These data are based on the UK rainfall chemistry data held on the UK-AIR database operated on behalf of Defra (http://uk-air.defra.gov.uk/). A subset of 20 sites was analysed, being those with the longest continuous data record from 1986 to 2011. Rainfall samples from bulk collectors were taken weekly or two-weekly at sites across the UK and analyzed by a central laboratory. The raw reported data contain some samples which were contaminated by bird droppings, or...