Metam sodium is a fumigant often used as a crop pretreatment in agriculture to control a wide array of pests that may inhibit plant yields. Previously, there have only been limited studies conducted on the effects of metam sodium on native soil microbial communities and plant pathogens, and results have been inconsistent. This present study utilized control and metam sodium-treated field plots to examine the effects of metam sodium on soil microbes in terms of numbers, activity, and diversity. Metam sodium did not cause significant changes in culturable heterotrophic numbers, as shown by heterotrophic plate counts, but may have adversely affected non-culturable microbes since metam sodium did affect microbial activity. Specifically, the LuminUltra® and dehydrogenase activity assays both showed a significant decrease in total activity in treated plots one day after soil treatment, with a return to pre-application conditions within seven days. Illumina Next-Generation Sequencing of the 16S rRNA gene showed slight changes in richness and community composition throughout the 28-day study, but initial and final communities were similar in both control and treated soils. Overall, some soil microbes were adversely affected by metam sodium, but the resilience of the soil microbial community allowed for an apparent rapid recovery in terms of numbers, activity, and diversity.

Biostimulation is the use of in-situ microorganisms and added reagents in order to biosequester, precipitate, or absorb contaminants from contaminated groundwater and sediment. To test the effectiveness of this remediation approach at a particular site, small scale experiments, such as miscible-displacement, batch, or microcosm experiments, should be performed before a large-scale in-situ biosequestration electron donor injection. In this study, electron donor solutions containing contaminated groundwater and ethanol, acetate, benzoate, or glucose were injected into aquifer sediments collected from a UMTRCA Title 1 Site in Monument Valley, AZ. These experiments showed that ethanol, acetate, and glucose were effective electron donors for the stimulation of microbial activity in order to sequester uranium and reduce nitrate and sulfate concentrations. Conversely, benzoate was not effective at sequestering or reducing the contaminants. After electron-donor deficient groundwater was injected into the columns, a rebound of nitrate, sulfate, and uranium concentrations was observed. Due to this rebound, it was inferred that the mechanism of sequestration of uranium and hence reduction of nitrate and sulfate was due to the creation of reducing conditions via microbial activity. The insoluble reduced uranium was hypothesized to have precipitated or adsorbed to surrounding sediments. Incoming groundwater contained dissolved oxygen and therefore oxidized the reduced contaminants, consequently returning them into solution. It was hypothesized that a similar rebound would occur if ethanol, acetate, or glucose were to be injected in-situ due to sustained groundwater flow through the aquifer sediments on site.

This study evaluates the effects of nitrogen and phosphorus response in young (two- and three-year-old), non-bearing,'Western Schley' and 'Wichita' varieties of pecan (Carya illinoinensis (Wangenh.) C. Koch) grown in two orchards in San Simon, AZ. Using tree trunk diameter and rates of photosynthesis, transpiration, stomatal conductance, and transpiration as proxies for tree growth and positive response, and by analyzing foliar elemental concentrations of N and P, preliminary results suggest that 'Wichita' responds better than 'Western' to N and P fertilizer with respect to tree growth. Additions of nitrogen ranging from 5.6 kg N·ha⁻¹ to 35.9 kg N·ha⁻¹ increased foliar N concentration in 'Wichita', although there was no response to photosynthesis, stomatal conductance, intracellular CO₂, or transpiration. Additions of phosphorus fertilizer up to 112 kg·ha⁻¹ improved tree growth; and growth increased with increasing foliar P concentration.

