Black Carbon Emission Factors Research Articles

Real-world black carbon emissions of gasoline vehicles at urban intersections

To gain insight into the real-world black carbon (BC) emission patterns at urban intersections, we employed a portable emission measurement system (PEMS) to assess the BC emissions from three light-duty gasoline vehicles along a designated urban route. The BC emission factors were evaluated, and the contributions of vehicle operating conditions at the intersections to the total BC emissions were quantified. The results show that the BC emission factors in an intersection area range from 0.045 to 0.291 mg/km, higher than those at an intersection's connecting sections. The average BC emission factor at signalized intersections is 17.07% higher than at roundabouts. Emission contribution analysis of driving conditions showed that in a state of non-free traffic flow, acceleration and deceleration conditions are responsible for 39% ∼ 56% and 24% ∼ 33% of BC emissions at intersections, respectively. We also found that vehicle specific power (VSP) and delay time are almost equally crucial for BC emissions from vehicles at intersections in the multiple linear regression. Our research reveals the significant impact of vehicle delay time and acceleration conditions on black carbon emissions at urban intersections, further emphasizing the importance of smooth (congestion-free) intersection operation and steady driving in reducing urban black carbon emissions.

Long-term trends of black carbon and particle number concentrations and their vehicle emission factors in Stockholm

Black carbon (BC) and particle number (PN) concentrations are usually high in cities due to traffic emissions. European mitigation policies, including Euro emission standards, have been implemented to curb these emissions. We analyzed BC and PN (particle diameter Dp > 4 nm) concentrations in Stockholm spanning the years 2013–2019 (BC) and 2009–2019 (PN) measured at street canyon and rooftop sites to assess the effectiveness of the implemented policies. Combining these data with inverse dispersion modeling, we estimated BC and PN emission factors (EFBC and EFPN) for the mixed fleet, reflecting real-world driving conditions. The pollutants showed decreasing trends at both sites, but PN concentrations remained high at the canyon site considering the World Health Organization (WHO) recommendations. BC concentrations declined more rapidly than PN concentrations, showing a −9.4% and −4.9% annual decrease at the canyon and −7.2% and −0.5% at the rooftop site in the years 2013–2019. The EFBC and EFPN trends showed that the mitigation strategies for reducing particulate emissions for on-road vehicles were successful over the study period. However, the introduction of biofuels in the vehicle fleet —ethanol and later rapeseed methyl ester (RME)— increased the concentrations of particles with Dp < 10 nm before the adoption of particulate filters in the exhausts. Stricter Euro emission regulations, especially with diesel particulate filters (DPF) in Euro 5, 6, and VI vehicles, led to 66% decrease in EFBC and 55% in EFPN. Real-world EFBC surpassed HBEFA (Handbook Emission Factors for Road Transport) database values by 2.4–4.8 times; however, direct comparisons between real-world and HBEFA EFPN are difficult due to differences in lower cut-off sizes and measurement techniques. Our results underscore the necessity for revising the HBEFA database, updating laboratory testing methods and portable emission measuring systems (PEMS) measurements to account for liquid condensate contributions to PN measurements.

Source apportionment of black carbon and combustion-related CO2 for the determination of source-specific emission factors

Abstract. Black carbon (BC) aerosol typically has two major sources in the urban environment: traffic and domestic biomass burning, which has a significant contribution to urban air pollution during the heating season. Traffic emissions have been widely studied by both laboratory experiments (individual vehicle emission) and real-world measurement campaigns (fleet emission). However, emission information from biomass burning is limited, especially an insufficiency of experimental results from real-world studies. In this work, the black carbon burden in the urban atmosphere was apportioned to fossil fuel (FF) and biomass burning (BB) related components using the Aethalometer source apportionment model. Applying the BC source apportionment information, the combustion-related CO2 was apportioned by multilinear regression analysis, supposing that both CO2 components should be correlated with their corresponding BC component. The combination of the Aethalometer model with the multilinear regression analysis (AM-MLR) provided the source-specific emission ratios (ERs) as the slopes of the corresponding BC–CO2 regressions. Based on the ER values, the source-specific emission factors (EFs) were determined using the carbon content of the corresponding fuel. The analysis was carried out on a 3-month-long BC and CO2 dataset collected at three monitoring locations in Ljubljana, Slovenia, between December 2019 and March 2020. The measured mean site-specific concentration values were in the 3560–4830 ng m−3 and 458–472 ppm ranges for BC and CO2, respectively. The determined average EFs for BC were 0.39 and 0.16 g(kg fuel)−1 for traffic and biomass burning, respectively. It was also concluded that the traffic-related BC component dominates the black carbon concentration (55 %–64 % depending on the location), while heating has the major share in the combustion-related CO2 (53 %–62 % depending on the location). The method gave essential information on the source-specific emission factors of BC and CO2, enabling better characterization of urban anthropogenic emissions and the respective measures that may change the anthropogenic emission fingerprint.

