Mean Annual pH Research Articles

Acid Precipitation – An International Environmental Problem

The acidification is no longer confined to Scandinavia, it is a trans-World problem. The concept of acidification is bound up with the discharge into the atmosphere of sulphur dioxide, nitrogen oxides, and metals and other micro-pollutants - and the subsequent effects of these substances on the environment. The bulk of man-made emissions occurs over industrialized regions covering less than 5% of the earth's surface. In these regions, man-made emissions exceed the natural emissions by a factor of five to twenty. In the 1950's a sharp rise in oil combustion increased the SO2 emissions in Europe to about 25 million tonnes of sulphur per year by 1970. European emissions of NO have increased from low values 100 years ago to the present value of about 6 million tonnes of nitrogen per year. Similar emission trends of SO2 and NOx have taken place in North America. Sulphur dioxide emissions in Europeare predicted to remain about the same as present-day emission through 1990. Further trends in emission will depend critically on the energy policies of each country and the entire region. Strong acids have decreased the mean annual pH of precipitation in much of Northwestern Europe and large areas of North America to between 4 and 4.5. The sources and environmental consequences of acid deposition are often separated by hundreds, even thousands, of kilometres. Its impacts on aquatic systems in more susceptible areas of Europe and North America are clearly documented today. Tomorrow, the emission source areas exposed to the heaviest depositions will be facing serious direct and indirect effects on natural ecosystems, materials and possibly even human health. Further, metal toxicity in soils, surface waters and groundwaters with consequences for terrestrial and aquatic life will most likely develop in both heavily polluted and sensitive areas.

Evidence of Acidification of Some Nova Scotian Rivers and Its Impact on Atlantic Salmon, Salmo solar

River pH's in Nova Scotia are closely related to geology, and seasonal pH variation is well correlated with river discharge rates. In the geologically sensitive areas (granite and metamorphic rocks), river pH's have fallen significantly over the past 27 yr at an apparent average rate of 0.017 pH units/year. Concomitant with this decrease are a decline in [Formula: see text] concentrations and increases in Al+++ and [Formula: see text]. On average, 73% of the increase in acid is attributable to increased [Formula: see text]. Changes in Na+, K+, Ca++, and Mg++ concentrations were not significant. In rivers presently at mean annual pH's < 4.7, the Atlantic salmon (Salmo salar) runs have disappeared and are presumed extinct. Rivers in the pH range 4.7–5.0 show a decline in salmon angling returns of 2.8%/yr, beginning about 1954, and low densities of juvenile salmon. Rivers presently of pH > 5.0 generally have normal juvenile densities and show no significant trend in angling returns.

Atmospheric Sulfur Deposition, Neutralization, and Ion Leaching in Two Deciduous Forest Ecosystems

AbstractIn the 1981 water year, bulk precipitation was primarily a solution of dilute H2SO4, and SO42‐ was the dominant anion in tbroughfall and soil leachates in two eastern Tennessee deciduous forests. Ecosystem inputs of SO42‐, which included dry deposition of forest canopies, may have been up to 40% greater than input estimates based on atmospheric deposition sampling in open areas. Volume‐weighted mean annual pH of bulk precipitation was 4.3; of throughfall 4.8; and of leachates from O2, A1, and B21 soil horizons about 6.0. At both sites, strong acids in precipitation were largely neutralized prior to rainwater's infiltration into mineral soil.Base cations that exchanged with H+ (hydrogen ions) in acid precipitation were almost entirely supplied by forest canopies and litter layers, and did not come directly from exchangeable mineral soil pools. Annual fluxes of HCO3− alkalinity from B21 horizons, about 0.42 and 0.51 kmol (−) ha−1 (keq ha−1) at the two sites, indicated that the natural H+ input from the partial ionization of H2CO3 was of similar magnitude to H+ input in bulk precipitation in 1981 [0.60 kmol(+)ha−1]. However, even in these infertile soils with low cation exchange capacities (CEC) [<7.2 cmol (NH4+) kg−1 (meq/100 g) in surface 50‐ or 80‐cm soil], exchangeable bases were more than two orders of magnitude greater than annual H+ input in bulk precipitation, and represented a substantial reserve for base cations in canopies and litter layers that exchanged with H+ in acid rain. Furthermore, inputs of H+ from acid precipitation were equal to about 0.4% of the base cations that are biologically cycling and immediately available in these ecosystems. Although poorly quantified, mineral weathering and deep rooting will supply, over time, substantial amounts of additional base cations for biologic cycling. Both soils are base‐poor Udults and classified as sensitive to acid rain, but the deposition, cycling, and soil data presented in this report indicate that leaching remains a process affecting cation reserves and soil development only over the very long term.

