Information measures for acid precipitation networks

The need to estimate the amount and pattern of air pollutants has resulted in the establishment of acid precipitation monitoring networks throughout northeastern North America. Information content measures are developed to examine the impact of station addition or removal on the ability of a network to estimate the deposition field. Also examined is the utility of standard precipitation network information to improve the acidic deposition estimates. The techniques are demonstrated through the estimation of the annual sulphate deposition field in southern Ontario for the years 1981 through 1984.     

Measurement of acid precipitation in Norway

Since January 1972, chemical analysis of daily precipitation samples from about 20 background stations in Norway has been carried out on a routine basis. Air monitoring is carried out at six stations. The chemical analysis program is: sulphate, pH and acidity in precipitation, sulphates and SO₂ in air. In addition, more detailed chemical analysis of aerosol and precipitation has been carried out at selected stations. Some results for the measurement period 1972 to 1974 are presented. Comparison of air and precipitation concentrations of S compounds show that the precipitation scavenging efficiency is very high under the conditions in southern Norway.     

On the origin and the trend of acid precipitation in China

The acidity of the precipitation in China as well as the area affected by acidic raimfalls have increased in the years, along with the rapid economic growth in china. Field observations indicate that acid precipitation often occur are the southern par, of china, although the emissiors of the precursors are stronger in the North.In this paper,we explain the geographical distribution of acid precipitation in china, based on the content alkaline ions in soil, soil acidity, atmospheric particulate concentration, aerosol buffering capacity and atmospheric dispersion. It is further anticipated that continuous increasing of sulfur emissions in the North will eventually result in acid rain in the northern part of China. On the basis of the projection of SO₂ and No emissions,it is argued that the problem of acid precipitation may get worse towars the year 2020,if expenditure on emission control maintains at current level.     

Chemical composition of acid precipitation in Central Texas

Studies were undertaken to determine factors affecting composition of acidic precipitation formation in the Austin area of Central Texas. The study was initiated to determine background levels of acid and alkalinity producing constitutents in an area with elevated natural dust levels from nearby limestone rock formations. Results showed normal rainfall pH values of 6.5 to 6.6 in the area, with extreme variations from 5.8 to 7.3. Significant Ca levels of 1 to 4 mg 1^?1 were observed from probably natural origin which appeared to have a buffering effect on acidity. Significant sulfate and nitrate ion concentrations occurred during the early stages of rainfall where rainfall pH was dependent on calcium-sulfate ratio.     

Impacts of acid precipitation on coniferous forest ecosystems

This paper summarizes the results from current studies in Norway. One main approach is the application of artificial acid ‘rain’ and of lime to field plots and lysimeters. Application during two growth seasons of 50 mm mo^?1 of ‘rain water’ of pH 3 to a podzol soil increased the acidity of the humus and decreased the base saturation. The reduction in base saturation was mainly due to leaching of Ca and Mg. Laboratory experiments revealed that decomposition of pine needles was not affected by any acid ‘rain’ treatment of the field plots. Liming slightly retarded the decomposition. No nitrification occurred in unlimed soils (pH 4.4-4.1). Liming increased nitrification. The soil enchytraeid (Ohgochaeta) fauna was not much affected by the acidification. Germination of spruce seeds in acidified mineral soil was negatively affected when soil pH was 4.0 or lower. Seedling establishment was even more sensitive to increasing soil acidity. Analysis of throughfall and stemflow water in southernmost Norway reveals that the total deposition of H₂SO₄ beneath spruce and pine is approximately two times the deposition in open terrain. A large part of this increase is probably due to dry deposition. Increased acidity of the rain seems to increase the leaching of cations from the tree crowns. Tree-ring analysis of spruce (Picea abies (L.) Karst.) and pine (Pinus sylvestris L.) has been based on comparisons between regions differently stressed by acid precipitation and also between sites presumed to differ in sensitivity to acidification. No effect that can be related to acid precipitation has yet been detected on diameter growth.     

