Grimsvotn volcanic eruption

As with the Eyjafjallajökull volcanic eruption last year, the Scottish Environment Protection Agency (SEPA) has been closely monitoring the latest volcanic eruption from Iceland and the impact of the resultant ash cloud on Scotland's environment.

SEPA is monitoring air quality, and collecting and analysing dust and rainwater samples, looking for volcanic contaminants such as iron, manganese and copper and monitoring pH and fluoride levels.

Volcanic ash in Lerwick

On Tuesday 24 May a number of cars in Shetland, Thurso and Orkney were reported to have a covering of dust, suspected to be volcanic ash. SEPA staff used a piece on clean cloth to collect a sample of this dust from a car in Lerwick, Shetland and sent it to SEPA's laboratory in Aberdeen for analysis.  

                

Picture 1 – Car covered in 'volcanic' dust

Picture 2 – Ash collected from a car in Lerwick

The ash sample was viewed under an optical microscope at magnifications of < 200x and 400x. Measurements of particles of this size are presented in micrometres (μm). A single human hair strand usually has a diameter of between 20 and 180 μm. The analysis shows a mixture of particle sizes ranging from 7.5ųm to 122.4ųm. The particles were a mixture of types and colours – greyish, more rounded aggregates, glassy square/angular particles, and long glassy shards.

The optical microscopic analysis did not allow the source of the material to be determined and so SEPA asked our colleagues at the James Hutton Institute in Aberdeen to put the sample through more detailed Scanning Electron Microscopy (SEM) to try to determine whether this material was volcanic in nature. 

Figure 1: SEM – particle size range

The SEM results show both fine and coarse particles. The fine ash particles seen by SEM showed 'aggregates' or 'clusters' of ash around normal dust/sand particles. The larger particles are mainly quartz, potassium (K)-feldspar and other un­determined alumino-silicate minerals which likely come from the immedi­ate surrounding environment. The finer particles are present in abundance and consist of highly angular particles, ranging in size from 3 to 10μm.

Figure 2: Fine particles

 

 

Figure 3: Volcanic glass aggregate                                        

The shape and structure of the fine particles, together with their elemental composition (as determined qualitatively by Energy Dispersive Spectroscopy (EDS)) is consistent with that of volcanic glass (Figure 3).

                                                                                                                      

Figure 4: Volcanic glass aggregate – texture and Figure 5: Volcanic glass aggregate – texture (5x   magnification of Figure 4 – concave 'bubble' visible in centre of image)

The EDS signature of this volcanic glass is slightly different (lower sodium and potassium; higher magnesium).from that of the volcanic glass collected during the Eyjafjal­lajokull eruption last year.

 

Grimsvotn Vs Eyjafjallajökull

Using optical microscopy, SEPA scientists also compared two further dust samples collected recently in Stornoway and Orkney to a sample of volcanic ash collected in Iceland from the 2010 Eyafjallajökull eruption. The results (shown in Figures 6 and 7) show aggregate material similar to that from the Shetland sample.

 

Figure 6: Stornoway sample                                             Figure 7: Eyjafjallajokul 2010 sample

 

Rainfall Network

The rainfall monitoring network established during the 2010 Eyjafjallajökull eruption has been reactivated. This network of 38 sites across Scotland is manned with volunteer rainfall observers. Samples should start to arrive by Friday 27 May and will be analysed for pH and fluoride.

SEPA staff have also been collecting rainwater samples and these are being analysed for pH, fluoride, iron, manganese and copper. So far, pH levels have been consistent with levels expected in Scottish rainfall and show no cause for concern.

Air quality

The Scottish Air Quality Database (SAQD) contains the most up-to-date continuous ambient air monitoring information across Scotland. Members of the public can access this information at www.scottishairquality.co.uk. Results from this database on 26 May showed no significant increase (above expected levels) in sulphur dioxide (SO2), nitrogen dioxide (NO2) or particulate matter across Scotland.

As well as reviewing data from this database, SEPA is using its network of existing air monitoring stations to monitor for airborne particulate matter.

The next steps

Although forecasts from the Met Office show that the high density volcanic ash cloud is no longer an immediate threat to the UK, SEPA will continue to gather and analyse dust, rain and air samples where possible and provide updates for the Scottish Government, partner agencies and the general public on any impact to Scotland's environment.  

An assessment of the environmental and human health implications for Scotland following the volcanic eruption event in May 2011 is now available: