Quantifying the influence of humic acid adsorption on colloidal microsphere deposition onto iron-oxide-coated sand

This article describes an approach for quantifying microsphere deposition onto iron-oxide-coated sand under the influence of adsorbed Suwannee River Humic Acid (SRHA). The experimental technique involved a triple pulse injection of model latex microspheres (microspheres) in pulses of (1) microspheres, followed by (2) SRHA, and then (3) microspheres, into a column filled with iron-coated quartz sand as a water-saturated porous medium. A random sequential adsorption model (RSA) simulated the gradual rise in the first (microsphere) breakthrough curve (BTC). Using the same model calibration parameters a dramatic increase in concentration at the start of the second particle BTC, generated after SRHA injection, could be simulated by matching microsphere concentrations to extrapolated RSA output. RSA results and microsphere/SRHA recoveries showed that 1 μg of SRHA could block 5.90 ± 0.14 × 10⁹ microsphere deposition sites. This figure was consistent between experiments injecting different SRHA masses, despite contrasting microsphere deposition/release regimes generating the second microsphere BTC.     

Aggregation and ecotoxicity of CeO₂ nanoparticles in synthetic and natural waters with variable pH, organic matter concentration and ionic strength

The influence of pH (6.0-9.0), natural organic matter (NOM) (0-10 mg C/L) and ionic strength (IS) (1.7-40 mM) on 14 nm CeO₂ NP aggregation and ecotoxicity towards the alga Pseudokirchneriella subcapitata was assessed following a central composite design. Mean NP aggregate sizes ranged between 200 and 10000 nm. Increasing pH and IS enhanced aggregation, while increasing NOM decreased mean aggregate sizes. The 48 h-E_rC20s ranged between 4.7 and 395.8 mg CeO₂/L. An equation for predicting the 48 h-E_rC20 (48 h-E_rC20 = −1626.4 × (pH) + 109.45 × (pH)² + 116.49 × ([NOM]) − 14.317 × (pH) × ([NOM]) + 6007.2) was developed. In a validation study with natural waters the predicted 48 h-E_rC20 was a factor 1.08-2.57 lower compared to the experimental values.     

Influence of Suwannee River humic acid on particle properties and toxicity of silver nanoparticles

Adsorption of natural organic matter (NOM) on nanoparticles can have dramatic impacts on particle dispersion resulting in altered fate and transport as well as bioavailability and toxicity. In this study, the adsorption of Suwannee River humic acid (SRHA) on silver nanoparticles (nano-Ag) was determined and showed a Langmuir adsorption at pH 7 with an adsorption maximum of 28.6 mg g⁻¹ nano-Ag. It was also revealed that addition of <10 mg L⁻¹ total organic carbon (TOC) increased the total Ag content suspended in the aquatic system, likely due to increased dispersion. Total silver content decreased with concentrations of NOM greater than 10 mg TOC L⁻¹ indicating an increase in nanoparticle agglomeration and settling above this concentration. However, SRHA did not have any significant effect on the equilibrium concentration of ionic Ag dissolved in solution. Exposure of Daphnia to nano-Ag particles (50 μg L⁻¹ and pH 7) produced a linear decrease in toxicity with increasing NOM. These results clearly indicate the importance of water chemistry on the fate and toxicity of nanoparticulates.     

Enhancement of phenanthrene adsorption on a clayey soil and clay minerals by coexisting lead or cadmium

Phenanthrene is commonly present together with heavy metals at many contaminated sites. This study investigated the influence of coexisting lead (Pb²⁺) or cadmium (Cd²⁺) on phenanthrene adsorption on soils. Batch experiments were conducted under different geochemical conditions including pH, mineral structure, organic matter content, and varying amounts of heavy metals. The results showed that the presence of heavy metals in solution at a fixed pH of 5.8 ± 0.1 enhanced phenanthrene adsorption, the extent of which was closely related to the concentrations and the electro-negativity of the metals. The enhancement on phenanthrene adsorption was positively correlated to the amount of adsorbed metals. Although Cd²⁺ is a softer Lewis acid, Pb²⁺ displayed a more significant effect as it was adsorbed to a greater extent on the soil surfaces. Thus, density of cation accumulation appears to be more influential than metal softness in enhancing phenanthrene adsorption. Moreover, with a portion of organic matter removed by heating at 550 °C, there was a stronger enhancement of phenanthrene adsorption by coexisting Pb²⁺, indicating an increasingly dominant mechanisms associated with Pb²⁺ at a lower organic matter content. Similar enhancement phenomenon was observed on bentonite and kaolinite, probably resulting from the cation-π bonding between the adsorbed soft metal cations and the aromatic ring of phenanthrene in solution. The desorption experiments further suggested that the bonding of phenanthrene adsorption was strengthened in the presence of Pb²⁺ and that a larger proportion of adsorbed phenanthrene remained on the soils (residual fraction) even after sequential methanol extractions. Further spectroscopic analyses and surface characterization are required to provide direct evidence of the formation and relative significance of cation-π bond for phenanthrene adsorption.     

