- Air Quality, Atmospheric Chemistry, Atmospheric Aerosols, Chemistry, Sustainable Development, Environmental Science, and 18 moreEnvironmental Studies, Environmental Sustainability, Environmental Policy and Governance, Environmental Chemistry, Sustainable Production and Consumption, Biogeochemistry, Atmospheric Science, Sustainable Agriculture (Sustainability), Environmental Planning, Chemical Oceanography, Atmospheric Modeling, Global Environmental Change, Environmental Activism, HPLC-MS of environmental samples, Chromatographic analysis of environmental samples, Ion Chromatography, Black Carbon Emissions, and Sustainable water and fertilizer managementedit
. New particle formation (NPF), referring to the nucleation of molecular clusters and their subsequent growth into the cloud condensation nuclei (CCN) size range, is a globally significant and climate-relevant source of atmospheric... more
. New particle formation (NPF), referring to the nucleation of molecular clusters and their subsequent growth into the cloud condensation nuclei (CCN) size range, is a globally significant and climate-relevant source of atmospheric aerosols. Classical NPF exhibiting continuous growth from a few nanometers to the Aitken mode around 60–70 nm is widely observed in the planetary boundary layer (PBL) around the world, but not in central Amazonia. Here, classical NPF events are rarely observed in the PBL, but instead, NPF begins in the upper troposphere (UT), followed by downdraft injection of sub-50 nm (CN
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We have evaluated the spread of SARS-CoV-2 through Latin America and the Caribbean (LAC) region by means of a correlation between climate and air pollution indicators, namely, average temperature, minimum temperature, maximum temperature,... more
We have evaluated the spread of SARS-CoV-2 through Latin America and the Caribbean (LAC) region by means of a correlation between climate and air pollution indicators, namely, average temperature, minimum temperature, maximum temperature, rainfall, average relative humidity, wind speed, and air pollution indicators PM10, PM2.5, and NO2 with the COVID-19 daily new cases and deaths. The study focuses in the following LAC cities: Mexico City (Mexico), Santo Domingo (Dominican Republic), San Juan (Puerto Rico), Bogotá (Colombia), Guayaquil (Ecuador), Manaus (Brazil), Lima (Perú), Santiago (Chile), São Paulo (Brazil) and Buenos Aires (Argentina). The results show that average temperature, minimum temperature, and air quality were significantly associated with the spread of COVID-19 in LAC. Additionally, humidity, wind speed and rainfall showed a significant relationship with daily cases, total cases and mortality for various cities. Income inequality and poverty levels were also considered as a variable for qualitative analysis. Our findings suggest that and income inequality and poverty levels in the cities analyzed were related to the spread of COVID-19 positive and negative, respectively. These results might help decision-makers to design future strategies to tackle the spread of COVID-19 in LAC and around the world.
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Black carbon (BC) aerosols influence the Earth's atmosphere and climate, but their microphysical properties, spatiotemporal distribution, and long-range transport are not well constrained. This study presents airborne observations of the... more
Black carbon (BC) aerosols influence the Earth's atmosphere and climate, but their microphysical properties, spatiotemporal distribution, and long-range transport are not well constrained. This study presents airborne observations of the transatlantic transport of BC-rich African biomass burning (BB) smoke into the Amazon Basin using a Single Particle Soot Photometer (SP2) as well as several complementary techniques. We base our results on observations of aerosols and trace gases off the Brazilian coast onboard the HALO (High Altitude and LOng range) research aircraft during the ACRIDICON-CHUVA campaign in September 2014.
