Biomass burning (BB) is a significant air pollution source, with global, regional and local impacts on air quality, public health and climate. Worldwide an extensive range of studies has been ...conducted on almost all the aspects of BB, including its specific types, on quantification of emissions and on assessing its various impacts. China is one of the countries where the significance of BB has been recognized, and a lot of research efforts devoted to investigate it, however, so far no systematic reviews were conducted to synthesize the information which has been emerging. Therefore the aim of this work was to comprehensively review most of the studies published on this topic in China, including literature concerning field measurements, laboratory studies and the impacts of BB indoors and outdoors in China. In addition, this review provides insights into the role of wildfire and anthropogenic BB on air quality and health globally. Further, we attempted to provide a basis for formulation of policies and regulations by policy makers in China.
Open field biomass burning causes severe air pollution, public health risk and potential climate impact. a) Photo taken in Changzhou rural area on June 10, 2015; b) Photo taken in Hebei rural area on October 23, 2013; c) A traditional indoor burner in rural area in China; d) Tar ball emitted from biomass burning. Display omitted
•This review discusses wildfire and anthropogenic emission from biomass burning in China.•Field observations and laboratory studies on public health and climate impacts of biomass burning•Atmospheric process of biomass burning plumes and their transport•Proposed research priorities and insights about biomass burning in China
The Sistan Basin has been recognized as one of the most active dust sources and windiest desert environments in the world. Although the dust activity in Sistan maximizes during the summer, rare but ...intense dust storms may also occur in the winter. This study aims to elucidate the atmospheric dynamics related to dust emission and transport, dust-plume characteristics, and impacts on aerosol properties and air quality during an intense dust storm over Sistan in February 2019. The dust storm was initiated by strong northerly winds (~20 ms−1) associated with the intrusion of a cold front from high latitudes. The upper-level potential vorticity (PV)-trough evolved into a cut-off low in the mid and upper troposphere and initiated unstable weather over Afghanistan and northern Pakistan. At the surface, density currents emanating from deep convective clouds and further strengthened by downslope winds from the mountains, caused massive soil erosion. The passage of the cold front reduced the temperature by ~10 °C and increased the atmospheric pressure by ~10 hPa, while the visibility was limited to less than 200 m. The rough topography played a major role in modulating the atmospheric dynamics, wind field, dust emissions, and transport pathways. Meso-NH model simulates large amounts of columnar mass dust loading (> 20 g m−2) over Sistan, while the intense dust plume was mainly traveling below 2 km and increased the particulate matter (PM10) concentrations up to 1800 µg m−3 at Zabol. The dust storm was initially moving in an arc-shaped pathway over the Sistan Basin and then it spread away. Plumes of dust covered a large area in southwest Asia, reaching the northern Arabian Sea, and the Thar desert one to two days later, while they strongly affected the aerosol properties at Karachi, Pakistan, by increasing the aerosol optical depth (AOD > 1.2) and the coarse-mode fraction at ~0.7.
Urban areas in developing countries are major sources of carbonaceous aerosols and air pollutants, pointing out the need for a detailed assessment of their levels and origin close to the source. A ...multi-instrument research campaign was performed in Delhi during December 2015–February 2016 aimed at exploring the pollution levels and the contribution of various sources to particulate matter (PM) concentrations, black carbon (BC) aerosols, and trace gases. The weak winds (< 5–6 m s
−1
) along with the shallow boundary layer favoured the formation of thick and persistent fog conditions, which along with the high BC (24.4 ± 12.2 μg m
−3
) concentrations lead to the formation of smog. Very high pollution levels were recorded during the campaign, with mean PM
10
, PM
2.5
, CO, NO, and O
3
concentrations of 245.5 ± 109.8 μg m
−3
, 145.5 ± 69.5 μg m
−3
, 1.7 ± 0.5 ppm, 7.9 ± 2.3 ppb, and 31.3 ± 18.4 ppb, respectively. This study focuses on examining the daily/diurnal cycles of the aerosol optical properties (extinction, scattering, absorption coefficients, single scattering albedo), as well as of PM and other pollutant concentrations, along with changes in meteorology (mixing-layer height and wind speed). In addition, the hot-spot pollution sources in the greater Delhi area were determined via bivariate plots and conditional bivariate probability function (CBPF), while the distant sources were examined via the concentration weighted trajectory (CWT) analysis. The results show that the highest aerosol absorption and scattering coefficients, PM, and trace gas concentrations are detected for weak winds (< 2 m s
−1
) with a preference for eastern directions, revealing high contribution from local sources and accumulation of pollutants within urban Delhi.
