Particulate Surface Research Articles

Lipid biomarkers and organic matter carbon isotopes in estuarine sediments as proxies for evaluating seawater intrusion

Coastal wetlands and estuarine sediments are characteristics of tide-dominated environments and retain a record of seawater intrusion and possibly sea-level changes. A variety of methods including the C/N ratio and δ13C of bulk organic matter in the sediment have been employed in estuarine studies, but they are generally non-specific indicators. Here we report using lipid biomarkers to evaluate the extent of seawater intrusion based on an estuary in eastern China, Xinyanggang. Along the river from the estuary mouth upstream to the freshwater head, the vegetation shifts quickly from salt-tolerant Spartina (C4) to the less tolerant reed Phragmites (C3), both of which have distinguished δ13C values and biomarker distribution. The δ13C values of particulate organic matter (POM) and surface sediment decreased from the estuary mouth upstream, indicating the reduced contributions from Spartina and marine phytoplankton to the POM and surface sediment and increased inputs from Phragmites. The C32/C30 alkanol and cholesterol/sitosterol ratio decreased in the surface sediments, faithfully recording the variations in the contributions from Spartina and Phragmites. The combination of biomarker distribution and organic matter δ13C in the sediments can be used as indicators for sea water intrusion into the estuary/river.

Plasma polymerization of sulfur-rich and water-stable coatings on silica particles

The plasma polymerization of thiophene has been applied to develop sulfur-rich coatings on silica particles. A range of plasma input energies (0.06–2.4kJ⋅cm−3) and deposition times (2–30min) were applied in the plasma polymerization process. The surface chemistry of plasma polymerized thiophene (PPT)-coated particles was evaluated via X-ray photoelectron spectroscopy (XPS), while the distribution of sulfur-containing groups was studied by time of flight secondary ion mass spectroscopy (ToF-SIMS). Washburn capillary rise measurements quantified the hydrophobicity of uncoated and PPT-coated particles. The stability of PPT-coated particles in water was evaluated for immersion durations of 5min to 24h. Surface chemistry analyses showed a rapid and homogenous formation of sulfur-rich PPT layers on particles at a low plasma input energy of 0.06kJ⋅cm−3. ToF-SIMS results suggested the formation of high density thiol functionalities on surfaces. PPT coatings demonstrated high stability in water, which was attributed to their highly hydrophobic character. The deposition rate of PPT on particles and planar surfaces has also been compared in this investigation. It has been shown that the plasma polymerization of a monomer on a 2-D surface produces significantly thicker coatings in comparison to a 3-D surface. The plasma polymerization of thiophene via a rotating reactor was found to be an effective method for the fabrication of sulfur-rich coatings on particulate surfaces.

Development of negatively charged particulate surfaces through a dry plasma-assisted approach

A completely dry method has been introduced for the development of negatively charged oxidized sulfur-terminated particles.

Particulate Characterization and Size Distribution in the Exhaust of a Gasoline Homogeneous Charge Compression Ignition Engine

Agglomeration, coagulation, surface condensation, adsorption and oxidation processes are a part of particulate evolution process and lead to significant changes in characteristics of particulate matter (PM), when they enter the atmosphere. PM formation can be significantly reduced by advanced combustion concepts such as homogeneous charge compression ignition (HCCI). In the present study, experiments were performed in a modified gasoline fuelled HCCI engine at varying intake air temperatures (T_i), exhaust gas recirculation (EGR) rates and relative air-fuel ratios (λ). For particulate characterization, a partial flow dilution tunnel was used to collect particulate samples on a filter paper. These particulate samples were analysed for benzene soluble organic fraction (BSOF), trace metals, and particulate morphology using scanning electron microscopy (SEM). Physical characterisation of particulates was done using engine exhaust particle sizer (EEPS), which measured the particle size-number distribution. In the experiments, higher PM was found for richer fuel-air mixtures and it further increased with application of EGR. Trace metals were found to be significantly lower for HCCI generated PM, which increased with increasing EGR. BSOF was negligible as compared to total PM which showed relatively lower toxicity of gasoline HCCI particulates. Total number of particles reduced with increasing λ, however particulate size-number distribution curve shifted away from accumulation mode, indicating that the particulate size decreased with increasing λ. Higher particle size-number distribution and particle size-mass distribution were observed for increasing T_i. Particulate surface area and volume also increased with increasing T_i and mixture strength.

