Concentrations and biosphere–atmosphere fluxes of inorganic trace gases and associated ionic aerosol counterparts over the Amazon rainforest

Abstract. The Amazon rainforest presents a unique, natural laboratory for the study of surface-atmosphere interactions. Its alternation between a near-pristine, marine-influenced atmosphere during the wet season, and a vulnerable system affected by periodic intrusions of anthropogenic pollution during the dry season, provides an opportunity to investigate some fundamental aspects of boundary-layer chemical processes. This study presents the first simultaneous hourly measurements of concentrations, fluxes and deposition velocities of the inorganic trace gases NH3, HCl, HONO, HNO3 and SO2 and their water-soluble aerosol counterparts NH4+, Cl−, NO2−, NO3− and SO42− over the Amazon. Species concentrations were measured in the dry season (from 6 October to 5 November 2017), at the Amazon Tall Tower Observatory (ATTO) in Brazil, using a two-point gradient, wet-chemistry instrument (Gradient of Aerosols and Gases Online Registration, GRAEGOR) sampling at 42 m and 60 m. Fluxes and deposition velocities were derived from the concentration gradients using a modified form of the aerodynamic gradient method corrected for measurement within the roughness sub-layer. Findings from this campaign include observations of elevated concentrations of NH3 and SO2 partially driven by long-range transport (LRT) episodes of pollution, and the substantial influence of coarse Cl− and NO3− particulate on overall aerosol mass burdens. From the flux measurements, the dry season budget of total reactive nitrogen dry deposition at the ATTO site was estimated as −2.9 kg N ha−1 a−1. HNO3 and HCl were deposited continuously at a rate close to the aerodynamic limit. SO2 was deposited with an average daytime surface resistance (Rc) of 28 s m−1, whilst aerosol components showed average surface deposition velocities of 2.8 and 2.7 mm s−1 for SO42− and NH4+. Deposition rates of NO3

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Concentrations and biosphere–atmosphere fluxes of inorganic trace gases and associated ionic aerosol counterparts over the Amazon rainforest

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-15551-2020 ◽

2020 ◽

Vol 20 (24) ◽

pp. 15551-15584

Author(s):

Robbie Ramsay ◽

Chiara F. Di Marco ◽

Matthias Sörgel ◽

Mathew R. Heal ◽

Samara Carbone ◽

...

Keyword(s):

Dry Deposition ◽

Tropical Rainforest ◽

Trace Gases ◽

Anthropogenic Pollution ◽

Early Morning ◽

Dry Season ◽

Water Soluble ◽

Amazon Rainforest ◽

Wet Season ◽

Deposition Velocities

Abstract. The Amazon rainforest presents a unique, natural laboratory for the study of surface–atmosphere interactions. Its alternation between a near-pristine marine-influenced atmosphere during the wet season and a vulnerable system affected by periodic intrusions of anthropogenic pollution during the dry season provides an opportunity to investigate some fundamental aspects of boundary-layer chemical processes. This study presents the first simultaneous hourly measurements of concentrations, fluxes, and deposition velocities of the inorganic trace gases NH3, HCl, HONO, HNO3, and SO2 as well as their water-soluble aerosol counterparts NH4+, Cl−, NO2-, NO3- and SO42- over the Amazon. Species concentrations were measured in the dry season (from 6 October to 5 November 2017), at the Amazon Tall Tower Observatory (ATTO) in Brazil, using a two-point gradient wet-chemistry instrument (GRadient of AErosols and Gases Online Registration, GRAEGOR) sampling at 42 and 60 m. Fluxes and deposition velocities were derived from the concentration gradients using a modified form of the aerodynamic gradient method corrected for measurement within the roughness sub-layer. Findings from this campaign include observations of elevated concentrations of NH3 and SO2 partially driven by long-range transport (LRT) episodes of pollution and the substantial influence of coarse Cl− and NO3- particulate on overall aerosol mass burdens. From the flux measurements, the dry season budget of total reactive nitrogen dry deposition at the ATTO site was estimated as −2.9 kg N ha-1a-1. HNO3 and HCl were deposited continuously at a rate close to the aerodynamic limit. SO2 was deposited with an average daytime surface resistance (Rc) of 28 s m−1, whilst aerosol components showed average surface deposition velocities of 2.8 and 2.7 mm s−1 for SO42- and NH4+, respectively. Deposition rates of NO3- and Cl− were higher at 7.1 and 7.8 mm s−1, respectively, reflecting their larger average size. The exchange of NH3 and HONO was bidirectional, with NH3 showing emission episodes in the afternoon and HONO in the early morning hours. This work provides a unique dataset to test and improve dry deposition schemes for these compounds for tropical rainforest, which have typically been developed by interpolation from conditions in temperate environments. A future campaign should focus on making similar measurements in the wet season in order to provide a complete view of the annual pattern of inorganic trace gas and coarse aerosol biosphere–atmosphere exchange over tropical rainforest.