Emission characteristics and light absorption apportionment of carbonaceous aerosols: A tunnel test conducted in an urban with fully enclosed use of E10 petrol

To reduce the heavy dependence on petroleum, bioethanol has been increasingly employed as an alternative and sustainable transportation fuel. However, the characteristics of black carbon (BC) emissions from E10 petrol vehicles (i.e., ethanol-gasoline containing 10% ethanol) are still unclear, especially under real driving conditions. Here, a tunnel test was conducted during a cold winter. This tunnel was characterized by heavy traffic comprising more than 98% E10-fueled gasoline vehicles (GVs). Real-time BC concentrations, traffic parameters and meteorological conditions were recorded during the sampling campaign. The average BC concentration inside the tunnel (10.94 ± 5.02 μg m−3) was almost twice the background concentration. Based on aethalometer AE33 in situ measurements and the minimum R-squared (MRS) method, real-time aerosol light absorption was apportioned. The light absorption proportions of BC, primary brown carbon (BrC1) and secondary brown carbon (BrC2) were 79.86%, 2.78% and 17.36%, respectively, at 370 nm. The BC emission factor (EFBC) of the E10-fueled vehicles was 1.09 ± 0.49 mg km−1·veh−1 and 15.24 ± 6.85 mg·(kg fuel)−1, lower than those of traditional gasoline fueled vehicles in previous studies. This study can support the compilation of vehicular BC emission inventories, provide recommendations for biofuel policies and contribute to comprehensively understanding the climatic impact of E10 petrol.

Tunnel measurements reveal significant reduction in traffic-related light-absorbing aerosol emissions in China

Light-absorbing aerosols (LAA), including black carbon (BC) and brown carbon (BrC), profoundly impact regional and global climate. Vehicle emission is an important source of LAA in urban areas, but real-world emission features of LAA from the urban vehicle fleet are not fully understood. This study evaluates traffic-related BC and BrC emission factors (EFs) and their vehicular emission inventories via road tunnel measurements in Tianjin, China, in 2017 and 2021. The distance-based and fuel-based EFs of BC for the mixed fleet were 1.05 ± 1.28 mg km−1 veh−1 and 0.057 ± 0.057 g (kg-fuel)−1, respectively, in 2021, with a dramatic decrease of 80.6 % compared to those in 2017. The BC EFs for gasoline vehicles (GVs, including traditional gasoline and hybrid vehicles) and diesel vehicles (DVs) were 0.55 ± 0.065 mg km−1 veh−1 and 10.5 ± 2.52 mg km−1 veh−1, respectively, in 2021. Compared to 2017, the BrC EFs also decreased significantly in 2021, by 10.8–53.6 %, with 0.32 ± 0.45 mg km−1 veh−1 and 0.018 ± 0.020 g (kg-fuel)−1 of distance-based and fuel-based EFs for mixed fleet. The BrC EFs for GVs and DVs were 0.091 ± 0.024 mg km−1 veh−1 and 3.06 ± 0.91 mg km−1 veh−1, respectively, in 2021. Based on the BC and BrC EFs for GVs and DVs and annual mileage for each vehicle category, the annual vehicular LAA emission inventories were estimated. From 2017 to 2021, the annual vehicular LAA emissions in Tianjin have been significantly reduced, by 69 % for BC and 10 % for BrC. DVs account for a small amount of the vehicle population (8.4 %), but contribute to most of the BC (83 %) and BrC (86 %). Our study demonstrates the significant reduction of vehicular light-absorbing aerosols emission due to vehicle pollution prevention and control in China.

