Showing papers in "Environmental Science & Technology in 2005"
TL;DR: Conventional treatment would have low removal of many EDC/PPCPs, while addition of PAC and/or ozone could substantially improve their removals, and existing strategies that predict relative removal of herbicides, pesticides, and other organic pollutants can be directly applied.
Abstract: The potential occurrence of endocrine-disrupting compounds (EDCs) as well as pharmaceuticals and personal care products (PPCPs) in drinking water supplies raises concern over the removal of these compounds by common drinking water treatment processes. Three drinking water supplies were spiked with 10 to 250 ng/L of 62 different EDC/PPCPs; one model water containing an NOM isolate was spiked with 49 different EDC/PPCPs. Compounds were detected by LC/MS/MS or GC/MS/MS. These test waters were subjected to bench-scale experimentation to simulate individual treatment processes in a water treatment plant (WTP). Aluminum sulfate and ferric chloride coagulants or chemical lime softening removed some polyaromatic hydrocarbons (PAHs) but removed 98% of GC/MS/MS compounds (more volatile) and 10% to >95% of LC/MS/MS compounds (more polar); higher PAC dosages improved EDC/PPCP removal. EDC/PPCP per...
1,433 citations
TL;DR: Results provide new insight into the redox reactivity of DOM and have implications for the application of fluorescence spectroscopy as a tool to characterize DOM.
Abstract: Excitation−emission matrixes (EEMs) of 379 dissolved organic matter (DOM) samples from diverse aquatic environments were modeled by parallel factor analysis (PARAFAC). Thirteen components likely representing groups of similarly fluorescing moieties were found to explain the variation in this data set. Seven of the thirteen components were identified as quinone-like based on comparison of their excitation and emission spectra to spectra of model quinones. These quinone-like fluorophores were found to vary in redox state and degree of conjugation. Two components were identified as amino acid-like based on comparison to tyrosine and tryptophan fluorescence spectra. The other four components are not yet associated with any class of molecules. The quinone-like fluorophores account for about 50% of the fluorescence for every sample analyzed, showing that quinone-like fluorophores are an important and ubiquitous fluorescing moiety and in natural waters. Further, the distribution of the quinone-like fluorophores ...
1,389 citations
TL;DR: It is advocated that the use of generic organic carbon-water distribution coefficients in the risk assessment of organic compounds is not warranted and that bioremediation endpoints could be evaluated on the basis of freely dissolved concentrations instead of total concentrations in sediment/soil.
Abstract: Evidence is accumulating that sorption of organic chemicals to soils and sediments can be described by “dual-mode sorption”: absorption in amorphous organic matter (AOM) and adsorption to carbonaceous materials such as black carbon (BC), coal, and kerogen, collectively termed “carbonaceous geosorbents” (CG). Median BC contents as a fraction of total organic carbon are 9% for sediments (number of sediments, n ≈ 300) and 4% for soils (n = 90). Adsorption of organic compounds to CG is nonlinear and generally exceeds absorption in AOM by a factor of 10−100. Sorption to CG is particularly extensive for organic compounds that can attain a more planar molecular configuration. The CG adsorption domain probably consists of surface sites and nanopores. In this review it is shown that nonlinear sorption to CG can completely dominate total sorption at low aqueous concentrations (<10-6 of maximum solid solubility). Therefore, the presence of CG can explain (i) sorption to soils and sediments being up to 2 orders of m...
1,339 citations
TL;DR: Carbon nanomaterials with different geometric structures exhibit quite different cytotoxicity and bioactivity in vitro, although they may not be accurately reflected in the comparative toxicity in vivo.
Abstract: A cytotoxicity test protocol for single-wall nanotubes (SWNTs), multi-wall nanotubes (with diameters ranging from 10 to 20 nm, MWNT10), and fullerene (C60) was tested. Profound cytotoxicity of SWNTs was observed in alveolar macrophage (AM) after a 6-h exposure in vitro. The cytotoxicity increases by as high as approximately 35% when the dosage of SWNTs was increased by 11.30 microg/cm2. No significant toxicity was observed for C60 up to a dose of 226.00 microg/cm2. The cytotoxicity apparently follows a sequence order on a mass basis: SWNTs > MWNT10 > quartz > C60. SWNTs significantly impaired phagocytosis of AM at the low dose of 0.38 microg/cm2, whereas MWNT10 and C60 induced injury only at the high dose of 3.06 microg/cm2. The macrophages exposed to SWNTs or MWNT10 of 3.06 microg/cm2 showed characteristic features of necrosis and degeneration. A sign of apoptotic cell death likely existed. Carbon nanomaterials with different geometric structures exhibit quite different cytotoxicity and bioactivity in vitro, although they may not be accurately reflected in the comparative toxicity in vivo.
1,322 citations
TL;DR: A critical examination of published data obtained primarily from recent nuclear magnetic resonance spectroscopy, X-ray absorption near-edge structure spectroscopic, electrospray ionization-mass spectrometry, and pyrolysis studies reveals an evolving new view of the molecular structure of soil humic substances.
