An investigation on the physical, chemical and ecotoxicological characteristics of particulate matter emitted from light-duty vehicles

Chemical characteristics of fine tire wear particles generated on a tire simulator

Tire wear is one of the major sources of traffic-related particle emissions, however, laboratory data on the components of tire wear particles (TWPs) is scarce. In this study, ten brands of tires, including two types and four-speed grades, were chosen for wear tests using a tire simulator in a closed chamber. The chemical components of PM2.5 were characterized in detail, including inorganic elements, water-soluble ions (WSIs), organic carbon (OC), elemental carbon (EC), and polycyclic aromatic hydrocarbons (PAHs). Inorganic elements, WSIs, OC, and EC accounted for 8.7 ± 2.1%, 3.1 ± 0.7%, 44.0 ± 0.9%, and 9.6 ± 2.3% of the mass of PM2.5, respectively. The OC/EC ratio ranged from 2.8 to 7.6. The inorganic elements were dominated by Si and Zn. The primary ions were SO42- and NO3-, and TWPs were proven to be acidic by applying an ionic balance. The total PAHs content was 113 ± 45.0 μg g-1, with pyrene being dominant. In addition, the relationship between the chemical components and tire parameters was analyzed. Inorganic elements and WSIs in TWPs were more abundant in all-season tires than those in winter tires, whereas the content of PAHs was the opposite. The mass fractions of OC, Si, and Al in the TWPs all showed increasing trends with increasing tire speed grade, but the PAHs levels showed a decreasing trend. Ultimately, to provide more data for further research, a TWPs source profile was constructed considering the tire weighting factor.

Laboratory and on-road testing for brake wear particle emissions: a review

Brake wear emission is a significant contributor to vehicle-related particulate matter, especially in areas with high traffic density and braking frequency. Only recently, non-exhaust emissions from car brake wear have been regulated under Euro 7 regulation, which introduces emission limits for both brake and tires. It also introduces a standard brake particle assessment procedure which includes sampling procedure and measurement techniques defined in the Global Technical Regulation on brakes from light-duty vehicles up to 3.5 t. Over the years, various experimental setups have been tried leading to non-comparable results. The brake wear particle emissions, expressed as emission factors, are mostly estimated as particle mass or particle number and described using different units (e.g., mg/stop brake, mg/km brake; particle number/cm3) making the comparison between studies very difficult. The aim of the present literature review is to present the state-of-the-art of different experimental methods tuned for assessing brake wear emissions, including electric vehicles. The experiments are carried in close, semi-closed, and open systems, and depending on the experimental design, different sampling methods are applied to reduce particle transport loss and guarantee the efficiency of the particle sampling. Driving condition (e.g., speed and applied pressure), formulation of brake materials, and friction temperature have been found to strongly affect the emission characteristics of brake particles, and this needs to be considered when designing study procedures. The findings reported in this review can be beneficial to policy makers and researchers.

Emission factors for a biofuel impacted fleet in south America's largest metropolitan area

The Metropolitan Area of São Paulo (MASP) is among the largest urban areas in the Southern Hemisphere. Vehicular emissions are of great concern in metropolitan areas and MASP is unique due to the use of biofuels on a large scale (sugar-cane ethanol and biodiesel). In this work, tunnel measurements were employed to assess vehicle emissions and to calculate emission factors (EFs) for heavy-duty and light-duty vehicles (HDVs and LDVs). The EFs were determined for particulate matter (PM) and its chemical compounds. The EFs obtained for 2018 were compared with previous tunnel experiments performed in the same area. An overall trend of reduction of fine and coarse PM, organic carbon (OC), and elemental carbon (EC) EFs for both LDVs and HDVs was observed if compared to those observed in past years, suggesting the effectiveness of vehicular emissions control policies implemented in Brazil. A predominance of Fe, Cu, Al, and Ba metals emission was observed for the LDV fleet in the fine fraction. Cu presented higher emissions than two decades ago, which was associated with the increased use of ethanol fuel in the region. For HDVs, Zn and Pb were mostly emitted in the fine mode and were linked with lubricating oil emissions from diesel vehicles. A predominance in the emission of three- and four-ring polycyclic aromatic hydrocarbons (PAHs) for HDVs and five-ring PAHs for LDVs agreed with what was observed in previous studies. The use of biofuels may explain the lower PAH emissions for LDVs (including carcinogenic BaP) compared to those observed in other countries. The tendency observed was that LDVs emit higher amounts of carcinogenic species. The use of these real EFs in air quality modeling resulted in more accurate simulations of PM concentrations, showing the importance of updating data with real-world measurements.