Hydrogen ion speciation in the acid precipitation of the northeastern United States

The acidity of precipitation in rural, forested areas of the northeastern United States is dominated by the strong mineral acids: H₂SO₄ and HN0₃. Weak acids have a negligible effect on the measured acidity (pH) of precipitation. These conclusions are based on total acidity titrations and detailed analysis of organic and inorganic components in precipitation.     

Fractional precipitation of humic acid from colored natural waters

Humic acid (HA) is usually defined in the soil and aquatic sciences as that fraction of base-soluble soil organic matter or dissolved organic matter (DOM) which is insoluble in acid. Stepwise titration of bulk DOM from four samples of bog pore water and stream water were undertaken to study the fractional precipitation of HA. Three independent methods: DOC analysis, absorbance measurements at 330 nm, and densitometry of photographic negatives of filters, were used to quantify the precipitation of HA. Half of the HA which would be precipitable at pH 2.0 can be precipitated at pH values from 3.4 to 4.6. These preliminary results have implications for the stability of DOM in waters that experience pH decreases, and for the capacity of DOM to complex metals.     

Impact of acid precipitation on freshwater ecosystems in Norway

Extensive studies of precipitation chemistry during the last 20 yr have clearly shown that highly polluted precipitation falls over large areas of Scandinavia, and that this pollution is increasing in severity and geographical extent. Precipitation in southern Norway, Sweden, and Finland contains large amounts of H⁺, SO⁼ ₄, and NO^? ₃ ions, along with heavy metals such as Cu, Zn, Cd, and Pb, that originate as air pollutants in the highly industrialized areas of Great Britain and central Europe and are transported over long distances to Scandinavia, where they are deposited in precipitation and dry-fallout. In Norway the acidification of fresh waters and accompanying decline and disappearance of fish populations were first reported in the 1920s, and since then in Sørlandet (southernmost Norway) the salmon have been eliminated from several rivers and hundreds of lakes have lost their fisheries. Justifiably, acid precipitation has become Norway's number-one environmental problem, and in 1972 the government launched a major research project entitled ‘Acid precipitation — effects on forest and fish’, (the SNSF-project). Studies of freshwater ecosystems conducted by the SNSF-project include intensive research at 10 gauged watersheds and lake basins in critical acid-areas of southern Norway, extensive surveys of the geographical extent and severity of the problem over all of Norway, and field and laboratory experiments on the effect of acid waters on the growth and physiology of a variety of organisms. Large areas of western, southern, and eastern Norway have been adversely affected by acid precipitation. The pH of many lakes is below 5.0, and sulfate, rather than bicarbonate, is the major anion. Lakes in these areas are particularly vulnerable to acid precipitation because their watersheds are underlain by highly resistant bedrock with low Ca and Mg contents. Apart from the well-documented decline in fish populations, relatively little is known about the effects of acid precipitation on the biology of these aquatic ecosystems. Biological surveys indicate that low pH-values inhibit the decomposition of allochthonous organic matter, decrease the species number of phyto-and zooplankton and benthic invertebrates, and promote the growth of benthic mosses. Acid precipitation is affecting larger and larger areas of Norway. The source of the pollutants is industrial Europe, and the prognosis is a continued increase in fossil-fuel consumption. The short-term effects of the increasing acidity of freshwater ecosystems involve interference at every trophic level. The long-term impact may be quite drastic indeed.     

酸沉降区土壤－作物系统的汞污染

In acid precipitation area of Chongqing suburb the average of Hg in soil rose from 0.158mg/kg in 1984 to 0.20mg/kg in 1989,and Hg content of crops grown on these soils increased too.Both soil and vegetable Hg came mainly from power plant emission.which caused Hg and acid precipitiation pollution in environment and the Hg pollution of water,crops and milk in the area.     