Multi-type emission factors quantification of black carbon from agricultural machinery based on the whole tillage processes in China

Black carbon (BC), as one of the short-lived climate pollutants, is becoming more prominent contribution from non-road mobile source, especially for agricultural machinery (AM) in China. However, the understanding of BC emissions from AM is still not clear, and the BC emission factors (EFs) are also limited. In this study, we conducted real-world measurements on twenty AM to investigate the instantaneous BC emission characteristics and quantify BC EFs under the whole tillage processes. We find the instantaneous BC emissions and fuel consumptions are obvious differences and present good synchronization under different tillage processes. Multi-type (CO2-, fuel-, distance-, time-, and area-based) EFs of BC are developed, which are significantly affected by different tillage processes and emission standards of the used AM. While AM conducting rotary tillage, ploughing, harvest corn and harvest wheat on the same area of land, total BC emissions by using the China III emission standard AM will be reduced by 56%, 36%, 88%, and 87% than those by using China II emission standard AM, respectively. Furthermore, for corn and wheat production under the whole tillage processes, BC EFs are 16.90 (6.03–39.12) g/hm2 and 18.18 (5.91–38.69) g/hm2, CO2 EFs are 112.64 (72.07–195.98) g/hm2 and 103.72 (71.47–167.02) g/hm2, respectively. We estimate the BC and CO2 emissions from wheat and corn productions based on the average area-based EFs. The large fluctuation ranges of BC and CO2 emissions in different tillage processes and the whole processes can reflect that the use of AM in China is uneven. It also indicates that there is a large space for BC and CO2 emission reduction and optimization. Therefore, more attention should be paid to the control of BC and CO2 emissions from AM. We believe that the recommended multi-type EFs are applicable for the quantification of BC emissions from AM in China and other countries.

On-road vehicular emission characterization from the road-tunnel measurements in India: Morphology, emission factors, and sources

In India, there is very limited data on vehicular emission characterization in real-world driving conditions and the contribution of non-exhaust vehicular emissions to ambient particulate matter (PM) is still unanswered. Furthermore, there are no real-world emission factors (EFs) for the PM constituents. Thus, this study aims to characterize the trace elements and metals, and black carbon (BC) in PM2.5 and PM10 from the light-duty vehicles (LDVs) and mixed vehicular fleet with significant contribution of heavy-duty vehicles (HDVs) through road-tunnel measurements. Real-world EFs were estimated for the measured PM chemical constituents. Further, source apportionment was carried out to find the plausible sources and their contribution to total PM2.5 and PM10 road traffic emissions. Air pollutant and traffic measurements were conducted at two roadway tunnels: Eastern Freeway tunnel (FT; only LDVs) and Kamshet-I tunnel (KT; 80% LDVs & 20% HDVs) in Mumbai, India covering both peak and off-peak traffic hours. Major elements (Al, Ca, Fe, K, Mg, and Na) constitute 90─93% of total measured elemental concentrations in both PM2.5 and PM10 road traffic emissions. Overall, the elemental concentrations were higher for the HDV-dominant fleet than the LDV-fleet for both PM2.5 and PM10. Similarly, BC was higher for the HDV-dominant fleet which is corroborated by the morphological analysis. The measured BC, trace elements and metals EFs in this study were higher than those reported than previous road tunnel studies with similar vehicle composition indicating the presence of high-emitting vehicles in this study. The dominant proportion of PM2.5 road traffic emissions was from the tailpipe (52%) followed by brake wear (30%) and vehicular driven resuspended road dust (18%). Whilst, resuspended road dust (63%) was identified as the major source of PM10 traffic emissions followed by vehicular exhaust (28%) and brake wear (9%). With the potential increase in the share of electric and hybrid vehicles in the vehicular fleet, the relative contribution of non-exhaust emissions to the airborne PM will be more significant. Hence, there is an imminent need to regulate non-exhaust vehicular emissions.

Estimation of the concentration of nano-carbon black in tire-wear particles using emission factors of PM10, PM2.5, and black carbon.