Ceramic particulate thermal barrier surface coatings for glass fibre-reinforced epoxy composites

This study investigates the thermal barrier efficiency of five commercially available ceramic nano and micro particles deposited on the surfaces of glass fibre-reinforced epoxy composites (GRE). Two approaches of application of deposition of ceramic particles have been undertaken, firstly where the ceramic particles were dispersed in a phenolic resin binder and applied on a GRE surface by a K-bar coater and the second where extra ceramic particles were sprayed on the first coating while the resin was partially cured to enable the surface to be completely covered by ceramic particles, leaving no resin exposed. The thermal barrier efficiency of these coatings was evaluated from the cone calorimetric parameters at incident heat fluxes of 35 and 50 kW/m2 as well as from temperature gradient through the samples’ thicknesses, measured by inserting thermocouples on the exposed and back surfaces during the cone tests. The morphology and durability of the coatings to water absorption, peeling, impact and flexural loading were also studied. The results showed that the surface layers of all coated samples were uniform and there was a strong adhesion between the coating and the substrate. Moreover, they did not adversely affect the mechanical properties of GRE composite while improving the mechanical property retention of GRE composites after exposure to heat.

Biocompatible PEGylated MoS2 nanosheets: Controllable bottom-up synthesis and highly efficient photothermal regression of tumor

Two-dimensional transition metal dichalcogenides, particularly MoS2 nanosheets, have been deemed as a novel category of NIR photothermal transducing agent. Herein, an efficient and versatile one-pot solvothermal synthesis based on “bottom-up” strategy has been, for the first time, proposed for the controlled synthesis of PEGylated MoS2 nanosheets by using a novel “integrated” precursor containing both Mo and S elements. This facile but unique PEG-mediated solvothermal procedure endowed MoS2 nanosheets with controlled size, increased crystallinity and excellent colloidal stability. The photothermal performance of nanosheets was optimized via modulating the particulate size and surface PEGylation. PEGylated MoS2 nanosheets with desired photothermal conversion performance and excellent colloidal and photothermal stability were further utilized for highly efficient photothermal therapy of cancer in a tumor-bearing mouse xenograft. Without showing observable in vitro and in vivo hemolysis, coagulation and toxicity, the optimized MoS2-PEG nanosheets showed promising in vitro and in vivo anti-cancer efficacy.

Sources, Distribution and Preservation of Organic Matter in a Tropical Estuary (Godavari, India)

Major sources and distribution of organic matter (OM) were examined in a tropical monsoonal estuary, the Godavari, using content and isotopic signatures in suspended particulate matter and surface sediments during no-discharge period. The lower ( 10 km) estuaries have shown remarkably different features with reference to the sources, distribution and preservation of OM. The upper estuary is characterized by relatively high content of particulate organic carbon (POC) and chlorophyll- a (Chl-a) and low suspended matter and sediment OC. In contrast, the lower estuary is characterized by relatively low content of particulate OC and Chl-a and high suspended matter and sediment OC. Our data and model results showed that suspended particulate OM is derived predominantly from freshwater phytoplankton in the upper (∼85 %) and lower (∼60 %) estuaries, with a minor contribution from estuarine phytoplankton(∼25%)andterrestrialC3plants(∼10%)inthe lower estuary, during the study period. On the other hand, sediment OM in the upper and lower estuaries derived from both autochthonous and allochthonous sources with nearly equal contributions. Although relatively high in situ produc- tion was observed in the upper than the lower estuary, rela- tively low sediment OC was found in the former than the latter region, suggesting that strong influence of preservation conditions rather than surface biological production on OC accumulation in sediments. This is attributed to intense trans- formation of OM by heterotrophs in the upper than the lower estuary because of prevailing conducive conditions for degra- dation of OM in the upper estuary during the study period.

Tethering metal ions to photocatalyst particulate surfaces by bifunctional molecular linkers for efficient hydrogen evolution.

A simple and versatile method for the preparation of photocatalyst particulates modified with effective cocatalysts is presented; the method involves the sequential soaking of photocatalyst particulates in solutions containing bifunctional organic linkers and metal ions. The modification of the particulate surfaces is a universal and reproducible method because the molecular linkers utilize strong covalent bonds, which in turn result in modified monolayer with a small but controlled quantity of metals. The photocatalysis results indicated that the CdS with likely photochemically reduced Pd and Ni, which were initially immobilized via ethanedithiol (EDT) as a linker, were highly efficient for photocatalytic hydrogen evolution from Na2S-Na2SO3-containing aqueous solutions. The method developed in this study opens a new synthesis route for the preparation of effective photocatalysts with various combinations of bifunctional linkers, metals, and photocatalyst particulate materials.