Phytoremediation as a potential technique for vehicle hazardous pollutants around highways

With the synchronous development of highway construction and the urban economy, automobiles have entered thousands of households as essential means of transportation. This paper reviews the latest research progress in using phytoremediation technology to remediate the environmental pollution caused by automobile exhaust in recent years, including the prospects for stereoscopic forestry. Currently, most automobiles on the global market are internal combustion vehicles using fossil energy sources as the primary fuel, such as gasoline, diesel, and liquid or compressed natural gas. The composition of vehicle exhaust is relatively complex. When it enters the atmosphere, it is prone to a series of chemical reactions to generate various secondary pollutants, which are very harmful to human beings, plants, animals, and the eco-environment. Despite improving the automobile fuel quality and installing exhaust gas purification devices, helping to reduce air pollution, the treatment costs of these approaches are expensive and cannot achieve zero emissions of automobile exhaust pollutants. The purification of vehicle exhaust by plants is a crucial way to remediate the environmental pollution caused by automobile exhaust and improve the environment along the highway by utilizing the ecosystem's self-regulating ability. Therefore, it has become a global trend to use phytoremediation technology to restore the automobile exhaust pollution. Now, there is no scientific report or systematic review about how plants absorb vehicle pollutants. The screening and configuration of suitable plant species is the most crucial aspect of successful phytoremediation. The mechanisms of plant adsorption, metabolism, and detoxification are reviewed in this paper to address the problem of automobile exhaust pollution.

Chemical characteristics analysis of automobile exhaust particles and the method for evaluating its ecological effect

Automobile exhaust has become the main source of atmospheric particulate matter with the increase in the number of automobiles. Automobile exhaust particles (AEPs) discharged into the atmosphere can enter the aquatic environment through atmospheric deposition, rain runoff, leaching, drainage water and urban sewage and further affect aquatic organisms. However, there is no comprehensive theory and method to evaluate the ecological effects of AEPs on aquatic environment. The new European driving cycle (NEDC) and the world harmonized light-duty test cycle (WLTC) were used to analyze the ecotoxicity of AEPs. The SUV gasoline, SUV hybrid and sedan gasoline under WLTC were used for further analysis. The chemical characteristics of AEPs were analyzed, and the ecotoxicity of AEPs on aquatic organisms was studied with Vibrio fischeri and Danio rerio as test organisms. The ecological effect of AEPs was studied through species sensitivity distribution based on interspecies correlation estimation (ICE) models. The results showed that (ⅰ) polycyclic aromatic hydrocarbons (PAHs) were the main organic substances in AEPs. The total concentrations of PAHs in AEPs measured under the NEDC and WLTC were 237.4 and 159.8 mg kg^-1, respectively, and the EC₅₀ values for V. fischeri measured under the NEDC and WLTC were 42.02 and 47.05 mg L^-1, respectively. (ⅱ) Total heavy metal concentrations in AEPs from SUV gasoline, SUV hybrid, and sedan gasoline were 197.52, 104.86, and 89.68 mg kg^-1, respectively, and the LC₅₀ values for D. rerio were 3.22, 4.46 and 5.62 mg L^-1. Cu and Mn were the main toxic heavy metals in AEPs. (ⅲ) The PNEC values of AEPs from SUV gasoline, SUV hybrid and sedan gasoline were 0.57, 0.83 and 1.02 mg L^-1, respectively. This exploratory study can provide technical information on water ecological safety assessment for determining the impact of AEPs on the surface water environment and for further improving automobile exhaust emission standards.

Effect of treadwear grade on the generation of tire PM emissions in laboratory and real-world driving conditions

Tires generally wear out due to the friction between the tire and the road surface. Minimizing tire wear could reduce the non-exhaust particulate matter (PM) emissions from tires. Typically, tire treadwear grade can be used as an indicator of PM emissions from tires. Tires that wear out quickly will produce higher PM emissions than more durable tires. In this study, the effect of treadwear grade on the generation of tire PM emissions was investigated through laboratory and on-road driving measurements. In the laboratory measurements, a tire wear simulator installed in an enclosed chamber was used to eliminate artifacts caused by interfering particles during the generation and measurement of tire wear particles. For realistic on-road driving measurements, a mobile sampling vehicle was employed to sample road dust. The road dust was chemically analyzed using pyrolysis gas chromatography-mass spectrometry (GC-MS) to characterize the tire-road wear particles. Both measurements showed that the higher treadwear grade generated lower tire PM emissions due to the high strength of the rubber, except for the UTQG 700 tire. The UTQG 700 tire, which had the highest treadwear grade, produced higher PM emissions than the UTQG 350 and 500 tires because it readily formed the fine particles due to lamellar peeling rather than tearing or curling of tire treads. Notably, tire nanoparticles were observed in laboratory measurements due to the volatilization and nucleation of the sulphur (S) and zinc (Zn) compounds in the tire tread due to the frictional heat between the tire and paved road surface.

