Trends and emissions of six perfluorocarbons in the Northern Hemisphere and Southern Hemisphere

Perfluorocarbons (PFCs) are potent greenhouse gases with global warming potentials up to several thousand times greater than CO2 on a 100-year time horizon. The lack of any significant sinks for PFCs means that they have long atmospheric lifetimes of the order of thousands of years. Anthropogenic production is thought to be the only source for most PFCs. Here we report an update on the global atmospheric abundances of the following PFCs, most of which have for the first time been analytically separated according to their isomers: c-octafluorobutane (c-C4F8), n-decafluorobutane (n-C4F10), n-dodecafluoropentane (n-C5F12), n-tetradecafluorohexane (n-C6F14), and n-hexadecafluoroheptane (n-C7F16). Additionally, we report the first data set on the atmospheric mixing ratios of perfluoro-2-methylpentane (i-C6F14). The existence and significance of PFC isomers have not been reported before, due to the analytical challenges of separating them. The time series spans a period from 1978 to the present. Several data sets are used to investigate temporal and spatial trends of these PFCs: time series of air samples collected at Cape Grim, Australia, from 1978 to the start of 2018; a time series of air samples collected between July 2015 and April 2017 at Tacolneston, UK; and intensive campaign-based sampling collections from Taiwan. Although the remote “background” Southern Hemispheric Cape Grim time series indicates that recent growth rates of most of these PFCs are lower than in the 1990s, we continue to see significantly increasing mixing ratios that are between 6 % and 27 % higher by the end of 2017 compared to abundances measured in 2010. Air samples from Tacolneston show a positive offset in PFC mixing ratios compared to the Southern Hemisphere baseline. The highest mixing ratios and variability are seen in air samples from Taiwan, which is therefore likely situated much closer to PFC sources, confirming predominantly Northern Hemispheric emissions for most PFCs. Even though these PFCs occur in the atmosphere at levels of parts per trillion molar or less, their total cumulative global emissions translate into 833 million metric tonnes of CO2 equivalent by the end of 2017, 23 % of which has been emitted since 2010. Almost two-thirds of the CO2 equivalent emissions within the last decade are attributable to c-C4F8, which currently also has the highest emission rates that continue to grow. Sources of all PFCs covered in this work remain poorly constrained and reported emissions in global databases do not account for the abundances found in the atmosphere

Tropospheric Ozone Assessment Report : Present-day ozone distribution and trends relevant to human health

This study quantifies the present-day global and regional distributions (2010–2014) and trends (2000–2014) for five ozone metrics relevant for short-term and long-term human exposure. These metrics, calculated by the Tropospheric Ozone Assessment Report, are: 4th highest daily maximum 8-hour ozone (4MDA8); number of days with MDA8 > 70 ppb (NDGT70), SOMO35 (annual Sum of Ozone Means Over 35 ppb) and two seasonally averaged metrics (3MMDA1; AVGMDA8). These metrics were explored at ozone monitoring sites worldwide, which were classified as urban or non-urban based on population and nighttime lights data.Present-day distributions of 4MDA8 and NDGT70, determined predominantly by peak values, are similar with highest levels in western North America, southern Europe and East Asia. For the other three metrics, distributions are similar with North–South gradients more prominent across Europe and Japan. Between 2000 and 2014, significant negative trends in 4MDA8 and NDGT70 occur at most US and some European sites. In contrast, significant positive trends are found at many sites in South Korea and Hong Kong, with mixed trends across Japan. The other three metrics have similar, negative trends for many non-urban North American and some European and Japanese sites, and positive trends across much of East Asia. Globally, metrics at many sites exhibit non-significant trends. At 59% of all sites there is a common direction and significance in the trend across all five metrics, whilst 4MDA8 and NDGT70 have a common trend at ~80% of all sites. Sensitivity analysis shows AVGMDA8 trends differ with averaging period (warm season or annual). Trends are unchanged at many sites when a 1995–2014 period is used; although fewer sites exhibit non-significant trends. Over the longer period 1970–2014, most Japanese sites exhibit positive 4MDA8/SOMO35 trends. Insufficient data exist to characterize ozone trends for the rest of Asia and other world regions

