Spatial and temporal analyses of air pollutants and meteorological driving forces in Beijing–Tianjin–Hebei region,China

Due to its negative impact on the living environment of human beings, ambient air pollution has become a global challenge to human health. In this study, surface observations of six criteria air pollutants, including PM_2.5, PM₁₀, SO₂, NO₂, CO and O₃, were collected to investigate the spatial and temporal variation in the Beijing–Tianjin–Hebei (BTH) region during 2013–2016 and to explore the relationships between atmospheric pollutants and meteorological variables using quantile regression model (QRM) and multiple linear regression model (MLRM). The results show that BTH region has experienced significant air pollution, and the southern part generally has more severe conditions. The annual average indicates clear decreasing trends of the particulate matters, SO₂ and CO concentrations over the last 4 years and slight increasing trends of NO₂ and O₃ in several cities. The seasonal and monthly characteristics indicate that the concentrations of five species reach their maxima in the winter and their minima in the summer, whereas O₃ has the opposite behaviour. Finally, the pseudo R² values show that the QRMs have the best performance in the winter, followed by spring, fall, and summer. Specifically, all the meteorological factors have significant impacts on air pollution but change with pollutants and seasons. The MLRM results are generally consistent with the QRM results in all seasons, and the inconsistencies are more common in the fall and winter. The results of this research provide foundational knowledge for predicting the response of air quality to climate change in the BTH region.     

Assessment of air pollution originating from copper smelter in Bor (Serbia)

Air quality monitoring was performed at the measuring sites in the urban-industrial and suburban zone during the period 2005–2007 in Bor (Serbia). Arsenic, lead, cadmium, copper and sulphur dioxide are predominantly of industrial origin as a result of copper production in the study area. The smelter, which is a part of the Mining-Metallurgical Complex Bor, is the major pollution source. As and SO₂ are the pollutants which pose the biggest threat for the inhabitants of the Bor area, since the measured concentrations exceed the proposed limit values. The obtained concentrations showed that the endangered areas are in close vicinity of the smelter, as well as in the directions of the prevailing winds. By grouping these pollutants into separate clusters, the results of cluster analysis confirmed high loads of As and SO₂ in the air. The results of principal component analysis showed that copper production has major influence on air pollution.     

The characteristics of air pollutants during different seasons in the urban area of Lanzhou,Northwest China

Based on data from ground-based air quality stations, space–time variations of six principal atmospheric pollutants, such as particulate matter (PM_2.5 and PM₁₀) and gas pollutants (SO₂, NO₂, СО, and O₃), obtained from January 1, 2014 to December 31, 2017 in the city of Lanzhou, have been studied. Average total concentrations of PM_2.5 and PM₁₀ were 53.2?±?26.91 and 124.54?±?82.33 µg/m³, respectively; however, the results showed that in 75.53% and 84.85% days, concentrations of these pollutants exceeded Chinese National Ambient Air Quality Standard and in 100% days exceeded World Health Organization guidelines standards. Daily mean values of aerosol optical depth and Ångström exponent based on data, received by satellite Moderate Resolution Imaging Spectroradiometer, show a broad range of values for aerosol optical depth (from 0.018 to 1.954) and Ångström exponent (from 0.003 to 1.8). Results of principal components analysis revealed three factor loadings. Thus, Factor 1 has the relevant loadings for PM_2.5, PM₁₀, CO, SO₂, and NO₂ (36%) and closely associated with transport emissions and industrial sources, which contribute to air pollution in Lanzhou. Factor 2 was heavily loaded with temperature and visibility (16.94%). Factor 3 consisted of relative humidity (14.11%). Cluster analysis revealed four subgroups: cluster 1 (PM_2.5, NO₂, SO₂), cluster 2 (CO), cluster 3 (PM₁₀) and cluster 4 (relative humidity, visibility, temperature, O₃, wind speed), which were compliant with results, obtained from principal components analysis. Positive correlation was found among all pollutants, other than O₃. According to processed backward trajectories obtained by Hybrid Single-Particle Lagrangian Integrated Trajectory model, it was found that movement of air masses occur from north, northwest, and west directions—the location of principal natural sources of aerosols.     

