Ionic concentrations in a blanket peat bog in northern England and correlations with deposition and climate variables

Abstract

Summary Soil solution was collected to identify seasonal trends in its chemistry and to examine relationships between the concentrations of ions and variables that may control them. Samples were collected fortnightly at 10 cm and 50 cm depth in a blanket peat soil at Moor House–Upper Teesdale National Nature Reserve in the northern Pennine uplands of England. Dissolved organic carbon at 10 cm peaked each summer and correlated most strongly with temperature. At both depths Na + and Cl – were the dominant ions, reflecting the oceanic climate. Over the 3‐year sampling period, concentrations of the principal anions and cations at 10 cm varied little except during the autumns of 1994 and 1995 following unusually dry summers. At these times concentrations of SO 4 2– ‐S increased from < 3 μmol to a maximum of 430 μmol and were balanced by smaller increases in Na + , Mg 2+ , Ca 2+ and H + . The SO 4 2– concentration at 10 cm was most strongly correlated with depth to the water weeks prior to sampling. At 50 cm depth in the peat a small increase in SO 4 2– occurred only during the autumn of 1995, and the concentration of SO 4 2– at this depth correlated most strongly with that at 10 cm. At neither depth were there any strong correlations with deposition. The increase in H + concentration associated with the peak in SO 4 2– at 10 cm depth represents a fall in pH from usual values around 4.2 to 3.5. Deposition flux of ions in bulk precipitation at Moor House from weekly samplings 1994 to 1996 in kg ha −1 year −1 . The UK flux is derived from 32 sites of the United Kingdom Precipitation Composition Monitoring Network 1992 to 1994 and the standard deviation (SD) relates to the variation between these sites () Moor House flux UK flux UK SD H + 0.31 0.26 0.10 Ca 2+ 4.07 3.58 1.86 Mg 2+ 3.37 3.62 2.62 K + 1.54 Fe 2+ 0.73 Al 3+ 0.44 Na + 29.32 25.77 19.27 Cl – 51.14 45.96 32.39 NO 3 – ‐N 4.01 3.20 1.05 NH 4 + ‐N 4.85 3.63 1.74 SO 4 2– ‐S 8.98 7.98 3.09 PO 4 3– ‐P 0.01