During flight AC19 over land and ocean at the northeastern coastline of the Amazon Basin, we observed a BC-rich layer at ∼3.5 km altitude with a vertical extension of ∼0.3 km. Backward trajectories suggest that fires in African grasslands, savannas, and shrublands were the main source of this pollution layer and that the observed BB smoke had undergone more than 10 d of atmospheric transport and aging over the South Atlantic before reaching the Amazon Basin. The aged smoke is characterized by a dominant accumulation mode, centered at about 130 nm, with a particle concentration of Nacc=850±330
cm−3. The rBC particles account for ∼15 % of the submicrometer aerosol mass and ∼40 % of the total aerosol number concentration. This corresponds to a mass concentration range from 0.5 to 2 µg m−3 (1st to 99th percentiles) and a number concentration range from 90 to 530 cm−3. Along with rBC, high cCO (150±30 ppb) and cO3
(56±9 ppb) mixing ratios support the biomass burning origin and pronounced photochemical aging of this layer. Upon reaching the Amazon Basin, it started to broaden and to subside, due to convective mixing and entrainment of the BB aerosol into the boundary layer. Satellite observations show that the transatlantic transport of pollution layers is a frequently occurring process, seasonally peaking in August/September.
By analyzing the aircraft observations together with the long-term data from the Amazon Tall Tower Observatory (ATTO), we found that the transatlantic transport of African BB smoke layers has a strong impact on the northern and central Amazonian aerosol population during the BB-influenced season (July to December). In fact, the early BB season (July to September) in this part of the Amazon appears to be dominated by African smoke, whereas the later BB season (October to December) appears to be dominated by South American fires. This dichotomy is reflected in pronounced changes in aerosol optical properties such as the single scattering albedo (increasing from 0.85 in August to 0.90 in November) and the BC-to-CO enhancement ratio (decreasing from 11 to 6 ng m−3 ppb−1). Our results suggest that, despite the high fraction of BC particles, the African BB aerosol acts as efficient cloud condensation nuclei (CCN), with potentially important implications for aerosol–cloud interactions and the hydrological cycle in the Amazon.
During flight AC19 over land and ocean at the northeastern coastline of the Amazon Basin, we observed a BC-rich layer at ∼3.5 km altitude with a vertical extension of ∼0.3 km. Backward trajectories suggest that fires in African grasslands, savannas, and shrublands were the main source of this pollution layer and that the observed BB smoke had undergone more than 10 d of atmospheric transport and aging over the South Atlantic before reaching the Amazon Basin. The aged smoke is characterized by a dominant accumulation mode, centered at about 130 nm, with a particle concentration of Nacc=850±330
cm−3. The rBC particles account for ∼15 % of the submicrometer aerosol mass and ∼40 % of the total aerosol number concentration. This corresponds to a mass concentration range from 0.5 to 2 µg m−3 (1st to 99th percentiles) and a number concentration range from 90 to 530 cm−3. Along with rBC, high cCO (150±30 ppb) and cO3
(56±9 ppb) mixing ratios support the biomass burning origin and pronounced photochemical aging of this layer. Upon reaching the Amazon Basin, it started to broaden and to subside, due to convective mixing and entrainment of the BB aerosol into the boundary layer. Satellite observations show that the transatlantic transport of pollution layers is a frequently occurring process, seasonally peaking in August/September.
By analyzing the aircraft observations together with the long-term data from the Amazon Tall Tower Observatory (ATTO), we found that the transatlantic transport of African BB smoke layers has a strong impact on the northern and central Amazonian aerosol population during the BB-influenced season (July to December). In fact, the early BB season (July to September) in this part of the Amazon appears to be dominated by African smoke, whereas the later BB season (October to December) appears to be dominated by South American fires. This dichotomy is reflected in pronounced changes in aerosol optical properties such as the single scattering albedo (increasing from 0.85 in August to 0.90 in November) and the BC-to-CO enhancement ratio (decreasing from 11 to 6 ng m−3 ppb−1). Our results suggest that, despite the high fraction of BC particles, the African BB aerosol acts as efficient cloud condensation nuclei (CCN), with potentially important implications for aerosol–cloud interactions and the hydrological cycle in the Amazon.
