Showing papers in "Environmental Science and Technology Letters in 2016"

Detection of Poly- and Perfluoroalkyl Substances (PFASs) in U.S. Drinking Water Linked to Industrial Sites, Military Fire Training Areas, and Wastewater Treatment Plants.

Abstract: Drinking water contamination with poly- and perfluoroalkyl substances (PFASs) poses risks to the developmental, immune, metabolic, and endocrine health of consumers. We present a spatial analysis of 2013–2015 national drinking water PFAS concentrations from the U.S. Environmental Protection Agency’s (US EPA) third Unregulated Contaminant Monitoring Rule (UCMR3) program. The number of industrial sites that manufacture or use these compounds, the number of military fire training areas, and the number of wastewater treatment plants are all significant predictors of PFAS detection frequencies and concentrations in public water supplies. Among samples with detectable PFAS levels, each additional military site within a watershed’s eight-digit hydrologic unit is associated with a 20% increase in PFHxS, a 10% increase in both PFHpA and PFOA, and a 35% increase in PFOS. The number of civilian airports with personnel trained in the use of aqueous film-forming foams is significantly associated with the detection of ...

The Critical Need for Increased Selectivity, Not Increased Water Permeability, for Desalination Membranes

Abstract: Desalination membranes are essential for the treatment of unconventional water sources, such as seawater and wastewater, to alleviate water scarcity. Promising research efforts on novel membrane materials may yield significant performance gains over state-of-the-art thin-film composite (TFC) membranes, which are constrained by the permeability–selectivity trade-off. However, little guidance currently exists on the practical impact of such performance gains, namely enhanced water permeability or enhanced water–solute selectivity. In this critical review, we first discuss the performance of current TFC membranes. We then highlight and provide context for recent module-scale modeling studies that have found limited impact of increased water permeability on the efficiency of desalination processes. Next we cover several important examples of water treatment processes in which inadequate membrane selectivity hinders process efficacy. We conclude with a brief discussion of how the need for enhanced selectivity ...

Legacy and Emerging Perfluoroalkyl Substances Are Important Drinking Water Contaminants in the Cape Fear River Watershed of North Carolina

Abstract: Long-chain per- and polyfluoroalkyl substances (PFASs) are being replaced by short-chain PFASs and fluorinated alternatives. For ten legacy PFASs and seven recently discovered perfluoroalkyl ether carboxylic acids (PFECAs), we report (1) their occurrence in the Cape Fear River (CFR) watershed, (2) their fate in water treatment processes, and (3) their adsorbability on powdered activated carbon (PAC). In the headwater region of the CFR basin, PFECAs were not detected in raw water of a drinking water treatment plant (DWTP), but concentrations of legacy PFASs were high. The U.S. Environmental Protection Agency’s lifetime health advisory level (70 ng/L) for perfluorooctanesulfonic acid and perfluorooctanoic acid (PFOA) was exceeded on 57 of 127 sampling days. In raw water of a DWTP downstream of a PFAS manufacturer, the mean concentration of perfluoro-2-propoxypropanoic acid (PFPrOPrA), a replacement for PFOA, was 631 ng/L (n = 37). Six other PFECAs were detected, with three exhibiting chromatographic peak ar...

Faradaic Reactions in Water Desalination by Batch-Mode Capacitive Deionization

Abstract: Non-Faradaic (ion electrosorption) and Faradaic (oxidation–reduction) effects in a batch-mode capacitive deionization (CDI) system were investigated, with results showing that both effects were enhanced with an increase in charging voltage (0.5–1.5 V). Significant concentrations of hydrogen peroxide (H2O2) were observed with the generation of H2O2 initiated by cathodic reduction of O2 with subsequent consumption occurring as a result of cathodic reduction of H2O2. A kinetic model of the Faradaic processes was developed and found to satisfactorily describe the variation in the steady-state concentration of H2O2 generated over a range of CDI operating conditions. Significant pH fluctuations were observed at higher charging voltages. While the occurrence of Faradaic reactions may well contribute to pH fluctuations and deterioration of electrode stability and performance, the presence of H2O2 could provide the means of inducing disinfection or trace contaminant degradation provided H2O2 could be effectively a...

