Mean Annual pH Research Articles

ACID RAIN-AN INVISIBLE THREAT

Acid Rain is defined as precipitation (rain) that has a pH lower than 5.6, which is the pH expected in distilled water exposed to the atmosphere. (pH is a measure ot the acidity or alkalinity of a water sample.) The pH Of precipitation undoubtedly is affected by a variety of natural sources of acidic and alkaline materials (e.g. volcanic gases, gases from decompoSng Organic matter and soil dust). However it has recently become apparent that rain and snow in certain regions of the earth are consistently more acidic than expected. The European Atmosphere Chemistry Net Work first recognized that the pH of precipitation was declining in Scandinavia during the late 1960's. Current data indicates that the mean annual pH in this region was 5.0 - 5.5 in the late 1950's which declined to 4.2 • 4.4 in the mid 1970's. In Eastern North America precipitation is now more acidic than in Scandinavia. The median pH for 1978 • 1979 ranged from 4.0 to 4.4 in North Eastern U.S. and South Eastem Canada. Although there is disagreement over the Source and nature Of acidic precipitation , the most widely accepted view is that the increased acidity is a result of the presence Of increased quantities Of sulphuric and nitric acids. These acids are believed to result from oxidation Of sulphur and nitrogen oxide gases. Oxides of sulphur and nitrogen are produced from combustion of fossil fuels, metal smelting and various industrial processes.

Land use influences on acidification and recovery of freshwaters in Galloway, south-west Scotland

Abstract. The long term response of surface waters to changes in sulphur deposition and afforestation is investigated for three upland river systems in the Galloway region of south-west Scotland. From 1984-1999, these rivers exhibited a statistically significant decline in non-marine sulphate concentrations in response to reduced acid deposition. This reduction in non-marine sulphate was, however, insufficient to induce a pH recovery over the period. A statistically significant increase in river pH was observed between 1956-1970 (0.05 yr-1) when subsidised agricultural lime payments were at a maximum. In 1976, this subsidy ceased and surface waters have progressively acidified. In addition, climatic change is found to influence long-term trends in pH. Mean annual pH was greatest during a dry period between 1969-1973 when total annual discharge was low. Thereafter, pH declined gradually in response to higher rainfall and increased total annual discharge. Overall, surface waters draining the afforested catchments of the Rivers Cree and Bladnoch are more acid than those draining the moorland catchment of the Luce. These results indicate that in afforested catchments, current reductions in sulphur emissions have not led to an observed improvement in the acid status of surface waters. Forestry, therefore, represents a confounding factor with regard to chemical recovery from acidification in this region. Keywords: acidification, afforestation, deposition, rivers, lochs, non-marine sulphate, pH

Fog and Precipitation Chemistry at Mt. Rokko in Kobe, April 1997-March 1998

Fog water and precipitation were collected and analyzed to study fog and precipitation chemistry. The research was carried out through one year from April 1997 to March 1998 at Mt. Rokko in Kobe. Higher fog occurrence and larger volume of fog water were observed in summer, corresponding to the trend of seasonal variation in precipitation amount. The annual mean pH value of fog water (3.80) was lower by ca. one pH unit than that of precipitation (4.74). The concentration of chemical species in fog water was ca. 7 times that in precipitation. The highest anion and cation concentrations were SO4 2− and NH4 + in fog water and Cl− and Na+ in precipitation, although the Cl−/Na+ equivalent ratio in both fog water and precipitation was almost the same value as that in sea water. It is considered that in the longest fog event, NH4 + and nss-SO4 2− in fog water mainly scavenged as (NH4)2SO4, mainly derived from (NH4)2SO4 (aerosol) in the atmosphere, NH3 was scavenged at the growing stage, and SO2 was also scavenged after the mature stage. NO3 − in this fog event was mainly absorbed as HNO3.

Atmospheric SO2 Pollution and Acidity of Rain in Changchun China

It is mainly SO2 that bring about acid rain in China. Changchun City, which is located in Northeast China, is a typical city that is polluted by SO2 from coal combustion in winter. In winter, the daily mean concentration of atmospheric SO2 is about 0.10mg/m3 and about 5 times as high as in summer, and the daily highest concentration usually appears in daybreak and nightfall. The monitored lowest pH value of rainwater was 4.8 in spring and the range of pH value of rain /snow was 5.2–6.0 in winter, 4.8–5.8 in spring, 5.4–6.4 in summer, 5.6–6.4 in autumn, and the annual mean pH value of rainfalls was 5.8 (1999–2000). Because the alkaline aerosol from soil, meteorological conditions etc., is unfavorable to acid rain formation, even though high SO2 emission intensity existed in winter, the acid rain did not appear obviously. The aerosol character, climate conditions in Northeast China are important factors for the acid rain formation, although SO2 emission is the original cause.

