Anthropogenic Fraction Research Articles

A better representation of VOC chemistry in WRF-Chem and its impact on ozone over Los Angeles.

The declining trend in vehicle emissions has underscored the growing significance of Volatile Organic Compound (VOC) emissions from Volatile Chemical Products (VCP). However, accurately representing VOC chemistry in simplified chemical mechanisms remains challenging due to its chemical complexity including speciation and reactivity. Previous studies have predominantly focused on VOCs from fossil fuel sources, leading to an underrepresentation of VOC chemistry from VCP sources. We developed an integrated chemical mechanism, RACM2B-VCP, that is compatible with WRF-Chem and is aimed to enhance the representation of VOC chemistry, particularly from VCP sources, within the present urban environment. Evaluation against the Air Quality System (AQS) network data demonstrates that our model configured with RACM2B-VCP reproduces both the magnitude and spatial variability of O3 as well as PM2.5 in Los Angeles. Furthermore, evaluation against comprehensive measurements of O3 and PM2.5 precursors from the Reevaluating the Chemistry of Air Pollutants in California (RECAP-CA) airborne campaign and the Southwest Urban NO x and VOC Experiment (SUNVEx) ground site and mobile laboratory campaign, confirm the model's accuracy in representing NOx and many VOCs and highlight remaining biases. Although there exists an underprediction in the total VOC reactivity of observed VOC species, our model with RACM2B-VCP exhibits good agreement for VOC markers emitted from different sectors, including biogenic, fossil fuel, and VCP sources. Through sensitivity analyses, we probe the contributions of VCP and fossil fuel emissions to total VOC reactivity and O3. Our results reveal that 52% of the VOC reactivity and 35% of the local enhancement of MDA8 O3 arise from anthropogenic VOC emissions in Los Angeles. Significantly, over 50% of this anthropogenic fraction of either VOC reactivity or O3 is attributed to VCP emissions. The RACM2B-VCP mechanism created, described, and evaluated in this work is ideally suited for accurately representing ozone for the right reasons in the present urban environment where mobile, biogenic, and VCP VOCs are all important contributors to ozone formation.

Trace elements in PM2.5aerosols in East Asian outflow in the spring of 2018: emission, transport, and source apportionment

Abstract. Trace metals in aerosol particles impact Earth's radiative budget, human health, and ocean biogeochemistry. Semi-continuous measurements of the elemental composition of fine-mode (PM2.5) aerosols were conducted using an automated X-ray fluorescence analyzer on a remote island of Japan during the spring of 2018. Temporal variations in mass concentrations of geochemically important elements for this period, such as Pb, Cu, Si, Fe, and Mn, and their relationships with the emission tracers, carbon monoxide (CO) and black carbon (BC), were reported. The Integrated Massively Parallel Atmospheric Chemical Transport (IMPACT) model was used to evaluate the source apportionment of these components and was evaluated in terms of emissions and wet removal processes. Pb and Cu originated mainly from anthropogenic sources (98 % and 93 % on average, respectively) over the East Asian continent. Positive correlations of Pb and Cu with BC and CO and the similarity of their concentration-weighted trajectories indicated that the emission sources of these metals share the region where the large CO (and BC) emission sources are located and that CO can be regarded as a tracer of continental anthropogenic emissions. The air masses with minimized impacts of the wet removal during transport were extracted to elucidate the “top-down” emission ratio of Pb and Cu to CO, which were, for the first time, evaluated as 152.7 and 63.1 µg g−1, respectively, during the spring of 2018 in the East Asian outflow. The analysis of the tagged tracer simulations by the IMPACT model confirmed that BC and Si could be used as tracers for anthropogenic and dust emissions, respectively, during the observation period. The source apportionment of Fe and Mn in PM2.5 aerosols was conducted using Si and BC tracers, which revealed that the anthropogenic contribution was 17 % and 44 % on average, respectively. Based on the air mass origins of Fe and Mn, their anthropogenic fraction varied from 2 % to 29 % and 9 % to 68 %, respectively, during the high-PM2.5-concentration periods. However, despite the non-dominant anthropogenic contributions of Fe, they could adversely affect human health and ocean biogeochemistry, owing to their higher water solubility. The modeled BC, Pb, Cu, and Fe were evaluated by separately diagnosing their emission and transport. Ratios of modeled to observed concentrations for these components were analyzed in terms of the accumulated precipitation along the transport from the East Asian continent. The current model simulations were found to overestimate the emissions (based on the Community Emissions Data System, CEDS v2021-02-05) of BC by 44 % and underestimate Cu by 45 %, anthropogenic Fe by 28 % in East Asia, and the wet deposition rates for BC and Pb. Overall, Cu in East Asia exhibited a different nature from BC and Pb in terms of emission sources and wet removal.

