Using Thermal Sensitivity Analysis to Determine the Impact of Drainage on the Hydrochemistry of a Tropical Peat Soil from Malaysia

Peat from an area of pristine swamp in Malaysia and from an area of that swamp drained 10 years earlier for agriculture was incubated along a temperature gradient from 0 to 20 °C to simulate microbial activity through changes in temperature. With increasing temperature, nitrate availability decreased in the pristine peat but increased in the drained peat, suggesting that drainage has altered the principle nitrate transformation process from denitrification to nitrification. Sulfate concentrations in the pristine peat exhibited a greater proportional decrease with increasing temperature than in the drained peat, suggesting that drainage has decreased the influence of sulfate reduction over sulfate availability at this site. With the exception of phosphate, nutrient concentrations in the drained site were significantly greater (P < 0.05) than in the pristine site. Biogeochemical models should consider that drained peatlands may respond very differently to the temperature change predicted by current climate change models.     

Characterizing Episodic Stream Acidity During Stormflows in the Great Smoky Mountains National Park

Episodic acidification of surface waters has been observed in the Great Smoky Mountains National Park, similar to other forested watersheds with base-poor bedrock in the eastern US receiving acids from atmospheric deposition. Three remote, forested, high-elevation streams were selected in the Little Pigeon River watershed for study; two of which brook trout have extirpated, and believed to have resulted from severe acidity during stormflows. This research characterized stream chemistry during episodes in order to better understand potential factors that contribute to rapid drops in pH and acid neutralizing capacity (ANC) during stormflows. Autosamplers initialized by sondes, collected samples during storm events for analysis of pH, ANC, cations, and anions over a 15-month period. ANC and pH depressions, and increased concentrations in sulfate, nitrate, and organic acids were observed for all storms at each study site. ANC contribution analysis indicated sulfate was the strongest contributor to ANC depressions, but nitrate, cation dilution, and organic acids were also significant in some cases. Acidic deposition appears to be the primary source of episodic acidification, supported also by the finding that larger stormflows preceded by long, dry periods resulted in significantly larger pH depressions. It appears stream acidification episodes may be driven by acid deposition. However, this study documents the variability of several ion contributors to observed stormflow ANC depressions illustrating the spatial and temporal complexity of watershed processes that influence this phenomenon.     

Comparison of Acid Neutralization by Chemical Weathering Between Acidified and Non-Acidified Watersheds

In eastern Asia, emission of acid materials and acid depositionwill increase with industrialization in future, and freshwatersin Japan are likely to become acidified. In this article, anevaluation method for acid-neutralization by chemical weatheringwas applied to one acidified watershed in U.S.A. and three non-acidified watersheds in Japan, and effect of hydrogeochemicalproperties on chemical weathering and stream water chemistry wasdiscussed. In three non-acidified watersheds in Japan, arealchemical weathering rates of primary minerals are much largerthan those observed in U.S.A. Watersheds in both countries showno difference in mineralogy, while the soil thickness (weatheredprofile) in watersheds is contrastive between acidified and non-acidified watersheds. Therefore, it is concluded that acidity is neutralized by chemical weathering of primary minerals in thick weathered profiles in Japanese watershed. In non-acidified Japanese watersheds which has the smallest acid-neutralization capacity in three observed watersheds, stream water will not acidify even if the acid deposition increases asmuch as two or three times the observed level. From the viewpoint of Japan's nationwide streamwater chemistry, more than 90% of the watersheds have far greater acid-neutralization capacities than this watershed, and will not be acidified even in cases where the acid deposition increase as much as two or three fold.     

Atmospheric sulfur and nitrogen in West Java

Wet-only rainwater composition on a weekly basis was determined at four sites in West Java, Indonesia, from June 1991 to June 1992. Three sites were near the extreme western end of Java, surrounding a coal-fired power station at Suralaya. The fourth site was ～100 km to the east in the Indonesian capital, Jakarta. Over the 12 months study period wet deposition of sulfate at the three western sites varied between 32–46 meq m^?2 while nitrate varied between 10–14 meq m^?2. Wet deposition at the Jakarta site was systematically higher, at 56 meq m^?2 for sulfate and 20 meq m^?2 for nitrate. Since sulfate and nitrate wet deposition fluxes in the nearby and relatively unpopulated regions of tropical Australia are both only ～5 meq m^?2 anthropogenic emissions of S and N apparently cause significant atmospheric acidification in Java. It is possible that total acid deposition fluxes (of S and N) in parts of Java are comparable with those responsible for environmental degradation in acid-sensitive parts of Europe and North America.     

