Ratio Of Black Carbon Research Articles

Present-day radiative effect from radiation-absorbing aerosols in snow

Abstract. Black carbon (BC), brown carbon (BrC), and soil dust are the most important radiation-absorbing aerosols (RAAs). When RAAs are deposited on the snowpack, they lower the snow albedo, causing an increase in the solar radiation absorption. The climatic impact associated with the snow darkening induced by RAAs is highly uncertain. The Intergovernmental Panel on Climate Change (IPCC) Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) attributes low and medium confidence to radiative forcing (RF) from BrC and dust in snow, respectively. Therefore, the contribution of anthropogenic sources and carbonaceous aerosols to RAA RF in snow is not clear. Moreover, the snow albedo perturbation induced by a single RAA species depends on the presence of other light-absorbing impurities contained in the snowpack. In this work, we calculated the present-day RF of RAAs in snow starting from the deposition fields from a 5-year simulation with the GEOS-Chem global chemistry and transport model. RF was estimated taking into account the presence of BC, BrC, and mineral soil dust in snow, simultaneously. Modeled BC and black carbon equivalent (BCE) mixing ratios in snow and the fraction of light absorption due to non-BC compounds (fnon-BC) were compared with worldwide observations. We showed that BC, BCE, and fnon-BC, obtained from deposition and precipitation fluxes, reproduce the regional variability and order of magnitude of the observations. Global-average all-sky total RAA-, BC-, BrC-, and dust-snow RF were 0.068, 0.033, 0.0066, and 0.012 W m−2, respectively. At a global scale, non-BC compounds accounted for 40 % of RAA-snow RF, while anthropogenic RAAs contributed to the forcing for 56 %. With regard to non-BC compounds, the largest impact of BrC has been found during summer in the Arctic (+0.13 W m−2). In the middle latitudes of Asia, the forcing from dust in spring accounted for 50 % (+0.24 W m−2) of the total RAA RF. Uncertainties in absorbing optical properties, RAA mixing ratio in snow, snow grain dimension, and snow cover fraction resulted in an overall uncertainty of −50 %/+61 %, −57 %/+183 %, −63 %/+112 %, and −49 %/+77 % in BC-, BrC-, dust-, and total RAA-snow RF, respectively. Uncertainty upper bounds of BrC and dust were about 2 and 3 times larger than the upper bounds associated with BC. Higher BrC and dust uncertainties were mainly due to the presence of multiple absorbing impurities in the snow. Our results highlight that an improvement of the representation of RAAs in snow is desirable, given the potential high efficacy of this forcing.

Source apportionment of polycyclic aromatic hydrocarbons and black carbon at the western coastal areas of the Yellow Sea based on isotopic signatures

The stable and radioactive isotopes (δ13C, Δ14C and δ2H) of black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) in the sediment from the western coastal areas of the Yellow Sea (i.e. the Jiangsu coastal areas (JCA)) were examined to identify the sources these environmental pollutants in the JCA. The results presented that the spatial heterogeneous characteristics of BC and PAHs were markedly presented in the JCA. This was suggestive of presence of the contributions of multiple potential environmental pollution sources. This can be solved and decoupled by applying the Bayesian mode. Accordingly, the statistical model showed that the major environmental pollution contributions is considered as coal combustion (39%) in the JCA. The liquid fossil fuels, petrogenic sources, and biomass combustion were accounted for 27%, 19%, and 15% in the JCA, respectively. The stable and radioactive carbon isotopic ratios (δ13C and Δ14C) of BC collected from the JCA are also applied to discriminate quantitatively the source of contamination. It is demonstrated that the BC in this study originates mainly from combustion of fossil fuels. And rock-derived BC as well as C3 and C4 plants combustions are also numerically predominant for BC and PAHs pollution in the coastal area. It is implied that the environmental PAHs and BC in the JCA seem to origin relatively homologies sources. Furthermore, it is suggested that the stable and radioactive carbon isotopes as well as hydrogen isotopes may be powerful and useful method to source apportionment, and have much advantages to clarify quantitatively BC and PAH pollutions in the coastal environment, but also detailed insights into the source apportionment and fate of the organic carbon in the marginal sea.

