Publications by authors named "Knappe D"

Per- and polyfluoroalkyl substances (PFAS) occur widely in drinking water, and consumption of contaminated drinking water is an important human exposure route. Granular activated carbon (GAC) adsorption can effectively remove PFAS from water. To support the design of GAC treatment systems, a rapid bench-scale testing procedure and scale-up approach are needed to assess the effects of GAC type, background water matrix, and empty bed contact time (EBCT) on GAC use rates.

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Dietary intake can be an important exposure route to per- and polyfluoroalkyl substances (PFASs). Little is known about the bioaccumulation of emerging per- and polyfluoroalkyl ether acids (PFEAs) in garden produce from PFAS-impacted communities and the associated dietary exposure risk. In this study, 53 produce samples were collected from five residential gardens near a fluorochemical manufacturer.

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Per- and polyfluoroalkyl substances (PFAS) are widespread contaminants with adverse environmental and public health effects. Anion exchange (IX) processes can effectively remove many PFAS from water. Objectives of this research were to (1) quantify the effects of PFAS structure and background water matrix constituents [dissolved organic matter (DOM) and major inorganic anions (bicarbonate, chloride, sulfate, and nitrate)] on PFAS uptake capacity of IX resins (K), and (2) develop models that predict PFAS breakthrough in packed bed IX columns from PFAS structure and background water matrix characteristics.

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Per- and polyfluoroalkyl substances (PFAS) are known to be highly persistent in groundwater, making it vital to develop new approaches to important practical questions such as the time scale for future persistence of PFAS in contaminated groundwater. In the approach presented here, groundwater from beneath streambeds was analyzed for PFAS and age-dated using SF and H/He. The results were coupled with groundwater flux measurements in a convolution approach to estimate past and future PFAS concentrations in groundwater discharge to the streams.

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Granular activated carbon (GAC) adsorption is frequently used to remove recalcitrant organic micropollutants (MPs) from water. The overarching aim of this research was to develop machine learning (ML) models to predict GAC performance from adsorbent, adsorbate, and background water matrix properties. For model calibration, MP breakthrough curves were compiled and analyzed to determine the bed volumes of water that can be treated until MP breakthrough reaches ten percent of the influent MP concentration (BV10).

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Article Synopsis
  • * Data analysis shows that GenX concentrations decrease with depth across four types of aquifers, highlighting long-term vertical contamination from air emissions.
  • * Though some deep wells exceed certain drinking water standards, they could present a viable and potentially cost-effective option for residents impacted by PFAS contamination in shallower groundwater sources.
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Detection and monitoring of per- and polyfluoroalkyl substances (PFAS) in aquatic environments has become an increasingly higher priority of regulatory agencies as public concern for human intake of these chemicals continues to grow. While many methods utilize active sampling strategies ("grab samples") for precise PFAS quantitation, here we evaluate the efficacy of low-cost passive sampling devices (Solid Phase Adsorption Toxin Tracking, or SPATTs) for spatial and temporal PFAS assessment of aquatic systems. For this study, passive samplers were initially deployed in North Carolina along the Cape Fear River during the summer and fall of 2016 and 2017.

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Article Synopsis
  • Lithium-ion batteries (LiBs) are essential for clean energy, but they now use a group of contaminants called bis-perfluoroalkyl sulfonimides (bis-FASIs), which are toxic and mobile like other harmful PFAS substances.
  • Research shows that the environmental levels of bis-FASIs near manufacturing sites and their harmful effects are similar to those from banned PFAS, highlighting a significant concern for the clean energy sector.
  • The study emphasizes the need to evaluate the environmental implications of clean energy initiatives to ensure they don't inadvertently increase the release of pollutants, counteracting benefits of reduced carbon emissions.
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  • The study investigates the relationship between left atrial strain reservoir (LAS) and the recurrence of atrial fibrillation (AF) after pulmonary vein isolation (PVI) in 132 patients.
  • Results show that lower LAS is significantly associated with a higher risk of AF recurrence, with a critical cut-off value identified at 31.4%.
  • The findings suggest that measuring LAS can help in assessing the risk of AF recurrence in patients undergoing PVI, enhancing patient management strategies.
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Aims: For patients with symptomatic drug-refractory atrial fibrillation (AF), catheter ablation to achieve rhythm control is an important therapeutic option. The atrial mechanical dispersion measured as standard deviation of the time to peak strain (SD-TPS) is associated with the risk of AF recurrence following catheter ablation.

Methods: The study cohort prospectively enrolled n = 132 consecutive patients with paroxysmal (n = 88) or persistent AF (n = 44) presenting for de novo pulmonary vein isolation (PVI) and followed for 1 year.

