International audience | We report lead (Pb) analyses in juvenile (n = 37; mean length = 24.7 ± 2.3 cm) and adult (n = 16; mean length = 52.3 ± 9.3 cm) Centroscymnus coelolepis Mediterranean deep-sea sharks that are compared to Pb content in bathy-demersal, pelagic and shallow coastal sharks. Median Pb concentrations of C. coelolepis muscle (0.009-0.056 wet ppm) and liver (0.023-0.061 wet ppm) are among the lowest encountered in shark records. Stable Pb isotope imprints in adult C. coelolepis muscles highlight that most of Pb in C. coelolepis is from human origin. Lead isotopes reveal the persistence of gasoline Pb emitted in the 1970s in low-turnover adult shark's muscle while associated liver imprints are in equilibrium with recent pollutant Pb signatures suggesting an efficient pollutant Pb turnover metabolism. The comparison of Pb distribution between adult and juvenile cohorts suggests the role of dietary exposure and possible maternal offloading of Pb during gestation, likely associated to vitellogenesis in this aplacental viviparous deep-sea shark.

The catalytic hydrogenolysis of a typical model compound of mulching film waste, polyethylene, was investigated as a potential way to improve economic efficiency of mulching film recycling. Nickel-based heterogeneous catalysts are proposed for polyethylene hydrogenolysis to produce liquid hydrocarbons. Among catalysts supported on various carriers, Ni/SiO₂ catalyst shows the highest activity which may due to the interactions between nickel and silica with the formation of nickel phyllosilicate. As high as 81.18% total gasoline and diesel range hydrocarbon was obtained from the polyethylene hydrogenolysis at relatively mild condition of 280 °C, and 3 MPa cold hydrogen pressure. The result is comparable to what have been reported in previous studies using noble metal catalysts. The gasoline and diesel range hydrocarbon are n-alkanes with a distribution at a range of C₄–C₂₂. The gas products are primarily CH₄ along with a small amount of C₂H₆ and C₃H₈. High yield of CH₄ as much as 9.68% was observed for the cleavage of molecule occurs along the alkane chain.

Engine start-stop (S&S) technology has been substantially incorporated into modern vehicles to save fuel during idling in congested urban areas because fuel economy regulations have become more stringent. However, the potential for increasing particle emissions after engine restarts, especially in cold environments, is of great concern. To investigate the effects of S&S systems on fuel consumption and tailpipe emissions, a chassis dynamometer was employed to measure the fuel consumption, particulate matter (PM), solid particle number (PN), particle number size distribution and black carbon (BC) for a typical gasoline direct injection vehicle when the S&S was on (S&S-on) and when the S&S was off (S&S-off) according to the worldwide harmonized light-duty test cycle in both hot (28 °C) and cold (5 °C) environments. S&S operation resulted in 3.1–4.3% fuel-savings at 28 °C but had a tendency to increase particulate emissions, especially of BC (21.8–31.8%) and PM (19.2–32.8%). Although PN emissions with S&S-on over the entire cycle were slightly lower than those with S&S-off, more particles were emitted during the engine restart moments. In a cold environment, the fuel-savings advantage of the S&S system was weakened, and the negative impacts on the particle emissions during the restart moment worsened. The S&S system resulted in higher abundances of accumulation mode particles, especially under cold ambient conditions. The relationship between the PN reduction rates and idling segments was determining to be exponential. Our results indicate that the S&S system, which may increase particle emissions during restarts, does save fuel, and that a comprehensive evaluation of the system in cold environments is needed to determine the serviceability of new engine technologies and after-treatments.

Air pollution is among the top risk faced by people around the world, and therefore combating it is among the top priorities. It begins with identifying the sources that contribute the most to local air pollution to prioritize their control. There are advanced methods for source identification and apportionment, but such methods are not available in many low-income countries and not everywhere in all high-income countries. We propose a simplified method by using source the signatures to help obtain information about the local source contribution if no other methods are available. Using low-cost monitors, particle mass (PM₂.₅) and carbon monoxide (CO) concentrations were measured and the ratio of CO/PM₂.₅ was determined. We investigated outdoor and indoor sources, including vehicular exhaust, combustion of biomass, incense and mosquito coil burning, and cigarette smoking. The results show that the ratios differed significantly between certain pollutant sources. Compressed natural gas (CNG) engines have a high ratio (mean value of 972 ± 419), which is attributed to relatively low PM₂.₅ emissions, while ship emissions and cigarette smoke recorded a relatively low ratio. Most traffic emissions recorded higher ratios than those of bushfire emissions, and ratios of most outdoor pollutant sources were much higher than those of indoor pollutant sources. There is a clear trend for ratios to decrease from high to low for CNG, petrol, diesel for buses, and fuel for ships. Our results suggest that the ratio of CO/PM₂.₅ can be used as an effective method to identify pollution sources.

