Wildfires in a warmer climate: Emission fluxes, emission heights, and black carbon concentrations in 2090-2099

Abstract. In this study one year of ceilometer measurements taken in the Kathmandu Valley, Nepal, in the framework of the SusKat project (A Sustainable Atmosphere for the Kathmandu Valley) were analyzed to investigate the diurnal variation of the mixing layer height and its dependency on the meteorological conditions. In addition, the impact of the mixing layer height on the temporal variation and the magnitude of the measured black carbon concentrations are analysed for each season. Based on the assumption that black carbon aerosols are vertically well mixed within the mixing layer and the finding that the mixing layer varies only little during night time and morning hours, black carbon emission fluxes are estimated for these hours and per month. Even though this method is relatively simple, it can give an observationally based first estimate of the black carbon emissions in this region, especially illuminating the seasonal cycle of the emission fluxes. In all seasons the diurnal cycle of the mixing layer height is typically characterized by low heights during the night and maximum values during in the afternoon. Seasonal differences are found in the absolute mixing layer height values and the duration of the typical daytime maximum. During the monsoon season a diurnal cycle has been observed with the smallest amplitude, with the lowest daytime mixing height of all seasons, and also the highest nighttime and early morning mixing height of all seasons. These characteristics can mainly be explained with the frequently present clouds and the associated reduction in incoming solar radiation and outgoing longwave radiation. In general, the black carbon concentrations show a clear anticorrelation with mixing layer height measurements, although this relation is less pronounced in the monsoon season. The daily evolution of the black carbon diurnal cycle differs between the seasons, partly due to the different meteorological conditions including the mixing layer height. Other important reasons are the different main emission sources and their diurnal variations in the individual seasons. The estimation of the black carbon emission flux for the morning hours show a clear seasonal cycle with maximum values in December to April. Compared to the emission flux values provided by different emission databases for this region, the here estimated values are considerably higher. Several possible sources of uncertainty are considered, and even the absolute lower bound of the emissions based on our methodology is higher than in most emissions datasets, providing strong evidence that the black carbon emissions for this region have likely been underestimated in modelling studies thus far.

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Investigation of the mixing layer height derived from ceilometer measurements in the Kathmandu Valley and implications for local air quality

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-8157-2017 ◽

2017 ◽

Vol 17 (13) ◽

pp. 8157-8176 ◽

Cited By ~ 23

Author(s):

Andrea Mues ◽

Maheswar Rupakheti ◽

Christoph Münkel ◽

Axel Lauer ◽

Heiko Bozem ◽

...

Keyword(s):

Black Carbon ◽

Monsoon Season ◽

Mixing Layer ◽

Early Morning ◽

Kathmandu Valley ◽

Mixing Height ◽

Night Time ◽

Emission Fluxes ◽

Mixing Layer Height ◽

Carbon Concentrations

Abstract. In this study 1 year of ceilometer measurements taken in the Kathmandu Valley, Nepal, in the framework of the SusKat project (A Sustainable Atmosphere for the Kathmandu Valley) were analysed to investigate the diurnal variation of the mixing layer height (MLH) and its dependency on the meteorological conditions. In addition, the impact of the MLH on the temporal variation and the magnitude of the measured black carbon concentrations are analysed for each season. Based on the assumption that black carbon aerosols are vertically well mixed within the mixing layer and the finding that the mixing layer varies only little during night time and morning hours, black carbon emission fluxes are estimated for these hours and per month. Even though this method is relatively simple, it can give an observationally based first estimate of the black carbon emissions in this region, especially illuminating the seasonal cycle of the emission fluxes. The monthly minimum median MLH values typically range between 150 and 200 m during night and early morning hours, the monthly maximum median values between 625 m in July and 1460 m in March. Seasonal differences are not only found in the absolute MLHs, but also in the duration of the typical daytime maximum ranging between 2 and 3 h in January and 6–7 h in May. During the monsoon season a diurnal cycle has been observed with the smallest amplitude (typically between 400 and 500 m), with the lowest daytime mixing height of all seasons (maximum monthly median values typically between 600 and 800 m), and also the highest night-time and early morning mixing height of all seasons (minimum monthly median values typically between 200 and 220 m). These characteristics can mainly be explained with the frequently present clouds and the associated reduction in incoming solar radiation and outgoing longwave radiation. In general, the black carbon concentrations show a clear anticorrelation with MLH measurements, although this relation is less pronounced in the monsoon season. The daily evolution of the black carbon diurnal cycle differs between the seasons, partly due to the different meteorological conditions including the MLH. Other important reasons are the different main emission sources and their diurnal variations in the individual seasons. The estimation of the black carbon emission flux for the morning hours show a clear seasonal cycle with maximum values in December to April. Compared to the emission flux values provided by different emission databases for this region, the estimated values here are considerably higher. Several possible sources of uncertainty are considered, and even the absolute lower bound of the emissions based on our methodology is higher than in most emissions datasets, providing strong evidence that the black carbon emissions for this region have likely been underestimated in modelling studies thus far.