Particulate matter (PM) from automobile exhaust has drastic effects on human health. The enforcement of environmental laws has controlled vehicle emissions and reduced the total PM. However, another significant source of PM is debris from tire wear, break wear, and road wear. In particular, tire-wear particles (TWPs) are further fragmented into nanoparticles, similar to the PMx or black carbon (BC) sources. As approximately 30wt% of carbon black (CB) is used as filler in tires, TWPs can fragment into free-bound nano-CB. This study evaluates the emission factors of BC from the ternary plots of PMx and BC to estimate the concentration of nano-CB in TWPs. Based on the emission factors of BC for TWP, approximately 500 monitoring data points were acquired at four different sites. Semi-closed sites in a field measurement test have 2.9-4.0 times larger BC concentration than open sites. The mass concentration of nano-CB evaluated with the BC data and emission factors at the open sites is 22.47-23.96ng/m3, whereas that at the semi-closed sites is 66.32-90.33ng/m3. Transmission electron microscopy analysis with scanning mobility particle sizer and selected-area electron diffraction reveals grape-like aggregated nanoparticles, which is considered as CB. To compare the effect of the washing out of airborne particulates by rain, further analysis is conducted on the interior and exterior of the tunnel on a rainy day. While the concentration of PMs was effectively reduced by rainfall, the amount of BC and CB in the interior of a tunnel was not changed. Namely, even under rainfall, nano-CB still exists in the tunnels and thus free-bound CB and nanoparticles released from TWP will be effected on the human health.

Physical, chemical and optical properties of PM2.5 and gaseous emissions from cooking with biomass fuel in the Indo-Gangetic Plain

The current study was designed to capture real-world cooking process-wise emissions generated by the combustion of mixed biomass fuel in traditional mud cookstoves in rural kitchens of the north Indian state of Uttar-Pradesh during regular meal preparations. Combustion characteristics, including modified combustion efficiency, thermal efficiency and burn rate, were examined to understand their relationship with emissions. Variations were observed in emission factors (EFs) of PM2.5, trace gases, namely CO, CO2, NOx and SO2, for different cooking processes. While the highest emission of PM2.5, CO and SO2 were observed for boiling (7.0 ± 2.7, 68 ± 29.3, 1.0 ± 1.7 gkg−1, respectively), CO2 and NOx recorded the highest EFs for frying (1537 ± 278.2 & 1.6 ± 0.9 gkg−1 respectively). Although the study reported similar carbon content emissions for different processes, high EC emissions were observed for baking (1.1 ± 0.3 gkg−1). A high concentration of K+ (indicating biomass burning) and toxic trace metals including Al, Cu, Sr, Ti, Mo & Cd has been reported in the present study. EFs of black carbon and brown carbon from mixed fuel burning during uncontrolled cooking have been discussed for different cooking processes which are critical inputs to emission inventories and radiative forcing calculation. The processes of frying and sautéing were found to be more consistent in emissions of pollutants than boiling and baking (variability- 13 %-167 %). Overall, this study emphasizes that a measurement of combustion characteristics and cooking method type should also be contemplated along with fuel and stove types during field emission studies.

In-Use Passenger Vessel Emission Rates of Black Carbon and Nitrogen Oxides.

This study quantified emission factors of black carbon (BC) and nitrogen oxides (NOx) from 21 engines on in-use excursion vessels and ferries operating in California's San Francisco Bay, including EPA uncertified and Tier 1-4 engines and across engine operating modes. On average, ∼60 fuel-based emission factors per engine were measured using a novel combination of exhaust plume capture combined with GPS location and speed data that can be more readily deployed than common portable emissions measurement systems. BC and NOx emission factors (g kg-1) were lowest and least variable during fast cruising and highest during maneuvering and docked operation. Selective catalytic reduction (SCR) reduced NOx emissions by ∼80% when functional. However, elevated NOx emissions that exceeded corresponding exhaust standards were measured on most Tier 3 and Tier 4 engines sampled, which can be attributed to inactive SCR during frequent low engine load operation. In contrast, BC emissions exceeded the PM emission standard for only one engine, and SCR systems employed as a NOx reduction technology also reduced emitted BC. Using these measured emission factors to compare commuting options, we show that the CO2-equivalent emissions per passenger-kilometer are comparable when commuting by car and ferry, but BC and NOx emissions can be several to more than ten times larger when commuting by ferry.