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Spatial and temporal heterogeneity in aerosol radiative effects over ecological area in south China: Composition and transmission implications

10.5194/egusphere-egu2020-4351 ◽

2020 ◽

Author(s):

Ma Yining ◽

Xin Jinyuan

Keyword(s):

Organic Carbon ◽

Radiative Forcing ◽

Dry Season ◽

Water Soluble ◽

Chemical Components ◽

Radiative Effects ◽

Wet Season ◽

Cooling Effects ◽

Ecological Region ◽

Aerosol Radiative

Abstract: Ecological region in southern China has been perennially affected by monsoon climate and anthropogenic emissions, resulting in complex aerosol components and frequent long-range transport. In this study, a Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model is applied to estimate aerosol radiative forcing (ARF) and multiple aerosol observation datasets is used to estimate the aerosol chemical components and optical properties. The aerosol loading and the radiative effects in the ecological region exhibited strong seasonal changes. The average major components (NH4+, NO3&#8722;, SO42&#8722;) in Total water soluble ionic (TWSI) ,organic carbon (OC) concentration, the ratio of organic carbon to element carbon (OC/EC) and biogenic secondary organic aerosol (BSOA) tracers were 3.20&#177;1.22 &#956;g&#183;m-3, 2.19&#177;1.39 &#956;g&#183;m-3, 3.17 and 74.00&#177;35.23 ng&#183;m-3 in the dry season and 2.22&#177;0.91 &#956;g&#183;m-3, 3.14&#177;1.62 &#956;g&#183;m-3, 7.13 and 186.34&#177;113.82 ng&#183;m-3 in the wet season, respectively. The average radiative forcing at the top of atmosphere (TOA) is -11.73&#177;11.36 W/m2 and -0.41&#177;10.08 W/m2 in dry and wet season. When the aerosol single scattering albedo (SSA) less than 0.9, the retrieve frequency in wet season reached account for 75%. The increase of OC and BSOA transformed by forests in the wet season weaken the cooling effects. However, the dry season is mainly composed of anthropogenic inorganic aerosols, which enhances the scattering effect. The aerosol observation baseline also verified the seasonal variation of ARF in the ecological region. Driven by multiple factors such as meteorological conditions, emission sources, and the mixed state of particulate matter, the transport patterns of air masses in ecological area exhibits completely opposite affects to ARF.

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Real-time measurements of ammonia, acidic trace gases and water-soluble inorganic aerosol species at a rural site in the Amazon Basin

Atmospheric Chemistry and Physics ◽

10.5194/acp-4-967-2004 ◽

2004 ◽

Vol 4 (4) ◽

pp. 967-987 ◽

Cited By ~ 138

Author(s):

I. Trebs ◽

F. X. Meixner ◽

J. Slanina ◽

R. Otjes ◽

P. Jongejan ◽

...

Keyword(s):

