The use of Natural Gas for Vehicles (NGV) is increasing due to estimated positive impacts on exhaust emissions and carbon footprint. However, significant emissions of unregulated particles in the ultrafine range have been reported in the literature. Significant variations have also been observed, but data is still lacking to thoroughly describe NGV emissions. This is particularly true for some vehicle categories such as light commercial vehicles. A clear need therefore exists to additionally document the NGV emissions, especially unregulated compounds with health or environmental effects such as ultrafine particles and Volatile and Intermediate-Volatility Organic Compounds (VOCs/IVOCs). This study presents the emissions of methane, regulated gases, total particles from 5.6 nm with size distribution, and VOCs/IVOCs. It focuses on NGV, diesel and gasoline passenger cars and light commercial vehicles with comparable technical characteristics. Results show that during regeneration phases, ultrafine particle emissions from gasoline vehicles with particle filters increase by factors 40 to 800. They also show high emissions of ultrafine particles from NGV, with significant shares of sub-23 and sub-10 nm particles (more than 2/3 of the emissions). The organics emitted by the NGV are less volatile than those from diesel or gasoline. Coupled with the significant sub-10 and sub-23 nm particles from NGV, this suggests that the particles could be partly semi-volatile. The NGV particle emissions might thus be underestimated with current normative protocols. In addition to measuring particles from 10 nm in the upcoming Euro 7 norm, this study indicates that quantifying semi-volatile particles could help better describe vehicular emissions, especially for NGV vehicles.

The intensification of pharmaceutical use globally has led to an increase in the number of water bodies contaminated by drugs, and an effective strategy must be developed to address this issue. In this work, several biochars produced from Miscanthus straw pellets (MSP550, MSP700) and wheat straw pellets (WSP550, WSP700) at 550 and 700°C, respectively, were selected as adsorbents for removing various pharmaceuticals, such as pemetrexed (PEME), sulfaclozine (SCL), and terbutaline (TBL), from the aqueous phase. The biochar characterizations (physicochemical properties, textural properties, morphological structures, and zeta potentials) and adsorptive conditions (contact times, temperatures, and pH effect) were investigated. The infrared and Raman spectra of biochars before and after pharmaceutical adsorption, as well as quantum chemical computations, were carried out to explore the adsorption mechanisms. The results showed that the general adsorption abilities of biochars for pharmaceuticals were in the order of WSP700 > MSP700 > MSP550 > WSP550. Both the higher drug concentration and higher temperature improved biochar adsorption. By decreasing the pH, the adsorption amounts increased for PEME and SCL. However, TBL exhibited the best adsorption at pH 7, whereas a weakening of affinity occurred at lower or higher pH values. Electrostatic interactions and hydrogen bonding were the main adsorptive mechanisms between all biochars and pharmaceuticals. π-π interactions played a role in the adsorption process of low-temperature-prepared biochars (MSP550 and WSP550). This work can provide new insights into the control of pharmaceuticals from water with low-cost adsorbents. PRACTITIONER POINTS: Use of biochars for pharmaceuticals removal from aqueous phase. Characterization of biochars : physical and chemical properties, textural and surface properties. Simulation calculation for characterization of pharmaceuticals. Kinetic studies of pharmaceuticals adsorption on biochars. DRIFTS and Raman analysis for the understanding of adsorption process.

Abstract In Earth’s atmosphere the efficiency of sub-micron aerosol particles to produce cloud droplets is expected to be affected by their surface tension. But this quantity cannot be measured directly and is inferred from the chemical compounds present in aerosols. Amphiphilic surfactants are present in aerosols but direct experimental information on the impacts of other aerosol components on their surface properties is lacking. This work explores systematically how NaCl, (NH4)2SO4, oxalic, and glutaric acid modify the surface properties of amphiphilic surfactants, SDS, Brij35, TritonX100, TritonX114, and CTAC, by determining the adsorption isotherms for these mixtures. The results reveal that all these water-soluble aerosol components enhance the efficiency of surfactants. The inorganic salts substantially lowered the surface tension (- Δσ > 10 mN m-1) and CMC of the surfactants by salting out while the surface tension of mixtures with organic acids deviated strongly from ideality (- Δσ = 10 - 30 mN m-1) and displayed some synergism. These results suggest that molecular interactions take place at the surface, even with non-ionic surfactants, that need to be further studied and included in models.