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.

Characteristics and Sources of Black Carbon and Organic Carbon in Topsoil from Different Functional Zones of Beijing, China

Considering human activities are the most direct and important factors leading to the accumulation and loss of soil black carbon (BC), a detailed understanding of soil BC in different functional zones and reasonable soil management are the keys to determine whether soil is the carbon source or carbon sink. In this study, carbon concentrations and isotope compositions of black carbon (BC%, δ13CBC) and organic carbon (OC, δ13COC) were determined in topsoil from different functional zones (roadside grass verges, parks, residential areas, mines, arable lands, woodlands and wastelands) in urban and suburban of Beijing, China. The organic carbon (OC) content in soils of the urban area (averaging 1.67%) is higher than in suburban areas (averaging 1.05%). Black carbon is not evenly distributed across different functional zones, but is more concentrated and variable in urban areas (0.11–2.43%, averaging 0.73%) than in suburban areas (0.03–0.70%, averaging 0.18%). The ratios of BC% to OC% in suburban areas (0.04–0.40) are smaller than in urban areas (0.15–0.98). The δ13CBC of topsoil (–26.35…–20.85‰) reflects that coal combustion has a strong impact on soil BC accumulation in Beijing. The carbon isotope differences between OC and BC of the suburban and urban topsoils are positive (averaging +0.56‰) and negative (averaging –0.41‰), respectively. This suggests that urban areas are seriously influenced by human activities which lead to a large amount of fossil fuel combustion, but suburban areas have received a uniform deposition of atmospherically transported finer BC aerosols.

Improved Simulations of Global Black Carbon Distributions by Modifying Wet Scavenging Processes in Convective and Mixed‐Phase Clouds

AbstractIn‐cloud wet scavenging dominates the wet removal of aerosols in the atmosphere, but is not well represented in climate models. Aircraft measurements of black carbon (BC) concentrations suggest that models commonly overestimate BC concentrations in the upper troposphere of the tropics by more than one order of magnitude but underestimate BC burdens in polar latitudes. In this study, we improved the in‐cloud wet scavenging parameterizations for convective clouds and mixed‐phase clouds to better characterize BC abundances in the remote atmosphere (remote oceans and polar regions) with a global model, CAM5‐ATRAS2. The modified wet scavenging processes in the model achieved a more realistic simulation of BC concentrations over both the tropics and the Arctic. The new, unified scheme for vertical transport and wet removal during deep convection generally reproduced the observed low mixing ratios (about 0.1 ng kg−1) of BC in the middle and upper troposphere over the tropics, and the Wegener–Bergeron–Findeisen process (WBF) lowered the wet removal efficiency of BC from mixed‐phase clouds and consequently increased BC burdens in the Arctic by about a factor of 2. The BC direct radiative forcings increased by 20% globally (from 0.26 to 0.31 W m−2), and more importantly by a factor of 2 in the Arctic (from 0.09 to 0.18 W m−2). Our results indicated that good agreement between modeled and observed BC concentrations could be obtained in the remote atmosphere without requiring the relatively short global BC lifetime (∼4 days) suggested by previous studies.