Assessment of environmental impact of open burning of scrap tyres on ambient air quality

Open burning of scrap (bicycle, motorcycle, car and truck) tyres (OBST) was simulated in the laboratory to investigate their impact on the ambient air quality. The tyre samples were burnt in combustion chamber, and gaseous pollutants (CO, NO₂ and SO₂) emitted were quantified, while concentrations and elemental compositions of emitted total suspended particulates (TSP) were determined. Emission level of SO₂ from all the tyre samples exceeded USEPA allowable (156.74 µg/m³) limit. CO due to car and truck tyres exceeded USEPA allowable (10,285.71 µg/m³) limit, while NO₂ concentration was below the allowable limit (56.33 µg/m³) only in bicycle tyre. 25% of all the gaseous pollutants emitted are within the Air Quality Index range of 101–150. TSP concentrations from all the tyre samples were higher than the Federal Ministry of Environment standard (250 µg/m³) for ambient TSP. There is strong correlation (R) of 0.885, 0.949 and 0.802 among all the gaseous (CO/NO₂, CO/SO₂ and NO₂/SO₂) pollutants, respectively, while the highest (0.999) and lowest (0.079) positive correlations were observed between Mg and Mn as well as Cd and Zn, respectively. The results of this study show that OBST emits hazardous pollutants, which pose serious threat to human health and environment.     

Chemistry and sulfur isotopic composition of precipitation at Bologna, Italy

Individual and monthly precipitation samples from the polluted atmosphere of Bologna (Emilia-Romagna province) were collected during March 1996 to May 1997 and analyzed for major ions in solution and S isotopes in dissolved SO₄.Weighted mean enrichment factors relative to seawater are found to be 1.0 for Na, 15.2 for K, 105 for Ca, 3.3 for Mg, 17.3 for SO₄ and 663 for HCO⁻₃. Very good positive correlations are observed for the Ca²⁺–Mg²⁺–HCO⁻₃–SO²⁻₄–NO⁻₃ system, indicating that dissolution of Ca (±Mg)-carbonate particles by H₂SO₄ and HNO₃ from combustion of oil and gas is a major process controlling the chemical composition of rain and snow. Na⁺ and Cl⁻ in monthly precipitation derive essentially from sea spray, but the contribution of Na⁺ from continental sources is appreciable in a number of individual rains. NH⁺₄ appears to be on average more abundant in spring and summer precipitation, its main sources being microbial activity in soils and application of fertilizers. K⁺ is probably of continental origin from soil dust.The S isotopic composition of SO₄ is systematically positive, with mean δ³⁴S values of +3.2±1.6‰ (n=40) in individual precipitation and +2.8±1.4‰ (n=12) in monthly precipitation. These isotopic compositions are interpreted in terms of a dominant contribution of S from anthropogenic emissions and subordinate contributions from biogenic and marine sources. Pollutant SO₄ is estimated to have a δ³⁴S value in the range +2.5 to +4.5‰, whereas a distinctive δ³⁴S of −4.5‰ or lower indicates SO₄ from oxidation of biogenic gases.The isotopic and chemical compositions of SO₄ do not depend on wind direction, thus testifying to a mostly local source for pollutant S in the Bologna atmosphere.     