The emission factor (EF) is a parameter used to assess vehicle emissions. Many studies have reported EFs for vehicles in driving conditions. However, the idling emissions should not be neglected in characterizing actual vehicle emissions in congested large cities, where idling is very common on the road. Whereas, EF data for idling vehicles have scarcely been reported in the literature, let alone comparison of different fuels. In this study, the EFs of passenger cars burning four types of fuels - gasoline, compressed natural gas (CNG), diesel, and liquefied petroleum gas (LPG) were measured and compared. The emissions data for CO, CO₂, unburned hydrocarbon (HC), and NO were recorded to calculate fuel-based EFs in units of g pollutants/kg fuel burned. EFs for CO, HC, and NO were compared for the four fuels. Diesel vehicles had the highest EF for CO, with an average value of 35.12 ± 21.37 g/kg fuel, due to low concentration of CO₂ in lean operation compared to CO emission. CNG vehicles had the highest EF for HC, with an average value of 28.15 ± 11.97 g/kg fuel, due to high concentration of unburned methane gas due to slow CNG flame speed whereas diesel vehicles again had the highest EF for NO due to high temperature and pressure and freezing of NO decomposition reaction, with an average value of 12.07 ± 5.37 g/kg fuel. Further comparison was conducted to analyze the effects of two additional variables on EF: engine displacement volume and model/brand year. Only the gasoline-fueled vehicles showed an increase in EFs (for CO, HC and NO) with the vehicle age according to the model year. However, no clear correlation was observed for CNG, LPG, and diesel-fueled vehicles. Finally, the EF results were compared with those reported in the literature, which have been measured in various countries under both idling and non-idling conditions. Because the idling EFs were not substantially smaller than those under moving conditions, and vehicles spend substantial time idling in large cities, idling emissions should not be ignored in the emission inventories for large cities.

The contamination status of heavy metals in urban environment changes frequently with the industrial structure adjustment, energy conservation and emission reduction and thus requires timely investigation. Based on enrichment factor, multivariate statistical analysis and isotope fingerprinting, we assessed comprehensively the inputs and sources of heavy metals in different samples from an urban area that was less impacted by leaded gasoline exhaust. The road dust contained relatively high levels of Cr, Pb and Zn (with enrichment factor >2) that originated from both exhaust and non-exhaust traffic emissions, while the moss plants could accumulate high levels of Pb and Zn from the deposition of traffic exhaust emission. This suggest that the traffic emission is still an important source of metals in the urban area although gasoline is currently lead free. On the contrary, the occurrences of metals in the urban soils were controlled by natural sources and non-traffic anthropogenic emission. These findings revealed that different samples would receive different inputs of metals from different sources in the urban area, and the responsiveness and sensitiveness of these urban samples to metal inputs can be ranked as moss ≥ dust > soil. Taken together, our results suggested that in order to avoid generalizing and get detail source information, multi-samples and multi-measures must be adopted in the assessment of integrated urban environmental quality.

Urban transportation is one of the leading causes of air pollution in big cities. In-use emissions of vehicles are higher than the emission control certification levels. The current study uses a roadside remote sensing emission monitoring campaign to investigate (a) fraction of high emitters in the light-duty vehicle (LDV) fleet and their contributions to the total emissions, (b) emission inspection (I/M) programs' effectiveness, and (c) alternate fuel (natural gas) encouragement policy. LDVs consist of passenger or freight transport vehicles with four wheels equivalent to classes M1 and N1 of European union vehicle classifications. The motivation is to assess the current emission inspection program's success rate and study the impact of the increased natural gas vehicle market share policy. It is also meant to present and validate remote sensing as a possible backup method to the current I/M program.The emission remote sensing campaign was conducted to measure emissions of CO, HC, and NO of the LDV fleet. Fleet age, engine size, and fuel type (gasoline or natural gas) were extracted and correlated with emissions. It was found that CO and HC emissions are five times higher for cars more than fifteen years old of age compared to those less than five years old. Analyses of high-emitters showed that almost 20% of the fleet were high-emitters and responsible for roughly half of CO, HC, and NO emissions.The correlation between the I/M program and the remote sensing to identify high-emitters was weak. Which indicates the need for an improved I/M program. It shows that even a limited remote sensing campaign is beneficial as a complementary monitoring tool to the I/M program. The study showed the same fraction of high-emitters in natural gas (methane) vehicles, despite the national policies to increase natural gas vehicle fraction in the market for reduced emissions.