Henry's Law coefficients of chloropicrin and methyl isothiocyanate

Henry's Law coefficients were measured for the first time for chloropicrin and methyl isothiocyanate (MITC) at 25 °C in deionized water, in 0.10 M NaCl, in 0.20 M NaCl, and in pH 4.0 and 8.0 buffered solutions. For chloropicrin, the Henry's Law coefficient was 2.1±0.3 atm M⁻¹, and did not show significant pH dependence or dependence on ionic strength. For MITC, the coefficient was much smaller, 0.06±0.05 atm M⁻¹. The Henry's Law coefficient for MITC did show dependence on ionic strength, increasing to 0.14±0.05 atm M⁻¹ at 0.20 M, but did not appear to depend on pH. MITC has a much stronger tendency to remain in solution than chloropicrin. The transport of chloropicrin from solution to the atmosphere is likely to be significant environmentally, while MITC shows a much lower rate of volatilization. When transferred to the atmosphere, oxidation and photochemical reactions are likely to dominate the transformation of both chloropicrin and MITC, rather than heterogenous reactions.     

Effect of natural organic matter and green microalga on carboxyl-polyethylene glycol coated CdSe/ZnS quantum dots stability and transformations under freshwater conditions

The influence of pH, ionic strength, presence of humic or alginic acids, extracellular polymeric substances (EPS), or freshwater microalga Chlorella kesslerii on the stability and transformation of carboxyl-PEG-CdSe/ZnS core/shell quantum dots (QDs) in terms of number, hydrodynamic size and fluorescence of individual particles, was studied by fluorescence correlation spectroscopy. Obtained results demonstrated that QDs form stable dispersions at nanomolar concentrations under conditions typical for freshwaters. The presence of 5 or 15 mg C L⁻¹ of humic acid or 50 mg C L⁻¹ EPS did not significantly affect these parameters. In contrast, 5 or 50 mg C L⁻¹ alginate at ionic strength of 10 mM shifted the hydrodynamic radius toward larger values, suggesting a possible capture of QDs by the linear alginate chains. The addition of microalga to the QD dispersions resulted in a slight reduction of the number of QDs and a significant decline in the fluorescence of individual QDs.     

Solubilization properties of polycyclic aromatic hydrocarbons by saponin, a plant-derived biosurfactant

The enhanced solubilization of polycyclic aromatic hydrocarbons (PAHs) by saponin, a plant-derived non-ionic biosurfactant, was investigated. The results indicated that the solubilization capabilities of saponin for PAHs were greater than some representative synthetic non-ionic surfactants and showed strong dependence on solution pH and ionic strength. The molar solubilization ratio (MSR) of saponin for phenanthrene was about 3-6 times of those of the synthetic non-ionic surfactants, and decreased by about 70% with the increase of solution pH from 4.0 to 8.0, but increased by approximately 1 times with NaCl concentration increased from 0.01 to 1.0 M. Heavy metal ions can enhance saponin solubilization for phenanthrene and the corresponding MSR values increased by about 25% with the presence of 0.01 M of Cd²⁺ or Zn²⁺. Saponin is more effective in enhancing PAHs solubilization than synthetic non-ionic surfactants and has potential application in removing organic pollutants from contaminated soils.     

Contamination and source differentiation of Pb in park soils along an urban-rural gradient in Shanghai

Urban soil Pb contamination is a great human health risk. Lead distribution and source in topsoils from 14 parks in Shanghai, China were investigated along an urban-rural gradient. Topsoils were contaminated averagely with 65 mg Pb kg⁻¹, 2.5 times higher than local soil background concentrations. HCl-extracts contained more anthropogenic Pb signatures than total sample digests as revealed by the higher ^207/206Pb and ^208/206Pb ratios in extracts (0.8613 ± 0.0094 and 2.1085 ± 0.0121 versus total digests 0.8575 ± 0.0098 and 2.0959 ± 0.0116). This suggests a higher sensitivity of HCl-extraction than total digestion in identifying anthropogenic Pb sources. Coal combustion emission was identified as the major anthropogenic Pb source (averagely 47%) while leaded gasoline emission contributed 12% overall. Urbanization effects were observed by total Pb content and anthropogenic Pb contribution. This study suggests that to reduce Pb contamination, Shanghai might have to change its energy composition to clean energy.     

