Precipitation chemistry over the Indian region

The present study is based on the precipitation chemistry data from the Background Air Pollution Monitoring Network (BAPMoN) in the Indian region, for the period 1976-87. Sampling is made on an event basis and the pH and electrical conductivity of the samples are determined from filtered samples immediately after cessation of rain. The chemical analysis is performed on monthly mixed samples. No trend is found in the pH of rainwater from background areas except at Allahabad, Pune and Visakhapatnam which suffer from sizable anthropogenic influences. The pH seems to be related more to NO3 ions compared to SO4-2 ions. A natural buffer appearing in the form of alkaline soil-derived species seems adequateat most places (except Mohanbari), in keeping a check on progressive acidification despite steady increase in concentration of nitrates. The ion balance cannot be achieved without including the presence of HCO3, which when done explains the observed electrical conductivity of rainwater. The interaction of marine aerosols with acid aerosols has also been studied for the marine regions in the Indian areas and reveals a substantial removal of chloride from sea-salt. Inland sources of NaCl have also been identified from the BAPMoN data.

Ecophysiological response of Eucalyptus camaldulensis to dust and lead pollution

Background: Air and soil pollution are among the main concerns in urban areas worldwide, and dust and heavy metals are major contributors to environmental pollution. Lead (Pb) is a highly toxic heavy metal that badly affects human health as well as plant's survival and growth. Vegetation can play an important role in ameliorating the effects of these pollutants. Eucalyptus camaldulensis is well adapted and cultivated throughout a wide range of urban environments from temperate to tropical climates. Methods: A 90 days experiment was conducted to investigate the effects of lead (Pb) and dust pollution on the growth performance of young E. camaldulensis plants. Four months old seedlings were treated with a factorial combinations of Pb (0,10 and 20 mg/l applied in irrigation) and dust levels (0,5 and 10 g applied on foliage). Results: All morphological traits (root length, shoot length, stem diameter) and biomass (root and shoot, fresh and dry mass) of E. camaldulensis were significantly reduced when exposed to higher Pb and dust levels. The highest Pb treatments exhibited greater Pb accumulation in plant roots (23.54 ± 1.61 mg/kg), shoots (15.53 ± 1.98 mg/kg), and leaves (13.89 ± 1.49 mg/kg). Dust load on leaves was greater (72.78 ± 8.1 mg/cm2) for those treatments with higher dust and Pb additions compared to the control (16.11 ± 2.0 mg/cm2). Chlorophyll content was greater at the start of the experiment (68.78 ± 0.74 mg.g-1FW) and progressively decreased over time consistently with the increase of Pb and dust levels applied. Conclusions: The results of the experiment, suggest that E. camaldulensis could be successfully grown in minimum to moderate Pb and dust polluted urban environments.

Volatile Organic Compounds in the Azteca/Cecropia Ant-Plant Symbiosis and the Role of Black Fungi

Black fungi of the order Chaetothyriales are grown by many tropical plant-mutualistic ants as small so-called “patches” in their nests, which are located inside hollow structures provided by the host plant (“domatia”). These fungi are introduced and fostered by the ants, indicating that they are important for the colony. As several species of Chaetothyriales tolerate, adsorb, and metabolize toxic volatiles, we investigated the composition of volatile organic compounds (VOCs) of selected domatia in the Azteca/Cecropia ant-plant mutualism. Concentrations of VOCs in ant-inhabited domatia, empty domatia, and background air were compared. In total, 211 compounds belonging to 19 chemical families were identified. Ant-inhabited domatia were dominated by ketones with 2-heptanone, a well-known ant alarm semiochemical, as the most abundant volatile. Empty domatia were characterized by relatively high concentrations of the monoterpenes d-limonene, p-cymene and β-phellandrene, as well as the heterocyclic sulphur-containing compound, benzothiazole. These compounds have biocidal properties and are primarily biosynthesized by plants as a defense mechanism. Interestingly, most of the latter compounds were present at lower concentrations in ant inhabited domatia than in non-colonized ones. We suggest that Chaetothyriales may play a role in reducing the VOCs, underlining that the mutualistic nature of these fungi as VOCs accumulation might be detrimental for the ants, especially the larvae.

