| Analysis of winter stream chemistry data from the Afon Hafren in mid-Wales
reveals links between stream chemistry and the North Atlantic Oscillation (NAO). K, Y, Al
and dissolved organic carbon (DOC) concentrations increase during high NAO index months
(relatively warm and wet weather), while Ca, Mg and NO3 concentrations increase
during low NAO months (relatively cold and dry conditions) with the increased concentrations
lasting into the next month. The cause of the concentration changes varies between
constituents: Y, Al and DOC are impacted by short term variations in rainfall; Mg and Ca
are influenced by flow conditions; and NO3 is temperature controlled. The
dominant control mechanism for K concentration seems to be related to rainfall after tree
felling has taken place but, prior to felling, the relationships are less certain.
Keywords: nitrate, potassium, yttrium, aluminium, Dissolved Organic Carbon, magnesium,
calcium, North Atlantic Oscillation, stream chemistry, Plynlimon, Hafren |