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Small Scale Heterogeneity of Soil Chemical Properties: Effects on Spring Water Chemistry
Author(s) -
Kaupenjohann Martin
Publication year - 2000
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/(sici)1522-2624(200004)163:2<203::aid-jpln203>3.0.co;2-4
Subject(s) - chemistry , saturation (graph theory) , spring (device) , environmental chemistry , soil water , soil ph , base (topology) , mineralogy , soil science , environmental science , mechanical engineering , mathematical analysis , mathematics , combinatorics , engineering
Previous soil and spring water analyses in small catchments revealed low pH values in the spring water during high discharge events. This paper analyses the potential which small scale heterogeneity of soil acidity may have to explain decreasing spring water pH as a result of high discharge. Soil aggregates were collected from a C‐horizon of a Spodosol in the Fichtelgebirge. Exchangeable cations and soil solution were examined on both samples from the surfaces and the cores of aggregates which were obtained by a mechanical separation procedure. The Reuss‐Johnson soil chemical equilibrium model was used to predict soil and spring water pH values as a function of acidic input and soil air CO 2 concentration in equilibrium with both aggregate fractions. Ranges of acidic input from 160—570 μeq L −1 and soil air CO 2 concentrations from 0.1 to 3 Vol. % were considered. The model predicted spring water pH values from 5.0 to 5.3 for the acidic aggregate surface samples (base saturation = 12.5%) and from 6.8 to 7.2 for the aggregate core samples (base saturation = 32.1%). The results suggest that small scale acidity gradients may expand the range of predictable spring water pH values. However, very low pH values (<5) still need additional explanation.