Variability in interference competition was studied in benthic marine communities of the arctic and subarctic Atlantic intertidal and shallow subtidal zones. We sampled multiple square-metre quadrats at distances of 101, 103, and 105 m apart around the high polar island of Spitsbergen (Svalbard Archipelago). We also took some similar samples in Iceland and in the Faeroe Islands (106 m apart from Spitsbergen samples). Encrusting fauna were present on high arctic intertidal rocks but we only found competitive interactions on subtidal substrata. On subarctic Icelandic and Faeroese shores, in contrast, spatial competition was common even in the intertidal zone. Analysis of variance of competition intensity data (numbers of interactions per area) revealed multiple factors to be significant influences explaining variability. Amongst the 101-, 103-, and 105-m spatial scales, only the largest emerged as a significant term. Whether intra- or interspecific competition dominated the types of interactions varied greatly between sites: 21–97% of competition was intraspecific. The proportion of competitive encounters resulting in a decided outcome (i.e. a win for one competitor and a loss for the other, rather than a tie or standoff between them) showed little variability at any scale. All the values of competition transitivity (how hierarchical a pecking order is) were very high compared to values reported in the literature from any other (polar or non-polar) locality. Variability in this measure was generally <10% across scales. We conclude from our data that great care must be taken in interpreting patterns of competition between similar taxa in large-scale space or time. Not only did most aspects of competition in our study communities vary significantly at the 105-m scale but different aspects of competition varied at different scales and by hugely different amounts.Communicated by J.P. Thorpe, Port Erin 相似文献
Oxidation of aldehydes to carboxylic acids is a major reaction. Conventionally, this reaction is carried out with oxidants and metal catalysts, thus producing unwanted metal waste. Recently, aqueous media have been used as an alternative for toxic organic solvents. Here, we tested the clathrate-structured, neutral hydrogen peroxide adduct 4Na2SO4·2H2O2·NaCl for the oxidation of aldehydes to acids in aqueous solution. We found that various aromatic, heteroaromatic and aliphatic aldehydes were selectively oxidized to corresponding acids in 70–98% yields. This simple acid–base treatment allows to separate easily the acid product in high purity without any organic solvent. Moreover, the adduct is produced using 25% H2O2, with inexpensive sodium sulphate, Na2SO4, and sodium chloride, NaCl. The adduct is a non-toxic white crystalline solid, readily soluble in water, and easy to handle. 相似文献
To test the hypothesis that stable isotope ratios from marine organisms vary, the δ15N and δ13C values from fish and squid collected in Alaskan waters were measured across years (1997, 2000, and 2005), seasons, geographic
locations, and different size/age classes, and between muscle tissue and whole animals. Temporal, geographic, and ontogenetic
differences in stable isotope ratios ranged from 0.5–2.5‰ (δ15N) to 0.5–2.0‰ (δ13C). Twenty-one comparisons of stable isotope values between whole organisms and muscle tissue revealed only four small differences
each for δ15N and δ13C, making costly and space prohibitive collection of whole animals unnecessary. The data from this study indicate that significant
variations of stable isotope values from animals in marine systems necessitates collection of prey and predator tissues from
the same time and place for best interpretation of stable isotope analysis in foraging ecology studies. 相似文献
The spontaneous oxidation process of pristine silicon (Si) limits its application as photocatalyst or electrode in aqueous solution or moist air. Covering a protection layer on Si surface is an effective approach to overcome this disadvantage. In this paper, α-Fe2O3 is demonstrated to be an excellent alternative as a protection material. α-Fe2O3 layer was deposited around each p-type Si micropillar (SiMP) in well-ordered array by chemical bath deposition method. The diameter of SiMP was 5 mm and the thickness of α-Fe2O3 layer was about 20 nm. The photoeletrochemical stability of SiMP/α-Fe2O3 was proved by 10 circles cyclic voltammetry testing. Compared with SiMP, its optical absorption and photocurrent density improved 2 times and 4 times, respectively, and its onset potential for hydrogen evolution moved positively about 0.4 V. These improved performances could be ascribed to the enhanced photogenerated-charge-separation efficiency deriving from built-in electric field at the interface between Si and α-Fe2O3. The above results show an effective strategy to utilize Si material as photocatalyst or electrode in aqueous solution or moist air.
