Acid-sensitive soils

Figure 5.12 depicts a hypothetical soil pH-buffer capacity curve. It is clear from this relationship that the soils most likely to reach very low pH and toxic Al solubilities even with modest inputs of acidity are those with low inherent buffer capacities (arising from the lack of carbonates, clay, or humus content) or those whose buffers have already been expended in neutralizing past acid inputs. These are termed acid-sensitive soils, and are typically acid soils with little clay and humus. They are the most likely soils to reach extremely low pH (<4) on exposure to acid rain or other sources of acidity. Since primary and secondary aluminosilicate mineral dissolution is very pH sensitive, phytotoxic concentrations of soluble AP" are increasingly likely as the pH lowers. 

Nitrogen Deposition in Nutrient-Deficient and Acid-Sensitive Soils... 

Greatest changes in aerial distribution and increase of concentration will occur in the Asian region (see Fig. 4). Regions with acid-sensitive soils and high N-depositions are concentrated to China and Southeast Asia, Western and Central Europe, and... 

Acid deposition is of greatest concern wherever there are large amounts ol lossil fuel combustion upwind of an area. Eastern North America, large areas of Europe, and eastern Asia all receive acidic deposition. Acidic deposition is especially a concern when poorly buffered soils, with little acid-neutralizing capacity, are impacted. In North America, large areas of eastern Canada, the Adirondack Mountains of upstate New York, and sections of New England all are considered acid sensitive areas, where resistant bedrocks and thin soils prevent significant neutralization of acidity. 

Class 5 (the least sensitive) soil include Kashtanozem, Brown soil and Sierozem soil zones in the Plateau of Inner Mongolia and the Loess Plateau, Desert soil zones in He-xi-zou-lang and the Talimu River Basin, Subalpine Steppe soil, Alpine Steppe soil and Alpine Desert soil in the Plateau of Tibet. These kinds of soils, belonging to the soil class of Xerosol or Alpine soil, consist of easy weathering minerals such as carbonate. They show alkaline reactions, with weak leaching and sparse vegetation. Those kinds of soils are insensitive to acid deposition. 

In one study of the persistence of disodium methane arsenic acid in soil, the initial and residual phytotoxicity of disodium methane arsenic acid in soil to cotton was measured over a broad range of concentrations in three soils. Toxicity decreased with time, particularly during the first 16 weeks after soil incorporation. Growth of cotton planted immediately after incorporation of disodium methane arsenic acid in Bosket silt loam was reduced significantly by concentrations of 50-80mg kg-1 in soil. In the same soils, other plants were shown to have different degrees of susceptibility to disodium methane arsenic acid concentrations. Rice was extremely sensitive to soil concentrations of 5ppm, while corn, cotton and wheat were little affected. 

Choose alkaline formulations for products designed to remove oils and organic soils or to treat acid-sensitive surfaces such as marble. 

There also is a concern about the impact of arid rain on forest soils. There is good reason to believe that long-term changes in the chemistry of some sensitive soils may have already occurred as a result of acid ram. As acid lain moves through the soils, it can strip away vital plant nutrients through chemical reactions, thus posing a potential threat to future forest productivity,... 

The systemic morpholine fungicide Corbel with fenpropimorph as its active substance is frequently applied to cereal cropping. It is rapidly metabolized in soil to fenpropimorphic acid. For the assay of fenpropimorphic acid in soil, GC-MS coupling109 has been proposed. The GC technique was used to assure the best separation for the fenpropimorphic acid from the complex soil matrix. The MS technique is very sensitive and assures the best reliability of the analytical information. The same reliability is also achieved when the HPLC-MS tandem system is used for sulfonylurea herbicide assay in soil.110... 

In relation to add input from 1980 to 1990, the buffering capacity of 1.8 Mio km or 15% of the acid-sensitive forest soils tends to become saturated in the next 25-100 years. Under the assumptions of the IS92a scenario, this share more than doubles and increases to 4.0 Mio km or 34% between 2040 and 2050. For 1980-1990, the mean buffering capacity of these sols based on our methodology is supposed to last for 65 years more. Under changed inputs this period tends to decrease for 2040-2050 to... 

FIGURE 3 Distribution of exceeded forest soils buffering capacity, (a) today (1980-1990) and (b) (2040-2050). Red areas show forest soils with an exceeded buffering capacity while the green areas show the not-affected areas of acid sensitive and nutrient deficient forest soils. See also color insert. 

Until recently, understanding of the effects of acidic deposition on soils was limited. However, current research has shown that acidic deposition has chemically altered forest soils with serious consequences for acid-sensitive ecosystems. Soils compromised by acidic deposition lose their ability to neutralize continuing inputs of strong acids, provide poorer growing conditions for plants, and extend the time needed for ecosystems to recover from acidic deposition. Acidic deposition has altered and continues to alter base-poor forest soils in three important ways. Acidic deposition depletes available calcium and other nutrient cations (e.g., magnesium, potassium) from soil facilitates the mobilization of dissolved inorganic aluminum into soil water and increases the accumulation of sulfur and nitrogen in soil. 

MacAvoy, S.E. and Bulger, A.J. (1995). Survival of brook trout (Salvelinus fonti-nalis) embryos and fry in streams of different acid sensitivity in Shenandoah National Park, USA. Water Air and Soil Pollution, 85, 439—444. 

Because Pb has to be transferred from the solid phase to the aqueous phase before it can be taken up by plants and aquatic organisms, the concentration of Pb in natural waters can be a sensitive indicator of the potential for Pb to become biologically available . To estimate how much of this Pb might be transferred to the aqueous phase, solutions collected from ten Swiss forest soils were measured for concentrations of total dissolved Pb (Peter Blaser, unpublished data) and found to range from < 1 to >60 p-g/L. Five of the profiles were acidic (pH 4-5) and these contained 20-60 pg/L Pb in the aqueous phase of the surface layers. These layers, however, are the most critical ecologically, as they represent the biologically active zone of acidic forest soils this is also the zone which has been most impacted by anthropogenic Pb. 

This class of compounds is covered by a large number of application and formulation patents. Such surfactants are claimed to have superior cleaning efficiency with respect to oily/greasy and enzyme-sensitive soils. Glucamides are polyhydroxy fatty acid amides, having the typical Structure D shown in Figure 14.20. 

The focus of the research just described utilizing the cucumber-nutrient culture and the cucumber-microbe-soil model systems was to identify and characterize what happens to phenolic acids once they enter the soil environment and how in turn this may influence the behavior and processes of phenolic acid-sensitive seedlings. The research was thus hypothetical, theoretical, and process oriented and not designed to answer speciflc questions related to actual field observations. When choosing any model system for study one hopes and assumes that the model system chosen is not unique but that the relationships and processes observed for the system chosen are representative of a broader array of other systems and hopefully relevant to field systems. 

Boron. The principal materials used are borax [1303-96-4] sodium pentaborate, sodium tetraborate, partially dehydrated borates, boric acid [10043-35-3] and boron frits. Soil appHcation rates of boron for vegetable crops and alfalfa are usually in the range of 0.5—3 kg/hm. Lower rates are used for more sensitive crops. Both soil and foHar appHcation are practiced but soil appHcations remain effective longer. Boron toxicity is not often observed in field appHcations (see Boron compounds). 

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