Direct measurements of black carbon fluxes in central Beijing using the eddy covariance method

Abstract. Black carbon (BC) forms an important component of particulate matter globally, due to its impact on climate, the environment and human health. Identifying and quantifying its emission sources are critical for effective policymaking and achieving the desired reduction in air pollution. In this study, we present the first direct measurements of urban BC fluxes using eddy covariance. The measurements were made over Beijing within the UK-China Air Pollution and Human Health (APHH) winter 2016 and summer 2017 campaigns. In both seasons, the mean measured BC mass (winter: 5.49 ng m−2 s−1, summer: 6.10 ng m−2 s−1) and number fluxes (winter: 261.25 particles cm−2 s−1, summer: 334.37 particles cm−2 s−1) were similar. Traffic was determined to be the dominant source of the BC fluxes measured during both seasons. The total BC emissions within the 2013 Multi-resolution Emission Inventory for China (MEIC) are on average too high compared to measured fluxes by a factor of 58.8 (winter) and 47.2 (summer). Only a comparison with the MEIC transport sector shows that emissions are also larger (factor of 37.5 in winter and 37.7 in summer) than the measured flux. Emission ratios of BC ∕ NOx and BC ∕ CO are comparable to vehicular emission control standards implemented in January 2017 for gasoline (China 5) and diesel (China V) engines, indicating a reduction of BC emissions within central Beijing, and extending this to a larger area would further reduce total BC concentrations.

Indoor black carbon and brown carbon concentrations from cooking and outdoor penetration: insights from the HOMEChem study.

Particle emissions from cooking are a major contributor to residential indoor air pollution and could also contribute to ambient concentrations. An important constituent of these emissions is light-absorbing carbon, including black carbon (BC) and brown carbon (BrC). This work characterizes the contributions of indoor and outdoor sources of BC and BrC to the indoor environment by concurrently measuring real-time concentrations of these air pollutants indoors and outdoors during the month-long HOMEChem study. The median indoor-to-outdoor ratios of BC and BrC during the periods of no activity inside the test house were 0.6 and 0.7, respectively. The absorption Ångström exponent was used to characterize light-absorbing particle emissions during different activities and ranged from 1.1 to 2.7 throughout the campaign, with the highest value (indicative of BrC-dominated emissions) observed during the preparation of a simulated Thanksgiving Day holiday style meal. An indoor BC exposure assessment shows that exposure for an occupant present in the kitchen area was ∼4 times higher during Thanksgiving Day experiments (primarily due to candle burning) when compared to the background conditions.

Indoor-outdoor relationships of airborne nanoparticles, BC and VOCs at rural and urban preschools.

Health risks caused by exposure to black carbon (BC) and nanoparticles (NP) are well studied, although no standard currently exists for them worldwide. Exposure to children may lead to serious health effects due to their increased vulnerability and longer time spend inside the classrooms, making it important to assess the factors that affect air quality in preschools. Thus, this work aims to evaluate indoor-outdoor (I/O) relationships of NPs in the 10-420nm range, BC and volatile organic compounds (VOCs) at rural and urban preschools (aged 3-5 years) between May 2016 and July 2017. Factorial analysis was applied to identify the possible emission sources. Prior communalities were estimated by the squared multiple correlations with all other variables. We used the varimax rotation method and the criterion for factor selection was the number of eigenvalues greater than one. Results indicate that BC and NP were 4- and 3.2-times higher in urban outdoor caused by traffic emissions, respectively. Highest concentrations occurred during rush hours and during the pickup time of children. In urban school, BC was directly related to accumulation mode (N49-205), while in the rural area, BC was related to local traffic and particles from pulp industries in the regional background. Nucleation mode (N11-36) was related to traffic emissions in urban school, while in the rural school was related with secondary formation of particles. Mean I/O ratios of BC and NP in the urban (0.54; 0.51) and rural (0.71; 0.91) schools, respectively, suggested that their higher concentrations occurred in outdoors. VOCs were higher indoor in urban (I/O=1.97) and rural (I/O=2.22) sites, indicating these pollutants are generated inside, regardless of urban or rural sites. These findings suggest the necessity of improving ventilation and commuting styles to lower the exposure of children to air pollutants in and around school environments.

