Finnish Arctic Research Articles

Sulfate aerosol formation in the Arctic boundary layer

Aerosol size distributions were measured in the Finnish Arctic over a continuous period of 1‐year using diffusion battery and condensation particle counter. Numerous nucleation bursts were observed. Some of the nucleation events were associated with marine air clean of SO2, while others were associated with SO2‐pollution events originating from smelters located in the Kola Peninsula. Six nucleation events were analyzed with a combined gas phase chemistry‐aerosol dynamical model that used meteorological input data taken from calculated back trajectories. The assumed homogeneous nucleation mechanism of sulfuric acid and water explains the observed pollution‐related nucleation events well but does not explain the marine nucleation events.

Formation of particulate MSA: deductions from size distribution measurements in the Finnish Arctic

Formation of particulate MSA: deductions from size distribution measurements in the Finnish Arctic

Formation of particulate MSA: deductions from size distribution measurements in the Finnish Arctic

Formation of particulate MSA was studied by conducting a field campaign in the Finnish Arctic. Based on continuous mass size distributions extracted from impactor measurements, 4 MSA modes were identified: an accumulation mode centred between 0.3-0.5 μm of particle aerodynamic diameter, an Aitken mode below 0.1 μm, and 2 supermicron modes that peaked at 2-3 and 7-10 μm, respectively. The lower supermicron mode resulted primarily from the reaction of gaseous MSA with sea salt particles, and the upper mode probably from its reaction with soil-derived particles. From 70 to 90% of the MSA was found in the accumulation mode, where it was distributed very similarly to ammonium. The overall MSA to nss-SO42- ratio, R, ranged from 2 to 34%, with most of this variation resulting from different degrees of anthropogenic perturbation in the measured air masses. When comparing different-size particles, R was clearly the highest in the Aitken mode, suggesting that MSA and sulfate contribute with comparable magnitudes to nuclei condensational growth at high latitudes during the summer. The evident variation of R with particle size, together with potential enhanced MSA production in air influenced by pollution, demonstrate further that one needs to be extremely careful when using observed MSA to nss- SO42- ratios for estimating the contribution of biogenic sources to total particulate sulfate in different environments. Strong indications on the saturation of MSA over accumulation-mode particles were found. The saturation effect was hypothesized to explain, in part, the observed large partitioning of MSA in the supermicron mode in warm and very acidic aerosol systems. The distribution of submicron MSA, including potential saturation, was shown to be affected significantly by cloud processing.

A new cascade impactor for aerosol sampling with subsequent PIXE analysis

A small deposit area low pressure impactor (abbreviated to SDI) has been developed and tested. The device has been designed specifically to collect size-fractionated aerosol samples in remote locations for subsequent chemical analysis by PIXE. The SDI is a 12-stage, multinozzle device, but the deposit for each stage remains confined to an area with diameter less than 8 mm. It operates at a flow rate of 11 L/min and accepts the same, 25 mm diameter substrate rings as the PIXE International cascade impactor. The experimental cut-points for stages 12 through 1 are 8.50, 4.08, 2.68, 1.66, 1.06, 0.796, 0.591, 0.343, 0.231, 0.153, 0.086 and 0.045 μm equivalent aerodynamic diameter. The SDI has been tested in (and employed for) size-fractionated aerosol sampling in the Finnish Arctic and at Summit in Greenland. The data show that the SDI gives results very similar to those obtained with the PIXE International impactor, but with detection limits that are much lower. This suggests that the SDI can be used with shorter sampling times or in areas where concentrations are smaller to obtain reliable size distribution data. The results also suggest that data for a greater number of elements can be obtained with the SDI.

Inorganic ions and ion balance in atmospheric aerosol in the Finnish Arctic

Inorganic ions and ion balance in atmospheric aerosol in the Finnish Arctic

Correlation between particle number concentrations and sulphur dioxide concentrations in the Finnish Arctic

Correlation between particle number concentrations and sulphur dioxide concentrations in the Finnish Arctic

Natural sulphur compounds in atmospheric aerosol in Finnish Arctic

Natural sulphur compounds in atmospheric aerosol in Finnish Arctic