Nanostructured lipid carriers containing a high percentage of a Pluronic copolymer increase the biodistribution of novel PDE4 inhibitors for the treatment of traumatic hemorrhage.

Although the application of nanotechnology to drug therapy has been widely investigated, very few nanomedicine-based treatments for traumatic hemorrhage have been reported so far. The aim of this work was to develop nanostructured lipid carriers (NLCs) loaded with phosphodiesterase 4 (PDE4) inhibitors to treat acute inflammation in peripheral organs. The pharmacokinetics and biodistribution of DSM-RX78 and EFB-1, two novel PDE4 inhibitors, were examined using rats as an animal model. Entrapment by NLCs resulted in sustained drug release. The plasma concentrations of DSM-RX78 and EFB-1 in NLCs were lower, and their half-lives were much shorter in the NLC condition than in the control condition. PDE4 inhibitors delivered in NLCs accumulated with high abundance in many organs, especially the brain and lungs. Polyethylene glycol (PEG) coating on the particulate surface (P-NLCs) significantly reduced brain delivery of the drugs. P-NLCs enhanced drug distribution to the lungs by 5-fold compared to free control. In vivo real-time imaging confirmed rapid escape of nanoparticles from the blood circulation. Histological examination and aminotransferase measurement revealed that P-NLCs containing EFB-1 improved hemorrhagic shock-induced injuries in the lungs, intestines, and liver. P-NLCs even reversed acute lung inflammation to the level observed in an uninjured condition. Our results indicate that NLC-based delivery of PDE4 inhibitors is a candidate treatment for traumatic hemorrhage.

Depth‐related distribution of a key gene of the tetraether lipid biosynthetic pathway in marine Thaumarchaeota

The distribution of isoprenoid glycerol dialkyl glycerol tetraethers (GDGT) lipids synthesized by Thaumarchaeota has been shown to be temperature-dependent in world oceans. Depth-related differences in the ammonia monooxygenase (amoA) of Thaumarchaeota have led to the classification of 'shallow' and 'deep water' clusters, potentially affecting GDGT distributions. Here, we investigate if this classification is also reflected in a key gene of the thaumarchaeotal lipid biosynthetic pathway coding for geranylgeranylglyceryl phosphate (GGGP) synthase. We investigated metagenomic databases, suspended particulate matter and surface sediment of the Arabian Sea oxygen minimum zone. These revealed significant differences in amoA and GGGP synthase between 'shallow' and 'deep water' Thaumarchaeota. Intriguingly, amoA and GGGP synthase sequences of benthic Thaumarchaeota clustered with the 'shallow water' rather than with 'deep water' Thaumarchaeota. This suggests that pressure and temperature are unlikely factors that drive the differentiation, and suggests an important role of ammonia concentration that is higher in benthic and 'shallow water' niches. Analysis of the relative abundance of GDGTs in the Arabian Sea and in globally distributed surface sediments showed differences in GDGT distributions from subsurface to deep waters that may be explained by differences in the GGGP synthase, suggesting a genetic control on GDGT distributions.

Photodegradation of Anthracene and Benzo[a]anthracene in Polar and Apolar Media: New Pathways of Photodegradation

The photochemical reactions of anthracene and benzo[a]anthracene polycyclic aromatic hydrocarbons (PAHs) in polar and apolar solvents (cyclohexane and water/acetonitrile) were studied using spectroscopic and chromatographic techniques. These homogenous photolysis experiments are used as simplified models to compare PAHs photochemistry in water and oil (or oil films). Moreover, these processes were to some extent used as model in literature in order to study those occurring on particulate matter and aerosol surfaces. In both media, new photochemical reaction products were found. Generally, the reaction rate in the polar medium is faster than that in the apolar medium, and the photodegradation quantum yields increase with increasing polarity of the medium. HPLC-absorption/emission analysis confirmed the literature reports that mainly oxygenated photoproducts, such as PAH-hydroxides, were formed. The novelty of this article is that GC-MS data revealed the presence of new photoproducts that have not yet been described. This simplified model system allowed us to characterize the product distribution, thus simplifying the interpretation of the photodegradation mechanism. The identification of new photofragmentation paths, originating by irradiation of primary PAH photoproducts, may suggest an innovative way of remediation triggered by light.