Characteristics and potential sources of black carbon particles in suburban Nanjing, China

As an important species of ambient fine particles, black carbon (BC) has significant adverse effects on air quality, human health and climate. This work reports results of one-year measurement of BC conducted in northern suburb of Nanjing, China from December 2017 to November 2018. Annual mean BC concentration was determined to be 2.78 μg/m³. BC concentration presented a “U” shape from December to November, lowest in summer and highest in winter. Nighttime BC concentration on average was higher than it in daytime, indicating heavier influence of meteorology than emissions. Diurnal pattern revealed that besides a clear emission-induced morning peak, meteorology played a more important role in governing BC changes in the rest of the day. Influences of meteorological factors on BC were in an order of boundary layer height, wind speed, temperature and relative humidity (RH), and further Granger causality analysis verified that the first three factors were indeed Granger causes of BC, while RH was not. Based on the diagnostic mass ratios of BC to CO, NO2 and SO2, as well as their correlation coefficients, we inferred that diesel vehicles rather than gasoline vehicles were the major BC emission source in suburban Nanjing; contributions from industry coal combustion were relatively less important. Back trajectory and potential source contribution analyses showed that regional rather than long-range transported air parcels led to the BC pollution in this site. Our findings provide useful insights into the reductions of BC and air pollution in this and similar atmospheric environments.

Characteristics of MERRA-2 black carbon variation in east China during 2000–2016

The spatial-temporal distributions, historical trends and affecting factors of black carbon (BC) concentration both for the surface and atmospheric column in East China (110°E ~ 123°E, 23°N ~ 42°N) during 2000–2016 were investigated through MERRA-2 (Modern-era Retrospective Analysis for Research and Applications, Vision2) reanalysis data. Although a little overestimate at most inland stations and underestimate at most coastal ones, BC concentrations of MERRA-2 generally presented a good correlation (R = 0.83) compared with 598 monthly samples from ground-based observations at 14 stations. From the long-term records, the variation characteristics of BC surface concentration and column density over East China can be summarized as follow: The overall annual mean of BC surface concentration, column density and the concentration ratio of surface BC and PM2.5 (BC/PM2.5) over East China were 3.41 μg m−3, 3.78 mg m−2 and 8.71%, respectively. The highest annual mean (~6.00 μg m−3) and the fastest growth rate (~0.06 μg m−3•a−1) of surface concentration were both shown in the region of Beijing-Tianjin-Hebei (BTH) and Henan area. The seasonal mean BC surface concentrations of this region were between 5.00 and 9.00 μg m−3, with the highest in winter and the lowest in summer. As to column density, the highest annual mean (~6.00 mg m−2) and the fastest growth rate (~0.02 mg m−2•a−1) appeared in BTH and the border area of Hebei, Henan and Shandong. Unlike the surface concentration, the high-density center moved toward south and extended its coverage from summer to winter, but shrunk to north from winter to summer. The region of relatively high (14.00%–16.00%) BC/PM2.5 ratio was over BTH area and central Shanxi area, while the lowest (2.00%–6.00%) regions were in part of Inner Mongolia and south coastal area. The yearly BC concentration increased rapidly since 2000 and reached the peak in 2007. It decreased obviously in the south part of East China during 2008-2016. The BC/PM2.5 ratios experienced a “increase-decrease-increase” variation, with the maximum and minimum in 2005 and 2010, respectively.

Effect of suspended particles with different grain sizes on the bioaccumulation of PAHs by zebrafish (Danio rerio).