Neptunium(V) adsorption to calcite

The migration behavior of the actinyl ions U(VI)O₂²⁺, Np(V)O₂⁺ and Pu(V,VI)O₂^(+,2+) in the geosphere is to a large extend controlled by sorption reactions (inner- or outer-sphere adsorption, ion-exchange, coprecipitation/structural incorporation) with minerals. Here NpO₂⁺ adsorption onto calcite is studied in batch type experiments over a wide range of pH (6.0–9.4) and concentration (0.4 μM–40 μM) conditions. pH is adjusted by variation of CO₂ partial pressure. Adsorption is found to be pH dependent with maximal adsorption at pH 8.3 decreasing with increasing and decreasing pH. pH dependence of adsorption decreases with increasing Np(V) concentration. EXAFS data of neptunyl adsorbed to calcite and neptunyl in the supernatant shows differences in the Np(V)-O-yl distance, 1.85 ± 0.01 Å for the adsorbed and 1.82 ± 0.01 Å for the solution species. The equatorial environment of the neptunyl in solution shows about 5 oxygen neighbours at 2.45 ± 0.02 Å. For adsorbed neptunyl there are also about 5 oxygen neighbours at 2.46 ± 0.01 Å. An additional feature in the adsorbed species' R-space spectrum can be related to carbonate neighbours, 3 to 6 carbon backscatterers (C-eq) at 3.05 ± 0.03 Å and 3 to 6 oxygen backscatterers (O-eq2) at 3.31 ± 0.02 Å. The differences in the Np(V)-O-yl distance and the C-eq and O-eq2 backscatterers which are only present for the adsorbed species indicate inner-sphere bonding of the adsorbed neptunyl species to the calcite surface. Experiments on adsorption kinetics indicate that after a fast surface adsorption process a continuous slow uptake occurs which may be explained by incorporation via surface dissolution and reprecipitation processes. This is also indicated by the part irreversibility of the adsorption as shown by increased K_D values after desorption compared to adsorption.     

Effects of pH and ionic strength on sulfamethoxazole and ciprofloxacin transport in saturated porous media

Many antibiotics regarded as emerging contaminants have been frequently detected in soils and groundwater; however, their transport behaviors in soils remain largely unknown. This study examined the transport of two antibiotics, sulfamethoxazole (SMZ) and ciprofloxacin (CIP), in saturated porous media. Laboratory columns packed with quartz sand was used to test the effects of solution pH and ionic strength (IS) on their retention and transport. The results showed that these two antibiotics behaved differently in the saturated sand columns. In general, SMZ manifested a much higher mobility than CIP for all experimental conditions tested. Almost all SMZ transported through the columns within one pore volume in deionized water (i.e., pH=5.6, IS=0), but no CIP was detected in the effluents under the same condition after extended column flushing. Perturbations in solution pH (5.6 and 9.5) and IS (0 and 0.1M) showed no effect on SMZ transport in the saturated columns. When pH increased to 9.5, however, ~93% of CIP was eluted from the sand columns. Increase of IS from 0 to 0.1M also slightly changed the distribution of adsorbed CIP within the sand column at pH 5.6, but still no CIP was detected in the effluents. A mathematical model based on advection-dispersion equation coupled with equilibrium and kinetic reactions successfully simulated the transport of the antibiotics in water-saturated porous media with R(2)=0.99.     

Preparation of various thiol-functionalized carbon-based materials for enhanced removal of mercury from aqueous solution

In this work, biochar (BC), activated carbon (AC), and graphene oxide (GO) were thiol-functionalized using 3-mercaptopropyltrimethoxysilane (3-MPTS) (named as BCS, ACS, and GOS, respectively). BCS, ACS, and GOS were synthesized mainly via the interaction between hydrolyzed 3-MPTS and surface oxygen-containing functional groups (e.g., –OH, O–C=O, and C=O) and π-π interaction. The materials before and after modification were characterized and tested for mercury removal, including sorption kinetics and isotherms, the effects of adsorbent dosage, initial pH, and ionic strength. Pseudo-second-order sorption kinetic model (R² = 0.992~1.000) and Langmuir sorption isotherm model (R² = 0.964~0.998) fitted well with the sorption data of mercury. GOS had the most –SH groups with the largest adsorption capacity for Hg²⁺ and CH₃Hg⁺ (449.6 and 127.5 mg/g), followed by ACS (235.7 and 86.7 mg/g) and BCS (175.6 and 30.3 mg/g), which were much larger than GO (96.7 and 4.9 mg/g), AC (81.1 and 24.6 mg/g), and BC (95.6 and 9.4 mg/g). GOS and ACS showed stable mercury adsorption properties at a wide pH range (2~9) and ionic strength (0.01~0.1 mol/L). Mercury maybe removed by ligand exchange, surface complexation, and electrostatic attraction.