What do we know about the global methane budget? Results from four decades of atmospheric CH 4 observations and the way forward

Atmospheric CH 4 is arguably the most interesting of the anthropogenically influenced, long-lived greenhouse gases. It has a diverse suite of sources, each presenting its own challenges in quantifying emissions, and while its main sink, atmospheric oxidation initiated by reaction with hydroxyl radical (OH), is well-known, determining the magnitude and trend in this and other smaller sinks remains challenging. Here, we provide an overview of the state of knowledge of the dynamic atmospheric CH 4 budget of sources and sinks determined from measurements of CH 4 and δ 13 C CH4 in air samples collected predominantly at background air sampling sites. While nearly four decades of direct measurements provide a strong foundation of understanding, large uncertainties in some aspects of the global CH 4 budget still remain. More complete understanding of the global CH 4 budget requires significantly more observations, not just of CH 4 itself, but other parameters to better constrain key, but still uncertain, processes like wetlands and sinks. This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 1)'.

Indoor and Outdoor Nanoparticle Concentrations in an Urban Background Area in Northern Sweden: The NanoOffice Study

In recent years, nanoparticles (NPs) have received much attention due to their very small size, high penetration capacity, and high toxicity. In urban environments, combustion-formed nanoparticles (CFNPs) dominate in particle number concentrations (PNCs), and exposure to those particles constitutes a risk to human health. Even though fine particles (<2.5 µm) are regularly monitored, information on NP concentrations, both indoors and outdoors, is still limited. In the NanoOffice study, concentrations of nanoparticles (10–300 nm) were measured both indoors and outdoors with a 5-min time resolution at twelve office buildings in Umeå. Measurements were taken during a one-week period in the heating season and a one-week period in the non-heating season. The measuring equipment SMPS 3938 was used for indoor measurements, and DISCmini was used for outdoor measurements. The NP concentrations were highest in offices close to a bus terminal and lowest in offices near a park. In addition, a temporal effect appeared, usually with higher concentrations of nanoparticles found during daytime in the urban background area, whereas considerably lower nanoparticle concentrations were often present during nighttime. Infiltration of nanoparticles from the outdoor air into the indoor air was also common. However, the indoor/outdoor ratios (I/O ratios) of NPs showed large variations between buildings, seasons, and time periods, with I/O ratios in the range of 0.06 to 0.59. The reasons for high indoor infiltration rates could be NP emissions from adjacent outdoor sources. We could also see particle growth since the indoor NPs were, on average, almost twice as large as the NPs measured outdoors. Despite relatively low concentrations of NPs in the urban background air during nighttime, they could rise to very high daytime concentrations due to local sources, and those particles also infiltrated the indoor air.

Historical reconstruction of background air pollution over France for 2000–2015

This paper describes a 16-year datasets of air pollution concentrations and air quality indicators over France. Using a kriging method that combines background measurements of air quality and modeling with the Chemistry Transport Model CHIMERE, hourly concentrations of NO2, O3, PM10 and PM2.5 are produced with a spatial resolution about 4 kilometers. Regulatory indicators (annual average, SOMO35, AOT40 etc…) are also calculated from these hourly data. NO2 and O3 datasets cover the period 2000–2015, as well as PM10 annual data. PM10 hourly concentrations are not available from 2000 to 2007 due to known artefact in PM10 measurements. PM2.5 data are only available from 2009 because of the lack of measurement stations before. The overall dataset has been evaluated over all the years through a cross-validation process against background measurement stations (rural, sub-urban and urban), to account for the data fusion between measurement and models in the method. Results are very good for PM10, PM2.5 and O3. It shows an overestimation of NO2 concentrations in rural area, while background NO2 values in urban areas are well represented. Maps of the main indicators are shown over years and trends are calculated. Finally, country exposure and trends of three main health related indicators: yearly averaged PM2.5 NO2 and SOMO35 are calculated. The DOI link for the dataset is http://doi.org/10.5281/zenodo.5043645 (Real et al., 2021). We hopethat the publication of this dataset in open access will facilitate further studies on the impacts of air pollution.