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The Amazon rain forest experiences the combined pressures from human-made deforestation and progressing climate change, causing severe and potentially disruptive perturbations of the ecosystem's integrity and stability. To intensify... more
The Amazon rain forest experiences the combined pressures from human-made deforestation and progressing climate change, causing severe and potentially disruptive perturbations of the ecosystem's integrity and stability. To intensify research on critical aspects of Amazonian biosphere-atmosphere exchange, the Amazon Tall Tower Observatory (ATTO) has been established in the central Amazon Basin. Here we present a multi-year analysis of backward trajecto-ries to derive an effective footprint region of the observatory, which spans large parts of the particularly vulnerable eastern basin. Further, we characterize geospatial properties of the footprint regions, such as climatic conditions, distribution of ecoregions, land cover categories, deforestation dynamics , agricultural expansion, fire regimes, infrastructural development , protected areas, and future deforestation scenarios. This study is meant to be a resource and reference work, helping to embed the ATTO observations into the larger context of human-caused transformations of Amazonia. We conclude that the chances to observe an unperturbed rain forest-atmosphere exchange at the ATTO site will likely decrease in the future, whereas the atmospheric signals from human-made and climate-change-related forest perturbations will increase in frequency and intensity.
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Wildfires inject large amounts of black carbon (BC) particles into the atmosphere, which can reach the lowermost stratosphere (LMS) and cause strong radiative forcing. During a 14-month period of observations on board a passenger aircraft... more
Wildfires inject large amounts of black carbon (BC) particles into the atmosphere, which can reach the lowermost stratosphere (LMS) and cause strong radiative forcing. During a 14-month period of observations on board a passenger aircraft flying between Europe and North America, we found frequent and widespread biomass burning (BB) plumes, influencing 16 of 160 flight hours in the LMS. The average BC mass concentrations in these plumes (∼140 ng·m −3 , standard temperature and pressure) were over 20 times higher than the background concentration (∼6 ng·m −3) with more than 100-fold enhanced peak values (up to ∼720 ng·m −3). In the LMS, nearly all BC particles were covered with a thick coating. The average mass equivalent diameter of the BC particle cores was ∼120 nm with a mean coating thickness of ∼150 nm in the BB plume and ∼90 nm with a coating of ∼125 nm in the background. In a BB plume that was encountered twice, we also found a high diameter growth rate of ∼1 nm·h −1 due to the BC particle coatings. The observed high concentrations and thick coatings of BC particles demonstrate that wildfires can induce strong local heating in the LMS and may have a significant influence on the regional radiative forcing of climate. black carbon | biomass burning | climate change | high altitude | mixing state E xtended summer dry seasons, drier vegetation, and decreased winter precipitation driven by climate change are leading to more frequent wildland fires in many parts of the world, with an increased duration and severity of burning (1-3). Especially in the northern high latitudes, where there is less intensive land management, a post-1750 increase in biomass burning (BB) events has been observed using the charcoal accumulation in sediments (charcoal index increased by ∼0.4) (4). Wildland fires release large amounts of greenhouse gases, aerosol precursors, and primary aerosols including black carbon (BC) (5-7). Via deep convective clouds and synoptic weather systems associated with warm conveyor belts, a fraction of these emissions can be transported into the upper troposphere (UT) (8-12) and low-ermost stratosphere (LMS) (13-16). At these high altitudes, BC particles can have a much stronger (up to ∼10 times) radiative forcing efficiency than at lower altitudes (17-22) due to less-attenuated solar radiation, increased radiation from the back-scattering of clouds, and longer residence time (23, 24). Moreover , an increasing BC concentration near the tropopause (TP) can also alter the vertical temperature profile, leading to a stabilizing effect in the atmosphere below, and can influence cloud and precipitation development in lower layers, resulting in a negative forcing contribution (22, 25).