Radiological assessment of urban soil samples in the residents of a central Anatolian volcanic province, Turkey

ABSTRACT The concentration of natural and anthropogenic radionuclides, emanation fraction (EF), and mass (χM) and area (χA) exhalation rate of 222Rn in urban soil samples collected from dwelling areas in Nevşehir city located in a region known as the central Anatolian volcanic province of Turkey were determined using gamma-ray spectroscopy. The average activity concentrations of 226Ra, 228Ra, 40K and 137Cs were measured as 60.2 ± 3.8, 50.1 ± 2.8, 631.0 ± 29.7 and 5.5 ± 0.4 Bq/kg, respectively. The average concentration of 222Rn in soil and air was estimated as 27 kBq/m3 and 84 Bq/m3, respectively. The average values of EF, χM and χA were found as 20%, 25.4 μBq/kg⋅s and 20.2 mBq/m2⋅s, respectively. The average values of outdoor absorbed gamma dose rate, external and internal annual effective dose and lifetime cancer risk estimated for radiological assessment were found as 85 nGy/h, 104 µSv/y, 797 µSv/y and 4.1 × 10−4, respectively.

Ecological features of floristic structure of devastated lands of the RightBank Forest-Steppe of Ukraine

In the proposed article we highlight the features of the floristic structure of the devastated lands of the Right Bank forest-steppe on the example of the Andriikovetskyi sand quarry. The research was conducted using general scientific methods (analysis, synthesis, monitoring), field study and in-house research, herbarium specimens were collected and a summary of quarry flora was compiled. Ecological conditions within the mining facilities are formed individually, which is associated with the degree of anthropogenic disturbance and natural conditions of the region. It was found, that after the decommissioning of the study facility, the initial stages of plant succession within the quarry was influenced by such factors as unstable hydroclimatic conditions (significant influence is the availability of moisture for plants), elemental composition and structure of sand substrate, uneven terrain. During three years of research, 71 species of plants were identified by the collected herbarium material, the leading families are Asteraceae (14 genuses), which is typical for holarctic flora; Rosaceae (10 genuses); Fabaceae (5 genuses). It has been determined that according to Raunkier’s classification, hemicryptophytes predominate in the quarry territory, according to Serebryakov’s classification — grass polycarpics. It was found, that the structure of aboveground shoots is dominated by rosetteless species, the structure of the root system — species with a taproot. Were analyzed, that ecological structure of flora displays the adaptation of plants to environmental conditions and affects their distribution in ecotopes: the ratio of plants to light is dominated by heliophytes distributed in the most illuminated areas (for example, Galiummollugo L., Medicago sativa L., Trifolium pratense L.); to moisture — mesophytes, to temperature — megatherms, to nutrition — mesotrophs. The presence of a significant number of mesophytic and mesotrophic species indicates the beginning of the accumulation of elements and humic compounds necessary for the development of a stable phytocenosis. Among cenomorphs, the most numerous are ruderants (22.5% of the total number of species), silvants (11.3%), stepants (11.3%) and transitional types: pratant — ruderants (11.3%) and pratant-silvants (8.4%). According to the degree of adaptation to anthropogenic changes, autochthonous and allochthonous fractions were distinguished, and the share of apophytic species (23 species) prevails over adventitious (14 species). Among the apophytes, has been identified the most numerous group — aboriginal species that have completely switched to anthropogenic habitats (13 species); among the adventitious faction predominate species that are fully naturalized on anthropogenic ecotopes (11 species), at the time of settlement there are species listed before and after the XVI century. This differentiation of floristic composition confirms the need for renaturalization measures to stabilize edaphic conditions, which will accelerate the formation of zonal flora and increase biodiversity

Isoprene in urban Atlantic forests: Variability, origin, and implications on the air quality of a subtropical megacity