Irrigation agriculture is the largest use of water (~80%) in the United States ('Irrigation and Water Use', 2016) A combination of irrigation and precipitation infiltrates through the Earth's subsurface and represents the primary inputs to an agricultural field's groundwater system. This water propagates down from the surface, with some of it recharging the underlying groundwater storage as return flow. The difference between the amount of irrigation water applied and the return flow to the aquifer, represents the consumptive use of the system. The alterations in the quality and distribution of water from groundwater pumping and irrigation places greater emphasis on the need to understand the connection between agricultural consumption and subsurface groundwater flux. Temperature fluctuations in the Earth's shallow subsurface are mainly governed by spatial and temporal variations in temperature at the ground surface (Hatch et al., 2006). These temperature signals at depth are primarily controlled by advection, dispersion, and thermal conduction. It has been shown for streambeds that when temperature propagates through the subsurface, it is a nonlinear function of fluid velocity, the frequency of the surface temperature variations, and the sediment and fluid thermal properties (Stallman, 1965). This information has been useful for understanding fluxes for saturated conditions such as in stream systems, but has not yet been applied to understand consumptive use in unsaturated conditions such as in agricultural systems. Temperature propagation in unsaturated conditions is different than saturated conditions due to changes in soil and thermal properties. Previous models have had difficulty estimating groundwater fluxes for some unsaturated conditions. This study experiments with the possibility of using a combination of MATLAB and HYDRUS 1D to infer unsaturated groundwater fluxes, saturated hydraulic conductivity, and saturated water content. One application of this type of flux estimation could be the inference of root water uptake and the consumptive use of an agricultural system. The method is designed to calculate root water uptake under steady-state conditions; and therefore might have limitations for quantifying consumptive use in field applications.It is beneficial to research the consumptive use in agricultural systems in order to gain understanding of the effects of irrigation on the total flux in groundwater storage. Other applications of consumptive use include: site specific farm efficiency and crop use parameters, nonpoint source pollution to estimate nutrient fluxes, irrigation efficiency, soil salinization, waste isolation, and slope stability.

<p>Coal fired power plants generate approximately 45% of the electricity produced in the United States every year, and each year, over 100 million tons of coal ash are produced as a by-product of electricity generation. Coal ash is a solid waste made up principally of bottom ash, fly ash, and flue gas desulfurization materials. The chemical composition of coal ash varies depending on the feed coal source, combustion parameters, and the presence and type of air pollution control devices that remove contaminants from the flue gas into the solid waste stream. Although a significant portion of coal ash waste is recycled, the majority of coal ash is disposed in landfills and holding ponds. Coal ash impoundments have a long history of environmental degradation, which includes: contaminant leaching into groundwater, the discharge of contaminant-laden effluent into surface waters, and catastrophic impoundment failures and ash spills. Despite these known problems, coal ash is not considered a hazardous waste, and thus is not subject to stringent disposal requirements. The current coal ash management system is based on risk assessments of coal ash that do not include environmental parameters that have a profound impact on coal ash contaminant mobility, particularly for the toxic elements such as mercury, arsenic, and selenium. This dissertation research focused on the biogeochemical transformations of mercury, arsenic, and selenium associated with coal ash materials in an effort to: (1) define the key environmental parameters controlling mercury, arsenic, and selenium fate during disposal and ash spills; and (2) delineate the relationship between coal ash characteristics, environmental parameters, and leaching potential. </p><p> The impact of coal ash on mercury transformations in anaerobic systems was assessed using anaerobic sediment-ash microcosms to mimic an ash spill into a benthic aquatic system. Anaerobic sediments are the primary zones for the microbial conversion of inorganic mercury to methyl mercury (MeHg), a process that is mediated by anaerobic bacteria, particularly sulfate reducing bacteria (SRB). MeHg is