Metribuzin degradation by membrane anodic Fenton treatment and its interaction with ferric ion

Metribuzin, a widely used herbicide and a frequently detected pollutant in the environment, was studied as a target compound for membrane anodic Fenton treatment (AFT), a Fenton technology with application potential for on-site treatment of pesticide wastewater. It was found that the degradation kinetics of metribuzin do not obey the AFT model, a previously developed model that fit AFT degradation kinetics of all previously investigated pesticides. The lack of fit for metribuzin data was determined to result from a weak interaction between metribuzin and the ferric ion, resulting in a significant reduction in availability of metribuzin for reaction with hydroxyl radicals during AFT, thus slowing degradation. A revised kinetic model was developed based on the original AFT model with the addition of this interaction. Results demonstrate that the new kinetic model fits metribuzin degradation data quite well at different delivery rates of Fenton reagent and at different temperatures. This weak interaction is also found to exist between ferric ion and several other triazinone/triazine herbicides during membrane AFT. The interaction intensity correlates with the electron-withdrawing/-donating property of substituents on the triazine/triazinone ring. The stronger the electron-donating ability of substituents, the stronger the interaction.     

Visible-light-assisted degradation of dye pollutants over Fe(III)-loaded resin in the presence of H2O2 at neutral pH values

A novel catalyst was synthesized by direct exchange of ferric ions onto a cationic resin (Amberlite IRA200). Upon visible light irradiation (lambda > 420 nm) in the presence of H2O2, this catalyst was found to be highly effective for the degradation of nonbiodegradable cationic dyes, Malachite green, Rhodamine B, and Methylene blue, even at neutral pH values. It was also easy to separate from the degraded solution. By total organic carbon, FT-IR, and GC-MS analysis, the degradation process of Malachite green was shown to proceed with demethylation and phenyl ring openings into CO2 and small molecular compounds. EPR studies revealed that *OH radicals, other than *OOH/O2*-, were involved as the active species. A possible reaction mechanism is proposed on the basis of all the information obtained under various experimental conditions.     

Measurements of OH reactivity and photochemical ozone production in the urban atmosphere

Measurements of OH reactivity (i.e., OH loss rates) in the troposphere are essential for discussing tropospheric OH photochemistry. In July and August 2003, we observed the total OH reactivity in a suburban area of Tokyo. More than 90% of the data of the measured OH loss rates were higher than the calculated values with simultaneously measured concentrations of various trace species even though the rate coefficient of the OH + NO2 reaction was measured by us. We concluded that this discrepancy is due to the existence of unmeasured volatile organic compounds (VOCs). We estimated the potential of the photochemical ozone production in the case of including the unknown species as VOCs and excluding the missing sink, respectively. When the unknown species were included as VOCs, the potential increases from 32% to 88%. This result indicates the photochemical production rates of ozone in the urban air are substantially greater than expected.     

Assessment of Efficiency of Repellent Formulations with N,N-diethyl-m-toluamide in Laboratory Conditions

The affinity of N,N-diethyl-m-toluamide) (DEET) for various polymers that are potential inert carriers (PEG, PVP, NaCMC, PAA) was studied. Mixtures of DEET and the polymers were prepared and analysed for DEET vapour release using head space analysis. Polyvinylpyrrolidone (PVP) showed the highest affinity for DEET. Several insect repellent formulations in the form of a hydrogel, an o/w cream and a stick were prepared with 5% w/w DEET and either 1% w/w or no PVP. The release of DEET from the formulations was investigated by Head Space gas-mass spectrometry at 32 degrees C. The degree of absorption of DEET through the skin was evaluated by applying these topical preparations to shaved rabbit skin and measuring DEET content in the blood samples by gas-mass spectrometry at various time intervals after application. Based on these results the pharmacokinetic parameters were determined. The minimum penetration of DEET through rabbit skin was obtained with a hydrogel containing PVP as a carrier. The biological efficiency of repellent formulations containing 5% DEET (w/w) was evaluated for repellency using the mosquito Aedes aegypti. The results demonstrated that the hydrogel formulation based on polyacrylic acid containing 5% DEET (w/w) supplemented with 1% PVP (w/w), could serve as a suitable vehicle for repellent preparations containing DEET.     