Wood-Derived Black Carbon (Biochar) as a Microbial Electron Donor and Acceptor

Abstract: Research on the environmental impacts of black carbon has focused largely on sorption. Besides being a strong geosorbent, black carbon is redox-active and may facilitate abiotic and microbial transformation. Using a wood-derived black carbon (biochar) and the bacterium Geobacter metallireducens (GS-15), we showed that air-oxidized biochar served as an electron acceptor to enable acetate oxidation, and that chemically or biotically reduced biochar served as an electron donor for nitrate reduction. The bioavailable (to GS-15) electron storage capacities (ESCs) of the biochar, estimated on the basis of acetate oxidation and nitrate reduction, were 0.85 and 0.87 mmol e–/g, respectively, comparable to the ESCs of humic substances and other biochars measured electrochemically. We propose that black carbon should be regarded as a rechargeable reservoir of bioavailable electrons in anaerobic environments. The redox cycling of biochar in natural and engineered systems and its impact on microbial processes and cont...

Current Browning of Surface Waters Will Be Further Promoted by Wetter Climate

Abstract: Browning of surface waters because of increasing terrestrial dissolved organic carbon (OC) concentrations is a concern for drinking water providers and can impact land carbon storage. We show that positive trends in OC in 474 streams, lakes, and rivers in boreal and subarctic ecosystems in Norway, Sweden, and Finland between 1990 and 2013 are surprisingly constant across climatic gradients and catchment sizes (median, +1.4% year–1; interquartile range, +0.8–2.0% year–1), implying that water bodies across the entire landscape are browning. The largest trends (median, +1.7% year–1) were found in regions impacted by strong reductions in sulfur deposition, while subarctic regions showed the least browning (median, +0.8% year–1). In dry regions, precipitation was a strong and positive driver of OC concentrations, declining in strength moving toward high rainfall sites. We estimate that a 10% increase in precipitation will increase mobilization of OC from soils to freshwaters by at least 30%, demonstrating the ...

Assessing and Reducing the Toxicity of 3D-Printed Parts

Abstract: 3D printing is gaining popularity by providing a tool for fast, cost-effective, and highly customizable fabrication. However, little is known about the toxicity of 3D-printed objects. In this work, we assess the toxicity of printed parts from two main classes of commercial 3D printers, fused deposition modeling and stereolithography. We assessed the toxicity of these 3D-printed parts using zebrafish (Danio rerio), a widely used model organism in aquatic toxicology. Zebrafish embryos were exposed to 3D-printed parts and monitored for rates of survival, hatching, and developmental abnormalities. We found that parts from both types of printers were measurably toxic to zebrafish embryos, with STL-printed parts significantly more toxic than FDM-printed parts. We also developed a simple post-printing treatment (exposure to ultraviolet light) that largely mitigates the toxicity of the STL-printed parts. Our results call attention to the need for strategies for the safe disposal of 3D-printed parts and printer wa...

Liquid water: Ubiquitous contributor to aerosol mass

Abstract: Aerosol liquid water (ALW) is a ubiquitous component of atmospheric aerosol and influences particle chemistry, visibility, human health, and regional climate. The global abundance and spatial patterns in ALW mass concentrations and its fractional contribution to total particle mass are not routinely documented. We estimate lower-bound ALW mass concentrations at locations and time periods of aerosol mass spectrometer (AMS) field campaigns using speciated ion measurements, meteorology from the Climate Forecast System Reanalysis, and thermodynamic predictions from ISORROPIA version 2.1. The contribution of water by organic compounds is estimated using κ-Kohler theory. Field campaign-specific patterns suggest that ALW mass is largest in urban and urban downwind areas, and that of growth factors is largest in rural areas. The highest average ALW mass concentration is estimated for the AMS study in Beijing and the highest mass fraction for rural Hyytiala. A more robust understanding of ALW is critical for devel...