Biosphere-atmosphere interactions play a key role in urban chemistry because of biogenic volatile organic compound (BVOC) emissions. Of the BVOC, isoprene is the most emitted compound; however, it also has anthropogenic origins in urban areas. In this study, we aimed to investigate the spatio-temporal variability and atmospheric impacts of biogenic and anthropogenic isoprene in the subtropical megacity of São Paulo (MASP), Brazil. Several measurement campaigns were conducted in three different urban Atlantic forests (Matão, PEFI, and RMG), and an urban background site (IAG); this equated to a total of 268 samples for the 2018–2019 period. For all sampling points, daytime average concentrations of isoprene were two to three times higher during the rainy season (IAG: 1.75 ± 0.93 ppb; Matão: 0.87 ± 0.35 ppb; PEFI: 0.50 ± 0.30 ppb; RMG: 0.37 ± 0.18 ppb), than those observed during the dry season (IAG: 0.46 ± 0.24 ppb; Matão: 0.31 ± 0.17 ppb; PEFI: 0.17 ± 0.11 ppb; RMG: 0.11 ± 0.07 ppb). Average isoprene concentrations were similar to those observed in other places worldwide, with the exception of the Amazon forest. Our results indicate differences in isoprene concentrations between sites, suggesting that environmental conditions such as the urban heat island and vegetation types, may play a role in spatial variability. Estimates of the isoprene fraction indicated that the biogenic fraction (85%) surpassed the anthropogenic fraction during the rainy season. By contrast, the anthropogenic fraction (52%) exceeded the biogenic fraction during dry periods. These fractions have an impact on potentially forming secondary pollutants gaseous (ozone formation potential: 7.19–33.32 μg m−3), and aerosols (secondary organic aerosols formation potential: 0.41–1.88 μg m−3). These results highlight the role of biogenic isoprene and its potential impact on urban air quality in subtropical megacities; this requires further investigation under future climate change scenarios.

Emission Ratios and Source Identification of VOCs in Moscow in 2019–2020

Measurements of CO and 15 volatile organic compounds (VOCs) at the IAP-RAS (A.M. Obukhov Institute of Atmospheric Physics) site located in the center of Moscow were analyzed. Acetaldehyde, ethanol, 1.3-butadiene, isoprene, toluene and C-8 aromatics were established to be the main ozone precursors in the observed area, providing up to 82% of the total ozone formation potential of the VOCs measured. Diurnal and seasonal variations of the compounds are discussed. The concentrations of anthropogenic VOCs (acetaldehyde, benzene, 1.3-butadiene, toluene, and C-8 aromatics) did not exceed their maximum permissible levels, reaching their maxima in summer and autumn in the morning and evening hours. Biogenic ethanol and isoprene were the highest in summer midday but their concentrations were low enough (up to 4 and 0.4 ppbv, respectively) due to small vegetation area around the site. Emission ratios (ERs) for the main ozone precursors—acetaldehyde, ethanol, 1.3-butadiene, isoprene, toluene, and C-8 aromatics—were estimated from two-sided linear regression fits using benzene and CO as tracers for anthropogenic emissions, with spatial and temporal filters being applied to account for the influence of chemistry and local emission sources. The best estimates of ERs were obtained using benzene as a reference species. Anthropogenic fractions of VOCs (AFs) were then estimated. As expected, acetaldehyde, toluene, 1.3-butadiene, and C8aromatics were entirely anthropogenic and emitted mainly from urban vehicle exhausts throughout the day, both in summer and in winter. AFs of isoprene and ethanol did not exceed 30% and 50% in summer, respectively, during both daytime and nighttime hours. In winter, the anthropogenic fractions of isoprene and ethanol were slightly higher (up to 35% and 60%, respectively).

Source apportionment of sulphate in the High Arctic by a 10 yr-long record from Gruvebadet Observatory (Ny-Ålesund, Svalbard Islands)

A long-term study of the chemical composition of Arctic aerosol has been carried out at the Gruvebadet Observatory located in Ny-Ålesund since 2010. The PM10 aerosol has been collected continuously every year on a daily/2-day basis, each covering at least the spring and summer months, and the ionic content was evaluated using simultaneously three IC-systems. In order to determine the contribution of different sources (sea spray, crustal, biogenic and anthropogenic) to the total sulphate budget, specific markers and characteristic marker-to-sulphate ratios were used (Na+, Ca2+ and methanesulphonate). The obtained data set was then compared with the one from the Zeppelin Observatory, also located in Ny-Ålesund. The anthropogenic fraction resulted to be the major component, reaching the highest value in March and April during the Haze period, followed by the sea salt, biogenic and crustal ones. The comparison between the two datasets confirms the seasonal trend of these fractions even though some differences in magnitude were observed, likely due to discrepancies in the timing and resolution of sampling campaigns. The temporal profile of the anthropogenic fraction, evaluated in both sites, showed no evident continuous trend from 2010 to 2019, although the 2017–19 period revealed higher concentration with respect to the previous years. Focusing on single months, two opposite trends in the sulphate budget along 10 years were observed for March against April and September. Whereas a decrease was observed in March, April and September showed an increase in the monthly mean concentration values. Finally, the correlation between the non-sea salt non-crustal sulphate fraction and ammonium was evaluated. An increase in the ammonia neutralizing effect, resulting in a decrease in aerosol acidity, was observed at GVB, from the 2010 to 2017, then stabilized. Conversely, a decrease in the concentration of ammonia was found in ZEP since 2015, leading to an increase of the nssSO42−/NH4+ ratio in the same period.

