Acid episodes in the Allt a’Mharcaidh, Scotland: an investigation

• Main Authors: Muriel C. Bonjean, Michael Hutchins, Colin Neal
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: acidic episodes; stream; sub-hourly monitoring; sea-salt conductivity; Antecedent Runoff Index; North Atlantic Oscillation; UKAWMN; Mharcaidh; North Atlantic; North Atlantic oscillation
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.371.7186; http://hal.archives-ouvertes.fr/docs/00/30/56/19/PDF/hess-11-340-2007.pdf

Stream waters in the Allt a’Mharcaidh catchment (Cairngorms, Scotland) have been monitored for flow, conductivity and pH at sub-hourly resolution; and for a range of chemical, biological and physical parameters, less intensively, since the mid-1980s. The Allt a’Mharcaidh stream is subject to acidic events (pH<5.5) triggered by both hydrology and sea-salt inputs from the atmosphere. This paper investigates the drivers of these acidic events using variables derived from sub-hourly monitored data. It also examines the influence of the North Atlantic Oscillation (NAO) on episode severity. Sub-hourly datasets are used to derive multiple regression models expressing stream H + concentration as a function of the sea-salt conductivity and the peak instantaneous flow rate amongst other explanatory variables. The relationship between sea-salt conductivity and the NAO is significant but hidden due to issues such as time lags and the influence of atmospheric patterns other than the NAO.