To decompose efficiently hydrogen cyanide (HCN) in exhaust gas, g-Al2O3-supported bimetallicbased Cu–Ni catalyst was prepared by incipient-wetness impregnation method. The effects of the calcination temperature, H2O/HCN volume ratio, reaction temperature, and the presence of CO or O2 on the HCN removal efficiency on the Cu–Ni/g-Al2O3 catalyst were investigated. To examine further the efficiency of HCN hydrolysis, degradation products were analyzed. The results indicate that the HCN removal efficiency increases and then decreases with increasing calcination temperature and H2O/HCN volume ratio. On catalyst calcined at 400°C, the efficiency reaches a maximum close to 99% at 480 min at a H2O/HCN volume ratio of 150. The HCN removal efficiency increases with increasing reaction temperature within the range of 100°C–500°C and reaches a maximum at 500°C. This trend may be attributed to the endothermicity of HCN hydrolysis; increasing the temperature favors HCN hydrolysis. However, the removal efficiencies increases very few at 500°C compared with that at 400°C. To conserve energy in industrial operations, 400°C is deemed as the optimal reaction temperature. The presence of CO facilitates HCN hydrolysis andincreases NH3 production. O2 substantially increases the HCN removal efficiency and NOx production but decreases NH3 production.
Stable isotopes are increasingly used in the study of trophic interactions of many aquatic animals and most recently cephalopods.
To evaluate the application of the method to squids, it is important to assess isotopic differences among and within consumer
tissues that may confound the resolution of ecological relationships. Inter- and intra-tissue isotopic variation was examined
in 55 individuals of the oceanic squid Todarodes filippovae that were collected at the beginning of April 2000 in the southwestern Indian Ocean (between 44°S, 76°E, and Saint Paul and
Amsterdam islands, 38°S, 78°E). Delipidated soft tissues (mantle, arm, buccal mass, gill and reproductive organs) showed small
δ13C and δ15N differences, which were probably tissue-specific. A lower carbon value was observed in the digestive gland as a consequence
of incomplete lipid removal. Hard tissues, such as beaks and gladii, had lower 15N values than soft tissues, which can be explained by the presence of chitin, a 15N-depleted molecule. Females (n = 38) and males (n = 17) had identical δ13C values, but females showed higher δ15N values than males. The difference was size-related rather than sex-related, however, as females were generally larger than
males. A comparison of similar-sized females and males produced identical nitrogen values. These data suggest dietary shifts
from lower to higher trophic levels during growth, because δ15N values of large T. filippovae were much higher than that of small specimens. As expected, nitrogen values of lower beaks and gladii of large squids increased
from the oldest to the most recently formed region, reflecting the progressive growth of chitinized tissues in parallel with
dietary changes. Sequential sampling along the growth increments of squid beaks and gladii can likely be used to produce a
chronological record of dietary information throughout an individual’s history. 相似文献
The explosive growth in anthropogenic energy consumption, coupled with the consequent environmental pollution, have been acknowledged as two impending challenges confronting humanity. Photocatalytic CO2 reduction to produce value-added hydrocarbon fuels, by using abundant solar energy and redundant atmospheric CO2, is an innovative way to satisfy global energy requirements whilst simultaneously reducing atmospheric CO2 levels. Although this notion is several decades old, it has unfortunately been lingering in a state of infancy due to inherently poor CO2-to-fuel conversion efficiencies, and the generation of low-value products (e.g., CO, HCHO). These pitfalls hamper this process from any potential commercial breakthrough and are primarily fuelled by the lack of progress in developing high-performance photocatalytic materials. Fortunately, the advent of nanotechnology has recently introduced many promising novel materials for this purpose. Here, we review photocatalysts with proven potential for converting CO2 into methanol, a high-value, energy-dense hydrocarbon fuel that is easily transported using existing pipeline infrastructure. Methanol possesses multifarious applications in the automobile, industrial and petrochemical sector. In addition, the development of direct methanol fuel cells (DMFCs) has introduced the tantalizing prospect of using methanol as a medium for storing solar energy that is easily converted to electricity via DMFCs. As such, methanol is an ideal fuel, with numerous advantages over its counterparts. This article reviews several photocatalysts that have been reported for this environmentally sustainable process of converting CO2 into methanol by photocatalysis. Specifically, the performance enhancement effected by adding dopant atoms, forming heterostructured composites and nanostructures, is investigated in terms of four key areas: (1) enhanced visible light sensitivity, (2) improved adsorption of reactants on the catalytic surface, (3) lowered electron–hole recombination and (4) increased CO2 reduction kinetics. The trends deduced therein are invaluable for researchers developing novel photocatalytic materials, which will utilize sunlight to convert CO2 into methanol with enhanced efficiency, thus ushering in the era of a green methanol-based economy. 相似文献
In this study, the photodegradation of three pharmaceuticals, namely Ibuprofen (IBP), Naproxen (NPX), and Cetirizine (CIZ) in aqueous media was investigated under UV irradiation. The photocatalyst used in this work consists of surface functionalized titanium dioxide (TiO2–NH2) nanoparticles grafted into Polyacrylonitrile (PAN)/multi-walled carbon nanotube composite nanofibers. Surface modification of the fabricated composite nanofibers was illustrated using XRD, FTIR, and SEM analyses.