Biomass Burning ◽

Amazon Basin ◽

Limit Of Detection ◽

Trace Gases ◽

Water Soluble ◽

Rural Site ◽

Wet Season ◽

Inlet System ◽

Mixing Ratios ◽

Inorganic Aerosol

Abstract. We measured the mixing ratios of ammonia (NH3), nitric acid (HNO3), nitrous acid (HONO), hydrochloric acid (HCl), sulfur dioxide (SO2 and the corresponding water-soluble inorganic aerosol species, ammonium (NH4+), nitrate (NO3-), nitrite (NO2-), chloride (Cl- and sulfate (SO42-), and their diel and seasonal variations at a pasture site in the Amazon Basin (Rondônia, Brazil). This study was conducted within the framework of LBA-SMOCC (Large Scale Biosphere Atmosphere Experiment in Amazonia - Smoke Aerosols, Clouds, Rainfall and Climate: Aerosols from Biomass Burning Perturb Global and Regional Climate). Sampling was performed from 12 September to 14 November 2002, extending from the dry season (extensive biomass burning activity), through the transition period to the wet season (background conditions). Measurements were made continuously using a wet-annular denuder (WAD) in combination with a Steam-Jet Aerosol Collector (SJAC) followed by suitable on-line analysis. A detailed description and verification of the inlet system for simultaneous sampling of soluble gases and aerosol compounds is presented. Overall measurement uncertainties of the ambient mixing ratios usually remained below 15%. The limit of detection (LOD) was determined for each single data point measured during the field experiment. Median LOD values (3σ-definition) were ≤0.015ppb for acidic trace gases and aerosol anions and ≤0.118ppb for NH3 and aerosol NH4+. Mixing ratios of acidic trace gases remained below 1ppb throughout the measurement period, while NH3 levels were an order of magnitude higher. Accordingly, mixing ratios of NH4+ exceeded those of other inorganic aerosol contributors by a factor of 4 to 10. During the wet season, mixing ratios decreased by nearly a factor of 3 for all compounds compared to those observed when intensive biomass burning took place. Additionally, N-containing gas and aerosol species featured pronounced diel variations. This is attributed to strong relative humidity and temperature variations between day and night as well as to changing photochemistry and stability conditions of the planetary boundary layer. HONO exhibited a characteristic diel cycle with high mixing ratios at nighttime and was not completely depleted by photolysis during daylight hours.

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Origin of water-soluble organic aerosols at the Maïdo high-altitude observatory, Réunion Island in the tropical Indian Ocean

10.5194/acp-2021-277 ◽

2021 ◽

Author(s):

Sharmine Akter Simu ◽

Yuzo Miyazaki ◽

Eri Tachibana ◽

Henning Finkenzeller ◽

Jérôme Brioude ◽

...

Keyword(s):

Indian Ocean ◽

High Altitude ◽

Radiative Forcing ◽

Numerical Models ◽

Stable Carbon Isotope ◽

Organic Aerosols ◽

Dry Season ◽

Water Soluble ◽

Spatial And Temporal Variation ◽

Wet Season

Abstract. The tropical and subtropical Indian Ocean (IO) is expected to be a significant source of water-soluble organic aerosols (WSOAs), which are important factors relevant to cloud condensation nuclei and ice nuclei of aerosol particles. Current atmospheric numerical models significantly underestimate the budget of organic aerosols and their precursors, especially over tropical oceans. This is primarily due to poor knowledge of sources and the paucity of observations of these parameters considering spatial and temporal variation over the tropical open ocean. To evaluate the contribution of sources to WSOA as well as their formation processes, submicrometer aerosol sampling was conducted at the high-altitude Maïdo observatory (21.1° S, 55.4° E, 2,160 m a.s.l), located on the remote island of La Réunion in the southwest IO. The aerosol samples were continuously collected during local daytime and nighttime, which corresponded to the ambient conditions of the marine boundary layer (MBL) and free troposphere (FT), respectively, from March 15 to May 24, 2018. Chemical analysis showed that organic matter was the dominant component of submicrometer water-soluble aerosol (~45 ± 17 %) during the wet season (March 15–April 23), whereas sulfate dominated (~77 ± 17 %) during the dry season (April 24–May 24). Measurements of the stable carbon isotope ratio of water-soluble organic carbon (WSOC) suggested that marine sources contributed significantly to the observed WSOC mass in both the MBL and the FT in the wet season, whereas a mixture of marine and terrestrial sources contributed to WSOC in the dry season. The distinct seasonal changes in the dominant source of WSOC were also supported by Lagrangian trajectory analysis. Positive matrix factorization analysis suggested that marine secondary OA dominantly contributed to the observed WSOC mass (~70 %) during the wet season, whereas mixtures of marine and terrestrial sources contributed during the dry season in both MBL and FT. Overall, this study demonstrates that the effect of marine secondary sources is likely important up to the FT in the wet season, which may be responsible for cloud formation as well as direct radiative forcing over oceanic regions.

