Source Regions Of Black Carbon Research Articles

Seasonal transition of Black carbon aerosols over Qinghai-Tibet Plateau: Simulations with WRF-Chem

Black carbon (BC) particles over the Qinghai-Tibet Plateau (Q-TP), whether suspended in the air or deposited on snow, can affect snow melt and accelerate glacier retreat. Since BC over the Q-TP may originate from different regions, it is necessary to understand the transport mechanism of BC and then provide concentrations and spatial-temporal distributions of BC over Q-TP, in order to study its radiative and climatic effects. In this study, Weather Research and Forecasting model with Chemistry (WRF-Chem), with MIX emission inventory (a mosaic Asian anthropogenic emission inventory for the MICS-Asia and the HTAP projects), was used to study the BC transport from South Asia, one of the major BC source regions, to Q-TP in April (pre-monsoon season), July (summer monsoon season) and December (winter monsoon season). The model's ability to simulate the BC transport from South Asia to the Q-TP was firstly evaluate using various reanalysis data, including 2 m temperature, precipitation, 10 m wind speed and direction and BC concentration at surface. The simulated meteorological fields and seasonal distribution and variation of BC are generally in good agreement with reanalysis data. The model showed good performance in simulating transport of BC as well. Our study showed that during pre-monsoon season, BC aerosols accumulated in the foothills of the Himalayas and were transported to southern Q-TP and even Southeast Asia via dry and wet deposition and westerly winds below 200hpa. Although the cyclonic airflow, which was favorable to transport, prevailed in South Asia, slight BC aerosols would be transported to Q-TP through wet deposition due to the efficient wet scavenging by abundant precipitation during summer monsoon season. During winter monsoon season, the prevailing westerly winds at 500hpa would transport BC aerosols from South Asia to Q-TP by dry deposition. A sensitivity simulation using PKU emission inventory (Peking University's global BC emission inventory) was then conducted to investigate the impact of different emission inventory on the modeling results. It is shown that the simulations using the different BC emission inventories overall did not have significant impacts on spatial distributions of surface concentration and column burden during three studies seasons. However, the simulated BC concentrations and burden based on PKU were overall higher than that based on MIX, that is, main differences were found in the southern part of Q-TP (i.e. adjacent to South Asia), especially during pre-monsoon and winter monsoon seasons. The differences of mean BC surface concentration ranging from 0.1 to 1 μg/m3, and burden ranging from 0.1 to 1 mg/m2 due to both higher dry and wet deposition (0.1–2 μg/m2/s for dry deposition flux, and 0.1–3 μg/m2/s for wet deposition flux) during pre-monsoon. During winter monsoon seasons, relatively large differences (0–3 μg/m3 for concentration, and 0–2 mg/m2 for burden, and 0.1–3 μg/m2/s for dry deposition flux) were found in southern Q-TP.

Assessment of carbonaceous aerosols at Mukteshwar: A high-altitude (~2200 m amsl) background site in the foothills of the Central Himalayas

The present study examined the equivalent black carbon (eBC) mass concentrations measured over 10.5 years (September 2005–March 2016) using a 7-wavelength Aethalometer (AE-31) at Mukteshwar, a high-altitude and regional background site in the foothills of Indian central Himalayas. The total spectral absorption coefficient (babs) was divided into three categories: black carbon (BC) and brown carbon (BrC); fossil fuels (FF) and wood/biomass burning (WB/BB); and primary and secondary sources. At the wavelength of 370 nm, a significant BrC contribution (25 %) to the total babs is identified, characterized by a pronounced seasonal variation with winter (December–January-February) maxima (31 %) and post-monsoon (October and November) minima (20 %); whereas, at 660 nm, the contribution of BrC is dramatically less (9 %). Climatologically, the estimated BCFF at 880 nm ranges from 0.25 ± 0.19 μg m−3 in July to 1.17 ± 0.80 μg m−3 in May with the annual average of 0.67 ± 0.63 μg m−3, accounting for 79 % of the BC mass. The maximum BCFF/BC fraction reaches its peak value during the monsoon (July and August, 85 %), indicating the dominance of local traffic emissions due to tourism activities. Further, the highest BCWB concentration observed during pre-monsoon (March–May) suggests the influence of local forest fires along with long-range transported aerosols from the low-altitude plains. The increased contribution of BrC (26 % at 370 nm) and WB absorption (61 % at 370 nm) to the total absorption at the shorter wavelengths suggests that wood burning is one of the major sources of BrC emissions. Secondary BrC absorption accounts for 24 % [91 %] of the total absorption [BrC absorption] at 370 nm, implying the dominance of secondary sources in BrC formation. A trend analysis for the measured BC concentration shows a statistically significant increasing trend with a slope of 0.02 μgm−3/year with a total increase of about 22 % over the study period. A back trajectory-based receptor model, potential source contribution function (PSCF), was used to identify the potential regional source region of BC. The main source regions of BC are the northwest states of India in the IGP region and the northeast Pakistan region.

