Volcanic ash cloud – the latest news from SEPA – update 6
EXT01 – B05
The Scottish Environment Protection Agency (SEPA) is monitoring
the situation regarding the volcanic ash cloud currently affecting
the UK and its possible impact on Scotland's environment.
SEPA's Director of Science and Strategy, Professor James Curran,
said:
"The greatest environmental concern from volcanic ash, and the
most significant risk to grazing livestock, would be fluoride
content in ash deposits. Information from SEPA's analysis of
Scottish dust samples, and from similar analysis in Norway,
indicates low levels of fluoride in the current Icelandic ash
plume.
"The latest rainwater samples analysed also indicate no cause
for concern - pH and fluoride levels are entirely consistent with
normal rainwater in Scotland. We are detecting small increases in
some volcanic contaminants, particularly iron, manganese and
copper. We will continue our programme of monitoring but, based on
the ash, rainfall and snowfall samples analysed so far, there is
minimal risk to the environment."
Ongoing monitoring
SEPA has been carrying out monitoring and analysis on four areas
of the Scottish environment – ambient air quality; rainwater and
snowfall; deposited ash particles; and vegetation. Samples
collected, covering all these areas, have been conveyed to SEPA
laboratories by SEPA staff, other volunteers and partner
organisations such as the Scottish Agricultural College (SAC).
Ongoing analysis is being supported by the Macaulay Institute and
Edinburgh University.
Air quality
The Scottish Air Quality Database (SAQD) contains the most
up-to-date continuous ambient monitoring information across
Scotland. Members of the public can access this information at
www.scottishairquality.co.uk.
All concentrations remain generally low across Scotland and
therefore there is no cause for concern. Some monitoring sites have
been experiencing some small changes in the concentration of
sulphur dioxide (SO2) and particulate matter. These
fluctuations are entirely normal and reflect daily ongoing
activities eg road traffic.
Radiation measurements are taken across the UK and Europe via
the RIMNET monitoring network. Readings show no evidence that the
volcanic ash contains radioactive materials of any
significance.
Rainwater analysis
Analysis of 28 samples of rainwater and snow has been undertaken
to assess the environmental impact of the volcanic ash deposition
across Scotland.
All sample results to date for fluoride, sulphate, nitrate and
chloride show levels which are below accepted standards and
guideline values.
The pH level of the samples was also analysed. pH measures the
concentration of hydrogen ions in solution and is the commonly
accepted measure of acidity and alkalinity, using pH units that
range from 0 to 14, with 0 to 7 reflecting acidic conditions, 7
neutral and 7 to 14 alkaline conditions.
Rainwater in Scotland is normally between 4 and 7 pH units.
Occasional acidic events are observed in Scotland and pH readings
can be as low as 2.5.
The results from the samples analysed by SEPA are all between 4
and 7 pH units and as such are typical of normal Scottish
rainfall.
The samples analyzed to date indicate no cause for
concern with minimal risk to the environment.
Deposited ash analysis
SEPA is monitoring deposits of ash taken right across the
country and ash deposition rates remain low. Analysis of the
particles collected is being undertaken by SEPA.
The analysis of sticky pads continues to show that very few dust
particles are being deposited.
The majority of the samples analyzed have displayed properties
consistent with those of volcanic ash.
Vegetation
On behalf of SEPA, the Scottish Agricultural College (SAC) has
collected 10 samples of grass from across Scotland. These are now
being analyzed by SEPA scientists, who will wash the samples and
analyse the run off to ascertain if there are any potential hazards
for grazing animals and the wider environment. Given that no
adverse effects have been observed in rainwater and dust deposits,
we do not expect to see any issues of concern.
Future work
Although it is spring, there have been recent snowfalls in
upland areas across Scotland. Snow is a particularly good medium
for absorbing dust particles from the atmosphere. Snow melt can
pass straight into rivers and, given that spring time is a
particularly important time of the year for spawning and junior
aquatic species, it is important that we monitor and assess its
likely environmental impact. The Scottish Avalanche Information
System (SAIS) is now collecting samples of snow on behalf of SEPA
and transporting them to our laboratories. We have now analysed a
number of snow samples and are not finding any indications of areas
of concern, but our ongoing monitoring allows us to provide further
reassurance about the environmental impacts.