a potent neurotoxin that biomagnifies up the aquatic food chain, presenting a human health risk-- especially to children and pregnant women. The results of the sediment-ash microcosm experiments indicated negligible net production of MeHg in microcosms with no ash and in microcosms amended with the low-sulfate/low-Hg ash. In contrast, microcosms amended with sulfate and mercury-rich ash showed increases in MeHg concentrations that were two to three times greater than control microcosms without ash. The enhancement MeHg production in the microcosms was likely due to large quantities of leachable sulfate that stimulated the activity of methylating bacteria. Overall, these results highlight the importance of considering both the geochemical conditions of the receiving environment and the chemical composition of the coal ash in assessing the MeHg potential of coal ash. </p><p> The hypothesis that sulfate-rich coal ash can change sediment microbial communities, enhancing MeHg production, was tested by analyzing coal ash impacts on the SRB community in the sediment-ash microcosms using Terminal Restriction Fragment Length Polymorphism (T-RFLP), Quantitative Polymerase Chain Reaction (q-PCR), and Reverse Transcription-qPCR (RT-qPCR). Coal ash did not appear to cause significant changes to the structure of the overall bacterial community, though results showed that it may have caused a decrease in the evenness for species distribution for both SRB and the overall microbial community. During the five-day incubation experiment, the coal ash had a temporary significant effect on SRB abundance during the first one to two days of the experiment and a more sustained effect on SRB activity. This stimulation of SRB population growth and activity also corresponded with increasing net MeHg production. Overall, results indicate that coal ash amendments do not cause large shifts in the overall microbial community or the SRB community, but results indicate that there are connections between SRB abundance/activity and MeHg production. More research is needed to determine how coal ash directly impacts Hg methylating microorganisms, which include diverse array of microorganisms outside of SRB.</p><p> The effect of aerobic and anaerobic conditions on arsenic and selenium leaching from coal ash in an ash spill scenario was also assessed using sediment-ash microcosms. The fate of arsenic and selenium associated with coal ash is of particular concern due to the leachability of these elements at neutral pH and their tendency to bioaccumulate in aquatic organisms. Both the redox speciation of arsenic and selenium, and the pH of the aquatic system, are known to influence leaching into the environment, yet current environmental risk assessments of coal ash focus on pH alone as the primary driving force for arsenic and selenium leaching from coal ash and do not take into account the effects of anaerobic conditions and microbial activity. In this research, total dissolved concentrations of arsenic and selenium, dissolved speciation of arsenic, and solid phase speciation of selenium were monitored to determine the biogeochemical transformations and leaching of arsenic and selenium under differing redox conditions. The results from the sediment-ash microcosm studies showed that redox potential was the major determinant of arsenic and selenium mobility in the microcosm systems with greater arsenic leaching occurring in anaerobic microcosms and greater selenium leaching occurring in aerobic microcosms. Furthermore, the experiments provided clues to how coal ash influences the geochemistry of the benthic environment and how these influences affect the speciation and longer term solubility of arsenic and selenium. </p><p> Finally, experiments were conducted to determine how differing CaO, SO3, and Fe2O3 concentrations in coal ash affect the release of arsenic and selenium from sediment-ash mixtures in a simulated ash spill environment. Aerobic and anaerobic sediment-ash microcosms were constructed to mimic an ash spill into a benthic aquatic system, and a variety of coal ash materials were tested as amendments, including seven fly ashes, one lime-treated fly ash sample, and two FGD samples. Results showed that, in most cases, the sediment in the microcosm buffered the system at neutral, which counteracted leaching impacts of differing CaO and SO3 concentrations in the microcosms. Regardless of ash material, leaching of selenium was greater under aerobic conditions and was correlated with the total selenium content of the microcosm. Maximum leaching of arsenic occurred in anaerobic microcosms for some ash materials and in aerobic microcosms for other materials, suggesting that ash material chemistry played a significant role in controlling arsenic mobility. In both aerobic and anaerobic microcosms, dissolved arsenic concentration was correlated with total arsenic content of the ash material and in anaerobic microcosms, dissolved arsenic concentrations also correlated with the total iron content of the ash material. Overall, the results of these experiments showed that arsenic and selenium release under environmentally relevant conditions cannot be predicted by the CaO and SO3 content of the ash material. Rather, the total arsenic, total selenium content, and total iron content of the ash material are good predictors of the worst case environmental leaching scenario.