Results
Sets of experiments were performed to study the effect of pharmaceuticals initial concentration (5–50 mg/L), solution pH (2–9), and irradiation time on the degradation efficiency. The results demonstrated that more than 99% degradation efficiency was obtained for IBP, CIZ, and NPX within 120, 40, and 25 min, respectively.
Conclusions
Comparatively, the photocatalytic degradation of pharmaceuticals using PAN-CNT/TiO2–NH2 composite nanofibers was much more efficient than with PAN/TiO2–NH2 composite nanofibers.
Sulfoxides are versatile synthetic intermediates for the preparation of biological products. Therefore, there is a need for efficient methods to oxidize sulfides into sulfoxides. Such oxidation may be catalyzed by magnetic nanocatalysts due to their good stability, easy synthesis, high surface area, low toxicity and easy separation by magnetic forces. Here we prepared a nanocatalyst by immobilization of the chitosan–Schiff base complex on supramagnetic Fe3O4 nanoparticles. The chitosan–Schiff base complex has been previously prepared by functionalization of chitosan with 5-bromosalicylaldehyde and metalation with copper(II) acetate. The catalyst was characterized by Fourier transform infrared, powder X-ray diffraction, transmission electron microscope, scanning electron microscopy, energy-dispersive X-ray spectroscopy and thermogravimetric analysis. Results show that the Fe3O4 nanoparticles and nanocatalyst were spherical in shape with an average size of 20 nm. Upon the covalently anchoring of chitosan–Schiff base Cu complex on the magnetic Fe3O4 nanoparticles, the average size increased to 60 nm. The prepared Fe3O4–chitosan–Schiff base Cu complex catalyzed very efficiently the oxidation of sulfides to sulfoxides with 100 % selectivity in all cases under green reaction conditions and excellent yields. Additionally, ease of recovery and reusability up to four cycles without noticeable loss of catalytic activity make the present protocol beneficial from industrial and environmental viewpoint. 相似文献
The flow of particulate nitrogen from marine net pen fish farm effluents to the surrounding biofouling community was quantified by means of stable isotopes of nitrogen. Plastic mesh substrates were deployed at 8 m depth near a sea bream fish farm and at a nearby reference site in the northern Gulf of Aqaba (Red Sea) to assess whether natural fouling organisms could sequester substantial quantities of farm-derived particulate nitrogen waste. A mixing equation, incorporating differences in nitrogen stable isotope composition, δ15N, between particulate organic matter (“source”) and fouling organisms (“sink”) at the fish farm and reference site, was used to estimate the amount of farm-derived nitrogen that was incorporated by the fouling community. Among the conspicuous fouling organisms examined, sponges, tunicates and polychaetes showed greatest uptake of fish farm N, where the mean fractions of farm-derived N estimated over the 2-year period of observation were 19±7, 22±6 and 31±8% of total organisms’ N content, respectively, with maximal recorded seasonal values of 68, 85 and 57%, respectively. Mean N uptake by mixed fouling communities (conspicuous + cryptic organisms) was as much as fivefold higher than that calculated for the sum of conspicuous taxa, suggesting that the retention efficiency is greater in mixed than in mono-specific biofouling communities. 相似文献
In summer 1998, shallow water corals at Sesoko Island, Japan (26°38′N, 127°52′E) were damaged by bleaching. In August 2003,
partially damaged colonies of the massive Porites lutea and the branching P. cylindrica were collected at depths of 1.0–2.5 m. The species composition of epilithic algal communities on dead skeletal surfaces of
the colonies (‘red turfs’, ‘green turfs’, ‘red crusts’) and the endolithic algae (living in coral skeletons) growing close
to and away from living coral polyps was determined. Carbon and nitrogen stable isotope values of organic matter (δ13C and δ15N) from all six of these biological entities were determined. There were no significant differences in the isotope composition
of coral tissues of the two corals, with P. lutea having δ13C of −15.3 to −9.6‰ and δ15N of 4.7–6.1‰ and P. cylindrica having similar values. Polyps in both species living close to an interface with epilithic algae had similar isotope values
to polyps distant from such an interface. Despite differences in the relative abundance of the algal species in red turfs
and crusts, their δ13C and δ15N values were not significantly different from each other (−18.2 to −13.9, −20.6 to −16.2, 1.1–4.3, and 3.3 to 4.9‰, respectively).
