Showing papers in "Environmental Science & Technology in 2001"

Global distribution of perfluorooctane sulfonate in wildlife.

Abstract: Here we report, for the first time, on the global distribution of perfluorooctanesulfonate (PFOS), a fluorinated organic contaminant. PFOS was measured in the tissues of wildlife, including, fish, birds, and marine mammals. Some of the species studied include bald eagles, polar bears, albatrosses, and various species of seals. Samples were collected from urbanized areas in North America, especially the Great Lakes region and coastal marine areas and rivers, and Europe. Samples were also collected from a number of more remote, less urbanized locations such as the Arctic and the North Pacific Oceans. The results demonstrated that PFOS is widespread in the environment. Concentrations of PFOS in animals from relatively more populated and industrialized regions, such as the North American Great Lakes, Baltic Sea, and Mediterranean Sea, were greater than those in animals from remote marine locations. Fisheating, predatory animals such as mink and bald eagles contained concentrations of PFOS that were greater than the concentrations in their diets. This suggests that PFOS can bioaccumulate to higher trophic levels of the food chain. Currently available data indicate that the concentrations of PFOS in wildlife are less than those required to cause adverse effects in laboratory animals.

Plastic Resin Pellets as a Transport Medium for Toxic Chemicals in the Marine Environment

Abstract: Plastic resin pellets (small granules 0.1−0.5 centimeters in diameter) are widely distributed in the ocean all over the world. They are an industrial raw material for the plastic industry and are unintentionally released to the environment both during manufacturing and transport. They are sometimes ingested by seabirds and other marine organisms, and their adverse effects on organisms are a concern. In the present study, PCBs, DDE, and nonylphenols (NP) were detected in polypropylene (PP) resin pellets collected from four Japanese coasts. Concentrations of PCBs (4−117 ng/g), DDE (0.16−3.1 ng/g), and NP (0.13−16 μg/g) varied among the sampling sites. These concentrations were comparable to those for suspended particles and bottom sediments collected from the same area as the pellets. Field adsorption experiments using PP virgin pellets demonstrated significant and steady increase in PCBs and DDE concentrations throughout the six-day experiment, indicating that the source of PCBs and DDE is ambient seawater...

Sorption of veterinary pharmaceuticals in soils: a review.

Abstract: Veterinary pharmaceuticals (VPs) are used in large amounts in modern husbandry. Due to their use pattern, they possess a potential for reaching the soil environment. To assess their mobility in soil, the literature on sorption of chemicals used as VPs is reviewed and put into perspective of their physicochemical properties. The compilation of sorption coefficients to soil solids (Kd,solid) demonstrates that these chemicals display a wide range of mobility (0.2 < Kd,solid < 6,000 L/kg). Partition coefficients for association of tetracycline and quinolone carboxylic acid VPs to dissolved organic matter (Kd,DOM) vary between 100 and 50,000 L/kg. The variation in Kd,solid for a given compound in different soils can be significant. For most of the compounds, the variation is not considerably lower for the organic carbon-normalized sorption coefficient Koc. In addition, prediction of log Koc by log Kow leads to significant underestimation of log Koc and log Kd,DOM values. This suggests that mechanisms other than hydrophobic partitioning play a significant role in sorption of VPs. A number of hydrophobicity-independent mechanisms such as cation exchange, cation bridging at clay surfaces, surface complexation, and hydrogen bonding appear to be involved. These processes are not accounted for by organic carbon normalization, suggesting that this data treatment is conceptually inappropriate and fails to describe the sorption behavior. Moreover, prediction of log Koc based on the hydrophobicity parameter log Kow is not successful.

Measurement of emissions from air pollution sources. 3. C1-C29 organic compounds from fireplace combustion of wood.