The physicochemical characteristics are different for suspended particles (SPS) with different sizes in rivers. Here, we studied the effect of SPS (1 g L-1) with three different sizes (63-106 μm, 20-63 μm, and <20 μm) on the bioaccumulation of deuterated polycyclic aromatic hydrocarbons (phenanthrene-d10, anthracene-d10, fluoranthene-d10 and pyrene-d10) in zebrafish using passive dosing devices to maintain the freely dissolved concentrations of PAHs-d10 constant in water. The results showed that all the three grain size SPS could be ingested by zebrafish, and there was no significant difference in the amount of ingested SPS among the three grain sizes. The concentrations (lipid-normalized or not) of PAHs-d10 in zebrafish were promoted in the presence of the three different size SPS, and the PAH-d10 concentrations in zebrafish increased with decreasing particle size. Compared with the systems without SPS, the lipid-normalized concentrations of PAHs-d10 increased by 12%-72%, 34%-130%, and 60%-196%, respectively in zebrafish in systems with 63-106 μm, 20-63 μm, and <20 μm of SPS after exposure for 20 h. The stronger effect of SPS with smaller grain sizes was probably due to their lower organic carbon content, lower ratio of black carbon to organic carbon content, smaller particle size, and higher dissolved organic matter contents, which could promote the desorption of PAHs-d10 from ingested SPS and bioaccessibility of PAHs-d10 to zebrafish. This study suggests that in addition to SPS concentration, the suspended particle size should be considered in ecological risk assessment for hydrophobic organic compounds in aquatic environment.

Impact of Outdoor Air Pollution on Indoor Air Quality in Low-Income Homes during Wildfire Seasons.

Indoor and outdoor number concentrations of fine particulate matter (PM2.5), black carbon (BC), carbon monoxide (CO), and nitrogen dioxide (NO2) were monitored continuously for two to seven days in 28 low-income homes in Denver, Colorado, during the 2016 and 2017 wildfire seasons. In the absence of indoor sources, all outdoor pollutant concentrations were higher than indoors except for CO. Results showed that long-range wildfire plumes elevated median indoor PM2.5 concentrations by up to 4.6 times higher than outdoors. BC, CO, and NO2 mass concentrations were higher indoors in homes closer to roadways compared to those further away. Four of the homes with mechanical ventilation systems had 18% higher indoor/outdoor (I/O) ratios of PM2.5 and 4% higher I/O ratios of BC compared to other homes. Homes with exhaust stove hoods had PM2.5 I/O ratios 49% less than the homes with recirculating hoods and 55% less than the homes with no stove hoods installed. Homes with windows open for more than 12 hours a day during sampling had indoor BC 2.4 times higher than homes with windows closed. This study provides evidence that long-range wildfire plumes, road proximity, and occupant behavior have a combined effect on indoor air quality in low-income homes.

Deposition of Organic and Black Carbon: Direct Measurements at Three Remote Stations in the Himalayas and Tibetan Plateau

AbstractCarbonaceous matter in the atmosphere has an important influence on climate change. Currently, the deposition of carbonaceous matter is one of the largest uncertainties in the climate system. This phenomenon is common in remote regions, such as the Himalayas and Tibetan Plateau. In this study, for the first time, we reported in situ measurements of wet and dry deposition rates of carbonaceous matter at three remote stations: Nam Co, Lulang, and Everest. The results showed that the annual wet deposition rates of water‐insoluble organic carbon (WIOC) and black carbon (BC) were 60.2 and 5.8 mg·m−2·year−1, 330 and 34.6 mg·m−2·year−1, and 47.0 and 2.6 mg·m−2·year−1 at the Nam Co, Lulang, and Everest stations, respectively. Seasonal variations in the wet deposition rates of WIOC and BC were controlled by precipitation amount and their atmospheric concentrations. In addition, the wet scavenging ratios of WIOC and BC at Nam Co Station were close to those observed in other remote areas. The total BC deposition at Nam Co Station (15.3 mg·m−2·year−1) was higher than that from chemical transport models, implying a dominant role of dry deposition of BC in the total deposition at this station and an urgent need to improve the aerosol deposition in models for the Himalayas and Tibetan Plateau. It was found that the deposition rates of carbonaceous matter in the Himalayas and Tibetan Plateau had large spatial variation; thus, high‐resolution models need to be applied in the future.