Degradation of cationic red GTL by catalytic wet air oxidation over Mo-Zn-Al-O catalyst under room temperature and atmospheric pressure

To overcome the drawback of catalytic wet air oxidation (CWAO) with high temperature and high pressure, the catalytic activity of Mo-Zn-Al-O catalyst for degradation of cationic red GTL under room temperature and atmospheric pressure was investigated. Mo-Zn-Al-O catalyst was prepared by coprecipitation and impregnation. XRD, TG-DTG, and XPS were used to characterize the resulting sample. Central composition design using response surface methodology was employed to optimize correlation of factors on the decolorization of cationic red GTL. The results show that the optimal conditions of pH value, initial concentration of dye and catalyst dosage were found to be 4.0, 85 mg/L and 2.72 g/L, respectively, for maximum decolorization of 80.1% and TOC removal of 50.9%. Furthermore, the reaction on the Mo-Zn-Al-O catalyst and degradation mechanism of cationic red GTL was studied by Electron spin resonance (ESR) and GC-MS technique. The possible reaction mechanism was that the Mo-Zn-Al-O catalyst can efficiently react with adsorbed oxygen/H(2)O to produce ·OH and (1)O(2) and finally induce the degradation of cationic red GTL. GC-MS analysis of the degradation products indicates that cationic red GTL was initiated by the cleavage of -N ═ N- and the intermediates were further oxidized by ·OH or (1)O(2).     

Decomposition of hydrogen peroxide and organic compounds in the presence of dissolved iron and ferrihydrite

This work examines the contribution of solution phase reactions, especially those involving a chain reaction mechanism, to the decomposition of hydrogen peroxide (H2O2) and organic compounds in the presence of dissolved iron and ferrihydrite. In solutions at pH 4, where Fe was introduced as dissolved Fe(III), both H2O2 and 14C-labeled formic acid decomposed at measurable rates that agreed reasonably well with those predicted by a kinetic model of the chain reaction mechanism, using published rate constants extrapolated to pH 4. The ratio of the formic acid and H2O2 decomposition rates, as well as the dramatic effect of tert-butyl alcohol on these rates, confirmed that a solution chain reaction mechanism involving *OH controlled the decomposition kinetics of both compounds. In the presence of ferrihydrite as the iron source, the ratio of the rate of formic acid decomposition to that of H2O2 decomposition was significantly lower than that observed in the presence of only dissolved Fe. Moreover, neither rate diminished drastically upon addition of tert-butyl alcohol, indicating that the solution phase chain reaction is not a dominant decomposition pathway of H2O2 and formic acid. Relative decomposition rates of formic acid and a second *OH probe, benzoic acid, were consistent with oxidation of these compounds by *OH. These observations can be reproduced by a kinetic model including (a) decomposition of H2O2 at the iron oxide surface, producing *OH with lower yield than the reaction sequence with dissolved Fe, and (b) low concentrations of dissolved Fe in the presence of ferrihydrite, preventing propagation of the solution phase chain reaction.     

Mechanism for OH-initiated degradation of 2,3,7,8-tetrachlorinated dibenzo-p-dioxins in the presence of O2 and NO/H2O

The atmospheric oxidation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TeCDD) is investigated theoretically by high-accuracy molecular orbital calculation. The study shows that the OH radical can easily be added to the C atom adjacent to the O atom in dioxin ring to form OH radical adduct. The 2,3,7,8-TeCDD-OH adduct can immediately react with O(2) to form the 2,3,7,8-TeCDD-OH-O(2) adduct which can react with NO or H(2)O to complete the decomposition process. The degradation mechanism varies with the addition position of O(2) and the O-abstraction by NO. The OH radical can be reproduced through the H-abstraction of H(2)O and initiate a new round of degradation. The direct dynamic calculation is performed, and the rate constants is calculated over a temperature range of 200-1200 K, using the canonical variational transition state theory with small-curvature tunneling effect. The four-parameter formula of rate constants with the temperature is fitted and the lifetimes of the reaction species in the troposphere are estimated according to the rate constants, which is helpful for the atmospheric model study on the formation and degradation of dioxin.     