Polycyclic Aromatic Hydrocarbons in Araucaria heterophylla Needles in Urban Areas: Evaluation of Sources and Road Characteristics

Araucaria heterophylla needles were collected in urban areas of the city of Quito, Ecuador, to analyze the relationship between the concentration of polycyclic aromatic hydrocarbons (PAHs) with different emission sources and road characteristics. The PAHs were analyzed by high-performance liquid chromatography (HPLC) and included naphthalene (Naph), benzo[a]anthracene (BaA), chrysene (Chry), and benzo[a]pyrene (BaP), which are related to the sources considered in this work. The results indicated that some streets with moderate and low traffic intensity had higher total concentrations of PAHs than streets with high traffic intensity, showing the importance of non-traffic related emission sources and road characteristics on PAH emissions. All the studied PAHs were associated with traffic emissions, although Naph and BaP were more associated with acceleration and braking activities, while BaA and Chry also seemed to come from restaurant emissions. The presence of gas stations was also important in the emission of PAHs. Road capacity seems to have a higher effect on pollutant emission than road gradient and urban forms. The outcomes of this study are expected to facilitate the diagnostics of the concentration of PAHs in urban areas, which contribute to the design of strategies for the mitigation of pollution by PAHs in urban environment.

Assessment of the effects of seasonality on the ecotoxicity induced by the particulate matter using the animal model Caenorhabditis elegans

The present work aimed to establish potential changes in the ecotoxicological effects on C. elegans induced by the exposure of coarse (PM₁₀) and fine (PM_2.5) particulate matter collected during dry and rainy periods. We also analyzed the probable influence on the change of a city's activities as the mega-events result in air quality. The element levels evaluation was performed on PM, on the solutions of exposure, and C. elegans after exposure. Biochemical essays were performed to evaluate damage to C. elegans. The results showed that infrastructure works increased the levels of pollutants, generating increases in the concentrations of PM_2.5 and PM₁₀. The biochemical results suggested effects mediated by different mechanisms, where PM_2.5 induced an increase in antioxidant capacity with activation of the defense system and lipoperoxidation. Results suggest that PM₁₀ reduces the antioxidant capacity and activates the glutathione S-transferase activity enzymatic action, but also induces lipoperoxidation in all groups of animals exposed to samples collected during the dry period of 2016. Individuals exposed to PM_2.5 in 2017 wet and dry periods and PM₁₀ in 2016 and 2017 dry periods shown a decrease in size compared to controls, while for fertility data, there was a decrease only in individuals exposed to PM_2.5 in the periods that the highest levels of PM concentration. We conclude that despite the positive issues linked to the hosting of mega-events, their infrastructure requirements can compromise air quality and bring damage related to lipoperoxidation and physiological changes in the life cycle of biological systems, such as what happened to C. elegans exposed to tested extracts. Also, rainy events reduced the presence of these pollutants, washing the atmosphere.

Ecotoxicity testing of airborne particulate matter-comparison of sample preparation techniques for the Vibrio fischeri assay

The bioassay based on the bioluminescence inhibition of the marine bacterium Vibrio fischeri has been the most widely used test for the assessment of airborne particulate matter ecotoxicity. Most studies available use an extract of the solid sample, either made with water or organic solvents. As an alternative, a whole-aerosol test is also available where test bacteria are in actual contact with contaminated particles. In our study, different extraction procedures were compared to this direct contact test based on the V. fischeri assay and analytical measurements. The lowest PAH content and the highest EC₅₀ were determined in water extract, while the highest PAH amount and lowest EC₅₀ were measured in dichloromethane, hexane, and dimethyl-sulphoxide extracts. EC₅₀ of the direct contact test was comparable to that of the methanol extract. Our results suggest that the sensitivity of the direct contact test equals to that of extraction procedures using organic solvents, moreover, it is mimicking an environmentally realistic exposure route.

Environmental Risk Assessment of Vehicle Exhaust Particles on Aquatic Organisms of Different Trophic Levels

Vehicle emission particles (VEPs) represent a significant part of air pollution in urban areas. However, the toxicity of this category of particles in different aquatic organisms is still unexplored. This work aimed to extend the understanding of the toxicity of the vehicle exhaust particles in two species of marine diatomic microalgae, the planktonic crustacean Artemia salina, and the sea urchin Strongylocentrotus intermedius. These aquatic species were applied for the first time in the risk assessment of VEPs. Our results demonstrated that the samples obtained from diesel-powered vehicles completely prevented egg fertilization of the sea urchin S. intermedius and caused pronounced membrane depolarization in the cells of both tested microalgae species at concentrations between 10 and 100 mg/L. The sample with the highest proportion of submicron particles and the highest content of polycyclic aromatic hydrocarbons (PAHs) had the highest growth rate inhibition in both microalgae species and caused high toxicity to the crustacean. The toxicity level of the other samples varied among the species. We can conclude that metal content and the difference in the concentrations of PAHs by itself did not directly reflect the toxic level of VEPs, but the combination of both a high number of submicron particles and high PAH concentrations had the highest toxic effect on all the tested species.