Local emissions and secondary pollutants cause severe PM2.5 elevation in urban air at the south edge of the North China Plain: Results from winter haze of 2017–2018 at a mega city

Severe haze occurrence in the north of the North China Plain (NCP) is recognized as a consequence of the regional transport of pollutants initially from the south and then the rapid formation of secondary pollutants in the local air. However, the origin of pollutants causing haze in the southern NCP has not yet been elucidated even through careful data observation. Based on the contents of water-soluble inorganic ions in PM2.5 samples collected during two severe haze episodes in Zhengzhou, a mega city located on the southern edge of the NCP, we estimated the contributions of local primary emissions and secondary pollutants to haze occurrence. On average, Na+, K+, and Ca2+ mainly originated from anthropogenic sources, and their anthropogenic fractions had proportions of 97.5%, 93.9%, and 76.5% in their respective total mass. Anions Cl− and SO42− substantially originated from not only produced substantially via secondary formation but also from primary emissions, and their primary proportions in their respective total mass were 51.1% and 30.8%. In contrast, NH4+ and NO3− were dominated by secondary formation. The increase in PM2.5 was mainly caused by the formation of secondary inorganic (29.1%) and organic species (57.2%) and the primary anthropogenic emissions (12.5%). These results indicated that the haze at the southern edge of the NCP was mainly caused by pollutants in the local areas. Compared to the haze in the northern NCP, the haze in the southern NCP edge had a higher PM2.5 mass concentration and a higher proportion of secondary species, but a lower proportion of primary species, indicating the high heterogeneity of winter haze over the NCP.

Decadal variations in natural and anthropogenic aerosol optical depth over the Bay of Bengal: the influence of pollutants from Indo-GangeticPlain.

Perennial increase in atmospheric pollution over the Bay of Bengal (BoB) and South China Sea is reported due to increase in human population and industrial activity in South and Southeast Asia. Based on total aerosol optical depth (AOD) derived from MODIS (moderate resolution imaging resolution imaging spectroradiometer), natural and anthropogenic fractions were derived. The seasonality and spatial variability in rate of increase in total, natural, and anthropogenic AOD fractions were examined over the BoB using data collected between 2001 and 2019. Both total and anthropogenic AOD displayed statistically significant rate of increase in the northwest BoB (NWB) and western coastal BoB (WCB) regions during 2001 to 2019 whereas the long-term changes are insignificant in the other regions of BoB. Significant increase in AOD in the NWB and WCB regions is mainly contributed by dominant outflow of anthropogenic emissions from Indo-Gangetic Plain (IGP) area of Indian subcontinent. The magnitude of AOD decreased by half from northern BoB to equatorial region due to increase in distance from the source region. The contribution of anthropogenic AOD was >70% to total AOD with higher contribution during winter and lower during summer. The rate of increase in both total and anthropogenic AOD was close to 0.104 and 0.099 per decade in the NWB and 0.069 and 0.059 per decade in the WCB region between 2001 and 2019. The rate of increase in total and anthropogenic AOD decreased from 2001-2009 (0.164 and 0.115 per decade respectively) to 2010-2019 (0.068 and 0.076 per decade respectively) in the NWB region. Significant increase in anthropogenic AOD by 50 and 30% was observed during El Niño and La Niña periods respectively than normal year in both northwest BoB (NWB) and western coastal (WCB) regions due to change in strength and direction of winds. Although some fraction of anthropogenic AOD is found over the entire BoB, significant rate of increase in anthropogenic AOD is found only about 23% of the area of BoB than hitherto reported as entire BoB. The impact of atmospheric deposition of anthropogenic aerosols on biogeochemical processes, such as primary production and ocean acidification, needs further evaluation.