In situ and operando diffuse reflectance FT-IR (DRIFTS) studies are often carried out over samples that may undergo changes in optical properties due to stronger absorptivity (darkening), for instance when coking or being reduced. The variation of IR optical pathlength of two Fe and Co-based Fischer-Tropsch catalysts treated at different temperatures was investigated through the use of an internal standard CaCO3 that was physically mixed with the catalyst. The CaCO3 overtone band at 1795 cm-1 was used, exhibiting an integral molar absorption coefficient & epsilon; = 2.68 x 105 cm mol-1. The IR penetration depth was negligible over the iron oxide sample once reduced above 400 degrees C, due to the formation of a strongly absorbing material. A reduction of the cobalt sample up to 350 degrees C revealed large changes of optical pathlength (dropping four-fold from 66 to 16 & mu;m), likely related to the onset of cobalt oxide deep reduction. These data indicate that changes in optical pathlength should be considered when attempting quantitative DRIFTS analyses and that mixing a small concentration of CaCO3, e.g. 2 wt%, is a suitable way of doing so.

The study aims to assess the efficiency of applying the Fenton process to municipal wastewater from Fez city (Morocco), previously pretreated by the aerobic process. Experiments were carried out on a lab scale with batch reactors. The aerobic pretreatment was operated in a suspended growth bio-reactor and monitored periodically for several parameters. The process performance was evaluated based on chemical oxygen demand (COD), biochemical oxygen demand (BOD5), and UV-Visible absorption spectra. The aerobic bioreactor showed a high efficiency, with removals up to 67% and 100% for COD and BOD5, respectively. The Fenton process applied after aeration pretreatment suc-cessfully reduced the residual bio-resistant organics, and its efficiency was evaluated in terms of COD. Therefore, the integrated treatment of aeration and Fenton technologies, at optimal operat-ing conditions of the Fenton process (pH = 3, contact time = 60 min, FeSO4 dose = 3.57 mmol/L, and H2O2 dose = 14.71 mmol/L) achieved total COD, color and BOD5 removals of 86%, 90.3%, and 100%, respectively. Accordingly, UV-visible absorption spectra underwent a significant decrease due to the removal of organic substances. Indeed, the final measured COD was 117.3 mg/L, which complies with national and international standards for liquid disposal or reuse. Therefore, the proposed treatment train could be promising for raw wastewater remediation and environmental protection.

In Earth's atmosphere, the surface tension of sub-micron aerosol particles is suspected to affect their efficiency in becoming cloud droplets. But this quantity cannot be measured directly and is inferred from the chemical compounds present in aerosols. Amphiphilic surfactants have been evidenced in aerosols but experimental information on the surface properties of their mixtures with other aerosol components is lacking. This work explores experimentally the surface properties of aqueous mixtures of amphiphilic surfactants (SDS, Brij35, TritonX100, TritonX114, and CTAC) with inorganic salts (NaCl, (NH4)2SO4) and soluble organic acids (oxalic and glutaric acid) using pendant droplet tensiometry. Contrary to what could be expected, inorganic salts and organic acids systematically enhanced the efficiency of the surfactants rather than reduced it, by further lowering the surface tension and, in some cases, the CMC. Furthermore, all the mixtures studied were strongly non-ideal, some even displaying some synergism, thus demonstrating that the common assumption of ideality for aerosol mixtures is not valid. The molecular interactions between the mixture components were either in the bulk (salting out), in the mixed surface monolayer (synergy on the surface tension) or in the micelles (synergy on the CMC) and need to be included when describing such aerosol mixtures.