Abstract: A critical examination of published data obtained primarily from recent nuclear magnetic resonance spectroscopy, X-ray absorption near-edge structure spectroscopy, electrospray ionization−mass spectrometry, and pyrolysis studies reveals an evolving new view of the molecular structure of soil humic substances. According to the new view, humic substances are collections of diverse, relatively low molecular mass components forming dynamic associations stabilized by hydrophobic interactions and hydrogen bonds. These associations are capable of organizing into micellar structures in suitable aqueous environments. Humic components display contrasting molecular motional behavior and may be spatially segregated on a scale of nanometers. Within this new structural context, these components comprise any molecules intimately associated with a humic substance, such that they cannot be separated effectively by chemical or physical methods. Thus biomolecules strongly bound within humic fractions are by definition humic...
1,122 citations
TL;DR: Nanoscale zero-valent iron (NZVI) was synthesized and tested for the removal of As(III), which is a highly toxic, mobile, and predominant arsenic species in anoxic groundwater and suggests that NZVI is a suitable candidate for both in-situ and ex-Situ groundwater treatment due to its high reactivity.
Abstract: Nanoscale zero-valent iron (NZVI) was synthesized and tested for the removal of As(III), which is a highly toxic, mobile, and predominant arsenic species in anoxic groundwater. We used SEM-EDX, AFM, and XRD to characterize particle size, surface morphology, and corrosion layers formed on pristine NZVI and As(III)-treated NZVI. AFM results showed that particle size ranged from 1 to 120 nm. XRD and SEM results revealed that NZVI gradually converted to magnetite/maghemite corrosion products mixed with lepidocrocite over 60 d. Arsenic(III) adsorption kinetics were rapid and occurred on a scale of minutes following a pseudo-first-order rate expression with observed reaction rate constants (kobs) of 0.07−1.3 min-1 (at varied NZVI concentration). These values are about 1000× higher than kobs literature values for As(III) adsorption on micron size ZVI. Batch experiments were performed to determine the feasibility of NZVI as an adsorbent for As(III) treatment in groundwater as affected by initial As(III) concentra...
1,100 citations
TL;DR: It is demonstrated that electricity generation is possible from soluble fermentation end products such as acetate and butyrate, but energy recoveries should be increased to improve the overall process performance.
Abstract: Hydrogen can be recovered by fermentation of organic material rich in carbohydrates, but much of the organic matter remains in the form of acetate and butyrate. An alternative to methane production from this organic matter is the direct generation of electricity in a microbial fuel cell (MFC). Electricity generation using a single-chambered MFC was examined using acetate or butyrate. Power generated with acetate (800 mg/L) (506 mW/m2 or 12.7 mW/L) was up to 66% higher than that fed with butyrate (1000 mg/L) (305 mW/m2 or 7.6 mW/L), demonstrating that acetate is a preferred aqueous substrate for electricity generation in MFCs. Power output as a function of substrate concentration was well described by saturation kinetics, although maximum power densities varied with the circuit load. Maximum power densities and half-saturation constants were Pmax = 661 mW/m2 and Ks = 141 mg/L for acetate (218 Ω) and Pmax = 349 mW/m2 and Ks = 93 mg/L for butyrate (1000 Ω). Similar open circuit potentials were obtained in us...
936 citations
TL;DR: By augmenting the electrochemical potential achieved by bacteria in this MFC with an additional voltage of 250 mV or more, it was possible to produce hydrogen at the cathode directly from the oxidized organic matter.
Abstract: Hydrogen production via bacterial fermentation is currently limited to a maximum of 4 moles of hydrogen per mole of glucose, and under these conditions results in a fermentation end product (acetate; 2 mol/mol glucose) that bacteria are unable to further convert to hydrogen. It is shown here that this biochemical barrier can be circumvented by generating hydrogen gas from acetate using a completely anaerobic microbial fuel cell (MFC). By augmenting the electrochemical potential achieved by bacteria in this MFC with an additional voltage of 250 mV or more, it was possible to produce hydrogen at the cathode directly from the oxidized organic matter. More than 90% of the protons and electrons produced by the bacteria from the oxidation of acetate were recovered as hydrogen gas, with an overall Coulombic efficiency (total recovery of electrons from acetate) of 60−78%. This is equivalent to an overall yield of 2.9 mol H2/mol acetate (assuming 78% Coulombic efficiency and 92% recovery of electrons as hydrogen)....
935 citations
TL;DR: It is demonstrated that power densities can be increased to over 1 W/m2 by changing the operating conditions or electrode spacing, which should lead to further improvements in power generation and energy recovery in single-chamber, air-cathode MFCs.
