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Acid rain is rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH).Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but acid rain has a pH level lower than this and ranges from 4–5 on average.
Diagram depicting the sources and cycles of acid rain precipitation. Freshwater acidification occurs when acidic inputs enter a body of fresh water through the weathering of rocks, invasion of acidifying gas (e.g. carbon dioxide), or by the reduction of acid anions, like sulfate and nitrate within a lake, pond, or reservoir. [1]
Acid-neutralizing capacity or ANC in short is a measure for the overall buffering capacity against acidification of a solution, e.g. surface water or soil water.. ANC is defined as the difference between cations of strong bases and anions of strong acids (see below), or dynamically as the amount of acid needed to change the pH value from the sample's value to a chosen different value. [1]
Upon exposure to oxygen (O 2) and water (H 2 O), metal sulfides undergo oxidation to produce metal-rich acidic effluent. If the pH is low enough to overcome the natural buffering capacity of the surrounding rocks (‘calcium carbonate equivalent’ or ‘acid neutralising capacity’), the surrounding area may become acidic, as well as contaminated with high levels of heavy metals.
In the process of oxidizing the organic substances found in the water sample, potassium dichromate is reduced (since in all redox reactions, one reagent is oxidized and the other is reduced), forming Cr 3+. The amount of Cr 3+ is determined after oxidization is complete and is used as an indirect measure of the organic contents of the water sample.
This compound causes rainfall pH to be around 5.0–5.5. When rainfall has a lower pH than natural levels, it can cause rapid acidification of soil. Sulfur dioxide and nitrogen oxides are precursors of stronger acids that can lead to acid rain production when they react with water in the atmosphere
Acid Base Accounting (ABA), namely, the practice of quantifying sources of acidity and alkalinity, is a critical aspect of managing acid sulfate soils. For example, ABA is used to calculate the amount of neutralising agent (e.g., lime) required to neutralise stockpiled sulfidic material generated from excavation or dredging activities.
The effectiveness of the oxidation is contingent on the site lithology, the residence time of the oxidant, the amount of oxidant used, the presence of oxidizing materials other than the targeted contaminant, the degree of effective contact between the oxidant and the contaminant(s), and the kinetics of the oxidation reaction between the oxidant ...