Aerosol Instruments

For more information about Aerosol Instruments and data, please, contact Dr. Patrick Hayes or Dr. Rachel Chang

Over the past decades, particle sizing spectrometers have been increasingly used in atmospheric aerosol research for long-term observations of particle size distributions in the super- and sub-micrometer diameter range. The particle number size distribution of atmospheric aerosols is a fundamental parameter required in calculations of the effects of aerosols on Arctic climate, cloud formation, human health, and ecosystems. It is also an essential parameter with regard to the description of aerosol sources and dynamic processes as well as heterogeneous chemical reactions in the Arctic atmosphere.

Fig1. OPC on the left / SMPS on the right

Among the most commonly used particle sizing instruments are the Optical Particle Counter (OPC) and the Scanning Mobility Particle Sizer (SMPS), which both provide fast and accurate measurement of particle concentration and particle size distribution using the well-established light scattering technology. At Eureka, the Ridge Lab of the Polar Environment Atmospheric Research Laboratory (PEARL) is equipped with an OPC and an SMPS to perform real time and continuous aerosol measurements in the Canadian High Arctic. Both instruments are located in the UV-Vis lab and are connected through a series of copper and stainless steel tubing to a common aerosol inlet placed 2.2 m above the roof of the PEARL Ridge Lab building.

Fig 2. Diagram of a Scanning Mobility Particle Sizer

The SMPS measures particle sizes based on the principle of mobility of a charged particle in an electric field. The three main components of the conventional SMPS are a bipolar diffusion charger (or traditionally named neutralizer), a Differential Mobility Analyzer (DMA), and a Condensation Particle Counter (CPC).

Particles are detected and counted by laser scattering in a very similar way to a standard OPC. Particle sizing using the OPC is based on the detection of light scattered from individual particles in real time. Every single particle is drawn through a laser beam and the resulting scattered light is collected by a parabolic mirror and focused on a photodetector. The number concentration is determined by the count rate, and the size of the particles is estimated from the pulse height.

Fig 3. Principle of an Optical Particle Counter

A detailed understanding of the relevant processes that control the Arctic aerosol number and size distributions year-round is required to gain a predictive understanding of Arctic climate as sea ice extent decreases. Our SMPS and OPC measurements at the PEARL Ridge Lab are targeted to address some of the unresolved aerosol processes and to contribute to improving model skill in simulating both the Arctic aerosol seasonal cycle and climate impacts. The key processes we are looking at with these instruments are the following:

  • Assess the response of both natural and anthropogenic Arctic aerosols to increased emissions of natural aerosols and precursors and increased human activity in the region due to sea ice retreat;
  • Determine the relative contribution of aerosol nucleation and growth events in the summer Arctic to particle size distributions;
  • Examine the properties of primary aerosols produced from snow and ice processes (e.g. blowing snow, frost flowers) and their strong impacts on the winter–spring size distribution;
  • Identify the mechanism and efficiency of aerosol lifetime and removal with the Arctic aerosol seasonal cycle, particularly during the winter and spring;
  • Quantify the seasonality of aerosol optical properties, especially the complex refractive index, and theirs impacts on the Arctic climate from the combined optical and size distribution data sets.