Abstract: Power density, electrode potential, coulombic efficiency, and energy recovery in single-chamber microbial fuel cells (MFCs) were examined as a function of solution ionic strength, electrode spacing and composition, and temperature. Increasing the solution ionic strength from 100 to 400 mM by adding NaCl increased power output from 720 to 1330 mW/m2. Power generation was also increased from 720 to 1210 mW/m2 by decreasing the distance between the anode and cathode from 4to 2 cm. The power increases due to ionic strength and electrode spacing resulted from a decrease in the internal resistance. Power output was also increased by 68% by replacing the cathode (purchased from a manufacturer) with our own carbon cloth cathode containing the same Pt loading. The performance of conventional anaerobic treatment processes, such as anaerobic digestion, are adversely affected by temperatures below 30 degrees C. However, decreasing the temperature from 32 to 20 degrees C reduced power output by only 9%, primarily as a result of the reduction of the cathode potential. Coulombic efficiencies and overall energy recovery varied as a function of operating conditions, but were a maximum of 61.4 and 15.1% (operating conditions of 32 degrees C, carbon paper cathode, and the solution amended with 300 mM NaCl). These results, which demonstrate that power densities can be increased to over 1 W/m2 by changing the operating conditions or electrode spacing, should lead to further improvements in power generation and energy recovery in single-chamber, air-cathode MFCs.
911 citations
TL;DR: The finding that one bacterium can produce electron shuttles, which can be used also by other bacteria, to enhance electron-transfer rate and growth, has not been shown before and has considerable implications with respect to the power output attainable in MFCs.
Abstract: High-rate electron transfer toward an anode in microbial fuel cells(MFCs) has thus far not been described for bacteria-producing soluble redox mediators. To study the mechanism of electron transfer, we used a MFC isolate, Pseudomonas aeruginosa strain KRP1. Bacterial electron transfer toward the MFC anode was enabled through pyocyanin and phenazine-l-carboxamide. The presence of the anode stimulated pyocyanin production. Mutant strains, deficient in the synthesis of pyocyanin and phenazine-1-carboxamide, were unable to achieve substantial electron transfer and reached only 5% of the wild type's power output. Upon pyocyanin addition, the power output was restored to 50%. Pyocyanin was not only used by P. aeruginosa to improve electron transfer but as well enhanced electron transfer by other bacterial species. The finding that one bacterium can produce electron shuttles, which can be used also by other bacteria, to enhance electron-transfer rate and growth, has not been shown before. These findings have considerable implications with respect to the power output attainable in MFCs.
902 citations
TL;DR: Two widely studied nano-Fe0 preparations are characterized: one synthesized by reduction of goethite with heat and H2 and the other by reductive precipitation with borohydride, which exhibit corrosion potentials that are more negative than nano-sized Fe2O3, Fe3O4, micro-sizedFe0, or a solid Fe0 disk.
Abstract: There are reports that nano-sized zero-valent iron (Fe0) exhibits greater reactivity than micro-sized particles of Fe0, and it has been suggested that the higher reactivity of nano-Fe0 may impart advantages for groundwater remediation or other environmental applications. However, most of these reports are preliminary in that they leave a host of potentially significant (and often challenging) material or process variables either uncontrolled or unresolved. In an effort to better understand the reactivity of nano-Fe0, we have used a variety of complementary techniques to characterize two widely studied nano-Fe0 preparations: one synthesized by reduction of goethite with heat and H2 (FeH2) and the other by reductive precipitation with borohydride (FeBH). FeH2 is a two-phase material consisting of 40 nm α-Fe0 (made up of crystals approximately the size of the particles) and Fe3O4 particles of similar size or larger containing reduced sulfur; whereas FeBH is mostly 20−80 nm metallic Fe particles (aggregates ...
TL;DR: It is suggested that a biologically based conceptualization, the biodynamic model, provides the necessary unification for a key aspect in risk: metal bioaccumulation (internal exposure).
Abstract: Ecological risks from metal contaminants are difficult to document because responses differ among species, threats differ among metals, and environmental influences are complex. Unifying concepts are needed to better tie together such complexities. Here we suggest that a biologically based conceptualization, the biodynamic model, provides the necessary unification for a key aspect in risk: metal bioaccumulation (internal exposure). The model is mechanistically based, but empirically considers geochemical influences, biological differences, and differences among metals. Forecasts from the model agree closely with observations from nature, validating its basic assumptions. The biodynamic metal bioaccumulation model combines targeted, high-quality geochemical analyses from a site of interest with parametrization of key physiological constants for a species from that site. The physiological parameters include metal influx rates from water, influx rates from food, rate constants of loss, and growth rates (whe...
TL;DR: Results show that many pharmaceuticals present in wastewater can be efficiently oxidized with O3 and that suspended solids have only a minor influence on the oxidation efficiency of nonsorbing micropollutants.
Abstract: To reduce the release of pharmaceuticals and endocrine disruptors into the aquatic environment or to remove them from wastewater intended for direct or indirect reuse, the application of advanced wastewater treatment may be required. In the present study, municipal wastewater effluents were treated with ozone (O3) in a pilot-scale plant consisting of two bubble columns. The investigated effluents, which varied in suspended solids concentrations, comprised an effluent of conventional activated sludge treatment (CAS), the same effluent dosed with 15 mg of TSS L-1 of activated sludge (CAS + SS), and the effluent of a membrane bioreactor pilot plant (MBR). Selected classes of pharmaceuticals were spiked in the wastewater at realistic levels ranging from 0.5 to 5 μg L-1. Samples taken at the inlet and the outlet of the pilot plant were analyzed with liquid chromatography (LC)−electrospray tandem mass spectrometry (MS). Macrolide and sulfonamide antibiotics, estrogens, and the acidic pharmaceuticals diclofenac,...
