Aerosols In the Environment Meeting at the IOP

April 2011

Just got back from attending the Aerosols in the Environment technical meeting at the Institute of Physics in London.

This was a joint meeting with the IOP Environmental Group and the Aerosol Society and was well attended by 35 people from a range of academia, meteorological groups and aerosol characterisation instrument suppliers.

As some reading this may know, my background is in high efficiency filtration and so I’m quite new to this area of environmental aerosol science.  However, having originally joined the Aerosol Society back in the 1980’s and only rejoined last year, it was interesting to see such a level of activity still on-going, listen to the developments made over that time and meet up with people involved.  I enjoyed and learned from all the presentations given and I add a personal impression from the presentations given at the meeting below. (I hope that the full presentations will be made available at either the IOP / Aerosol Society)

Prof Ian Ford – Current understanding of aerosol nucleation in the environment
I suppose that I always considered particles to be formed from breakdown activity i.e. particles are formed from the breakdown of some sort of bulk.  I’m familiar with a simple condensation process where a particle passing through a saturated vapour initiates a growth by condensation. This is the principle used in CPC’s to grow small particles to a size large enough to be counted using optical systems, but I confess that the subject of nucleation, describing the formation of particles from molecular agglomeration hadn’t really occurred to me, so a whole new vista was opened at this meeting.

Prof Ian Colbeck – Indoor Aerosols
Indoor Aerosols are an area of interest for a filtration specialist and instrument supplier, as much of our work is involved with HEPA / ULPA filtration systems used in HVAC installations and more recently I’ve been involved in vacuum cleaner assessments.  It was interesting to see a ‘tricked up’ house being monitored with every instrument you can think of to identify sources of indoor aerosol and other contaminants.  I have to admit to being rather unsurprised that cooking and walking across carpets re-suspending dusts was found to be some of the highest source of particulates in the homes monitored.  However, following this talk I now have evidence that this is a significant source of re-suspended aerosols in homes in the developed world and a significant reason for not vacuuming!!
Additional monitoring results were offered from Pakistan, but here again the rather unsurprising result was that cooking with open wood burning stoves in a closed area and heavy smoking at social events without ventilation were the major causes of extremely high respirable particulate levels. The location of animals close to the cooking and food prep areas also gave high biological loadings in the aerosols.  I suppose with these type of issues you still need to measure the parameters to prove and quantify levels.  The values measured are certainly huge in comparison to those tolerated in the developed world.

Dr Claire Ryder – Using aircraft measurements to determine the radiative effect of Saharan Mineral Dust
Did you know that dusts blown up from the Sahara travel across the Atlantic to North and South America and did you know that the level of dust in the atmosphere contributes to global cooling?  Having already been covered by Prof Ford in his presentation described as some form of ‘active intervention’, I now have a mental picture of atmosphere modifier stations seen in some sci-fi movies; huge chimneys sucking up desert dusts and pumping particles high into the atmosphere to cool the earth down!
Anyway, to see the data and pictures of the dust plumes being tracked and the impact measured by researchers flying in a BEe-146 aircraft through these, taking samples and making measurements was again an eye opener for me.  The global scale of influence of desert sourced dusts was a bit of a surprise and the influence of the material type in terms of adsorption of incoming radiation was again a learning experience for me.  Brave people these researchers, deliberately flying into hazardous environments for aircraft!

Prof Colin O’Dowd – Biogenic influences on marine primary and secondary particle formation – recent advances
Once again, I hadn’t really thought too much about the major sources of aerosols and the influence of the oceans.  Many of our client’s filter development focus, particularly for turbine protection, has been related to protection of equipment on offshore installations and most of the particulate dealt with, at least that I was aware of was sea salt.  The impact of the aerosol generation from the oceans turns out to be highly significant, with phytoplankton blooms in the oceans contributing seasonally to this impact.
Fascinating to see the sources of biogenic derived aerosols and have presented so visually the seasonal variation associated with both particle size and aerosol character.  It was interesting to see nucleation taking place out at sea with particles ‘grown’ some 1500km offshore from the Mace Head Atmospheric Research Station measurement site on the coast of Ireland, then being picked up by instruments measuring in the micron range, together with more local nucleation events with particles recorded in the sub-10 nanometer range.  It was also surprising to me that the Mace Head monitoring station had been collecting data for over 50 years.

Dr Ben Murray – Glassy aerosols and their role in ice cloud formation
A very entertaining review of a ‘new’ form of aerosol matter, glassy materials or very high viscosity fluids (like glass) with a non-crystalline structure.  The example shown of a slurp of Golden Syrup chilled in liquid nitrogen to form a brittle fluid visualised brilliantly, for this simple soul, what was being discussed.
The physics behind this was certainly interesting and the lack of re-crystallisation at low humidity / low temperature was fascinating.  I loved the use of highly technical equipment, an ‘allen key’, used to shatter the glassy droplets formed in a Raman spectroscopy experiment and then to see the AIDA Cloud Chamber in Karlsruhe (Palas GmbH being based in Karlsruhe) again being used to form these aerosols simulating the upper atmosphere and demonstrating what a novel and capable facility this is.
I wonder whether other applications of this material type may be developed in the future, apart from developing a better understanding what is going on in cloud formation.

Dr Evgenia IIyonskaya – Eyjafallajokull Volcano 2010: Volcanic ash in the atmosphere during and after the eruption
I have to confess to this presentation being my favourite and a good one to finish the day with.  Some fantastic photos, amazing stats and a reminder to all of the impact of a single natural event on a huge region of the developed world, which we were powerless to do anything about.  Tens of tonnes per second of material were being pumped into the atmosphere, with up to 7% as particles smaller than 1um!  The plume reached over 7km and was carried in the winds of the upper troposphere / lower stratosphere towards central Europe resulting in air traffic disturbances.
An interesting and worrying aspect is that even now, over one year on, re-suspended ash is still causing health concerns in Iceland.  This is apparently an unprecedented situation in Iceland and therefore no indication can be made of when this threat will reduce.  I think that it was surprising to most of the audience that this re-suspension issue continues to present problems to the Icelandic people.

My thanks to the organisers and presenters and we will see what is reported in developments at the next meetings.

If you are interested in aerosol science then can I recommend the Aerosol Society and the IOP’s Environmental Physics Group .

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