High-Molecular Weight Dimer Esters Are Major Products in Aerosols from α-Pinene Ozonolysis and the Boreal Forest

Abstract: This study investigates the contribution of high-molecular weight dimer esters to laboratory-generated α-pinene gas- and particle-phase secondary organic aerosol (SOA) and particulate matter (PM) collected at the Nordic boreal forest site of Hyytiala, Finland. Laboratory flow reactor experiments (25 °C) show that dimer esters from ozonolysis of α-pinene contribute between 5 and 16% of the freshly formed α-pinene particle-phase SOA mass. An increased level of formation is observed at a higher relative humidity of ∼40%, and the presence of a hydroxyl radical (OH) scavenger is shown to affect the formation of dimer esters. Of the 28 dimer esters identified in laboratory α-pinene SOA, 15 are also observed in ambient PM samples, contributing between 0.5 and 1.6% of the total PM1. The observed esters show good correlation with known α-pinene SOA tracers in collected PM samples. This work reveals an, until now, unrecognized contribution of dimer esters from α-pinene oxidation to boreal forest PM.

Source attribution of poly- and perfluoroalkyl substances (PFASs) in surface waters from Rhode Island and the New York Metropolitan Area.

Abstract: Exposure to poly- and perfluoroalkyl substances (PFASs) has been associated with adverse health effects in humans and wildlife. Understanding pollution sources is essential for environmental regulation, but source attribution for PFASs has been confounded by limited information about industrial releases and rapid changes in chemical production. Here we use principal component analysis (PCA), hierarchical clustering, and geospatial analysis to understand source contributions to 14 PFASs measured across 37 sites in the northeastern United States in 2014. PFASs are significantly elevated in urban areas compared to rural sites except for perfluorobutanesulfonate, N-methyl perfluorooctanesulfonamidoacetic acid, perfluoroundecanate, and perfluorododecanate. The highest PFAS concentrations across sites were those of perfluorooctanate (PFOA, 56 ng L−1) and perfluorohexanesulfonate (PFHxS, 43 ng L−1), and perfluorooctanesulfonate (PFOS) levels are lower than earlier measurements of U.S. surface waters. PCA and clu...

Does Hydrophilic Polydopamine Coating Enhance Membrane Rejection of Hydrophobic Endocrine-Disrupting Compounds?

Abstract: Endocrine-disrupting compounds (EDCs), an important class of micropollutants with potent adverse health effects, are generally poorly rejected by traditional thin film composite polyamide membranes and thus pose significant risks in membrane-based water reclamation. We hypothesize that membrane rejection of hydrophobic EDCs can be enhanced by a hydrophilic surface coating. Using polydoamine (PDA) as a model hydrophilic coating layer, the PDA-coated NF90 membrane experienced an up to 75% reduction in the passage of bisphenol A compared to the control (NF90 without coating). Meanwhile, we also observed a systematic increase in the level of rejection of three hydrophobic parabens with an increase in PDA coating time. In contrast, there were no systematic changes in the rejection of neutral hydrophilic polyethylene glycol, which suggests that the enhanced rejection of EDCs was due to weakened EDC–membrane hydrophobic interaction. Further sorption tests revealed that the hydrophilic PDA coating could effective...

Methane Production in Oxic Lake Waters Potentially Increases Aquatic Methane Flux to Air

Abstract: Active methane production in oxygenated lake waters challenges the long-standing paradigm that microbial methane production occurs only under anoxic conditions and forces us to rethink the ecology and environmental dynamics of this powerful greenhouse gas. Methane production in the upper oxic water layers places the methane source closer to the air–water interface, where convective mixing and microbubble detrainment can lead to a methane efflux higher than that previously assumed. Microorganisms may produce methane in oxic environments by being equipped with enzymes to counteract the effects of molecular oxygen during methanogenesis or using alternative pathways that do not involve oxygen-sensitive enzymes. As this process appears to be influenced by thermal stratification, water transparency, and primary production, changes in lake ecology due to climate change will alter methane formation in oxic water layers, with far-reaching consequences for methane flux and climate feedback.

Gaseous Ammonia Emissions from Coal and Biomass Combustion in Household Stoves with Different Combustion Efficiencies

Abstract: This study reports on the emission characteristics of NH3 from coal and biomass combustion in the household stoves. The average NH3 emission factors (EFs) for burning 13 coal and four biomass briquette samples in a traditional heating stove were 1.01 and 0.95 mg/g, respectively, whereas the biomass EF in a traditional cooking stove was 0.96 mg/g. These NH3 EFs did not present significant differences and were not well-correlated with the tested fuel properties. However, the modified combustion efficiency (MCE) appeared to be well-correlated with the NH3 EFs measured from various fuel–stove combinations. For the same fuel samples, the advanced heating stove with a high MCE had a much lower average NH3 EF of 0.13 mg/g. Our findings indicate that household combustion may be a significant NH3 emission source in developing countries such as China, and demonstrate that utilizing improved combustion technologies is an effective method for reducing these emissions.