Abstract: Organic compound emission rates for volatile organic compounds (VOC), gas-phase semivolatile organic compounds, and particle-phase organic compounds are measured from residential fireplace combustion of wood. Firewood from a conifer tree (pine) and from two deciduous trees (oak and eucalyptus) is burned to determine organic compound emissions profiles for each wood type including the distribution of the alkanes, alkenes, aromatics, polycyclic aromatic hydrocarbons (PAH), phenol and substituted phenols, guaiacol and substituted guaiacols, syringol and substituted syringols, carbonyls, alkanoic acids, resin acids, and levoglucosan. Levoglucosan is the major constituent in the fine particulate emissions from all three wood types, contributing 18−30% of the fine particulate organic compound emissions. Guaiacol (2-methoxyphenol), and guaiacols with additional substituents at position 4 on the molecule, and resin acids are emitted in significant quantities from pine wood combustion. Syringol (2,6-dimethoxyphenol) and syringols with additional substituents at position 4 on the molecule are emitted in large amounts from oak and eucalyptus firewood combustion, but these compounds are not detected in the emissions from pine wood combustion. Syringol and most of the substituted syringols are found to be semivolatile compounds that are present in both the gas and particle phases, but two substituted syringols that have not been previously quantified in wood smoke emissions, propionylsyringol and butyrylsyringol, are found exclusively in the particle phase and can be used to help trace hardwood smoke particles in the atmosphere. Benzene, ethene, and acetylene are often used as tracers for motor vehicle exhaust in the urban atmosphere. The contribution of wood smoke to the ambient concentrations of benzene, ethene, and acetylene could lead to an overestimate of the contribution of motor vehicle tailpipe exhaust to atmospheric VOC concentrations.

Arsenic contamination of groundwater and drinking water in Vietnam: a human health threat.

Abstract: This is the first publication on arsenic contamination of the Red River alluvial tract in the city of Hanoi and in the surrounding rural districts. Due to naturally occurring organic matter in the sediments, the groundwaters are anoxic and rich in iron. With an average arsenic concentration of 159 micrograms/L, the contamination levels varied from 1 to 3050 micrograms/L in rural groundwater samples from private small-scale tubewells. In a highly affected rural area, the groundwater used directly as drinking water had an average concentration of 430 micrograms/L. Analysis of raw groundwater pumped from the lower aquifer for the Hanoi water supply yielded arsenic levels of 240-320 micrograms/L in three of eight treatment plants and 37-82 micrograms/L in another five plants. Aeration and sand filtration that are applied in the treatment plants for iron removal lowered the arsenic concentrations to levels of 25-91 micrograms/L, but 50% remained above the Vietnamese Standard of 50 micrograms/L. Extracts of sediment samples from five bore cores showed a correlation of arsenic and iron contents (r2 = 0.700, n = 64). The arsenic in the sediments may be associated with iron oxyhydroxides and released to the groundwater by reductive dissolution of iron. Oxidation of sulfide phases could also release arsenic to the groundwater, but sulfur concentrations in sediments were below 1 mg/g. The high arsenic concentrations found in the tubewells (48% above 50 micrograms/L and 20% above 150 micrograms/L) indicate that several million people consuming untreated groundwater might be at a considerable risk of chronic arsenic poisoning.

Field assessment of nanoscale bimetallic particles for groundwater treatment.

Abstract: A field demonstration was performed in which nanoscale bimetallic (Fe/Pd) particles were gravity-fed into groundwater contaminated by trichloroethene and other chlorinated aliphatic hydrocarbons at a manufacturing site. With diameters on the order of 100−200 nm, the nanoparticles are uniquely suited to rapidly degrade redox-amenable contaminants and for optimal subsurface delivery and dispersion. Approximately 1.7 kg of the nanoparticles was fed into the test area over a 2-day period, resulting in minimal clogging of the injection well. The test area was located within a well-characterized region of the contaminant plume and included an injection well and three piezometer couplets spaced 1.5 m apart. Despite the low nanoparticle dosage, trichloroethene reduction efficiencies of up to 96% were observed over a 4-week monitoring period with the highest values observed at the injection well and adjacent piezometers. Data from the field assessment were consistent with the results of pre-injection laboratory st...

Compound-Specific, Quantitative Characterization of Organic Fluorochemicals in Biological Matrices

Abstract: Since the early 1980s, there has been a steady increase in the use of nonvolatile fluorinated organic compounds for a variety of industrial and commercial applications. The industrial use of these relatively stable compounds has initiated debate over the fate of fluorochemicals in the environment and, ultimately, the bioavailability of these compounds. In this manuscript, we present quantitative results from a study of 65 human sera samples purchased from biological supply companies that provide characterization of specific organic fluorochemicals present in the sera of nonindustrially exposed humans. Summed together, the compound-specific characterization data reported here agree closely with levels of nonspeciated organic fluorine that were originally reported to be present in sera in 1970. The compound-specific method for the extraction of extremely low levels of several commercial organic fluorochemicals from sera and liver with quantitative detection by negative ion electrospray tandem mass spectrometry described represents a robust, previously undescribed approach to quantifying specific organic fluorochemicals in biological matrices.