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The Amazon rainforest is a sensitive ecosystem experiencing the combined pressures of progressing deforestation and climate change. Its atmospheric conditions oscillate between biogenic and biomass burning (BB) dominated states. The... more
The Amazon rainforest is a sensitive ecosystem experiencing the combined pressures of progressing deforestation and climate change. Its atmospheric conditions oscillate between biogenic and biomass burning (BB) dominated states. The Amazon further represents one of the few remaining continental places where the atmosphere approaches pristine conditions during occasional wet season episodes. The Amazon Tall Tower Observatory (ATTO) has been established in central Amazonia to investigate the complex interactions between the rainforest ecosystem and the atmosphere. Physical and chemical aerosol properties have been analyzed continuously since 2012. This paper provides an in-depth analysis of the aerosol's optical properties at ATTO based on data from 2012 to 2017. The following key results have been obtained. – The aerosol scattering and absorption coefficients at 637 nm, σ sp,637 and σ ap,637 , show a pronounced sea-sonality with lowest values in the clean wet season (mean ± SD: σ sp,637 = 7.5 ± 9.3 M m −1 ; σ ap,637 = 0.68 ± 0.91 M m −1) and highest values in the BB-polluted dry season (σ sp,637 = 33±25 M m −1 ; σ ap,637 = 4.0 ± 2.2 M m −1). The single scattering albedo at 637 nm, ω 0 , is lowest during the dry season (ω 0 = 0.87 ± 0.03) and highest during the wet season (ω 0 = 0.93 ± 0.04). – The retrieved BC mass absorption cross sections, α abs , are substantially higher than values widely used in the literature (i.e., 6.6 m 2 g −1 at 637 nm wavelength), likely related to thick organic or inorganic coatings on the BC cores. Wet season values of α abs = 11.4 ± Published by Copernicus Publications on behalf of the European Geosciences Union. 12818 J. Saturno et al.: Black and brown carbon over central Amazonia 1.2 m 2 g −1 (637 nm) and dry season values of α abs = 12.3 ± 1.3 m 2 g −1 (637 nm) were obtained. – The BB aerosol during the dry season is a mixture of rather fresh smoke from local fires, somewhat aged smoke from regional fires, and strongly aged smoke from African fires. The African influence appears to be substantial, with its maximum from August to October. The interplay of African vs. South American BB emissions determines the aerosol optical properties (e.g., the fractions of black vs. brown carbon, BC vs. BrC). – By analyzing the diel cycles, it was found that particles from elevated aerosol-rich layers are mixed down to the canopy level in the early morning and particle number concentrations decrease towards the end of the day. Brown carbon absorption at 370 nm, σ ap,BrC,370 , was found to decrease earlier in the day, likely due to photo-oxidative processes. – BC-to-CO enhancement ratios, ER BC , reflect the variability of burnt fuels, combustion phases, and atmospheric removal processes. A wide range of ER BC between 4 and 15 ng m −3 ppb −1 was observed with higher values during the dry season, corresponding to the lowest ω 0 levels (0.86–0.93). – The influence of the 2009/2010 and 2015/2016 El Niño periods and the associated increased fire activity on aerosol optical properties was analyzed by means of 9-year σ sp and σ ap time series (combination of ATTO and ZF2 data). Significant El Niño-related enhancements were observed: in the dry season, σ sp,637 increased from 24 ± 18 to 48 ± 33 M m −1 and σ ap, 637 from 3.8 ± 2.8 to 5.3 ± 2.5 M m −1. – The absorption Ångström exponent, å abs , representing the aerosol absorption wavelength dependence, was mostly <1.0 with episodic increases upon smoke advec-tion. A parameterization of å abs as a function of the BC-to-OA mass ratio for Amazonian aerosol ambient measurements is presented. The brown carbon (BrC) contribution to σ ap at 370 nm was obtained by calculating the theoretical BC å abs , resulting in BrC contributions of 17 %–29 % (25th and 75th percentiles) to σ ap 370 for the entire measurement period. The BrC contribution increased to 27 %–47 % during fire events under El Niño-related drought conditions from September to Novem-ber 2015. The results presented here may serve as a basis to understand Amazonian atmospheric aerosols in terms of their interactions with solar radiation and the physical and chemical-aging processes that they undergo during transport. Additionally , the analyzed aerosol properties during the last two El Niño periods in 2009/2010 and 2015/2016 offer insights that could help to assess the climate change-related potential for forest-dieback feedbacks under warmer and drier conditions.