Chemical characterization of PM2.5 emitted from China IV and China V light-duty vehicles in China

This study reported the emission factors (EFs) and detailed chemical compositions of PM_2.5 collected from China IV and China V light-duty vehicles (LDVs) through dynamometer test. The China IV LDVs containing 4 gasoline vehicles (GVs) and 4 natural gas vehicles (NGVs) had port fuel injection (PFI) engines, while the China V LDVs included 2 GVs with PFI engines and 2 GVs with gasoline direct injection (GDI) engines. The average EFs of PM_2.5 were 1.90 ± 0.70 mg km^-1, 1.44 ± 0.29 mg km^-1, and 0.56 ± 0.05 mg km^-1 for China IV GVs, China IV NGVs, and China V GVs, respectively. PM_2.5 profiles of LDVs were characterized by abundant carbon species (60.59-68.58%) with low amounts of water soluble ions (WSIs, 6.96-16.37%) and elements (5.20-7.53%). In general, the EFs of PM_2.5 constituents including organic carbon (OC), elemental carbon (EC), WSIs, and elements were reduced obviously by strengthening emission standards from China IV to China V. While the contributions of most WSIs and elements to PM_2.5 increased as vehicle technology improved. Furthermore, the EFs of PM_2.5 components from China IV LDVs also decreased when shifting fuels from gasoline to natural gas. While the fractions of OC, WSIs and most elements in PM_2.5 increased due to the highest reduction rate of EC mass. For China V LDVs, GDI vehicles emitted less OC but more EC compared to PFI vehicles, and the EFs of most WSIs and elements also increased. Overall, GDI vehicles exhibited lower fractions OC and WSIs but higher contents of EC and elements in PM_2.5. Besides, PM_2.5 and its chemical species were heavily dependent on vehicle's driving patterns. The average EFs of PM_2.5 components under aggressive driving pattern increased significantly compared to those under moderate driving pattern.

Mathematical Modeling Approaches for Assessing the Joint Toxicity of Chemical Mixtures Based on Luminescent Bacteria: A Systematic Review

Developments in industrial applications inevitably accelerate the discharge of enormous substances into the environment, whereas multi-component mixtures commonly cause joint toxicity which is distinct from the simple sum of independent effect. Thus, ecotoxicological assessment, by luminescent bioassays has recently brought increasing attention to overcome the environmental risks. Based on the above viewpoint, this review included a brief introduction to the occurrence and characteristics of toxic bioassay based on the luminescent bacteria. In order to assess the environmental risk of mixtures, a series of models for the prediction of the joint effect of multi-component mixtures have been summarized and discussed in-depth. Among them, Quantitative Structure-Activity Relationship (QSAR) method which was widely applied in silico has been described in detail. Furthermore, the reported potential mechanisms of joint toxicity on the luminescent bacteria were also overviewed, including the Trojan-horse type mechanism, funnel hypothesis, and fishing hypothesis. The future perspectives toward the development and application of toxicity assessment based on luminescent bacteria were proposed.

Vehicle emissions in a middle-sized city of China: Current status and future trends

Vehicle emissions are regarded as an important contributor to urban air pollution in China and most previous studies focused on megacities. However, the vehicle pollution in middle-sized cities becomes more severe due to the increasing vehicle population (VP) and lagged control policy. This study takes Langfang, a typical middle-sized city bordered by two megacities (Beijing and Tianjin), as the target domain to investigate vehicle emissions. The speed correction curves (SCC) are introduced to improve the vehicle emission factors (EF) simulation in official technical guidelines on emission inventory (GEI). A multi-year vehicle emission inventory (from 2011 to 2025) is developed in Langfang. From 2011 to 2017, the total vehicle emissions in Langfang decrease for carbon monoxide (CO), but increase for volatile organic compounds (VOCs), nitrogen oxides (NO_x), and inhalable particles (PM₁₀), respectively. From 2018 to 2025, the emissions would increase more rapidly in Langfang than in Beijing and Tianjin, indicating the middle-sized cities may become a significant contributor to air pollution in China. Four possible control policies, including VP constrained (VPC), public transportation promotion (PTP), new energy vehicles promotion (NEP), and freight transportation structure optimization (FTO) are evaluated. The most significant emissions reductions are observed under the FTO for CO, NO_x, and PM₁₀, and under the VPC for VOCs. The spatial distributions of vehicle emissions show a high order of heterogeneity, indicating that local conditions should be considered in policy formulation in addition to national consistency. More comprehensive policies should be implemented to mitigate the vehicle pollution in middle-sized cities.

Correlation of Oxidative Potential with Ecotoxicological and Cytotoxicological Potential of PM10 at an Urban Background Site in Italy