Long-term aerosol characteristics were assessed over the Indo-Gangetic Basin (IGB) using satellite-derived aerosol properties from January 2007 to December 2017. The study shows steadily high aerosol ...optical depth (AOD ~0.7) with a decadal increasing trend (~20%) over the IGB. Angstrom exponent (AE) shows a relatively large increasing trend at Lucknow in the central IGB (~25%) as compared to Delhi in the north-west IGB (~18%), which suggests relative increase in fine-mode aerosols at Lucknow (~30%). Though, single scattering albedo (SSA) does not show any considerable decadal trend at both the stations, the ultraviolet-aerosol index (UV-AI) shows an increasing trend, with a pronounced increase at Delhi (~26%) compared to Lucknow (~20%). Result suggests relative dominance of absorbing dust aerosols over Delhi. Further, to understand the impact of emerging activities, analyses were done in two sub-periods: 2007–2012 and 2013–2017. Interestingly, a relative increasing trend in AOD (~31%) is observed at Delhi compared to Lucknow during 2007–2012, which was observed at Lucknow (~22%) during 2013–2017. The emission inventory corroborates with the trend and variability of optical properties for different sub-periods, and results show intense development activities in the region have an influence on vertical as well as horizontal aerosol load.
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•Lang-term aerosol characteristics were assessed at two contrasting sites over IGB.•A decadal increasing trend in AOD by ~20% was observed over the IGB.•Pronounced increase in AE at Lucknow suggests relative dominance of fine particles.•Pronounced increase in UV-AI at Delhi suggests relative dominance of absorbing aerosols.•PM10 is ~2.5 times higher at Delhi than Lucknow associated with intense developmental activities.
An efficient method for the separation of prime value products from crude xylenol fraction of noncaking coal-derived tar acids involving suitable distillation technique is described. The feed as well ...as the products was analysed by gas chromatography (G.C.). The crude xylenol comprising a number of close-boiling phenolic compounds was fractionated under reduced pressure to yield three cuts, viz. cresols (30.7%), xylenols (31.2%) and dihydric phenols (23.3%). The dihydric phenols fraction termed as high boiling tar acids (HBTA) was found to contain significant amounts of catechol (6.4%), methyl catechols (32.3%), resorcinol (12.7%) and methyl resorcinols (8.6%). Catechol together with its homologues and resorcinol with its homologues were isolated from the HBTA. These products, not available from the HBTA of metallurgical coke plants, have been shown to offer distinct marketing advantages. A conceptual scheme for the treatment of crude xylenol as well as application pattern of various products obtainable from the crude mixture is presented.
The present study examines the aerosol characteristics over two locations in the northwest region of India (Dehradun and Patiala) during premonsoon season of 2013. The average mass concentrations of ...particulates (PM10; PM2.5; PM1) were found to be 118 ± 36 , 34 ± 11 , and 19 ± 10 µgm−3 and 140 ± 48 , 30 ± 13 , and 14 ± 06 µgm−3 over Dehradun and Patiala, respectively. The average aerosol optical depth ( A O D 500 n m ) is observed to be 0.62 ± 0.11 over Dehradun and 0.56 ± 0.21 over Patiala. Ångström exponent and fine mode fraction show higher values over Dehradun as compared to Patiala. The average mass concentration of black carbon was found to be 3343 ± 546 ngm−3 and 6335 ± 760 ngm−3 over Dehradun and Patiala, respectively. The diurnal pattern of BC is mainly controlled by boundary layer dynamics and local anthropogenic activities over both the stations. The average single scattering albedo ( S S A 500 n m ) exhibited low value over Patiala ( 0.83 ± 0.01 ) in comparison to Dehradun ( 0.90 ± 0.01 ), suggesting the abundance of absorbing type aerosols over Patiala. The average atmospheric aerosol radiative forcing is +37.34 Wm−2 and +54.81 Wm−2 over Dehradun and Patiala, respectively, leading to atmospheric heating rate of 1.0 K day−1 over Dehradun and 1.5 K day−1 over Patiala.
