CCN measurements at the Princess Elisabeth Antarctica research station during three austral summers

For three austral summer seasons (2013-2016, each from December to February) aerosol particles arriving at the Belgian Antarctic research station Princess Elisabeth (PE) in Dronning Maud Land in East Antarctica were characterized. This included number concentrations of total aerosol particles (N CN ) and cloud condensation nuclei (N CCN ), the particle number size distribution (PNSD), the aerosol particle hygroscopicity, and the influence of the air mass origin on N CN and N CCN . In general N CN was found to range from 40 to 6700cm -3 , with a median of 333cm -3 , while N CCN was found to cover a range between less than 10 and 1300cm-3 for supersaturations (SSs) between 0.1% and 0.7%. It is shown that the aerosol is dominated by the Aitken mode, being characterized by a significant amount of small, and therefore likely secondarily formed, aerosol particles, with 94% and 36% of the aerosol particles smaller than 90 and ≈35nm, respectively. Measurements of the basic meteorological parameters as well as the history of the air masses arriving at the measurement station indicate that the station is influenced by both marine air masses originating from the Southern Ocean and coastal areas around Antarctica (marine events - MEs) and continental air masses (continental events - CEs). CEs, which were defined as instances when the air masses spent at least 90% of the time over the Antarctic continent during the last 10 days prior to arrival at the measurements station, occurred during 61% of the time during which measurements were done. CEs came along with rather constant N CN and N CCN values, which we denote as Antarctic continental background concentrations. MEs, however, cause large fluctuations in N CN and N CCN , with low concentrations likely caused by scavenging due to precipitation and high concentrations likely originating from new particle formation (NPF) based on marine precursors. The application of HYSPLIT back trajectories in form of the potential source contribution function (PSCF) analysis indicate that the region of the Southern Ocean is a potential source of Aitken mode particles. On the basis of PNSDs, together with N CCN measured at an SS of 0.1%, median values for the critical diameter for cloud droplet activation and the aerosol particle hygroscopicity parameter ° were determined to be 110nm and 1, respectively. For particles larger than ĝ‰110nm the Southern Ocean together with parts of the Antarctic ice shelf regions were found to be potential source regions. While the former may contribute sea spray particles directly, the contribution of the latter may be due to the emission of sea salt aerosol particles, released from snow particles from surface snow layers, e.g., during periods of high wind speed, leading to drifting or blowing snow. The region of the Antarctic inland plateau, however, was not found to feature a significant source region for aerosol particles in general or page276 for cloud condensation nuclei measured at the PE station in the austral summer

The impact of boundary layer height on air pollution concentrations in London – early results from the ClearfLo project.

The ClearfLo projects aims to understand the processes generating pollutants like ozone, NOx and particulate matter and their interaction with the urban atmospheric boundary layer. ClearfLo (www.clearflo.ac.uk) is a large multi-institution NERC-funded project that is establishing integrated measurements of the meteorology, composition and particulate loading of London’s urban atmosphere, complemented by an ambitious modeling programme. The project established a new long-term measurement infrastructure in London encompassing measurement capabilities at street level and at elevated sites. These measurements were accompanied by high resolution mod- eling with the UK Met Office Unified model and WRF. This combined measuring/modelling approach enables us to identify the seasonal cycle in the meteorology and composition, together with the controlling processes. Two intensive observation periods in January/February 2012 and during the Olympics in summer 2012 measured London’s atmosphere with higher level of detail. Data from these IOPs will enable us (i) to determine the vertical structure and evolution of the urban atmosphere (ii) to determine the chemical controls on ozone production, particularly the role of biogenic emissions and (iii) to determine the processes controlling the evolution of the size,distribution and composition of particulate matter. We present results from the wintertime IOP in London focusing on a wintertime pollution episode during January 2012. We compare measured concentrations from top of BT Tower in central London with rural background measurements and determine the processes leading to the urban increment in pollutant concentrations. Therefore, we combine high-resolution simulations with the Met Office Unified Model for London and mixing layer heights derived from lidar measurements with air quality measurements in central London in order to quantify the role the boundary layer depth plays for London’s concentrations