Generic NICA−Donnan Model Parameters for Metal-Ion Binding by Humic Substances

Abstract: Forty-nine datasets consisting of literature and experimental data for proton binding by fulvic and humic acids have been analyzed using the NICA-Donnan model. The model successfully described the behavior of the individual datasets with a high degree of accuracy and highlighted the differences in site density and binding affinity between fulvic acids (FA) and humic acids (HA) while demonstrating their strong similarities. The data have also been used to derive generic model descriptions of proton binding by FA and HA that can be used for modeling in the absence of specific parameter sets for the particular humic substance of interest. These generic parameters can provide estimates of the amount of proton binding by a wide variety of humic substances to within approximately ±20% under any given conditions. The maximum site density for protons was 7.74 and 5.70 equiv kg-1 for a generic FA and HA, respectively. The recommended generic NICA-Donnan parameter values for FA are b = 0.57, Qmax1,H = 5.88, log KH...

Determination of endocrine-disrupting phenolic compounds and estrogens in surface and drinking water by HRGC-(NCI)-MS in the picogram per liter range.

Abstract: A method for the analysis of phenolic estrogenic active compounds in surface and drinking water in the picogram per liter range is described. Besides the widely used monomer bisphenol A, 4-tert-octylphenol [4-(1,1,3,3-tetramethylbutyl)phenol] and the technical isomer mixture of 4-nonylphenol; phenolic steroid hormones such as the endogenous estrogens estrone, 17α-estradiol, and 17β-estradiol; and the exogenous estrogen 17α-ethinylestradiol were determined in water at the 20−200 pg/L level. Water samples from 1 to 5 L were extracted by solid-phase extraction (SPE) on a cartridge system containing LiChrolut EN as sorbent. The phenols and steroids were converted into their pentafluorobenzoylate esters in an extractive derivatization reaction. The derivatives were then determined by high-resolution gas chromatography with negative chemical ionization mass spectrometric detection (HRGC−(NCI)−MS) in the selected ion mode (SIM). All results were also confirmed by HRGC with electron capture detection (ECD). This ...

Biohydrogen production as a function of ph and substrate concentration

Abstract: The conversion of organics in wastewaters into hydrogen gas could serve the dual role of renewable energy production and waste reduction. The chemical energy in a sucrose rich synthetic wastewater was recovered as hydrogen gas in this study. Using fractional factorial design batch experiments, the effect of varying pH (4.5-7.5) and substrate concentration (1.5-44.8 g COD/L) and their interaction on hydrogen gas production were tested. Mixed bacterial cultures obtained from a compost pile, a potato field, and a soybean field were heated to inhibit hydrogen-consuming methanogens and to enrich sporeforming, hydrogen-producing acidogens. It was determined that the highest rate (74.7 mL H2/(L*h)) of hydrogen production occurred at a pH of 5.5 and a substrate concentration of 7.5 g COD/Lwith a conversion efficiency of 38.9 mL H2/(g COD/L). The highest conversion efficiency was 46.6 mL H2/(g COD/L).

Fluorescence excitation-emission matrix characterization of some sewage-impacted rivers.

Abstract: Fluorescence excitation-emission matrix (EEM) spectrophotometry was applied to 10 sample sites in six rivers in northeastern England, some of which were adversely impacted by sewage treatment works (STW) discharges, with the aim to investigate whether STW discharge has a significantly distinct fluorescence signature. Upstream, downstream, and STW discharge samples for two STWs demonstrated that treated sewage has a distinct fluorescence EEM, with high tryptophan and fulvic-like fluorescence intensities that are of approximately equal ratio. This signature could be seen in downstream samples. When all 10 sample locations were compared, two trend lines were apparent where STW impacted rivers plotted separately from the other sample locations. Fluorescence EEM signatures were compared to absorption at 254 nm and demonstrated to provide a better fingerprint of sewage-impacted water. It is suggested that fluorescence EEM spectrophotometry can provide a useful tool for the analysis of grab samples taken for both routine and investigative monitoring and has the potential for on-line monitoring of STW impacts on river systems.

Influence of chemical and biological factors on trophic transfer of persistent organic pollutants in the northwater polynya marine food web.

Abstract: Persistent organic pollutants (POPs) and stable isotopes of nitrogen (δ15N) were measured in zooplankton (6 species), a benthic invertebrate (Anonyx nugax), Arctic cod (Boreogadus saida), seabirds (6 species), and ringed seals (Phoca hispida) collected in 1998 in the Northwater Polynya to examine effects of biological and chemical factors on trophic transfer of POPs in an Arctic marine food web. Strong positive relationships were found between recalcitrant POP concentrations (lipid corrected) and trophic level based on stable isotopes of nitrogen, providing clear evidence of POP biomagnification in Arctic marine food webs. Food web magnification factors (FWMFs), derived from the slope of the POP−trophic level relationship, provided an overall magnification factor for the food web but over and underestimated biomagnification factors (BMFs) based on predator−prey concentrations in poikilotherms (fish) and homeotherms (seabirds and mammals), respectively. Greater biomagnification in homeotherms was attribute...

Chemical Characterization of Fine Particle Emissions from Fireplace Combustion of Woods Grown in the Northeastern United States

Abstract: The fireplace combustion of wood is a significant and largely unregulated source of fine particle pollution in the United States. Source apportionment techniques that use particulate organic compounds as tracers have been successful in determining the contribution of wood smoke to ambient fine particle levels in specific areas in California. To apply these techniques to the rest of the United States, the differences in emissions profiles between different wood smoke sources and fuel types should be resolved. To this end, a series of fireplace source tests was conducted on six fuel wood species found in the Southern United States to determine fine particulate emission factors for total mass, ionic and elemental species, elemental and organic carbon, and over 250 individual organic compounds. The wood species tested, chosen for their high abundance and availability in the Southern U.S. region, were yellow poplar, white ash, sweetgum, mockernut hickory, loblolly pine, and slash pine. The differences in the emissions of compounds such as substituted phenols and resin acids help to distinguish between the smoke from hardwood and softwood combustion. Levoglucosan, a cellulose pyrolysis product which may serve as a tracer for wood smoke in general, was quantified in the emissions from all the wood species burned. The furofuran lignan, yangambin, which was emitted in significant quantities from yellow poplar combustion and not detected in any of the other North American wood smokes, is a potential species-specific molecular tracer which may be useful in qualitatively identifying particulate emissions from a specific geographical area where yellow poplar is being burned.

Study of Au/Au3+-TiO2 Photocatalysts toward Visible Photooxidation for Water and Wastewater Treatment

Abstract: With an attempt to extend light absorption of TiO2-based photocatalyst toward the visible light range and eliminate the rapid recombination of excited electrons/holes during photoreaction, a new type of photocatalysts (Au/Au3+-TiO2) powder was prepared by a photoreduction/sol−gel process. The crystal phase composition, surface structure, and light absorption of the new photocatalysts were comprehensively examined by X-ray differential detection (XRD), UV−visible absorption spectra, X-ray photoelectron emission spectroscopy (XPS), and photoluminescence (PL) spectra. The photooxidation efficiencies of the photocatalysts were also evaluated in the photodegradation of methylene blue (MB) in aqueous solutions under visible light irradiation from a high-pressure sodium lamp (λ > 400 nm). The results of PL analyses in this study indicated that the gold/gold ion-doping on the surface of TiO2 could eliminate the electron/holes recombination and also increase the light absorption in the visible range. The analytica...

Removal of endocrine-disrupting chemicals in activated sludge treatment works

Abstract: The release of endocrine-disrupting chemicals into the aquatic environment has raised the awareness of the central role played by sewage treatment in lowland water quality. This review focuses on the activated sludge process, which is commonly used to treat sewage in large towns and cities and which successfully removes the bulk of the organic compounds that enter the works. However, not all compounds are completely broken down or converted to biomass. For example, the estrogenic alkylphenols and steroid estrogens found in effluent are the breakdown products of incomplete breakdown of their respective parent compounds. Batch microcosm studies have indicated that estrone, ethinylestradiol, and alkylphenols will not be completely eliminated in activated sludge over typical treatment times. Field data suggest that the activated sludge treatment process can consistently remove over 85% of estradiol, estriol, and ethinylestradiol. The removal performance for estrone appears to be less and is more variable. Because of its relatively high hydrophobicity, the accumulation of alkylphenol in sludge has been observed. Although it has not been examined, accumulation of ethinylestradiol in sludge is a possibility due to its recalcitrance and hydrophobicity. A comparison between the concentrations of some of the major endocrine-active chemicals in effluents and their biological potencies has been made, to direct attention to the chemicals of most concern. While water purification techniques such as UV or activated charcoal could significantly remove these microorganic contaminants, the high costs involved suggest that research into the potential for treatment optimization should receive more attention.

