Atmospheric deposition acidification

If the weathering rate equals or exceeds the rate of H+ release by the biota, such as would be the case in a calcareous soil, the soil will maintain a buffer in base cations and residual alkalinity. On the other hand, in noncalcareous "acid" soils, the rate of H+ release by the biomass may exceed the rate of H+ consumption by weathering and cause a progressive acidification of the soil. In some instances, the acidic atmospheric deposition may be sufficient to disturb an existing H+ balance... 

In order to verify whether atmospheric deposition directly affects surface water chemistry of high-altitude Alpine lakes, trend analyses were performed for 20 mountain lakes with low alkalinity on the key variables involved in acidification and recovery alkalinity (Gran alkalinity), pH, sulphate, nitrate, base cations (calcium + magnesium). The analysis covers the period 1980-2004 and allows a comparison between atmospheric inputs and surface water quahty. 

Numerous experiments have been conducted to understand the chemical linkages between atmospheric deposition of acidic compounds and acidification of soils, lakes, and streams. Experiments have included additions of acid, exclusion of acids, and the application of limestone (CaC03) or other acid neutralizing compounds to add ANC directly to surface water or sods. Many of the studies are discussed in Dise and Wright (1992), Rasmussen et al. (1993), and Jenkins et al. (1995). We highlight a few studies here. 

Galloway J. N., Norton S. A., and Church M. R. (1983) Freshwater acidification from atmospheric deposition of sulfuric acid a conceptual model. Environ. Sci. Technol. 17, 541-545. 

Acid atmospheric deposition causes acidification of waters and soils if the neutralization of the acids by weathering is too slow. Biologically mediated redox processes are important in affecting the H balance. Among the redox processes that have a major impact on H" production and consumption are the synthesis and mineralization of biomass. Any uncoupling of linkages between photosynthesis and respiration affects acidity and alkalinity in terrestrial and aquatic ecosystems (Table 15.1). 

Kreutzer K, Beir C, Bredemeier M, etal. (1998) Atmospheric deposition and soil acidification in five coniferous forest ecosystems a comparison of the control plots of the EXMAN sites. Forest Ecology and Management 101 125-142. 

Kreiser.A., N. L. Rose, A. Probst .-C. Massabuau, 1995. Relationship between lake-water acidification in the Vosges mountains and S02-NO emissions in western Europe. In Landmann, G. M. Bonneau (eds.) Forest Decline and Atmospheric Deposition Effects in the French Mountains. 

The major factors affecting the quality of soils close to mining industries are (i) change of soil pH, i.e. acidification or alkalisation, as well as (ii) accumulation of trace elements, particularly of heavy metals. Because those soils are contaminated mainly by atmospheric depositions, it is difficult to specify the... 

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