</p><p> These investigations illuminated two major conclusions: (1) microbial activity and differing redox conditions are key in determining the impact of coal ash on the environment and in determining the mobility of coal ash contaminants, and (2) coal ash characteristics, such as sulfate and iron content, can change the redox chemistry and microbial activity of the surrounding environment, further influencing the fate of ash contaminants. This work will be useful in designing a framework that accurately predicts the leaching potential of ash contaminants under environmentally relevant conditions. The results will also be helpful in developing treatment technologies for ash impoundment effluent, guiding decisions on ash pond closure and remediation, and in designing long-term monitoring plans and remediation strategies for ash-impacted sites.</p> / Dissertation

Wastewater effluent produced in the fiberglass manufacturing industry contains a significant amount of total suspended solids. Environmental regulations require pretreatment of effluent before it is discharged to the municipal wastewater treatment plant. Chemical precipitation by coagulation and flocculation is the method of pretreatment used at the Vetrotex CertainTeed Corporation (VCT). A treatability study was conducted to determine conditions at which the VCT Wastewater Pretreatment Plant could operate to consistently achieve a total suspended solids concentration ≤ 200-mg/L. Jar tests varied pH, polymer dosage, and ferric sulfate dosage. Total suspended solids and turbidity were measured to evaluate treatment performance. The data were used to determine an optimum set of conditions under project guidelines. Of twelve polymers screened, BPL 594 was selected as the most effective polymer. For cost efficiency in the wastewater pretreatment operation, recommendations suggested that treatment chemical injection be electronically controlled according to turbidity of the treated effluent.

<p>Selenium (Se) is a micronutrient necessary for the function of a variety of important enzymes; Se also exhibits a narrow range in concentrations between essentiality and toxicity. Oviparous vertebrates such as birds and fish are especially sensitive to Se toxicity, which causes reproductive impairment and defects in embryo development. Selenium occurs naturally in the Earth's crust, but it can be mobilized by a variety of anthropogenic activities, including agricultural practices, coal burning, and mining. </p><p>Mountaintop removal/valley fill (MTR/VF) coal mining is a form of surface mining found throughout central Appalachia in the United States that involves blasting off the tops of mountains to access underlying coal seams. Spoil rock from the mountain is placed into adjacent valleys, forming valley fills, which bury stream headwaters and negatively impact surface water quality. This research focused on the biological impacts of Se leached from MTR/VF coal mining operations located around the Mud River, West Virginia. </p><p>In order to assess the status of Se in a lotic (flowing) system such as the Mud River, surface water, insects, and fish samples including creek chub (Semotilus atromaculatus) and green sunfish (Lepomis cyanellus) were collected from a mining impacted site as well as from a reference site not impacted by mining. Analysis of samples from the mined site showed increased conductivity and Se in the surface waters compared to the reference site in addition to increased concentrations of Se in insects and fish. Histological analysis of mined site fish gills showed a lack of normal parasites, suggesting parasite populations may be disrupted due to poor water quality. X-ray absorption near edge spectroscopy techniques were used to determine the speciation of Se in insect and creek chub samples. Insects contained approximately 40-50% inorganic Se (selenate and selenite) and 50-60% organic Se (Se-methionine and Se-cystine) while fish tissues contained lower proportions of inorganic Se than insects, instead having higher proportions of organic Se in the forms of methyl-Se-cysteine, Se-cystine, and Se-methionine. </p><p>Otoliths, calcified inner ear structures, were also collected from Mud River creek chubs and green sunfish and analyzed for