Diurnal Variation Of Black Carbon Research Articles

Spatiotemporal variations and source on black carbon over Chongqing, China: Long-term changes and observational experiments

Black carbon (BC), as a critical light-absorbing constituent within aerosols, exerts profound effects on atmospheric radiation balance, climate, air quality and human health, etc. And it is also a long-standing focus in rapidly developing megacities. So, this study primarily focuses on investigating the variation characteristics and underlying causes of BC in Chongqing (31,914,300 population), which is one of the municipalities directly under the central government of China, serving as a pivotal economic hub in southwest China. Utilizing MERRA-2 reanalysis data, we examined the long-term changes of atmospheric BC over Chongqing 20 years (from 2002 to 2021). Moreover, BC mass concentration observations were conducted using an Aethalometer (AE-33) from March 15 to June 14, 2021 in Liangping District, Chongqing. The statistical analysis over the last 20 years reveals an annual mean BC concentration in Chongqing of 3.42 ± 0.20 μg/m3, exhibiting growth from 2002 to 2008, followed by a decline from 2008 to 2021. Monthly concentration displays a “U-shaped” trend, with the lowest values occurring in summer and the highest in winter. Due to topographical and meteorological influences, local emissions primarily contribute to BC pollution, characterized by a spatial distribution pattern of high in the west and low in the east. Ground observation indicates a distinct dual-peaked pattern in the diurnal variation of BC, with peak concentrations aligning with periods of high traffic emissions. The variation in BC is significantly influenced by meteorological conditions (wind, temperature, atmospheric boundary layer) and local pollution sources (predominantly traffic). Furthermore, extreme events analysis suggests that local emissions and regional transport (with higher contributions from Chongqing and the Sichuan Basin) predominantly contributed to BC pollution. This study effectively makes up for the deficiency in analyzing the distribution and sources of BC pollution in Chongqing, providing valuable scientific insights for the atmospheric environment of megacities.

Black carbon and size-segregated elemental carbon, organic carbon compositions in a megacity: a case study for Istanbul

In this study, black carbon (BC), particulate matter (PM), nitrogen oxides (NOx), and sulphur dioxide (SO2) were monitored between May 2019 and February 2020. During this sampling period, size-segregated particle samples were collected by a high-volume cascade impactor, once a week. Elemental carbon (EC) and organic carbon (OC) were investigated on the size-segregated particles. The study was carried out at Esenler district of Istanbul. Main sources in the vicinity of the sampling area are Central Coach Station of Istanbul, residential buildings, small-scale industrial facilities, and O-1 and O-2 highway connection. The average BC concentration was 2763 ± 1974 ng/m3. PM10 and PM2.5 concentrations were 38.2 ± 17.4 and 21.5 ± 12.4 μg/m3, respectively. BC comprised 12.8% and 7.2% of PM2.5 and PM10, respectively. Diurnal variation of BC had a similar trend with NO2 concentrations, which showed peak concentrations during rush hours. BC had high Pearson correlation coefficients with NO, NO2, and PM2.5. The geographical position of possible emission sources was estimated through conditional probability function. The Central Coach Station of Istanbul had the highest geographical possibility for BC sources. EC and OC exhibited bimodal size distribution. The coarse mode peak was at 0.95–1.5-μm size bin for OC, whilst it was at 1.5–3-μm size bin for EC. Since EC and BC exhibit the same origin with different measurement principles, we concluded that resuspension of road dust also contributed ambient BC concentrations.

Cross-Sectional View of Atmospheric Aerosols over an Urban Location in Central India

ABSTRACTSurface, column and vertically resolved variations of physical and optical properties of atmospheric aerosol over Hyderabad, a tropical urban location in central India are explored on the basis of ground based and satellite retrieved data. Annual mean aerosol optical depth (τ) observed with Microtops sun-photometer is 0.61 ± 0.07 and seasonally it varied from 0.71 ± 0.06 in pre-monsoon to 0.55 ± 0.05 in winter. Aerosol types are categorized based on Angstrom exponent (α) and τ relations; revealed that the study region is dominated by mixed type (MT) aerosol followed by urban/industrial aerosols under high τ (HUI) category. A consistent diurnal variation of black carbon (BC) is observed irrespective of seasonal variation with annual BC mass concentration is found to be 9.7 ± 1.9 µg m–3. During Telangana Survey day, which was the least pollutant day showed a reduction of 75% BC concentration during day time in comparison to five years average values, indicating the influence of anthropogenic effect over Hyderabad. Vertical information’s on aerosol are analyzed using Cloud Aerosol Lidar Pathfinder Satellite Observations (CALIPSO) and ground based Lidar (LAMP) data. LAMP data analysis shows a significant elevated aerosol layer up to 4 km during pre-monsoon while aerosols are confined below 3 km during post-monsoon and winter. Long term CALIPSO observations revealed that during post-monsoon to winter, the study area is dominated (~60%) by ‘urban’ aerosol; while during pre-monsoon period ~75% of the aerosol type belongs to ‘dusty mix’ category. A decline in short wave flux at the top of the atmosphere (0.66 Wm–2 yr–1) is observed, as revealed by long term Clouds and Earths Radiant Energy System (CERES) data analysis with higher decline rate observed in winter (1 Wm–2 yr–1) followed by pre-monsoon (0.8 Wm–2 yr–1).