The green algal turf had significantly higher δ13C values (−14.9 to −9.3‰) than that of red turfs and crusts but similar δ15N (1.2–4.1‰) to the red algae. The data do not suggest that adjoining associations of epilithic algae and coral polyps exchange
carbon- and nitrogen-containing metabolites to a significant extent. The endolithic algae in the coral skeletons had δ13C values of −14.8 to −12.3‰ and δ15N of 4.0–5.4‰. Thus they did not differ significantly from the coral polyps in their carbon and nitrogen isotope values. The
similarity in carbon isotope values between the coral polyps and endolithic algae may be attributed to a common source of
CO2 for zooxanthellae and endolithic algae, namely, from respiration by the coral host. While it is difficult to fully interpret
similarity in the nitrogen isotope composition of coral tissue and of green endolithic algae and the difference in δ15N between green epilithic and endolithic algae, the data are consistent with nitrogen-containing metabolites from the scleractinian
coral serving as a significant source of nitrogen for the endolithic algae. 相似文献
We studied the removal mechanism and affecting factors of Fe2+-based replacement–precipitation process for treating CuEDTA-containing wastewaters. Since Fe2+ was easily oxidized to Fe3+ in the presence of oxygen, the chelated copper was removed by the synergetic effect of Fe3+ replacement and NaOH precipitation. Our experiments showed that the copper removal efficiency was considerably dependant
on pH conditions of the solution and molar ratio of Fe2+/Cu2+. 相似文献
We studied Na+/K+–ATPase activity and ultrastructure in gills of the hyper-hypo-regulating crab Chasmagnathus granulatus Dana, 1851 acclimated to different salinities: 10, 30 and 45, known to be hypo-, iso-, and hyper-osmotic to the hemolymph, respectively. After centrifugation of homogenates at 11,000 g, Na+/K+–ATPase activity was almost entirely found in the pellets from the posterior (6–8) and anterior (3–5) gills, whereas very little was detected in the supernatant liquid. Specific activity of gill 6 was 41.3, 30.2, and 28.2 µmol Pi h–1 mg prot–1 for crabs acclimated to 10, 30, and 45, respectively, the result for 10 being significantly higher than those at 30 and 45. Although the concentration of sodium at which the reaction rate is half-maximal (KM) was similar in the three acclimation salinities, only the enzyme from crabs acclimated to 10 was inhibited by high sodium concentration. Specific activity of gill 5 increased with the increment in external salinity (10.1, 15, and 18.1 µmol Pi h–1 mg prot–1 for 10, 30, and 45, respectively), the only significant difference being that between the extreme salinities. The epithelium thickness of the dorsal portion of gill 6 showed a variation among salinities: 21.7, 15.8 and 17.2 µm for 10, 30 and 45, respectively. There were significant differences in epithelium thickness between the 10 and the other salinities. In all three salinities, the ultrastructure of gill 6 epithelium showed a high density of mitochondria, estimated by their volume fraction (Vvm=0.307–0.355). These mitochondria were packed between extensive basolateral membrane interdigitations in ionocytes and pillar cells. Gill 5 showed three cell types: pillars which possess mitochondria packed between membrane folds only in their interdigitations with neighbouring cells; type-I cells 8.0 µm thick with low density of mitochondria (Vvm=0.088), and type-II cells, 9.9 µm thick and rich in mitochondria (Vvm=0.423), but lacking basolateral interdigitations. Vvm of type-I cells of gill 5 was significantly lower than those of type-II cells of the same gill and the ionocytes of gill 6. No significant difference in Vvm was detected between the latter cell types.Communicated by P.W. Sammarco, Chauvin 相似文献
Background, aim, and scopeThe focus of popular interest on the subject of acid rain has been on the effects, which it has on aquatic ecosystems. Aluminium toxicity and the bioavailability depend on the species of aluminium present. The cationic aluminium species are important for the phytotoxocity and for the precipitation of aluminium containing precipitate.Materials and methodsSpeciation diagrams of aqueous aluminium chloride solutions with tridecameric cations (Al13) at room temperature as function of concentration (1·10–1–1·10–5 mol·l–1 Al) and aging time (9 month) have been obtained from a kinetic method; these Ferron method offers a simple and inexpensive alternative for identification and quantification of aluminium cations.ResultsThe Al13-cation stability decrease with decreasing concentration and increasing aging