Exposure to atmospheric particulate matter (PM) has detrimental effects on health, but specific mechanisms of toxicity are still not fully understood. In recent years, there has been a growing evidence that oxidative stress is an important mechanism of toxicity; however, when acellular oxidative potential (OP) data are correlated with the outcomes of in vitro (or in vivo) toxicological tests there are contrasting results. In this work, an analysis of PM10 health effect indicators was done, using the acellular Dithiotreitol (DTT) assay to retrieve OPDTT, the Microtox® test on Vibrio fischeri bacterium to assess the ecotoxicological potential, and the in vitro MTT assay on the human cell line A549 to estimate the cytotoxicological potential. The objective was to evaluate the correlation among acellular OPDTT and the results from toxicological and ecotoxicological bioassays and how these health-related indicators are correlated with atmospheric PM10 concentrations collected at an urban background site in Southern Italy. Results indicated that both bioassays showed time-dependent and dose-dependent outcomes. Some samples presented significant ecotoxic and cytotoxic response and the correlation with PM10 concentration was limited suggesting that these health endpoints depend on PM10 chemical composition and not only on exposure concentrations. OPDTT showed a statistically significant correlation with PM10 concentrations. MTT and Microtox outcomes were not correlated suggesting that the two toxicological indicators are sensitive to different physical-chemical properties of PM10. Intrinsic oxidative potential OPDTTM (DTT activity normalised with PM10 mass) was correlated with mortality observed with MTT test (normalized with PM10 mass); however, it was not correlated with Microtox outcomes.

Effects of air/fuel ratio and ozone aging on physicochemical properties and oxidative potential of soot particles

Fuel combustion conditions and atmospheric aging processes can affect the physicochemical properties of soot particles, which further change the oxidative potential (OP) of soot. In this study, we generated two soot samples under higher and lower air/fuel ratio (A/F) conditions, and further treated them with ozone (O₃) at a level similar to that in the polluted atmosphere. The physicochemical properties and OP values (measured by dithiothreitol (DTT) assay, OP^DTT) of fresh and ozonised soot samples were compared to investigate the influences of A/F and O₃ aging. Both A/F and O₃ aging significantly affected soot physicochemical properties and OP^DTT values. Lower A/F was favourable for generating soot particles containing more polycyclic aromatic hydrocarbon (PAH), water-soluble organic carbon (WSOC), and light-absorbing organics, but fewer oxygen-containing groups. After O₃ aging, a decline in PAHs and increase in oxygen-containing groups and WSOC were observed in both aged soot samples. In addition, both lower A/F and O₃ aging enhanced soot OP^DTT values. Soot generated under lower A/F was more sensitive to O₃ aging, after which there was a significantly greater change in physicochemical characteristics, in turn contributing substantially to the greater OP increase observed in low-A/F soot.

Using an innovative flag element ratio approach to tracking potential sources of heavy metals on urban road surfaces

Heavy metals deposited on urban road surfaces can be washed-off by stormwater runoff, undermining stormwater reuse safety due to their high toxicity to ecological and human health. Heavy metals on urban road surfaces come from diverse sources and tracking these sources is essential to effectively manage stormwater and hence its reuse safety. This research study developed an innovative approach to tracking sources of heavy metals using data collected in Shenzhen, China. This approach developed was based on a "flag element ratio" theory, where each source generally corresponds to a specific ratio of targeted pollutants to the flag element. It is noted that Cr, Cu, Pb, Ni, and Zn on urban roads were 19.05 mg/kg to 152.01 mg/kg, 25.66 mg/kg to 310.75 mg/kg, 15.61 mg/kg to 220.35 mg/kg, 10.65 mg/kg to 100.28 mg/kg, and 138.14 mg/kg to 1047.05 mg/kg, respectively. Gasoline emission was the main source for Cr, Ni and Pb, while braking wear and tyre wear were the major sources of Cu and Zn, respectively. Furthermore, the rankings of sources of each heavy metal in terms of their contributions were obtained by using this approach. Vehicle exhaust was found as the main contributor for all the heavy metals on urban road surfaces. This highlighted that vehicle exhaust should be seriously considered in terms of controlling heavy metal pollution on urban road surfaces and hence resulting urban road stormwater runoff.

In vitro cellular toxicity induced by extractable organic fractions of particles exhausted from urban combustion sources - Role of PAHs

The bioactivity of the extractable organic matter (EOM) of particulate matter (PM) exhausted from major urban combustion sources, including residential heating installations (wood-burning fireplace and oil-fired boiler) and vehicular exhaust from gasoline and diesel cars), was investigated in vitro by employing multiple complementary cellular and bacterial assays. Cytotoxic responses were investigated by applying the MTT ((3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide)) bioassay and the lactate dehydrogenase (LDH) release bioassay on human lung cells (MRC-5). Sister Chromatids Exchange (SCE) genotoxicity was measured on human peripheral lymphocytes. Lipid peroxidation potential via reactive oxygen species (ROS) was evaluated on E. coli bacterial cells by measuring the malondialdehyde (MDA) end product. Furthermore, the DNA damage induced by the organic PM fractions was evaluated by the reporter (β-galactosidase) gene expression assay in the bacterial cells, and, by examining the fragmentation of chromosomal DNA on agarose gel electrophoresis. The correlations between the source PM-induced biological endpoints and the PM content in polycyclic aromatic hydrocarbons (PAHs), as typical molecular markers of combustion, were investigated. Fireplace wood smoke particles exhibited by far the highest content in total and carcinogenic PAHs followed by oil boilers, diesel and gasoline emissions. However, in all bioassays, the total EOM-induced toxicity, normalized to PM mass, was highest for diesel cars equipped with Diesel Particle Filter (DPF). No correlation between the toxicological endpoints and the PAHs content was observed suggesting that cytotoxicity and genotoxicity are probably driven by other extractable organic compounds than the commonly measured unsubstituted PAHs. Clearly, further research is needed to elucidate the role of PAHs in the biological effects induced by both, combustion emissions, and ambient air particles.

