Time series of air chemistry measurements at Georg-von-Neumayer station, Dronning Maud Land, Antarctica in the years 1982 to 1991

The first Air Chemistry Observatory at the German Antarctic station Georg von Neumayer (GvN) was operated for 10 years from 1982 to 1991. The focus of the established observational programme was on characterizing the physical properties and chemical composition of the aerosol, as well as on monitoring the changing trace gas composition of the background atmosphere, especially concerning greenhouse gases. The observatory was designed by the Institut für Umweltphysik, University of Heidelberg (UHEIIUP). The experiments were installed inside the bivouac lodge, mounted on a sledge and put upon a snow hill to prevent snow accumulation during blizzards. All experiments were under daily control and daily performance protocols were documented. A ventilated stainless steel inlet stack (total height about 3-4 m above the snow surface) with a 50% aerodynamic cut-off diameter around 7-10 µm at wind velocities between 4-10 m/s supplied all experiments with ambient air. Contamination free sampling was realized by several means: (i) The Air Chemistry Observatory was situated in a clean air area about 1500 m south of GvN. Due to the fact that northern wind directions are very rare, contamination from the base can be excluded for most of the time. (ii) The power supply (20 kW) is provided by a cable from the main station, thus no fuel-driven generator is operated in the very vicinity. (iii) Contamination-free sampling is controlled by the permanently recorded wind velocity, wind direction and by condensation particle concentration. Contamination was indicated if one of the following criteria were given: Wind direction within a 330°-30° sector, wind velocity <2.2 m/s or >17.5 m/s, or condensation particle concentrations >2500/cm**3 during summer, >800/cm**3 during spring/autumn and >400/cm**3 during winter. If one or a definable combination of these criteria were given, high volume aerosol sampling and part of the trace gas sampling were interrupted. Starting at 1982 through 1991-01-14 surface ozone was measured with an electrochemical concentration cell (ECC). Surface ozone mixing ratio are given in ppbv = parts per 10**9 by volume. The averaging time corresponds to the given time intervals in the data sheet. The accuracy of the values are better than ±1 ppbv and the detection limit is around 1.0 ppbv. Aerosols were sampled on two Whatman 541 cellulose filters in series and analyzed by ion chromatography at the UHEI-IUP. Generally, the sampling period was seven days but could be up to two weeks on occasion. The air flow was around 100 m**3/h and typically 10000-20000 m**3 of ambient air was forced through the filters for one sample. Concentration values are given in nanogram (ng) per 1 m**3 air at standard pressure and temperature (1013 mbar, 273.16 K). Uncertainties of the values were approximately ±10% to ±15% for the main components MSA, chloride, nitrate, sulfate and sodium, and between ±20% and ±30% for the minor species bromide, ammonium, potassium, magnesium and calcium.

PM2.5, PM10, and PM10-associated elements in the air in Bamako, Mali (2012-2013)

Saharan dust incursions and particulates emitted from human activities degrade air quality throughout West Africa, especially in the rapidly expanding urban centers in the region. Particulate matter (PM) that can be inhaled is strongly associated with increased incidence of and mortality from cardiovascular and respiratory diseases and cancer. Air samples collected in the capital of a Saharan-Sahelian country (Bamako, Mali) between September 2012 - July 2013 were found to contain inhalable PM concentrations that exceeded World Health Organization (WHO) and US Environmental Protection Agency (USEPA) PM2.5 and PM10 24-h limits 58 - 98% of days and European Union (EU) PM10 24-h limit 98% of days. Mean concentrations were 1.2-to-4.5 fold greater than existing limits. Inhalable PM was enriched in transition metals, known to produce reactive oxygen species and initiate the inflammatory reaction, and other potentially bioactive and biotoxic metals/metalloids. Eroded mineral dust composed the bulk of inhalable PM, whereas most enriched metals/metalloids were likely emitted from oil combustion, biomass burning, refuse incineration, vehicle traffic, and mining activities. Human exposure to inhalable PM and associated metals/metalloids over 24-h was estimated. The findings indicate that inhalable PM in the Sahara-Sahel region may present a threat to human health, especially in urban areas with greater inhalable PM and transition metal exposure.