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.

한반도 수도권 및 준 수도권 지역의 블랙 카본 측정 연구: 한-미 협력 국내 대기질 공동 조사 연구 (KORea-US Air Quality Study, KORUS-AQ) 예비캠페인 기간을 중심으로

Abstract Black carbon(BC) aerosols were monitored at the KIST site(37.603°N, 127.046°E) and Cheonan-KOREATECH site(36.766°N, 127.281°E) during the pre KORea-US Air Quality Study(KORUS-AQ) campaign using a couple of Muliti Angle Absorption Photometers(MAAP). BC mass concentrations were presented as 2.14μg/m± 3 1.06 and 0.94±0.60 μg/m 3 at KIST site(Seoul) and KOREATECH site(Cheonan), respectively. BC mass concentrations measured at KIST and KOREATECH sites from 22:00 on May 22 to 12:00 on May 23, 2015 showed 80% and 72% higher than average BC mass concentrations measured during campaign period, respectively. It indicates both sites could be influenced by a remote source. Similar patterns of BC concentrations between two sites from 20:00 to 24:00 on June 6, 2015 implies that the BC could be transported into both sites and then be stagnant inside the Korean Peninsula. Diurnal variation of BC in weekdays and weekends were also presented for the KIST and KOREATECH sites. Morning rush hour peak was observed at KIST site located in metropolitan area though no distinct morning rush hour peak was not observed at KOREATECH site located in a suburban area. This study revealed transport pathways of BC near the Korean Peninsula using back-trajectory analysis of BC measured both in a metropolitan area and in a suburban area.

Physical and optical properties of aerosols in a free tropospheric environment: Results from long-term observations over western trans-Himalayas

Simultaneous and collocated estimates of near-surface mass concentration of black carbon (BC), number size distribution (NSD) and total number concentration (NT) of composite aerosols, columnar spectral aerosol optical depth (AOD) and local meteorological parameters were made from Aug 2009 to July 2012 at the high altitude (4520 m amsl), remote location Hanle in western trans-Himalayas. Even though all the aerosol parameters remain quite low, large annual variations are seen in the monthly mean values of BC (25 ng m−3–181 ng m−3), total number concentrations of composite aerosols (628 cm−3–1500 cm−3) and AOD (0.05–0.16). Size segregated correlation analysis reveals that the BC mass contributes significantly to the size range of 200–400 nm of the submicron aerosol size spectra. The diurnal variation of BC mostly has been dampened; yet seems to be prominent during spring, showing the presence of weak boundary layer dynamics. In contrast, the diurnal fluctuations in total number concentration have been mostly controlled by the new particle formation events, leading to bursts of large concentrations of ultrafine particles, which subsequently undergo coagulation. Spectral dependence of AOD also shows large monthly variations, with the Angstrom exponent varying from ∼0.52 to 1.3, with a mean value of ∼0.95 ± 0.21. The vertical distribution of extinction coefficients, obtained from CALIPSO data, indicates the presence of elevated aerosol layers, attributed mainly to the influence of long range transport of aerosols from the west Asian and Indian desert region.

Seasonal characteristics of black carbon aerosols over a high altitude station in Southwest India

Black carbon (BC) aerosol mass concentrations were measured using an Aethalometer at high altitude station Sinhagad, a rural location in south-west India, in the pre-monsoon and post-monsoon seasons during 2009–10. Mean BC concentration was about 67% less during pre-monsoon than that during post-monsoon. During post-monsoon, the surface boundary layer is generally shallow resulting in the trapping of pollutants in a lesser volume near the surface which lead to higher BC concentrations than of pre-monsoon which experiences high convective activity and thereby dispersion of aerosols near the surface. Diurnal variation of BC during pre-monsoon was attributed to the changes in the local boundary layer as well as to the certain anthropogenic activities near the sampling site. BC aerosol mass concentration showed good correlation with temperature gradient and relative humidity in pre-monsoon. However in post-monsoon, a weak correlation was observed with temperature gradient whereas with relative humidity, a good correlation was observed during night hours only. The wind speed and direction using NCEP/NCAR reanalysis data showed a possible transport from Pune city as well as from N/NE Indian regions during post-monsoon. BC also showed good correlation with other anthropogenic components of aerosols like NssSO4, NssK, NO3, and NH4; indicating a possible common source for them.