Origins of black carbon from anthropogenic emissions and open biomass burning transported to Xishuangbanna, Southwest China

Black carbon (BC) has importance regarding aerosol composition, radiative balance, and human exposure. This study adopted a backward-trajectory approach to quantify the origins of BC from anthropogenic emissions (BCAn) and open biomass burning (BCBB) transported to Xishuangbanna in 2017. Haze months, between haze and clean months, and clean months in Xishuangbanna were defined according to daily PM2.5 concentrations of >75, 35–75, and <35 µg/m3, respectively. Results showed that the transport efficiency density (TED) of BC transported to Xishuangbanna was controlled by the prevailing winds in different seasons. The yearly contributions to the effective emission intensity of BCAn and BCBB transported to Xishuangbanna were 52% and 48%, respectively. However, when haze occurred in Xishuangbanna, the average BCAn and BCBB contributions were 23% and 77%, respectively. This suggests that open biomass burning (BB) becomes the dominant source in haze months. Myanmar, India, and Laos were the dominant source regions of BC transported to Xishuangbanna during haze months, accounting for 59%, 18%, and 13% of the total, respectively. Furthermore, India was identified as the most important source regions of BCAn transported to Xishuangbanna in haze months, accounting for 14%. The two countries making the greatest contributions to BCBB transported to Xishuangbanna were Myanmar and Laos in haze months, accounting for 55% and 13%, respectively. BC emissions from Xishuangbanna had minimal effects on the results of the present study. It is suggested that open BB in Myanmar and Laos, and anthropogenic emissions in India were responsible for poor air quality in Xishuangbanna.

Source apportionment of black carbon over Delhi: A case study of extreme biomass burning events and Diwali festival

Present study investigates the temporal and diurnal variations of Black Carbon (BC) and quantifies the contribution of fossil fuel (BCff) combustion and biomass burning (BCbb) to the BC concentrations in Delhi using the Aethalometer model. The average BC mass concentration and Absorption Angstrom Exponent were 12.6 ± 8.2 μg/m3 (range: 1.73–37.0 μg/m3) and 1.30 ± 0.16 (range: 1.06–1.82), respectively. The average BCff and BCbb mass concentrations were 7.90 ± 4.98 μg/m3 (range: 1.13–19.98 μg/m3) and 4.73 ± 5.23 μg/m3 (range: 0.21–26.85 μg/m3), respectively. The contribution of BCbb was 31.15% and BCff was 68.85% to the overall BC concentration in the study period. The highest BCbb contribution, amounting to 52.04%, was found in the month of November (stubble burning season). The effect of Diwali firecrackers on BC concentrations was also investigated which was transient, lasted for few hours only. The probable major source regions of BC to the receptor site were Rajasthan, Gujarat, Punjab, Indo-Gangetic Plain and parts of Pakistan during monsoon season while Punjab, Haryana, and parts of Uttar Pradesh during post-monsoon season. The results revealed that the biomass burning activities in Punjab and Haryana contribute significantly to the Delhi's post-monsoon air pollution suggesting urgency to implement the carbonaceous aerosols emission abatement strategies over northern India.