Potential effects of acid precipitation on soils in the humid temperate zone

Unmanaged soils in the northeast United States generally tend toward increasing acidity which results from several natural processes in the soil. Possible effects of acid precipitation on these processes may be caused by hydrogen ions associated with excess anions in the precipitation and, in addition, the anions may also have specific effects. This is especially true for N and S both of which have important biological implications. It is likely that direct effects of the H ion will be modest. As an example, the acidity in 114 cm of rainfall per year (Connecticut's average) with a pH of 4.3 would require 28.5 kg ha ^?1 of limestone for neutralization. By contrast agronomic practice in Connecticut frequently dictates limestone additions as high as several thousand kg ha^?1 to neutralize acidity generated by a combination of natural processes and fertilizer amendments. Studies of rainfall composition in Connecticut from 1929 to 1948 showed no clear trends with time and indicated levels of sulfate and nitrate in rainwater similar to those reported today. In a 10 yr lysimeter study in Connecticut in which tobacco was grown using conventional fertilization techniques, soil pH decreased from 5.4 to 5.0 and both gains and losses of soil cations were recorded. Thus it appears that changes in unmanaged soils induced by acid precipitation alone will be modest and subtle and probably cannot be expressed completely by measuring changes in soil pH value.     

On the prediction of acid precipitation events and their effects on fishes

It is possible to predict acid rain events and melts of acid snow some 12 to 24 hr in advance, including estimation of the magnitude and duration of such events. This is sufficient notice to permit monitoring of stream chemistry and fish plasma and muscle ions before acid stress, and to continue this monitoring throughout and after specific events. Such a program has been in place for 2 yr in waters tributary to the Milford Bay Trout Hatchery, Ontario. During one snow melt in February 1984 surface waters showed a decline to pH 4 and associated negative ANC. Rainbow trout held in such water lost plasma Na and Cl rapidly and died within 28 hr. The hatchery water supply, consisting of a mixture of spring and surface water, showed a decline in alkalinity from 300 to 30 μeq.L^?1, and a pH change from 6.6 to 5.4, during snow melt. Total A1 concentration increased from 42 to 222 μg.L^?1 during snow melt with the “reactive” component increasing from 17 to 112 μg.L^?1. Rainbow trout held in this water did not show physiological stress. More rapid run-off of melt water could be expected to exhaust all of the alkalinity in the hatchery water supply permitting the pH to decline and A1 concentration to rise to levels lethal to the hatchery stock of rainbow trout.     

Variations in the acid content of rain water in the course of a single precipitation

The major acid components in the rain water collected during five different rainfall events in July and August 1977, were found to be a strong acid, the weak acid NH _in4 ^su+ and dissolved CO₂ from the atmosphere. Variations in their concentrations were determined as a function of time in the course of each of the rainfall events. Two experimental methods were used in this investigation, a microtitrim etric method and a coulometric method, and the data were analyzed by the use of modified Gran functions. Both methods gave the same results. The most significant observation was that the strong acid concentration increased from very low values to a maximum and then decreased in the course of a single rainfall event.     

An approach for the evaluation of efficacy of wetlands-based phosphorus control programs for eutrophication-related water quality improvement in downstream waterbodies

It has been suggested that re-creation of the marshes that used to exist in the Lake Okeechobee watershed is the key to the prevention of further eutrophication of this Florida lake. This paper presents a review of the information available on water quality characteristics of this lake and characteristics of its watershed and presents an evaluation of the potential impact of this management alternative on Lake Okeechobee's eutrophication-related water quality. While data were limited and recommendations were made specifying study needs, it was concluded that the construction of the proposed wetlands may have limited impact on eutrophication-related water quality of the lake.     

Changes in chemical processes in soils caused by acid precipitation

In the absence of SO _infin4 ^sup= and NO _inf3 ^su? in precipitation, the pH of precipitation is primarily a function of CO₂?₂0 equilibria. Soil CO₂ and organic acids, acquired during descent through soil profiles, augment the dissolving capacity of the solutions which initially may have a pH of 4 or lower. The recent man-related increase of H₂SO₄ and HNO₃ in rainfall results in a significant lowering of pH in incident precipitation and an increase in corrosiveness of soil solutions. H₂SO₄ and HNO₃ may contribute some Eh buffering capacity. Particularly susceptible to these changes are clay minerals and redox sensitive elements such as Fe, Mn, Ni, and Co. The overall chemical weathering trends associated with increased acidity of rainfall will be de-stabilization and eventual solution of clay minerals (and the loss of their cation exchange capacity), increased rates of chemical denudation, and solution of illuvial Fe and Al oxides and hydroxides. The latter results in the loss of the adsorbed and coprecipitated metal trace elements associated with these highly reactive phases. The general result in soils developed on non-carbonate substrates is a tendency toward extensive podsolization, with associated decrease in clay minerals, loss of cation exchange capacity, and decrease in fertility.     