Rapid Time Variations in Chemical Composition of Precipitation in South Korea

Data from a monitoring program on precipitation at four sites in South Korea during the period from 1993 to 1998 were analyzed for determining a time trend relationship in chemical composition of precipitation. The concentrations of nss-sulphate, ammonium and calcium were found to have decreased over time at a statistically significant level in Seoul (p<0.05). The concentration of nss-sulphate had declined by a rate of 12% per year for the period from 1993 to 1998. The concentrations of ammonium and calcium decreased by 11% and 12% per year respectively for the same period. The concurrent reduction of cation offsets the change in strong acid anion, thus the annual mean pH of precipitation has been approximately constant. In contrast to the rapid change of sulphate, the second most abundant anion, nitrate, showed no statistically significant decrease. As a result, the nitrate to nss-sulphate ratio (N/S ratio) has increased rapidly; the N/S ratio in precipitation has increased from less than 0.1 in 1985 to nearly 0.5 in 1998 at Seoul. In spite of the short monitoring period, a significant upward trend in the N/S ratio was also observed at all of the other sites suggesting that the nitrogen species contribute more to precipitation acidity throughout Korea.

Mineralogical composition of African dust delivered by red rains over northeastern Spain

The African dust deposition, mineralogy, source regions, and influence on rain chemistry were analyzed for a site in the Montseny mountains (Catalonia, northeastern Spain) for the period August 1, 1983, through August 1, 1994. Dust deposition was highly variable: two events (collected on November 9–11, 1984, and March 22–25, 1991) accounted for 62% of the total dust input in the 38 red rain events recorded in the period. The average annual dust deposition was 5.3 g m−2 (SE 2.6). Three source regions in the African continent were identified with back trajectory analysis: (1) Western Sahara, (2) Moroccan Atlas, and (3) Central Algeria. Events from the Moroccan Atlas predominated in terms of number of events, amount of rainfall, and dust deposition. The meteorological situations during red rains were identified: Western Sahara events occurred principally with a depression at high latitudes (50°N) forming a trough in the North Atlantic, Moroccan Atlas events occurred with a depression in front of Portugal, and events from central Algeria were associated with a depression over Spain or North Africa. By order of abundance (median of n=13) the minerals identified in the dust by X ray diffraction were as follows: illite &gt; quartz &gt; smectite &gt; palygorskite &gt; kaolinite &gt; calcite &gt; dolomite &gt; feldspars. Differences in mineralogy between source regions were significant for smectite, kaolinite, quartz, and dolomite. Smectite and kaolinite content was highest in the Algerian events, while quartz and dolomite content was lowest. Events from the Moroccan Atlas had the lowest smectite and kaolinite. The red rain soluble chemistry was clearly influenced by the dissolution of calcite (high alkalinity, calcium concentration and basic pH) and by marine components (high Na+, Cl− arid Mg+2 concentrations). Because of the very alkaline character of red rains they had a strong weight on the annual mean pH of rainwater. This was reflected by the significant relationship (r=0.71, p&lt;0.01) between the percentage of annual precipitation as red rain and annual mean precipitation pH. Red rains provided 25–45% of the annual dissolved input of the major ions in precipitation and 34% of the calcium required for holm oak (Quercus ilex L.) forest growth at the study site.

Trends in background air pollution parameters over India

The Background Air Pollution Monitoring Network (BAPMoN) data from ten stations in the Indian region for the period 1973–1990, has been used to determine the background trends. Falling pH and increasing turbidity trends have been noticed in all but one of the stations. The post 1982 epoch has witnessed fall in annual mean pH at Vishakhapatnam, Allahabad, Pune and Nagpur though the reduction of mean values are not statistically significant at 5% level of confidence. Frequency distributions of the values of turbidity coefficient B(500 nm) for the epochs 1974–1980, 1981–1985 and 1986–1990 are also presented here. The trend of atmospheric burden is seen to be positive upto the second epoch and stable subsequently. The source identification for chemical constituents of rainwater has been examined by carrying out principal component analysis and using BAPMoN rain chemistry data collected in the entire period of 1974–1988.

