive waters from domestic wastewater treatment plants resulting in the release and distribution of pharmaceuticals to the marine environment. In the present study, 15 active pharmaceutical ingredients (APIs) were measured regularly over 1 year in the dissolved and particulate phases as they entered Narragansett Bay from the Pawtuxet River in Cranston, RI, USA. Of the APIs measured, 14 were consistently present in the dissolved phase, with concentrations ranging from below detection to > 310 ng/L, while 8 of the APIs were present in the particulate phase (0.2 ng/g to 18 ng/g). Partition coefficients (Kds and Kocs) were determined and organic carbon normalization reduced variability associated with Kds for the APIs evaluated. Flux estimates based on river flow were calculated for both dissolved and particulate phase APIs, with particulate fluxes being low (1 g/yr to 12 g/yr) while dissolved fluxes of APIs were 155 g/yr to 11,600 g/yr. Results indicate that the pharmaceuticals measured in the present study reside primarily in the dissolved phase and thus are likely bioavailable upon entering the estuarine waters of Narragansett Bay. This long-term temporal study provides important information on seasonal and annual dynamics of pharmaceuticals in an urban estuarine watershed. This article is protected by copyright. All rights reserved
Mark G. Cantwell; David R. Katz; Julia C. Sullivan; Kay Ho; Robert M. Burgess; Michaela Cashman. Selected pharmaceuticals entering an estuary: Concentrations, temporal trends, partitioning, and fluxes. Environmental Toxicology and Chemistry 2016, 35, 2665 -2673.
AMA StyleMark G. Cantwell, David R. Katz, Julia C. Sullivan, Kay Ho, Robert M. Burgess, Michaela Cashman. Selected pharmaceuticals entering an estuary: Concentrations, temporal trends, partitioning, and fluxes. Environmental Toxicology and Chemistry. 2016; 35 (11):2665-2673.
Chicago/Turabian StyleMark G. Cantwell; David R. Katz; Julia C. Sullivan; Kay Ho; Robert M. Burgess; Michaela Cashman. 2016. "Selected pharmaceuticals entering an estuary: Concentrations, temporal trends, partitioning, and fluxes." Environmental Toxicology and Chemistry 35, no. 11: 2665-2673.