Black carbon and other light-absorbing impurities in snow in the Chilean Andes

Vertical profiles of black carbon (BC) and other light-absorbing impurities were measured in seasonal snow and permanent snowfields in the Chilean Andes during Austral winters 2015 and 2016, at 22 sites between latitudes 18°S and 41°S. The samples were analyzed for spectrally-resolved visible light absorption. For surface snow, the average mass mixing ratio of BC was 15 ng/g in northern Chile (18–33°S), 28 ng/g near Santiago (a major city near latitude 33°S, where urban pollution plays a significant role), and 13 ng/g in southern Chile (33–41°S). The regional average vertically-integrated loading of BC was 207 µg/m2 in the north, 780 µg/m2 near Santiago, and 2500 µg/m2 in the south, where the snow season was longer and the snow was deeper. For samples collected at locations where there had been no new snowfall for a week or more, the BC concentration in surface snow was high (~10–100 ng/g) and the sub-surface snow was comparatively clean, indicating the dominance of dry deposition of BC. Mean albedo reductions due to light-absorbing impurities were 0.0150, 0.0160, and 0.0077 for snow grain radii of 100 µm for northern Chile, the region near Santiago, and southern Chile; respective mean radiative forcings for the winter months were 2.8, 1.4, and 0.6 W/m2. In northern Chile, our measurements indicate that light-absorption by impurities in snow was dominated by dust rather than BC.

Quantifying the light absorption and source attribution of insoluble light-absorbing particles on Tibetan Plateau glaciers between 2013 and 2015

Abstract. The deposition of insoluble light-absorbing particles (ILAPs) on snow and ice surfaces can significantly reduce albedo, thereby accelerating the melting process. In this study, 67 ice samples were collected from seven glaciers located on the Tibetan Plateau (TP) between May 2013 and October 2015. The mixing ratios of black carbon (BC), organic carbon (OC), and mineral dust (MD) were measured with an integrating sphere/integrating sandwich spectrophotometer (ISSW) system, which assumes that the light absorption of MD is due to iron oxide (Fe). Our results indicate that the mass-mixing ratios of BC, OC, and Fe exhibit considerable variability (BC: 10–3100 ng g−1; OC: 10–17 000 ng g−1; Fe: 10–3500 ng g−1) with respective mean values of 220±400 ng g−1, 1360±2420 ng g−1, and 240±450 ng g−1 over the course of the field campaign. We observed that for wavelengths of 450–600 nm, the measured light absorption can be largely attributed to the average light absorption of BC (50.7 %) and OC (33.2 %). Chemical elements and selected carbonaceous particles were also analyzed for source attributions of particulate light absorption based on a positive matrix factorization (PMF) receptor model. Our findings indicate that on average, industrial pollution (33.1 %), biomass or biofuel burning (29.4 %), and MD (37.5 %) constitute the principal sources of ILAPs deposited on TP glaciers.

Interpretation of particle number size distributions measured across an urban area during the FASTER campaign

Abstract. Particle number size distributions have been measured simultaneously by scanning mobility particle sizers (SMPSs) at five sites in central London for a 1 month campaign in January–February 2017. These measurements were accompanied by condensation particle counters (CPCs) to measure total particle number count at four of the sites and Aethalometers measuring black carbon (BC) at five sites. The spatial distribution and inter-relationships of the particle size distribution and SMPS total number counts with CPC total number counts and black carbon measurements have been analysed in detail as well as variations in the size distributions. One site (Marylebone Road) was in a street canyon with heavy traffic, one site (Westminster University) was on a rooftop adjacent to the Marylebone Road sampler, and a further sampler was located at Regent's University within a major park to the north of Marylebone Road. A fourth sampler was located nearby at 160 m above ground level on the BT tower and a fifth sampler was located 4 km to the west of the main sampling region at North Kensington. Consistent with earlier studies it was found that the mode in the size distribution had shifted to smaller sizes at the Regent's University (park) site, the mean particle shrinkage rate being 0.04 nm s−1 with slightly lower values at low wind speeds and some larger values at higher wind speeds. There was evidence of complete evaporation of the semi-volatile nucleation mode under certain conditions at the elevated BT Tower site. While the SMPS total count and black carbon showed typical traffic-dominated diurnal profiles, the CPC count data typically peaked during night-time as did CPC∕SMPS and CPC∕BC ratios. This is thought to be due to the presence of high concentrations of small particles (2.5–15 nm diameter) probably arising from condensational growth from traffic emissions during the cooler night-time conditions. Such behaviour was most marked at the Regent's University and Westminster University sites and less so at Marylebone Road, while at the elevated BT Tower site the ratio of particle number (CPC) to black carbon peaked during the morning rush hour and not at night-time, unlike the other sites. An elevation in nucleation mode particles associated with winds from the west and WSW sector was concluded to result from emissions from London Heathrow Airport, despite a distance of 22 km from the central London sites.