The characterization of vehicle exhaust emissions of volatile organic compounds (VOCs) is essential to estimate their impact on the formation of secondary organic aerosol (SOA) and, more generally, air quality. This paper revises and updates non-methane volatile organic compounds (NMVOCs) tailpipe emissions of three Euro 5 vehicles during Artemis cold urban (CU) and motorway (MW) cycles. Positive matrix factorization (PMF) analysis is carried out for the first time on proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) datasets of vehicular emission. Statistical analysis helped to associate the emitted VOCs to specific driving conditions, such as the start of the vehicles, the activation of the catalysts, or to specific engine combustion regimes. Merged PTR-ToF-MS and automated thermal desorption gas chromatography mass spectrometer (ATD-GC-MS) datasets provided an exhaustive description of the NMVOC emission factors (EFs) of the vehicles, thus helping to identify and quantify up to 147 individual compounds. In general, emissions during the CU cycle exceed those during the MW cycle. The gasoline direct injection (GDI) vehicle exhibits the highest EF during both CU and MW cycles (252 and 15 mg/km), followed by the port-fuel injection (PFI) vehicle (24 and 0.4 mg/km), and finally the diesel vehicle (15 and 3 mg/km). For all vehicles, emissions are dominated by unburnt fuel and incomplete combustion products. Diesel emissions are mostly represented by oxygenated compounds (65%) and aliphatic hydrocarbons (23%) up to C-22, while GDI and PFI exhaust emissions are composed of monoaromatics (68%) and alkanes (15%). Intermediate volatility organic compounds (IVOCs) range from 2.7 to 13% of the emissions, comprising essentially linear alkanes for the diesel vehicle, while naphthalene accounts up to 42% of the IVOC fraction for the gasoline vehicles. This work demonstrates that PMF analysis of PTR-ToF-MS datasets and GC-MS analysis of vehicular emissions provide a revised and deep characterization of vehicular emissions to enrich current emission inventories.

Three activated carbons (ACs) obtained from wood and activated either by steam (AC1) or phosphoric acid (AC2, AC3) were characterized via nitrogen adsorption-desorption isotherms, zeta potentials, infrared and Raman spectroscopy, as well as their chemical analysis was determined. Adsorption experiments with Pemetrexed (PEME), a pharmaceutical used for the treatment of tumors, were carried out in which adsorbent doses, contact times, temperatures, and solution pH were investigated. Correlation between the physicochemical properties of ACs and the adsorption capacity was proposed. According to the results, it was found that AC1 and AC3 were better described by the Freundlich and Langmuir models, respectively, whereas both models could be used to fit the adsorptive isotherm of AC2. The higher the initial PEME concentration or the temperature, the higher the adsorption capacity was. The adsorption capacities of the adsorbents were in the following order, AC3 > AC2 > AC1, in agreement with their specific surface areas. A coexistence process of physical and chemical adsorption existed in all ACs as predicted by the best fitting obtained with the Dubinin-Radushkevich, pseudo-second-order kinetic and Elovich models. The adsorption mechanisms were researched using the Conductor-like Screening Model methodology to determine the proton donor and acceptor centres in PEME. As main conclusion, supported by DRIFTS analysis and O/C ratios, AC3 and AC2 containing more oxygenated groups, must adsorb PEME onto their surface according to a monolayer adsorption mechanism. Fitting procedure demonstrated that the equilibrium data obtained with these two materials can be fitted to the Langmuir isotherm.

Atmospheric particles have several impacts on health and the environment, especially in urban areas. Parts of those particles are not fresh and have undergone atmospheric chemical and physical processes. Due to a lack of representativeness of experimental conditions and experimental artifacts such as particle wall losses in chambers, there are uncertainties on the effects of physical processes (condensation, nucleation and coagulation) and their role in particle evolution from modern vehicles. This study develops a new method to correct wall losses, accounting for size dependence and experiment-to-experiment variations. It is applied to the evolution of fresh diesel exhaust particles to characterize the physical processes which they undergo. The correction method is based on the black carbon decay and a size-dependent coefficient to correct particle distributions. Six diesel passenger cars, Euro 3 to Euro 6, were driven on a chassis dynamometer with Artemis Urban cold start and Artemis Motorway cycles. Exhaust was injected in an 8 m3 chamber with Teflon walls. The physical evolution of particles was characterized during 6 to 10 h. Increase in particle mass is observed even without photochemical reactions due to the presence of intermediate-volatility organic compounds and semi-volatile organic compounds. These compounds were quantified at emission and induce a particle mass increase up to 17 % h−1, mainly for the older vehicles (Euro 3 and Euro 4). Condensation is 4 times faster when the available particle surface is multiplied by 6.5. If initial particle number concentration is below [8–9] × 104 cm−3, a nucleation mode seems to be present but not measured by a scanning mobility particle sizer (SMPS). The growth of nucleation-mode particles results in an increase in measured [PN]. Above this threshold, particle number concentration decreases due to coagulation, up to −27 % h−1. Under those conditions, the chamber and experimental setup are well suited to characterizing and quantifying the process of coagulation.