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Application of multivariate statistical analysis in the assessment of groundwater quality of Tan Thanh district, Ba Ria – Vung Tau province

Science & Technology Development Journal - Science of The Earth & Environment ◽

10.32508/stdjsee.v1im2.446 ◽

2017 ◽

Vol 1 (M2) ◽

pp. 66-72

Author(s):

Au Hai Nguyen ◽

Ngan Thi Khanh Phan ◽

Thuy Thi Thanh Hoang ◽

Ngoc Nguyen Hong Phan

Keyword(s):

Cluster Analysis ◽

Statistical Analysis ◽

Groundwater Quality ◽

Multivariate Statistical Analysis ◽

Anthropogenic Pollution ◽

Dry Season ◽

Wet Season ◽

Multivariate Statistical ◽

Rock Interaction ◽

And Cluster Analysis

In the present study, Multivariate Statistical Analysis (MSA) such as Principle Component Analysis (PCA) and Cluster Analysis (CA) were applied to determine the temporal and spatial variations of groundwater quality in Tan Thanh district, Ba Ria – Vung Tau province. Groundwater samples were collected from 18 monitoring wells in April (dry season) and October (wet season) during the year 2012. Fifteen parameters (pH, TH, TDS, Cl-, F-, NO3-, SO42-, Cr6+, Cu2+, Ca2+, Mg2+, Na+, K+, HCO3- and Fe2+) were selected for MSA. PCA identified a reduced number of mean three latent factors of groundwater quality. Three factors called salinization, water-rock interaction and anthropogenic pollution explanined 70,5% (dry season) and 71.28% (wet season) of the variances. Cluster analysis revealed two main different groups of similarities between the sampling sites. This study presents the necessity of MSA in order to extract more precise information from a huge minitoring data, which will be usefull to groundwater quality management.

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Quantifying deposition pathways of Ozone at a rainforest site (ATTO) in the central Amazon basin

10.5194/egusphere-egu2020-19455 ◽

2020 ◽

Author(s):

Matthias Sörgel ◽

Anywhere Tsokankunku ◽

Stefan Wolff ◽

Alessandro Araùjo ◽

Pedro Assis ◽

...

Keyword(s):

Surface Temperature ◽

Eddy Covariance ◽

Amazon Basin ◽

Leaf Surface ◽

Dry Season ◽

Leaf Wetness ◽

Gas Phase Reactions ◽

Deposition Velocities ◽

Flux Measurements ◽

The City

Direct eddy covariance flux measurements of O3 in tropical forests are sparse and deposition velocities of O3 for tropical forest have large uncertainties in models. Therefore, we measured O3 fluxes at different heights ( 4 m, 12 m, 46 m and 81 m), which is 2 levels within canopy (below crown layer) and two levels above. At the same levels heat and CO2 fluxes were measured by eddy covariance to differentiate upper canopy fluxes from understory and soil fluxes and to infer stomatal conductance based on the inverted Penman-Monteith equation. Further measurements include the profiles of O3, NOx, CO2 and H2O which are used to calculate storage fluxes and reactions of O3 with NOx within the air volume. Additionally, leaf surface temperature and leaf wetness were measured in the upper canopy (26 m) to infer their influence on the non-stomatal deposition. The measurements took place at the ATTO (Amazon Tall Tower Observatory) site that is located about 150 km northeast of the city of Manaus in the Amazon rainforest. (02&#176;08&#8217;38.8&#8217;&#8217;S, 58&#176;59&#8217;59.5&#8217;&#8217;W). The climate in this region is characterized by a rainy (350 mm around March) and a dry season (ca. 80 mm in September). During the wet months, the air quality is close to pristine, while strong pollution from biomass burning is evident in the dry season. Therefore, we will present results from two intensive campaigns (3- 4 flux levels) for the rainy season (March to May) and the dry season (September to December) 2018.&#160;The focus of the analysis is the partitioning between a) the crown layer and understory and b) stomatal and non-stomatal deposition with a further analysis of the non-stomatal pathways. Non-stomatal deposition is analyzed by quantifying gas-phase reactions of O3 with NOx and an estimate of O3 reactivity by VOCs. Furthermore, the remaining (surface) deposition is analyzed according to its relations with leaf surface temperature and leaf wetness.

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Physico-chemical characterization of urban aerosols from specific combustion sources in West Africa at Abidjan in Côte d'Ivoire and Cotonou in Benin in the frame of the DACCIWA program

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-5327-2020 ◽

2020 ◽

Vol 20 (9) ◽

pp. 5327-5354 ◽

Cited By ~ 4

Author(s):

Aka Jacques Adon ◽

Catherine Liousse ◽

Elhadji Thierno Doumbia ◽

Armelle Baeza-Squiban ◽

Hélène Cachier ◽

...