Hydrogeochemical Conditions Affecting Acidification of Stream Water in Mountainous Watersheds

Acid deposition in eastern Asia will increase and freshwaters in Japan are likely to become acidified in future. In order to make long-term predictions about freshwater acidification, it is necessary to evaluate acid neutralization mechanisms in Japanese watersheds. Ikeda and Miyanaga (1999) earlier proposed a method of separating acid-neutralization capacity into chemical weathering and cation exchange. By this means, we were able to assess the effect of hydrogeochemical properties on chemical weathering and stream water chemistry for three watersheds in Japan. On the basis of this assessment, acid-neutralization stream water chemistry was predicted using the ILWAS (Integrated Lake-Watershed Acidification Study) model. The main factors determining acidification are the thickness of weatherd profile and chemical weathering rates. The principal results are: (1) for non-acidified watersheds in Japan, acid deposition is neutralized by chemical weathering of primary minerals; (2) freshwaters in Japanese watersheds will not acidify even if acid deposition increases to the extent found in an acidified watershed in the U.S.A.     

Modeling fate and transport of sulfate and alkalinity in an acidified lake

Acid mine drainage from Contrary Creek flows into an entire arm of Lake Anna. Much of the acid inflow is neutralized by bacterial sulfate reduction in the lake sediments. We developed a simple model to track the seasonal fate and mass transport of sulfate and alkalinity along the acidified arm. The loss of sulfate from the water column was characterized by a first-order decay reaction. A gain in alkalinity due to sulfate removal was also incorporated in the model. In addition, CO₂ acidity and pH in the water column were calculated. The model was calibrated with data collected in 1983 and 1984. Model sensitivity runs were conducted to demonstrate the importance of sulfate reduction in the system.     

Towards a new method of setting a critical load of acidity for ombrotrophic peat

Critical loads of acidity for mineral soils can be set according to the capacity of the underlying bedrock to replenish the base cations leached by acid deposition. Unfortunately, this relatively simple approach cannot be applied to peat, one of the most widely occurring soil types in the wetter, western areas of Europe. These organic soils depend on atmospheric deposition for their supply of base cations rather than mineral weathering. We aim to develop a critical load methodology for ombrotrophic peat, using a combination of field observations and laboratory experiments. Simulated rain has been applied to intact cores of peat to determine the key chemical processes governing the response of these soils to both increases and decreases in acid deposition. It is evident that peat does not behave as a simple ion exchanger; the complex reactions of decomposition, sulphate reduction, nitrate uptake and organic acid production also control the response to acid inputs. This paper looks at some of the results from these experiments and considers the implications for setting critical loads.     

The effect of organic acids on base cation leaching from the forest floor under six North American tree species

Organic acidity and its degree of neutralization in the forest floor can have large consequences for base cation leaching under different tree species. We investigated the effect of organic acids on base cation leaching from the forest floor under six common North American tree species. Forest floor samples were analysed for exchangeable cations and forest floor solutions for cations, anions, simple organic acids and acidic properties. Citric and lactic acid were the most common of the acids under all species. Malonic acid was found mainly under Tsuga canadensis (hemlock) and Fagus grandifolia (beech). The organic acids were positively correlated with dissolved organic carbon and contributed significantly to the organic acidity of the solution (up to 26%). Forest floor solutions under Tsuga canadensis contained the most dissolved C and the most weak acidity among the six tree species. Under Tsuga canadensis we also found significant amounts of strong acidity caused by deposition of sulphuric acid from the atmosphere and by strong organic acids. Base cation exchange was the most important mechanism by which acidity was neutralized. Organic acids in solution from Tsuga canadensis, Fagus grandifolia, Acer rubrum (red maple) and Quercus rubra (red oak) were hardly neutralized while much more organic acidity was neutralized for Acer saccharum (sugar maple) and Fraxinus americana (white ash). We conclude that quantity, nature and degree of neutralization of organic acids differ among the different tree species. While the potential for base cation leaching with organic acids from the forest floor is greatest under Tsuga canadensis, actual leaching with organic anions is greatest under Acer saccharum and Fraxinus americana under which the forest floor contains more exchangeable cations than does the strongly acidified forest floor under Tsuga canadensis.     