Impact of biodiesel source material and chemical structure on emissions of criteria pollutants from a heavy-duty engine.

Abstract: Biodiesel is an oxygenated diesel fuel made from vegetable oils and animal fats by conversion of the triglyceride fats to esters via transesterification. In this study we examined biodiesels produced from a variety of real-world feedstocks as well as pure (technical grade) fatty acid methyl and ethyl esters for emissions performance in a heavy-duty truck engine. The objective was to understand the impact of biodiesel chemical structure, specifically fatty acid chain length and number of double bonds, on emissions of NOx and particulate matter (PM). A group of seven biodiesels produced from real-world feedstocks and 14 produced from pure fatty acids were tested in a heavy-duty truck engine using the U.S. heavy-duty federal test procedure (transient test). It was found that the molecular structure of biodiesel can have a substantial impact on emissions. The properties of density, cetane number, and iodine number were found to be highly correlated with one another. For neat biodiesels, PM emissions were essentially constant at about 0.07 g/bhp-h for all biodiesels as long as density was less than 0.89 g/cm3 or cetane number was greater than about 45. NOx emissions increased with increasing fuel density or decreasing fuel cetane number. Increasing the number of double bonds, quantified as iodine number, correlated with increasing emissions of NOx. Thus the increased NOx observed for some fuels cannot be explained by the NOx/PM tradeoff and is therefore not driven by thermal NO formation. For fully saturated fatty acid chains the NOx emission increased with decreasing chain length for tests using 18, 16, and 12 carbon chain molecules. Additionally, there was no significant difference in NOx or PM emissions for the methyl and ethyl esters of identical fatty acids.

Harvesting Energy from the Marine Sediment−Water Interface

Abstract: Pairs of platinum mesh or graphite fiber-based electrodes, one embedded in marine sediment (anode), the other in proximal seawater (cathode), have been used to harvest low-level power from natural, microbe established, voltage gradients at marine sediment−seawater interfaces in laboratory aquaria. The sustained power harvested thus far has been on the order of 0.01 W/m2 of electrode geometric area but is dependent on electrode design, sediment composition, and temperature. It is proposed that the sediment/anode−seawater/cathode configuration constitutes a microbial fuel cell in which power results from the net oxidation of sediment organic matter by dissolved seawater oxygen. Considering typical sediment organic carbon contents, typical fluxes of additional reduced carbon by sedimentation to sea floors < 1000 m deep, and the proven viability of dissolved seawater oxygen as an oxidant for power generation by seawater batteries, it is calculated that optimized power supplies based on the phenomenon demonstr...

Validation of an Arsenic Sequential Extraction Method for Evaluating Mobility in Sediments

Abstract: Arsenic (As) mobility and transport in the environment are strongly influenced by arsenic's associations with solid phases in soil and sediment. We have tested a sequential extraction procedure intended to differentiate the following pools of solid phase arsenic: loosely and strongly adsorbed As; As coprecipitated with metal oxides or amorphous monosulfides; As coprecipitated with crystalline iron (oxyhydr)oxides; As oxides; As coprecipitated with pyrite; and As sulfides. Additions of As-bearing phases to wetland and riverbed sediment subsamples were quantitatively recovered by the following extractants of the sequential extraction procedure: As adsorbed on goethite, 1 M NaH2PO4; arsenic trioxide (As2O3), 10 M HF; arsenopyrite (FeAsS), 16 N HNO3; amorphous As sulfide, 1 N HCI, 50 mM Ti-citrate-EDTA, and 16 N HNO3; and orpiment (As2S3), hot concentrated HNO3/H2O2. Wet sediment subsamples from both highly contaminated wetland peat and less As-rich sandy riverbed sediment were used to test the extraction procedure for intra-method reproducibility. The proportional distribution of As among extractant pools was consistent for subsamples of the wetland and for subsamples of the riverbed sediments. In addition, intermethod variability between the sequential extraction procedure and a single-step hot concentrated HNO3/H2O2 acid digestion was investigated. The sum of the As recovered in the different extractant pools was not significantly different than results for the acid digestion.

Flame retardants in indoor air at an electronics recycling plant and at other work environments.

