A Climatological Satellite Assessment of Absorbing Carbonaceous Aerosols on a Global Scale

A global climatology of absorbing carbonaceous aerosols (ACA) for the period 2005–2015 is obtained by using satellite MODIS (Moderate Resolution Imaging Spectroradiometer)-Aqua and OMI (Ozone Monitoring Instrument)-Aura aerosol optical properties and by applying an algorithm. The algorithm determines the frequency of presence of ACA (black and brown carbon) over the globe at 1° × 1° pixel level and on a daily basis. The results of the algorithm indicate high frequencies of ACA (up to 19 days/month) over world regions with extended biomass burning, such as the tropical forests of southern and central Africa, South America and equatorial Asia, over savannas, cropland areas or boreal forests, as well as over urban and rural areas with intense anthropogenic activities, such as the eastern coast of China or the Indo-Gangetic plain. A clear seasonality of the frequency of occurrence of ACA is evident, with increased values during June–October over southern Africa, during July–November over South America, August–November over Indonesia, November–March over central Africa and November–April over southeastern Asia. The estimated seasonality of ACA is in line with the known annual patterns of worldwide biomass-burning emissions, while other features such as the export of carbonaceous aerosols from southern Africa to the southeastern Atlantic Ocean are also successfully reproduced by the algorithm. The results indicate a noticeable interannual variability and tendencies of ACA over specific world regions during 2005–2015, such as statistically significant increasing frequency of occurrence over southern Africa and eastern Asia.

Fractal morphology features and carbon component analysis of diesel particulates

External morphology and internal carbonaceous compositions are important characteristics for the source recognition of atmospheric particulate matter (PM). The fractal dimension of morphology and carbon components of diesel PM with different sizes both at high and low load were studied through fractal theory and thermal optical reflection method. It is revealed that small-size PM absorbs more soluble organic fractions and correspondingly has greater box dimension. Due to heavy aggregation, PM collected at low load has greater box dimension than that at high load because of heavy aggregation. OC1, which is the most volatile among organic carbons, is remarkably increased at low load or for small-size PM, absorbing more unburned hydrocarbons. At low load, a large amount of EC1 (char-EC) is generated and the ratio of OC/EC is more than 10, while, at high load, the EC is mainly composed of EC2 (soot-EC) and the ratio of OC/EC is less than 1. Apparently, the box dimension from the morphology of diesel PM presents a positive correlation with the ratio of OC/EC. Via above external and internal characteristics, particulates exhausted from motor vehicles in the atmosphere can be beneficially identified.

Vertical profiles of black carbon aerosols over the urban locations in South India

Vertical profiles of black carbon (BC) aerosol were determined from aircraft measurements under the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) program conducted by the Indian Institute of Tropical Meteorology, India during 2009 over Bangalore and Hyderabad in south India. BC mass loadings decreased approximately monotonically from 10(3) to 10(4) ng/m(3) at the surface to ~10(2) ng/m(3) at an altitude of about 7 km; although layers at intermediate levels containing anomalously high BC loadings were frequently encountered that were attributed mainly to the convective transport from surface sources accompanied by changes in the local boundary layer and atmospheric stability. In addition, as evidenced from air mass back trajectories; long range transport from distant sources contributed to some anomalous spikes in BC concentration. The presence of BC in cloud forming regions of the free troposphere could have important implications for cloud microphysics and subsequent rainfall mechanism over this region. Apart from this, the effects on human health are equally important.

Measurement of semivolatile carbonaceous aerosols and its implications: a review

Measurement of carbonaceous aerosols is complicated by positive and negative artifacts. An organic denuder with high efficiency for removing gaseous organics is an effective approach to eliminate the positive artifact, and it is a precondition for the accurate determination of SVOC by an adsorbent backup filter. Evaluations of different configurations of the organic denuder, and SVOC determined by different denuder-based samplers, both integrated and semi-continuous, are reviewed. A new equation for determination of the denuder efficiency is estimated, considering the efficiency of removing both the gaseous organics that could be adsorbed by the quartz and the gaseous passing through the quartz that could be subsequently adsorbed by the backup adsorbent filter. The origin of OC on the backup quartz filter, behind either quartz or Teflon filter, is quantitatively evaluated by the denuder-based method based on the data published. The backup-OC is shown to be dominated by either gaseous organics passing through the front filter or the evaporated particulate organic carbon depending on the sampling environment.