Characteristics and Source Apportionment of Black Carbon in Chengdu

Black carbon (BC) was measured at Chengdu from December 1, 2017, to November 30, 2018, using a seven-channel aethalometer (AE-33). The variation characteristics of BC were obtained. BC sources were explored based on the aethalometer model and a hybrid single particle Lagrangian integrated trajectory model (Hysplit-4). The results showed the BC concentration was the highest in the winter (8.18 μg·m-3) with the monthly mean of 11.11 μg·m-3 peaking in December, followed by the spring (5.11 μg·m-3) and autumn (3.91 μg·m-3), and was the lowest in summer (3.28 μg·m-3) with the lowest monthly mean of 2.30 μg·m-3 in July. The annual average concentration of BC was 5.26 μg·m-3 with a standard deviation of 4.27 μg·m-3. The diurnal variations of BC showed typical bimodal patterns in four seasons mainly due to the influence of the boundary layer and traffic rush. The source apportionment of BC showed that the liquid fuel (e.g., vehicle emission) had higher contribution to total BC concentration during all seasons (ranging from 69% in winter to 82% in summer) than solid fuel (e.g., coal and biomass combustion). The contribution of liquid fuel to the total BC was higher in summer, while solid fuel had a higher contribution in winter. The diurnal cycles of BC source apportionment demonstrated that the contribution of liquid fuel increased in the rush hours. The results of potential source contribution function and concentration weighted trajectory showed that the potential sources of BC in Chengdu were slightly different in different seasons and were mainly affected by the different air mass sources. However, the main potential source regions were the surrounding areas of Chengdu and the areas between Chengdu and Chongqing (the Chuanyu City group). The mass contribution to the BC in Chengdu was high in the region where liquid fuel most affected the total BC. Additionally, the southern part of Shaanxi and the southern part of Gansu were also potential sources of BC, and in Summer, some regions in Guangxi and Guizhou could become the source regions of BC in Chengdu.

Investigation of aerosol black carbon over semi-urban and urban locations in south-western India

Abstract Temporal evolution of the ‘dual-spot’ 7-channel Aethalometer measured black carbon (BC) aerosols over different time scales, their potential source regions and impact of meteorology on BC mass are analyzed using observational data at Ahmednagar College (AC-Ahmednagar), Ahmednagar and Indian Institute of Tropical Meteorology, Pashan (IITM-Pashan), Pune. Results reveal well defined bimodal diurnal pattern in BC mass; one in morning (07:00-09:00 LT) and another in evening (around 20:00 LT) at both sites. This is quite consistent with seasonally changing BC mass and is the combined effects of variations in anthropogenic emissions, meteorology and associated atmospheric boundary layer (ABL) dynamics. BC mass concentration at AC-Ahmednagar and IITM-Pashan varied from 1.8 to 49.0 μg m−3 (annual mean 13.8 ± 10.4 μg m−3) and 0.7–21.6 μg m−3 (annual mean 3.9 ± 2.8 μg m−3) respectively. Annual BC cycle at AC-Ahmednagar, IITM-Pashan, Delhi and Xian (China) appears to be similar. However, BC mass at AC-Ahmednagar being of the same order to that reported at Delhi (India) and Xi'an (China), it is about 3.5 times higher than at IITM-Pashan. The present work, further, demonstrates prominent role exerted by surface temperature (T) and relative humidity (RH) in modulating BC mass. Occurrence of high ΔBC (BC370 nm – BC880 nm) and absorption Angstrom exponent (AAE) are indicative of enhanced absorption in near-UV and low-visible wavelengths attributed to the presence of biomass burning and light absorbing particulate matter. The back-trajectory cluster and concentrated weighted trajectory (CWT) analysis identifies four distinct potential BC source regions at the present receptor sites.

Temporal variation and source identification of black carbon at Lin’an and Longfengshan regional background stations in China

Black carbon (BC) is a component of fine particulate matter (PM2.5), associated with climate, weather, air quality, and people’s health. However, studies on temporal variation of atmospheric BC concentration at background stations in China and its source area identification are lacking. In this paper, we use 2-yr BC observations from two background stations, Lin’an (LAN) and Longfengshan (LFS), to perform the investigation. The results show that the mean diurnal variation of BC has two significant peaks at LAN while different characteristics are found in the BC variation at LFS, which are probably caused by the difference in emission source contributions. Seasonal variation of monthly BC shows double peaks at LAN but a single peak at LFS. The annual mean concentrations of BC at LAN and LFS decrease by 1.63 and 0.26 μg m–3 from 2009 to 2010, respectively. The annual background concentration of BC at LAN is twice higher than that at LFS. The major source of the LAN BC is industrial emission while the source of the LFS BC is residential emission. Based on transport climatology on a 7-day timescale, LAN and LFS stations are sensitive to surface emissions respectively in belt or approximately circular area, which are dominated by summer monsoon or colder land air flows in Northwest China. In addition, we statistically analyze the BC source regions by using BC observation and FLEXible PARTicle dispersion model (FLEXPART) simulation. In summer, the source regions of BC are distributed in the northwest and south of LAN and the southwest of LFS. Low BC concentration is closely related to air mass from the sea. In winter, the source regions of BC are concentrated in the west and south of LAN and the northeast of the threshold area of stot at LFS. The cold air mass in the northwest plays an important role in the purification of atmospheric BC. On a yearly scale, sources of BC are approximately from five provinces in the northwest/southeast of LAN and the west of LFS. These findings are helpful in reducing BC emission and controlling air pollution.