Abstract: Air samples from a plant engaged in recycling electronics goods, a factory assembling printed circuit boards, a computer repair facility, offices equipped with computers, and outdoor air have been analyzed with respect to their content of brominated hydrocarbon and phosphate ester flame retardants. Polybrominated diphenyl ethers, polybrominated biphenyls, 1,2-bis(2,4,6-tribromophenoxy)-ethane, tetrabromobisphenol A, and organophosphate esters were all detected in the indoor air samples, with the highest concentrations being detected in air from the recycling plant. In air from the dismantling hall at the recycling plant the average concentrations of decabromodiphenyl ether, tetrabromobisphenol A, and triphenyl phosphate were 38, 55, and 58 pmol/m3, respectively. Significantly higher levels of all of these additives were present in air in the vicinity of the shredder at the dismantling plant. This is the first time that 1,2-bis(2,4,6-tribromophenoxy)-ethane and several arylated phosphate esters are reported to be contaminants of air in occupational settings. At all of the other sites investigated, low levels of flame retardants were detected in the indoor air. Flame retardants associated with airborne particles, present at elevated levels, pose a potential health hazard to the exposed workers.

Peer Reviewed: What Future for Carbon Capture and Sequestration?

Abstract: New technologies could reduce carbon dioxide emissions to the atmosphere while still allowing the use of fossil fuels

Accumulation of Perfluorooctane Sulfonate in Marine Mammals

Abstract: Perfluorooctane sulfonate (PFOS) is a perfluorinated molecule that has recently been identified in the sera of nonindustrially exposed humans. In this study, 247 tissue samples from 15 species of marine mammals collected from Florida, California, and Alaskan coastal waters; the northern Baltic Sea; the Arctic (Spitsbergen); and Sable Island in Canada were analyzed for PFOS. PFOS was detected in liver and blood of marine mammals from most locations including those from Arctic waters. The greatest concentrations of PFOS found in liver and blood were 1520 ng/g wet wt in a bottlenose dolphin from Sarasota Bay, FL, and 475 ng/mL in a ringed seal from the northern Baltic Sea (Bothnian Sea), respectively. No age-dependent increase in PFOS concentrations in marine mammals was observed in the samples analyzed. The occurrence of PFOS in marine mammals from the Arctic waters suggests widespread global distribution of PFOS including remote locations.

The hygroscopic properties of dicarboxylic and multifunctional acids: measurements and UNIFAC predictions.

Abstract: The role of water-soluble organic compounds on the hygroscopic properties of atmospheric aerosols has recently been the subject of many studies. In particular, low molecular weight dicarboxylic acids and some multifunctional organic acids have been found or are expected to exist in atmospheric aerosols in urban, semiurban, rural, and remote sites. Unlike for their inorganic counterparts, the hygroscopic properties of organic acids have not been well characterized. In this study, the hygroscopic properties of selected water-soluble dicarboxylic acids (oxalic acid, malonic acid, succinic acid, and glutaric acid) and multifunctional acids (citric acid, DL-malic acid, and L-(+)-tartaric acid) were studied using single droplets levitated in an electrodynamic balance at 25 degrees C. The water activities of bulk samples of dilute solutions were also measured. Solute evaporation was observed in the dicarboxylic acids but not in the multifunctional acids. Oxalic acid, succinic acid, and glutaric acid droplets crystallize upon evaporation of water, but, except for glutaric acid droplets, do not deliquesce even at 90% relative humidity (RH). Mass transfer limitation of the deliquescence process was observed in glutaric acid. Neither crystallization nor deliquescence was observed in malonic acid, citric acid, DL-malic acid, or L-(+)-tartaric acid. Malonic acid and these three hydroxy-carboxylic acids absorb water even at RH much lower than their respective deliquescence RH. The growth factor (Gf), defined as the ratio of the particle diameter at RH = 10% to that at RH = 90%, of oxalic acid and succinic acid was close to unity, indicating no hygroscopicity in this range. The remaining acids (malonic acid, glutaric acid, citric acid, malic acid, and tartaric acid) showed roughly similar hygroscopicity of a Gf of 1.30-1.53, which is similar to that of "more hygroscopic" aerosols in field measurements reported in the literature. A generalized equation for these four acids, Gf = (1-aw)-0.163, was developed to represent the hygroscopicity of these acids. Water activity predictions from calculations using the UNIFAC model were found to agree with the measured water activity data to within 40% for most of the acids but the deviations were as large as about 100% for malic acid and tartaric acid. We modified the functional group interaction parameters of the COOH(-H20, OH-H20, and OH-COOH pairs by fitting the UNIFAC model with the measured data. The modified UNIFAC model improves the agreement of predictions and measurements to within 38% for all the acids studied.