The effect of natural and anthropogenic nutrient and sediment loads on coral oxidative stress on runoff-exposed reefs

Recently, corals on the Great Barrier (GBR) have suffered mass bleaching. The link between ocean warming and coral bleaching is understood to be due to temperature-dependence of complex physiological processes in the coral host and algal symbiont. Here we use a coupled catchment-hydrodynamic-biogeochemical model, with detailed zooxanthellae photophysiology including photoadaptation, photoacclimation and reactive oxygen build-up, to investigate whether natural and anthropogenic catchment loads impact on coral bleaching on the GBR. For the wet season of 2017, simulations show the cross-shelf water quality gradient, driven by both natural and anthropogenic loads, generated a contrasting zooxanthellae physiological state on inshore versus mid-shelf reefs. The relatively small catchment flows and loads delivered during 2017, however, generated small river plumes with limited impact on water quality. Simulations show the removal of the anthropogenic fraction of the catchment loads delivered in 2017 would have had a negligible impact on bleaching rates.

On the attribution of industrial-era glacier mass loss to anthropogenic climate change

Abstract. Around the world, small ice caps and glaciers have been losing mass and retreating since the start of the industrial era. Estimates are that this has contributed approximately 30 % of the observed sea-level rise over the same period. It is important to understand the relative importance of natural and anthropogenic components of this mass loss. One recent study concluded that the best estimate of the magnitude of the anthropogenic mass loss over the industrial era was only 25 % of the total, implying a predominantly natural cause. Here we show that the anthropogenic fraction of the total mass loss of a given glacier depends only on the magnitudes and rates of the natural and anthropogenic components of climate change and on the glacier's response time. We consider climate change over the past millennium using synthetic scenarios, palaeoclimate reconstructions, numerical climate simulations, and instrumental observations. We use these climate histories to drive a glacier model that can represent a wide range of glacier response times, and we evaluate the magnitude of the anthropogenic mass loss relative to the observed mass loss. The slow cooling over the preceding millennium followed by the rapid anthropogenic warming of the industrial era means that, over the full range of response times for small ice caps and glaciers, the central estimate of the magnitude of the anthropogenic mass loss is essentially 100 % of the observed mass loss. The anthropogenic magnitude may exceed 100 % in the event that, without anthropogenic climate forcing, glaciers would otherwise have been gaining mass. Our results bring assessments of the attribution of glacier mass loss into alignment with assessments of others aspects of climate change, such as global-mean temperature. Furthermore, these results reinforce the scientific and public understanding of centennial-scale glacier retreat as an unambiguous consequence of human activity.

Chemistry of soluble ions in atmospheric bulk precipitation during the monsoon over the Brahmaputra Valley

This study presents spatial variations of soluble ion chemistry in the bulk precipitation over the Brahmaputra Valley covering a large city (Guwahati) and remote rural locations (Tezpur and Dhemaji) during the monsoon period of 2015. The chemical characterization of the inorganic ions (F−, Cl−, Ca2+, Mg2+, Na+, K+) along with secondary ions (NO3−, SO42−, and NH4+) of bulk samples was done. Concentrations of NO3−, SO42−, K+, Ca2+, and Mg2+ showed significant variations in all the three sites at p < 0.05 significant level. Calcium ion (Ca2+) and SO42− showed maximum concentrations in the bulk precipitation samples irrespective of different sampling backgrounds. Precipitation at Dhemaji showed the lesser total ionic composition (60.2 μeq/L), compared to Guwahati (178.4 μeq/L) and Tezpur (87.5 μeq/L). Calculation of %SSF (sea salt fraction), %CF (crustal fraction), and %AF (anthropogenic fraction) revealed NO3− and SO42− being mostly contributed by the anthropogenic sources in samples of all the locations. Principal component analysis revealed the influence of crustal, biomass burning, marine and other anthropogenic sources such as emissions from agricultural fields, cattle farming, wasteland, waste burning, and biogenic emissions as the main contributors to the bulk precipitation chemistry over the Brahmaputra Valley. A significant positive correlation between PM2.5 and anthropogenic components such as NO3−, SO42−, and NH4+ of bulk precipitation was observed. This indicates a prominent aerosol precipitation coupling, which helps in the scavenging of air pollutants over the study region.

Regional and global contributions of air pollution to risk of death from COVID-19.