Two commercial activated carbons, namely STIX and AP4, were selected to investigate their ability for siloxane adsorption and further thermal regeneration in relation with their different physico-chemical properties. In the frame of biogas purification, the studied siloxanes were L2, L3, L4 (linear molecules) and D4, D5 (cyclic molecules). The maximum capacity of adsorption was estimated by gas chromatography and gravimetric methods. AP4 presents better adsorptive properties comparing with STIX irrespective of the type of siloxane. Thermal regeneration after siloxanes adsorption was followed up to 400 degrees C by both gas chromatography and in situ DRIFTS. Except L2, the siloxane polymerization proceeds on the AC containing alkali metals (K, Na) as revealed by the observed release of their decomposition products during the thermodesorption treatment. The same sites are responsible for the cleavage of SieO bonds in linear molecules and formation of L2 as primary product above 100 degrees C. The presence of such sites, possibly strong basic sites, is detrimental to the regenerability of the spent adsorbent and to the adsorption which could be limited by partial blockage of the AC porosity. Interestingly the regenerability of the alkali-free AC depends only on the volatility of the siloxane.

Predicting the activation of submicrometer particles into cloud droplets in the atmosphere remains a challenge. The importance of surface tension, sigma (mN m(-1)), in these processes has been evidenced by several works, but information on the "surfactants" lowering sigma in actual atmospheric particles remains scarce. In this work, PM1 aerosols from urban, coastal, and remote regions of Europe (Lyon, France, Rogoznica, Croatia, and Pallas, Finland, respectively) were investigated and found to contain amphiphilic surfactants in concentrations up to 2.8 mu g m(-3) in the air and 1.3 M in the particle dry volume. In Pallas, correlations with the PM1 chemical composition showed that amphiphilic surfactants were present in the entire range of particle sizes, supporting recent works. This implied that they were present in hundreds to thousands of particles cm(-3) and not only in a few large particles, as it has been hypothesized. Their adsorption isotherms and critical micelle concentration (CMC) were also determined. The low CMC obtained (3 x 10(-5)-9 x 10(-3) M) implies that surface tension depression should be significant for all the particles containing these compounds, even at activation (growth factor similar to 10). Amphiphilic surfactants are thus likely to enhance the CCN ability of submicrometer atmospheric particles.

The photodegradation reactions of two typical β2-adrenoceptor agonists, salbutamol (SAL) and terbutaline (TBL), alone, and in the presence of Aldrich humic acid (AHA) or Suwannee River fulvic acid (SRFA) were investigated by steady-state photolysis experiments, laser flash photolysis (LFP), kinetic modeling and quantum calculation. AHA and SRFA (2–20 mgC L−1) accelerated the phototransformation of both SAL and TBL. For SAL, an inhibiting effect of oxygen on the photodegradation was observed that is fully consistent with the main involvement of excited triplet states of HS (3HS*). On the contrary, oxygen drastically enhanced the photodegradation of TBL showing that 3HS* were negligibly involved in the reaction. The involvement of singlet oxygen was also ruled out because of the low reaction rate constant measured between TBL and singlet oxygen. Quantum calculations were therefore performed to explore whether oxygenated radicals could through addition reactions explain the differences of reactivity of TBL and SAL in oxygen medium. Interestingly, calculations showed that in the presence of oxygen, the addition of phenoxyl on TBL led to the formation of adducts and to the loss of TBL while the same addition reaction on SAL partly regenerated the starting compound and at the end degraded SAL less efficiently. This study is of high relevance to understand the processes involved in SAL and TBL phototransformation and the photoreactivity of HS. Moreover, our findings suggest that TBL might be a promising probe molecule to delineate the role of oxygenated radicals.

A commercial activated carbon (AC) was characterized by physicochemical methods. The AC adsorption/desorption properties and the adsorbent regenerability were evaluated for the removal of octamethylcyclotetrasiloxane (D4), a common siloxane impurity in biogases. In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) was employed to investigate the adsorption of D4 on AC at room temperature and its thermodesorption up to 300 degrees C. The AC was activated in N-2 at varying temperatures within the 25-300 degrees C interval. The striking feature is the polymerization of D4 observed during the desorption experiment followed by the release of PolyDimethylSiloxane (PDMS) in the gas phase. The thermal treatment before adsorption is proposed to influence the D4-AC interaction. (c) 2017 Elsevier B.V. All rights reserved.