Seasonality of Formic Acid (HCOOH) in London during the ClearfLo Campaign

Following measurements in the winter of 2012, formic acid (HCOOH) and nitric acid (HNO3) were measured using a chemical ionization mass spectrometer (CIMS) during the Summer Clean Air for London (ClearfLo) campaign in London, 2012. Consequently, the seasonal dependence of formic acid sources could be better understood. A mean formic acid concentration of 1.3 ppb and a maximum of 12.7 ppb was measured which is significantly greater than that measured during the winter campaign (0.63 ppb and 6.7 ppb, respectively). Daily calibrations of formic acid during the summer campaign gave sensitivities of 1.2 ion counts s-1 parts per trillion (ppt) by volume-1 and a limit of detection of 34 ppt. During the summer campaign, there was no correlation between formic acid and anthropogenic emissions such as NOx and CO or peaks associated with the rush hour as was identified in the winter. Rather, peaks in formic acid were observed that correlated with solar irradiance. Analysis using a photochemical trajectory model has been conducted to determine the source of this formic acid. The contribution of formic acid formation through ozonolysis of alkenes is important but the secondary production from biogenic VOCs could be the most dominant source of formic acid at this measurement site during the summer

Photochemical sensitivity to emissions and local meteorology in Bogotá, Santiago, and São Paulo: An analysis of the initial COVID-19 lockdowns

This study delves into the photochemical atmospheric changes reported globally during the pandemic by analyzing the change in emissions from mobile sources and the contribution of local meteorology to ozone (O3) and particle formation in Bogotá (Colombia), Santiago (Chile), and São Paulo (Brazil). The impact of mobility reductions (50%–80%) produced by the early coronavirus-imposed lockdown was assessed through high-resolution vehicular emission inventories, surface measurements, aerosol optical depth and size, and satellite observations of tropospheric nitrogen dioxide (NO2) columns. A generalized additive model (GAM) technique was also used to separate the local meteorology and urban patterns from other drivers relevant for O3 and NO2 formation. Volatile organic compounds, nitrogen oxides (NOx), and fine particulate matter (PM2.5) decreased significantly due to motorized trip reductions. In situ nitrogen oxide median surface mixing ratios declined by 70%, 67%, and 67% in Bogotá, Santiago, and São Paulo, respectively. NO2 column medians from satellite observations decreased by 40%, 35%, and 47%, respectively, which was consistent with the changes in mobility and surface mixing ratio reductions of 34%, 25%, and 34%. However, the ambient NO2 to NOx ratio increased, denoting a shift of the O3 formation regime that led to a 51%, 36%, and 30% increase in the median O3 surface mixing ratios in the 3 respective cities. O3 showed high sensitivity to slight temperature changes during the pandemic lockdown period analyzed. However, the GAM results indicate that O3 increases were mainly caused by emission changes. The lockdown led to an increase in the median of the maximum daily 8-h average O3 of between 56% and 90% in these cities

Time series of ice nuclei concentration at Cape Verde

Cumulative ice nuclei concentration as function of temperature determined using filter samples collected at the Cape Verde Atmospheric Observatory. Samples cover the year 2009-2013. Measurements cover the temperature range 0°C to -20°C. Additional concentration measurements obtained with the SPIN CFDC from an intense campaign in Jan.-Feb. 2016 at the Cape Verde Atmospheric Observatory complement the dataset at temperatures below -24°C