Rare-Earth separation using bacteria

Abstract: The rare-earth elements are critical to many green energy technologies but are difficult to separate from one another because of their chemical similarity. We demonstrate an alternative, biogenic method based on the adsorption of lanthanide to the bacterium Roseobacter sp. AzwK-3b, immobilized on an assay filter, followed by subsequent desorption as a function of pH. The elution desorption data suggest that the basicity of the individual lanthanides is important in determining their desorption behavior. It is found that via preprotonation of the bacteria it is possible to concentrate a solution of equal concentrations of each lanthanide to nearly 50% of the three heaviest lanthanides (Tm, Lu, and Yb) in just two passes. This surpasses existing industrial practice. The findings suggest that there is an opportunity to harness the diversity of bacterial surface chemistry to separate and recover technologically important rare-earth metals in an environmentally benign manner.

In Situ Silver Decoration on Graphene Oxide-Treated Thin Film Composite Forward Osmosis Membranes: Biocidal Properties and Regeneration Potential

Abstract: The surfaces of thin film composite (TFC) forward osmosis (FO) membranes were modified by in situ formation of silver nanoparticles (AgNPs) in the presence and absence of graphene oxide (GO) nanosheets to impart biocidal properties to the membranes. The abundance of oxygen-containing functional groups in GO makes it suitable for anchoring Ag+ ions and governing the size, shape, and distribution of AgNPs. The presence of GO resulted in the formation of smaller and uniformly distributed AgNPs as well as increased silver loading, higher stability, and enhanced ion release control. Membranes modified by both GO and Ag exhibited improved (98%) bacterial inactivation when compared to that of only Ag-modified (80%) or GO-modified membranes (50%). After release of Ag ion from GO-Ag-modified membranes for 7 days, AgNP regeneration was conducted in a manner identical to the in situ Ag formation procedure. After regeneration, the membrane regained nearly all of its antibacterial properties and 75% of its initial sil...

Origin of Hexavalent Chromium in Drinking Water Wells from the Piedmont Aquifers of North Carolina

Abstract: Hexavalent chromium [Cr(VI)] is a known pulmonary carcinogen Recent detection of Cr(VI) in drinking water wells in North Carolina has raised public concern about contamination of drinking water wells by nearby coal ash ponds Here we report, for the first time, the prevalence of Cr and Cr(VI) in drinking water wells from the Piedmont region of central North Carolina, combined with a geochemical analysis to determine the source of the elevated Cr(VI) levels We show that Cr(VI) is the predominant species of dissolved Cr in groundwater and elevated levels of Cr and Cr(VI) are found in wells located both near and far (>30 km) from coal ash ponds The geochemical characteristics, including the overall chemistry, boron to chromium ratios, and strontium isotope (87Sr/86Sr) variations in groundwater with elevated Cr(IV) levels, are different from those of coal ash leachates Alternatively, the groundwater chemistry and Sr isotope variations are consistent with water–rock interactions as the major source for Cr(

Metformin and Other Pharmaceuticals Widespread in Wadeable Streams of the Southeastern United States

Abstract: Pharmaceutical contaminants are growing aquatic-health concerns and largely attributed to wastewater treatment facility (WWTF) discharges. Five biweekly water samples from 59 small Piedmont (United States) streams were analyzed for 108 pharmaceuticals and degradates using high-performance liquid chromatography and tandem mass spectrometry. The antidiabetic metformin was detected in 89% of samples and at 97% of sites. At least one pharmaceutical was detected at every site (median of 6, maximum of 45), and several were detected at ≥10% of sites at concentrations reported to affect multiple aquatic end points. Maximal cumulative (all detected compounds) concentrations per site ranged from 17 to 16000 ng L–1. Watershed urbanization, water table depth, soil thickness, and WWTF metrics correlated significantly with in-stream pharmaceutical contamination. Comparable pharmaceutical concentrations and detections at sites with and without permitted wastewater discharges demonstrate the importance of non-WWTF source...