TL;DR: A simple and green approach for synthesizing palladized iron (Fe-Pd) nanoparticles by applying a water-soluble starch as a stabilizer is developed, and the starched nanoparticles exhibited markedly greater reactivity when used for dechlorination of TCE or PCBs in water.
Abstract: Dechlorination of TCE and PCBs using bimetallic nanoparticles has received increasing interest in recent years. However, due to the extremely high reactivity, nanoparticles prepared using current methods tend to either react with surrounding media or agglomerate, resulting in the formation of much larger flocs and significant loss in reactivity. To overcome these drawbacks, we developed a simple and green approach for synthesizing palladized iron (Fe−Pd) nanoparticles. We modified the conventional methods by applying a water-soluble starch as a stabilizer. The starched nanoparticles displayed much less ag glomeration but greater dechlorination power than those prepared without a stabilizer. TEM analyses indicated that the starched nanoparticles were present as discrete particles as opposed to dendritic flocs for nonstarched particles. The mean particle size was estimated to be 14.1 nm with a standard deviation of 11.7 nm, which translated to a surface area of ∼55 m2 g-1. While starched nanoparticles remai...
TL;DR: Comparison of the colloid stability of a series of oxide nanoparticles reveals that untreated oxide suspensions rapidly agglomerate in biological fluids and allows the conclusion that the presented transport and uptake kinetics at low concentrations may be extended to other industrially relevant materials.
Abstract: Quantitative studies on the uptake of nanoparticles into biological systems should consider simultaneous agglomera tion, sedimentation, and diffusion at physiologically relevant concentrations to assess the corresponding risks of nanomaterials to human health. In this paper, the transport and uptake of industrially important cerium oxide nanoparticles, into human lung fibroblasts is measured in vitro after exposing thoroughly characterized particle suspensions to a fibroblast cell culture for particles of four separate size fractions and concentrations ranging from 100 ng g-1 to 100 μg g-1 of fluid (100 ppb to 100 ppm). The unexpected findings at such low but physiologically relevant concentrations reveal a strong dependence of the amount of incorporated ceria on particle size, while nanoparticle number density or total particle surface area are of minor importance. These findings can be explained on the basis of a purely physical model. The rapid formation of agglomerates in the liquid is strongly favore...
TL;DR: It was found that the soluble COD (SCOD) removal efficiencies remained over 90% throughout the operational period, mainly because of methanogenic activity, which accounted for 35 to 58% of the SCOD removed at a loading rate of 1.0 g COD/L/ day.
Abstract: The upflow microbial fuel cell (UMFC) was developed to generate electricity while simultaneously treating wastewater. During a five-month period of feeding a sucrose solution as the electron donor, the UMFC continuously generated electricity with a maximum power density of 170 mW/m2. To achieve this power density, the artificial electron-mediator hexacyanoferrate was required in the cathode chamber. The power density increased with increasing chemical oxygen demand (COD) loading rates up to 2.0 g COD/ L/day after which no further increases in power density were observed, indicating the presence of limiting factors. The overarching limiting factor for the UMFC in this study was the internal resistance, which was estimated as 84 omega at the maximum power density, and restricted the power output by causing a significant decrease in operating potential. Low Coulombic efficiencies varying from 0.7 to 8.1% implied that the electron-transfer bacteria were incapable of converting all of the available organics into electricity, so the excessive substrate created niches for the growth of methanogens. We found that the soluble COD (SCOD) removal efficiencies remained over 90% throughout the operational period, mainly because of methanogenic activity, which accounted for 35 to 58% of the SCOD removed at a loading rate of 1.0 g COD/L/ day. Additionally, transport limitation due to insufficient substrate diffusion was shown by cyclic voltammetry (CV).
TL;DR: Results from DMPO spin-trapping electron spin resonance measurements confirm the formation of hydroxyl radicals, which is the origin of the considerable bactericidal activity under visible light irradiation.
Abstract: Sulfur-doped titanium dioxide exhibits a strong visible-light-induced antibacterial effect. The new photocatalyst can effectively kill Micrococcus lylae, a common Gram-positive bacterium. The relationship between sulfur concentration and the bactericidal activity of S-doped TiO2 was investigated. Results from DMPO spin-trapping electron spin resonance measurements confirm the formation of hydroxyl radicals, which is the origin of the considerable bactericidal activity under visible light irradiation.
TL;DR: Reaction rates, pathways, and efficiency of two nanoscale Fe0 particles are measured in batch reactors: particles synthesized from sodium borohydride reduction of ferrous iron (Fe/B) and commercially available particles (RNIP).