Impacts of local human activities on the Antarctic environment

We review the scientific literature, especially from the past decade, on the impacts of human activities on the Antarctic environment. A range of impacts has been identified at a variety of spatial and temporal scales. Chemical contamination and sewage disposal on the continent have been found to be long-lived. Contemporary sewage management practices at many coastal stations are insufficient to prevent local contamination but no introduction of non-indigenous organisms through this route has yet been demonstrated. Human activities, particularly construction and transport, have led to disturbances of flora and fauna. A small number of non-indigenous plant and animal species has become established, mostly on the northern Antarctic Peninsula and southern archipelagos of the Scotia Arc. There is little indication of recovery of overexploited fish stocks, and ramifications of fishing activity oil bycatch species and the ecosystem could also be far-reaching. The Antarctic Treaty System and its instruments, in particular the Convention for the Conservation of Antarctic Marine Living Resources and the Environmental Protocol, provide a framework within which management of human activities take place. In the face of the continuing expansion of human activities in Antarctica, a more effective implementation of a wide range of measures is essential, in order to ensure comprehensive protection of the Antarctic environment, including its intrinsic, wilderness and scientific values which remains a fundamental principle of the Antarctic Treaty System. These measures include effective environmental impact assessments, long-term monitoring, mitigation measures for non-indigenous species, ecosystem-based management of living resources, and increased regulation of National Antarctic Programmes and tourism activities

The Tropospheric Ozone Assessment Report : Trends in ozone and ozone metrics relevant for human health

Ozone is an air pollutant formed in the atmosphere from precursor species (NOx, VOCs, CH4, CO) that is detrimental to human health and ecosystems. The global Tropospheric Ozone Assessment Report (TOAR) initiative was recently initiated by the International Global Atmospheric Chemistry Project (IGAC) with the mission to provide the research community with an up-to-date scientific assessment of tropospheric ozone’s global distribution and trends from the surface to the tropopause. TOAR has assembled the world’s largest database of surface ozone observations and is generating ozone exposure and dose metrics at thousands of measurement sites around the world. This talk will present results from the assessment focused on those indicators most relevant to human health. An overview of trends in ozone concentrations across the globe, with an emphasis on urban areas because of their high population density and thereby relevance for human health, will be shown. Trends in different world regions will be compared, as well as differences within regions. Additionally, there are a variety of existing metrics aimed at assessing ozone concentrations and the protection of human health in use worldwide. The message communicated can be very different depending on metric used and whether this is focused on peak ozone concentrations or longer-term average concentrations. A selection of these metrics has been made to represent different conditions and applied to the ozone data gathered in the TOAR effort. The sensitivity of the trends to the selection of metric will be discussed

Chemistry of the Antarctic boundary layer and the interface with snow: an overview of the CHABLIS campaign

CHABLIS (Chemistry of the Antarctic Boundary Layer and the Interface with Snow) was a collaborative UK research project aimed at probing the detailed chemistry of the Antarctic boundary layer and the exchange of trace gases at the snow surface. The centre-piece to CHABLIS was the measurement campaign, conducted at the British Antarctic Survey station, Halley, in coastal Antarctica, from January 2004 through to February 2005. The campaign measurements covered an extremely wide range of species allowing investigations to be carried out within the broad context of boundary layer chemistry. Here we present an overview of the CHABLIS campaign. We provide details of the measurement location and introduce the Clean Air Sector Laboratory (CASLab) where the majority of the instruments were housed. We describe the meteorological conditions experienced during the campaign and present supporting chemical data, both of which provide a context within which to view the campaign results. Finally we provide a brief summary of highlights from the measurement campaign. Unexpectedly high halogen concentrations profoundly affect the chemistry of many species at Halley throughout the sunlit months, with a secondary role played by emissions from the snowpack. This overarching role for halogens in coastal Antarctic boundary layer chemistry was completely unanticipated, and the results have led to a step-change in our thinking and understanding