Analysis of Diurnal and Seasonal Variation of Submicron Outdoor Aerosol Mass and Size Distribution in a Northern Indian City and Its Correlation to Black Carbon

The seasonal and diurnal behavior of atmospheric submicron aerosol was studied in the northern Indian city of Kanpur in the Indo Gangetic Plain during July 2006–May 2007. The size distribution and mass concentration of the aerosol in the range of 15-700 nm was measured using a scanning mobility particle sizer (SMPS). Simultaneously, black carbon (BC) measurement was made using an aethalometer. The measurements were recorded for four different seasons, viz. monsoon, post-monsoon, winter and pre-monsoon. The diurnal variation of BC and submicron aerosol mass followed very similar trends in all the seasons. This is evident by the fact that BC had strong positive correlation with the submicron aerosol mass (0.83 ≤ R ≤ 0.96, where R is the Pearson’s correlation coefficient). Both peaked once in the morning [07:00-09:00 local time (LT)], and once in the night (20:00-22:00 LT). The peak concentrations varied from season to season, which could be attributed to seasonal variation in anthropogenic activity, traffic movement and atmospheric boundary layer conditions. The background aerosol number concentration in winter (~105 #/cm3) was an order of magnitude higher than that observed in other seasons (~104 #/cm3); and on a foggy day in the winter, it was twice as high as that seen on a clear winter day. The fraction (FBC) of the BC mass concentration in the submicron aerosol was observed to be highest in monsoon (0.18 ± 0.13), followed by pre-monsoon (0.08 ± 0.02) and post-monsoon (0.05 ± 0.01), with the lowest in winter (0.03 ± 0.01).

Aerosol characteristics during winter fog at Agra, North India

Simultaneous measurements on physical, chemical and optical properties of aerosols over a tropical semi-arid location, Agra in north India, were undertaken during December 2004. The average concentration of total suspended particulates (TSP) increased by about 1.4 times during intense foggy/hazy days. Concentrations of SO4 2−, NO3 −, NH4 + and Black Carbon (BC) aerosols increased by 4, 2, 3.5 and 1.7 times, respectively during that period. Aerosols were acidic during intense foggy/hazy days but the fog water showed alkaline nature, mainly due to the neutralizing capacity of NH4 aerosols. Trajectory analyses showed that air masses were predominantly from NW direction, which might be responsible for transport of BC from distant and surrounding local sources. Diurnal variation of BC on all days showed a morning and an evening peak that were related to domestic cooking and vehicular emissions, apart from boundary layer changes. OPAC (Optical properties of aerosols and clouds) model was used to compute the optical properties of aerosols. Both OPAC-derived and observed aerosol optical depth (AOD) values showed spectral variation with high loadings in the short wavelengths (<1 µm). AOD value at 0.5 µm wavelength was significantly high during intense foggy/hazy days (1.22) than during clear sky or less foggy/hazy days (0.63). OPAC-derived Single scattering albedo (SSA) was 0.84 during the observational period, indicating significant contribution of absorbing aerosols. However, the BC mass fraction to TSP increased by only 1% during intense foggy/hazy days and thereby did not show any impact on SSA during that period. A large increase was observed in the shortwave (SW) atmospheric (ATM) forcing during intense foggy/hazy days (+75.8 W/m2) than that during clear sky or less foggy/hazy days (+38 W/m2), mainly due to increase in absorbing aerosols. Whereas SW forcing at surface (SUF) increased from −40 W/m2 during clear sky or less foggy/hazy days to −76 W/m2 during intense foggy/hazy days, mainly due to the scattering aerosols like SO4 2-.

Influence of local waste burning on atmospheric aerosol properties in urban environment

Aerosols affect the radiative energy budget on both the regional and global scales. The wavelength-dependent aerosol optical depth (AOD) is a fundamental determinant of the amount by which extra-terrestrial incoming sunlight and outgoing terrestrial radiation are being attenuated in the atmosphere. The present study addresses the influence of local waste burning on aerosol characteristics, black carbon (BC) aerosol mass concentration and spectral solar irradiance using ground-based measurements over the tropical urban environment of Hyderabad, India. AOD has been observed to be maximum during burning days compared to normal days. Aerosol size spectra suggest bimodal distributions during pre-and post-burning periods and trimodal distributions during burning periods. Angstrom wavelength exponent estimated from spectral variation of AOD suggested dominance of accumulation mode particle loading during burning days compared to normal days. Diurnal variation of BC on normal days showed a broad nocturnal peak during ∼20:00 to ∼24:00 h with a maximum value of BC aerosol concentration of ∼14,000 ng m −3 whereas on local waste burning days enormous increases in BC concentrations have been observed with a peak at ∼60,000 ng m −3. Relative attenuation of global solar irradiance during burning days has been found to be of the order of 30% in the visible and 28% in the near-infrared regions. The results are discussed in detail in this paper.