Anchored oxygen-donor coordination to iron for photodegradation of organic pollutants

A photocatalyst of oxygen-donor coordination to iron, complex of 5-sulfosalicylic acid (SSA) with ferric ion, supported on resin to cycle Fe3+/Fe2+ center under visible irradiation can effectively generate *OH radicals from H2O2, leading to degradation of organic pollutants in water. The higher turnover number was achieved by this catalyst for the degradation of model compound than those reported for the general N-donor ligands catalysts. The reversible "on/ off" switching of Fe3+/Fe2+ complexation with SSA, coupled with the phenol/phenoxyl radical conversion of the o-phenoxyl moiety of SSA, produces an ideal catalytic system that separates the Fenton reaction and the followed oxidations by *OH radicals (in water phase) from the regeneration of the catalytic species, Fe (SSA)2-, which occurs on the surface of resin. This system not only inhibits the undesired destruction of the ligands by *OH radicals, improving the stability of the catalyst, but also avoids the unnecessary decomposition of H2O2 into HO2* that occurs in the homogeneous Fenton system. Therefore, the system suggests an efficient utilization of H2O2 for degradation of organic pollutants.     

Studies on the atmospheric degradation of chlorpyrifos-methyl

The gas-phase atmospheric degradation of chlorpyrifos-methyl (a widely used organophosphate insecticide in Southern European regions) has been investigated at the large outdoor European Photoreactor (EUPHORE) in Valencia, Spain. Photolysis under sunlight conditions and reaction with ozone were shown to be unimportant. The rate constant for reaction of chlorpyrifos-methyl with OH radicals was measured using a conventional relative rate method with cyclohexane and n-octane employed as reference compounds with k = (4.1 ± 0.4) × 10(-11) cm(3) molecule(-1) s(-1) at 300 ± 5 K and atmospheric pressure. The available evidence indicates that tropospheric degradation of chlorpyrifos-methyl is mainly controlled by reaction with OH radicals and that the tropospheric lifetime is estimated to be around 3.5 h. Significant aerosol formation was observed following the reaction of chlorpyrifos-methyl with OH radicals, and the main carbon-containing products detected in the gas phase were chlorpyrifos-methyl oxone and 3,5,6-trichloro-2-pyridinol.     

Kinetics and mechanism of photoactivated periodate reaction with 4-chlorophenol in acidic solution

The application of photoactivated periodate (UV/IO4-) to the degradation of 4-chlorophenol (4-CP) was explored in this study. Under low irradiation intensities (23 microW/cm2), wavelength of 266 nm, and pH 3, 4-CP was observed to degrade by pseudo-first-order reaction kinetics. The small reduction in 4-CP degradation in the presence of tert-butyl alcohol (t-BuOH) suggests that degradation of 4-CP by UV/IO4- was not dominated by an OH* pathway. O3 production was suppressed in the presence of t-BuOH under O2-limited environments and in the presence of 4-CP. Faster degradation of 4-CP in the presence of an OH* scavenger under nitrogen purging as compared to air-saturated conditions indicates that O(3P) is an important reactive species with 4-CP in this system. When 4-CP is added to the system, IO3- production is enhanced. On the basis of the elimination of potential reaction pathways, O(3P) and IO3* are suspected reactive species with 4-CP in this system.     

Indirect photodegradation of dissolved free amino acids: the contribution of singlet oxygen and the differential reactivity of DOM from various sources

The role of photochemically generated singlet oxygen (1O2) in the DOM-sensitized degradation of eighteen dissolved free amino acids was investigated. The fraction of total sensitized degradation due to reaction with 1O2 was determined through a kinetic analysis based on a measured reaction rate constant for each amino acid coupled with measured 1O2 concentrations and was confirmed through quenching experiments. Only four of the eighteen free amino acid residues examined were found to be photolabile under environmentally relevant conditions: histidine, methionine, tyrosine, and tryptophan. The fraction of Suwannee River Humic Acid (SRHA)-sensitized degradation due to reaction with 1O2 ranged from an upper value of 110 +/- 10% for histidine to 8 +/- 1% for tryptophan, with 26 +/- 3% contribution for methionine and 33 +/- 4% for tyrosine. In addition to degradation through reaction with 1O2, other reactive intermediates involved in the SRHA-photosensitized degradation of these amino acids were identified. Methionine was thought to be additionally degraded through reaction with H2O2 and triplet excited-state DOM, and 67% of tyrosine's indirect photodegradation was assigned to an oxygen-dependent type I photooxidation reaction. The majority of tryptophan indirect degradation was due to reaction with 3DOM. Photodegradation experiments with various DOM sources including Pony Lake (Antarctica) fulvic acid and a synthetic estuarine sample, as well as Minnesota freshwater samples (lakes Itasca, Superior, Josephine, and the St Louis River), demonstrated distinct reactivity patterns, indicating that DOM's 1O2-generation efficiency is not strongly coupled to its ability to promote other photooxidation pathways. These four amino acids highlightthe differential photoreactivity of DOM from various sources.     