Two decades of ozone standard exceedances in Santiago de Chile

A drastic decline of 2.4 ppbv decade(-1) in the ozone mixing ratio has been measured in Santiago de Chile during the 2000s. Subsequently, in the 2010s, ozone trends stabilized in downtown and showed upward trends in eastern Santiago. The number of days with an 8-h average ozone mixing ratio above 61 ppbv, deemed harmful to health according to Chilean legislation, has declined significantly both in western and central Santiago. However, in eastern Santiago, one finds a 2010-2018 decade average of 43 days per year above recommended levels. Also, at a Receptor Site located ~ 70 km downwind from Santiago, this number rose to up to 3 months per year. A common denominator for the last two decades has been a steady increase in both gasoline and diesel-powered private cars. In the 2010s, the ozone weekend effect was frequently noted, providing evidence that the ozone formation regime in Santiago is VOC-limited. Nitrogen oxides and carbon monoxide (a proxy of anthropogenic VOCs) have increased steadily since 2014 in a relatively constant CO-to-NOx ratio. Therefore, we propose that primary emissions of NOX and VOCs from motor vehicle exhaust have remained as the main driver of the photochemical air pollution in Santiago as well as explaining the weekly variation. Santiago, like other megacities in the world, faces several challenges associated with increasing urbanization as well as the effects of climate change. An increasing population, growth in private car use, and urban sprawl have contributed to maintain high levels of ozone. New threats such as increasing temperatures observed in the central valleys of Chile, along with more frequent occurrences of heat waves, whose number has doubled in the last decade, will require a different approach to manage ozone pollution during the next decade. Santiago will not meet its own goals in the upcoming years without implementing robust, scientifically sound, and cost-effective strategies designed specifically to tackle photochemical pollution

Sharing a written medical summary with patients on the post‐admission ward round: A qualitative study of clinician and patient experience

Abstract: Rationale, Aims and Objectives: Sharing aspects of the traditional medical record with patients has been successful in primary and antenatal care, but has not been investigated in the UK inpatient setting. Our aim was to evaluate the impact on patient and clinician experience of providing patients with a written lay summary of their care‐plan in the acute care setting. Method: We carried out a qualitative interview study on two acute medicine wards in an NHS University Teaching Hospital for a 4‐week period in 2019. A summary record, designed in response to suggestions from doctors and patients from a previous study, was distributed to patients on the first ward round after admission. Eligible participants included all doctors and nurses working on and all patients and their families attending the acute medical units; patients were excluded if they lacked capacity to consent or were under 18. We interviewed 20 patients, 10 relatives, 10 doctors and 7 nurses. Results: Patients felt that the summary improved their ability to remember details about their care so they could more accurately and easily update their relatives. They did not feel that the summary induced anxiety. Patient‐doctor communication was improved: patients felt empowered to ask more questions and doctors felt that it solidified their plan and encouraged them to avoid medical jargon. Most patients felt the summary included the ‘right’ amount of information. Healthcare professionals were more concerned about the risk of breaching confidentiality than patients. Doctors felt that providing summaries was time‐consuming; there were differing opinions about whether this was a worthwhile investment of time. Clinicians recognized that the traditional medical record has many roles. Conclusions: A summary record could empower patients and improve patient‐doctor communication but would require additional clinician and administrative time

Concentration and variability of ice nuclei in the subtropic, maritime boundary layer

Measurements of the concentration and variability of ice nucleating particles in the subtropical, maritime boundary layer are reported. Filter samples collected in Cape Verde over the period 2009–2013 are analyzed with a drop freezing experiment sensitive to detect the few, rare ice nuclei active at low supercooling. The data-set is augmented with continuous flow diffusion chamber (SPIN) measurements at temperatures below −24 °C from a two month field campaign at Cape Verde in 2016. The data set is used to address the questions: What are typical concentrations of ice nucleating particles active at a certain temperature, what affects their concentration, what is their composition and where are their sources? To investigate what the most common ice nuclei are and to identify the sources, bulk chemical aerosol composition obtained from the utilized filter samples is tested for correlations with ice nuclei concentration. It is shown that no significant correlation between the rare ice nuclei and the bulk aerosol chemical composition, which could serve as tracer for a specific aerosol class e.g. of maritime origin, can be made. Concentration of ice nuclei is found to increase exponentially with decreasing temperature. It indicates that several groups of particles with different ice nucleation properties (size, composition) are contributing to the ice nuclei concentration at different temperatures. The concentration of ice nuclei active at a specific temperature varies over a wide range. The frequency with which a certain ice nuclei concentration is measured within this range is found to follow a log-normal distribution. The log-normal frequency distribution can be explained by random dilution associated with turbulent, long-distance transport. To investigate the geographic origin of ice nuclei, source attribution of air masses from dispersion modeling is used to classify the data into 7 typical situations. While no source could be attributed to the ice nuclei active at temperatures higher than −12 °C, concentrations at lower temperatures tend to be elevated in air masses originating from the Saharan desert