Electrochemical capacitance of poly(pyrrole-co-formylpyrrole)/sulfonated polystyrene layer-by-layer assembled multilayer films

Poly(pyrrole-co-formylpyrrole), P(Py-co-FPy) was prepared on poly(4-styrenesulfonate acid) (PSS) using layer-by-layer (LBL) self-assembly process in the presence of trifluoroacetic acid (TFA) through straightforward chemical polymerization. The P(Py-co-FPy) and PSS multilayer contained homogeneous particulate surfaces with a hierarchical porous structure, depending on the number of layers and the PSS concentration. The layer cycles gave rise to increased electrical conductivity from 2.8 × 10−4 S/cm at 2 layers to 3.2 × 10−3 S/cm at 10 layers, implying the benefit of the doping effect of the sulfonic group on the improvement of electrical conductivity for multilayer films. The electrostatic interaction between the P(Py-co-FPy) and the PSS layer was confirmed from UV–visible spectra. It is enhanced by the number of layers and PSS concentration. Cyclic voltammetry and electrochemical impedance measurements showed that the electrochemical capacitance of those multilayer films is influenced by the increase of the number of layers and the PSS concentration, suggesting that the multilayer film morphology affects the electrochemical behavior.

Contribution of allochthonous organic carbon across the Serrano River Basin and the adjacent fjord system in Southern Chilean Patagonia: Insights from the combined use of stable isotope and fatty acid biomarkers

Chilean Patagonia is characterized by an irregular geography involving many islands, peninsulas, channels, sounds and fjords, that prevent direct interaction between oceanic water masses and freshwater river discharges at the head of the continental fjords. In this paper, we evaluate the potential sources and composition of organic matter along the Serrano River basin and the adjacent channels and fjords in Southern Chilean Patagonia (51–52°S), as well as their importance for marine planktonic organisms. In spring of 2009, evidence of C:N ratio, δ13C, δ15N and fatty acids composition in particulate organic carbon (POC), surface sediment, soil, plankton, and vegetal tissue, as well some physical and chemical characteristics (i.e. salinity, dissolved oxygen, NO3−, NH4+, PO4−3, Si(OH)4), were measured in samples collected during the CIMAR 14 Fiordos oceanographic cruise. Significant differences in δ13C-POC were found between the terrestrial and marine environments but not within fjord stations. Along the fjord region, the high C:N ratio and depleted δ13C values in POC samples suggest that particulate organic matter (POM) in the upper level of the water column (0–10m depth) is supported by different sources. Terrestrial organic carbon exported by rivers may constitute a significant subsidy, up to 70% based on two end-member mixing model, to the fjord ecosystem. Furthermore, terrestrial carbon might account for a significant percentage of the zooplankton body carbon, estimated both by using isotopic (∼24–61%) and fatty acid analysis (∼14–61%). Isotopic analyses in marine sediment samples suggest that POC seems to be decoupled from terrestrial-influenced surface sources at the fjord stations, and the contribution of surrounding vegetation seemingly unimportant for carbon export to the benthos. Local hydrographic and geomorphological characteristics might determine the presence of oceanographic frontal zones, which in turn might explain differences in carbon sources found between POM and the surface sediments.

Analytical approach to estimating aerosol extinction and visibility from satellite observations

This study investigates the application of satellite data to the evaluation of aerosol extinction and visibility, for a better understanding of the spatio-temporal variation of local air quality in urban areas. A new analytical model based on aerosol microphysics and non-linear exponential fitting was applied to the analysis of aerosol extinction using aerosol optical thickness (AOT, τa) data retrieved from the MODerate-resolution Imaging Spectroradiometer (MODIS), over one of the largest global megacities: Seoul, Korea. The relationship between the MODIS τa and ground-based aerosol measurements of particulate matter mass concentration, extinction, and surface visibility was assessed over Seoul, Korea, during eight intensive observation periods in 2007–2009. The results clearly demonstrate that satellite-derived τa is a good surrogate for monitoring aerosol extinction and visibility over this study area. In particular, it is found that MODIS-estimated visibility values have a closer relation to the observed values than traditionally assumed Koschemeider's relation. The analytical results shown in this study can provide a better understanding of aerosol extinction and visibility in megacity, as well as for routine visibility monitoring.