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The long-range transport (LRT) of trace gases and aerosol particles plays an important role for the composition of the Amazonian rain forest atmosphere. Sulfate aerosols originate to a substantial extent from LRT sources and play an... more
The long-range transport (LRT) of trace gases and aerosol particles plays an important role for the composition of the Amazonian rain forest atmosphere. Sulfate aerosols originate to a substantial extent from LRT sources and play an important role in the Amazonian atmosphere as strongly light-scattering particles and effective cloud condensation nuclei. The transatlantic transport of volcanic sulfur emissions from Africa has been considered as a source of particulate sulfate in the Amazon; however, direct observations have been lacking so far. This study provides observational evidence for the influence of emissions from the Nyamuragira–Nyiragongo volcanoes in Africa on Amazonian aerosol properties and atmospheric composition during September 2014. Comprehensive ground-based and airborne aerosol measurements together with satellite observations are used to investigate the volcanic event. Under the volcanic influence, hourly mean sulfate mass concentrations in the submicron size range reached up to 3.6µgm−3 at the Amazon Tall Tower Observatory, the highest value ever reported in the Amazon region. The substantial sulfate injection increased the aerosol hygroscopicity with κ values up to 0.36, thus altering aerosol–cloud interactions over the rain forest. Airborne measurements and satellite data indicate that the transatlantic transport of volcanogenic aerosols occurred in two major volcanic plumes with a sulfate-enhanced layer between 4 and 5km of altitude. This study demonstrates how African aerosol sources, such as volcanic sulfur emissions, can substantially affect the aerosol cycling and atmospheric processes in Amazonia.
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Size-resolved measurements of atmospheric aerosol and cloud condensation nuclei (CCN) concentrations and hygroscopicity were conducted over a full seasonal cycle at the remote Amazon Tall Tower Observatory (ATTO)
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In the Amazonian atmosphere, the aerosol coarse mode comprises a complex, diverse, and variable mixture of bioaerosols emitted from the rain forest ecosystem, long-range transported Saharan dust (we use Sahara as shorthand for the dust... more
In the Amazonian atmosphere, the aerosol coarse mode comprises a complex, diverse, and variable mixture of bioaerosols emitted from the rain forest ecosystem, long-range transported Saharan dust (we use Sahara as shorthand for the dust source regions in Africa north of the Equator), marine aerosols from the Atlantic Ocean, and coarse smoke particles from deforestation fires. For the rain forest, the coarse mode particles are of significance with respect to biogeochemical and hydrological cycling, as well as ecology and biogeography. However, knowledge on the physic-ochemical and biological properties as well as the ecological role of the Amazonian coarse mode is still sparse. This study presents results from multi-year coarse mode measurements at the remote Amazon Tall Tower Observatory (ATTO) site. It combines online aerosol observations, selected remote sensing and modeling results, as well as dedicated coarse mode sampling and analysis. The focal points of this study are a systematic characterization of aerosol coarse mode abundance and properties in the Amazonian atmosphere as well as a detailed analysis of the frequent, pulse-wise intrusion of African long-range transport (LRT) aerosols (comprising Saharan dust and African biomass burning smoke) into the Amazon Basin. We find that, on a multi-year time scale, the Amazonian coarse mode maintains remarkably constant concentration levels (with 0.4 cm −3 and 4.0 µg m −3 in the wet vs. 1.2 cm −3
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Deriving absorption coefficients from Aethalome-ter attenuation data requires different corrections to compensate for artifacts related to filter-loading effects, scattering by filter fibers, and scattering by aerosol particles. In this... more