Aerosol-trace gases interactions and their role in air quality control of Delhi city (India)

Atmospheric dust is considered to be the major cause of poor air quality due to its contribution to high particulate levels, but their interaction with the acidic gases helps in controlling the level of SO₂ and NO₂ through ambient neutralization reactions. In the present study, the interaction of acidic gases such as SO₂ and NO₂ with alkaline dust was investigated during October, 2013–July, 2014 at a site named as Babarpur located at the Trans-Yamuna region of Delhi. The concentration of SO₂ ranged from 10 to 170 μg/m³ with an average of 36 μg/m³ while that of NO₂ ranged from 15 to 54 μg/m³ with an average of 26?±?8 μg/m³. The results were observed to be well within the National Ambient Air Quality Standard (NAAQS) limits prescribed by the Central Pollution Control Board (CPCB). The average concentrations of SO₂ during day and night time were recorded as 31?±?18 and 43?±?53 μg/m³ respectively while the mean concentrations of NO₂ during day and night time were recorded as 26?±?7 and 27?±?12 μg/m³ respectively. A positive correlation between SO₄^2? and NO₃^? was also observed indicating their secondary aerosol formation. In aerosol phase, average concentrations of SO₄^2? during day and night time were 3.9?±?0.3 and 6.5?±?2.3 μg/m³ respectively while that of NO₃^? were 9.5?±?1.5 and 7.3?±?0.5 μg/m³ respectively. Molar ratios of Ca²⁺/SO₄^2?, NH₄⁺/SO₄^2?, and NH₄⁺/NO₃^? were observed as 8, 5, and 1.7 during daytime and 1.5, 0.4, and 0.8 during nighttime respectively. Such molar ratios confirmed high concentrations of sulphate (SO₄)^2? and low concentrations of nitrate (NO₃^?) during night time, thereby indicating different pathway of aerosol formation during day and night time. Surface morphology and elemental composition of aerosol samples showed various oval, globular, and platy shapes where the diameter varied from few nm to ~5 μm depending on their precursors. There were certain shapes like grossularite, irregular aggregate, grape-like, triangular, and flattened which indicate the crustal origin of aerosols and their possible role in SO₂ and NO₂ adsorption.     

Levels, seasonal variations, and health risks assessment of ambient air pollutants in the residential areas

People living in the urban area and the surrounding suburban area have disparities in exposure and health risks due to different levels of ambient air pollutants. The main objective of this study is to investigate the concentrations, seasonal variations, and related health risks of ambient air pollutants (PM₁₀, NO₂, and SO₂) in urban and suburban areas of Ningbo, China. The results showed that the average PM₁₀, NO₂, and SO₂ concentrations in the urban area were 85.2, 49.3, and 37.4 μg/m³, which were 1.13, 1.25, and 1.41 times the values of the suburban area during the period of March 2009 to February 2010. For the potential health risk analysis, the residents have been divided into four age categories namely, infants, children (1 year), children (8–10 years), and adults. The analysis took into account age-specific breathing rates, body weights for different age categories. The results showed that the potential health risks to respiratory disease for all age categories living in urban area were higher than those in suburban area.     

Computer simulated versus observed NO2 and SO2 emitted from elevated point source complex

ISC-AERMOD dispersion model was used to predict air dispersion plumes from an diesel power plant complex. Emissions of NO₂and SO₂from stacks (5 numbers) and a waste oil incinerator were studied to evaluate the pollutant dispersion patterns and the risk of nearby population. Emission source strengths from the individual point sources were also evaluated to determine the sources of significant attribution. Results demonstrated the dispersions of pollutants were influenced by the dominant easterly wind direction with the cumulative maximum ground level concentrations of 589.86 μg/m³ (1 h TWA NO₂) and 479.26 μg/m³ (1 h TWA SO₂). Model performance evaluation by comparing the predicted concentrations with observed values at ten locations for the individual air pollutants using rigorous statistical procedures were found to be in good agreement. Among all the emission sources within the facility complex, SESB-Power (diesel power plant) had been singled out as a significant source of emission that contributed >85% of the total pollutants emitted.     