Se content using laser ablation inductively couple mass spectrometry (LA-ICP-MS). Significant differences were found between the two species of fish, based on the concentrations of otolith Se. Green sunfish otoliths from all sites contained background or low concentrations of otolith Se (< 1 µg/g) that were not significantly different between mined and unmined sites. In contrast creek chub otoliths from the historically mined site contained much higher (&#8805; 5 µg/g, up to approximately 68 µg/g) concentrations of Se than for the same species in the unmined site or for the green sunfish. Otolith Se concentrations were related to muscle Se concentrations for creek chubs (R2 = 0.54, p = 0.0002 for the last 20% of the otolith Se versus muscle Se) while no relationship was observed for green sunfish. </p><p>Additional experiments using biofilms grown in the Mud River showed increased Se in mined site biofilms compared to the reference site. When we fed fathead minnows (Pimephales promelas) on these biofilms in the laboratory they accumulated higher concentrations of Se in liver and ovary tissues compared to fathead minnows fed on reference site biofilms. No differences in Se accumulation were found in muscle from either treatment group. Biofilms were also centrifuged and separated into filamentous green algae and the remaining diatom fraction. The majority of Se was found in the diatom fraction with only about 1/3rd of total biofilm Se concentration present in the filamentous green algae fraction </p><p>Finally, zebrafish (Danio rerio) embryos were exposed to aqueous Se in the form of selenate, selenite, and L-selenomethionine in an attempt to determine if oxidative stress plays a role in selenium embryo toxicity. Selenate and selenite exposure did not induce embryo deformities (lordosis and craniofacial malformation). L-selenomethionine, however, induced significantly higher deformity rates at 100 µg/L compared to controls. Antioxidant rescue of L-selenomethionime induced deformities was attempted in embryos using N-acetylcysteine (NAC). Pretreatment with NAC significantly reduced deformities in the zebrafish embryos secondarily treated with L-selenomethionine, suggesting that oxidative stress may play a role in Se toxicity. Selenite exposure also induced a 6.6-fold increase in glutathione-S-transferase pi class 2 gene expression, which is involved in xenobiotic transformation. No changes in gene expression were observed for selenate or L-selenomethionine-exposed embryos.</p><p>The findings in this dissertation contribute to the understanding of how Se bioaccumulates in a lotic system and is transferred through a simulated foodweb in addition to further exploring oxidative stress as a potential mechanism for Se-induced embryo toxicity. Future studies should continue to pursue the role of oxidative stress and other mechanisms in Se toxicity and the biotransformation of Se in aquatic ecosystems.</p> / Dissertation

The Nogales International Wastewater Treatment Plant releases treated wastewater from both Nogales, Arizona and Nogales, Sonora, Mexico into the Santa Cruz River. In recent years, the discharged effluent has contained high levels of cadmium and nickel, which exceed the plant's permit standards. Due to the industrial demographic of the region, outdated infrastructure, and differences in sampling schedules of multiple organizations, the treatment facility and the treated effluent is an important area of study. To understand how the treated effluent is affecting the river, data were compiled from existing water quality databases and flow reports from 2008 to 2015. To address how flow quantity has changed during drought periods, effluent flows were compared to historical flood data produced by the USGS. To evaluate water quality issues, water quality reports produced by the International Boundary and Water Commission were examined for past exceedances of constituents. According to flow volumes reported at the U.S.-Mexico border, the majority of the effluent was produced in Nogales, Sonora. Results showed that spikes in effluent flow corresponded with rainfall events. Results also show that rainfall influences the flow volumes from Nogales, Arizona, but there is little impact to flow volumes from Mexico. Although the quality of the effluent generally meets the permitted standards, exceedances did occur. The potential impact of such exceedances on stream water quality was evaluated using measured and simulated data. Although outreach to stakeholders across the border and updated infrastructure has improved the quality of water in the river, there are still many areas to improve upon, including sampling and monitoring schedules. To identify opportunities for improvement, further studies should examine the specific fate of each contaminant present in the effluent.

