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Environmental problems - Chemical approaches
RESEARCH ARTICLE

Long-term responses in soil solution and stream-water chemistry at Hubbard Brook after experimental addition of wollastonite

Shuai Shao A , Charles T. Driscoll A E , Chris E. Johnson A , Timothy J. Fahey B , John J. Battles C and Joel D. Blum D
+ Author Affiliations
- Author Affiliations

A Department of Civil and Environmental Engineering, 151 Link Hall, Syracuse University, Syracuse, NY 13244, USA.

B Department of Natural Resources, G16 Fernow Hall, Cornell University, Ithaca, NY 14853, USA.

C Department of Environmental Science, Policy and Management, 137 Mulford Hall #3114, University of California, Berkeley, CA 94720, USA.

D Department of Earth and Environmental Sciences, 1100 North University Avenue, University of Michigan, Ann Arbor, MI 48109, USA.

E Corresponding author. Email: ctdrisco@syr.edu

Environmental Chemistry 13(3) 528-540 https://doi.org/10.1071/EN15113
Submitted: 2 June 2015  Accepted: 10 October 2015   Published: 18 December 2015

Environmental context. Calcium silicate was added to a forest watershed in New Hampshire, USA, to accelerate its recovery from acid rain. The acid–base status of soil and stream quality improved over the 12-year study, with the most pronounced response in the upper elevation and the upper soil of the watershed. A total of 95 % of the added calcium and 87 % of the added silica were retained in the watershed over the study period.

Abstract. In October 1999, 3450 kg ha–1 of wollastonite (CaSiO3) was applied to Watershed 1 at the Hubbard Brook Experimental Forest in New Hampshire, USA, with the objective of restoring calcium that had been depleted from soil-exchange sites by chronic inputs of acid deposition. After the treatment, the concentrations and fluxes of calcium and dissolved silica significantly increased in both soil solution and stream water throughout Watershed 1, as did the acid-neutralising capacity. The concentrations and fluxes of inorganic monomeric aluminium significantly decreased. The treatment improved the acid–base status and decreased the potential for aluminium toxicity in stream water, especially in the lower reaches of the watershed. Approximately 4.7 % of the added calcium and 17 % of the added silica from the wollastonite treatment was exported from Watershed 1 in stream water by the end of 2010. Meanwhile, ~1825 mmol m–2 of the added calcium and 2125 mmol m–2 of the added silica were either transported to lower mineral soil horizons – as particulate wollastonite, or as dissolved solutes (calcium 77.6 mmol m–2; silica 592.2 mmol m–2), thus contributing to increases in soil pools – or were taken up by vegetation and incorporated into internal calcium and silica cycles of the watershed ecosystem. This experimental wollastonite addition was an effective tool for mitigating the acidification of the ecosystem and restoring the calcium status and forest health of this base-poor watershed.


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