Characteristics of Tire Wear Particles Generated by a Tire Simulator under Various Driving Conditions

Physicochemical properties of pure tire wear particles (TWPs) were investigated in a laboratory. A tire simulator installed in an enclosing chamber was employed to eliminate artifacts caused by interfering particles during the generation and measurement of TWPs. TWP particulate matter (PM_2.5 and PM₁₀) was correlated with tire speed ( r > 0.94) and load ( r > 0.99). Their mass size distributions showed that TWP mode diameters ranged between 3 and 4 μm (unimodal). Tire wear caused by slip events resulted in an increase in the number concentration (ca. 8.4 × 10⁵ cm^-3) of particles (mainly ultrafine particles (UFPs)) at low PM_2.5 and PM₁₀ values (1 and 2 μg m^-3, respectively). During braking events, UFPs were emitted at an early stage, with an increase in number concentration (up to 1.1 × 10⁷ cm^-3); a high mass concentration (3.6 mg m^-3) was observed at a later stage via the coagulation of early emitted UFPs and condensation. On the basis of morphology and elemental composition, TWPs generally had elongated (micrometer-scale) and round/irregular (submicrometer-scale) shapes and they were classified into C/Si-rich, heavy metal-containing, S-containing, and mineral-containing particles. This study determined that TWP emissions can vary with changes in driving condition.

Airborne particulate matter biotoxicity estimated by chemometric analysis on bacterial luminescence data

In this work, PM₁₀ samples previously subjected to thorough chemical speciation and receptor modelling, have been investigated for their bio-toxicity using an inhibition test based on bacterial luminescence modulation when in contact with airborne particulate samples. The variation of light emission intensity from a luminescent bacteria strain, the Photobacterium phosphoreum, is proposed as an efficient proxy for the quantification of bio-toxic effects induced by airborne particulate matter. PM₁₀ samples characterized by definite levels of pollutants from the pertaining air shed were found to induce a decrease in the bacterial bioluminescence intensity, expressed as percentage of Inhibition Ratio (IR%). This behaviour suggests the decay of this energy-consuming activity because of a toxic effect. Cluster analysis on chemical composition and IR% data provides evidence of a statistically significant association between the adverse effects on living cells and the range of specific chemical species in PM₁₀.

Vibrio fischeri bioluminescence inhibition assay for ecotoxicity assessment: A review

Vibrio fischeri bioluminescence inhibition bioassay (VFBIA) has been widely applied for the monitoring of toxicity on account of multiple advantages encompassing shorter test duration, sensitive, cost-effective and ease of operation. Moreover, this bioassay found to be equally applicable to all types of matrices (organic & inorganic compounds, metals, wastewater, river water, sewage sludge, landfill leachate, herbicides, treated wastewater etc.) for toxicity monitoring. This review highlights the apparent significance of Vibrio fischeri bioluminescence inhibition assay for ecotoxicological screening and evaluation of diverse chemical substances toxicity profile. The biochemical and genetic basis of the bioluminescence assay and its regulatory mechanism have been concisely discussed. The basic test protocol with ongoing improvements, widespread applications, typical advantages and probable limitations of the assay have been overviewed. The sensitivity of VFBIA and toxicity bioassays has also been compared.

Eco- and genotoxicity profiling of a rapeseed biodiesel using a battery of bioassays

Biodiesel is considered an important renewable energy source but still there is some controversy about its environmental toxicity, especially to aquatic life. In our study, the toxicity of water soluble fraction of biodiesel was evaluated in relatively low concentrations using a battery of bioassays: Vibrio fischeri bioluminescence inhibition, Sinapis alba root growth inhibition, Daphnia magna immobilization, boar semen live/dead ratio and DNA fragmentation and Unio pictorum micronucleus test. While the S. alba test indicated nutritive (stimulating) effect of the sample, the biodiesel exerted toxic effect in the aquatic tests. D. magna was the most sensitive with EC₅₀ value of 0.0226%. For genotoxicity assessment, the mussel micronucleus test (MNT) was applied, detecting considerable genotoxic potential of the biodiesel sample: it elucidated micronuclei formation already at low concentration of 3.3%. Although this test has never been employed in biodiesel eco/genotoxicity assessments, it seems a promising tool, based on its appropriate sensitivity, and representativity.