Ends
Questions and answers
Q: What is Fluoride?
A: Fluoride is a commonly occurring chemical. It is present in
small amounts in the body and its primary function is to strengthen
the bones. It is well known for its use in toothpastes to prevent
tooth decay.
Fluorides are naturally occurring in the environment through the
weathering of rocks and in releases of gases from volcanoes. The
most important natural source of fluoride is from bedrock. Fluoride
can enter groundwater from the weathering of bedrock and can
subsequently reach surface and sea water.
Environmental releases of fluoride can occur through industrial
processes such as aluminium smelting and through natural processes
including volcanic eruptions. Volcanoes emit a variety of gases
both between and during eruptions, including hydrogen fluoride. The
hydrogen fluoride reacts with the ash particles to form various
forms of fluoride.
Q: Why are we concerned about fluoride?
A: Like many chemicals, a small amount of fluoride is essential
for life, but an excessive amount can cause concern. High levels of
fluoride can have adverse effects on the environment, including
impacts on sensitive species, such as caddis flies and migratory
salmon, impacts on crops and on livestock.
The levels of fluoride that we have detected are consistent with
background levels expected and far lower then accepted standards
and therefore present no cause for concern.
Q: What is pH and why are we measuring it?
A: pH is a measure of acidity and is related to the
concentration of hydrogen ions. pH values range from 0 to 14. Pure
water has a pH of 7 and is described as neutral. Water with pH
below 7 is described as acidic and above 7 as alkaline.
The presence of acidic substances in water will influence the pH
because acids provide hydrogen ions. Alkaline substances in water
will raise the pH. Rain water is naturally mildly acidic because of
interactions with gases in the atmosphere, and the normal range of
pH is from approximately 4 to 7.
Acids can be released naturally from soils and plants and so
streams can have a pH in the range of 4.5. Due to alkaline
substances which can be released from soils and rocks streams can
also naturally have a higher pH up to around 8.5. Acidifying
substances can be released into the environment from natural and
man-made sources. These can include emissions to air from natural
sources such as volcanic eruptions.
pH is one of the most important variables in the environment and
it is known as a 'driving variable' because it can influence most
chemical and biological processes. For this reason, it is one of
the primary parameters monitored in the environment.
Q: What are the environmental consequences of lower
pH?
A: Inputs of acidifying substances can lead to acidification of
the environment. In freshwater acidification can have impacts on
the ecology and water quality. Some species of fish, aquatic
invertebrates and plants are sensitive to acidic (or lowered pH)
conditions. Fish eggs and fry are particularly at risk, as lowered
pH can affect their chance of survival and development. If
acidification is severe, it can lead to the disappearance of some
sensitive species and potentially to a loss of biodiversity.
Some pollutants including metals (such as lead, aluminium, zinc
and cadmium) become more water soluble and so can be more toxic at
lower pH. This may be an underlying cause of some of the damaging
effects of acidification in freshwaters.
Q: How do we recognise the effects?
A: SEPA monitors pH routinely across Scotland in rivers and
lochs, so we are well placed to recognise the occurrence and
effects of a pH change. We also monitor aquatic invertebrates at
numerous sites and have long-term data from sites that have
historically been affected by acid rain.
A Mayfly nymph; an example of an acid sensitive aquatic
invertebrate (photo by Tim Foster).
Q: What is SEPA doing?
A: SEPA have already collected and analysed rainfall samples for
fluoride and pH. The pH of rainwater (4.7 – 6) analysed since the
volcanic ash event are within the normal range we would expect for
rainwater.
The concentrations of fluoride detected are similar to natural
background concentrations reported elsewhere and are well below
those of environmental concern.
Samples of snowmelt, dust/ash and vegetation have been collected
and we are in the process of analysing these samples.