Patterns of storm runoff chemistry from a wollastonite (calcium-silicate mineral, CaSiO3) treated watershed (W1) were compared with a reference watershed (W6) at the Hubbard Brook Experimental Forest (HBEF) in New Hampshire (NH), USA to investigate the role of Ca2+ supply in the acid-base status of stream chemistry. In the summer of 2003, six storm events were studied in W1 and W6 to evaluate the effects of the wollastonite treatment on the episodic acidification of stream waters. Although mean values of Ca2+ concentrations decreased slightly from 33.8 to 31.7 μmol/L with increasing stream discharge in W1 during the events, the mean value of acid neutralizing capacity (ANC) was positive (1.2 μeq/L) during storm events, compared to negative values (- 0.2 μeq/L) in W6. This pattern is presumably due to enhanced Ca2+ supply in W1 (20.7 to 29.0% of dissolved Ca2+ derived from the added wollastonite) to stream water as a result of interflow along shallow flowpaths. In addition, the application of wollastonite increased pH and dissolved silica (H4SiO4) concentrations, and decreased the concentration of inorganic monomeric Al (Ali) in W1 in comparison with W6 during storm events. Despite an increase in SO4 2- concentration, likely due to desorption of sulfate from soil after the treatment, the watershed showed an increase in ANC compared to the reference watershed, serving to mitigate episodic acidification.
- Acid neutralizing capacity
- Episodic acidification
- Hubbard Brook Experimental Forest
ASJC Scopus subject areas
- Environmental Chemistry
- Waste Management and Disposal
- Environmental Engineering