Keyword(s):

Organic Carbon ◽

West Africa ◽

Cote D'ivoire ◽

Côte D’Ivoire ◽

Dry Season ◽

Water Soluble ◽

Wet Season ◽

Cote D’Ivoire ◽

Côte D'ivoire ◽

Combustion Sources

Abstract. Urban air pollution in West Africa has yet to be well characterized. In the frame of DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa) program, intensive measurement campaigns were performed in Abidjan (Côte d'Ivoire) and Cotonou (Benin), in dry (January 2016 and 2017) and wet (July 2015 and 2016) seasons, at different sites chosen to be representative of African urban combustion sources, i.e., domestic fires (ADF), traffic (AT) and waste burning (AWB) sources in Abidjan and traffic source in Cotonou (CT). Both the size distribution of particulate matter (PM) and their chemical composition including elemental carbon (EC), organic carbon (OC), water-soluble organic carbon (WSOC), water-soluble inorganic ions (WSI) and trace metals were examined. Results show very high PM concentrations at all sites and a well-marked seasonality as well as a strong spatial variation. The average PM2.5 mass concentrations during the wet season are 517.3, 104.1, 90.3, and 69.1 µg m−3 at the ADF, CT, AT, and AWB sites, respectively. In the dry season, PM2.5 concentrations decrease to 375.7 µg m−3 at the ADF site, while they increase to 269.7, 141.3, and 175.3 µg m−3 at the CT, AT, and AWB sites, respectively. The annual PM2.5 levels at almost all sites are significantly higher than the WHO guideline level of 10 µg m−3. As for PM mass, (EC) and (OC) concentrations are also maximal at the ADF site, accounting for up to 69 % of the total PM mass. Such a high content is mainly linked to wood burning for domestic cooking and commercial food smoking activities. Dust contributions are dominant at CT (57 %–80 %), AT (20 %–70 %), and AWB (30 %–69 %) sites and especially in the coarse and fine-particle modes at the CT site and in the coarse fraction at the AT site, which may be explained by the impact of long-range desert-dust transport and resuspended particles from the roads, in addition to anthropogenic sources. The contributions of WSI to the total PM mass, mainly driven by chloride, nitrate, and calcium in the fine and/or large particles, are highly variable according to the sites but remain less than 30 %. Values are generally 1–3 times higher in the wet season than in the dry season. This is due not only to anthropogenic emissions but also to nitrate formation by reaction processes and natural emissions. The concentrations of trace elements reflect well the trends in dust at the traffic and AWB sites, with a predominance of Al, Na, Ca, Fe, and K, keys markers of crustal dust. This study constitutes an original database that characterizes specific African combustion sources.

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Molecular composition of dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls and fatty acids in atmospheric aerosols from Tanzania, East Africa during wet and dry seasons

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-2235-2013 ◽

2013 ◽

Vol 13 (4) ◽

pp. 2235-2251 ◽

Cited By ~ 43

Author(s):

S. L. Mkoma ◽

K. Kawamura

Keyword(s):

Fatty Acids ◽

Dicarboxylic Acids ◽

Dry Season ◽

Water Soluble ◽

Molecular Composition ◽

Wet Season ◽

Dry Seasons ◽

Pm2.5 And Pm10 ◽

Related Compounds ◽

Wet And Dry Seasons

Abstract. Atmospheric aerosol samples of PM2.5 and PM10 were collected during the wet and dry seasons in 2011 from a rural site in Tanzania and analysed for water-soluble dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls, and fatty acids using a gas chromatography/flame ionization detector (GC/FID) and GC/mass spectrometry. Here we report the molecular composition and sources of diacids and related compounds for wet and dry seasons. Oxalic acid (C2) was found as the most abundant diacid species followed by succinic and/or malonic acids whereas glyoxylic acid and glyoxal were the dominant ketoacid and α-dicarbonyl, respectively in both seasons in PM2.5 and PM10. Mean concentration of C2 in PM2.5 (121 ± 47 ng m−3) was lower in wet season than dry season (258 ± 69 ng m−3). Similarly, PM10 samples showed lower concentration of C2 (169 ± 42 ng m−3) in wet season than dry season (292 ± 165 ng m−3). Relative abundances of C2 in total diacids were 65% and 67% in PM2.5 and 65% and 64% in PM10 in the wet and dry seasons, respectively. Total concentrations of diacids (289–362 ng m−3), ketoacids (37.8–53.7 ng m−3), and α-dicarbonyls (5.7–7.8 ng m−3) in Tanzania are higher than those reported at a rural background site in Nylsvley (South Africa) but comparable or lower than those reported from sites in Asia and Europe. Diacids and ketoacids were found to be present mainly in PM2.5 in both seasons (total α-dicarbonyls in the dry season), suggesting a production of organic acids from pyrogenic sources and photochemical oxidations. Averaged contributions of total diacids to aerosol total carbon were 1.4% in PM2.5 and 2.1% in PM10 during wet season and 3.3% in PM2.5 and 3.9% in PM10 during dry season whereas those to water-soluble organic carbon were 2.2% and 4.7% in PM2.5 during wet season and 3.1% and 5.8% in PM10 during dry season. The higher ratios in dry season suggest an enhanced photochemical oxidation of organic precursors probably via heterogeneous reactions on aerosols under strong solar radiation. Strong positive correlations were found among diacids and related compounds as well as good relations to source tracers in both seasons, suggesting a mixed source from natural biogenic emissions, biomass burning, biofuel combustion, and photochemical production.