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Compost is widely used in agriculture as fertilizer while providing a practical option for solid municipal waste disposal. However, compost may also contain per- and polyfluoroalkyl substances (PFAS), potentially impacting soils and leading to PFAS entry into food chains and ultimately human exposure risks via dietary intake. This study examined how compost affects the bioavailability and uptake of eight PFAS (two ethers, three fluorotelomer sulfonates, and three perfluorosulfonates) by lettuce (Lactuca sativa) grown in commercial organic compost-amended, PFAS spiked soils.

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Muscle wasting diseases, such as cancer cachexia and age-associated sarcopenia, have a profound and detrimental impact on functional independence, quality of life, and survival. Our understanding of the underlying mechanisms is currently limited, which has significantly hindered the development of targeted therapies. In this study, we explored the possibility that the streptococcal quorum sensing peptide Competence Stimulating Peptide 7 (CSP-7) might be a previously unidentified contributor to clinical muscle wasting.

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Background: Cryptococcosis and cryptococcal meningitis, caused by infections, lead to approximately 180,000 deaths per year, primarily in developing countries. Individuals with compromised immune systems, e.g.

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Background: A fluorochemical facility near Fayetteville, North Carolina, emitted per- and polyfluoroalkyl ether acids (PFEAs), a subgroup of per- and polyfluoroalkyl substances (PFAS), to air.

Objective: Analyze PFAS in private wells near the facility and in blood from well users to assess relationships between PFEA levels in water and serum.

Methods: In 2019, we recruited private well users into the GenX Exposure Study and collected well water and blood samples.

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Background: The use of urinary sodium to guide diuretics in acute heart failure is recommended by experts and the most recent European Society of Cardiology guidelines. However, there are limited data to support this recommendation. The ENACT-HF study (Efficacy of a Standardized Diuretic Protocol in Acute Heart Failure) investigated the feasibility and efficacy of a standardized natriuresis-guided diuretic protocol in patients with acute heart failure and signs of volume overload.

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  • Anion exchange (IX) is an effective method for removing PFAS from water, and this research focused on using small-scale tests to predict PFAS removal in larger systems.
  • Key goals included evaluating how crushing IX resin affects its properties, understanding the influence of initial PFAS concentrations on their removal, and identifying the primary factor that limits the rate of PFAS uptake.
  • The study found that PFAS uptake was consistent across a range of initial concentrations, and that factors like hydraulic loading rates significantly affect removal efficiency, providing insights for scaling up this treatment method from lab tests to full-scale applications.
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Pharmacologic reduction in heart rate with beta-blockers (BB) or ivabradine is associated with improved survival in heart failure (HF) with sinus rhythm. We analyzed the association of different heart rate-reducing drug treatments on outcomes in HF outpatients. Consecutive patients with HF in sinus rhythm referred to a specialized tertiary service were prospectively enrolled from August 2015 until March 2018.

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Research on per- and polyfluoroalkyl substances (PFAS) frequently incorporates organofluorine measurements, particularly because they could support a class-based approach to regulation. However, standardized methods for organofluorine analysis in a broad suite of matrices are currently unavailable, including a method for extractable organofluorine (EOF) measured using combustion ion chromatography (CIC). Here, we report the results of an international interlaboratory comparison.

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To estimate half-lives for novel fluoroethers, the GenX Exposure Study obtained two serum measurements for per- and polyfluoroalkyl substances (PFAS) for 44 participants of age 12-86 years from North Carolina, collected 5 and 11 months after fluoroether discharges into the drinking water source were controlled. The estimated half-lives for these compounds were 127 days (95% confidence interval (95% CI) = 86, 243 days) for perfluorotetraoxadecanoic acid (PFO4DA), 296 days for Nafion byproduct 2 (95% CI = 176, 924 days), and 379 days (95% CI = 199, 3870 days) for perfluoro-3,5,7,9,11-pentaoxadodecanoic acid (PFO5DoA). Using these estimates and the literature values, a model was built that predicted PFAS half-lives using structural properties.

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In 2017, people living in New Hanover County, North Carolina, learned that for ∼40 years they were unknowingly exposed to per- and polyfluoroalkyl substances (PFAS) through drinking water sourced by the Cape Fear River. Using data from the GenX Exposure Study, which measured serum PFAS levels in county residents, we aimed to understand questionnaire-measured factors associated with serum PFAS levels. Because most residents were served by the same municipal water source, we focused on surrogate factors of drinking water exposure that may contribute to variability in PFAS levels.

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Per- and polyfluoroalkyl substances (PFAS) are widely used anthropogenic chemicals. Because of the strength of the carbon-fluorine bond, PFAS are not destroyed in typical water treatment processes. Sulfate (SO) and hydroxyl (OH) radicals can oxidize some PFAS, but the behavior of per- and polyfluoroalkyl ether acids (PFEAs) in processes involving SO and OH is poorly understood.

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