AimsThe risk of mortality from the coronavirus disease that emerged in 2019 (COVID-19) is increased by comorbidity from cardiovascular and pulmonary diseases. Air pollution also causes excess mortality from these conditions. Analysis of the first severe acute respiratory syndrome coronavirus (SARS-CoV-1) outcomes in 2003, and preliminary investigations of those for SARS-CoV-2 since 2019, provide evidence that the incidence and severity are related to ambient air pollution. We estimated the fraction of COVID-19 mortality that is attributable to the long-term exposure to ambient fine particulate air pollution.Methods and resultsWe characterized global exposure to fine particulates based on satellite data, and calculated the anthropogenic fraction with an atmospheric chemistry model. The degree to which air pollution influences COVID-19 mortality was derived from epidemiological data in the USA and China. We estimate that particulate air pollution contributed ∼15% (95% confidence interval 7–33%) to COVID-19 mortality worldwide, 27% (13 – 46%) in East Asia, 19% (8–41%) in Europe, and 17% (6–39%) in North America. Globally, ∼50–60% of the attributable, anthropogenic fraction is related to fossil fuel use, up to 70–80% in Europe, West Asia, and North America.ConclusionOur results suggest that air pollution is an important cofactor increasing the risk of mortality from COVID-19. This provides extra motivation for combining ambitious policies to reduce air pollution with measures to control the transmission of COVID-19.

Constraining Uncertainty in Aerosol Direct Forcing

AbstractThe uncertainty in present‐day anthropogenic forcing is dominated by uncertainty in the strength of the contribution from aerosol. Much of the uncertainty in the direct aerosol forcing can be attributed to uncertainty in the anthropogenic fraction of aerosol in the present‐day atmosphere, due to a lack of historical observations. Here, we present a robust relationship between total present‐day aerosol optical depth and the anthropogenic contribution across three multimodel ensembles and a large single‐model perturbed parameter ensemble. Using observations of aerosol optical depth, we determine a reduced likely range of the anthropogenic component and hence a reduced uncertainty in the direct forcing of aerosol.

A new perspective of probing the level of pollution in the megacity Delhi affected by crop residue burning using the triple oxygen isotope technique in atmospheric CO2

Air quality in the megacity Delhi is affected not only by local emissions but also by pollutants from crop residue burning in the surrounding areas of the city, particularly the rice straw burning in the post monsoon season. As a major burning product, gaseous CO2, which is rather inert in the polluted atmosphere, provides an alternative solution to characterize the impact of biomass burning from a new perspective that other common tracers such as particulate matters are limited because of their physical and chemical reactiveness. Here, we report conventional ([CO2], δ13C, and δ18O) and unconventional (Δ17O) isotope data for CO2 collected at Connaught Place (CP), a core area in the megacity Delhi, and two surrounding remote regions during a field campaign in October 18–20, 2017. We also measured the isotopic ratios near a rice straw burning site in Taiwan to constrain their end member isotopic compositions. Rice straw burning produces CO2 with δ13C, δ18O, and Δ17O values of −29.02 ± 0.65, 19.63 ± 1.16, and 0.05 ± 0.02‰, respectively. The first two isotopic tracers are less distinguishable from those emitted by fossil fuel combustion but the last one is significantly different. We then utilize these end member isotopic ratios, with emphasis on Δ17O for the reason given above, for partitioning sources that affect the CO2 level in Delhi. Anthropogenic fraction of CO2 at CP ranges from 4 to 40%. Further analysis done by employing a three-component (background, rice straw burning, and fuel combustion) mixing model with constraints from the Δ17O values yields that rice straw burning contributes as much as ∼70% of the total anthropogenic CO2, which is more than double of the fossil fuel contribution (∼30%), during the study days.

Measurement of mercury, other trace elements and major ions in wet deposition at Jomsom: The semi-arid mountain valley of the Central Himalaya