Legionella DNA Markers in Tap Water Coincident with a Spike in Legionnaires’ Disease in Flint, MI

Abstract: Two clusters of Legionnaires’ disease occurred in Flint, MI, subsequent to switching to a corrosive potable water source from April 2014 to October 2015. We hypothesized that the interrupted corrosion control and associated release of iron, nutrients, and depleted chlorine residual in the distribution system would lead to high levels of Legionella. A tap water survey conducted throughout Flint in August and October 2015 confirmed Legionella pneumophila in two hospitals (mean of 1890 ± 2220 gene copy numbers/mL, 48% positivity), but not small single-story buildings. The hospitals frequently had optimal Legionella growth temperatures and were located in high-water age zones of the distribution system (3 to >6 days). Relatively high concentrations of iron were present (mean of 51.0 ± 37.2 ppb), and Cl2 residual was sporadic (mean of 0.700 ± 0.775 mg/L) throughout the Flint distribution system. This study addresses knowledge gaps linking legionellosis outbreaks to changes in municipal water quality and distri...

Bacterial Nanocellulose Aerogel Membranes: Novel High-Porosity Materials for Membrane Distillation

Abstract: We fabricated, characterized, and tested novel fibrous aerogel membranes in direct contact membrane distillation (MD) to elucidate the effects of a model high-porosity membrane material on MD performance. Unsupported bacterial nanocellulose aerogels exhibit higher porosity, thinner fibers, and lower bulk thermal conductivity than any previously reported MD materials. Modeling and experiments demonstrate that these material properties confer significantly higher intrinsic membrane permeability and thermal efficiency than symmetric PVDF phase inversion membranes with lower porosity. Development of macroporous fibrous membranes with aerogel-like porosity and thermal conductivity (>98% and <0.03 W m–1 K–1, respectively) in thinner-film formats may further improve MD flux.

Observation of Fullerene Soot in Eastern China

Abstract: This work reports the observation of a series of fullerene ions, indicating the occurrence of fullerene soot (FS) in ambient air for the first time using an Aerodyne soot particle-aerosol mass spectrometer (SP-AMS) deployed in eastern China. We found the distribution of these ions showed a pattern almost identical with that of an Alfa Aesar FS standard. Although the SP-AMS may provide only a semiquantitative measurement of the FS, the measured concentrations can still reflect the temporal variations of airborne fullerenes. Combining results from factor analyses and meteorological data, we identified the petrochemical plants situated northeast of the site as the major source responsible for the FS-like ions. Our findings indicate the general presence of FS in ambient air, especially in oil and gas production regions. The SP-AMS technique may offer new insights into characterizing fullerene-related species in other environmental samples, as well.

Active H2 Harvesting Prevents Methanogenesis in Microbial Electrolysis Cells

Abstract: Undesired H2 sinks, including methanogenesis, are a serious issue faced by microbial electrolysis cells (MECs) for high-rate H2 production. Different from current top-down approaches to methanogenesis inhibition that showed limited success, this study found active harvesting can eliminate the source (H2) from all H2 consumption mechanisms via rapid H2 extraction using a gas-permeable hydrophobic membrane and vacuum. Active harvesting completely prevented CH4 production and led to H2 yields (2.62–3.39 mol of H2/mol of acetate) much higher than that of the control using traditional spontaneous release (0.79 mol of H2/mol of acetate). In addition, existing CH4 production in the control MEC was stopped once the switch to active H2 harvesting was made. Active harvesting also increased current density by 36%, which increased operation efficiency and facilitated organic removal. Energy quantification shows the process was energy-positive, as the H2 energy produced via active harvesting was 220 ± 10% of external ...

Occurrence of Host-Associated Fecal Markers on Child Hands, Household Soil, and Drinking Water in Rural Bangladeshi Households

Abstract: We evaluated whether provision and promotion of improved sanitation hardware (toilets and child feces management tools) reduced rotavirus and human fecal contamination of drinking water, child hands, and soil among rural Bangladeshi compounds enrolled in a cluster-randomized trial. We also measured host-associated genetic markers of ruminant and avian feces. We found evidence of widespread ruminant and avian fecal contamination in the compound environment; non-human fecal marker occurrence scaled with animal ownership. Strategies for controlling non-human fecal waste should be considered when designing interventions to reduce exposure to fecal contamination in low-income settings. Detection of a human-associated fecal marker and rotavirus was rare and unchanged by provision and promotion of improved sanitation to intervention compounds. The sanitation intervention reduced ruminant fecal contamination in drinking water and general (non-host specific) fecal contamination in soil but overall had limited effe...

