The Met Office has continued to detect evidence of ash dust over the UK, and there have been some reports of it falling to the ground.
A research flight by the Natural Environment Research Council, commissioned by the Met Office, has flown over the North Sea and detected three distinct layers of ash, from fine particles at low levels to large particles around 8,000 feet.
Dust collected at Lerwick and Aberdeen has been analysed by Scottish Environment Protection Agency.
Preliminary analysis has shown that the properties of the particles appear to be consistent with the properties of volcanic ash, but further more detailed analysis is being undertaken.
Yesterday, Sepa said its readings from Scotland's air quality and radioactivity monitoring networks continued to be normal, with no areas of concern.
Rainfall samples collected over the weekend will be returned to Sepa laboratories today for analysis.
And this week, further work will be undertaken in partnership with a range of other organisations to monitor soil and vegetation, and to do further more detailed analysis of samples of volcanic ash collected in dust filters at sampling sites across the country.