Abstract: Nanoscale Fe0 particles are a promising technology for in situ remediation of trichloroethene (TCE) plumes and TCE-DNAPL source areas, but the physical and chemical properties controlling their reactivity are not yet understood. Here, the TCE reaction rates, pathways, and efficiency of two nanoscale Fe0 particles are measured in batch reactors: particles synthesized from sodium borohydride reduction of ferrous iron (Fe/B) and commercially available particles (RNIP). Reactivity was determined under iron-limited (high [TCE]) and excess iron (low [TCE]) conditions and with and without added H2. Particle efficiency, defined as the fraction of the Fe0 in the particles that is used to dechlorinate TCE, was determined under iron-limited conditions. Both particles had a core/shell structure and similar specific surface areas (∼30 m2/g). Using excess iron, Fe/B transformed TCE into ethane (80%) and C3−C6 coupling products (20%). The measured surface area normalized pseudo-first-order rate constant for Fe/B (1.4 ×...
TL;DR: Pot experiments show that the proportions of DMAV in the grain are significantly dependent on rice cultivar (p = 0.026) and that plant nutrient status is effected by arsenic exposure.
Abstract: Ingestion of drinking water is not the only elevated source of arsenic to the diet in the Bengal Delta. Even at background levels, the arsenic in rice contributes considerably to arsenic ingestion in subsistence rice diets. We set out to survey As speciation in different rice varieties from different parts of the globe to understand the contribution of rice to arsenic exposure. Pot experiments were utilized to ascertain whether growing rice on As contaminated soil affected speciation and whether genetic variation accounted for uptake and speciation. USA long grain rice had the highest mean arsenic level in the grain at 0.26 microg As g(-1) (n = 7), and the highest grain arsenic value of the survey at 0.40 microg As g(-1). The mean arsenic level of Bangladeshi rice was 0.13 microg As g(-1) (n = 15). The main As species detected in the rice extract were AsIII, DMAV, and AsV. In European, Bangladeshi, and Indian rice 64 +/- 1% (n = 7), 80 +/- 3% (n = 11), and 81 +/- 4% (n = 15), respectively, of the recovered arsenic was found to be inorganic. In contrast, DMAV was the predominant species in rice from the USA, with only 42 +/- 5% (n = 12) of the arsenic being inorganic. Pot experiments show that the proportions of DMAV in the grain are significantly dependent on rice cultivar (p = 0.026) and that plant nutrient status is effected by arsenic exposure.
TL;DR: Emissions of metals and other particle-phase species from on-road motor vehicles were measured in two tunnels in Milwaukee, WI during the summer of 2000 and winter of 2001 and correlations between these elements in PM2.5 indicate that direct brake wear emissions are also important.
Abstract: Emissions of metals and other particle-phase species from on-road motor vehicles were measured in two tunnels in Milwaukee, WI during the summer of 2000 and winter of 2001. Emission factors were calculated from measurements of fine (PM2.5) and coarse (PM10) particulate matter at tunnel entrances and exits, and effects of fleet composition and season were investigated. Cascade impactors (MOUDI) were used to obtain size-resolved metal emission rates. Metals were quantified with inductively-coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence (XRF). PM10 emission rates ranged from 38.7 to 201 mg km(-1) and were composed mainly of organic carbon (OC, 30%), inorganic ions (sulfate, chloride, nitrate, ammonium, 20%), metals (19%), and elemental carbon (EC, 9.3%). PM10 metal emissions were dominated by crustal elements Si, Fe, Ca, Na, Mg, Al, and K, and elements associated with tailpipe emissions and brake and tire wear, including Cu, Zn, Sb, Ba, Pb, and S. Metals emitted in PM2.5 were lower (11.6% of mass). Resuspension of roadway dust was dependent on weather and road surface conditions, and increased emissions were related to higher traffic volumes and fractions of heavy trucks. Emission of noble metals from catalytic converters appeared to be impacted by the presence of older vehicles. Elements related to brake wear were impacted by enriched road dust resuspension, but correlations between these elements in PM2.5 indicate that direct brake wear emissions are also important. A submicrometer particle mode was observed in the emissions of Pb, Ca, Fe, and Cu.
TL;DR: The results obtained illustrate the importance of considering retransformable substances, for example human metabolites, when investigating the behavior and fate of pharmaceuticals.
Abstract: The occurrence of sulfonamide and macrolide antimicrobials, as well as trimethoprim, was investigated in conventional activated sludge treatment. Average daily loads in untreated wastewater correlated well with those estimated from annual consumption data and pharmacokinetic behavior. Considerable variations were found during a day, and seasonal differences seem to occur for the macrolides, probably caused by a higher consumption of these substances in winter. The most predominant macrolide and sulfonamide antimicrobials were clarithromycin and sulfamethoxazole, respectively. In the case of sulfamethoxazole, the main human metabolite, N4-acetylsulfamethoxazole, was included as an analyte, accounting for up to 86% of the total load in untreated wastewater. The results obtained illustrate the importance of considering retransformable substances, for example human metabolites, when investigating the behavior and fate of pharmaceuticals. Average concentrations of sulfapyridine, sulfamethoxazole, trimethoprim, azithromycin, and clarithromycin in activated sludge ranged between 28 and 68 microg/kg of dry weight. Overall the sorption to activated sludge was shown to be low for the investigated antimicrobials, with estimated sorption constants for activated sludge below 500 L/kg. Elimination in activated sludge treatment was found to be incomplete for all investigated compounds. In final effluents, the median concentrations for sulfamethoxazole and clarithromycin were 290 and 240 ng/L, respectively.