Recovery of tar acids from ammoniacal liquor and middle oil fraction (170–270°C) of tar produced in the Woodall–Duckham type carboniser of Dankuni Coal Complex (DCC), using non-caking coals, has been ...investigated. About 99.5% of the phenols contained in ammoniacal liquor can be extracted with isobutyl acetate in five stages of extraction using a feed:solvent ratio of 8:1 (v/v) and the phenols content of the liquor can be reduced from about 6000 to 30 ppm. A comparison of products obtained from tar distillation under laboratory conditions to those under actual plant operation has been made. The optimum yields of the middle oil, under standard laboratory distillation and tar distillation plant, were 27.12% and 22.5%, respectively, on dry tar and the content of the refined tar acids in these oil fractions were found to be 9.35% and 7.6% (on dry tar), respectively. However, in actual plant practice, this level of yield has not been achieved yet, due to loss of substantial quantity of tar acids in processing units. With a view to optimising the yield, various aspects of plant operation and process streams were investigated. The yields of tar acids and the other processing streams of DCC have been compared with those of metallurgical coke plants and variations in composition of tar acids discussed. The dihydric phenols (ca. 16% of tar acids) obtainable from DCC, have been shown to offer an attractive potential. The environmental aspects related to discharge of waste streams have been dealt with.
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•Effects of Monsoon, Shamal and Levar winds on dust activity over the Arabian Sea in summer.•High dust accumulation over the north/central Arabian Sea due to merge of contrasting dust ...plumes.•The “hot-spot” dust-laden area is characterized by weak wind conditions.•Inter-Tropical Discontinuity (ITD) plays a major role in dust accumulation and relative influence of each wind regime.•Presence of multiple dust layers in the vertical from different origins along the position of ITD.
This study examines the atmospheric circulation patterns that are associated with contrasting wind regimes, desert dust outflows and accumulation of dust over the Arabian Sea in the summer season. The examined period is 11–16 July 2016, when several dust plumes of various intensity and from different sources (Arabian Peninsula, Somalia and Iran), affected the Arabian Sea. During summer, south Asia is under the influence of the southwest monsoon, with main characteristics being the thermal low-pressure system centered over northwest India/Pakistan with secondary lows over south Iran and southeast Arabian Peninsula, and the Arabian ridge combined with the Indian trough in the mid troposphere. Apart from the dominant southwest monsoon flow over the Arabian Sea, strong local winds are developed over the desert areas, such as the northwest Shamal along the east Arabian Peninsula and northern Levar in southeast Iran. These wind regimes initiate several dust outbreaks, while their convergence over the Arabian Sea results in accumulation of large amounts of dust aerosols (AOD > 2.0), as observed by satellite (MODIS, MISR, CALIPSO) observations and reanalysis (MERRA-2). The dust-accumulation area (central/north part of the Arabian Sea) is characterized by weak winds, while the position of the Inter-Tropical Discontinuity (ITD) plays an important role in merging the contrasting dust plumes. The vertical profiles of the monsoon, Shamal and Levar winds are especially important for the dust accumulation, since the low-altitude dust plumes come from the southeastern Arabian Peninsula and Somalia, while those above 3000 m from northern directions (Iran, Pakistan).
The Caspian Sea – Hindu Kush Index (CasHKI) has been introduced as an indicator of modulation of the wind regime and dust activity over southwest (SW) Asia. This study analyzes the long-term series ...in CasHKI values and the associated mean sea-level pressure (MSLP) anomalies over the Caspian Sea (CS) and Hindu Kush (HK) domains during the period 1963–2014, aiming at examining the trends in CasHKI and the associated climate implications. An overall negative trend (−0.12 hPa per decade) in CasHKI is revealed during 1963–2014, mostly driven by the large decrease in CasHKI during 1963–1980, whereas an increasing trend is found during the 2000s. The CasHKI values are mostly related to the MSLP anomalies over the CS rather than HK domain; however, the negative anomalies in MSLP over HK during the 1960s determine the corresponding CasHKI trends. The MSLP values and anomalies show a regional shift in the core maximum and higher increasing trends at the southern compared to northern latitudes within the CS domain. The synoptic maps of the MSLP, geopotential height at 700 hPa (Z700) and vertical profile of the meridional wind are compared between the months with highest and lowest CasHKI values, revealing a significant intensification in the north wind over the SW Asia and a deepening of the Indian/Pakistan thermal low for the high-CasHKI months in summer. In addition, the high-CasHKI months are mostly associated with a decrease in Z700 over SW Asia and the Middle East, an intensification of the Indian monsoon trough, a decrease in temperature over the SW Asia and a slight increase in rainfall over parts of SW Asia, Middle East and east Africa. Finally, ENSO variability seems not to be significantly linked with CasHKI - but this issue requires further examination.
•Analysis of the long-term (1963–2014) CasHKI variations and trends•Significant intra-seasonal to inter-annual changes in CasHKI intensity•CasHKI variations strongly affect synoptic meteorology over southwest Asia and the Middle East•Large impact of CasHKI variations on wind speed and temperature over southwest Asia
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