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Traffic Density-Related Black Carbon Distribution: Impact of Wind in a Basin Town

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18126490 ◽

2021 ◽

Vol 18 (12) ◽

pp. 6490

Author(s):

Borut Jereb ◽

Brigita Gajšek ◽

Gregor Šipek ◽

Špela Kovše ◽

Matevz Obrecht

Keyword(s):

Black Carbon ◽

Carbon Concentration ◽

Ground Level ◽

Traffic Density ◽

Carbon Distribution ◽

Wind Speeds ◽

Black Carbon Concentration ◽

Low Wind Speeds ◽

Temperature Inversions ◽

Carbon Concentrations

Black carbon is one of the riskiest particle matter pollutants that is harmful to human health. Although it has been increasingly investigated, factors that depend on black carbon distribution and concentration are still insufficiently researched. Variables, such as traffic density, wind speeds, and ground levels can lead to substantial variations of black carbon concentrations and potential exposure, which is even riskier for people living in less-airy sites. Therefore, this paper “fills the gaps” by studying black carbon distribution variations, concentrations, and oscillations, with special emphasis on traffic density and road segments, at multiple locations, in a small city located in a basin, with frequent temperature inversions and infrequent low wind speeds. As wind speed has a significant impact on black carbon concentration trends, it is critical to present how low wind speeds influence black carbon dispersion in a basin city, and how black carbon is dependent on traffic density. Our results revealed that when the wind reached speeds of 1 ms−1, black carbon concentrations actually increased. In lengthy wind periods, when wind speeds reached 2 or 3 ms−1, black carbon concentrations decreased during rush hour and in the time of severe winter biomass burning. By observing the results, it could be concluded that black carbon persists longer in higher altitudes than near ground level. Black carbon concentration oscillations were also seen as more pronounced on main roads with higher traffic density. The more the traffic decreases and becomes steady, the more black carbon concentrations oscillate.

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Black carbon concentrations in California vehicles and estimation of in-vehicle diesel exhaust particulate matter exposures

Atmospheric Environment ◽

10.1016/j.atmosenv.2004.04.026 ◽

2004 ◽

Vol 38 (25) ◽

pp. 4123-4133 ◽

Cited By ~ 111

Author(s):

Scott A Fruin ◽

Arthur M Winer ◽

Charles E Rodes

Keyword(s):

Particulate Matter ◽

Black Carbon ◽

Diesel Exhaust ◽

Diesel Exhaust Particulate ◽

Carbon Concentrations ◽

Exhaust Particulate

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Effect of Reducing Ambient Traffic-Related Air Pollution on Blood Pressure

Hypertension ◽

10.1161/hypertensionaha.120.15580 ◽

2021 ◽

Vol 77 (3) ◽

pp. 823-832

Author(s):

Neelakshi Hudda ◽

Misha Eliasziw ◽

Scott O. Hersey ◽

Ellin Reisner ◽

Robert D. Brook ◽

...

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Air Pollution ◽

Black Carbon ◽

Mixed Model ◽

Particle Number ◽

Linear Mixed Model ◽

High Efficiency ◽

High Exposure ◽

Carbon Concentrations

Exposure to traffic-related air pollution (TRAP) may contribute to increased prevalence of hypertension and elevated blood pressure (BP) for residents of near-highway neighborhoods. Relatively few studies have investigated the effects of reducing TRAP exposure on short-term changes in BP. We assessed whether reducing indoor TRAP concentrations by using stand-alone high-efficiency particulate arrestance (HEPA) filters and limiting infiltration through doors and windows effectively prevented acute (ie, over a span of hours) increases in BP. Using a 3-period crossover design, 77 participants were randomized to attend three 2-hour-long exposure sessions separated by 1-week washout periods. Each participant was exposed to high, medium, and low TRAP concentrations in a room near an interstate highway. Particle number concentrations, black carbon concentrations, and temperature were monitored continuously. Systolic BP (SBP), diastolic BP, and heart rate were measured every 10 minutes. Outcomes were analyzed with a linear mixed model. The primary outcome was the change in SBP from 20 minutes from the start of exposure. SBP increased with exposure duration, and the amount of increase was related to the magnitude of exposure. The mean change in SBP was 0.6 mm Hg for low exposure (mean particle number and black carbon concentrations, 2500 particles/cm 3 and 149 ng/m 3 ), 1.3 mm Hg for medium exposure (mean particle number and black carbon concentrations, 11 000 particles/cm 3 and 409 ng/m 3 ), and 2.8 mm Hg for high exposure (mean particle number and black carbon concentrations, 30 000 particles/cm 3 and 826 ng/m 3 ; linear trend P =0.019). There were no statistically significant differences in the secondary outcomes, diastolic BP, or heart rate. In conclusion, reducing indoor concentrations of TRAP was effective in preventing acute increases in SBP.

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