Soil Acid-Base Chemistry of a High-Elevation Forest Watershed in the Great Smoky Mountains National Park: Influence of Acidic Deposition

Understanding the acid-base chemistry of soil and the soil processes related to the release or retention of sulfate and nitrate is important in order to predict watershed recovery from long-term acid deposition. Soils were sampled from the Noland Divide Watershed (NDW), a small, high-elevation watershed in the Great Smoky Mountains National Park receiving high rates of acid deposition over several decades. Soil samples were measured for chemical properties related to acidification and used to conduct sulfate adsorption and nitrogen (N) incubation experiments. Shallow soil was higher in acidic and basic ions than deeper soils, and the mean effective cation exchange capacity was 8.07, 5.06, and 3.57 cmol_c kg⁻¹ in the A, Bw, and Cb horizons, respectively. In all three soil horizons, the base saturation was equal to or below 7% and the ratio of Ca/Al was below 0.01, indicating that the NDW is very sensitive to acid deposition. Based on results from sulfate adsorption isotherms, the NDW has not reached its maximum sulfate adsorption saturation and is likely able to retain further additions of sulfate. Desorption of sulfate from NDW soils is expected if sulfate concentrations in soil solution drop below 50 μeq L⁻¹ but is highly dependent on soil pH and organic carbon content. Total soil organic N was 500 times greater than inorganic N in the A soil horizon, and net N mineralization and nitrification remained constant during a 28-day incubation indicating a large reservoir of N substrate for soil microbes. Nitrogen experiment results suggest that nitrate export from the watershed is largely controlled by biological processes rather than by nitrate deposition flux. Soil data collected in this study contributes to our understanding of biogeochemical processes affecting the response of acid-impacted ecosystems such as the NDW to future changes in atmospheric deposition.     

Characteristics of Nitrogenous Air Pollutants at Urban and Suburban Forested Sites, Western Japan

Nitrogenous air pollutants including nitrogen dioxide (NO₂), nitric acid (HNO₃), nitrate (NO ₃ ^? ), ammonia (NH₃), ammonium (NH ₄ ⁺ ), and nitrous acid (HONO) were characterized at an urban forested (UF) site in Hiroshima and at a suburban forested (SF) site in Fukuoka, western Japan, using an annular denuder system for 1?year from May 2006 to May 2007 to compare the concentrations and chemical species of atmospheric nitrogenous pollutants between UF and SF sites. The proximity of the urban area was reflected in higher NO₂ concentrations at the UF site than at the SF site. NO₂ was more oxidized at the SF site because it is farther from an urban area than the UF site, which was reflected in higher concentrations of HNO₃ at the SF site than the UF site. HNO₃ and acidic sulfate is neutralized by NH₃, existing as ammonium nitrate (NH₄NO₃) and ammonium sulfate [(NH₄)₂SO₄] at the UF site. At the SF site, acidic sulfate is neutralized by NH₃, existing as (NH₄)₂SO₄, but NH₄NO₃, had scarcely formed at the SF site. A much higher HONO concentration was observed at the UF site than at the SF site, especially in winter and spring at night, which could be explained by higher NO₂ concentrations at the UF site because of its proximity to an urban area and stagnant meteorological conditions. Atmospheric HONO determination was critical in evaluating the possibility of damage to trees in UF areas.     

Modeling the transport of acidity in soil profiles with front — A dynamic transport model

A dynamic transport model, FRONT, that describes the downwards transport of acidity in podzolized forest soils is presented. In this model the downward transport of acidity with the soil solution is counteracted by a production of alkalinity through the weathering of primary minerals and delayed by the adsorption of sulfate and hydrogen ions on iron- and aluminium oxides. The heart of the model is a massbalance equation that describes the transport of bulk acidity/alkalinity. The FRONT model was tested on 23 deep soil profiles situated along three transects in west-to-east direction across Sweden. Using a deposition scenario starting at 1910 the model was able to account for the large regional differences in the present depth of the acid front. Assuming a linearly decreasing deposition until 30% of present deposition is reached in 2010 the model was used to simulate a scenario for profiles in different parts of Sweden. The scenarios indicated that the upper parts of soil profiles that are severely acidified today will recover and assume a new steady-state in 2030. However, for soil profiles that have large stores of adsorbed sulfate in the B horizon the simulations indicate that one can expect an increased acidity in the deep soil layers several decades after the deposition has ceased due to downward transport of acidity.     