Deriving absorption coefficients from Aethalome-ter attenuation data requires different corrections to compensate for artifacts related to filter-loading effects, scattering by filter fibers, and scattering by aerosol particles. In this study, two different correction schemes were applied to seven-wavelength Aethalometer data, using multi-angle absorption photometer (MAAP) data as a reference absorption measurement at 637 nm. The compensation algorithms were compared to five-wavelength offline absorption measurements obtained with a multi-wavelength absorbance an-alyzer (MWAA), which serves as a multiple-wavelength reference measurement. The online measurements took place in the Amazon rainforest, from the wet-to-dry transition season to the dry season (June–September 2014). The mean absorption coefficient (at 637 nm) during this period was 1.8 ± 2.1 Mm −1 , with a maximum of 15.9 Mm −1. Under these conditions, the filter-loading compensation was negligible. One of the correction schemes was found to artificially increase the short-wavelength absorption coefficients. It was found that accounting for the aerosol optical properties in the scattering compensation significantly affects the absorption Ångström exponent (å ABS) retrievals. Proper Aethalometer data compensation schemes are crucial to retrieve the correct å ABS , which is commonly implemented in brown carbon contribution calculations. Additionally, we found that the wavelength dependence of uncompensated Aethalome-ter attenuation data significantly correlates with the å ABS retrieved from offline MWAA measurements.
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The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere 1. Most field studies of atmospheric aerosols over continents are... more
The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere 1. Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin (for example, ref. 2) and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions 3–5 , but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear 6–8. Here we present aircraft-and ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. This rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.
Size-resolved long-term measurements of atmospheric aerosol and cloud condensation nuclei (CCN) concentrations and hygroscopicity were conducted at the remote Amazon Tall Tower Observatory (ATTO) in the central Amazon Basin over a 1-year... more
Size-resolved long-term measurements of atmospheric aerosol and cloud condensation nuclei (CCN) concentrations and hygroscopicity were conducted at the remote Amazon Tall Tower Observatory (ATTO) in the central Amazon Basin over a 1-year period and full seasonal cycle (March 2014–February 2015). The measurements provide a climatology of CCN properties characteristic of a remote central Amazonian rain forest site. The CCN measurements were continuously cycled through 10 levels of supersaturation (S = 0.11 to 1.10 %) and span the aerosol particle size range from 20 to 245 nm. The mean critical diameters of CCN activation range from 43 nm at S = 1.10 % to 172 nm at S = 0.11 %. The particle hygroscopicity exhibits a pronounced size dependence with lower values for the Aitken mode (κ Ait = 0.14 ± 0.03), higher values for the accumulation mode (κ Acc = 0.22 ± 0.05), and an overall mean value of κ mean = 0.17 ± 0.06, consistent with high fractions of organic aerosol. The hygroscopicity parameter, κ, exhibits remarkably little temporal variability: no pronounced diurnal cycles, only weak seasonal trends, and few short-term variations during long-range transport events. In contrast, the CCN number concentrations exhibit a pronounced seasonal cycle, tracking the pollution-related seasonality in total aerosol concentra-Published by Copernicus Publications on behalf of the European Geosciences Union. 15710 M. L. Pöhlker et al.: Long-term observations of cloud condensation nuclei in the Amazon rain forest – Part 1 tion. We find that the variability in the CCN concentrations in the central Amazon is mostly driven by aerosol particle number concentration and size distribution, while variations in aerosol hygroscopicity and chemical composition matter only during a few episodes. For modeling purposes, we compare different approaches of predicting CCN number concentration and present a novel parametrization, which allows accurate CCN predictions based on a small set of input data.
