Journal article
Seasonal Variability of Adsorption and Exchange Equilibria in Soil Waters
Aquatic geochemistry, Vol.4(2), pp.273-290
06/1998
Handle:
https://hdl.handle.net/2376/104298
Abstract
Chemical analyses for major ions have been conducted on waters,collected on an approximately weekly basis over the period April, 1993 toNovember, 1996, that drain three small experimental ecosystems(“sandboxes”) at Hubbard Brook, New Hampshire. One sandbox is planted withpine trees, another with grass, and the third is left “bare” (actually itis covered sporadically by bryophytes and lichens). Results show linearcorrelations, independent of discharge, between the concentrations ofdissolved Na+ and K+ on the one hand andCa++ and Mg++ on the other for all threesandboxes. No correlations between singly charged and doubly chargedcations were found. These correlations are interpreted to represent cationexchange equilibria between soil waters and clay minerals plus soil organicmatter. The correlation slope, representing the exchange constant, for Na vsK is different for the pine-covered sandbox than for the other two whereasfor Ca vs Mg the correlation is independent of the presence or absence oftrees. We interpret this as representing a shift of cation exchangeequilibria in the pine sandbox by the activities of growing trees.Concentrations of Na, K, Ca, Mg, and H4SiO4from the barren and grass-lined sandboxes were found to vary seasonally witha marked sinusoidal pattern which was independent of the discharge from eachsandbox. (The discernment of a similar pattern in the tree lined sandbox wasdifficult due to a lack of discharge over much of the year.) Concentrationmaxima occurred in August and minima in February, and there is a closeparallelism with soil temperature. We interpret this as representingtemperature induced variations in cation exchange equilibria and silicaadsorption. Independence from highly varying water discharge, e.g.,. thataccompanying severe rainstorms, indicates rapidly re-attained equilibrium.Variations in the concentrations of cations are likely due to exchange withunmeasured cations, probably H+ or dissolved Al species, as aresult of possible seasonal changes in internal acid production and externalinput of acid rain to the sandboxes. Internal production may represent aresponse to seasonal changes in respiration rate as it responds toseasonally varying temperature. Added to this is the effect of temperatureon exchange equilibrium. Seasonal variations in dissolved silica are mostlikely due to the dependence of adsorption/desorption equilibria ontemperature. The temperature dependence of a number of silica-consumingreactions are consistent with the measured values.
Metrics
4 Record Views
Details
- Title
- Seasonal Variability of Adsorption and Exchange Equilibria in Soil Waters
- Creators
- Robert Berner - Dept. of Geology and Geophysics Yale University New Haven CT 6520-8109 USAJi-Long Rao - Dept. of Geology and Geophysics Yale University New Haven CT 6520-8109 USASoobum Chang - Dept. of Geology and Geophysics Yale University New Haven CT 6520-8109 USARachel O'brien - Dept. of Geology Washington State University Pullman WA 99164-2812 USAC Keller - Dept. of Geology Washington State University Pullman WA 99164-2812 USA
- Publication Details
- Aquatic geochemistry, Vol.4(2), pp.273-290
- Academic Unit
- Environment, School of the (CAS)
- Publisher
- Kluwer Academic Publishers; Dordrecht
- Identifiers
- 99900546838301842
- Language
- English
- Resource Type
- Journal article