Emissions performance of high moisture wood fuels burned in a residential stove

A study has been made of the effect of fuel moisture content on emissions from a wood burning domestic stove. Two fuel types were studied: beech which is a hardwood, and spruce which is a softwood. The moisture contents investigated were for a freshly felled wood, a seasoned wood and a kiln dried wood. The effect of the moisture measurement method was considered using a commercial electrical conductivity probe moisture meter which was compared with laboratory analysis by drying in an oven at 105 °C. It was shown that the probe can significantly underestimate the actual moisture content in certain cases. Correlations were made of the burning rate, the Emission Factors for the formation of gaseous and particulate pollutants as a function of the moisture content. We also studied the ratio of Black Carbon to Total Carbon (BC/TC) to obtain information on the organic content of the particles. The NOX emissions from this type of stove were only dependent on the fuel-nitrogen content and not on the moisture content.

Speciated online PM&amp;lt;sub&amp;gt;1&amp;lt;/sub&amp;gt; from South Asian combustion sources – Part 1: Fuel-based emission factors and size distributions

Abstract. Combustion of biomass, garbage, and fossil fuels in South Asia has led to poor air quality in the region and has uncertain climate forcing impacts. Online measurements of submicron aerosol (PM1) emissions were conducted as part of the Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) to investigate and report emission factors (EFs) and vacuum aerodynamic diameter (dva) size distributions from prevalent but poorly characterized combustion sources. The online aerosol instrumentation included a “mini” aerosol mass spectrometer (mAMS) and a dual-spot eight-channel aethalometer (AE33). The mAMS measured non-refractory PM1 mass, composition, and size. The AE33-measured black carbon (BC) mass and estimated light absorption at 370 nm due to organic aerosol or brown carbon. Complementary gas-phase measurements of carbon dioxide (CO2), carbon monoxide (CO), and methane (CH4) were collected using a Picarro Inc. cavity ring-down spectrometer (CRDS) to calculate fuel-based EFs using the carbon mass balance approach. The investigated emission sources include open garbage burning, diesel-powered irrigation pumps, idling motorcycles, traditional cookstoves fueled with dung and wood, agricultural residue fires, and coal-fired brick-making kilns, all of which were tested in the field. Open-garbage-burning emissions, which included mixed refuse and segregated plastics, were found to have some of the largest PM1 EFs (3.77–19.8 g kg−1) and the highest variability of the investigated emission sources. Non-refractory organic aerosol (OA) size distributions measured by the mAMS from garbage-burning emissions were observed to have lognormal mode dva values ranging from 145 to 380 nm. Particle-phase hydrogen chloride (HCl) was observed from open garbage burning and was attributed to the burning of chlorinated plastics. Emissions from two diesel-powered irrigation pumps with different operational ages were tested during NAMaSTE. Organic aerosol and BC were the primary components of the emissions and the OA size distributions were centered at ∼80 nm dva. The older pump was observed to have significantly larger EFOA than the newer pump (5.18 g kg−1 compared to 0.45 g kg−1) and similar EFBC. Emissions from two distinct types of coal-fired brick-making kilns were investigated. The less advanced, intermittently fired clamp kiln was observed to have relatively large EFs of inorganic aerosol, including sulfate (0.48 g kg−1) and ammonium (0.17 g kg−1), compared to the other investigated emission sources. The clamp kiln was also observed to have the largest absorption Ångström exponent (AAE = 4) and organic carbon (OC) to BC ratio (OC : BC = 52). The continuously fired zigzag kiln was observed to have the largest fraction of sulfate emissions with an EFSO4 of 0.96 g kg−1. Non-refractory aerosol size distributions for the brick kilns were centered at ∼400 nm dva. The biomass burning samples were all observed to have significant fractions of OA and non-refractory chloride; based on the size distribution results, the chloride was mostly externally mixed from the OA. The dung-fueled traditional cookstoves were observed to emit ammonium, suggesting that the chloride emissions were partially neutralized. In addition to reporting EFs and size distributions, aerosol optical properties and mass ratios of OC to BC were investigated to make comparisons with other NAMaSTE results (i.e., online photoacoustic extinctiometer (PAX) and off-line filter based) and the existing literature. This work provides critical field measurements of aerosol emissions from important yet under-characterized combustion sources common to South Asia and the developing world.

Perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) based composites organic battery

A new organic battery was fabricated using perylene-3,4,9,10-tetracarboxylic dianhydride organic semiconductor and copper chloride electrolyte. The perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) organic semiconductor based composites were synthesized for various contents of black carbon (BC). The structural properties of the PTCDA:BC composites were confirmed by XRD, FTIR, EDX and SEM analyses. The dielectric constants and alternating electrical conductivity (AC) of the composites were increased using BC dopant. The electrical properties of prepared batteries were by current-voltage characteristics. The open circuit voltage, Voc of the battery is increased from 0.17 V to 0.45 V, while the short circuit current, Isc is changed from 12 mA to 25 mA. The battery having PTCDA:BC (80.20) ratio exhibited a highest maximum power, Pmax of 3.08 mW.The obtained results indicate that PTCDA:BC composites based batteries can be used in micropower energy applications.

Black carbon, organic carbon, and co-pollutant emissions and energy efficiency from artisanal brick production in Mexico

Abstract. In many parts of the developing world and economies in transition, small-scale traditional brick kilns are a notorious source of urban air pollution. Many are both energy inefficient and burn highly polluting fuels that emit significant levels of black carbon (BC), organic carbon (OC) and other atmospheric pollutants into local communities, resulting in severe health and environmental impacts. However, only a very limited number of studies are available on the emission characteristics of brick kilns; thus, there is a need to characterize their gaseous and particulate matter (PM) emission factors to better assess their overall contribution to emissions inventories and to quantify their ecological, human health, and climate impacts. In this study, the fuel-, energy-, and brick-based emissions factors and time-based emission ratios of BC, OC, inorganic PM components, CO, SO2, CH4, NOx, and selected volatile organic compounds (VOCs) from three artisanal brick kilns with different designs in Mexico were quantified using the tracer ratio sampling technique. Simultaneous measurements of PM components, CO, and CO2 were also obtained using a sampling probe technique. Additional measurements included the internal temperature of the brick kilns, mechanical resistance of bricks produced, and characteristics of fuels employed. Average fuel-based BC emission factors ranged from 0.15 to 0.58 g (kg fuel)−1, whereas BC∕OC mass ratios ranged from 0.9 to 5.2, depending on the kiln type. The results show that both techniques capture similar temporal profiles of the brick kiln emissions and produce comparable emission factors. A more integrated inter-comparison of the brick kilns' performances was obtained by simultaneously assessing emissions factors, energy efficiency, fuel consumption, and the quality of the bricks produced.