page_title: Freshwater acidification
section_title: Buffering Capacity
hierarchical_section_title: Freshwater acidification / Causes / Buffering Capacity
caption_attribution_description: English: Map of w:Atlantic Canada and nearby areas created from public domain data at Natural Earth. Albert Equal Area projection on longitude 60W.
context_page_description: Freshwater becomes acidic when acid inputs surpass the quantity of bases produced in the reservoir through weathering of rocks, or by the reduction of acid anions, like sulfate and nitrate within the lake. The main reason for freshwater acidification is atmospheric depositions and soil leaching of SOₓ and NOx. In an acid-sensitive ecosystem, which includes slow-weathering bedrock and depleted base cation pools, SOₓ and NOₓ from runoff will be accompanied by acidifying hydrogen ions and inorganic aluminum, which can be toxic to marine organisms. Acid rain is also a contributor to freshwater acidification, however acid rain is formed when SOₓ and NOₓ react with water, oxygen and oxidants within the clouds. In addition to SOₓ and NOx, the buffering capacity of soils and bedrocks within the freshwater ecosystem can contribute to the acidity of the water. Each freshwater reservoir has a capacity to buffer acids. However, with excess input of acids into the reservoir, the buffering capacity will essentially “run out” and the water will eventually become more acidic. Increase in atmospheric CO₂ affects freshwater acidity very similarly to the way rising CO₂ affects ocean ecosystems.
context_section_description: In addition to SOₓ and NOₓ, low buffering capacities of ecosystems can also lead to freshwater acidity. For example, Atlantic Canada has the lowest acid deposition rates in Eastern North America, with the most acidic waters on the continent. This is due to the low buffering of the regional bedrock and the addition of natural organic acids produced by close by wetlands. Specifically, in Southwestern and Eastern Nova Scotia, there is a combination of high organic acidity, poor buffering, and high acid deposition to produce a very low surface water pH and acid neutralization capacity (ANC) values. In most of the Atlantic region, granite and shale bedrock are found, which contain very little buffering material. Soil formed from low-buffering materials and the waters that drain from them are, therefore, susceptible to acidification, even under low acid deposition.
caption: A map depicting Atlantic Canada.
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