The response of a small stream in the Lesni potok forested catchment, central Czech Republic, to a short-term in-stream acidification

Abstract

Lesni Potok stream drains a forested headwater catchment in the central Czech Republic. It was artificially acidified with hydrochloric acid (HCl) for four hours to assess the role of stream substrate in acid-neutralisation and recovery. The pH was lowered from 4.7 to 3.2. Desorption of Ca and Mg and desorption or solution of Al dominated acid-neutralisation; Al mobilisation was more important later. The stream substrate released 4,542 meq Ca, 1,184 meq Mg, and 2,329 meq Al over a 45 m long and 1 m wide stream segment; smaller amounts of Be, Cd, Fe, and Mn were released. Adsorption of SO 4 2 and desorption of F occurred during the acidification phase of the experiment. The exchange reactions were rapidly reversible for Ca, Mg and SO 4 2 but not symmetric as the substrate resorbed 1083, 790 and 0 meq Ca, Mg, and Al, respectively, in a 4-hour recovery period. Desorption of SO 4 2 occurred during the resorption of Ca and Mg. These exchange and dissolution reactions delay acidification, diminish the pH depression and retard recovery from episodic acidification. The behaviour of the stream substrate-water interaction resembles that for soilsoil water interactions. A mathematical dynamic mass-balance based model, MASS (Modelling Acidification of Stream Sediments), was developed which simulates the adsorption and desorption of base cations during the experiment and was successfully calibrated to the experimental data.

Experimental acidification of two biogeochemically-distinct neotropical streams: Buffering mechanisms and macroinvertebrate drift

“…A six month experimental addition of sulfuric acid (H 2 SO 4 ) to a stream in the Hubbard Brook Experimental Forest increased export of Al i , Ca 2+ , Mg 2+ , and K 2+ , and decreased aquatic insect emergence (Hall et al, 1980). Short term (b24 h) acidification experiments report similar buffering mechanisms in response to inorganic acid addition: sediment release of base cations, release of Al i , adsorption of SO 4 2− , and protonation of bicarbonate (HCO 3 − ) and weak organic acids (Hedin et al, 1990;Hruska et al, 1999;Navratil et al, 2003;Norton et al, 1992;Norton et al, 2000). Environmental conditions and underlying geology determine the relative importance of these buffering mechanisms (Goss and Norton, 2008).…”

Forest vegetation affecting the deposition of atmospheric elements to soils

“…Mean annual surface water discharge was 2.24 L s −1 between 1997-2005. The significant difference between the water input and output was due to ∼80% evapotranspiration (NAVRÁTIL et al, 2003). The annual average air temperature is +7…”

Amorphous Aluminum Hydroxide Control on Sulfate and Phosphate in Sediment-Solution Systems

“…Sorption of excess SO 4 onto stream sediment retards acidification and desorption delays recovery from acidification (Norton et al 1999;Navratil et al 2003). By inference, soils should behave similarly.…”