D.G. Kaskaoutis

Effects of crop residue burning on aerosol properties, plume characteristics, and long‐range transport over northern India

Aerosol emissions from biomass burning are of specific interest over the globe due to their strong radiative impacts and climate implications. The present study examines the impact of paddy crop residue burning over northern India during the postmonsoon (October–November) season of 2012 on modification of aerosol properties, as well as the long-range transport of smoke plumes, altitude characteristics, and affected areas via the synergy of ground-based measurements and satellite observations. During this period, Moderate Resolution Imaging Spectroradiometer (MODIS) images show a thick smoke/hazy aerosol layer below 2–2.5 km in the atmosphere covering nearly the whole Indo-Gangetic Plains (IGP). The air mass trajectories originating from the biomass-burning source region over Punjab at 500 m reveal a potential aerosol transport pathway along the Ganges valley from west to east, resulting in a strong aerosol optical depth (AOD) gradient. Sometimes, depending upon the wind direction and meteorological conditions, the plumes also influence central India, the Arabian Sea, and the Bay of Bengal, thus contributing to Asian pollution outflow. The increased number of fire counts (Terra and Aqua MODIS data) is associated with severe aerosol-laden atmospheres (AOD500 nm > 1.0) over six IGP locations, high values of Angstrom exponent (>1.2), high particulate mass 2.5 (PM2.5) concentrations (>100–150 µgm−3), and enhanced Ozone Monitoring Instrument Aerosol Index gradient (~2.5) and NO2 concentrations (~6 × 1015 mol/cm2), indicating the dominance of smoke aerosols from agricultural crop residue burning. The aerosol size distribution is shifted toward the fine-mode fraction, also exhibiting an increase in the radius of fine aerosols due to coagulation processes in a highly turbid environment. The spectral variation of the single-scattering albedo reveals enhanced dominance of moderately absorbing aerosols, while the aerosol properties, modification, and mixing atmospheric processes differentiate along the IGP sites depending on the distance from the aerosol source, urban influence, and local characteristics.

Variability and Trends of Aerosol Properties over Kanpur, Northern India using AERONET Data (2001-10)

Natural and anthropogenic aerosols over northern India play an important role in influencing the regional radiation budget, causing climate implications to the overall hydrological cycle of South Asia. In the context of regional climate change and air quality, we discuss aerosol loading variability and trends at Kanpur AERONET station located in the central part of the Indo-Gangetic plains (IGP), during the last decade (2001‐10). Ground-based radiometric measurements show an overall increase in column-integrated aerosol optical depth (AOD) on a yearly basis. This upward trend is mainly due to a sustained increase in the seasonal/monthly averaged AOD during the winter (Dec‐Feb) and post-monsoon (Oct‐Nov) seasons (dominated by anthropogenic emissions). In contrast, a neutral to weak declining trend is observed during late pre-monsoon (Mar‐May) and monsoon (Jun‐Sep) months, mainly influenced by inter-annual variations of dust outbreaks. A general decrease in coarse-mode aerosols associated with variable dust activity is observed, whereas the statistically significant increasing post-monsoon/winter AOD is reflected in a shift of the columnar size distribution towards relatively larger particles in the accumulation mode. Overall, the present study provides an insight into the pronounced seasonal behavior in aerosol loading trends and, in general, is in agreement with that associating the findings with those recently reported by satellite observations (MODIS and MISR) over northern India. Our results further suggest that anthropogenic emissions (due mainly to fossil-fuel and biomass combustion) over the IGP have continued to increase in the last decade.

Carbonaceous aerosols and pollutants over Delhi urban environment: temporal evolution, source apportionment and radiative forcing.

Particulate matter (PM2.5) samples were collected over Delhi, India during January to December 2012 and analysed for carbonaceous aerosols and inorganic ions (SO4(2-) and NO3(-)) in order to examine variations in atmospheric chemistry, combustion sources and influence of long-range transport. The PM2.5 samples are measured (offline) via medium volume air samplers and analysed gravimetrically for carbonaceous (organic carbon, OC; elemental carbon, EC) aerosols and inorganic ions (SO4(2-) and NO3(-)). Furthermore, continuous (online) measurements of PM2.5 (via Beta-attenuation analyser), black carbon (BC) mass concentration (via Magee scientific Aethalometer) and carbon monoxide (via CO-analyser) are carried out. PM2.5 (online) range from 18.2 to 500.6μgm(-3) (annual mean of 124.6±87.9μgm(-3)) exhibiting higher night-time (129.4μgm(-3)) than daytime (103.8μgm(-3)) concentrations. The online concentrations are 38% and 28% lower than the offline during night and day, respectively. In general, larger night-time concentrations are found for the BC, OC, NO3(-)and SO4(2-), which are seasonally dependent with larger differences during late post-monsoon and winter. The high correlation (R(2)=0.74) between OC and EC along with the OC/EC of 7.09 (day time) and 4.55 (night-time), suggest significant influence of biomass-burning emissions (burning of wood and agricultural waste) as well as secondary organic aerosol formation during daytime. Concentrated weighted trajectory (CWT) analysis reveals that the potential sources for the carbonaceous aerosols and pollutants are local emissions within the urban environment and transported smoke from agricultural burning in northwest India during post-monsoon. BC radiative forcing estimates result in very high atmospheric heating rates (~1.8-2.0Kday(-1)) due to agricultural burning effects during the 2012 post-monsoon season.

