title: A comparison of MAGIC and paleolimnological predictions of preindustrial pH for 55 Swedish lakes.
abstract: Two fundamentally different approaches to define reference conditions for acidification assessments are hydrogeochemical modeling and paleolimnological reconstructions. Both methods have been applied to calculate the preindustrial chemistry for 55 Swedish lakes in two independent studies. This paper investigates whether these methods give similar reconstructions of the preindustrial pH for these lakes. Special focus has been attached to the importance of total organic carbon concentrations and CO2 partial pressure (pCO2) in the conversion from ANC to pH in the hydrogeochemical modeling. With a uniform pCO2 value for all the lakes of 0.63 matm, the mean absolute difference between pH from the hydrogeochemical model and the paleolimnological pH was +0.23 units (mean absolute difference 0.36 units). If instead a lake specific preindustrial pCO2 is assumed, equal to contemporary pCO2, the mean difference in the predicted preindustrial pH between the two methods was reduced to +0.03 units (mean absolute difference 0.22 units). Statistical analyses indicated that with a lake specific pCO2, the difference between the reconstructions is smaller than 0.13 pH-units at a 95% level of significance. The results of this study build confidence in the reliability of both methods, providing that lake-specific estimates of pC02 are used.
authors: Department of Environmental Assessment, Swedish University of Agricultural Sciences, Box 7050, 75007, Uppsala, Sweden. Martin.Erlandsson@ma.slu.se
authors: Martin
authors: M
authors: Erlandsson
authors: Kevin
authors: K
authors: Bishop
authors: Jens
authors: J
authors: Fölster
authors: Matilda
authors: M
authors: Guhrén
authors: Tom
authors: T
authors: Korsman
authors: Veronika
authors: V
authors: Kronnäs
authors: Filip
authors: F
authors: Moldan
mesh_terms: D002244:Carbon / Q000032:analysis; D002245:Carbon Dioxide / Q000032:analysis; D017377:Diatoms; D005618:Fresh Water / Q000737:chemistry*; D019015:Geologic Sediments / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007221:Industry; D008962:Models, Theoretical; D013548:Sweden
chemical_list: D002245:Carbon Dioxide; D002244:Carbon