Eco-toxicological bioassay of atmospheric fine particulate matter (PM2.5) with Photobacterium Phosphoreum T3

A bioluminescent bacterium, Photobacterium phosphoreum T3 (PPT3), was used as a bio-indicator for the atmospheric fine particulate matter (PM2.5) to determine the eco-toxicity of PM2.5. The PM2.5 contains toxic chemicals, which reduce light output. The PM2.5 samples were collected in the period from March 2014 to January 2015 in Nanjing and analyzed for the chemical composition versus their eco-toxicity. The eco-toxicological responses of each toxicant were detected in PM2.5 samples with PPT3. The dose-response curves obtained were verified using the Weibull fitting function. According to the measured EC50 values (EC50, the concentration of a toxicant that inhibits 50% of the bioluminescence), the toxicity sequence was: B[a]P>hexa-PCB>tetra-PCB>tri-PCB>Pb(2+)>DEHP>Cu(2+)>DBP>BDE209>Zn(2+)>DMP>DEP, where B[a]P is benzo(a)pyrene, PCB is polychlorinated biphenyl, DEHP is diethylhexyl phthalate, DBP is dibutyl phthalate, BDE209 is decabromodiphenyl ether, DMP is dimethyl phthalate, and DEP is diethyl phthalate. All the PM2.5 samples analyzed proved to be weak toxic for PPT3. The toxicity of PM2.5 was assessed by the dose-addition of organic species and heavy metallic elements existing in PM2.5 with PPT3. The bioluminescence test showed that the metals and organics detected in PM2.5 promoted PM2.5 toxicity. The total detectable organics (denoted by ΣOrs) exhibited slightly higher toxicity than the total metals (denoted by ΣMs). In contrast, the sum of water-soluble ions (denoted by ΣIons) was beneficial to PPT3. The PM2.5 toxicity increased as the PM2.5 trapped more organics or metallic elements from the industrial or densely populated urban areas, where the PM2.5 had a high inhibition rate of bioluminescence for PPT3 in contrast to the residential PM2.5 samples, where the minimum inhibition rate was observed. The toxicity of PM2.5 samples varied with the mass concentrations, chemical constituents, and sampling locations. The chemicals in PM2.5, especially organic species and metallic elements, affected its eco-toxicity. These data provided good understanding of the atmospheric PM2.5 pollution in the large portion of the East China.

Characterization of the chemical composition of PM2.5 emitted from on-road China III and China IV diesel trucks in Beijing, China

The composition of diesel exhaust fine particulate matter (PM2.5) is of growing interest because of its impacts on health and climatic factors and its application in source apportionment and aerosol modeling. We characterized the detailed chemical composition of the PM2.5, including the organic carbon (OC), elemental carbon (EC), water-soluble ions (WSIs), and elemental contents, emitted from China III and China IV diesel trucks (nine each) based on real-world measurements in Beijing using a portable emissions measurement system (PEMS). Carbonaceous compounds were the dominant components (totaling approximately 87%) of the PM2.5, similar to the results (greater than 80% of the PM2.5) of our previous study of on-road China III diesel trucks. In general, the amounts of individual component groups (carbonaceous compounds, WSIs, and elements) and PM2.5 emissions for China IV diesel trucks were lower than those of China III diesel trucks of the same size, except for the WSIs and elements for the light- and medium-duty diesel trucks. The EC/OC mass ratios were strongly dependent on the emission standards, and the ratios of China IV diesel trucks were higher than those of China III diesel trucks of the same size. The chemical species in the PM2.5 were significantly affected by the driving conditions. Overall, the emission factors (EFs) of the PM2.5 and OC under non-highway (NHW) driving conditions were higher than those under highway (HW) driving conditions, and the EC/OC mass ratios presented an increasing trend, with decreasing OC/PM2.5 and increasing EC/PM2.5 from NHW to HW driving conditions; similar trends were reported in our previous study. In addition, Pearson's correlation coefficients among the PM2.5 species were analyzed to determine the relationships among the various chemical components.

Bioassay based luminescent bacteria: interferences, improvements, and applications

Due to the merits of being time-saving, cost effective and simple operation, the luminescent bacteria toxicity assay (LBTA) has been widely used for environmental pollution monitoring. Based on numerous studies since 2007, this critical review aims to give an overview on the mechanisms, developments and applications of LBTA. Firstly, based on the introduction of the mechanisms of LBTA, this review shows the interferences from the characteristics of testing samples (such as inorganic nutrients, color, turbidity) and summarizes the improvements on pretreatment method, test methods and test systems in recent years. Regarding the factors that affect the toxicity prediction of single chemicals, the correlation between the toxicity index expressed as median effective concentration (EC50) and characters (such as Kow, the alkyl chain length, the anion and the cation) of known chemicals, especially the emerging ionic liquids (ILs), were given an in-depth discussion. The models for predicting the joint effect of mixtures to luminescent bacteria were also presented. For the factors that affect the toxicity of actual waters, the correlation of toxicity of actual samples to luminescent bacteria and their conventional indexes were discussed. Comparing the sensitivity of the LBTA with other bioassays could indicate the feasibility of the LBTA applied on specific samples. The summary on the application of LBTA to environmental samples has been made to find the future research direction.

