Acidification of soils

The soil itself is destroyed and so at the end of the extraction process soil is no longer present, and what is left is a mixture of highly acidic salts that must be disposed of. It is for this reason that extraction or remediation methods that depend on the acidification of soil to low pH fail and should never be undertaken [18,19],... 

The reaction results in the acidification of soil on farms and the pollution of ground water with nitrate ions. 

Acid deposition can cause acidification of soils and waters. Acidification can be defined as a reduction of the acid-neutralizing capacity of soils or waters. The acidneutralizing capacity is also known as alkalinity (AUc) and indicates the sensitivity of a water system toward acidification. It can be expressed as [9] ... 

Nitrogen fixation in excess of biological demand, however, can lead to nitrification or mineralization of organic N and ultimately to acidification of soil or surface waters (70, 71). 

The bulk of the saccharides in soil aqueous extracts are contained in the FA fraction, or the organic fraction that remains in solution on acidification of soil extracts. The introduction of XAD resin technology (see Section 1.3.2) for the fractionation of soil organic extracts has allowed some separation of saccharides from what are considered to be the true FAs. Swincer et al. (1968) deserve to be credited with that concept. They used Polyclar-AT [a (poly)vinylpyrrolidone resin used for... 

The capture of acid particles, or acid droplets, by forests is considered an important cause of acidification of soils and water courses in mountain regions (Lovett, 1984 Lovett Reiners, 1986). Field experiments on the required scale are hardly feasible. Several authors have made calculations of the wind profile within the forest, and the capture efficiency of model leaves and twigs in the canopy. Figure 6.12 shows the results of calculations by Belot (1975), Slinn (1982), and Lovett (1984). When expressed in terms of the normalised velocity of deposition v., there is little difference in Fig. 6.9 between the calculated... 

Deposition of sulfur in regions where the soils are deficient in sulfur may be considered a beneficial effect all of the other effects of sulfur air pollution are considered adverse. They include effects on human health, materials degradation, vegetation, and atmospheric visibility, and acidification of soils, watersheds and freshwaters. Limitations on the scope of this paper will greatly restrict our discussions of the details of these effects see the References 1-11 for more detailed information. 

The adverse effects of this chain of events can include direct damage to vegetation, acidification of soils, and acidification of surface waters with attendant impacts on flora and fauna. In the case of managed (agricultural) soils, soil acidification effects may be overcome through use of lime. Liming has also been used to control the pH of lakes. 

Production of N03 also leads to acidification of soil water systems. Based on the overall nitrification reaction,... 

Reuss, J.O. and Johnson, D.W., Acid Deposition and the Acidification of Soils and Waters, Ecolological Studies 59, Springer-Verlag, Berlin, 1986. 

Evidence for the toxic acidification of soil by the use of the test on soluble iron (according to Knabe and Bartels, in prep.). 

Acidification of soil combined with lack of nutrients and release of aluminium ions which act toxic to plant roots was the other line of explanation. Wieler (1905, 1933), Ulrich et al. (1979, 1983 a, b) and Drablos and Tollan (1980) can be used to support this theory, while it is more critically discussed in VDI (1983). 

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. 

Reuss J. O. and Johnson D. W. (1986) Acid Deposition and Acidification of Soils and Waters. Ecological Studies. Springer, NY, vol. 59. 

Often, the rates of fertilization in intensively managed agriculture are intended to satiate the needs of crop plants for these chemicals, so their productivity will not be limited by nutrient availability. However, excessive rates of fertilization have important environmental costs. These include the contamination of ground water with nitrate eutrophication of surface waters caused by nutrient inputs (especially phosphate) acidification of soil because of the nitrification of ammonium to nitrate large emissions of nitrous oxide and other nitrogen gases to the atmosphere, with implications for acid rain and Earth s greenhouse effect and the need to use herbicides to control the weeds that flourish under artificially nutrient-rich conditions. 

Methods to calculate critical loads from steady-state models do not take time scales for acidification and recoveiy into account. Detailed non-steady-state models have been used to estimate target loads for three watersheds in Norway and Finland (Warfvinge et al., 1992). For reviews on acidification of soils see Reuss and Johnson (1986) and Stumm and Schnoor (in press). Paces (1994) illustrates the modeling of hydrological and biogeochemical responses of a catchment area to anthropogenic inputs. 

NH3(g), NRT -III Fertilizer, animal feed lots Atmosphere, soil Waters Nitrification of NH4 (from precipitates) leads to acidification of soils Toxicity of NH3 to fish, increased chlorine demand in chlorination of drinking water... 

Selecting sensitive receptor sites In the analysis of environmental acidification from sulphur dioxide emissions, an important first step is the selection of possible locations for receptor sites which may be particularly sensitive to the deposition of acidic sulphur species. Table 1 contains the locations of arbitrary receptor sites which have been chosen to reflect the contribution from sulphur deposition to environmental damage caused by the acidification of soils, surface waters and freshwater ecosystems [14]. 

Critical loads data are usually presented as maps showing the sensitivity of receptors present at each location or as a percentile in the fi quency distribution of the receptors present within a particular grid square. Critical loads maps are available for the United Kingdom [15] for the acidification of soils and surface waters by sulphur and nitrogen compounds and for Europe [16], for the acidification of soils. 

Acid soils, with a pH of 5.5 or lower, significantly limit crop production worldwide approximately 50% of the world s potentially arable soils are acidic, and the production of staple food crops is particularly affected. Twenty percent of the worldwide production of maize and 13% of rice is on acid soils, while 60% of the acid soils in the world are in the tropics and subtropics. Thus, acid soils hmit crop yields in many developing countries, while in developed countries such as the United States, the extensive use of ammonia fertihzers causes further acidification of agricultural soils. The primary limitations of acid soils are toxic levels of aluminium and manganese, and suboptimal levels of phosphorous. Acidification of soils leads to acidification of rivers and streams, increasing the solubility of aluminium, with direct consequences on fish populations, and eventually of water supplies to the general population. 

The corrosion effect on constructions in the atmosphere due to acidification is in most areas mainly of local nature. It should be stressed, however, that acidification of soil and water can lead to increased corrosion of buried installations and of installations in water including water pipes (3, ). This is on the other hand mainly a regional problem, where the long-range transport of air pollutants plays an important role. The following subdivision may thus be used. 

The acidification of soils and waters arises predominantly through the transformation of air pollutants into acids. This leads to a decrease of the pH-value of rainwater and fog from 5.6 to 4 and below. Sulfur dioxide and nitrogen oxide and their respective acids (H2SO4 and HNO3) produce relevant crnitributions. Damage occurs to ecosystems, of which the dying of forests is the most weU-known while... 

Sulphur dioxide is formed when sulphur-containing fuels such as oil and coal are burned. In contact with humid air, it transforms to sulphuric acid, which contributes to the acidification of soil and water. 

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