Black carbon (BC) is the most potent light-absorbing component of particulate matter and can have a significant warming impact. On-road vehicles are a major source of BC and a significant contributor to global warming. This paper establishes an updated inventory to quantify the mitigation potential of efforts to control BC emissions from on-road transportation in China. The total emissions of BC from on-road vehicles in China were 152.1 thousand tons in 2017. Heavy-duty diesel fleets accounted for a large percentage of emissions, whereas light-duty gasoline fleets presented a gradually increasing trend of emissions. Historically, comprehensive control policies for on-road vehicle emissions have achieved substantial BC reductions, with a 45% decrease in 2017 compared to 2000. With the implementation of stringent control policies and the development of advanced control technologies, BC emissions from the on-road sector may have a greater reduction potential in the future. By 2035, three various future scenarios representing different stringency levels of emission controls will reduce BC emissions by 58%, 90%, and 93% relative to 2017. The major benefits in reducing BC emissions result from more stringent emission standards and the accelerated retirement of older heavy-duty diesel vehicles. The shorter lifetime of BC than that of CO₂ implies that the mitigation of BC emissions would offer an important opportunity to contribute to alleviating global warming in the short term. Our assessment reveals that in 2035, the most stringent scenario, Scenario PC3, could deliver a CO₂-equivalent emission reduction on a 20-year scale of 234.2 (GWP₂₀₋yᵣ) million tons compared with the NAP Scenario, which is equivalent to reducing the oil consumption in China’s transportation sector by nearly 20% from a climate impact perspective.

Antarctic trace element records could provide important insights into the impact of human activities on the environment over the past few centuries. In this study, we investigated the atmospheric concentrations of 14 representative heavy metals (Al, As, Cd, Co, Cu, Fe, K, Mg, Mn, Pb, Sb, Sr, Tl and V) from 174 samples collected in a 4-m snow pit at Dome Argus (Dome A) on the East Antarctic Plateau, covering the period from 1950 to 2016 A.D. We found great variability in the annual concentration of all metals. The crustal enrichment factors suggest that the concentrations of some heavy metals (Cd, Sb, Cu, As and Pb) were likely influenced by anthropogenic activities in recent decades. An analysis of source regions suggests that heavy metal pollution at Dome A was largely caused by human activities in Australia and South America (e.g. mining production, leaded gasoline). Based on the relationship between the trace elements fluxes and sea ice concentration (SIC), sea surface temperature (SST) and annual mean air temperature at 2 m above the ground (T₂ₘ), our analysis shows that deposition and transport of atmospheric aerosol at Dome A were influenced by circum-Antarctic atmospheric circulations.

Continuous tightening emission standards (ESs) facilitate the reduction of organic gas emissions from gasoline vehicles. Correspondingly, it is essential to update the emissions and chemical speciation of total organic gases (TOGs), including volatile organic compounds (VOCs), intermediate volatility organic compounds (IVOCs), CH₄, and unidentified non-methane hydrocarbons (NMHCs) for assessing the formation of ozone and secondary organic aerosol (SOA). In this study, TOG and speciation emissions from 12 in-use light-duty gasoline vehicle (LDGV) exhausts, covering the ESs from China II to China V, were investigated on a chassis dynamometer under the Worldwide Harmonized Light-duty Test Cycle (WLTC) in China. The results showed that the most effectively controlled subgroup in TOG emissions from LDGVs was VOCs, followed by the unidentified NMHCs and IVOCs. The mass fraction of VOCs in TOGs also reduced from 61 ± 9% to 46 ± 18% while the IVOCs gently increased from 2 ± 0.4% to 8 ± 4% along with the more stringent ESs. For the VOC subsets, the removal efficiency of oxygenated VOCs (OVOCs) was lower than those of other VOC subsets in the ESs from China IV to V, suggesting the importance of OVOC emission controls for relatively new LDGVs. The IVOC emissions were mainly subject to the ESs, then driving cycles and fuel use. The formation potentials of ozone and SOA from LDGVs decreased separately 96% and 90% along with the restricted ESs from China II-III to China IV. The major contributor of SOA formation transformed from aromatics in the VOC subsets for China II-III vehicles to IVOCs for China IV/V vehicles, highlighting that IVOC emissions from LDGVs are also needed more attentions to control in future.