Ecotoxicological characterisation of exhaust particulates from diesel-powered light-duty vehicles

Diesel exhaust is one of the major sources of fine and ultrafine particulate matter in urban air. Toxicity of diesel-powered engine emissions has been quite widely assessed, however, much less information is available on their ecotoxicity. In our study the kinetic version of the Vibrio fischeri bioluminescence inhibition bioassay, based on the ISO 21338:2010 standard, was used to characterise the ecotoxicity of diesel-powered cars. The method is sensitive enough to test the ecotoxic effect of the emission of individual vehicles. In general, significant positive correlation was found between ecotoxicity (expressed as Toxic Unit /TU/values) and total carbon (TC) as well as between TU and polycyclic aromatic hydrocarbon (PAH) concentrations.

Ecotoxicity and genotoxicity assessment of exhaust particulates from diesel-powered buses

Diesel exhaust is one of the major sources of fine and ultra-fine particulate matter in urban air. Toxicity of diesel-powered engine emissions has been quite widely assessed; however, much less information is available on their ecotoxicity. In our study, the kinetic version of the Vibrio fischeri bioluminescence inhibition bioassay based on the ISO 21338:2010 standard was used to characterise the ecotoxicity of diesel-powered buses. It is a direct contact test in which solid samples are tested in suspension and test organisms are in direct contact with toxic particles. The age of the selected buses fell into a wide range; the oldest one was produced in 1987. Diesel engines of different emission standards (Euro0-Euro4) were included. Measured EC50 values of Euro0-Euro1 engine emissions fell into the same range, 1.24-0.96 μg ml(-1), respectively. On the contrary, emission of Euro4 vehicle proved to be non-toxic. Genotoxic potential of the samples was also estimated, using the colorimetric SOS-chromotest™. Genotoxicity was detected also for Euro0 and Euro1 buses, showing correlation with the ecotoxic potential. The fact that the particulates from Euro4 vehicles did not show ecotoxic/genotoxic effect implies that replacing old Euro1 and Euro2 buses can be a highly effective solution for reducing environmental hazard of automotive emissions. The whole-aerosol testing method is a cheap alternative that can be used in engine developments and emission control.

In vitro tests to assess toxic effects of airborne PM(10) samples. Correlation with metals and chlorinated dioxins and furans

Inhalation is an important exposure pathway to airborne pollutants such as heavy metals, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and particulate matter. Chronic exposure to those chemicals, which form part of complex environmental mixtures, may mean important human health risks. In the present study, the suitability of different in vitro tests to evaluate the toxic effects of air PM(10) pollutants is investigated. In addition, it is also assessed how to distinguish the contribution of chemical pollutants to toxicity. Sixty-three air samples were collected in various areas of Catalonia (Spain), and the levels of ecotoxicity, cytotoxicity and genotoxicity were evaluated. Aqueous acidic extractions of quartz fiber filters, where PM(10) had been retained, were performed. The photo-luminescent bacteria Vibrio fischeri (Microtox®) bioassay was performed to assess ecotoxicity. Moreover, MTT and Comet Assays, both using human lung epithelial cells A549 as target cells, were applied to assess the cytotoxicity and genotoxicity of air samples, respectively. The results show that Microtox® is an excellent screening test to perform a first evaluation of air quality, as it presented a significant correlation with chemical contaminants, contrasting with MTT Assay. Although none of the samples exhibited genotoxicity, a high correlation was found between this in vitro test and carcinogenic agents. Urban samples from traffic-impacted areas would be significantly more toxic. Finally, environmental temperature was identified as a key parameter, as higher values of ecotoxicity were found in winter.

Biomonitors of urban air pollution: Magnetic studies and SEM observations of corticolous foliose and microfoliose lichens and their suitability for magnetic monitoring

This study explored the suitability of available lichen species as air pollution biomonitors and assessed their potential for magnetic monitoring in cities. Several lichens on tree bark were collected in urban and industrial sites from Tandil city, as well as control sites. The results showed that magnetite-like minerals were the main magnetic carriers in all sites and samples. However, the concentration varied between clean and polluted sites. In addition, magnetic-grain size-distribution showed clear differences between sites. Observations by scanning electron microscopy showed different particles in a variety of shapes and grain sizes; moreover, the presence of iron oxides and several toxic elements was detected by energy dispersive spectroscopy analysis. Although eleven lichen species were identified that appeared suitable for use as air-pollution monitors, three of them, Parmotrema pilosum, Punctelia hipoleucites and Dirinaria picta, occurred more frequently in the area, thus constituting appropriate species for future monitoring in the study area.

Direct contact test for estimating the ecotoxicity of aerosol samples

Atmospheric particulate matter with aerodynamic diameter less than 10 μm (PM10) and 2.5 μm (PM2.5) is now identified as one of the most dangerous pollutants on human health by the EU new directive on air quality (2008/50/CE). Although these primary pollutants are monitored in cities, little information is available on their ecotoxicity. In this paper a 'whole-aerosol' testing protocol is suggested based on the kinetic version of the Vibrio fischeri bioluminescence inhibition test.