TL;DR: To further improve MFCs, focus has to be placed on the enhanced conversion of nonrapidly biodegradable material and the better directing of the anode flow toward the electrode instead of to alternative electron acceptors.
Abstract: A tubular, single-chambered, continuous microbial fuel cell (MFC) that generates high power outputs using a granular graphite matrix as the anode and a ferricyanide solution as the cathode is described. The maximal power outputs obtained were 90 and 66 W m(-3) net anodic compartment (NAC) (48 and 38 W m(-3) total anodic compartment (TAC)) for feed streams based on acetate and glucose, respectively, and 59 and 48 W m(-3) NAC for digester effluent and domestic wastewater, respectively. For acetate and glucose, the total Coulombic conversion efficiencies were 75 +/- 5% and 59 +/- 4%, respectively, at loading rates of 1.1 kg chemical oxygen demand m(-3) NAC volume day(-1). When wastewater was used, of the organic matter effectively removed (i.e., 22% at a loading of 2 kg organic matter m(-3) NAC day(-1)), up to 96% was converted to electricity on a Coulombic basis. The lower overall efficiency of the wastewater-treating reactors is related to the presence of nonreadily biodegradable organics and the interference of alternative electron acceptors such as sulfate present in the wastewater. To further improve MFCs, focus has to be placed on the enhanced conversion of nonrapidly biodegradable material and the better directing of the anode flow toward the electrode instead of to alternative electron acceptors. Also the use of sustainable, open-air cathodes is a critical issue for practical implementation.
TL;DR: This research suggests that selected chemicals are useful as tracers of human wastewater discharge by determining the persistence of a chemically diverse suite of emerging contaminants in streams.
Abstract: The quality of drinking and recreational water is currently (2005) determined using indicator bacteria. However, the culture tests used to analyze forthese bacteria require a long time to complete and do not discriminate between human and animal fecal material sources. One complementary approach is to use chemicals found in human wastewater, which would have the advantages of (1) potentially shorter analysis times than the bacterial culture tests and (2) being selected for human-source specificity. At 10 locations, water samples were collected upstream and at two successive points downstream from a wastewaster treatment plant (WWTP); a treated effluent sample was also collected at each WWTP. This sampling plan was used to determine the persistence of a chemically diverse suite of emerging contaminants in streams. Samples were also collected at two reference locations assumed to have minimal human impacts. Of the 110 chemical analytes investigated in this project, 78 were detected at least once. The number of compounds in a given sample ranged from 3 at a reference location to 50 in a WWTP effluent sample. The total analyte load at each location varied from 0.018 microg/L at the reference location to 97.7 microg/L in a separate WWTP effluent sample. Although most of the compound concentrations were in the range of 0.01-1.0 microg/L, in some samples, individual concentrations were in the range of 5-38 microg/L. The concentrations of the majority of the chemicals present in the samples generally followed the expected trend: they were either nonexistent or at trace levels in the upstream samples, had their maximum concentrations in the WWTP effluent samples, and then declined in the two downstream samples. This research suggests that selected chemicals are useful as tracers of human wastewater discharge.
TL;DR: Four important organic UV filter compounds are investigated in wastewater, and in water and fish from various Swiss lakes, using gas chromatographic/mass spectrometric analyses, suggesting some potential for accumulation of these compounds in biota.