FTIR kinetic, product, and modeling study of the OH-initiated oxidation of 1-butanol in air

A kinetic and product study was performed on the reaction of OH radicals with 1-butanol in a 480 L indoor photoreactor and also in the EUPHORE outdoor smog chamber in Valencia, Spain. Long path in situ FTIR spectroscopy and gas chromatography with photoionization detection were used to analyze reactants and products. Using a kinetic relative rate technique, a rate coefficient of k(OH + 1-butanol) = (8.28 +/- 0.85) x 10(-12) cm3 s(-1) was measured in 740 Torr synthetic air at 298 +/- 2 K. The reaction products observed and their fractional molar yields were (in percent) butanal (51.8 +/- 7.1), propanal (23.4 +/- 3.5), ethanal (12.7 +/- 2.2), and formaldehyde (43.4 +/- 2.4). In addition, the results support the probable formation of 4-hydroxy-2-butanone. Propanal, ethanal, and formaldehyde could also be formed in secondary reactions of some of the primary aldehydic products. However, under the conditions employed in the experiments, the contribution from secondary reactions is very minor. On the basis of the product studies, a detailed atmospheric degradation mechanism was constructed and tested against experimental data by chemical box model calculations. Measured and simulated concentration-time profiles for selected reactants were in excellent agreement.     

Monitoring OH-initiated oxidation kinetics of isoprene and its products using online mass spectrometry

A novel technique has been developed to simultaneously monitor the kinetics of the OH radical-initiated oxidation of isoprene and formation and oxidation of its products (methyl vinyl ketone, methacrolein, 3-methylfuran, and formaldehyde) using online mass spectrometry. The kinetics of isoprene and its products were investigated at 323 K and at 1 atm total pressure. The responses of 30 representative ions for isoprene and its products were monitored during the reaction, and their concentration profiles were calculated by linear algebraic equations, which resolve the measured mass spectra of representative ions into the responses of individual target organics, and by calibrations, which converted the responses to individual target concentrations. Using this method, yields of methyl vinyl ketone, methacrolein, and 3-methylfuran at 323 K were measured to be 14.4+/-0.1%, 19.0+/-0.2%, and 2.9+/-0.2%, respectively, in excellent agreement with previously reported yields under NOx-free conditions. The reaction kinetics of isoprene and its oxidation products measured by the experimental procedure developed in this study were compared with those estimated by a kinetic model of isoprene oxidation. The observed methacrolein concentrations as a function of time were reproduced reasonably well by this model, while the observed methyl vinyl ketone concentration could be reproduced by including secondary reactions of some of the hydroperoxide products of isoprene oxidation. The observed 3-methylfuran concentrations could be reproduced using secondary cyclization reactions of some of the 1,4-hydroxycarbonyl products of isoprene oxidation. These results suggest that under low NOx conditions reactions of some of the hydroperoxides and hydroxycarbonyls produced from the OH-initiated oxidation of isoprene may be a significant source of methyl vinyl ketone and 3-methylfuran in the atmosphere.     