Mechanism of acid-neutralization in two Japanese watersheds

In Japan, acidification of terrestrial water has not yet been reported except lakes acidified by volcano or mine. However, acid deposition in Japan is as much as those in northern Europe and north-eastern U.S.A., and acidification of terrestrial water may occur in future. In order to predict long-term acidification, it is necessary to understand acid-neutralization mechanism in watershed. Therefore, two experimental watersheds study for geology, hydrology, and water chemistry were conducted. On the basis of these data, chemical change in percolation of precipitation through watersheds and acid-neutralization mechanism are analyzed. The principal results are: (1) Acid deposition is neutralized continuously in percolation of precipitation from ground-surface to aquifer, (2) Chemical weathering of primary minerals plays an important role in the acidneutralization in the watersheds, and should be quantified and taken into account in the long-term prediction of acidification.     

Proton Budgets of Forest Ecosystems on Volcanogenous Regosols in Hokkaido,Northern Japan

The proton budgets of deciduous and coniferous forest ecosystems on volcanogenous regosols in Hokkaido, northern Japan, were studied by measuring the biogeochemical fluxes (atmospheric deposition, canopy leaching, vegetation uptake and leaching from soil) at each site during a three year period. The proton budgets were developed for individual compartments of the ecosystem: vegetation canopy, organic and mineral soil layers. At both sites, atmospheric S deposition was the dominant proton source in the vegetation canopy. In organic horizons, dissociation of weak acids (bicarbonate and/or organic acids) and vegetation uptake of base cations were the dominant proton sources, and the net mineralization of base cations was the dominant proton sink. Atmospheric acid deposition was almost neutralized in the forest canopy and organic horizon. At both sites, weathering and/or ion exchange of base cations and protonation of weak acids (mainly bicarbonate) were the dominant proton sinks in the mineral soil. In both organic and mineral soil, internal proton sources (mainly vegetation uptake of base cations and dissociation of weak acids) exceeded external proton sources, indicating that acid deposition was not the main driving force of soil acidification in the studied forest ecosystems.     

Liming and fertilization of acid forest soil: Short-term effects on runoff from small catchments

Increased atmospheric deposition of strong acids and deposition of potentially acidifying compounds (e.g. ammonium) has caused a decline in pH and exchangeable base cations in forest soils in Sweden. In recent years, attention has been paid to liming of forest soil as a method to counteract the effects of acid deposition. Experiments with liming, fertilization and woodash treatment of acid forest soils started in 1984. The aim of this study was to determine the effects of low doses of lime (500 to 1500 kg ha^?1) in combination with N fertilizers on tree growth, nutritional status of trees as well as soil, and runoff chemistry. This paper describes the short term effects of liming and fertilization on runoff from ten small catchments in two regions in south Sweden. The effects of liming were small in both areas. In the catchments fertilized with N (NH₄NO₃), a substantial leakage of various N species appeared in runoff after treatment. The increased N output was dominated by nitrate. The excess leakage of N during 2 yr after fertilization was 25 and 13% as an average of the applied N in the two study areas. The mobile nitrate increased the base cations output via runoff with 10 to 100% during 1 yr after N treatment. The runoff of Al increased with 60 to 100% the first year in the fertilized catchments. Mobilization of cations was also influenced by ammonium, especially K that was exchanged by ammonium on the surface of the soil particles. The effects of woodash-treatment were small, however, sulfate in the ash leaked out following application and about 100% of the added sulfate was found in runoff during the first year.     

Liming and fertilization of acid forest soil: Short-term effects on runoff from small catchments