Abstract: Organic UV filters are used in personal care products such as sunscreen products, and in cosmetics, beauty creams, skin lotions, lipsticks, hair sprays, hair dyes, shampoos, and so forth. The compounds enter the aquatic environmentfrom showering, wash-off, washing (laundering), and so forth via wastewater treatment plants (WWTPs) ("indirect inputs") and from recreational activities such as swimming and bathing in lakes and rivers ("direct inputs"). In this study, we investigated the occurrence of four important organic UV filter compounds (benzophenone-3, BP-3; 4-methylbenzylidene camphor, 4-MBC; ethylhexyl methoxy cinnamate, EHMC; octocrylene, OC) in wastewater, and in water and fish from various Swiss lakes, using gas chromatographic/mass spectrometric analyses. All four UV filters were present in untreated wastewater (WWTP influent) with a maximum concentration of 19 microg L(-1) for EHMC. The data indicate a seasonal variation with influent loads higher in the warmer season (June 2002) than in the colder one (April 2002). The influent loads were in the order EHMC > 4-MBC approximately BP-3 > OC. The concentrations in treated wastewater (WWTP effluent) were considerably lower, indicating substantial elimination in the plants. 4-MBC was usually the most prevalent compound (maximum concentration, 2.7 microg L(-1)), followed by BP-3, EHMC, and OC. UV filters were also detected in Swiss midland lakes and a river (Limmat) receiving inputs from WWTPs and recreational activities. However, all concentrations were low (<2-35 ng L(-1)); no UV filters (<2 ng L(-1)) were detected in a remote mountain lake. Data from passive sampling using semipermeable membrane devices (SPMDs) supported the presence of these UV filters in the lakes and the river and suggested some potential for accumulation of these compounds in biota. SPMD-derived water concentrations increased in the order Greifensee < Zurichsee < Huttnersee. This order is reversed from that observed for methyl triclosan, used as a chemical marker for WWTP-derived lipophilic contaminants in the lakes. This indicated inputs of UV filters from sources other than WWTPs to the lakes during summer,for example,inputs from recreational activities. Fish (white fish, Coregonus sp.; roach, Rutilus rutilus; perch, Perca fluviatilis) from these lakes contained low but detectable concentrations of UV filters, in particular, 4-MBC (up to 166 ng g(-1) on a lipid basis). 4-MBC concentrations relative to methyl triclosan were lower in fish than in SPMDs exposed in the same lakes, suggesting that 4-MBC is less bioaccumulated than expected or metabolized in fish. The lipid-based bioconcentration factor (BCF(L)) estimated from the fish (roach) data and SPMD-derived water concentrations was about 1-2.3 x 10(4) and thus approximately 1 order of magnitude lower than expected from its Kow value.
TL;DR: The environmental fate, distribution, and biological risk associated with this important class of engineered nanomaterials will require a model that addresses not only the properties of bulk C60 but also that of the aggregate form generated in aqueous media.
Abstract: Upon contact with water, under a variety of conditions, C60 spontaneously forms a stable aggregate with nanoscale dimensions (d = 25-500 nm), termed here "nano-C60". The color, hydrophobicity, and reactivity of individual C60 are substantially altered in this aggregate form. Herein, we provide conclusive lines of evidence demonstrating that in solution these aggregates are crystalline in order and remain as underivatized C60 throughout the formation/stabilization process that can later be chemically reversed. Particle size can be affected by formation parameters such as rates and the pH of the water addition. Once formed, nano-C60 remains stable in solution at or below ionic strengths of 0.05 I for months. In addition to demonstrating aggregate formation and stability over a wide range of conditions, results suggest that prokaryotic exposure to nano-C60 at relatively low concentrations is inhibitory, indicated by lack of growth (> or = 0.4 ppm) and decreased aerobic respiration rates (4 ppm). This work demonstrates the fact that the environmental fate, distribution, and biological risk associated with this important class of engineered nanomaterials will require a model that addresses not only the properties of bulk C60 but also that of the aggregate form generated in aqueous media.
TL;DR: Inadvertent ingestion of house dust is the largest contributor to exposure of toddlers through to adults and is the main exposure pathway for all life stages other than the infant, including the nursing mother, who transfers PBDEs to her infant via human milk.
Abstract: Polybrominated diphenyl ether (PBDE) body burdens in North America are 20 times that of Europeans and some “high accumulation” individuals have burdens up to 1−2 orders of magnitude higher than median values, the reasons for which are not known. We estimated emissions and fate of ΣPBDEs (minus BDE-209) in a 470 km2 area of Toronto, Canada, using the Multi-media Urban Model (MUM-Fate). Using a combination of measured and modeled concentrations for indoor and outdoor air, soil, and dust plus measured concentrations in food, we estimated exposure to ΣPBDEs via soil, dust, and dietary ingestion and indoor and outdoor inhalation pathways. Fate calculations indicate that 57−85% of PBDE emissions to the outdoor environment originate from within Toronto and that the dominant removal process is advection by air to downwind locations. Inadvertent ingestion of house dust is the largest contributor to exposure of toddlers through to adults and is thus the main exposure pathway for all life stages other than the infan...
TL;DR: Alkaline Ca-rich industrial residues are presented as a possible feedstock for mineral CO2 sequestration and the carbonation reaction was found to occur in two steps: leaching of calcium from the steel slag particles into the solution and precipitation of calcite on the surface of these particles.
Abstract: Mineral CO2 sequestration, i.e., carbonation of alkaline silicate Ca/Mg minerals, analogous to natural weathering processes, is a possible technology for the reduction of carbon dioxide emissions t...
TL;DR: "Dicofol type DDT pollution", defined asDDT pollution caused by dic ofol use and characterized with high o,p'-DDT/p,p'DDT ratio, might be serious in China, especially in southern and eastern China.