time.DiscussionPolynuclear aluminium species can be formed in nature by the dissolution of Al-containing minerals, as a consequence of surface water acidification, followed by neutralization process. The question of the occurrence of the tridecameric polycation (Al13) in natural soil solutions and stream waters is of considerable interest.ConclusionsThe results are important on the occurrence of the Al13 in natural waters, for the precipitation of aluminium species by acidification and for the aluminium phytotoxicity.Recommendations and perspectivesThis research suggests strongly that Al13 should be negligible in natural soil and surface waters. The toxicity of Al13 to plants and aquatic organism in natural conditions may be considered to be very low. 相似文献
Mine wastes and tailings are considered hazardous to human health because of their potential to generate large quantities of highly toxic emissions of particulate matter (PM). Human exposure to As and other trace metals in PM may occur via inhalation of airborne particulates or through ingestion of contaminated dust. This study describes a laboratory-based method for extracting PM2.5–10 (coarse) and PM2.5 (fine) particles from As-rich mine waste samples collected from an historical gold mining region in regional, Victoria, Australia. We also report on the trace metal and metalloid content of the coarse and fine fraction, with an emphasis on As as an element of potential concern. Laser diffraction analysis showed that the proportions of coarse and fine particles in the bulk samples ranged between 3.4–26.6 and 0.6–7.6 %, respectively. Arsenic concentrations were greater in the fine fraction (1680–26,100 mg kg?1) compared with the coarse fraction (1210–22,000 mg kg?1), and Co, Fe, Mn, Ni, Sb and Zn were found to be present in the fine fraction at levels around twice those occurring in the coarse. These results are of particular concern given that fine particles can accumulate in the human respiratory system. Our study demonstrates that mine wastes may be an important source of metal-enriched PM for mining communities. 相似文献
PurposeLittle is known about the ecotoxicity of nanomaterials and there are no specific guidelines for sample preparation and testing. We set out to establish whether the method used to prepare TiO2 dispersions had a significant impact on aquatic ecotoxicity. We also followed the formation of agglomerates during the incubation period.MethodsWe applied the algal growth inhibition test (OECD test guideline no. 201). Dispersions were prepared by stirring and/or ultrasonication for different durations, and by filtration according to an OECD procedure recommended for testing difficult substances.ResultsSamples stirred for 7?d were not toxic, but EC20 values could be calculated for all the other treatments. Shorter treatments generated EC20 values in the range 1–27?mg/L. Only the shortest treatment (1 min stirring, 1 min ultrasonication) produced an unusually high EC20 value, indicating low toxicity. Development of agglomerate size and of toxicity depends on the nanoparticles. We found that ecotoxicity was predominantly caused by a fraction of nanoparticles and agglomerates obtained by passing dispersions through a 0.22-µm filter.ConclusionsWe propose a short treatment regime to generate the most relevant ecotoxicity data for TiO2, for example stirring for 1?min followed by 3 min ultrasonication. Until more data concerning the ecotoxicity of different fractions are available, we recommend the testing of unfiltered dispersions rather than filtrates. Relating ecotoxicity to the total hydrodynamic surface of the nanomaterials rather than concentration does not seem to improve the accuracy of ecotoxicity assessments using the algal growth inhibition test. 相似文献
The protobranch bivalve Solemya velum Say, 1822 has large gills, which harbor chemolithoautotrophic bacteria that supply the majority of the clams organic carbon. A substantial portion of the CO2, O2, H2S, and other nutrients necessary for symbiont autotrophy and host heterotrophy are acquired from the environment through the gills, whose large size may be necessary to facilitate the acquisition of sufficient O2 from S. velums habitat to meet the combined demands of the host and symbionts. Large gills may also result in an oversupply of CO2, which may in turn be responsible for the isotopically depleted 13C values observed in S. velum biomass (–31 to –34). Alternatively, gill hypertrophy may simply be an adaptation to house a large population of symbionts adjacent to their environmental source of dissolved gases and other nutrients. To better understand gill function in this symbiosis, gill