Increased atmospheric deposition of strong acids and deposition of potentially acidifying compounds (e.g. ammonium) has caused a decline in pH and exchangeable base cations in forest soils in Sweden. In recent years, attention has been paid to liming of forest soil as a method to counteract the effects of acid deposition. Experiments with liming, fertilization and woodash treatment of acid forest soils started in 1984. The aim of this study was to determine the effects of low doses of lime (500 to 1500 kg ha^–1) in combination with N fertilizers on tree growth, nutritional status of trees as well as soil, and runoff chemistry. This paper describes the short term effects of liming and fertilization on runoff from ten small catchments in two regions in south Sweden. The effects of liming were small in both areas. In the catchments fertilized with N (NH₄NO₃), a substantial leakage of various N species appeared in runoff after treatment. The increased N output was dominated by nitrate. The excess leakage of N during 2 yr after fertilization was 25 and 13% as an average of the applied N in the two study areas. The mobile nitrate increased the base cations output via runoff with 10 to 100% during 1 yr after N treatment. The runoff of Al increased with 60 to 1009, the first year in the fertilized catchments. Mobilization of cations was also influenced by ammonium, especially K that was exchanged by ammonium on the surface of the soil particles. The effects of woodash-treatment were small, however, sulfate in the ash leaked out following application and about 100% of the added sulfate was found in runoff during the first year.     

Buffer capacities of podzolic and peat gleyic podzolic soils to sulfuric and nitric acids

Soil samples from the main genetic horizons of pale podzolic and peat gleyic podzolic soils from the Central Forest Reserve were subjected to a continuous potentiometric titration by sulfuric and nitric acids. The sulfate sorption capacity was determined in soil mineral horizons. The buffer capacity of mineral horizons of both soils to sulfuric acid was found to be higher than that to the nitric acid. This is explained by the sorption of sulfates via the mechanism of ligand exchange with the release of hydroxyl groups from the surfaces of Fe and Al hydroxide particles and edge faces of clay crystallites. The buffer capacity of organic horizons of the pale podzolic soil to sulfuric acid proved to be higher than that to nitric acid; in organic horizons of the peat gleyic podzolic soil, the buffer capacity to sulfuric acid was lower than that to nitric acid. The reasons for this phenomenon have yet to be investigated.     

Tiefengradienten der Bodenversauerung

Depth gradients of soil acidification In dystric Cambisols, developed from diabas and clay schist/greywacke in the Sösemulde (Harz), the depth gradient of the acid/base status has been assessed by measuring pH and the composition of exchangeable cations. After the soil in the root zone has acidified to within the aluminum buffer range, a marked acidification front is formed below the rooting zone. Strong acids (protons, Mn, Al ions) are buffered completely above the acidification front. Long-term measurements of the input and output of acids and bases in nine forest ecosystems in NW-Germany show that the acid input due to acid deposition into soil horizons in the Al- or Al/Fe- buffer range appears almost quantitatively as output in the seepage water from these horizons. The kind of acid responsible for the soil acidification can be identified by the anion composition of the seepage water. The deep reaching acidification is traced back to acid deposition.     

Absorption spectra of humic acids

For the purpose of explaining the forming process of soil humic acids, the author determined the absorption spectra of various humic acids. From soils and peats which were pretreated with 5% HCl at 70°C for 30 minutes or from those which were not, humic acids were extracted by treating with 0.5% NaOH at boiling temperature for 30 minutes. In these humic acids, the one which is extracted after acid pretreatment is provisionally designated as SrL humic acid and the other as L humic acid. The supernatant alkaline solutions obtained by centrifuging the above mentioned extracts were acidified with hydrochloric acid, and precipitated humic acids were filtered and washed with water until Cl' free. Humic acids were dissolved in 0.1% NaOH and ultrafiltered using collodion membrane. The filtrates were acidified with hydrochloric acid and humic acids were collected by centrifuging, transferred on the filter paper, washed with dilute hydrochloric acid and water successively, then air-dried and pulverized.     

The Importance of Calcium Deposition in Assessing Impacts of Acid Deposition in China

The extensive use of coal as an energy carrier in China has led to high deposition of sulfur in a large part of the country. In the southern part of China large areas receive acid deposition, while in the northern part of the country the acidity of the emissions is neutralized by alkaline dust from the desert areas. In this paper we demonstrate the importance of knowing the sources and deposition patterns of base cations when assessing the effects of changes in sulfur emissions. Regional-scale data of both sulfur and calcium deposition from modeling and monitoring are combined in order to demonstrate how the acidity of deposition in China has changed historically and may change in the future. The importance of base cation deposition is also demonstrated using the dynamic acidification model MAGIC with input data from an intensive monitoring site outside Guiyang. It is not known what fraction of the deposited base cations is of natural origin and anthropogenic origin, respectively. The relative source strength varies greatly between regions. Future effects of emission changes are highly dependent on the relative reduction in sulfur and base cation emissions.