Chemical composition of precipitation in a forest area of Chongqing, Southwest China

Experiments were carried.out in Chongging-a city seriously damaged by acid precipitation in southwest China — to explore chemical compositions of open bulk precipitation, throughfall and stemflow in a Masson pine (Pinus massoniana) forest. The results showed that annual mean pH values of and annual ion depositions in the three types of rain water were 4.47 and 50.6 g m−2, 3.82 and 69.7 g m−2, and 2.92 and 0.215 g m−2 respectively. pH values demonstrated an obvious seasonal variation; they were lower in winter than in the rest of the year. Ca2+ and NH inf4 sup+ together made up more than 80% of the total cation, while SO in4 sup2− alone contributed over 90% to the total anion. This high level of SO in4 sup2− in rain water in Chongqing, which outran those found in other cities in China, was closely related to the combustion of locally produced coal that contains 3 to 5% sulphur. Thus, acid precipitation in Chongqing is of a typical sulphuric-acid type.

Precipitation chemistry in Japan 1989?1993

Precipitation chemistry in Japan was discussed on a wet-only sample database obtained in a nationwide survey from April 1989 to March 1993. Wet-only samples were collected at 29 stations over Japan on a biweekly basis. Commonly determined chemical parameters were measured in laboratories. The volume-weighted annual mean pH at each site ranged from 4.50 to 5.83 with a mean of 4.76. Concentration ranges and means (parenthesized) on an equivalent basis for major ions were as follows: nss-SO4 2−; 5.2–58.9 (38.6), NO3 −; 1.8–25.0 (14.1), NH4 +; 0.55–29.8 (18.3), nss-Ca2+; 2.0–34.5(14.2), Na+; 6.4–275.3 (49.1), Cl−; 13.7–322.4 (63.5) β eq L−1. Acid-base relationships for Phase-II records were quantitatively discussed in terms of three measures: pH, fractional acidity, and our proposed pAi.

Effect of acid deposition on forested catchment in the western Tokyo, Japan

Acid deposition and its effect on Andisols were investigated in the forest experimental station, the Rolling Land Laboratory (RLL), located in the Tama Hill region of Central Japan. The annual volume-weighted mean pH value of open bulk precipitation was 4.8 in the period 1990 to 1992. Nitrate deposition at RLL was larger than for sulfate, which was obviously different from results in Japan Environment Agency (JEA) stations or in study areas of Europe and North America. Abundant nitrate deposition was ascribed to the high emissions from a non-point source, mainly cars. Although sulfate concentration in throughfall fluctuated, its concentration in soil solution was kept at a low level. This was attributed to the high sulfate adsorption capacity of the Andisols.

Effect of acidic deposition on forested andisols in the Tama Hill region of Japan

Acid deposition and its effect on Andisols was investigated in the forest experimental station, the Rolling Land Laboratory, the Tama Hill region, central Japan. The annual volume-weighted mean pH value of open bulk precipitation was 4·8. The acidity of stemflow from coniferous trees was attributed to dry deposition of air pollutants. The acidic stemflow affected the chemical composition of the soil solution and the pH of soils around the coniferous trees. The concentration of aluminum in the soil solution was accompanied by nitrate which was provided by nitrification in the low soil pH range. The concentration of aluminum in the soil solution, which ranged from 0·02 to 0·12 mmol c liter −1 is similar to the critical levels for the roots of the trees. Andisols in the surface horizon are acidified due to the atmospheric acid deposition, even though seepage from the catchment is still neutral.

Development and Evaluation of a Biological Model to Assess Regional-Scale Effects of Acidification on Atlantic Salmon (Salmo salar)

We developed an age-structured simulation model incorporating pH-dependent mortality to assess impacts of acidification on Atlantic salmon (Salmo salar) populations at the reach and river system level. Applied to the LaHave River, Nova Scotia, acidic reaches (mean annual pH 4.6–5.1) were predicted to have 0–15% of the annual smoit production and 0–31% of the maiden spawner production compared with circumneutral reaches (pH ≥ 5.6) and increased juvenile growth due to lower parr densities. The benefit of increased growth (earlier age of smoltification and increased early marine survival) was not sufficient to outweigh impacts of higher freshwater juvenile mortality. Simulated removal of acidic conditions resulted in a 41% increase in recruits, but only after several decades following complete chemical recovery. Circumneutral reaches were predicted to be 4–12 times more efficient at producing smolts and 3–7 times more efficient at producing adults from hatchery fingerlings compared with acidic reaches. To maintain current target egg deposition rates of 240 eggs/100 m2, circumneutral reaches could withstand grilse exploitation rates of up to 65%, while acidic reaches, even without harvesting mortality, could not maintain this level. Fisheries management strategies need to account for variability in freshwater production both within and between river systems.