Quantitative of instantaneous BC emissions based on vehicle specific power from real-world driving diesel trucks in China

In-depth exploration of the potential links between instantaneous black carbon (BC) emissions and driving parameters from real-world diesel trucks (DTs) is a key step toward development of a highly flexible vehicle emissions estimation system. In this study, we conducted real-world measurements on 22 DTs with mainstream types and emission standards, and obtained instantaneous data of BC emissions and vehicle driving. Since vehicle specific power (VSP) is an excellent surrogate for engine load, we characterize the instantaneous BC emissions and VSP distributions, and then establish links between VSP and fuel consumption, VSP and BC emission rates, VSP and BC emission factors (EFs), respectively. We find that BC emission rates of China V light-duty DTs installed with diesel particulate filter (DPF) are significantly lower (2 to 3 orders of magnitude) than those with China III and China IV. Frequent acceleration and deceleration of vehicles maybe the main reason leads to high BC emissions. The distribution of VSP is mainly concentrated in the ranges of −30 to 35 kW/t in the scope of this study. We find that VSP and BC EFs did not show a consistent pattern for all tested DTs, and BC EFs present obvious fluctuations with the VSP variation. The average fuel-based BC EFs vary by factors of 2.27–8.25 from the lowest to highest EFs. Through a fitting of the third-order polynomial function, we finally quantify and provide fitting formulas of BC EFs and VSP under more detailed categorization. Our results can provide important data support for accurate quantification of BC EFs, and even emission inventory calculations.

Non-negligible emissions of black carbon from non-road construction equipment based on real-world measurements in China

Non-road construction equipment (NRCE) has become a vital contributor to urban air pollutants with the rapid urbanization in China. Black carbon (BC), as a key pollutant emitted from NRCE (mainly diesel-fueled), has attracted considerable concerns due to adverse impacts on climate change, visibility, and human health. However, the understanding of its emissions is still unclear based on limited research results. In this study, we conducted real-world measurements on BC emissions from 12 excavators and 9 loaders to characterize the variation and quantify fuel-based emission factors (EFs) by using a synchronous platform based on PEMS (SP-PEMS). We analyzed the impacts of key factors (operation mode, emission standard, and engine rated power) on BC emission comprehensively. High BC emission in working mode may be mainly owing to the increase of fuel consumption and the deterioration of air-fuel ratio. With more stringent emission standards, BC EFs of all tested NRCE present significant decreasing trends. Interestingly, NRCE with high rated power generally exhibits lower BC emissions. Through comparison, we find BC EFs in this study are generally higher than elemental carbon (EC) EFs reported in previous studies, which will lead BC emissions from NRCE to be underestimated while EC EFs are used instead of BC EFs. Furthermore, BC EFs of NRCE with Stage III are significantly higher (1–3 orders of magnitude) than those of on-road diesel trucks with the current mainstream emission standards of China IV and China V, which reinforces the urgency and importance of controlling BC emissions from NRCE in China. Finally, we recommend BC EFs of excavators and loaders under different emission standards and operation modes, and which preliminarily fills the gap in localized BC EFs of typical NRCE to relieve the urgent needs for emission inventory calculation.

Evaluation of heavy-duty vehicle emission controls with a decade of California real-world observations