     

PM10 measurements at McMurdo Station,Antarctica

PM₁₀ aerosols at McMurdo Station, Antarctica were sampled continuously during the austral summers of 1995–1996 and 1996–1997. PM₁₀ (particles with aerodynamic diameters less than 10 μm) mass concentrations at Hut Point, located less than 1 km from downtown McMurdo, averaged 3.4 μg m⁻³, more than an order of magnitude lower than the USEPA annual average National Ambient Air Quality Standard (NAAQS) of 50 μg m⁻³. Concentrations of methanesulfonate and nitrate were similar to those measured at other Antarctic coastal sites. Non-sea-salt sulfate (NSS) concentrations on Ross Island were higher than those found at other coastal locations. The average elemental carbon concentration (129 ng m⁻³) downwind of the station was two orders of magnitude higher than those measured at remote coastal and inland Antarctic sites during summer. Average sulfur dioxide concentrations (746 ng m⁻³) were 3–44 times higher than those reported for coastal Antarctica. Concentrations of Pb and Zn were 17 and 46 times higher than those reported for the South Pole. A methanesulfonate to biogenic sulfate ratio (R) of 0.47 was derived that is consistent with the proposed temperature dependence of R.     

Influence of air mass trajectories on the chemical composition of precipitation in India

Chemical composition of precipitation was measured with wet-only samplers at a rural site at Bhubaneswar in eastern India during 1997–1998. All rain events were compared with trajectories and precipitation fields from the ECMWF. The pH and ionic concentrations were found to vary systematically with the origin of air and the amount of rainfall along the trajectory. A seasonal cycle for pH was found with a monthly median pH below 5.0 during October–December. The highest monthly median concentration of Ca²⁺ was found in May with 20 μmol l⁻¹ and for SO₄²⁻ in January with 52 μmol l⁻¹. Samples with trajectories within 400 km from Bhubaneswar during the last 5 days were found to have a median pH slightly below 5.0 as an average. These samples also had the highest concentration for all measured ions, indicating large pollution sources within the region. Samples with continental origin showed a decrease of ∼70% in concentration if there had been rain during >50% of the last 5 days compared to rain during <50% of the last 5 days. High concentrations of Na⁺ and Cl⁻ were also found in continental samples. Resuspension of previously deposited sea salt is believed to be the reason. The data were compared with data from three other sites in western India and higher concentrations of almost all ions (NH₄⁺ being the exception) compared to Bhubaneswar were found at the west coast in monsoon samples.     

Chlorination of chlortoluron: kinetics, pathways and chloroform formation

Chlortoluron chlorination is studied in the pH range of 3-10 at 25 ± 1 °C. The chlorination kinetics can be well described by a second-order kinetics model, first-order in chlorine and first-order in chlortoluron. The apparent rate constants were determined and found to be minimum at pH 6, maximum at pH 3 and medium at alkaline conditions. The rate constant of each predominant elementary reactions (i.e., the acid-catalyzed reaction of chlortoluron with HOCl, the reaction of chlortoluron with HOCl and the reaction of chlortoluron with OCl⁻) was calculated as 3.12 (± 0.10) × 10⁷ M⁻² h⁻¹, 3.11 (±0.39) × 10² M⁻¹ h⁻¹ and 3.06 (±0.47) × 10³ M⁻¹ h⁻¹, respectively. The main chlortoluron chlorination by-products were identified by gas chromatography-mass spectrometry (GC-MS) with purge-and-trap pretreatment, ultra-performance liquid chromatography-electrospray ionization-MS and GC-electron capture detector. Six volatile disinfection by-products were identified including chloroform (CF), dichloroacetonitrile, 1,1-dichloropropanone, 1,1,1-trichloropropanone, dichloronitromethane and trichloronitromethane. Degradation pathways of chlortoluron chlorination were then proposed. High concentrations of CF were generated during chlortoluron chlorination, with maximum CF yield at circumneutral pH range in solution.     