Comparison of Physicochemical Surface Conditioning Methods for Adhesion of bis-GMA Resin Cement to Particulate Filler Composite and Surface Characterization

This study compared the effect of physicochemical surface conditioning methods on the adhesion of bis-GMA-based resin cement to particulate filler composite (PFC) used for indirect dental restorations. PFC blocks (N block = 54, n block = 9 per group) were polymerized and randomly subjected to one of the following surface conditioning methods: a) No conditioning (Control-C), b) Hydrofluoric acid (HF)etching for 60 s (AE60), c) HF for 90 s (AE90), d) HF for 120 s (AE120), e) HF for 180 s (AE180), and f) air-abrasion with 30 µm silica-coated alumina particles (AB). The conditioned surfaces were silanized with an MPS silane, and an adhesive resin was applied. Resin composite blocks were bonded to PFC using resin cement and photo-polymerized. PFC–cement–resin composite blocks were cut under coolant water to obtain bar specimens (1 mm × 0.8 mm). Microtensile bond strength test (μTBS)was performed in a universal testing machine (1 mm/min). After debonding, failure modes were classified using stereomicroscopy. Surface characterization was performed on a set of separate specimen surfaces using Scanning Electron Microscopy (SEM), X-Ray Dispersive Spectroscopy (XDS), X-Ray Photoelectron Spectroscopy (XPS), and Fourier Transform-Raman Spectroscopy (FT-RS). Mean μTBS (MPa) of C (35.6 ± 4.9) was significantly lower than those of other groups (40.2 ± 5.6–47.4 ± 6.1) (p < 0.05). The highest μTBS was obtained in Group AB (47.4 ± 6.1). Prolonged duration of HF etching increased the results (AE180: 41.9 ± 7), but was not significantly different than that of AB (p > 0.05). Failure types were predominantly cohesive in PFC (34 out of 54) followed by cohesive failure in the cement (16 out of 54). Degree of conversion (DC) of the PFC was 63 ± 10%. SEM analysis showed increased irregularities on PFC surfaces with the increased etching time. Chemical surface analyses with XPS and FT-RS indicated 11–70% silane on the PFC surfaces that contributed to improved bond strength compared to Group C that presented 5% silane, which seemed to be a threshold. Group AB displayed 83% SiO2 and 17% silane on the surfaces.

An investigation of ammonia and inorganic particulate matter in California during the CalNex campaign

Airborne observations from the California Research at the Nexus of Air Quality and Climate Change (CalNex) campaign in May and June 2010 are used to investigate the role of ammonia (NH3) in fine particulate matter (PM2.5) formation and surface air quality in California and test the key processes relevant to inorganic aerosol formation in the GEOS-Chem model. Concentrations of ammonia throughout California, sulfur dioxide (SO2) in the Central Valley, and ammonium nitrate in the Los Angeles (LA) area are underestimated several-fold in the model. We find that model concentrations are relatively insensitive to uncertainties in gas-particle partitioning and deposition processes in the region. Conversely, increases to anthropogenic livestock ammonia emissions (by a factor of 5) and anthropogenic sulfur dioxide emissions in the Central Valley (by a factor of 3–10) and a reduction of anthropogenic NOx emissions (by 30%) substantially reduce the bias in the simulation of gases (SO2, NH3, HNO3) throughout California and PM2.5 near LA, although the exact magnitudes of emissions in the region remain uncertain. Using these modified emissions, we investigate year-round PM2.5 air quality in California. The model reproduces the wintertime maximum in surface ammonium nitrate concentrations in the Central Valley (regional mean concentrations are three times higher in December than in June), associated with lower planetary boundary layer heights and colder temperatures, and the wintertime minimum in the LA region (regional mean concentrations are two times higher in June than December) associated with ammonia limitation. Year round, we attribute at least 50% of the inorganic PM2.5 mass simulated throughout California to anthropogenic ammonia emissions.