Abstract South Asian pollutants can be transported and deposited via wet/dry deposition to the remote areas of the Himalayas and could pose a serious threat to the mountain ecosystems. Therefore, in order to understand the concentrations, fluxes, seasonal variation and origin of the mercury (Hg), major ions and trace elements, precipitation samples were collected during 2012–2013 from a data gap region, Jomsom, the high elevation semi-arid mountain valley in the central Himalayas. The volume-weighted mean (VWM) concentrations of ions followed the order of Ca2+ > Mg2+ > Na+ > NH4+ > SO42− > Cl− > NO3− > K+. The concentration of Cd was lowest (0.07 μg L−1) whereas that of Fe was the highest (1073.59 μg L−1) in the precipitation samples. Wet deposition level of all the measured inorganic species was comparable to urban Lhasa but higher than those in remote alpine sites of the Tibetan Plateau (TP). This study shows that Hg and other inorganic constituents were higher in the non-monsoon season compared to monsoon due to enhanced washout of aerosols. Enrichment factor (EF), sea salt fraction, crustal and anthropogenic fractions, principal component analysis (PCA) and correlation coefficient analysis suggested that crustal dust and anthropogenic activities as the major sources of measured chemical species whereas the influence of sea-salt was minimal. In addition, local anthropogenic emissions were low suggesting that the majority of the pollutants could have been transported from the South Asian region to the high elevation mountains. Meanwhile, low precipitation and dry environment could have enhanced the concentrations of inorganic species in the arid region than other sites over the central Himalayas. This work adds new dataset of inorganic pollutants in wet precipitation and provides baseline information for an arid region environmental protection. However, there is a need for further long-term monitoring to understand the precipitation chemistry of the arid regions.

Impact of anthropogenic sulfate deposition via precipitation on carbonate weathering in a typical industrial city in a karst basin of southwest China: A case study in Liuzhou

An analysis was performed of the hydrochemical characteristics of precipitation and river water samples collected from the Liujiang River Basin from June 2014 to May 2015, SW China to determine the carbon source and sink of carbonate weathering by anthropogenic sulfate deposition via precipitation in a typical Karst industrial city. Our findings revealed that (1) the pH of the precipitation samples has a volume-weighted mean (VWM) of 5.78 and that the acid rain rate is 12%. The enrichment factor (EF), sea salt fraction (SSF), crustal fraction (CF) and anthropogenic fraction (AF) were calculated, and the results indicated that precipitation was characterized by high concentrations of SO4, NH4, Ca and NO3. Na and Cl, Ca and NH4, and SO4 (98.2%) and NO3 (99.8%) were mainly derived from sea salt, earth crust, and anthropogenic activities, respectively. Combined with the air mass trajectory (HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory)) and the concentration of non-sea salt (NSS) SO4 and δ34S–SO4nss, the δ34S–SO4sam ranged from −2.6–12.6‰ and atmospheric sulfate was mainly associated with local coal combustion, fossil fuels and the transmission distance of pollution sources from the northwest and southwest in the interior of the continents. (2) An analysis of the river hydrochemical characteristics showed that the cations are mainly Ca and Mg, and they accounted for approximately 90% of the total cations. The anions were mainly HCO3 and SO4, and the hydrochemical composition of the river was mainly controlled by the weathering of carbonate minerals in the river basin. An analysis of the correlation between the changes in the chemical equivalence concentration of [Ca + Mg]/[HCO3+SO4] showed that the ratio of most river water samples was approximately 1, indicating that Ca and Mg in the river need HCO3 and SO4 for chemical equilibrium and that SO4 in the river may be involved in the dissolution of carbonate minerals. (3) Corrections were performed based on the chloride-normalized ratios and the contribution of each terminal element was calculated to estimate the major ions of precipitation input; the results showed that the average contribution ratio of SO4 transported to the river by anthropogenic sulfuric acid in precipitation reached 85.57%. (4) According to the proportional relationships, carbonate weathering accounts for 31.73% of the anthropogenic sulfuric acid via precipitation and would cause an approximate 6.27% increase in carbonate weathering rates but a 19.48% decrease in CO2 consumption rates. Taken together, our results revealed that even in high-carbonate areas of Southwest China, chemical weathering by sulfuric acid can reduce the carbon sink effect caused by carbonate weathering.

Anthropogenic gadolinium in tap water and in tap water-based beverages from fast-food franchises in six major cities in Germany