Time Compatibility of Water Chemical Lake Variables

AbstractThis paper summarizes results from extensive field work in 95 Swedish lakes. The focus is on methodological aspects of importance when establishing the time compatibility of traditional water variables (monthly data on pH, Secchi depth, temperature, alkalinity, total‐P, conductivity, Fe, Ca, hardness and colour from 4 years, 1986 to 1989). From most textbooks in limnology, it is evident that there exist patterns, in terms of how the concentrations and the variability of the concentrations of these standard variables vary in lakes. Then it would be interesting to see if there exists patterns also for the time compatibility between different lake variables and different variants of the same variable, i.e., mean values from different periods. This issue is discussed in a systematic way in this paper with statistical methods. These results are of importance in ecosystem analyses, monitoring and modelling. These parameters generally vary in a lake, both temporally and areally, the focus here is on such variations and how to express lake‐typical, time compatible values for longer periods of time. Selected results: High correlations (r2‐values) exist between (1) mean annual pH and all the variants of alkalinity and lake colour for different periods of time. (2) between mean (3 year) total‐P and most of the variants of total‐P, especially those from the winter period (months 10 to 12; r2 ≈ 0.95), but not for the variants from the spring and the summer periods, when the variability is great for total‐P, (3) between mean (3 year) lake colour and most of the variants of Fe and pH, especially those from the first half of the year for pH and those from the second half of the year for Fe. Quite high r2‐values, about 0.5, exist between colour and different variants from the winter period for total‐P and Secchi depth.

Effects of simulated acid rain on the growth of agricultural crops

Three species of crops, radish, spinach and bush bean, were exposed to simulated acid rain at pH 5.6 (control) to 2.5 throughout their growing periods. Plants were subjected to acid rain treatment three times a week, for one hour with 10mm of precipitation at a time. All the plants exposed to simulated acid rain falls at pH3.0 or below produced visible injury on the leaves. The visible injuries were severe on the cotyledons of radish and spinach and primary leaves of bush bean exposed to rain at pH 2.7 and 2.5, which resulted in the growth reduction of plants at early stages of growth compared to pH 5.6. In none of the cases in this study did treatment at pH 3.0 or higher significantly affect the growth of leaf area or dry weight of whole plants in three species. These results suggest that current ambient levels of rain acidity in Japan, where annual mean pH value is about 4.6, may not affect growth in the three species of crops tested in this study.

A regional model of acidification in Wales

A regional assessment of streamwater quality in Wales is presented which reconstructs the historical trend for acidification and predicts the effect of several pollutant deposition reduction policies, using the model of acidification of ground water in catchments (MAGIC). The regional methodology used is a two-stage coupling of Monte Carlo simulations with a calibration procedure designed to produce a coarse fit to the joint distribution of the key streamwater quality variables. The regional model is based on data from the Welsh Water Authority Survey of 1983–1984 during which streams and lakes were sampled weekly for one year. The modelling results reveal a significant decline of water quality across the region since industrialization. The model indicates that 40% of the streams and lakes within the region have suffered a decline of mean annual pH of > 0.5 pH units. Predictions indicate that a 30% reduction of deposition would maintain present-day stream quality levels. Reductions of the order of 60% are required to ensure a significant recovery at most sites across the region.

LONGITUDINAL AND SEASONAL WATER CHEMISTRY VARIATIONS IN A NORTHERN APPALACHIAN STREAM1

ABSTRACT: Quaker Run, a fourth order stream located in southwestern New York State, exhibits a highly unusual chemical gradient along its upper reaches. Weekly water samples showed an increase in the mean annual pH from 5.07 to 7.01 along a stretch of only 2.2 km. Mean alkalinity, calcium, magnesium, sodium, potassium, nitrate‐nitrite‐nitrogen, silica, and conductivity also increased appreciably over this distance. The study area receives some of the most highly acidic atmospheric deposition in the United States. Minimal buffering of these acidic inputs in the extreme upper watershed, and an abrupt downstream increase in buffering associated with changes in soil type, apparently produce the observed streamwater chemistry gradient. In contrast, a comparison between 11 midstream, downstream, and tributary sites showed relatively little variation in streamwater chemistry. In addition to the pronounced longitudinal chemistry changes along the upper portion of the stream, pronounced temporal chemistry variations were also observed at all sampling sites. High flow during snowmelt and heavy rains produced more dilute, acidic conditions, while streamwater pH and dissolved base cations were generally highest during low flow. Much of this temporal variation in streamwater chemistry is attributed to seasonal variation in residence times of soil water.