Temporal variations in air pollution at two roundabouts in the city of Cotonou, Benin

Background: Air pollution has caused health and environmental problems around the world. In this study we analysed the temporal evolution of air pollution in Cotonou regarding the standards of Benin and of World Health Organization (WHO). Methods: Solar-powered electrochemical sensors (CO: carbon monoxide, SO2: sulphur dioxide, and O3/NO2: ozone/nitrogen dioxide) and photoionization detectors (for NMVOC: nonmethane volatile organic compounds) were permanently installed and monitored from June 2019 to March 2020 at Akpakpa PK3 (A) and Vèdokô Cica-Toyota (B) roundabouts.Results: CO and SO2 concentrations at both roundabouts were significantly higher on weekends than on weekdays. The concentrations of NMVOC and O3 / NO2 on Sunday differed considerably from the other days of the week at A and B, respectively. There was a positive linear correlation between the concentrations of CO and SO2, O3 / NO2 and SO2, and CO O3 / NO2 to B, and only between CO and O3 / NO2, in A.At the two sites, the average of SO2 concentrations (in μg/m3) were higher than the WHO standard (500) for an exposure of 10 minutes (2258 A and 2143 B) and the Benin standard (1300) for 1 hour exposure (2181 in A and 2092 in B).Conclusion: Air pollution varies in hours and days in Cotonou. Standards are respected, except for SO2. Particular attention should be paid to the concentrations and the possible sources of gas. More sophisticated monitoring system should be put in place.

Education Differences in the Adverse Impact of PM2.5 on Incident Cognitive Impairment Among U.S. Older Adults

Background: Air pollution is linked to worse cognitive function in older adults, but whether differences in this relationship exist by education, a key risk factor for cognitive decline, remains unknown. Objective: To determine if the association between fine particulate matter air pollution (PM2.5) and incident cognitive impairment varies by level of education in two cohorts assessed a decade apart. Methods: We used data on adults ages 60 and older from the nationally representative Health and Retirement Study (HRS) linked with tract-level annual average PM2.5. We used mixed-effects logistic regression models to examine education differences in the association between PM2.5 and incident cognitive impairment in two cohorts: 2004 (n = 9,970) and 2014 (n = 9,185). Cognitive impairment was determined with tests of memory and processing speed for self-respondents and proxy and interviewer assessments of cognitive functioning in non-self-respondents. Results: PM2.5 was unrelated to incident cognitive impairment among those with 13 or more years of education, but the probability of impairment increased with greater concentrations of PM2.5 among those with 8 or fewer years of education. The interaction between education and PM2.5 was only found in 2004, possibly because PM2.5 concentrations were much lower in 2014. Conclusion: Education is a key determinant of cognitive decline and impairment, and in higher pollution contexts may serve as a protective factor against the harms of air pollution on the aging brain. Additionally, because air pollution is ubiquitous, and particularly harmful to vulnerable populations, even small improvements in air quality may have large impacts on population health.

Organic and inorganic bromine measurements around the extratropical tropopause and lowermost stratosphere (Ex-LMS): Insights into transport pathways and total bromine