Continuously measured 222Rn activity concentrations (daily means) in near surface air at Neumayer Station in the period 1995 through 2011

We report on continuously measured 222Rn activity concentrations in near-surface air at Neumayer Station in the period 1995-2011. This 17-year record showed no long-term trend and has overall mean ± standard deviation of (0.019 ± 0.012) Bq/m**3. A distinct and persistent seasonality could be distinguished with maximum values of (0.028 ± 0.013) Bq/m**3 from January to March and minimum values of (0.015 ± 0.009) Bq/m**3 from May to October. Elevated 222Rn activity concentrations were typically associated with air mass transport from the Antarctic Plateau. Our results do not support a relation between enhanced 222Rn activity concentrations at Neumayer and cyclonic activity or long-range transport from South America. The impact of oceanic 222Rn emissions could not be properly assessed but we tentatively identified regional sea ice extent (SIE) variability as a significant driver of the annual 222Rn cycle.

Continuous 25-years aerosol records at coastal Antarctica: Part I. Variability and climate implications of ionic compounds

The aerosol climatology at the coastal Antarctic Neumayer Station (NM) was investigated based on continuous, 25-yr long observations of biogenic sulphur components (methanesulfonate and non-sea salt sulphate), sea salt and nitrate. Although significant long-term trends could only be detected for nitrate (-3.6 ± 2.5% per year between 1983 and 1993 and +4.0 ± 3.2% per year from 1993-2007), non-harmonic periodicities between 2 and 5 yr were typical for all species. Dedicated time series analyses revealed that relations to sea ice extent and various circulation indices are weak at best or not significant. In particular, no consistent link between sea ice extent and sea salt loadings was evident suggesting only a rather local relevance of the NM sea salt record. Nevertheless, a higher Southern Annular Mode index tended to entail a lower biogenic sulphur signal. In examining the spatial uniformity of the NM findings we contrasted them to respective 17 yr records from the coastal Dumont d'Urville Station. We found similar long-term trends for nitrate, indicating an Antarctic-wide but not identifiable atmospheric signal, although any significant impact of solar activity or pollution could be ruled out. No inter-site variability on the multiannual scale was evident for the other ionic compounds.

Continuous condensation particle (CP) observations from 1984 through 2009 at Neumayer Station, Antacrtica

Continuous condensation particle (CP) observations were conducted from 1984 through 2009 at Neumayer Station under stringent contamination control. During this period, the CP concentration (median 258 1/cm**3) showed no significant long term trend but exhibited a pronounced seasonality characterized by a stepwise increase starting in September and reaching its annual maximum of around 10**3/cm**3 in March. Minimum values below 10**2/cm**3 were observed during June/July. Dedicated time series analyses in the time and frequency domain revealed no significant correlations between inter-annual CP concentration variations and atmospheric circulation indices like Southern Annular Mode (SAM) or Southern Ocean Index (SOI). The impact of the Pinatubo volcanic eruption and strong El Niño events did not affect CP concentrations. From thermodenuder experiments we deduced that the portion of volatile (at 125 °C) and semi-volatile (at 250 °C) particles which could be both associated with biogenic sulfur aerosol, was maximum during austral summer, while during winter non-volatile sea salt particles dominated. During September through April we could frequently observe enhanced concentrations of ultrafine particles within the nucleation mode (between 3 nm and 7 nm particle diameter), preferentially in the afternoon.

Time series of black carbon aerosol measurements from Neumayer Station, 1999-2011

Continuous black carbon (BC) observations were conducted from 1999 through 2009 by an Aethalometer (AE10) and from 2006 through 2011 by a Multi-Angle Absorption Photometer (MAAP) at Neumayer Station (NM) under stringent contamination control. Considering the respective observation period, BC concentrations measured by the MAAP were somewhat higher (median ± standard deviation: 2.1 ± 2.0 ng/m**3) compared to the AE10 results (1.6 ± 2.1 ng/m**3). Neither for the AE10 nor for the MAAP data set a significant long-term trend could be detected. Consistently a pronounced seasonality was observed with both instruments showing a primary annual maximum between October and November and a minimum in April with a maximum/minimum ratio of 4.5/1.6 = 3.8 and 2.7/0.64 = 4.2 for the MAAP and AE10 data, respectively. Occasionally a secondary summer maximum in January/February was visible. With the aim to assess the impact of BC on optical properties of the aerosol at NM, we evaluated the BC data along with particle scattering coefficients measured by an integrating nephelometer. We found the mean single scattering albedo of w550 = 0.992 ± 0.0090 (median: 0.994) at a wavelength of 550 nm with a range of values from 0.95 to 1.0.