What is acid deposition

In soil, processes causing acidification and the consequences of acidification are linked and feedback on each other. The N status of a site can affect certain soil transformation rates and uptake patterns which drive the acidification process, e. This process depends on the availability of ammonium ions for transformation by microbes.

Diagram modified from Binkley and Richter Acidifying deposition associated with sulphur continues to fall so that today most acidification effects are associated with nitrogen deposition. Emissions of primary pollutants contributing to acid deposition have reduced substantially since the s, mainly in response to international control measures e.

Detailed estimates of the spatial distribution of concentration and deposition of pollutants have been provided by Atmospheric Transport Models ATMs. However, this decline is not equal over the whole of the UK. Deposition in areas remote from sources has fallen by disproportionately smaller amounts than deposition close to sources, e. Reduced N is expected to dominate acid deposition chemistry in the future. Acid rain was responsible for large-scale damage to aquatic ecosystems and forests in Scandinavian countries, south eastern Canada, north eastern United States, south west Scotland Galloway , Wales and Germany.

Gaseous precursors, such as acid gases, can also cause direct damage to sensitive vegetation when they deposit in sufficiently high concentrations, e. SO 2 damage to sensitive lichens. High altitude forests are especially vulnerable as they are often surrounded by clouds and fog in which acid ions are more concentrated.

Once the pH falls below 3. Reproduction in both birds and plants appears to be sensitive to acidification, e. Eggshell thickness often declines as the availability of calcium in the diet falls in response to acid leaching Nybx et al ; Ramsay and Houston Many crustaceans cannot inhabit acidified waters due to the low availability of calcium Havas and Rosseland ; Muniz Skip to main content.

Home Pollutants Acid deposition. Acid deposition. What is it? Effects Acid rain was responsible for large-scale damage to aquatic ecosystems and forests in Scandinavian countries, south eastern Canada, north eastern United States, south west Scotland Galloway , Wales and Germany. Leaching of base cations, especially magnesium from soils, have been linked to leaf chlorosis, a common symptom on trees in some German forests in the s, where this yellowing was associated with forest decline Huettl et al Decomposition rates can be reduced in acid soils which will mean nutrient availability is compromised as mineral nutrients remain immobilised.

Acid deposition can lead to calcium being leached from conifer needles, e. The effect on food crops is minimised by the application of lime and fertilizers to replace lost nutrients and maintain a more neutral soil pH. Chemical changes leading to reduced fertility and nutrient deficiencies, e. Changes in microbial transformations e. Pollutants are generally more dispersed and of lower concentrations than local ground level pollutants.

About Lenntech. General Delivery Conditions. Privacy Policy. All rights reserved. In conjunction with other pollutants, acid deposition contributes to potentially deleterious effects on aquatic, agricultural, and forest ecosystems. Chemical changes attributed to the deposition of acidity from the atmosphere have been measured in forest ecosystems and surface waters. Concentrations of acids in lakes has been correlated with the concentrations and deposition rates of atmospheric acids, and high concentrations of acids in lakes and streams can harm fish populations.

Health effects associated with exposure to acid-containing particulates in humans are uncertain, because current studies of these effects are too limited to unambiguously discern dose—response relationships in humans.

Acid deposition from the atmosphere has been shown to accelerate the deterioration rate of exposed metals, painted finishes, and concrete or stone surfaces. Considerable damage has occurred to historic buildings and monuments due to acid rain deposition worldwide. In industrialized areas, concentrations of sulfuric and nitric acids in cloud water and precipitation are up to 50— times greater than values measured in areas that are not influenced by upwind emissions of anthropogenic pollutants.

The relative concentrations of deposited sulfur and nitrogen acids correlates with the relative sulfur and nitrogen emissions rates over a larger-scale area.

Sulfates and nitrates that are associated with acid deposition are also important contributors to tropospheric aerosol concentrations, particularly fine particulate matter in the less than 2.

In response to the Acid Precipitation Act of , a National Acid Precipitation Assessment Program NAPAP was established as a yr integrated research effort to coordinate federally funded research and assessment activities to facilitate the development of a firm scientific basis for policy decisions pertaining to acid rain.

In , NAPAP produced a quantitative assessment of the undesirable effects associated with atmospheric acidity, and also summarized our current understandings of the emissions, transport, transformation, and deposition of acids in the atmosphere. Integrated numerical modeling systems of atmospheric chemistry and transport were refined and validated during NAPAP.

In the industrialized eastern United States, the concentrations of sulfuric and nitric acid in precipitation also declined during the s. Reductions in sulfur emissions are to be achieved using a market-based trading and banking system of emissions allowances. Clean Air Act are implemented, although these NOx emissions may increase after the turn of the century.

As pollution-control technologies improve and legislative policies are implemented, air quality should improve and the concentrations of acidic substances should decline with time. However, it is important to design, implement, and maintain a system for providing an accurate measure of the influence of control measures taken in response to air pollution legislation. It is essential that research and monitoring continue to ensure compliance with existing public policy objectives and to quantitatively improve and verify our understanding of the complex processes involved in the formation and deposition of atmospheric acidity as embodied in current models of acidity in the atmosphere.

The scientific basis for current and future pollution control strategies should be continually tested and validated in the light of our evolving understandings of the physics and chemistry of atmospheric acidity, particularly in areas where there is significant uncertainty in quantifying processes affecting concentrations of acidity in the atmosphere. Further and more sophisticated analysis of alternate emissions-reduction scenarios using reliable models of atmospheric processes could assist in designing the optimum pollution-reduction strategy.

The American Meteorological Society will continue to provide a forum for ongoing collaboration between the meteorological and chemical communities to further understand atmospheric acidity. Background a. Formation of acids Sulfuric and nitric acids are produced by reactions between atmospheric oxidants and emitted sulfur and nitrogen oxides SO2, NO, and NO2 , which are by-products of fossil fuel combustion and other industrial activities.