Acid neutralizing capacity, ANC

Soil solution equilibrium. Soil solution equilibriumis based on the quantification of acid-neutralizing capacity, ANC, which has been defined as ... 

Acid neutralizing capacity (ANC) - ANC is a consideration in selecting an antacid. It varies for commercial antacid preparations and is expressed as mEq/mL. Milliequivalents of ANC is defined by the mEq of hydrochloride required to keep an antacid suspension at pH 3.5 for 10 minutes in vitro. An antacid must neutralize at least 5 mEq/dose. Also, any ingredient must contribute at least 25% of the total ANC of a given product to be considered an antacid. 

Antacids are basic compounds that neutralise acid in gastric lumen, have no effect on gastric acid secretion. They are quantitatively compared in terms of their acid neutralizing capacity (ANC), which is defined as the quantity of 1 N HCl (in MEq) that can be brought to pH 3.5 in 15 minutes by a unit dose of antacid preparation. An ideal antacid should be potent in neutralizing acid, inexpensive, not absorbed from GIT and contain negligible amounts of sodium, should be sufficiently palatable to be readily tolerated with repeated dosage and should be free of side effects. An ideal antacid is yet to be developed. 

Figure 8. Effect of baseline acid-neutralizing capacity (ANC) and episodic conditions in Adirondack lakes, a, Relationship between baseline ANC and the springtime depression in ANC (baseline ANC—minimum ANC) for 11 lakes sampled in 1986 and 1987. b, The relative contributions of base cations (Cb) and nitrate (N03 ) to the springtime ANC depressions in Adirondack lakes. Lakes at intermediate ANC values undergo the largest springtime depressions in ANC. Lakes with lower baseline ANC are affected more by N03 pulses, and lakes with higher baseline ANC are affected more by base-cation dilution. Solid lines represent best-fit relationships. (Redrawn with permission from reference 126. Copyright 1990 American Geophysical Union.)...

Figure 10. Temporal patterns in lake-water N03, acid-neutralizing capacity (ANC), base cations (Ca + + Mg2+ + Na+ + K+), S042, and inorganic monomeric aluminum (Al ) at Constable Pond, a long-term monitoring site in the Adirondack Mountains. Trend lines are shown for variables with significant trends (p < 0.10 in seasonal Kendall tau test). Seasonal pattern is typical of Adirondack lakes, with seasonal minima in ANC coincident with seasonal maxima in NOf and Ah. Many Adirondack lakes exhibited upward trends in N03 in the 1980s the primary increase was in episodic N03 concentrations.

One term now used interchangeably with acid neutralizing capacity (ANC) of natural waters is alkalinity (Aik)—defined as the concentration of negative charge that will react with H+. 

Scientific objectives. The three most common are determination of the available release potential (this notion aims to evaluate the total elementary content of pollutant available for leaching), study of solubilities at equilibrium (these tests which are conducted on crushed waste are carried out either at controlled pH or by addition of given quantities of acid when measuring the acid neutralization capacity, ANC), and assessment of the release dynamics (these tests are carried out on monolithic samples over long periods from one to three months or more) [33-36]. 

Acidity of waters is typically expressed by the pH (= — log[H ]) as an intensity factor and by acid-neutralizing capacity (ANC), or alkalinity (ALK), as a capacity factor. The latter is commonly expressed in peqL An acidic water has a pH below 7.0. Many papers suggest that acidic water should be defined as a water that... 

The general sequence of the calculations in PROFILE is given in Fig. 7.12. The acid neutralization capacity (ANC) of soil moisture (the alkalinity minus the acidity) and the soil pH are com-... 

Alkalinity is a measure of the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate. It is closely related to the acid neutralizing capacity (ANC) of a solution, and ANC is often incorrectly used to refer to alkalinity. Alkalinity is equal to the stoichiometric sum of the concentrations of HCO3 and COs —that is, ([HCOj]-t2[COi ]) in mmol/L in most solutions. It is determined by titrating with acid down to a pH of about 4.5. 

These experimental test procedures, together with calculations of the acid-producing potential (APP) and acid-neutralizing capacity (ANC), are characteristic tools for the medium- and long-term prediction of metal release from all types of waste materials. Application of such prognostic tool will become even more important, when the rate of waste material utilization/ recycling is enhanced (in Germany up to 100% by the year 2020), and will intensify the contact of the secondary products with the soil environment. 

S deposition (Driscoll et al. 1995 Dillon et al. 1997 Dillon and Evans 2001 Lofgren et al. 2001). Furthermore, other measures of chemical recovery, particularly increases in lake pH and acid neutralizing capacity (ANC), have provided conflicting evidence. In a few cases (Webster and Brezonik 1995 Stoddard et al. 1998), they have indicated limited evidence of chemical recovery, while in many others (Clair et al. 1995 Houle et al. 1996 Dillon et al. 1997), there has been little or no change in these parameters despite declining S deposition. 

ARD can also produce sulfuric acid at a slower rate, so that the acid neutralizing capacity (ANC) of the aquifer can neutralize the produced acid. In such cases, the total dissolved solids (TDS) concentration of the water can be increased from the dissolution of minerals from the acid-neutralization reaction with the minerals. 

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