光活化过硫酸钾体系下直接蓝15降解动力学及其降解机制

为探索双偶氮染料直接蓝15(DB15)在水中的降解可行性及在活性氧物种作用下可能的反应位点和迁移转化机制,利用紫外光活化过硫酸钾(UV/K₂S₂O₈)技术研究了DB15在活性氧物种作用下的降解动力学和反应机制。结果表明,双偶氮染料DB15在UV/K₂S₂O₈体系中降解符合假一级动力学,其动力学常数速率为0.010 7 min^-1, K₂S₂O₈质量浓度、底物初始浓度和反应温度对其降解动力学影响显著。利用气相色谱-质谱法对DB15在UV/K₂S₂O₈体系下降解中间产物进行初步的分离与分析,并结合DB15前线电子云密度(FEDs)的理论计算结果对其降解途径进行推导。研究发现:DB15在硫酸根自由基($SO_4^-为探索双偶氮染料直接蓝15(DB15)在水中的降解可行性及在活性氧物种作用下可能的反应位点和迁移转化机制,利用紫外光活化过硫酸钾(UV/K_2S_2O_8)技术研究了DB15在活性氧物种作用下的降解动力学和反应机制。结果表明,双偶氮染料DB15在UV/K_2S_2O_8体系中降解符合假一级动力学,其动力学常数速率为0.010 7 min~(-1),K_2S_2O_8质量浓度、底物初始浓度和反应温度对其降解动力学影响显著。利用气相色谱-质谱法对DB15在UV/K_2S_2O_8体系下降解中间产物进行初步的分离与分析,并结合DB15前线电子云密度(FEDs)的理论计算结果对其降解途径进行推导。研究发现:DB15在硫酸根自由基(SO_4~-·)、羟基自由基(·OH)等活性氧物种作用下N_(11)、N_(24)、N_(41)、N_(42)和C_(28)等活性位点易被自由基直接攻击或者发生电子转移反应,从而引起DB15分子中NN和C—N键断裂,然后中间产物再进一步羟基化是其主要的降解途径。     

Efficient degradation of TCE in groundwater using Pd and electro-generated H2 and O2: a shift in pathway from hydrodechlorination to oxidation in the presence of ferrous ions

Degradation of trichloroethylene (TCE) in simulated groundwater by Pd and electro-generated H(2) and O(2) is investigated in the absence and presence of Fe(II). In the absence of Fe(II), hydrodechlorination dominates TCE degradation, with accumulation of H(2)O(2) up to 17 mg/L. Under weak acidity, low concentrations of oxidizing ?OH radicals are detected due to decomposition of H(2)O(2), slightly contributing to TCE degradation via oxidation. In the presence of Fe(II), the degradation efficiency of TCE at 396 μM improves to 94.9% within 80 min. The product distribution proves that the degradation pathway shifts from 79% hydrodechlorination in the absence of Fe(II) to 84% ?OH oxidation in the presence of Fe(II). TCE degradation follows zeroth-order kinetics with rate constants increasing from 2.0 to 4.6 μM/min with increasing initial Fe(II) concentration from 0 to 27.3 mg/L at pH 4. A good correlation between TCE degradation rate constants and ?OH generation rate constants confirms that ?OH is the predominant reactive species for TCE oxidation. Presence of 10 mM Na(2)SO(4), NaCl, NaNO(3), NaHCO(3), K(2)SO(4), CaSO(4), and MgSO(4) does not significantly influence degradation, but sulfite and sulfide greatly enhance and slightly suppress degradation, respectively. A novel Pd-based electrochemical process is proposed for groundwater remediation.     

Quantitative correlation of absolute hydroxyl radical rate constants with non-isolated effluent organic matter bulk properties in water

Absolute second-order rate constants for the reaction between the hydroxyl radical (*OH) and eight water samples containing non-isolated effluent organic matter (EfOM) collected at different wastewater and reclamation sites were measured by electron pulse radiolysis. The measured rate constants ranged from 0.27 to 1.21 x 10(9) Mc(-1) s(-1), with an average value of 0.86 (+/-0.35) x 10(9) Mc(-1) s(-1). These absolute values were 3-5 times faster than previously reported values using natural organic matter and wastewater isolates. The obtained rate constants were correlated (R2 > 0.99) to bulk EfOM properties through an empirical equation that included terms relating to the polarity, apparent molecular weight, and fluorescence index of the effluent organic matter. The obtained data were used to model steady state *OH concentrations during UV advanced oxidation. The steady-state *OH concentration was lower than that obtained using previously reported values for the reaction with dissolved organic matter, indicating that accurate measurement of reaction rate constants at specific sites would greatly improve the design and prediction of the removal of organic contaminants. These results will improve the ability of researchers to accurately model scavenging capacities during the advanced oxidation processtreatment of wastewaters.     