SMX degradation by ozonation and UV radiation: a kinetic study

The rate constants of sulfamethoxazole (SMX) degradation by ozonation and UV₂₅₄ radiation were investigated under various parameters including influent ozone gas concentration, initial SMX concentration, UV light intensity, ionic strength, water quality in terms of varying anions (bicarbonate, sulfate and nitrate), humic acid (HA) and pH. The results indicated that the removal of SMX by ozonation and UV₂₅₄ radiation fitted well to a pseudo first-order kinetic model and the rate constants were in the range of (0.9-9.8) × 10⁻³ and (1.7-18.9) × 10⁻³ s⁻¹, respectively. The second-order rate constants of SMX with ozone (k_O3), under varying operational parameters, were also determined and varied in the range of (0.60-3.38) ± 0.13 × 10⁵ M⁻¹ s⁻¹. In addition, SMX degradation through UV pretreatment followed by ozonation in the presence of HA was proved to be an effective method which can remove SMX with a low ozone dose. The results suggested that ozonation of SMX was more affected by concentration of influent ozone gas, alkalinity, and HA, while incident UV light intensity, pH, and HA were the dominant factors influencing UV degradation of SMX.     

Sulfadimethoxine and sulfaguanidine: their sorption potential on natural soils

Sulfonamides (SAs) are one of the oldest groups of veterinary chemotherapeutic agents. As these compounds are not completely metabolized in animals, a high proportion of the native form is excreted in feces and urine. They are therefore released either directly to the environment in aquacultures and by grazing animals, or indirectly during the application of manure or slurry. Once released into the environment, SAs become distributed among various environmental compartments and may be transported to surface or ground waters. The physicochemical properties of SAs, dosage and nature of the matrix are the factors mainly responsible for their distribution in the natural environment. Although these rather polar compounds have been in use for over half a century, knowledge of their fate and behavior in soil ecosystems is still limited. Therefore, in this work we have determined the sorption potential of sulfadimethoxine and sulfaguanidine on various natural soils. The influence on sorption of external factors, such as ionic strength and pH, were also determined. The sorption coefficients (K_d) obtained for the sulfonamides investigated were quite low (from 0.20 to 381.17 mL g⁻¹ for sulfadimethoxine and from 0.39 to 35.09 mL g⁻¹ for sulfaguanidine), which indicated that these substances are highly mobile and have the potential to run off into surface waters and/or infiltrate ground water. Moreover, the sorption of these pharmaceuticals was found to be influenced by OC, soil solution pH and ionic strength, with higher K_d values for soils of higher OC and lower K_d values with increasing pH and ionic strength.     

Wet deposition mercury fluxes in the Canadian sub-Arctic and southern Alberta,measured using an automated precipitation collector adapted to cold regions

This paper reports mercury (Hg) concentrations and fluxes in precipitation that was collected from 2006 to 2008 at three sites in Canada: sub-Arctic boreal forest, sub-Arctic coast, and southern Alberta, using cold-adapted precipitation collectors which operated reliably at temperatures below ?30 °C during the study. The southern Alberta site (Crossfield) may be influenced by Calgary urban air, whereas the sub-Arctic coastal (Churchill, Manitoba) and boreal forest (Fort Vermilion, Alberta) sites are in more remote northern areas. Annual mean Hg concentrations in precipitation (5.0–9.2 ng L^?1) at the study sites were in the lower half of the range reported for southern Canada and the USA by the Mercury Deposition Network (MDN). But owing to typically low precipitation rates, gross wet Hg fluxes (0.54–2.0 μg m^?2 yr^?1) were among the lowest reported by MDN, with Crossfield having about twice the flux in 2007 of the other two sites. Flux was significantly correlated with precipitation, and thus was highest in summer (June–August) and lowest during winter, a pattern typical of other temperate continental locations. There was no evidence of higher wet Hg fluxes or concentrations in springtime at Churchill where atmospheric mercury depletion events (AMDEs) occur. Measured gross deposition fluxes at the study locations were ～2–8 times lower than estimated by GEOS-Chem and GRAHM atmospheric models. The largest discrepancy occurred for Churchill, which raises the question of how well Hg deposition from AMDEs is described by current models. Better agreement between measurements and models was obtained from MDN stations in Alberta and Alaska, where wet Hg fluxes were 2–10 times higher than the study sites either because of power plant emissions (Alberta), or because of high precipitation rates (Alaska).     