ABSTRACT Over the past decade, efforts to reduce emissions of particulate matter (PM) and oxides of nitrogen (NO + NO2, or NO x ) from heavy-duty diesel vehicles (HDDVs) have led to the widespread adoption of both Diesel Particulate Filters (DPFs) to control PM and Selective Catalytic Reduction (SCR) to control NO x . We evaluated the performance of DPFs and SCR with 13,327 real-world fuel-based Black Carbon (BC) and NO x emission factors from 9,167 unique heavy-duty vehicles (primarily HDDVs) measured at four sites in California (two ports, two highways) from 2011 to 2018. BC emission factors have decreased by 90% during the past decade. At the same time, BC distributions have become increasingly skewed toward “high-emitters” – e.g., the portion of the HDDV fleet responsible for half of all BC emissions has decreased from ~16% to ~3%. NO x emission factors have also decreased over the past decade, but by only 31%. They remain roughly five times greater than in-use thresholds.We examined changes in BC and NO x emissions with engine age. BC emissions from DPF-only trucks decreased slightly but insignificantly, by 6 ± 15 mg/kg fuel per year, while for DPF+SCR trucks they increased by 5 ± 3. These changes are less than 5% of in-use thresholds. The annual increase in NO x emissions with age was much greater: 1.44 ± 0.28 g/kg for older SCR trucks without on-board diagnostic (OBD) capabilities and 0.48 ± 0.35 for newer trucks with OBD, roughly 20– 50% of in-use thresholds. Paired t-tests on the over 600 vehicles that were observed in multiple campaigns were consistent with these results. Observed changes in BC emissions with age were best fit with a “gross emitter” model assuming an annual DPF failure rate of 0.83 ± 0.01% for DPF-only trucks and 0.56 ± 0.01% for DPF+SCR trucks.Implications: These observations of real-world HDV emission factors have several major implications for regulatory efforts to reduce them. The increasing importance of a relatively small number of high BC emitters suggests that widespread sampling of the on-road fleet will be necessary to identify these vehicles. On the other hand, the much more ubiquitous deterioration in NO x control measures may be better addressed by incorporating on-board diagnostic systems, with telematic data transfer when possible, into inspection and maintenance programs. These NO x observations also highlight the need for strengthening heavy-duty SCR durability demonstration requirements.

Real-world emission characteristics of black carbon emitted by on-road China IV and China V diesel trucks

Diesel vehicle is an important source of black carbon (BC). A portable emission measurement system including a photo-acoustic extinctiometer and SEMTECH-LDV was used to measure the real-world emissions of 14 light-duty and heavy-duty diesel trucks (LDDTs and HDDTs, meeting the China IV and China V standards) in Beijing. BC emission factors and the BC/PM2.5 ratio were obtained, and the effects of the vehicle type, emission standard and driving cycle on emissions were analyzed. The tightening of emission standards and the advancement of vehicle technology have reduced BC emissions from the China II standard to the China V standard. The emission reductions of BC are lower than those of other components of PM2.5 from the China II standard to the China IV standard but higher from the China IV standard to the China V standard. The BC and PM2.5 had the same main sources for the HDDTs and China IV LDDTs but had different sources for the China V LDDTs having diesel particulate filters. The BC/PM2.5 ratios of LDDTs, and HDDTs decreased from the China IV standard to the China V standard by 97.2% and 38.2%, respectively. The BC/PM2.5 ratio for China V LDDTs was 10 to 20 times lower than that for other diesel vehicles. The BC emissions tested under the highway driving cycle were 39.4% ± 16.7% lower than those under the no-highway driving cycle, but the BC/PM2.5 ratios had the opposite tendency. More China V and China VI heavy-duty diesel vehicles equipped with diesel particulate filters need to be tested to obtain more accurate BC/PM2.5 data and to improve the readiness of emission inventory calculations. The findings of this study help clarify the BC emission characteristics of diesel vehicles on actual roads and provide scientific basis for the formulation of emission control strategies for diesel vehicles in China.

Determining black carbon emissions and activity from in-use harbor craft in Southern California

Black carbon (BC) emitted from diesel fuel combustion contributes significantly to particulate matter emissions that impact air quality and human health. Off-road sources of BC are increasingly important as emissions from on-road vehicles continue to decrease. This study characterizes harbor craft emissions and activity, including tugboats, passenger boats, and fishing vessels. Vessel traffic data suggest that the Southern California tugboat fleet is composed of relatively few unique vessels, yet tugboats spent more non-idle operating time within 3 nautical miles of California's coast than all other vessel types (including large ocean-going vessels). Fuel-based BC emission factors (EFBC) were measured from shore in the San Pedro Bay Port Complex in Los Angeles using the plume capture method, yielding 78 EFBC values from ~45 unique vessels. Passenger boats had the highest geometric mean EFBC (0.56 ± 0.86 g/kg). Tugboats had higher EFBC while moving with versus without loads (0.64 ± 0.29 and 0.48 ± 0.67 g/kg, respectively). Non-idle EFBC for vessels were skewed, with the dirtiest 20% of plume intercepts contributing ~47% of BC emissions. Given the trends observed in both vessel activity and EFBC values, tugboats could be worthwhile targets for emissions reductions.