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We use a global chemical transport model (GEOS-Chem) to interpret observed light-absorbing aerosols in Amazonia during the wet season. Observed aerosol properties , including black carbon (BC) concentration and light absorption, at the... more
We use a global chemical transport model (GEOS-Chem) to interpret observed light-absorbing aerosols in Amazonia during the wet season. Observed aerosol properties , including black carbon (BC) concentration and light absorption, at the Amazon Tall Tower Observatory (ATTO) site in the central Amazon have relatively low background levels but frequently show high peaks during the study period of January–April 2014. With daily temporal resolution for open fire emissions and modified aerosol optical properties , our model successfully captures the observed variation in fine/coarse aerosol and BC concentrations as well as aerosol light absorption and its wavelength dependence over the Amazon Basin. The source attribution in the model indicates the important influence of open fire on the observed variances of aerosol concentrations and absorption, mainly from regional sources (northern South America) and from northern Africa. The contribution of open fires from these two regions is comparable, with the latter becoming more important in the late wet season. The analysis of correlation and enhancement ratios of BC versus CO suggests transport times of < 3 days for regional fires and ∼ 11 days for African plumes arriving at ATTO during the wet season. The model performance of long-range transport of African plumes is also evaluated with observations from AERONET, MODIS, and CALIOP. Simulated absorption aerosol optical depth (AAOD) averaged over the wet season is lower than 0.0015 over the central Amazon, including the ATTO site. We find that more than 50 % of total absorption at 550 nm is from BC, except for the northeastern Amazon and the Guianas, where the influence of dust becomes significant (up to 35 %). The brown carbon contribution is generally between 20 and 30 %. The distribution of absorption Ångström exponents (AAE) suggests more influence from fossil fuel combustion in the southern part of the basin (AAE ∼ 1) but more open fire and dust influence in the northern part (AAE > 1.8). Uncertainty analysis shows that accounting for absorption due to secondary organic aerosol (SOA) and primary biogenic aerosol (PBA) particles could result in differences of < 8 and 5–40 % in total absorption, respectively.
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A micro/nanoparticle bismuth film electrode (BiFE) has been developed for the determination of lead and cadmium by anodic stripping voltammetry (ASV) and trace levels of chromium by adsorptive stripping voltammetry (AdSV). Chromium was... more
A micro/nanoparticle bismuth film electrode (BiFE) has been developed for the determination of lead and cadmium by anodic stripping voltammetry (ASV) and trace levels of chromium by adsorptive stripping voltammetry (AdSV). Chromium was detected in a flow cell. Bismuth was electrodeposited on
a hydrated aluminum oxide template, which was previously coated on a glassy-carbon (GC) electrode. Then, the template was selectively removed by soaking the electrode in a 0.1 M NaOH solution for 30 min, leaving a dispersed bismuth film covering the electrode surface; such electrodeposits had a particulate appearance, which was observed by scanning electron microscopy (SEM). The voltammetric analyses from a chromium solution on a -NPs/BiFE provided a limit of detection (LOD) equal to 0.12 ng L−1 (n = 6) and a slope of 0.27 C/ng L−1 (R2 = 0.9903). The signals registered were more than 50 times higher than the peaks obtained from a conventional BiFE. The analysis of aqueous solutions of Cd and Pb gave also lower LOD and higher sensitivity against the conventional BiFe experiments.
a hydrated aluminum oxide template, which was previously coated on a glassy-carbon (GC) electrode. Then, the template was selectively removed by soaking the electrode in a 0.1 M NaOH solution for 30 min, leaving a dispersed bismuth film covering the electrode surface; such electrodeposits had a particulate appearance, which was observed by scanning electron microscopy (SEM). The voltammetric analyses from a chromium solution on a -NPs/BiFE provided a limit of detection (LOD) equal to 0.12 ng L−1 (n = 6) and a slope of 0.27 C/ng L−1 (R2 = 0.9903). The signals registered were more than 50 times higher than the peaks obtained from a conventional BiFE. The analysis of aqueous solutions of Cd and Pb gave also lower LOD and higher sensitivity against the conventional BiFe experiments.