Comparison of biochar- and activated carbon-supported zerovalent iron for the removal of Se(IV) and Se(VI): influence of pH,ionic strength,and natural organic matter

Biochar (BC) and activated carbon (AC) were both produced from corn straw. Biochar-supported zerovalent iron (BC-ZVI) and activated carbon-supported zerovalent iron (AC-ZVI) were synthesized and applied for Se(IV)/Se(VI) removal. The sorption capacity of BC-ZVI for Se(IV) and Se(VI) was reported at 62.52 and 35.39 mg g^?1, higher than that of AC-ZVI (56.02 and 33.24 mg g^?1), respectively, due to its higher iron content and more positive charges. The spectroscopic analyses showed that Se(IV)/Se(VI) were reduced to Se(0)/Se(-II) of less toxicity and solubility. The effects of various factors such as pH, ionic strength, co-existing cations and anions, and natural organic matter (NOM) were also investigated. Ionic strength showed no significant effect on Se(IV)/Se(VI) removal, but pH was critical. The presence of NO₃^? and SO₄^2? did not cause obvious inhibition to the removal, while PO₄^3? inhibited the sorption capacity of BC-ZVI and AC-ZVI for Se(IV)/Se(VI) significantly. Common cations (K⁺, Ca²⁺, and Mg²⁺) were found to slightly enhance the removal, while NOM significantly decreased the sorption capacity of BC-ZVI and AC-ZVI for Se(IV)/Se(VI). Besides, NOM showed stronger inhibition effect on AC-ZVI than that on BC-ZVI. These results indicated that BC-ZVI, compared with AC-ZVI, could be a promising sorbent to remove Se(IV)/Se(VI) due to its low cost and high efficiency.

     

Mercury transport between sediments and the overlying water of the St. Lawrence River area of concern near Cornwall, Ontario

Contaminated sediments in the St. Lawrence River remain a difficult problem despite decreases in emissions. Here, sediment and pore water phases were analyzed for total mercury (THg) and methyl mercury (MeHg) and diffusion from the sediment to the overlying water was 17.5 ± 10.6 SE ng cm⁻² yr⁻¹ for THg and 3.8 ± 1.7 SE ng cm⁻² yr⁻¹ for MeHg. These fluxes were very small when compared to the particle-bound mercury flux accumulating in the sediment (183 ± 30 SE ng cm⁻² yr⁻¹). Studies have reported that fish from the westernmost site have higher Hg concentrations than fish collected from the other two sites of the Cornwall Area of Concern, which could not be explained by differences in the Hg flux or THg concentrations in sediments, but the highest concentrations of sediment MeHg, and the greatest proportions of MeHg to THg in both sediment and pore water were observed where fish had highest MeHg concentrations.     

Light-induced heterogeneous ozone processing on organic coated particles: Kinetics and condensed-phase products

For the first time we investigated the effect of solar irradiation upon the heterogeneous ozonation of adsorbed 3,4,5-trimethoxybenzaldehyde on solid surface. Light-induced heterogeneous reactions between gas-phase ozone and 3,4,5-trimethoxybenzaldehyde adsorbed on silica particles were performed and the consecutive reaction products were identified. At an ozone mixing ratio of 250 ppb, the loss of 3,4,5-trimethoxybenzaldehyde ranged from 1.0 · 10^?6 s^?1 in the dark to 2.9 · 10^?5 s^?1 under light irradiation. Such large enhancement of 29 times clearly shows the importance of light (λ > 300 nm) during the heterogeneous ozonolysis on organic coated particles.The reaction products identified in this study (3,4,5-trimethoxybenzoic acid, syringic acid, methyl 3,4,5-trimethoxybenzoate) absorb light in the spectral window (λ > 300 nm) which implies that light-induced heterogeneous ozone processing can have an influence on the aerosol surfaces by changing their physico-chemical properties.The main identified product of the heterogeneous reactions between gas-phase ozone and 3,4,5-trimethoxybenzaldehyde under dark conditions and in presence of light was 3,4,5-trimethoxybenzoic acid. For this reason we estimated the carbon yield of 3,4,5-trimethoxybenzoic acid. Carbon yields of 3,4,5-trimethoxybenzoic acid decreased with increasing ozone mixing ratio; from 40% at 250 ppb to 15% at ≥2.5 ppm under dark conditions. At ozone mixing ratio (250 ppb–1 ppm), carbon yields of 3,4,5-trimethoxybenzaldehyde are relatively higher in the experiment under dark condition than under simulated solar light.