Acidification means that soil or water bodies are losing their capacity to neutralize (buffer) acidic deposition. Acidifying compounds are deposited with rain as wet deposition or with particles and gases as dry deposition.
of surface waters is a global problem. Oxides of sulfur are the major acidifying compounds in the Arctic. They are formed when fossil fuels burn and when sulfide ores are smelted. The Pechenganikel-combine located in the Norwegian and Russian border area is one of the largest sources of aerial sulfuric acid oxide pollution in the North (AMAP). These oxides subsequently react in the atmosphere to produce acids that are dissolved in precipitation.
Acidification represents a serious threat to many plants and animals, particularly in sensitive aquatic ecosystems. One of the most harmful impacts of acidification is that in acidic conditions toxic aluminum and heavy metal ions are more easily leached from the soil and absorbed by living organisms. This leads to irregularities of reproduction processes, drop in biodiversity, disappearance of acid sensitive species, domination of resistant ones etc. On the whole the resistance of ecosystems is decreasing.
Water
buffering capacity
Buffering capacity
Acid buffering capacity (capacity to neutralize acids) of a water body is determined with alkalinity measurement. In the process acid is added to the sample in small doses and the effect is measured as pH change. The buffering capacity is determined as how much acid can be added to the sample before the pH decreases to a certain value.
Alkalinity of 0,05 mmol/l is the limit value for a risk of acidification of a water body. The buffering capacity is very weak if the alkalinity value is lower.
of water is affected by the composition of the soil and bedrock in the catchment area. In many of the project areas the substrata are made up of alkaline minerals and the catchment systems effectively stand the existing acid load. Acidification of the surface water in these areas take place in the form of short-term pH drop (during melting of snow and heavy rains), changes of the ratio between the main ions in the chemical composition of water and decrease of the general buffering capacity of the surface water.
At the same time there are regions where catchment areas are made up by acidic geologic layers (mainly granite and gneiss) and their ecosystems’ resistance to
acidic deposition
Acid rain
Acid rain is formed mainly from sulfur and nitrogen oxides (SO2 and NOx) and ammonium (NH3) that have been released into air.
Surfur and nitroxen oxides form sulfuric acid and nitric acid directly as they react with water in the air or in the moist soil. Ammonium, in itself, is not an acidic compound, but it is easily oxidized into nitrites (NO2) or nitrates (NO3) and has an acidifying effect that way.
are very low. These are primarily coastal and elevated regions. Vätsäri, Jarfjord and Southern Varanger areas are especially sensitive to acidification. In addition to acid bedrock, the soil thinness in the watershed also increases susceptibility to acidification. Jarfjord in particular has a number of areas with almost no soil cover at all.
Close to the emissions sources in Pechenga hardly any acidification impact has been observed. The reason for this is probably due to the bedrock of the area and the alkalinity of dust emissions. The alkaline ash fallout from the air to the ground neutralizes the impact of acidic fallout.