Assessment of chemical and mineralogical characteristics of airborne dust in the Sistan region, Iran

Windblown transport and deposition of dust is widely recognized as an important physical and chemical concern to climate, human health and ecosystems. Sistan is a region located in southeast Iran with extensive wind erosion, severe desertification and intense dust storms, which cause adverse effects in regional air quality and human health. To mitigate the impact of these phenomena, it is vital to ascertain the physical and chemical characteristics of airborne and soil dust. This paper examines for the first time, the mineralogical and chemical properties of dust over Sistan by collecting aerosol samples at two stations established close to a dry-bed lake dust source region, from August 2009 to August 2010. Furthermore, soil samples were collected from topsoil (0-5 cm depth) at several locations in the dry-bed Hamoun lakes and downwind areas. These data were analyzed to investigate the chemical and mineralogical characteristics of dust, relevance of inferred sources and contributions to air pollution. X-ray Diffraction (XRD) analysis of airborne and soil dust samples shows that the dust mineralogy is dominated mainly by quartz (30-40%), calcite (18-23%), muscovite (10-17%), plagioclase (9-12%), chlorite (~6%) and enstatite (~3%), with minor components of dolomite, microcline, halite and gypsum. X-ray Fluorescence (XRF) analyses of all the samples indicate that the most important oxide compositions of the airborne and soil dust are SiO(2), CaO, Al(2)O(3), Na(2)O, MgO and Fe(2)O(3), exhibiting similar percentages for both stations and soil samples. Estimates of Enrichment Factors (EFs) for all studied elements show that all of them have very low EF values, suggesting natural origin from local materials. The results suggest that a common dust source region can be inferred, which is the eroded sedimentary environment in the extensive Hamoun dry lakes lying to the north of Sistan.

Dryness of ephemeral lakes and consequences for dust activity: The case of the Hamoun drainage basin, southeastern Iran

This study examines the influence of changes in the water coverage in the Hamoun dry-bed lakes on visibility, dust outbreaks, aerosol loading and land-atmospheric fluxes over the region covering the period 1985-2005. The Hamoun basin, located on the southeastern Iran and western Afghanistan borders, has been recognized as one of the major dust source regions in south Asia and is covered by shallow, marshy lakes that are fed by the Helmand and Farahrood rivers. When the water in watersheds that support the lakes is drawn down for natural or human-induced reasons, the end result is a decrease in the water coverage in the basin, or even complete dryness as occurred in 2001. Then, strong seasonal winds, mainly in summer, blow fine sand and silt off the exposed lakebed, enhancing dust activity and aerosol loading over the region. Satellite (Landsat) and meteorological observations reveal that the water levels in the Hamoun lakes exhibit considerable inter-annual variability during the period 1985-2005 strongly related to anomalies in precipitation. This is the trigger for concurrent changes in the frequency of the dusty days, aerosol loading and deterioration of visibility over the region, as satellite (TOMS, MODIS, MISR) observations reveal. On the other hand, soil moisture and latent heat, obtained via model (GLDAS_noah-10) simulations are directly linked with water levels and precipitation over the region. The desiccation of the Hamoun lakes in certain years and the consequent increase in frequency and intensity of dust storms are serious concerns for the regional climate, ecosystems and human health.

Crop Residue Burning: A Threat to South Asian Air Quality

For more than 2 decades, crop residues in Punjab, a region spanning northwestern India and eastern Pakistan, have been burned during October and November to ready fields for the next years planting. This practice poses a serious threat to air quality in South Asia.

Transport pathways of Sahara dust over Athens, Greece as detected by MODIS and TOMS

This study analyses the Saharan dust (SD) events over Athens during 2000–2005 using daily Moderate Resolution Imaging Spectroradiometer (MODIS) and Total Ozone Mapping Spectrometer (TOMS) satellite data. The dust events were identified using the MODIS daily observations over Greece and the dates with detectable dust plumes were collected. The aerosol optical depth (AOD550) and fine-mode (FM) values from Terra-MODIS and Aerosol Index (AI) values from TOMS were obtained over Athens for the dusty days focusing on analysing the seasonality, intensity, transport pathways and mechanisms of dust. Seventy-nine dusty days were identified corresponding to SD events with duration from 1 to 4 consecutive days; the majority of SD events occur in April–May and July, with less during winter. The dust frequency presents large seasonal and intra-annual variation, with a maximum of 20 dust events in 2002 and a minimum of 7 in 2003. The use of TOMS-AI seems to be adequate for the characterization of dust over Athens despite the fact that 35% of the dusty days do not correspond to high AI values. The dust events are more intense during spring, mostly associated with dust transport from near surface to mid troposphere (vertical transport mechanism), while dust events detected only within the boundary layer have the lowest AOD values. On the other hand, the dust events in summer are of larger duration due to stable weather conditions and absence of precipitation and transportation at elevated heights.