Two distinct patterns of seasonal variation of airborne black carbon over Tibetan Plateau

Airborne black carbon (BC) mass concentrations were measured from November 2012 to June 2013 at Ranwu and Beiluhe, located in the southeastern and central Tibetan Plateau, respectively. Monthly mean BC concentrations show a winter (November–February) high (413.2ngm−3) and spring (March–June) low (139.1ngm−3) at Ranwu, but in contrast a winter low and spring high at Beiluhe (204.8 and 621.6ngm−3, respectively). By examining the meteorological conditions at various scales, we found that the monthly variation of airborne BC over the southeastern Tibetan Plateau (TP) was highly influenced by regional precipitation and over the hinterland by winds. Local precipitation at both sites showed little impact on the seasonal variation of airborne BC concentrations. Potential BC source regions are identified using air mass backward trajectory analysis. At Ranwu, BC was dominated by the air masses from the northeastern India and Bangladesh in both winter and spring, whereas at Beiluhe it was largely contributed by air masses from the south slope of Himalayas in winter, and from the arid region in the north of the TP in spring. The winter and spring seasonal peak of BC in the southern TP is largely contributed by emissions from South Asia, and this seasonal variation is heavily influenced by the regional monsoon. In the northern TP, BC had high concentrations during spring and summer seasons, which is very likely associated with more efficient transport of BC over the arid regions on the north of Tibetan Plateau and in Central Asia. Airborne BC concentrations at the Ranwu sampling site showed a significant diurnal cycle with a peak shortly after sunrise followed by a decrease before noon in both winter and spring, likely shaped by local human activities and the diurnal variation of wind speed. At the Beiluhe sampling site, the diurnal variation of BC is different and less distinct.

Using an explicit emission tagging method in global modeling of source‐receptor relationships for black carbon in the Arctic: Variations, sources, and transport pathways

AbstractWe introduce an explicit emission tagging technique in the Community Atmosphere Model to quantify source‐region‐resolved characteristics of black carbon (BC), focusing on the Arctic. Explicit tagging of BC source regions without perturbing the emissions provides a physically consistent and computationally efficient approach to establish source‐receptor relationships and transport pathways. Our analysis shows that the contributions of major source regions to the global BC burden are not proportional to the respective emissions due to strong region‐dependent removal rates and lifetimes, while the contributions to BC direct radiative forcing show a near‐linear dependence on their respective contributions to the burden. Arctic BC concentrations, deposition, and source contributions all have strong seasonal variations. Eastern Asia contributes the most to the wintertime Arctic BC burden, but has much less impact on lower‐level concentrations and deposition. Northern Europe emissions are more important to both surface concentration and deposition in winter than in summer. The largest contribution to Arctic BC in the summer is from Northern Asia. Although local emissions contribute less than 10% to the annual mean BC burden and deposition within the Arctic, the per‐emission efficiency is much higher than for non‐Arctic sources. The interannual variability (1996–2005) due to meteorology is small in annual mean BC burden and radiative forcing but is significant in yearly seasonal means over the Arctic. When a slow aging treatment of BC is introduced, the increase of BC lifetime and burden is source dependent. Global BC forcing‐per‐burden efficiency also increases primarily due to changes in BC vertical distributions.