Gaseous air pollution background estimation in urban,suburban, and rural environments

There is a great demand for estimating the ambient air pollutant background concentrations in order to assess the effectiveness of different emission control strategies. In this paper, the background concentrations of four pollutants, namely sulfur dioxide (SO₂), nitrogen oxides (NOx), carbon monoxide (CO), and ozone (O₃) pollutants in urban, suburban, and rural environments were investigated using Kolmogorov–Zurbenko (KZ) filter technique. Air quality data from monitoring stations over a period of 4 years (2007–2010) was analyzed for three locations in Kuwait, namely urban, suburban, and rural. The spatial and temporal (daily, weekly, and monthly) variations of the four pollutants were analyzed. The results show that the levels of ambient air pollutant background concentrations were high in the urban site compared to suburban and rural area. The diurnal variation of SO₂ concentration showed an early morning peak, while the diurnal variation of NOx concentration constituted has two peaks, one was in the early morning hours (5 to 8 a.m.) and the second was in nighttime hours (8 to 11 p.m.). These two peaks were observed at all three locations. The monthly background NOx concentration reached a maximum in winter and minimum in summer. Diurnal variation of CO concentration showed a similar trend to SO₂ concentrations in all three locations. Because of the photochemical reactions that occur in the atmosphere, the background concentration of O₃ showed an inverse relation with respect to background concentration of NOx.     

Temporal analysis of air pollution and its relationship with meteorological parameters in Bahrain, 2006–2012

The objective of this paper is to analyze temporal and seasonal trends of air pollution in Bahrain between 2006 and 2012 by utilizing datasets from five air quality monitoring stations. The non-parametric and robust Theil-Sen approach is employed to study quantitatively temporal variations of particulate matter (PM₁₀ and PM_2.5), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and ozone (O₃). The calculated annual concentrations for PM₁₀ and PM_2.5 in Bahrain were substantially higher than recommended World Health Organization (WHO) guideline standards. Results showed increasing trends for PM₁₀, PM_2.5, and SO₂ whereas O₃ and its precursor NO₂ showed decreasing behavior. The general increase in air pollution trends is in agreement with prediction of air pollution models for Middle East region due to economic growth, industrialization, and urbanization. The significances of long-term trends were examined. Additional to actual (unadjusted) trends, meteorological adjusted (deseasonalized) trends and seasonal trends were quantified. The box-plot analysis visually illustrated monthly variations of key air pollutants. It showed that only PM₁₀ and PM_2.5 exhibited seasonal pattern, and their concentrations increased during summer and decreased during winter. The effects of ambient air temperature, relative humidity, wind speed, and rainfall on particulate matter (PM) concentrations were further investigated. The Spearman correlation coefficient results demonstrated significant negative correlation between relative humidity and PM concentrations (??0.595 for PM₁₀ and ??0.526 for PM_2.5) while significant positive correlation was observed between temperature and PM concentrations (0.420 for PM₁₀ and 0.482 for PM_2.5).     

Identification of river water pollution characteristics based on projection pursuit and factor analysis

Human activities contribute different pollutants to receiving waters, often with significant variations in time and space. Therefore, integrating multiple parameters of water quality and their spatiotemporal variations is necessary to identify the pollution characteristics. Based on the water quality monitoring data with 12 parameters for 2 years at 22 sampling sites in the Cao-E River system, eastern China, the projection pursuit method was used to project all parameters and their temporal variations into a one-dimensional vector through two projections. Accordingly, we could easily assess the comprehensive water quality in different sampling sites and then classify their water pollution features. Factor analysis was then used to identify the pollution characteristics and potential sources. Results showed that all sampling sites for the river system could be classified into four groups: headwater sites (HS), agricultural nonpoint sources pollution sites (ANPS), point sources pollution sites (PSPS), and mixed sources pollution sites. Water quality in HS was good, containing only a few nutrients from the woodland runoff and soil erosion. For ANPS, the main pollutants were dissolved phosphorus, total P, and nitrate nitrogen (NO₃ ^?-N), mainly from farming land. For PSPS, ammonium nitrogen (NH₄ ⁺-N) and organic pollutants originated from industrial and municipal sewage. In HS and ANPS, NO₃ ^?-N was the main form of nitrogen, and a high ratio of NO₃ ^?-N/NH₄ ⁺-N was a remarkable characteristic, whereas NH₄ ⁺-N was the main form of nitrogen in PSPS. Except in HS, water quality in the other groups could not meet the local water quality control standard. Finally, suggestions were proposed for water pollution control for the different groups.     