A new method to measure effective soil solution concentration predicts copper availability to plants

Abstract: Risk assessments of metal contaminated soils need to address metal bioavailability. To predict the bioavailability of metals to plants, it is necessary to understand both solution and solid phase supply processes in soils. In striving to find surrogate chemical measurements, scientists have focused either on soil solution chemistry, including free ion activities, or operationally defined fractions of metals. Here we introduce the new concept of effective concentration, CE, which includes both the soil solution concentration and an additional term, expressed as a concentration, that represents metal supplied from the solid phase. CE was measured using the technique of diffusive gradients in thin films (DGT) which, like a plant, locally lowers soil solution concentrations, inducing metal supply from the solid phase, as shown by a dynamic model of the DGT−soil system. Measurements of Cu as CE, soil solution concentration, by EDTA extraction and as free Cu2+ activity in soil solution were made on 29 different...

Arsenate and Arsenite Removal by Zerovalent Iron: Effects of Phosphate, Silicate, Carbonate, Borate, Sulfate, Chromate, Molybdate, and Nitrate, Relative to Chloride

Abstract: Batch tests were performed to evaluate the effects of inorganic anion competition on the kinetics of arsenate (As(V)) and arsenite (As(III)) removal by zerovalent iron (Peerless Fe0) in aqueous solution. The oxyanions underwent either sorption-dominated reactions (phosphate, silicate, carbonate, borate, and sulfate) or reduction-dominated reactions (chromate, molybdate, and nitrate) with Peerless Fe0 in the presence of As(V) or As(III), relative to chloride. Pseudo-first-order rate equations were found to describe satisfactorily both As(V) and As(III) removal kinetics in the presence of each competing anion. Of the oxyanions tested for Peerless Fe0 in the pH range from 7 to 9, phosphate caused the greatest decrease in As removal rate (7.0 × 10-3 to 18.5 × 10-3 h-1) relative to chloride (34.9 × 10-3 to 36.2 × 10-3 h-1). Silicate, chromate, and molybdate also caused strong inhibition of As removal, followed by carbonate and nitrate, whereas borate and sulfate only caused slight inhibition to As(III) removal...

Source apportionment of urban particulate aliphatic and polynuclear aromatic hydrocarbons (PAHs) using multivariate methods

Abstract: Samples of organic aerosol were collected in Santiago de Chile. An activated-charcoal diffusion denuder was used to strip out organic vapors prior to particle collection. Both polynuclear aromatic hydrocarbons (PAHs) and aliphatic hydrocarbons were determined using gas chromatography/mass spectrometry (GC/MS). Organic particle sources were resolved using both concentration diagnostic ratios and multivariate methods such as hierarchical cluster analysis (HCA) and factor analysis (FA). Four factors were identified based on the loadings of PAHs and n-alkanes and were attributed to the following sources: (1) high-temperature combustion of fuels; (2) fugitive emissions from oil residues; (3) biogenic sources; and (4) unburned fuels. Multilinear regression (MLR) analysis was used to determine emission profiles and contributions of the sources. The reconstructed concentrations of particle phase aliphatic and polynuclear aromatic hydrocarbons were in good agreement (R2 > 0.70) with those measured in Santiago de Chile.

Arsenate and arsenite removal by zerovalent iron: kinetics, redox transformation, and implications for in situ groundwater remediation.

Abstract: Batch tests were performed utilizing four zerovalent iron (Fe0) filings (Fisher, Peerless, Master Builders, and Aldrich) to remove As(V) and As(III) from water. One gram of metal was reacted headspace-free at 23 °C for up to 5 days in the dark with 41.5 mL of 2 mg L-1 As(V), or As(III) or As(V) + As(III) (1:1) in 0.01 M NaCl. Arsenic removal on a mass basis followed the order: Fisher > Peerless ≈ Master Builders > Aldrich; whereas, on a surface area basis the order became: Fisher > Aldrich > Peerless ≈ Master Builders. Arsenic concentration decreased exponentially with time, and was below 0.01 mg L-1 in 4 days with the exception of Aldrich Fe0. More As(III) was sorbed than As(V) by Peerless Fe0 in the initial As concentration range between 2 and 100 mg L-1. No As(III) was detected by X-ray photoelectron spectroscopy (XPS) on Peerless Fe0 at 5 days when As(V) was the initial arsenic species in the solution. As(III) was detected by XPS at 30 and 60 days present on Peerless Fe0, when As(V) was the initial ...