weights, gill surface areas, and foot 13C values were measured as a function of total weights. S. velum gill weights were found to be a substantial portion of total clam weight, averaging 38% of wet weight, compared to nonsymbiotic protobranch bivalves Yoldia limatula Say, 1831 (5%) and Nucula proxima Say, 1822 (11%). Gill weights are a smaller percentage of total weight in larger individuals; the allometric equation for gill weight (G) as a function of total weight (M) is G=0.26M0.85. Dry weights scale similarly. Gill surface areas are immense; the average gill surface area measured was 107 cm2 g–1 total soft tissue wet weight, the highest value for any marine invertebrate. Gill surface area (SA) also scales with size (SA=69.8M0.85). When gill surface areas were calculated with respect to gill wet weights, they did not scale with size. The 13C values do not scale with size either, consistent with high rates of CO2 supply at all sizes. Extraordinarily high rates of CO2 supply relative to demand are supported by a model for CO2 delivery based on Ficks law and the allometric relationship between surface areas and total weight, consistent with a role for large gill surface areas in the generation of isotopically depleted tissue 13C values.Communicated by J. P. Grassle, New Brunswick 相似文献
It is difficult to meet the increasingly stringent environmental regulations by the application of conventional precipitation processes treating complex heavy metal wastewaters. We studied the potential of a new method for removing heavy metals from metal–EDTA wastewater by Fenton reaction followed by hydroxide precipitation. This process is referred to as Fenton reaction-hydroxide precipitation (FR-HP) process. This study investigated the use of FR-HP and ultrasonic/FR-HP processes for the removal of Ni(II) from Ni–EDTA wastewater. The results indicate that ultrasonic/FR-HP process is more effective for the removal of nickel ions than FR-HP process. 相似文献
The gene for the catalytic domain of thermostable endo-β-1,3-glucanase (laminarinase) LamA was cloned from Thermotoga maritima MSB8 and heterologously expressed in a bioengineered Synechococcus sp. PCC 7002. The mutant strain was cultured in a photobioreactor to assess biomass yield, recombinant laminarinase activity, and CO2 uptake. The maximum enzyme activity was observed at a pH of 8.0 and a temperature of 70°C. At a CO2 concentration of 5%, we obtained a maximum specific growth rate of 0.083 h–1, a biomass productivity of 0.42 g?L–1?d–1, a biomass concentration of 3.697 g?L–1, and a specific enzyme activity of the mutant strain of 4.325 U?mg–1 dry mass. All parameters decreased as CO2 concentration increased from 5% to 10% and further to 15% CO2, except enzyme activity, which increased from 5% to 10% CO2. However, the mutant culture still grew at 15% CO2 concentration, as reflected by the biomass productivity (0.26 g?L–1?d–1), biomass concentration (2.416 g?L–1), and specific enzyme activity (3.247 U?mg–1 dry mass).
Seasonal pattern of transport pathways and potential sources of PM2.5 in Chengdu during 2012–2013 were investigated based on hourly PM2.5 data, backward trajectories, clustering analysis, potential source contribution function (PSCF), and concentration-weighted trajectory (CWT) method. The annual hourly mean PM2.5 concentration in Chengdu was 97.4 mg·m–3. 5, 5, 5 and 3 mean clusters were generated in four seasons, respectively. Short-distance air masses, which travelled within the Sichuan Basin with no specific source direction and relatively high PM2.5 loadings (>80 mg·m–3) appeared as important pathways in all seasons. These short pathways indicated that emissions from both local and surrounding regions of Chengdu contributed significantly to PM2.5 pollution. The cities in southern Chengdu were major potential sources with PSCF>0.6 and CWT>90 mg·m–3. The northeastern pathway prevailed throughout the year with higher frequency in autumn and winter and lower frequency in spring and summer. In spring, long-range transport from southern Xinjiang was a representative dust invasion path to Chengdu, and the CWT values along the path were 30-60 mg·m–3. Long-range transport was also observed in autumn from southeastern Xinjiang along a northwesterly pathway, and in winter from the Tibetan Plateau along a westerly pathway. In summer, the potential source regions of Chengdu were smaller than those in other seasons, and no long-range transport pathway was observed. Results of PSCF and CWT indicated that regions in Qinghai and Tibet contributed to PM2.5 pollution in Chengdu as well, and their CWT values increased to above 30 mg·m–3 in winter.