Effects of multiple source pollution on a small Mediterranean river

The small Mediterranean riverine system of the Litheos river, which flows through the city of Trikala, and its drainage area are subjected to pollution from point and non point sources,which results in poor quality of surface waters. The pollution sources include urban activities, agriculture, industrial activities, handicrafts and traffic. The concentration levels and the geochemical behaviour of nutrients, trace metals and organic pollutants were studied during the period 1991–1992, in a project supported by the Municipality of Trikala. The simultaneous existence of several polluting sources leads to significant variations in the concentrations and distributions of main pollutants, which are elevated in the neighbourhood of polluting activities in various parts of the river (NO₃⁻ above the city, NH₃, NO₂⁻ and detergents near central rainwater collector, into the city, P04 below the city, near the waste water treatment plant, PAI-Is and metals in another river branch in the ‘industrial’ zone of the city). The appearance of concentration maxima of various pollutants in various parts of the river indicates environmental problems in the whole length of the river. The water quality is significantly influenced and in most cases is unsuitable for human consumption. The mean values of the main pollutants in Litheos (NO₃⁻ 4.0 mg N/1, NH₃ 0.23 mg N/1, NO₂⁻ 0.10 mg N/1, P 0.37 mg P/1, Cu 7.1 μg/l, Pb 4.8 μg/l, Zn 3.9 μg/l, Ni 12.8 μg/l, Cr 3.5 μg/l) characterize Litheos as a moderately polluted river, but the observation of eutrophication phenomena and the appearance of some high concentrations of heavy metals and/or organic pollutants in certain parts of the river reveal that a serious effort must be made in order to avoid further deterioration of Litheos water quality.     

Sampling and analytical procedures for the determination of VOCs released into air from natural and anthropogenic sources: A comparison between SPME (Solid Phase Micro Extraction) and ST (Solid Trap) methods

In the present study, two sampling and analytical methods for VOC determination in fumarolic exhalations related to hydrothermal-magmatic reservoirs in volcanic and geothermal areas and biogas released from waste landfills were compared: (a) Solid Traps (STs), consisting of three phase (Carboxen B, Carboxen C and Carbosieve S111) absorbent stainless steel tubes and (b) Solid Phase Micro Extraction (SPME) fibers, composed of DiVinylBenzene (DVB), Carboxen and PolyDimethylSiloxane. These techniques were applied to pre-concentrate VOCs discharged from: (i) low-to-high temperature fumaroles collected at Vulcano Island, Phlegrean Fields (Italy), and Nisyros Island (Greece), (ii) recovery wells in a solid waste disposal site located near Florence (Italy). A glass condensing system cooled with water was used to collect the dry fraction of the fumarolic gases, in order to allow more efficient VOC absorption avoiding any interference by water vapor and acidic gases, such as SO₂, H₂S, HF and HCl, typically present at relatively high concentrations in these fluids. Up to 37 organic species, in the range of 40–400 m/z, were determined by coupling gas chromatography to mass spectrometry (GC–MS). This study shows that the VOC compositions of fumaroles and biogas determined via SPME and ST are largely consistent and can be applied to the analysis of VOCs in gases released from different natural and anthropogenic environments. The SPME method is rapid and simple and more appropriate for volcanic and geothermal emissions, where VOCs are present at relatively high concentrations and prolonged gas sampling may be hazardous for the operator. The ST method, allowing the collection of large quantities of sample, is to be preferred to analyze the VOC composition of fluids from diffuse emissions and air, where these compounds are present at relatively low concentrations.     