&lt;p&gt;We report on measurements of total bromine (Br&lt;sup&gt;tot&lt;/sup&gt;) in the upper troposphere and lower stratosphere (UTLS) taken from the German High Altitude and LOng range research aircraft (HALO) over the North Atlantic, Norwegian Sea and north-western Europe in September/ October 2017 during the WISE (Wave-driven ISentropic Exchange) research campaign. Br&lt;sup&gt;tot&lt;/sup&gt; is calculated from measured total organic bromine (Br&lt;sup&gt;org&lt;/sup&gt;) (i.e., the sum of bromine contained in CH&lt;sub&gt;3&lt;/sub&gt;Br, the halons and the major very short-lived brominated substances) added to inorganic bromine (Br&lt;sub&gt;y&lt;/sub&gt;&lt;sup&gt;inorg&lt;/sup&gt;), evaluated from measured BrO and photochemical modelling. Combining these data, the weighted mean [Br&lt;sup&gt;tot&lt;/sup&gt;] is 19.2 &amp;#177; 1.2 ppt in the extratropical lower stratosphere (Ex-LS) of the northern hemisphere. The inferred average Br&lt;sup&gt;tot&lt;/sup&gt; for the Ex-LS is slightly smaller than expected for the middle stratosphere in 2016 (~19.6 ppt (ranging from 19-20 ppt) as reported by the WMO/UNEP Assessment (2018)). However, it reflects the expected variability in Br&lt;sup&gt;tot&lt;/sup&gt; in the Ex-LS due to influxes of shorter lived brominated source and product gases from different regions of entry. A closer look into Br&lt;sup&gt;org&lt;/sup&gt; and Br&lt;sub&gt;y&lt;/sub&gt;&lt;sup&gt;inorg&lt;/sup&gt; as well as simultaneously measured transport tracers (CO, N&lt;sub&gt;2&lt;/sub&gt;O, ...) and an air mass lag-time tracer (SF&lt;sub&gt;6&lt;/sub&gt;), suggests that a filament of air with elevated Br&lt;sup&gt;tot&lt;/sup&gt; protruded into the extratropical lowermost stratosphere (Ex-LMS) from 350-385 K and between equivalent latitudes of 55-80&amp;#730;N (high bromine filament &amp;#8211; HBrF). Lagrangian transport modelling shows the multi-pathway contributions to Ex-LMS bromine. According to CLaMS air mass origin simulations, contributions to the HBrF consist of predominantly isentropic transport from the tropical troposphere (also with elevated [Br&lt;sup&gt;tot&lt;/sup&gt;] = 21.6 &amp;#177; 0.7 ppt) as well as a smaller contribution from an exchange across the extratropical tropopause which are mixed into the stratospheric background air. In contrast, the surrounding LS above and below the HBrF has less tropical tropospheric air, but instead additional stratospheric background air. Of the tropical tropospheric air in the HBrF, the majority is from the outflow of the Asian monsoon anticyclone and the adjacent tropical regions, which greatly influences concentrations of trace gases transported into the Ex-LMS in boreal summer and fall. The resulting increase of Br&lt;sup&gt;tot&lt;/sup&gt; in the Ex-LMS and its consequences for ozone is investigated through the TOMCAT/SLIMCAT model simulations. However, more extensive monitoring of total stratospheric bromine in more aged air (i.e., in the middle stratosphere) as well as globally and seasonally is required in addition to model simulations to fully understand its impact on Ex-LMS ozone and the radiative forcing of climate.&lt;/p&gt;

Impact of large wildfires on PM10 levels and human mortality in Portugal

Uncontrolled wildfires have a substantial impact on the environment, the economy and local populations. According to the European Forest Fire Information System (EFFIS), between the years 2000 and 2013 wildfires burnt about 170,000–740,000 ha of land annually on the south of Europe (Portugal, Spain, Italy, Greece and France). Although most southern European countries have been impacted by wildfires in the last decades, Portugal was the most affected, having the highest percentage of burned area comparing to its whole territory. For this reason, it deserves a closer attention. However, there is a lack of knowledge regarding the impacts of the wildfire-related pollutants on the mortality of the population. All wildfires occurring during the fire seasons (June-July-August-September) from 2001 and 2016 were identified and those with a burned area above 1000 ha were considered for the study. To assess the spatial impact of the wildfires, these were correlated with PM10 concentrations measured at nearby background air quality monitoring stations, provided by the Portuguese Environment Agency (APA). Associations between PM10 and all-cause (excluding injuries, poisoning and external causes) and cause-specific mortality (circulatory and respiratory), provided by Statistics Portugal, were studied for the affected populations, using Poisson regression models. During the studied period (2001–2016), more than 2 million ha of forest were burned in mainland Portugal and the 48 % of wildfires occurred were large fires. A significant correlation between burned area and PM10 have been found in some NUTS III (regions) on Portugal, as well as a significant correlation between burned area and mortality. North, centre and inland of Portugal are the most affected areas. The high temperatures and long episodes of drought expected on the future will increase the probabilities of extreme events and therefore, the occurrence of wildfires.