<p>Waste-derived organic products are nutrient-rich materials often applied to agricultural land as a fertilizer to enhance agricultural production and soil quality. Commercially available biosolid-based products, which are sold and distributed in bags or bulk, are rapidly gaining popularity for urban and suburban use. Although biosolid-derived products have many benefits, they may contain trace organic contaminants such as per- and polyfluoroalkyl acids (PFAAs) and pharmaceutical and personal care products (PPCPs), in varying levels, depending on waste source composition. These organic compounds have been used in a variety of consumer and industrial products and are known to accumulate in biosolids due to their recalcitrance in conventional wastewater treatment processes. Thus, the application of commercially available biosolids-based products on urban and suburban gardens may lead to transfer and accumulation of organic contaminants into food crops, raising food safety concerns. Most studies to date have focused on municipal biosolids application on agricultural lands with very few studies focused on commercial products available for home and urban gardens. For the latter, the evaluations of bioavailability and subsequent plant uptake of organic contaminants from biosolids have also often been conducted by adding organic contaminants to the growing media (e.g., soil or hydroponic) at a concentration that greatly exceed environmentally relevant concentrations. Moreover, there are currently no studies evaluating leaching and plant uptake potential of contaminants from commercially available (e.g., local stores) biosolids. The research described in this dissertation 1) assessed the occurrence of PFAAs and representative PPCPs in commercially available biosolid-based products and their porewater concentrations in saturated media as a measure of bioavailability and leachability; 2) investigated how heat-treatment, composting, blending and thermal hydrolysis processes on biosolids to convert them to commercial biosolid-based products affect PFAA concentrations in the production of commercial biosolid-based product; and 3) assessed the bioavailability and plant uptake of PFAAs and targeted PPCPs by kale and turnips grown in soil-less potting media amended with Milorganite (a commercially available biosolids-based fertilizer product) at the recommended rate and four times the recommended rate.</p><p>The biosolid-based products displayed varying levels of organic contaminants. Higher PFAA concentrations were detected in biosolid-based products compared to nonbiosolid-based products. The common treatment processes used in taking biosolids to commercially available products were ineffective in reducing PFAA levels in the products except for blending with other essentially PFAA-free materials, thus served as a simple dilution. Porewater concentrations of PFAAs and PPCPs as an indicator of leachability and bioavailability were higher for the less hydrophobic compounds (e.g., short-chain PFAAs and diphenhydramine and carbamazepine with lower octanol-water partition coefficient). Leachability alone did not explain the observed plant uptake potential of PFAAs and PPCPs. With similar leachability and molecular weight/size between diphenhydramine and carbamazepine, higher uptake was observed with a positively charged compound (diphenhydramine compared to a neutral compound (carbamazepine). However, not all positively charged compounds were taken up by the plant. Azithromycin, a positively charged compound, had lower uptake than other contaminants which may be due to its large molecular size compared to diphenhydramine. Higher concentrations of miconazole, triclosan, and triclocarban were found in the biosolids-fertilizer; however, these compounds had low leachabilities and limited uptake by plants. Also, for PPCPs, the application rates of biosolid-based products did not necessarily correlate with the higher uptake and translocation of contaminants to the above-ground portion of plants. </p><p>This study provides an evaluation of commercially available waste-derived organic products under condition comparable to home and urban garden setting. Although biosolids-based products can serve as alternatives to synthetic fertilizers, they contain higher levels of trace organic contaminants than nonbiosolid-organic products. Common biosolids treatment processes are ineffective for reducing the levels of trace organic contaminants in biosolids, particularly for PFAAs. Thus, it is critical to control the sources contributing to the higher level of these contaminants in biosolids-based products. Also, regulations (e.g., triclosan and triclocarban) and replacements (e.g., longer-chain PFAAs to short-chain PFAAs) of persistent trace organic chemicals have led to a reduction in their levels in biosolids-based products. Although longer chain PFAAs are more likely to bioaccumulate and persistent than the replacement short-chain alternatives, the current study has shown that the short-chain PFAAs are more readily taken up to edible parts of plants than longer-chain PFAAs even when applying at the recommended fertilizer rate. Thus, the current movement to replace longer chain PFAAs with short chains has the potential to result in higher total PFAA concentrations being bioavailable for plant uptake, thus increasing the risk of food contamination by PFAAs. </p>