Rapid Oxidation of Skin Oil by Ozone

Abstract: The reaction of gas-phase ozone with human skin oil has been studied at room temperature. Skin oil was exposed to ozone at mixing ratios similar to those in the ambient environment and then analyzed for condensed-phase products using direct analysis in real time mass spectrometry (DART-MS). Prior to ozone exposure, skin oil gives rise to prominent mass spectral signals indicative of highly unsaturated alkenes, sterols, triglycerides, long-chain fatty acids, pyroglutamic acid, and probably waxy esters. Upon oxidation with 50 ppb ozone for 90 min, there is a rapid loss of alkene, fatty acid, and triglyceride signals resulting from efficient multiphase ozonolysis. Oxygenated products, including a variety of carboxylic acids, are identified via studies with pure compounds present in skin oil, i.e., squalene, cholesterol, and triolein. The chemistry is rapid, occurring on time scales of tens of minutes, implying that these highly oxygenated reaction products are always present on human skin both indoors and ou...

Improving the Energy Efficiency of Stoves To Reduce Pollutant Emissions from Household Solid Fuel Combustion in China

Abstract: Emissions of air pollutants from household solid fuel combustion in low-efficiency stoves have serious negative impacts on human health and air quality in China. This study compares the thermal efficiency (TE) and emissions from solid fuel combustion in a newly developed under-fire heating stove and a typical traditional over-fire heating stove. The average TEs for burning all tested fuel types (semi-coke, anthracite, briquette, bituminous, lignite, and biomass) were 83 and 42% for the new stove and the traditional stove, respectively. The new stove was effective in reducing CO2 and pollutant emissions per unit energy delivered to a radiator. The average reductions were ∼50% for CO2, 79% for PM2.5, 95% for EC, 85% for benzo[a]pyrene equivalent carcinogenic potency, and 66% for eight selected toxic elements (Pb, Cu, Sb, Cd, As, Ag, Se, and Ni) in PM2.5. Improvements in stove technology are demonstrated as a practical approach for improving TE and reducing emissions of hazardous pollutants and CO2.

Isoprene-Derived Secondary Organic Aerosol Induces the Expression of Oxidative Stress Response Genes in Human Lung Cells

Abstract: Atmospheric oxidation of isoprene in the presence of acidic sulfate aerosol leads to secondary organic aerosol (SOA) that substantially contributes to the mass of outdoor fine particulate matter (PM2.5). The potential adverse health effects resulting from exposure to this PM type are largely unknown. Isoprene-derived epoxides, isoprene epoxydiols (IEPOX) and methacrylic acid epoxide (MAE), have recently been identified as key gaseous intermediates leading to isoprene SOA formation through acid-catalyzed multiphase chemistry. Altered expression of oxidative stress-associated genes was assessed from exposure to laboratory-generated IEPOX- and MAE-derived SOA in an in vitro model of human airway epithelial cells (BEAS-2B). Exposure to SOA filter extracts is associated with an increased level of expression of oxidative stress response genes in human lung cells under noncytotoxic conditions, with MAE-derived SOA extracts showing greater potency than IEPOX-derived SOA extracts. Our findings highlight the import...

A High-Precision Passive Air Sampler for Gaseous Mercury

Abstract: Passive air samplers (PASs) provide an opportunity to improve the spatial range and resolution of gaseous mercury (Hg) measurements. Here, we propose a sampler design that combines a sulfur-impregnated activated carbon sorbent, a Radiello diffusive barrier, and a protective shield for outdoor deployments. The amount of gaseous Hg taken up by the sampler increased linearly with time for both an 11-week indoor (r2 = 0.990) and 12-month outdoor (r2 = 0.996) deployment, yielding sampling rates of 0.158 ± 0.008 m3 day–1 indoors and 0.121 ± 0.005 m3 day–1 outdoors. These sampling rates are close to modeled estimates of 0.166 m3 day–1 indoors and 0.129 m3 day–1 outdoors. Replicate precision is better than for all previous PASs for gaseous Hg, especially during outdoor deployments (2 ± 1.3%). Such precision is essential for discriminating the relatively small concentration variations occurring at background sites. Deployment times for obtaining reliable time-averaged atmospheric gaseous Hg concentrations range fr...