The history and character of acid precipitation in eastern North America

The history and present distribution of precipitation acidity in eastern North America are reviewed. Precipitation chemistry from the 1920's indicates heavy ionic deposition, but low acidity (calculated) in Tennessee (pH 7.4) and New York (pH 6.15). However, high acidity was apparently widespread over northeast North America by 1955–56 and measured pH's below 4.5 were observed earlier. The geographic distribution of acid precipitation has spread through the present. Yearly average pH values for 1972–73 are not significantly different in New York and New Hampshire, indicating a regional consistency in acid (pH 4.10) deposition. Summer acidity is currently lower in Tennessee than in the Northeast. Precipitation chemistry of individual storms reveals some local variation even within a 3 km range, but a storm in central New York is generally homogenous over 70 km.     

Sequential sampling and variability of acid precipitation in Hampton,Virginia

Rain samples were collected sequentially by amount (≈2.7 mm each) from individual events at a single, relatively isolated, suburban site from August 1977 to July 1980. Rain pH's for ≤ 3 mm samples closely fit a monomodal Gaussian distribution with a median of 4.50 and a standard deviation of 0.39. The variability in pH was primarily interevent as opposed to intraevent. The 3-yr volume-weighted pH was 4.35 ± 0.02 for 3.16 m collected; annual pH's were 4.31, 4.37, and 4.38, and cumulative H⁺ deposition was 141 mg H⁺ m^?2. Event-averaged rain pH and meteorological and air quality data were correlated. Low pH was associated with low rainfall volume and rate; rain after several dry days; rains with northeast surface winds; high SO₂, NO₂, and O₃ in the ambient atmosphere; and high, strongly correlated, SO₄ ⁼ and NO₃ ^? rainwater concentrations. The lowest 3-yr seasonal average pH (4.31) occurred during summer; values for other seasons were ≈4.37. Average intraevent H⁺ molarity (volume-weighted) was accurately characterized by 6.89 E^{?5 *}(mm ram)^?0.215. The relative merits of composite (e.g., whole event) and sequential sampling are examined.     

The role of neutral salts in the ion exchange between acid precipitation and soil

Theory and experimental results have shown that neutral salts in the precipitation or supplied to the ground by other means reduce the acidification of soils by acid precipitation. This salt effect is caused by the cation exchange occurring after the entry of the rain water into the soil.The acid components of precipitation consist of H₂SO₄, HNO₃ and HCl and of NH₄⁺ after nitrification in the soil. The magnitude of the salt effect depends on the relative bonding energy of H₃O⁺ and of Ca²⁺, Mg²⁺, Na⁺, K⁺, NH₄⁺ in the soil as well as on the concentrations of H₃O⁺ and the above cations in the precipitation. The salt effect may be considerable in very acid soils. It decreases with rising pH to become very small or negligible in neutral soils, chiefly due to the increasing bonding energy of H₃O⁺ in this direction.The adverse effect of acid precipitation, therefore, is likely to be less in very acid soils, such as podsols, than in slightly acid and neutral soils with low buffering capacity against pH change. Soil texture and calcite content are very important factors in this respect as fine material and calcite increase the buffering.     

Acidification of lakes in Canada by acid precipitation and the resulting effects on fishes

Water, Air, & Soil Pollution - In the Sudbury region of Ontario, Canada, fallout of sulfur oxides has been shown to be responsible for damage to vegetation, lakes and fishes. The acidic fallout...