Gadolinium-based contrast agents used in magnetic resonance imaging are difficult to impossible to remove in wastewater treatment plants, and may enter groundwater production wells and hence municipal tap water via bank filtration. As anthropogenic gadolinium (Gd) may be accompanied by other, more harmful waste water-derived (micro)pollutants such as endocrine disruptors, we investigated the potential pathway of anthropogenic Gd into popular tap water-based beverages sold in highly frequented fast food restaurants. We, therefore, determined the concentration and distribution of geogenic and anthropogenic rare earth elements (REE) in tap water and in a related tap water-based popular soft drink (Coca Cola) from two fast food franchises (McDonalds and Burger King) in six major German cities. We observed anthropogenic Gd in both tap water and corresponding soft drinks in all investigated cities, extending the database for anthropogenic Gd in tap waters and highlighting its widespread distribution. In Berlin and Düsseldorf, where tap water is (mainly) produced by river bank filtration, 85 to 99% of the total Gd is of anthropogenic origin. The surprisingly high anthropogenic fraction (91%) in tap water from Munich reveals that even the shallow groundwater tapped in two Alpine valleys is eventually exposed to anthropogenic pollution. The REE distribution in post-mix soft drinks generally follows that of the corresponding tap water, except for enrichments of ytterbium (Yb), lutetium (Lu) and cerium (Ce), which are derived from the syrup. The concentration of anthropogenic Gd is similar in the soft drinks and in the corresponding tap water, demonstrating that the highly stable Gd-based contrast agents are not removed in soda fountains but are directly transferred to the beverages. This study highlights a pathway for anthropogenic waste water-derived xenobiotics such as pharmaceuticals and endocrine disruptors into the food chain, and hence, reveals the potential for human exposure to potentially harmful anthropogenic compounds.

The Relationship between Air-Mass Trajectories and the Abundance of Dust-Borne Prokaryotes at the SE Mediterranean Sea

Airborne prokaryotes are transported along with dust/aerosols, yet very little attention is given to their temporal variability above the oceans and the factors that govern their abundance. We analyzed the abundance of autotrophic (cyanobacteria) and heterotopic airborne microbes in 34 sampling events between 2015–2018 at a coastal site in the SE Mediterranean Sea. We show that airborne autotrophic (0.2–7.6 cells × 103 m−3) and heterotrophic (0.2–30.6 cells × 103 m−3) abundances were affected by the origin and air mass trajectory, and the concentration of dust/aerosols in the air, while seasonality was not coherent. The averaged ratio between heterotrophic and autotrophic prokaryotes in marine-dominated trajectories was ~1.7 ± 0.6, significantly lower than for terrestrial routes (6.8 ± 6.1). Airborne prokaryotic abundances were linearly and positively correlated to the concentrations of total aerosol, while negatively correlated with the aerosol’s anthropogenic fraction (using Pb/Al or Cu/Al ratios as proxies). While aerosols may play a major role in dispersing terrestrial and marine airborne microbes in the SE Mediterranean Sea, the mechanisms involved in the dispersal and diversity of airborne microorganisms remain to be studied and should include standardization in collection and analysis protocols.

The MACv2 aerosol climatology

The MAC aerosol climatology defines monthly global maps for aerosol properties. The definition of mid-visible optical and microphysical properties is strongly linked to multi-year statistics of observations by sun-photometers of the AERONET and MAN ground networks. As available statistics are spatially sparse, context from bottom-up global modelling is added. Now in its second version, oceanic MAN reference data are included, a different lower anthropogenic fraction is assumed and the merging of the data-statistics is improved. Hereby, now only absolute properties are merged and trusted photometer data are given stronger weights via regional corrections in place of local domain limited corrections. Global average mid-visible (550 mn) aerosol properties are 0.12 for the aerosol optical depth (AOD), 0.94 for the single scattering albedo (SSA) and 0.7 for the asymmetry-factor (ASY). Averages for sub-micrometer (fine-mode) and super-micrometer (coarse-mode) aerosol sizes are 0.063 (AODf) and 0.058 (AODc), 0.92 (SSAf) and 0.965 (SSAc) and 0.64 (ASYf) and 0.77 (ASYc), respectively. A new element is the separation of aerosol absorption (AAOD) by sky-/sun-photometers into fine-mode and coarse-mode contributions. These properties as well as the fine-mode effective radii were merged with background data from global modelling yielding global averages of 0.0051 (AAODf), 0.0021 (AAODc) and 0.18 μm (RE,f). Local monthly mode detail now allows (in a ‘top-down’ approach) to extract global distributions for aerosol component amounts and sizes. As the considered components for soot (BC), organics (OC), non-absorbing fine-mode (SU), sea-salt (SS) and mineral dust (DU) have pre-defined spectrally resolved properties, optical properties at other than mid-visible wavelengths are automatically defined – as required in broadband radiative transfer applications. With component information (e.g. amount, composition and size) also MAC estimates for CCN and IN concentrations are possible and also a simple MAC based aerosol retrieval model for satellite sensor data is suggested.