Formation of peste des petits ruminants spikeless virus-like particles by co-expression of M and N proteins in insect cells

Peste des petits ruminants virus (PPRV) has a non-segmented negative sense RNA genome and is classified within the Morbillivirus genus of the Paramyxoviridae. Using the Bac-to-Bac® baculovirus expression system, we constructed recombinant baculoviruses that were able to co-express the PPRV matrix and nucleocapsid proteins in insect cells under the control of the polyhedron and p10 promoters, respectively. The results showed that although both structural proteins were expressed at a relatively low level, the interaction between them caused the formation of virus-like particles (VLPs) by viewing of transmission electron microscopy. The VLPs morphologically resembled authentic PPRVs but lacked spikes protruding from the particulate surfaces. Interestingly, the diameter of PPRV VLPs ranged from 100 to 150nm, far less than the mean diameter (400–500nm) of parental virions.

Physical, Chemical and Optical Properties of Fine Aerosol as a Function of Relative Humidity at Gosan, Korea during ABC-EAREX 2005

The water uptake by fine aerosol in the atmosphere has been investigated at Gosan, Korea during ABC-EAREX 2005. The concentration of inorganic ion and carbon components, size distribution, and light scattering coefficients in normal and dry conditions were simultaneously measured for <TEX>$PM_{2.5}$</TEX> by using a parallel integrated monitoring system. The result of this study shows that ambient fine particles collected at Gosan were dominated by water-soluble ionic species (35%) and carbonaceous materials (18%). In addition, it shows the large growth of aerosol in the droplet mode when RH is higher than 70%. Size distribution of the particulate surface area in a wider size range (<TEX>$0.07-17{\mu}m$</TEX>) shows that the elevation of RH make ambient aerosol grow to be the droplet mode one around <TEX>$0.6{\mu}m$</TEX> or the coarse mode one, larger than <TEX>$2.5{\mu}m$</TEX>. Hygroscopic factor data calculated from the ratio of aerosol scattering coefficients at a given ambient RH and a reference RH (25%) show that water uptake began at the intermediate RH range, from 40% to 60%, with the average hygroscopic factor of 1.10 for 40% RH, 1.11 for 50% RH, and 1.17 for 60% RH, respectively. Finally, average chemical composition and the corresponding growth curves were analyzed in order to investigate the relationship between carbonaceous material fraction and hygroscopicity. As a result, the aerosol growth curve shows that inorganic salts such as sulphate and nitrate as well as carbonaceous materials including OC largely contribute to the aerosol water uptake.

The reflectance and negative polarization of light scattered from snow surfaces with different grain size in backward direction

The scattered light from particulate surfaces is useful for the verification of light scattering theory and the remote sensing applications. We present the photometric and polarimetric measurement results of natural snow surfaces with different grain size in the backward direction in field and in the laboratory. The snow grains are assumed that they exhibit both nonsphericity of shape and small-scale surface irregularities. All the samples display the prominent phenomena of brightness opposition surge and negative polarization; both of them are in dependence on the phase angle. There are clear effects of snow grain size on the photopolarimetric measurement results: the snow surfaces with small diameter show brighter reflectance than those of larger diameter, because of the amount of contaminants there is an exception of snow samples consist of small grain in the visible wavelengths; the absolute values of negative polarization increase with a decrease in grain size (corresponding to packing density), and the effect of snow grain size on negative polarization is quite significant in this study. The relation between snow grain size and negative polarization at near-backscattering geometries can be explained by the coherent backscattering mechanism. These results are useful to better understand the scattering property of high-albedo particulate surface with large particles.

Source contribution analysis of surface particulate polycyclic aromatic hydrocarbon concentrations in northeastern Asia by source–receptor relationships

We analyzed the source–receptor relationships for particulate polycyclic aromatic hydrocarbon (PAH) concentrations in northeastern Asia using an aerosol chemical transport model. The model successfully simulated the observed concentrations. In Beijing (China) benzo[a]pyren (BaP) concentrations are due to emissions from its own domain. In Noto, Oki and Tsushima (Japan), transboundary transport from northern China (>40°N, 40–60%) and central China (30–40°N, 10–40%) largely influences BaP concentrations from winter to spring, whereas the relative contribution from central China is dominant (90%) in Hedo. In the summer, the contribution from Japanese domestic sources increases (40–80%) at the 4 sites. Contributions from Japan and Russia are additional source of BaP over the northwestern Pacific Ocean in summer. The contribution rates for the concentrations from each domain are different among PAH species depending on their particulate phase oxidation rates. Reaction with O3 on particulate surfaces may be an important component of the PAH oxidation processes.