Assessment of spatial variations of particulate matter (PM<Subscript>10</Subscript> and PM<Subscript>2.5</Subscript>) in Bahrain identified by air quality index (AQI)

The rapid urbanization, industrialization, modernization, and the frequent Middle Eastern dust storms have negatively impacted the ambient air quality in Bahrain. The objective of this study is to identify the most critical atmospheric air pollutants with emphasis on their potential risk to health based on calculated AQI (air quality index) values using EPA approach. The air quality datasets of particulate matters (PM₁₀ and PM_2.5), ozone (O₃), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and carbon monoxide (CO) were measured in January 2012 and August 2012 using five mobile air quality monitoring stations located at different governorates. The results of this study demonstrated that PM₁₀ and PM_2.5 are the most critical air pollutants in Bahrain with PM_2.5 prevailing during January 2012 and PM₁₀ prevailing during August 2012. The corresponding AQI categories were utilized to evaluate spatial variability of particulate matters in five governorates. The impact of meteorological factors such as ambient air temperature, wind speed, relative humidity, and total precipitation on ambient air quality were discussed. The analysis demonstrated that the highest PM₁₀ concentrations were observed in the Northern Governorate while the highest PM_2.5 concentrations were observed in the Capital, Central, and Northern Governorates during August 2012. It was observed that the levels of PM_2.5 pollution were higher within proximity of the industrial zone. The results suggested that the average PM_2.5/PM₁₀ ratio in August 2012 was lower than in January 2012 due to the Aeolian processes. This study concludes that higher wind speed, total precipitation, relative humidity rates, and lower ambient air temperature in January 2012 assisted with the dissipation of particulate matter thus lowering the pollution levels of both PM₁₀ and PM_2.5 in comparison to August 2012.     

Geochemical and mineralogical composition of black weathering crusts on limestones from seven different European countries

Twenty-seven samples of black weathering crust and host carbonates were studied from seven European countries (Germany, Hungary, Belgium, Czech Republic, France, Italy and Poland) representing 11 different sites. The samples were collected for sites for which long-term air pollution records are available. The mineralogical analyses (XRD, polarizing microscopy, SEM) have shown that despite decreasing SO₂ emissions crust samples are still very rich in gypsum. Further, in all host rock samples gypsum was also detected. Good correlations (R² > 0.9) were also found between water-soluble calcium and gypsum content and between sulphate and gypsum content both for black crusts and host rocks. The black gypsum crusts are four or five times richer in sulphate than the host rock. The conductivity of dissolved crust and host rock samples also shows a positive correlation with gypsum content of the samples. LA-ICP-MS analyses allowed the detection of high Pb-levels in black crusts and a negative shift in lead concentration at the crust/host rock transition. The lead content of the host rock is 2–5 mg/kg, while that of the crust is 3–25 mg/kg in the sample collected from Germany, while in the Belgian sample these values are 2–14 mg/kg and 80–870 mg/kg for the host rock and crust, respectively. The GC–MS technique allowed to detect the PAH content of black crusts and host rocks. The former one contains 0.6–15.6 (102.5) mg/kg, while in the host rock values between 0.2 and 2.4 mg/kg were found. The present study suggests that still large amounts of air pollution-related minerals and organic pollutants are found in the black weathering crusts of European carbonate buildings despite decreasing trends in air pollution.     

Tree-ring growth recovers,but δ13C and δ15N do not change,after the removal of point-source air pollution: a case study for poplar (Populus cathayana) in northwestern China

Pollution from urban centers and fossil fuel combustion can decrease forest growth and interfere with physiological processes. To evaluate whether tree growth and the carbon isotope ratio (δ¹³C) and nitrogen isotope ratio (δ¹⁵N) in tree rings can serve as proxies for air pollution, this study compared these indices for poplar (Populus cathayana) growing at urban and suburban locations in Lanzhou, in northwestern China. Basal area increment values were much lower at the urban site than in the suburbs from 1985 to 2009, were negatively correlated with NO₂ (r = ?0.56, p < 0.01) and SO₂ (r = ?0.52, p < 0.05) emissions from 1990 to 2009, and increased abruptly after the Lanzhou urban steel factory closed. Urban tree-ring δ¹³C values were not significantly correlated with NO₂ and SO₂ concentrations, and did not differ significantly between the two sites, indicating that other environmental effects (such as precipitation) masked the pollution effects. Tree-ring δ¹⁵N values in the urban samples were much higher than the suburban values. Such differences may be attributable to uptake of ¹⁵N-enriched compounds caused by a higher urban N deposition rate. Tree growth is a promising tool for detecting ecophysiological responses of trees to both diffuse and point-source air pollution, but δ¹³C and δ¹⁵N in poplar were not sensitive to point-source air pollution in a heavily polluted environment.     