Estimation of particulate matter from satellite-and ground-based observations over Hyderabad, India

Long-term trends in surface-level particulate matter of dynamic diameter ≤2 µm (PM2) in regard to air quality observations over Greater Hyderabad Region (GHR), India are estimated by the synergy of ground-based measurements and satellite observations during the period 2001–2013 (satellite) and July 2009–Dec 2013 (ground-based). Terra Moderate Resolution Imaging Spectroradiometer (MODIS)-derived aerosol optical thickness (AOT) (MODIS-AOTs) was validated against that measured from Microtops-II Sunphotometer (MTS) AOTs (MTS-AOTs) and then utilized to estimate surface-level PM2 concentrations over GHR using regression analysis between MODIS-AOTs, MTS-AOTs, and measured PM2. In general, the MODIS-estimated PM2 concentrations fell within the uncertainty of the measurements, thus allowing the estimate of PM2 from MODIS, although in some cases they differed significantly due to vertical heterogeneity in aerosol distribution and the presence of distinct elevated aerosol layers of different origin and characteristics. Furthermore, significant spatial and temporal heterogeneity in the AOT and PM2 estimates is observed in urban environments, especially during the pre-monsoon and monsoon seasons, which reduces the accuracy of the PM2 estimates from MODIS. The estimates of PM2 using MTS or MODIS-AOT exhibit a root mean square deference (RMSD) of about 8–16% against measured PM2 on a seasonal basis. Furthermore, a tendency of increasing PM2 concentrations is observed, which however is difficult to quantify for urban areas due to uncertainties in PM2 estimations and gaps in the data set. Examination of surface and columnar aerosol concentrations, along with meteorological parameters from radiosonde observations on certain days, reveals that changes in local emissions and boundary-layer dynamics, and the presence or arrival of distinct aerosol plumes aloft, are major concerns in the accurate estimation of PM2 from MODIS, while the large spatial distribution of aerosol and pollutants in the urban environment makes such estimates a considerable challenge.

Changes of Permanent Lake Surfaces, and Their Consequences for Dust Aerosols and Air Quality: The Hamoun Lakes of the Sistan Area, Iran

© 2012 Rashki et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Changes of Permanent Lake Surfaces, and Their Consequences for Dust Aerosols and Air Quality: The Hamoun Lakes of the Sistan Area, Iran

First results from light scattering enhancement factor over central Indian Himalayas during GVAX campaign

The present work examines the influence of relative humidity (RH), physical and optical aerosol properties on the light-scattering enhancement factor [f(RH=85%)] over central Indian Himalayas during the Ganges Valley Aerosol Experiment (GVAX). The aerosol hygroscopic properties were measured by means of DoE/ARM (US Department of Energy, Atmospheric Radiation Measurement) mobile facility focusing on periods with the regular instrumental operation (November-December 2011). The measured optical properties include aerosol light-scattering (σsp) and absorption (σap) coefficients and the intensive parameters i.e., single scattering albedo (SSA), scattering Ångström exponent (SAE), absorption Ångström exponent (AAE) and light scattering enhancement factor (f(RH)=σsp(RH, λ)/σsp(RHdry, λ)). The measurements were separated for sub-micron (<1μm, D1μm) and particles with diameter<10μm (D10μm) in order to examine the influence of particle size on f(RH) and enhancement rate (γ). The particle size affects the aerosol hygroscopicity since mean f(RH=85%) of 1.27±0.12 and 1.32±0.14 are found for D10μm and D1μm, respectively. These f(RH) values are relatively low suggesting the enhanced presence of soot and carbonaceous particles from biomass burning activities, which is verified via backward air-mass trajectories. Similarly, the light-scattering enhancement rates are ~0.20 and 0.17 for the D1μm and D10μm particles, respectively. However, a general tendency for increasing f(RH) and γ is shown for higher σsp and σap values indicating the presence of rather aged smoke plumes, coated with industrial aerosols over northern India, with mean SSA, SAE and AAE values of 0.92, 1.00 and 1.15 respectively. On the other hand, a moderate-to-small dependence of f(RH) and γ on SAE, AAE, and SSA was observed for both particle sizes. Furthermore, f(RH) exhibits an increasing tendency with the number of cloud condensation nuclei (NCCN) indicating larger particle hygroscopicity but without significant dependence on the activation ratio.