Bicarbonate, phosphate, chloride ions, and humic substances are among the constituents most widely present in natural waters. These non-target constituents can greatly affect the efficiency of advanced oxidation processes used for water decontamination due to their capacity to interfere with the adsorption of the target compounds on the surface of TiO2, absorb photons, scavenge hydroxyl radicals (·OH), and generate photochemical reactive intermediates. In this work, the effect of these constituents on the degradation of sulfaclozine (SCL) was monitored in three different AOPs systems: UV/TiO2, UV/K2S2O8, and UV/TiO2/K2S2O8. It was shown that bicarbonate (HCO3 −) and phosphate (HPO4 2−) ions enhanced the degradation of SCL in UV/TiO2 and UV/TiO2/K2S2O8 systems whereas the addition of humic substances influenced these rates with a much smaller extent. On the other hand, the degradation rate of SCL in the UV/K2S2O8 system was not affected by the presence of HCO3 − and HPO4 2− but was inhibited in the presence of humic substances. In addition, the different mechanisms that can take place in the presence of these constituents were discussed and the degradation rate enhancement in presence of HCO3 − and HPO4 2− was attributed to the formation of new reactive species such as carbonate (CO3 ·–) and hydroxyl (·OH) radicals activated by TiO2 holes (h+). In the presence of chloride (Cl−) and nitrate (NO3 −) ions, an enhancement of SCL adsorption on the surface of TiO2 was observed. Finally, a comparative study of the degradation of SCL in river water and ultrapure water was reported.

Biogas produced from sludge in waste water treatment plant, as well as from landfills, can be collected and utilized as a clean energy source. However, a special issue regarding biogas concerns the presence of traces siloxanes, semi-volatile methylated organosilicon (VMS) compounds containing Si–O bonds originating from hygiene, health care and industrial products [1]. During the biogas combustion, siloxanes are converted into crystalline silica inducing the engine damage. The present work aims to investigate the adsorption and thermodesorption of decamethyltetrasiloxane (L4) over two commercial activated carbon (AC) samples (STIX and AP4-50 from ChemEnvirocarb) using the Diffuse Reflection Infrared Spectroscopy (DRIFTS). The physicochemical properties of ACs were characterized using various techniques like N2 adsorption at 77K, XRD, SEM and TGA. The adsorption experiments were performed by contacting a stream of L4 (40 ppm) in nitrogen with a mixture of AC/KBr at room temperature. The spectra recorded during this step are dominated by the response of the gas phase. Therefore, the adsorbed phase can be hardly observed. Upon saturation, the cell was purged under N2 flow during 16h to eliminate L4 in the gas phase. The exhausted ACs underwent thermal programmed desorption from 25°C to 300°C (for STIX) or 400°C (for AP4-50). At 25°C, the spectra of ACs exhibit very weak bands of L4 in adsorbed phase. Upon heating, STIX sample shows mainly the decomposition of L4 into L2 between 80 and 200°C accompanied by a small desorption of L4. Further heating leads to the polymerization of L4 into PolyDimethylSiloxane (PDMS) [2]. This compound is weakly volatile and cannot be completely removed at 300°C. For AP4-50, the release of L4 into the gas phase can be observed throughout the heating process (mainly between 175 and 350°C). Small formation of L2 is noticed when heating up to 145°C. No evidence of the polymerization can be found for this sample. The transformation of L4 during the thermodesorption can be related to its reaction with the surface functional groups of ACs. The determination of these groups which are responsible for the formation of PDMS seems to be important for improving the regenerability properties and the reuse of ACs. References [1]. R. Dewil, L. Appels, J. Baeyens, Energy. Convers. Manag. 47 (2006) 1711–1722. [2]. V.T.L. Tran, P. Gelin, C. Ferronato, L. Fine, J.M. Chovelon, G. Postole, Catal. Today. (2017) http://dx.doi.org/10.1016/j.cattod.2017.01.006