Kinetic model for Fe(II) oxidation in seawater in the absence and presence of natural organic matter

A detailed kinetic model has been developed to describe the oxidation of Fe(II) in seawater in both the absence and the presence of natural organic material. Experimental data were collected using a luminol chemiluminescence-based method to measure Fe(II), assuming that both the inorganic and the organically complexed species were detected. In the absence of organic matter, the data were modeled based on the Haber-Weiss mechanism with the inclusion of a back-reaction of Fe(III) with superoxide and precipitation of Fe(OH)3. Both reactions were found to be significant using sensitivity analysis. When organic matter is present, the model was extended by organic complexation of Fe(II) and Fe(III) with the creation of a parallel oxidation pathway for Fe(II). Fe(II) oxidation at natural (nanomolar) concentrations was accurately predicted for a range of organic concentrations. The model also accounted for scavenging of superoxide by sub-nanomolar levels of dissolved copper and by organic matter when present. The presence of a relatively strong Fe(III) binding ligand was observed to significantly increase the rate of Fe(II) oxidation, while ultimately retaining most of the iron in the system in dissolved (organically complexed) form. The complexation reactions and reaction of inorganic and organically bound Fe(II) with oxygen were found to be critical reactions in the system, while Fe(III) hydrolysis became unimportant even at low organic concentrations. The superoxide radical was also observed to have a major role in the cycling of iron due to its ability to act as both an oxidant and a reductant. The model indicates that the rate constant for the reaction of Fe(II) with O2 has generally been underestimated in previous work and that the secondary oxidation of Fe(II) by H2O2 and subsequently OH* plays a relatively minor role in these systems.     

花生粕酶水解液中黄曲霉毒素脱毒定性研究

本文研究了一种新工艺，将花生粕深度酶水解后，使微溶于水的黄曲毒素（AFT）从结合的疏水性氨基酸残基上充分游离，采用过滤法，截2留住大部分黄典霉毒素，从而使AFT含量显著下降。     

Radical dependence of the yields of methacrolein and methyl vinyl ketone from the OH-initiated oxidation of isoprene under NO(x)-free conditions

Formation yields of methacrolein (MAC), methyl vinyl ketone (MVK), and 3-methyl furan (3MF) from the hydroxyl radical (OH) initiated oxidation of isoprene were investigated under NO(x)-free conditions (NO(x) = NO + NO(2)) at 50 °C and 1 atm in a quartz reaction chamber coupled to a mass spectrometer. Yields of the primary products were measured at various OH and hydroperoxy (HO(2)) radical concentrations and were found to decrease as the HO(2)-to-isoprene-based peroxy radical (ISORO(2)) concentration ratio increases. This is likely the result of a competition between ISORO(2) self- and cross-reactions that lead to the formation of the primary products, with reactions between these peroxy radicals and HO(2) which can lead to the formation of peroxides. Under conditions with HO(2)/ISORO(2) ratios close to 0.1, yields of MVK (15.5% ± 1.4%) and MAC (13.0% ± 1.2%) were higher than the yields of MVK (8.9% ± 0.9%) and MAC (10.9% ± 1.1%) measured under conditions with HO(2)/ISORO(2) ratios close to 1. This radical dependence of the yields was reproduced reasonably well by an explicit model of isoprene oxidation, suggesting that the model is able to reproduce the observed products yields under a realistic range of atmospheric HO(2)/ISORO(2) ratios.     

High-resolution atmospheric modeling of fluorotelomer alcohols and perfluorocarboxylic acids in the North American troposphere

A high spatial and temporal resolution atmospheric model is used to evaluate the potential contribution of fluorotelomer alcohol (FTOH) and perfluorocarboxylate (PFCA) emissions associated with the manufacture, use, and disposal of DuPont fluorotelomer-based products in North America to air concentrations of FTOH, perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA) in North America and the Canadian Arctic. A bottom-up emission inventory for PFCAs and FTOHs was developed from sales and product composition data. A detailed FTOH atmospheric degradation mechanism was developed to simulate FTOH degradation to PFCAs and model atmospheric transport of PFCAs and FTOHs. Modeled PFCA yields from FTOH degradation agree with experimental smog-chamber results supporting the degradation mechanism used. Estimated PFCA and FTOH air concentrations and PFCA deposition fluxes are compared to monitoring data and previous global modeling. Predicted FTOH air concentrations are generally in agreement with available monitoring data. Overall emissions from the global fluorotelomer industry are estimated to contribute approximately 1-2% of the PFCAs in North American rainfall, consistent with previous global emissions estimates. Emission calculations and modeling results indicate that atmospheric inputs of PFCAs in North America from fluorotelomer-based products will decline by an order of magnitude in the near future as a result of current industry commitments to reduce manufacturing emissions and lower the residual fluorotelomer alcohol raw material and trace PFCA product content.