Using time- and size-resolved particulate data to quantify indoor penetration and deposition behavior.

Abstract: Because people spend approximately 85−90% of their time indoors, it is widely recognized that a significant portion of total personal exposures to ambient particles occurs in indoor environments. Although penetration efficiencies and deposition rates regulate indoor exposures to ambient particles, few data exist on the levels or variability of these infiltration parameters, in particular for time- and size-resolved data. To investigate ambient particle infiltration, a comprehensive particle characterization study was conducted in nine nonsmoking homes in the metropolitan Boston area. Continuous indoor and outdoor PM2.5 and size distribution measurements were made in each of the study homes over weeklong periods. Data for nighttime, nonsource periods were used to quantify infiltration factors for PM2.5 as well as for 17 discrete particle size intervals between 0.02 and 10 μm. Infiltration factors for PM2.5 exhibited large intra- and interhome variability, which was attributed to seasonal effects and home d...

Hybrid organic/inorganic reverse osmosis (RO) membrane for bactericidal anti-fouling. 1. Preparation and characterization of TiO2 nanoparticle self-assembled aromatic polyamide thin-film-composite (TFC) membrane.

Abstract: Hybrid organic/inorganic reverse osmosis (RO) membranes composed of aromatic polyamide thin films underneath titanium dioxide (TiO2) nanosized particles have been fabricated by a self-assembly process, aiming at breakthrough of biofouling problems. First, positively charged particles of the colloidal TiO2 were synthesized by a sol−gel process, and the diameter of the resulting particles in acidic aqueous solution was estimated to be ≈2 nm by analyzing the UV−visible absorption characteristics with a quantum mechanical model developed by Brus. Transmission electron microscopy (TEM) further confirmed the formation of the quantum-sized TiO2 particles (∼10 nm or less). The TiO2 particles appeared to exist in the crystallographic form of anatase as observed with the X-ray diffraction (XRD) pattern in comparison with those of commercial 100% rutile and commercial 70:30% anatase-to-rutile mixture. The hybrid thin-film-composite (TFC) aromatic polyamide membranes were prepared by self-assembly of the TiO2 nanopar...

Rhizosphere bacteria mobilize Zn for hyperaccumulation by Thlaspi caerulescens.

Abstract: Thlaspi caerulescens has a remarkable ability to hyperaccumulate Zn from soils containing mostly nonlabile Zn. The present study shows that rhizosphere microbes play an important role in increasing the availability of water-soluble Zn in soil, thus enhancing Zn accumulation by T. caerulescens. The addition of bacteria to surface-sterilized seeds of T. caerulescens sown in autoclaved soil increased the Zn concentration in shoots 2-fold as compared to axenic controls; the total accumulation of Zn was enhanced 4-fold. When the same experiment was conducted with Thlaspi arvense, a nonaccumulator, bacteria had no effect on shoot Zn accumulation although they increased water-soluble Zn concentrations available to both Thlaspi species by 22-67% as compared to the axenic controls. Further evidence that bacteria increase the availability of water-soluble Zn in soil was obtained when liquid media that had supported bacterial growth mobilized 1.3-1.8-fold more Zn from soil as compared to axenic media. Other experiments with agar media showed that bacteria did not facilitate an increase in the rate of soluble Zn transport into the root nor did they enlarge the surface area of the roots of either Thlaspi species. Thus, the bacterially mediated increase in the dissolution of Zn from the nonlabile phase in soil may enhance Zn accumulation in T. caerulescens shoots.

Atmospheric aerosol over Vermont: chemical composition and sources.

Abstract: Aerosol chemical composition data for PM2.5 samples collected during the period from 1988 to 1995 at Underhill, VT, were analyzed. Sulfur and black carbon mass concentrations ranged from 0.01 to 6.5 μg m-3 and from 0.05 to 2.2 μg m-3, respectively, while the total fine aerosol mass concentration ranged from 0.2 to 51.1 μg m-3. Seasonal variations with maxima during the summer and minima in winter/spring were observed for sulfur and the fine mass concentrations. No annual pattern was observed for black carbon. Seasonal variations for most of the other anthropogenic species had maxima in winter and spring and minima in the summer. A factor analysis method, positive matrix factorization (PMF), utilizing error estimates of the data to provide optimum data point scaling was used to obtain information about possible sources of the aerosol. An 11-factor solution was obtained. The six sources representing wood burning, coal and oil combustion, coal combustion emissions plus photochemical sulfate production, metal...