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Speciation Analysis of Nickel in the Soils of Tejgaon Industrial Area of Bangladesh

Bangladesh Journal of Scientific and Industrial Research ◽

10.3329/bjsir.v44i1.2717 ◽

1970 ◽

Vol 44 (1) ◽

pp. 87-108 ◽

Cited By ~ 2

Author(s):

AS Chamon ◽

MN Mondol ◽

B Faiz ◽

MH Rahman ◽

SF Elahi

Keyword(s):

Organic Matter ◽

Organic Matter Content ◽

Industrial Area ◽

Dry Season ◽

Soil Samples ◽

Water Soluble ◽

Industrial Wastes ◽

City Centre ◽

Wet Season ◽

Tolerable Level

The main focus of the study is Tejgaon industrial area which is located within the Dhaka City Corporation and about 5 km north of the city centre. The industries around the study area like battery, chemical manufacturing, electrical and electronic, metal finishing, mining, paint and dye, textiles, pharmaceuticals, pesticides, etc, discharge heavy metals like Ni with their effluents and wastes. At Tejgaon soil the minimum pH value was 5.3 and the maximum 7.6 (at 26°C). High buffering capacity resulting from high soil organic matter content (4.87-11.55%) probably influenced soil pH. Electrical conductivity (EC) (25-551 μS/cm) and organic matter (OM) (4.87-11.55%) contents were also influenced by the industrial wastes and effluents of the factories. In the wet season, the average Ni concentration in different soil fractions was 1.69, 4.16, 13.21 and 93.12 mg kg-1 in water-soluble, NH4OAc extractable, DTPAextractable and total fractions respectively. Comparing wet season and dry season sampling data, total Ni concentrations in different locations were higher in the dry season and the mean concentration of total Ni was 223.89 mg kg-1, which was more than 4 times higher than the tolerable limit. Concentrations of total Ni in different locations during wet season were found above the natural background level with few exceptions. Ni concentration in the group of tolerable level was 21% (>022-=50 mg kg-1) and 75% (=50 mg kg-1) soil samples were found in the group of in excess of tolerable level during wet season. During dry season, 11% of Ni (=50 mg kg-1) samples were in the normal range and 89% (>50 mg kg-1) soil samples were found in the group of in excess of tolerable level. Ni concentration during dry season samples in different extraction i.e in NH4OAc extractable, DTPA extractable and in total fraction was found to decrease with distance away from the disposal point source due to dilution of the effluent and water. The decreasing tendency with distance indicates the accumulation of metals by the industrial operations. Key words: Speciation,Tejgaon soil, Industrial area, Nickel. doi: 10.3329/bjsir.v44i1.2717 Bangladesh J. Sci. Ind. Res. 44(1), 87-108, 2009

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Isoprene photochemistry over the Amazon rainforest

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1524136113 ◽

2016 ◽

Vol 113 (22) ◽

pp. 6125-6130 ◽

Cited By ~ 44

Author(s):

Yingjun Liu ◽

Joel Brito ◽

Matthew R. Dorris ◽

Jean C. Rivera-Rios ◽

Roger Seco ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Amazon Basin ◽

Anthropogenic Pollution ◽

Amazon Rainforest ◽

Urban Region ◽

Peroxy Radicals ◽

Wet Season ◽

Transport Models ◽

Air Masses ◽

A Value

Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO2) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK + MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4–0.6. This result implies a ratio of the reaction rate of ISOPOO with HO2 to that with NO of approximately unity. A value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (>1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (<60 ppt). This abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest.

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