<div> <p>In recent years, the presence of per- and polyfluoroalkyl substances (PFAS) in aquatic systems has led to research on their fate, effects and treatability. PFAS have been found in various environmental matrices including wastewater effluents, surface, ground, and drinking water. Perfluoroalkyl acids (PFAAs) are the class of PFAS most commonly tested due to their ability to migrate rapidly through groundwater and include perfluoroalkyl sulfonic acids (PFSAs) and perfluoroalkyl carboxylic acids (PFCAs). Of the globally distributed and persistent PFAAs, PFSAs are the most resistant to biological and oxidative chemical attack. This doctoral study focused on a reductive treatment approach with zero valent metals/bimetals nanoparticles (NPs) synthesized onto a carbon material to reduce NP aggregation. Initial work focused on exploring reactivity of different combinations of nano (n) Ni, nFe⁰ and activated carbon (AC) at 22 ^oC to 60 ^oC for transforming perfluorooctanesulfonate (PFOS) from which nNiFe⁰-AC at 60 ^oC led to transformation of both linear (L-) and branched (Br-) PFOS isomers. The remaining research focused on work with nNiFe⁰-AC at 60 ^oC in batch reactors including optimizing nNiFe⁰-AC preparation, quantifying PFOS transformation kinetics and evaluating the effects of PFAA chain length (C4, C6 and C8) and polar head group (PFSA versus PFCA) as well a groundwater matrix on transformation magnitude. Optimization of analytical methods to provide multiple lines of evidence of transformation including fluoride, sulfite and organic product generation was an ongoing throughout the research.</p> <p>nNiFe⁰-AC prepared with a 3-h synthesis stirring time led to the highest PFOS transformation of 51.1 ± 2.1% with generation of ~ 1 mole of sulfite (measured as sulfate) and 12 moles of fluoride. Several poly/per-fluorinated intermediates with single and double bonds were identified using quadrupole time-of-flight mass spectrometry (QToF-MS) in negative electrospray ionization (ESI-) mode with MS/MS fragmentation confirmation as well as one and later two desulfonated products with QToF negative atmospheric pressure chemical ionization (APCI-). All organic transformation products were found in only particle extracts as well as most of the sulfite generated. PFOS transformation kinetics showed that generated fluoride concentrations increased for the first day whereas sulfate concentrations continued to increase during the 5-d reaction. The transformation products identified showed defluorination of single- and double-bond structures, formation of C8 to C4 PFCAs and paraffins from cleavage of the C-S bond.</p> <p>The length of the perfluoroalkyl chain affected the length of time to achieve peak removal, but overall magnitude of transformation when reactions appeared complete were similar for both PFSAs and PFCAs. Like PFOS, PFOA transformation maxed in 1 d whereas shorter chains required more time to reach their peak removal, which is hypothesized to be due to lower sorption of the shorter chain PFAAs to the reactive surfaces. Measured F mass balance was higher for PFOS and PFOA (>90% F) compared to shorter chain PFAAs (~50-70% F). The Perfluorohexanesulfonate (PFHxS) and perfluorobutanesulfonate (PFBS) degradation products include single bond polyfluoroalkyl sulfonates and shorter-chain perfluoroalkyl carboxylates. For example, PFHxS transformation resulted in perfluorohexane carboxylic acid (PFHxA) and perfluorobutane carboxylic acid (PFBA). PFCA transformation products included per- & polyfluoroalkyl carboxylates with single bonds and alcohols with single and double bonds. The effect of inorganic matrix on transformation with nNiFe⁰-AC at 60 ^oC was explored using a contaminated groundwater collected at a former fire-training area in Massachusetts. Transformation appeared ‘generally’ lower than in the single-solute clean water systems, which may have been due to the presence of PFAS precursors that degraded to PFAAs and competitive adsorption between anionic PFAAs and inorganic ions onto the NP surface.</p><p>The research presented here demonstrates that nNiFe⁰-AC at 60 ^oC can mineralize PFAAs even in a typical groundwater matrix. Additional lab and pilot scale studies are needed to clarify the mechanisms leading to transformation as well as why transformation reactions plateau prior to all the parent compounds being transformed. The latter may be due to a poisoning phenomenon that can occur in closed systems, which may not occur in a flowing system more characteristic of an environmental scenario, as well as surface area and reactive site constraints or particle passivation.</p></div>