Abstract: High DDT concentrations and o,p'-DDT/p,p'-DDT ratios observed in the air over Taihu Lake, a lake near Shanghai, China, led us to suggest that current use of dicofol in the area north of the lake was the main source of the measured DDTs. To examine this hypothesis, samples of commercially available formulated dicofol in China were collected in 2003 to measure the impurities of DDT related compounds (DDTs). The o,p'-DDT/p,p'-DDT ratio in the samples was 7.0, close to the observed value in the air over Taihu Lake. Average contents of o,p'-DDT, p,p'-CI-DDT, o,p'-DDE, and p,p'-DDT in the samples were 114, 69, 44, and 17 g per kg dicofol, respectively. On the basis of a production and distribution survey, total input of DDTs to the environment from the dicofol use in China was estimated to be 8770 t between 1988 and 2002. "Dicofol type DDT pollution", defined as DDT pollution caused by dicofol use and characterized with high o,p'-DDT/p,p'-DDT ratio, might be serious in China, especially in southern and eastern China. The conversion of p,p'-CI-DDT to p,p'-DDE can lead to high p,p'-DDE/p,p'-DDT ratio and could mislead the evaluation of p,p'-DDT resident time in the environment. Therefore, more studies on p,p'-CI-DDT in the environment are needed.
TL;DR: The findings indicate the potential of performing organic source apportionment on the basis of total particle mass, rather than on the based of organic tracer compounds that contribute a small fraction of this mass.
Abstract: A new technique has been developed to deconvolve and quantify the mass concentrations of hydrocarbon-like and oxygenated organic aerosols (HOA and OOA) using highly time-resolved organic mass spectra obtained with an Aerodyne Aerosol Mass Spectrometer (AMS). This technique involves a series of multivariate linear regressions that use mass-to-charge ratios (ml/s) 57 (mostly C4H9+) and 44 (mostly CO2+)-the identified AMS mass spectral tracers for HOA and OOA, respectively-as the initial principal components. Two algorithms have been developed: algorithm 1 is based solely on m/z 44 and m/z 57, and algorithm 2 is an iterative procedure expanded from algorithm 1. This technique was applied to the AMS organic aerosol data acquired at the EPA Pittsburgh Supersite during September 2002. The reconstructed organic concentrations (= HOA + OOA) agree well with the measured values (r2 = 0.997, slope = 0.998), and the reconstructed organic data matrix (size = 3199 time steps x 300 m/z's) explains 99% of the variance in the measured time series. In addition, the extracted mass spectrum of HOA shows high similarity to those of diesel exhaust, lubricating oil, and freshly emitted traffic aerosols observed in urban areas, while the spectrum of OOA closely resembles those of aged organic aerosols sampled in rural areas and also shows similarity with the spectrum of fulvic acid- a humic-like substance that is ubiquitous in the environment and has previously been used as an analogue to represent polyacid components found in highly processed and oxidized atmospheric organic aerosols. There is evidence for the presence of a third component, although its contribution to the total organic signal appears to be small in this study. The most important result is that m/z 44 and m/z 57 are reliable AMS mass spectral "markers" that provide the "first guess" for algorithm 2 which allows the quantitative description of the organic aerosol concentration and mass spectra over a period of 16 days in a major urban area and allows the extraction of mass spectra of OOA and HOA that can be interpreted chemically. These findings indicate the potential of performing organic source apportionment on the basis of total particle mass, rather than on the basis of organic tracer compounds that contribute a small fraction of this mass.
TL;DR: In this article, the authors performed quantitative structure-activity relationship (QSAR) analyses that suggested a propensity of TCC to persist in various environmental compartments with predicted half-lives ranging from 0.75 days in air to 540 days in sediment.
Abstract: Triclocarban (TCC) and triclosan (TCS) are antimicrobial additives in personal care products. Whereas TCS has been studied extensively, the environmental fate of TCC remains largely unknown. To address this data gap, we performed quantitative structure-activity relationship (QSAR) analyses that suggested a propensity of TCC to persist in various environmental compartments with predicted half-lives ranging from 0.75 days in air to 540 days in sediment. Moreover, concentrations of both antimicrobials were measured in 42 environmental samples from the Greater Baltimore region using a combination of solid-phase extraction, liquid chromatography/mass spectrometry, and isotope dilution. The co-occurrence of TCC and TCS was observed, owing to similar properties, usage, disposal, and environmental half-lives. A linear empirical correlation (R2 = 0.9882) fit the log-log-transformed data from diverse aquatic media and spanned 5 orders of magnitude in concentration. Occurrences of TCC predicted for 85 U.S. streams were statistically indistinguishable from experimental regional data (alpha < or = 0.05). Annual loading of antimicrobials to water resources probably is dominated by activated sludge treatment plants (39-67%), followed by trickling filters (31-54%) and combined and sanitary sewer overflows (2-7% and <0.2%, respectively). Study results suggest that TCC is a previously unrecognized contaminant of U.S. water resources nationwide, likely ranking in the top 10 in occurrence rate and in the top 20 in maximum concentration among 96 organic pollutants considered. The magnitude and frequency of TCC contamination (regional, 6750 ng/L, 68%; predicted nationwide for 1999--2000, 1150 ng/L, 60%) were markedly higher than non-peer-reviewed numbers (240 ng/L, 30%, U.S.) currently used by the U.S. Environmental Protection Agency for evaluating TCC's ecological and human health risks.