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: