Acidification, buffer capacity

Acid rain primarily affects sensitive bodies of water, that is, those that rest atop soil with a limited ability to neutralize acidic compounds (called buffering capacity ). Many lakes and streams examined in a National Surface Water Survey (NSWS) suffer from chronic acidity, a condition m which water lias a constant low (acidic) pH level. The survey investigated tlie effects of acidic deposition in over 1,000 lakes larger than 10 acres and in thousands of miles of streams believed to be sensitive to acidification. Of the lakes and streams surveyed in the NSWS, arid rain has been determined to cause acidity in 75 percent of the acidic lakes and about 50 percent of tlie acidic streams. Several regions in the U.S. were identified as containing many of the surface waters sensitive to acidification. They include, but are not limited to, the Adirondacks. the mid-Appalachian highlands, the upper Midwest, and the high elevation West. 

Microbial-driven mineralization of organic matter can also contribute to acidification of the rhizosphere (Badalucco and Nannipieri, 2007). It should be noted that pH variations in the rhizosphere depend also on the soil s buffering capacity... 

Acidification Effects. Deposition of acidifying substances upon the landscape can have several different types of adverse effects, depending on the buffering capacity of the ecosystem. These acidifying substances include both acid precipitation and dry deposition of S02 and sulfate particles. In non-arid regions,... 

Polyethyleneimine (PEI) is one of the most extensively examined polymers because it has a relatively high transfection efficiency. PEI is believed to enter the cell via an endocytotic route and to possess a buffering capacity and the ability to swell when protonated.52,53 Therefore, at low pH values, it is believed that PEI prevents acidification of the endosome and induces a large inflow of ions and water, subsequently leading to rupture of the endosomal or lysosomal membrane so that the PEI-plasmid DNA complex is delivered to the cytoplasmic space.54,55 PEI is also reported to undergo nuclear localization while retaining an ordered structure once endocytosed.53 However, the transfection efficiency of PEI depends on its molecular weight and structure.56-58... 

The ability of forests to withstand acid rain depends on the capacity of the soil to neutralize the inputting acidity. This is largely determined by local geology, in much the same way that it affects the acidification of lakes. Acidification is mainly a problem in areas where the underlying rocks provide poor buffering capacity. Rocks such as granite offer little buffering protection. Chalk and limestone neutralize added acid, and so soils, lakes and streams in limestone areas are fairly insensitive to acidic precipitation. 

With the pH-stat-technique (Obermann and Cremer 1992), a combined determination of metal releases and buffer capacity can be made at different time intervals the sum curve of acid consumption provides information on the potential changes of the matrix composition during acidification. 

We can conclude from the above discussion that rain of pH higher than 5.6 has not been influenced by humans, or if it has, it has sufficient buffering capacity so that acidification... 

Standard acidification and deacidification methods are aimed solely at changing total acidity levels, with no concern for the impact on pH and even less for the buffer capacity of the wine, with all the unfortunate consequences this may have on flavor and aging potential. 

Applying Buffer Capacity to the Acidification and Deacidification of Wine... 

Examination of the results shows that adding 100 g/hl to a cuvee must or wine only resulted in 10-15% acidification, corresponding to an increase in total acidity of approximately 0.5 g/1 (H2SO4). Evaluating the acidification rate from the buffer capacity gave a similar result. The operation was even less effective when there was a high potassium level, and potassium bitartrate precipitated out when the tartaric acid was added. 

Lead (Pb) Some really low remediation percentages (0%-10%) were obtained in studies of calcareous soil (Maini et al, 2000) and tailing soil (Kim and Kim, 2001), whereas around 50% removal was obtained in studies of different sludges (Khan and Alam, 1994 Kim et al, 2005). Highly successful removals (92%-98%) were obtained in full scale, as well as in a study of noncalcareous soil (Clarke et al, 1996 Ottosen et al, 2005). Apart from confirming the fact that acidification, and thus buffer capacity, is a determinant of remediation success, it is difficult to deduct any conclusions from the results since Clarke et al (1996) give no detailed information about remediation conditions. However, it seems that long remediation times are necessary for successful removal (Ottosen et al, 2005). 

Copper (Cu) Very good removal percentages of up to 99%. Cu was obtained in unenhanced systems (Table 4.1) however, the duration of the successful experiments was very long. Enhancement in the case of copper is mainly focused on a faster acidification of the soil, and thus remediation. Citric acid showed good results. The acid demand for soils with high buffer capacity is high, and in such soils the enhancement may be the addition of a complex binder for Cu so the remediation can occur at neutral to alkaline pH. An example of this is ammonia. 

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