Ecology of streams draining forested and non-forested catchments in an area of central Scotland subject to acid precipitation

A study of 12 streams draining forested and non-forested catchments was made in an area of central Scotland where slow-weathering bedrock was predominantly quartzite, schists and slates. Sitka spruce (Picea sitchensis Carriere) was the most common tree species. Precipitation in the area had an annual mean pH in the range 4.3–4.5. Streams within the planted zone were always more acid than those outside and had higher concentrations of aluminium and manganese. With one exception, trout were absent from streams within long-established forests and planted salmon eggs (Salmo salar L.) died within a few weeks. A high proportion of such eggs survived in streams outside the forest. Siphlonurus lacustris Eaton was the only mayfly nymph found in the most acid streams in summer collections. In winter samples, mayfly nymphs, Heptagenia lateralis (Curtis) were found in only one forest stream but several species were present in the non-forested catchments. It is suggested that spruce forests can effectively collect acid pollutants which are subsequently washed out, thus accelerating the acidification of the soil. Streams therefore become increasingly acid as the neutralisation capacities of their catchments decrease.

Seasonal mass balance of major ions in three small watersheds in a maritime environment

Three watersheds (16.4, 544, and 83 ha) at distances of 0.5, 20, and 40 km from the Atlantic coast have been monitored for major ion chemistry of precipitation input and streamflow from May 1977 to November 1978. More than 200 precipitation and stramflow samples were analyzed for Na, K, Ca, Mg, chloride and sulphate, as well as pH, conductivity, alkalinity, and compared to similar studies at Hubbard Brook, New Hampshire, U.S.A., and Kejimkujik National Park, Nova Scotia. Major ion chemistry reflects proximity to Atlantic and Bay of Fundy coastal sources of marine aerosols. Evidence is presented implying biological reduction of H + and S04 to H2S during summer months for two consecutive growing seasons. Weighted mean annual pH values of precipitation for the three watersheds in Nova Scotia range from 4.11 to 4.63. More than 50% of the H + in precipitation is retained in the watersheds (with the exception of the ombrotrophic Fink Cove ecosystem), principally at the expense of basic cations being leached from the watersheds. Acidic deposition of Nova Scotian precipitation is predominantly as sulphuric acid, in contrast to ammonium sulphate, characteristic of continental precipitation.

The Acidity of Scandinavian Precipitation

Data on the pH of the total monthly precipitation at stations of a Swedish network for sampling and chemical analysis of precipitation and atmospheric aerosols during the year July 1953—June 1954 are presented and discussed, together with the pH data from the first two months of operation of a larger pan-Scandinavian net. It is found that well-defined regions of acidity and alkalinity relative to the pH of water in equilibrium with atmospheric carbon dioxide exist, and that these regions persist to such an extent that the monthly deviations from the pattern of the annual mean pH at each station are relatively small. The mean pH of the entire network shows a distinct annual cycle, with greatest acidity in winter and greatest alkalinity in late spring. Coastal stations unaffected by local pollution show persistently high acidity, while inland northern stations show equally persistent alkalinity. Some possible reasons for the observed distributions are considered. DOI: 10.1111/j.2153-3490.1955.tb01159.x

The Acidity of Scandinavian Precipitation

Data on the pH of the total monthly precipitation at stations of a Swedish network for sampling and chemical analysis of precipitation and atmospheric aerosols during the year July 1953—June 1954 are presented and discussed, together with the pH data from the first two months of operation of a larger pan-Scandinavian net. It is found that well-defined regions of acidity and alkalinity relative to the pH of water in equilibrium with atmospheric carbon dioxide exist, and that these regions persist to such an extent that the monthly deviations from the pattern of the annual mean pH at each station are relatively small. The mean pH of the entire network shows a distinct annual cycle, with greatest acidity in winter and greatest alkalinity in late spring. Coastal stations unaffected by local pollution show persistently high acidity, while inland northern stations show equally persistent alkalinity. Some possible reasons for the observed distributions are considered.