Characteristics of three acidic lakes in Kejimkujik National Park, Nova Scotia, Canada

This report summarizes a study of the chemical and biological characteristics of three oligotrophic lakes located in a region that receives a moderately acidic precipitation (mean annual pH 4.5-4.6), and a sulfate deposition of about 20 kg/ha/yr. The two brownwater lakes are relatively acidic (pH 4.5 and 4.8), and much of their acidity is attributable to organic anions. The brownwater lakes also have a large concentration of aluminum and iron, but these are bound to dissolved organic matter and are relatively non-toxic to biota. Average phytoplankton production was largest in the clearwater lake. This was due to its relatively deep euphotic zone, since the average unit-volume productivity did not differ much among the lakes. In fact, productivity at light optimum was largest in the most acidic brownwater lake, probably because of its larger phosphorus concentration. The clearwater lake had extensive macrophyte vegetation, which covered its bottom to a depth of 6.5 m. In the brownwater lakes, macrophytes were confined to shallow nearshore water because of the limited water transparency. Zooplankton density and biomass were largest in the most acidic brownwater lake, probably because of allochthonous organic particulates and little fish predation. Benthic invertebrates were abundant in all three lakes, and were dominated by insects, especially Chironomids. Lakes in the study area appear to be sustaining fish populations at more acidic pHs than elsewhere. This may be due to the large concentration of dissolved organic matter in many lakes, which complexes and partially detoxifies metals such as aluminum.

Precipitation and streamwater chemistry from undisturbed watersheds in the cascade mountains of Oregon

Long-term records of precipitation and streamwater chemistry are rare; such records from forested watersheds relatively free of acidic deposition are even rarer. Precipitation and streamwater chemistry have been measured on two undisturbed forested watersheds at the H. J. Andrews Experimental Forest located on the western slopes of the Cascade Mountains of Oregon. Data from one watershed spans the period 1973–1985, the other 1969–1985. The mean annual pH of precipitation was 5.5 with a range of 4.7 to 6.0. HCO3 − was the dominant anion; Ca2+ and Na+ were the dominant cations. The mean annual pH of streamwater was 7.3, and was dominated by HCO3 − and Ca2+. These data contrast sharply with data from other calibrated watersheds in the north Cascade Mountains of Washington and British Columbia, and with data from New Hampshire and North Carolina where pH of precipitation averages 4.14 and 4.43, respectively, with SO4 2− the dominant anion.

Ion Mass Balances and Seasonal Fluxes from Four Acidic Brownwater Streams in Nova Scotia

Precipitation and four brownwater streams in southwestern Nova Scotia were sampled for 3–5 yr. Precipitation cation chemistry was dominated by H+ (44% of cation equivalents) and Na+ (38%), while anions were dominated by Cl− (44%), SO42− (41%), and NO3− (15%); mean annual pH was 4.6, and acidity was correlated with concentrations of SO42− (r = 0.90) and NO3− (r = 0.82). Surface water chemistry was dominated by Na+ (51% of cation equivalents), Mg2+ (17%), and Ca2+ (16%), while H+ averaged only 4%; anions were dominated by Cl− (53%), organic anions (23%), and SO42− (21%); H+ was not strongly related to concentrations of other ionic constituents (the most consistent correlation was with sulfate, but this was weak and accounted for &lt;30% of the variation). Hydrogen ion was consumed in all four watersheds by an average value of &gt;75%. Water flow was by far the strongest determinant of annual pattern of flux of chemical constituents from the watersheds. Seasonal variations of concentration were of relatively small magnitude and had much less influence on patterns of flux.

RAINFALL AND WATER QUALITY IN THE SOUTHERN PLAINS

ABSTRACT The chemical composition of rainfall, agricultural runoff, groundwater, and pond water at several rural Oklahoma and north Texas locations was determined over a number of years (1972–1985). The inputs of acid, P, Cl, and cations in rainfall are not of major agronomic importance, although inputs of N (as NO3-N and NH4-N) and S (as SO4) in rainfall can contribute a significant proportion of the uptake of these elements by grasses or crops. The mean annual pH of rainfall was consistently greater than that of pure rainfall (5.6) averaging 6.5, while the average pH of two farm ponds (7.8) was even greater than that of rainfall. If a decrease in the pH of rainfall in the Southern Plains should occur in the future, the impact of the acidity on surface water will be reduced to a certain degree by the buffering capacity of the area soils. Appreciably more acid was added annually to the agricultural soils of the area via fertilizer P and N than in rainfall. Under present conditions it would take up to 1,500 years rainfall to add as much acid as added by fertilizer in one year. Even with a dramatic decrease in rainfall pH to 4.0, this period would be 10 years. Thus, rainfall acidity presents no immediate threat to agricultural soils, groundwater, or lakes in Oklahoma and north Texas under continuing management practices, although periodic monitoring is recommended due to an increasing number of coal-fired power stations located in this area.