The identification of source regions of black carbon at a receptor site off the eastern coast of China

The black carbon (BC) mass concentration and the particle chemical compositions were continually measured at Changdao Island, which is a regional receptor site off the eastern coast of China. This island is in the transport passage of the continental outflow to the Pacific Ocean when the East Asia monsoon prevails in the winter and spring. The campaign period was for March and April 2011, which corresponded to heating and non-heating periods in northern China. The effect of BC emission source regions on BC measured at Changdao Island between the heating and non-heating periods was determined by integrating the total potential source contribution function (TPSCF) model with the new monthly emission inventory in 2010 and the fire counts retrieved from MODIS during the campaign. BC concentrations were determined to be highest for similar times of day for both the heating and non-heating periods: 4.27 μg m−3 at 8:00 AM and 3.06 μg m−3 at 9:00 AM, respectively. The probable source regions for BC were primarily located in Shandong and Jiangsu provinces (and in other neighboring provinces) for both periods. However, the source regions for the non-heating period extended more to the north and southwest than those of the heating period. TPSCF values were correlated with the emission rates from residential, industry, transportation, and power plants sources in the anthropogenic emission inventory. This correlation provides an indirect and qualitative process to verify the emission inventory. In the heating period, the predominant source was the residential source in the emission inventory, and this source had a significant effect on the BC concentration. The differing peak concentrations between the two periods may be observed because of the increased residential heating during the heating period, which suggested that the measures employed by the government and environmental managers to reduce the emissions of pollutants should be stricter in the identified source regions during the heating period.

Aerosol absorption over Bay of Bengal during winter: Variability and sources

Abstract Measurements of black carbon (BC) mass concentration were made over the Bay of Bengal (BoB) during the period of 27 December 2008–29 January 2009. BC mass concentration is highest over the Coastal-BoB (5.1 ± 3.0 μg m −3 ) and is more than a factor of two higher than the South-BoB (2.5 ± 1.4 μg m −3 ). The source regions of BC over the study region is identified using the Total Potential Source Contribution Function (TPSCF) analysis. The probable source regions over the Coastal-BoB and North-BoB (India, Indo-Gangetic plain, Pakistan, Afghanistan) are found to be distinctly different than that over the East-BoB and South-BoB (mostly from southeast Asia). The spectral distribution of absorption coefficients suggested similar source types of BC present over the entire BoB, with significant contribution of absorbing aerosols from the sources other than fossil fuel burning. Our results suggest that the entire BoB remains dominantly influenced by aerosols emitted from biomass/biofuel burning during winter. Single scattering albedo (SSA) is found to vary in the range of 0.63–0.70 over different parts of BoB with the lowest value over Coastal-BoB and the highest value over South-BoB. SSA values observed in the present study are the lowest ever reported over the BoB in the last decade indicating highest concentration of absorbing aerosols over the BoB during winter. The present work and the results obtained will have strong implications while investigating the effect of anthropogenic aerosols over marine environment, and in estimating the spatiotemporal variation of aerosol radiative impact.

Continuous measurements of aerosol physical parameters at the Mt. Cimone GAW Station (2165 m asl, Italy)

Particle size distribution in the range 0.3 < D p ≤ 20 μm, has been analysed from August 2002 to July 2006 at the GAW Station of Mt. Cimone (44.10 N, 10.42 E; 2165 m asl) in the northern Italian Apennines. The seasonal aerosol number size distribution, characterized by a bimodal shape, showed a behaviour typical for background conditions, characterized by highest values in summer and lowest in winter. The seasonal and diurnal variations of the larger accumulation mode (0.3 < D p ≤ 1 μm average values: 26.15 cm − 3 ) and the coarse mode (1 < D p ≤ 20 μm, average value: 0.17 cm − 3 ) particle number concentrations ( N 0.3–1 and N 1–20, respectively) exhibited a seasonal cycle with the highest values in spring–summer and the lowest value in autumn–winter. Except in winter, N 0.3–1 showed a clear diurnal variation with high values during day-time. N 1–20 showed a less marked diurnal variation (but with higher variability), suggesting the influence of non-continuous sources of coarse particle (i.e. Saharan dust events). Since July 2005, continuous measurement of black carbon (BC) concentrations was also available at the measurement site. On average low BC concentrations were recorded (average value: 0.28 μg m − 3 ) even if a few events of high concentrations were recorded both in warm and cold season. Apart from wet scavenging processes which strongly affected aerosol concentrations, combined analysis of N 0.3–1, BC, meteorological parameters and air mass back-trajectories, suggests that the transport of polluted air masses from the lower troposphere (by local, regional or long-range transport) represents an important mechanism favouring N 0.3–1 and BC increases at Mt. Cimone. In particular, a trajectory statistical analysis for the period July 2005–July 2006 allowed the identification of the main source regions of BC and N 0.3–1 for Mt. Cimone: north Italy, west Europe and east Europe.