Beyond the Pipeline: Assessing the Efficiency Limits of Advanced Technologies for Solar Water Disinfection

Abstract: This critical review analyzes and compares the efficiency of select technologies that harness solar energy for point-of-use water disinfection, including photocatalysts, photosensitizing chromophores, UVC light-emitting diodes, and visible-to-UVC upconversion phosphors. The volume rate of water that each material can treat to achieve 99% inactivation of model microorganisms, given the same sunlight exposure, was estimated on the basis of literature data and theoretical predictions, in the context of both currently reported efficiencies and theoretical thermodynamic maximum efficiencies. Each material is further critiqued in terms of the spectral match with sunlight, quantum efficiency, and the relative strength of the resulting disinfecting agent such as hydroxyl radicals, singlet oxygen, and UVC radiation. This review emphasizes critical needs for disinfection strategies that can efficiently inactivate more than one type of microorganism. In addition, the approach described herein can guide future resear...

Preliminary Associations between the Detection of Perfluoroalkyl Acids (PFAAs) in Drinking Water and Serum Concentrations in a Sample of California Women

Abstract: This study compared detection of perfluoroalkyl acids (PFAAs) in public drinking water with PFAA serum concentrations for 1566 California women. PFAA occurrence in drinking water from U.S. EPA’s third Unregulated Contaminant Monitoring Rule (UCMR3) database was linked by residential zip code to study participants. Detectable water concentrations of perfluorooctanoic acid (PFOA) ranged from 0.020 to 0.053 μg/L and of perfluorooctanesulfonic acid (PFOS) from 0.041 to 0.156 μg/L. Forty percent of detectable concentrations exceeded the 2016 Health Advisory Level of 0.07 μg/L for combined PFOA and PFOS concentrations. Serum concentrations of PFOS and PFOA significantly differed between participants with and without detectable measures of these compounds in water (Wilcoxon P ≤ 0.0007). Median serum concentrations of PFOS and PFOA were 29% and 38% higher, respectively, among those with detectable levels in water compared to those without detectable levels. Validation of this approach and replication of these res...

TiO2 Nanotube Arrays Modified Titanium: A Stable, Scalable, and Cost-Effective Bioanode for Microbial Fuel Cells

Abstract: Titanium has been widely used as a dimensionally stable anode in the electrolysis industry because of its excellent corrosion resistance, conductivity, and scalability. However, because of its poor biocompatibility and poor performance as a bioanode, it has drawn little attention in the field of microbial fuel cells (MFCs). This study reports an efficient way to convert a titanium electrode into a high-performance anode for MFCs, in situ growth of titanium dioxide nanotubes (TNs) on its surface. After TN modification, the titanium surface became rougher, more hydrophilic, and more conducive for anodic biofilm formation. The maximal current density achieved on this TN-modified titanium electrode was 12.7 A m–2, which was 190-fold higher than that of the bare titanium electrode and even higher than that of the most commonly used carbon felt electrode. Therefore, the high conductivity, corrosion resistance, and current density make the TN-modified titanium electrode a promising and scalable anode for MFCs.

SO2 Uptake on Oleic Acid: A New Formation Pathway of Organosulfur Compounds in the Atmosphere

Abstract: Organosulfates are tracers for secondary organic aerosol (SOA) formation. We propose a new mechanism of organosulfur product formation in the atmosphere, in which sulfur dioxide (SO2) reacts directly with alkenes. The experiments were conducted at the gas–liquid interface with a coated-wall flow tube reactor. It was shown, for the first time, that SO2 reacts efficiently with the unsaturated bond in oleic acid under atmospheric conditions (without ozone), leading to the formation of C9 and C18 organosulfur products. The associated uptake coefficients were in excess of 10–6, decreasing with initial SO2 concentration and increasing with humidity. These results might explain a fraction of organosulfur products detected in atmospheric particles. This work tends to elucidate the role of organosulfates’ interfacial chemistry as a potentially unrecognized pathway for their contribution to SOA formation; however, it remains to be determined how significant this pathway is to the overall organosulfate abundances me...