Atmospheric concentrations and emission ratios of black carbon and nitrogen oxides in the Arabian/Persian Gulf region

The atmospheric concentration of black carbon (BC) has paramount importance worldwide due to its role in global warming and its adverse effect on human health. Only limited information is available about BC concentration and emission factors from the Arabian/Persian Gulf region despite the presence of significant sources including petrochemical industry and maritime shipping. The atmospheric concentrations of BC, nitrogen oxides (NO, NO2), ozone and particulate matter (PM10) were monitored at a suburban location and at a central residential location in Doha, Qatar during fall-spring 2016–2017. Elevated NOX and BC mean concentrations (25.8 ppbv and 5.17 μg/m3 respectively) and maximum values (228 ppbv vs. 27 μg/m3) were measured at both locations. The average ozone mixing ratio was 15.9 ppbv (max. 52.6 ppbv). Typically, the BC concentration was correlated with NOX, which indicates common sources. BC/NOX emission ratios (ER) were calculated to characterise the sources, while the NO/NOX concentration ratio was used as a proxy of pollution age. The calculated BC/NOX emission ratios were found to be high comparing to the EMEP database, with the means of 0.13 μg m−3 ppbv−1 (suburban location) and 0.10 μg m−3 ppbv−1 (residential location). The BC/NOX ER did not show significant daily variation, while the NO/NOX ratio showed typical urban time pattern with high ratio during morning rush hours following by a decreasing trend during afternoon, and minimum values at night-time. The PM10 concentrations were high during the measurement period with a mean of 103 μg m−3, which is typical in the Gulf region. During occasional dust storm events the PM10 hourly average concentration raised peaked at 1054 μg m−3. Significant influence of mineral dust was observed on the BC measurement and the absorption properties, as it was increasing the BC readings and widening the distribution of the absorption Ångström exponent. The mass absorption cross-section of mineral dust was determined during the major dust storm event.

Real-Time Black Carbon Emissions from Light-Duty Passenger Vehicles Using a Portable Emissions Measurement System

Black carbon (BC) is considered the second largest anthropogenic climate forcer, but the radiative effects of BC are highly correlated with its combustion sources. On-road vehicles are an important source of anthropogenic BC. However, there are major uncertainties in the estimates of the BC emissions from on-road light-duty passenger vehicles (LDPVs), and results obtained with the portable emissions measurement system (PEMS) method are particularly lacking. We developed a PEMS platform and evaluated the on-road BC emissions from ten in-use LDPVs. We demonstrated that the BC emission factors (EFs) of gasoline direction injection (GDI) engine vehicles range from 1.10 to 1.56 mg·km−1, which are higher than the EFs of port fuel injection (PFI) engine vehicles (0.10–0.17 mg·km−1) by a factor of 11. The BC emissions during the cold-start phase contributed 2%–33% to the total emissions. A strong correlation (R2 = 0.70) was observed between the relative BC EFs and average vehicle speed, indicating that traffic congestion alleviation could effectively mitigate BC emissions. Moreover, BC and particle number (PN) emissions were linearly correlated (R2 = 0.90), and compared to PFI engine vehicles, the instantaneous PN-to-BC emission rates of GDI engine vehicles were less sensitive to vehicle specific power-to-velocity (VSPV) increase in all speed ranges.

Optically Measured Black and Particulate Brown Carbon Emission Factors from Real-World Residential Combustion Predominantly Affected by Fuel Differences