A study of PM<Subscript>2.5</Subscript> and PM<Subscript>10</Subscript> concentrations in the atmosphere of large cities in Gansu Province,China, in summer period

Due to rapid economic growth of the country in the last 25 years, particulate matter (PM) has become a topic of great interest in China. The rapid development of industry has led to an increase in the haze created by pollution, as well as by high levels of urbanization. In 2012, the Chinese National Ambient Air Quality Standard (NAAQS) imposed ‘more strict’ regulation on the PM concentrations, i.e., 35 and 70 μg/m³ for annual PM_2.5 and PM₁₀ in average, respectively (Grade-II, GB3095-2012). The Pearson’s correlation coefficient was used to determine the linear relationship of pollution between pollution levels and weather conditions as well as the temporal and spatial variability among neighbouring cities. The goal of this paper was to investigate hourly mass concentration of PM_2.5 and PM₁₀ from June 1 to August 31, 2015 collected in the 11 largest cities of Gansu Province. This study has shown that the overall average concentrations of PM_2.5 and PM₁₀ in the study area were 26 and 66 μg/m³. In PM_2.5 episode days (when concentration was more than 75 μg/m³ for 24 hrs), the average concentrations of PM_2.5 was 2–3 times higher as compared to non-episode days. There were no observed clear differences during the weekday/weekend PM and other air pollutants (SO₂, NO₂, CO and O₃) in all the investigated cities.     

Chemical characteristics of PM<Subscript>10</Subscript> aerosols and airmass trajectories over Bay of Bengal and Arabian Sea during ICARB

For the first time, chemical characterization of PM₁₀ aerosols was attempted over the Bay of Bengal (BoB) and Arabian Sea (AS) during the ICARB campaign. Dominance of SO ₄ ^2? , NH ₄ ⁺ and NO ₃ ^? was noticed over both the regions which indicated the presence of ammonium sulphate and ammonium nitrate as major water soluble particles playing a very important role in the radiation budget. It was observed that all the chemical constituents had higher concentrations over Bay of Bengal as compared to Arabian Sea. Higher concentrations were observed near the Indian coast showing influence of landmass indicating that gaseous pollutants like SO₂, NH₃ and NO _x are transported over to the sea regions which consequently contribute to higher SO ₄ ^2? , NH ₄ ⁺ and NO ₃ ^? aerosols respectively. The most polluted region over BoB was 13°?19°N and 70°?90°E while it was near 11°N and 75°E over AS. Although the concentrations were higher over Bay of Bengal for all the chemical constituents of PM₁₀ aerosols, per cent non-sea salt (nss) fraction (with respect to Na) was higher over Arabian Sea. Very low Ca2+ concentration was observed at Arabian Sea which led to higher atmospheric acidity as compared to BoB. Nss SO ₄ ^2? alone contributed 48% of total water soluble fraction over BoB as well as AS. Ratios SO ₄ ^2? /NO _? ³ over both the regions (7.8 and 9 over BoB and AS respectively) were very high as compared to reported values at land sites like Allahabad (0.63) and Kanpur (0.66) which may be due to very low NO.3 over sea regions as compared to land sites. Air trajectory analysis showed four classes: (i) airmass passing through Indian land, (ii) from oceanic region, (iii) northern Arabian Sea and Middle East and (iv) African continent. The highest nss SO ₄ ^2? was observed during airmasses coming from the Indian land side while lowest concentrations were observed when the air was coming from oceanic regions. Moderate concentrations of nss SO2. 4 were observed when air was seen moving from the Middle East and African continent. The pH of rainwater was observed to be in the range of 5.9–6.5 which is lower than the values reported over land sites. Similar feature was reported over the Indian Ocean during INDOEX indicating that marine atmosphere had more free acidity than land atmosphere.     