The evaluation of different persulfate activation methods (UV, solar light, electron, Fe(II)) on the degradation of sulfaclozine was investigated along with the effect of persulfate concentrations. UV/TiO2/K2S2O8 resulted in the highest degradation rate regardless persulfate concentrations. However, persulfate addition on the UV/TiO2 system was not as efficient as expected and the use of radical scavengers showed that pH played an important role in the distribution of dominant radicals. It was found that at pH 7, hydroxyl and sulfate radicals were involved in the degradation of sulfaclozine, whereas at pH 11 no contribution of sulfate radicals was observed.Following the formation of the six by-products of the first generation formed in UV/TiO2 system, we obtained the formation of two by-products out of six in the UV/K2S2O8 system and four in the UV/TiO2/K2S2O8 system but with different concentrations, confirming the hypothesis suggested about the intervention of O-2(center dot-) in the degradation mechanism of sulfaclozine.The second order rate constant of the reaction between sulfaclozine and SO4 center dot- radicals was determined by a competitive kinetics method and two values of 7.5 x 10(9) M-1 s(-1) and 1.7 x 10(10) M-1 s(-1) were obtained depending on the references used, and found to be close to those obtained between sulfaclozine and (OH)-O-center dot radicals (7.2 x 10(9) M-1 s(-1) and 5.9 x 10(9) M-1 s(-1)). (C) 2016 Elsevier B.V. All rights reserved.

The photocatalytic degradation of sulfaclozine on TiO2 suspensions under UV light was investigated and a complete degradation of 88 mu M of sulfaclozine was obtained after 60 min. The addition of isopropanol (500 mM), methanol (500 mM), and ICI (10 mM) to the system inhibited the degradation of sulfaclozine c.a 60%, 85% and 95% respectively, which allowed us to conclude that (OH)-O-center dot radicals, valence-band holes and electrons could intervene in the degradation of sulfaclozine.The second order rate constant of the reaction between sulfaclozine and (OH)-O-center dot radicals was determined by a competitive kinetics method and a value of (7.2 x 10(9) M-1 s(-1)) was obtained.HPLC/DAD and LC-MS/MS analysis were used to identify and follow the appearance and disappearance of sulfaclozine as well as its intermediates. Twelve main intermediates were identified from the photocatalytic degradation of sulfaclozine on TiO2 suspensions. The comparison of the evolution of those intermediates with and without the addition of methanol showed that the quantity of eight intermediates decreased in the presence of methanol, one intermediate was observed to show an increase, while three others maintained the same amount. These results helped us to propose a tentative mechanism of degradation including (OH)-O-center dot radicals, holes, superoxide radicals and electrons attack. In addition, TOC monitoring and mineralization during the photocatalytic degradation of sulfaclozine showed the release of almost all chlorides and the existence of the nitrogen atoms in molecular form even after 180 min of irradiation. (C) 2015 Elsevier B.V. All rights reserved.

Recent analyses of atmospheric aerosols from different regions have demonstrated the ubiquitous presence of strong surfactants and evidenced surface tension values, σ, below 40 mN m(-1), suspected to enhance the cloud-forming potential of these aerosols. In this work, this approach was further improved and combined with absolute concentration measurements of aerosol surfactants by colorimetric titration. This analysis was applied to PM2.5 aerosols collected at the Baltic station of Askö, Sweden, from July to October 2010. Strong surfactants were found in all the sampled aerosols, with σ = (32-40) ± 1 mN m(-1) and concentrations of at least 27 ± 6 mM or 104 ± 21 pmol m(-3). The absolute surface tension curves and critical micelle concentrations (CMC) determined for these aerosol surfactants show that (1) surfactants are concentrated enough in atmospheric particles to strongly depress the surface tension until activation, and (2) the surface tension does not follow the Szyszkowski equation during activation but is nearly constant and minimal, which provides new insights on cloud droplet activation. In addition, both the CMCs determined and the correlation (R(2) ∼ 0.7) between aerosol surfactant concentrations and chlorophyll-a seawater concentrations suggest a marine and biological origin for these compounds.

Isoprene is an important reactive gas that is produced mainly in terrestrial ecosystems but is also produced in marine ecosystems. In the marine environment, isoprene is produced in the seawater by various biological processes. Here, we show that photosensitized reactions involving the sea-surface microlayer lead to the production of significant amounts of isoprene. It is suggested that H-abstraction processes are initiated by photochemically excited dissolved organic matter which will the degrade fatty acids acting as surfactants. This chemical interfacial processing may represent a significant abiotic source of isoprene in the marine boundary layer.