Acid deposition ecological effects

Ecological Effects studies to determine the nature or extent of air pollution and acid deposition to ecosystems. 

In addition to climate change, the increased atmospheric concentration of C02 is likely to have wide-spread ecological effects in various environments, since C02 is a physiologically active gas, in plants as well as animals. The acidic nature of C02 will also lead to changes in the chemistry of the ocean s surface, which is in equilibrium with the atmosphere. Once the shift in the oceanic chemical balance becomes significant, it will affect ecosystems. It has been shown, for example, that doubling C02 concentration in the atmosphere will reduce the rate of calcium carbonate deposition in coral reefs by 30-40% (Langdon et al., 2000). 

The NADP analyzes the constituents important in precipitation chemistry, including those affecting rainfall acidity and those that may have ecological effects. The Netwoik measures sulfate, nitrate, hydrogen ion (measure of acidity), ammonia, chloride, and base cations (calcium, magnesium. potassium). To ensure comparability of results, laboratory analyses for all samples are conducted by the NADP s Central Analytical Lab at the Illinois State Water Survey, A new subnetwork of the NADP, the Mercury Deposition Network (MDN) measures mercury in precipitation. 

Acids and alkalis. Most freshwater lakes, streams, and ponds have a natural pH in the range of 6 to 8. Acid deposition has many harmful ecological effects when the pH of most aquatic systems falls below 6 and especially below 5. 

Since the mid-1970 s, increasing interest has emerged in the environmental consequences of the large scale deposition of atmospheric contaminants. The deposition of acid-forming constituents, sulfate and nitrate, is of particular concern for potentially adverse ecological effects. These species derive from the oxidation of sulfur dioxide (SO ) and nitrogen oxides (NO and NO ). Over most if... 

The term "acid rain" itself is not easily defined however for the purpose of this discussion, let us include under acid deposition those solids, liquids, gases, or aerosols of man-made origin. The degree of contamination, pH levels, type of anions, or ecological significance are not defined, although continued emphasis in these areas of research is important. This report will focus on the effect... 

The wet deposition of can be considered as a measure of acidity deposition rates. This is a value of the most important ecological concern regarding the acidification loading and effects on the ecosystems (see Chapter 4). 

The Hubbard Brook Experimental Forest is a long-term ecological research site established by the U.S. Department of Agriculture Forest Service in the White Mountains of New Hampshire to investigate the structure and function of forest and aquatic ecosystems, and their response to disturbance (Likens and Bormann 1995 Groffman et al. 2004). Hubbard Brook was the site where acidic deposition was first reported in North America (Likens et al. 1972). Hubbard Brook receives elevated inputs of acidic deposition and the forest ecosystem is very sensitive to these inputs. There have been long-term measurements and studies of acidic deposition and its effects on forests and streams at Hubbard Brook (Likens et al. 1996 Driscoll et al. 2001). 

There are several consistent themes that run through this volume that indicate what we still need to do. One of the highest priorities is to find a more effective way to reduce major sources of acid deposition other than sulfur dioxide. This means reducing emissions of nitrous oxides and ammonia that are derived from dispersed sources (vehicles and farming activities, respectively) and so are more difficult to control. Another theme is that we need to understand and monitor the ecological effects of acid deposition in a wide range of ecosystems, and determine if there are ways to speed their recovery from decades of acid deposition. 

Because of the type of soil and the composition of surface waters in The Netherlands, these ecosystems show a large buffering capacity to acid deposition, although ecological effects can still be demonstrated. 

National Swedish Environmental Protection Boards Ecological Effects of Acid Deposition Report and Background papers/ Stockholm Conference on Acidification of the Environment 1982. 

The development and assessment of strategies to combat acid deposition in Europe are reviewed by R. Shaw (Austria) whilst M. Chadwick and J. Kuylenstiema (U.K.) review the concept of a critical load based abatement strategy. Such a strategy based upon ecologically defined limits may be one of the most effective policy responses to acid deposition. 

However, as understanding of the basic ecological effects of acid depositions improves, it is becoming apparent that emission abatement to achieve the necessaiy deposition reductions, in some areas, will be called for that are considerably in excess of those envisaged by the existing international agreements. To take one example, it has been estimated that a reduction of approximately 75 per cent in S deposition (from approximately 80 keq km yr to approximately 20 keq km ... 

Bache, B.W. (1983). The implications of rock weathering for acid neutredlzatlon. In Ecological Effects of Add Deposition. Report PM 1636, pp. 175-87. National Swedish Environment Protection Board, Solna. 

Peatlands, or organic soils, are water-logged deposits of partly decomposed plant debris. Ecological variation and diversity in extent of domination by water influence the degree of humification in peatlands. Humification in peatlands does not coincide with decomposition as well as in mineral soils. Measurement and extraction of peatland humus are hampered by the presence of large proportions of unhumified material. Therefore, most studies on the characterization of peatland humus have focused on humic acids, or on pyrophosphate extracts of the organic soils. Pyrophosphate extracts contain less unhumified materials than alkali extracts but are far less effective in extracting the peat humic substances. 

Pennanen, ., Perkiomaki, J., Kiikkila, 0.,Vanhala, P., Neuvonen, S. and Fritze, H. (1998) Prolonged, simulated acid rain and heavy metal deposition separated and combined effects on forest soil microbial community structure. FFMS Microbial Ecology 2 7, 291 -300. 

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