Sources and processes governing rainwater chemistry in New Delhi,India

Rainwater plays an important role in scavenging of aerosols and gases from atmosphere, and its chemistry helps to understand the relative contributions of atmospheric pollution sources. The present work is aimed to understand and explain the sources, seasonal patterns and the processes thereof affecting rainwater chemistry in an urban environment of Delhi, India. Rainwater samples (n = 111) collected throughout the year in New Delhi showed alkalinity in general. Eight rainwater samples, collected in late monsoon and winter season, had pH less than 5.6 indicating that Delhi continues to face the prospects of acid rain despite the introduction of compressed natural gas as the clean fuel in city transport. Organic acids could be the possible contributors of acidity in rainwater samples having the fractional acidity (FA) value of 0.174, which is greater than the annual average FA (0.011) and the (Ca²⁺ + Mg²⁺ + NH₄ ⁺)/(SO₄ ^2? + NO₃ ^?) ration of more than one. Average acid neutralization factors of cations decrease in the order Ca²⁺ (1.01) > NH₄ ⁺ (0.77) > Mg²⁺ (0.10). However, neutralization by Ca²⁺ dominates only in summer season as cation-rich dust is transported from the Great Indian Thar Desert to this region by strong summer S–SW winds, while NH₄ ⁺ dominates in rainwater of other three sampling seasons. Identified dominant sources for soluble ions in rainwater are (1) non-silicate crustal source for carbonates and sulfates of Ca and Mg, (2) emissions from catalytic convertor-fitted vehicles and agriculture fields for NH₃ and (3) mixed anthropogenic sources for SO₄ ^2?, NO₃ ^? and Cl^?. Rainwater chemistry showed significant seasonal variations. This could be due to the changes in relative proportions of natural and anthropogenic sources of soluble ions to rainwater. Dominance of anthropogenic sources over crustal sources can result in acidic rains, which can adversely affect the environment and human health in this region.     

Chemical monitoring of volcanic gas using remote FT-IR spectroscopy at several active volcanoes in Japan

Chemical compositions of volcanic gases of several Japanese active volcanoes have been monitored from distant safe places since the beginning of the 1990s using an FT-IR spectral radiometer. For absorption measurements, an infrared light source behind volcanic gas emissions is necessary in a volcanic environment. In the early observations, infrared radiation from hot lava domes (Unzen volcano) and hot ground heated by high-temperature fumaroles (Usu, Aso, and Satsuma-Iwojima volcanoes) were used as infrared light sources. However, these sources were not available in many cases. This remote FT-IR method became more commonly applied to chemical monitoring of volcanic gases emitted from the summit or slopes of active volcanoes using scattered solar infrared light as infrared light sources (Sakurajima, Miyakejima, and Asama volcanoes). To date, eight species have been measured using this method: SO₂, HCl, HF, CO, CO₂, COS, SiF₄, and H₂O. The observations indicate that volcanic gases for each volcano have different chemical composition on a SO₂–HCl–HF ternary diagram in spite of similar tectonic settings, suggesting that vapor/melt volume ratios during volcanic gas formation differ among volcanoes. During more than 15 years of monitoring, chemical changes in volcanic gases attributable to ascent of magma were observed only at Asama, where HCl/SO₂ and HF/HCl ratios in the eruptive period were higher than those in non-eruptive period because of scrubbing of more soluble components in surface hydrothermal systems in the non-eruptive stage or solubility-controlled fractionation processes. Results show that these parameters are the most prospective ones among the various parameters measured using the remote FT-IR method to monitor volcanic activities.