Residential solid fuel use is an important source of black carbon (BC) but also a main source of uncertainty in BC emission inventories, as reliable real-world emission factors (EFs) and data on consumption of noncommercial household fuels are limited. In this study, particulate BC and brown carbon (BrC) for real-world indoor coal and biomass burning were evaluated using a SootScan model OT21 optical transmissometer from a field campaign including 343 biomass/coal combustion events. The highest BC EF from the burning of coal cake (a mixed fuel locally made from coal and clay) was 1.6-6.4 higher than that of other fuels, and BC EFs were higher for coal combustion than for biomass burning. The highest particulate BrC EF was from charcoal burning and was 1.5-4.3 times higher than that from other biomass and coals. Burning fuel in iron stoves had lower BC and BrC EFs, at approximately 15-66% and 40-54%, respectively, compared with burning in other stove types. The difference between heating and cooking activities was statistically insignificant (p > 0.05). A generalized linear model coupled with dominance analysis evidenced that the EFs were significantly associated with fuel and stove types, with the fuel difference being a major influencing factor explaining 68% of the variation. This suggests that a clean fuel transition would have beneficial impacts on air pollution associated with the residential sector in China. The absorption EFs differed by 2-3 orders of magnitude across different fuel-stove combinations. The Absorption Ångström Exponent values for the particulate from residential solid fuel combustions ranged from 0.92 to 3.7.

Comparing the Use of High- to Low-Cost Black Carbon and Carbon Dioxide Sensors for Characterizing On-Road Diesel Truck Emissions.

The exhaust plume capture method is a commonly used approach to measure pollutants emitted by in-use heavy-duty diesel trucks. Lower cost sensors, if used in place of traditional research-grade analyzers, could enable wider application of this method, including use as a monitoring tool to identify high-emitting trucks that may warrant inspection and maintenance. However, low-cost sensors have for the most part only been evaluated under ambient conditions as opposed to source-influenced environments with rapidly changing pollutant concentrations. This study compared black carbon (BC) emission factors determined using different BC and carbon dioxide (CO2) sensors that range in cost from $200 to $20,000. Controlled laboratory experiments show that traditional zero and span steady-state calibration checks are not robust indicators of sensor performance when sampling short duration concentration peaks. Fleet BC emission factor distributions measured at two locations at the Port of Oakland in California with 16 BC/CO2 sensor pairs were similar, but unique sensor pairs identified different high-emitting trucks. At one location, the low-cost PP Systems SBA-5 agreed on the classification of 90% of the high emitters identified by the LI-COR LI-7000 when both were paired with the Magee Scientific AE33. Conversely, lower cost BC sensors when paired with the LI-7000 misclassified more than 50% of high emitters when compared to the AE33/LI-7000. Confidence in emission factor quantification and high-emitter identification improves with larger integrated peak areas of CO2 and especially BC. This work highlights that sensor evaluation should be conducted under application-specific conditions, whether that be for ambient air monitoring or source characterization.

Real-time measurements of black carbon and other pollutant emissions from residential biofuel stoves in rural China

Biofuel stoves are an important source of black carbon (BC) emissions, which have adverse effects on the environment and human health, especially in rural areas. However, there have been only limited studies of BC emissions from residential biofuel stoves based on real-time measurements. In this study, a photo-acoustic extinctiometer (PAX)-based real-time measurement system was employed to monitor the emission characteristics of corncobs, corn stalks, cotton stalks and poplar branches in simple or improved stoves (with a total of 16 units) in Hebei Province, China. The real-time and phased emissions of BC, fine particulate matter (PM2.5), carbon monoxide (CO) and carbon dioxide (CO2) were assessed, and the effects of stove type and fuel on emissions were analyzed. Under the same conditions, polar branches were associated with the highest BC emission factors (EFs) of up to 2.64 ± 0.42 g kg−1, while the EFs for improved stoves were higher than those for simple stoves. During the ignition phase, BC emissions were found to be low, while the later addition of fuel dramatically increased emissions, followed by a gradual decrease until the next fuel addition. The phased results show that the flaming phase had the highest BC emission rate, the fuel addition phase was associated with the highest BC EF. The BC emission rates and EFs for the ignition, fuel addition, flaming and smoldering phases ranged from 0.0014–0.014, 0.11–6.32, 0.18–2.24 and 0.03–0.32 mg s−1, and from 0.04–0.18, 0.38–9.53, 0.45–3.55 and 0.12–1.01 g kg−1, respectively. This study assessed the BC emissions from residential biofuel stoves using a larger sample size than in prior work. The results increase our understanding of the BC emissions process, which is helpful in terms of improving the accuracy of BC EF estimations. The real-time measurement process described herein is also expected to provide new approaches to minimizing BC emissions.