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To monitor recovery from acidification, water chemistry was sampled in 11 Dutch moorland pools from 1978 to 2018. Changes were assessed by visual inspection of time series and tested non-parametrically. As a net result of all inputs and outputs, the median sulphate and ammonium concentrations in the surface water dropped by about 90%. This was accompanied by increases in pH, acid neutralizing capacity, and dissolved organic matter, and decreased metals, particularly toxic aluminium. Decreases of ammonium and sulphate in the surface water are considerably higher than in deposition, indicating the importance of losses to sediments and the atmosphere. The changes were greatest in pools with relatively flat banks exposed to the air in extremely dry summers. After the extremely dry summer of 1976, the changes were dramatic due to acidification by oxidation of the reduced sulphur and nitrogen compounds stored in the moorland pool bottom. In later dry years, the changes in the pools with flat banks were less extreme, as the sulphur stock in the sediment was depleted by winterly discharge to groundwater. In pools with steep banks, the sulphur compounds are retained in the sediment and may cause eutrophication by the displacement of phosphorus from iron compounds. [ABSTRACT FROM AUTHOR]

Nitrogen deposition from air pollution is increasingly reaching alpine lakes where the addition of nitrate and ammonium to sensitive surface waters can cause acidification and/or eutrophication. Thirty years of sampling in the Wind River Range, WY, has shown some lakes increasing in nitrogen. We sought to (1) determine if nutrient concentrations in Deep Lake increase during snowmelt when atmospheric deposition is released from the snowpack and (2) assess if the sampling season, location, meteorological factors, and time of day samples are collected influence lake chemistry metrics, to inform monitoring. We analyzed water samples from the outlet of Deep Lake in peak snowmelt (June) and from the inlet, outlet, and middle of Deep Lake when the basin was snow free (August). In June, outlet samples were more acidic, and nitrogen content was three times August levels. Acid neutralizing capacity (ANC) declined with snowmelt. August inlet samples were higher in nutrients than outlet and mid-lake samples. Our results indicate that atmospheric pollution in the snowpack enters the lake with snowmelt. Although Deep Lake has not acidified, ANC levels indicate a risk of episodic acidification if nitrogen deposition continues to increase. When monitoring lakes at risk for episodic acidification, sampling during the late snowmelt pulse should be prioritized. Simplified sampling protocols may be used in some lakes, as epilimnion and outlet samples were nearly identical. The time of day and cloud cover did not affect lake chemistry, while wind speed and precipitation weakly increased August ANC and June pH, respectively. [ABSTRACT FROM AUTHOR]

This paper compares lake chemistry in the Adirondack region of New York measured by the Temporally Integrated Monitoring of Ecosystems (TIME) and Adirondack Long-Term Monitoring (ALTM) programs by examining the data from six lakes common to both programs. Both programs were initiated in the early 1990s to track the efficacy of emission reduction policies and to assess the full impacts of acid deposition on surface water chemistry. They now serve to inform on the emerging chemical recovery of these waters. The Adirondack TIME program utilizes a probability-based approach to assess chronic acidification in a population of lakes using one summer sample per year. The ALTM attempts to track changes in both chronic and episodic acidification across a gradient of lake types using monthly samples. The ALTM project has two important attributes that contrast with the TIME program in the Adirondacks: higher temporal resolution (monthly versus once during the summer or fall) and speciation of aluminum. In particular, the ALTM program provides inorganic monomeric aluminum (Al), the fraction of Al that is most toxic. The monthly sampling of the ALTM program includes the spring snowmelt period when acid-neutralizing capacity and pH are near their lowest and Al levels are near their highest. We compare chemistry trends (1992-2008) for sulfate, nitrate, base cations, dissolved organic carbon, hydrogen ion, acid neutralizing capacity, and Al for the six lakes common to both programs. We also compare relatively high springtime Al concentrations from the ALTM with relatively low summertime total Al concentrations from the TIME, showing that the ALTM program provides a more biologically relevant indicator of the effects of acid deposition, illustrating the value of the complementary monitoring efforts in the Adirondack region. [ABSTRACT FROM AUTHOR]

pH monitoring data for public water bodies in Niigata and Gifu prefectures in central Japan were tested by the nonparametric seasonal Mann–Kendall method to evaluate long-term acidification. A significant long-term declining trend in river water pH was found in several watersheds in Niigata and Gifu prefectures. In Niigata, the declining trend was observed only in areas receiving drainage from granitic rocks, and the acid neutralizing capacity of the river waters was in fact low in those areas. In Gifu, a declining trend was observed in some remote watersheds, where there was no clear relationship between the geology and the long-term trends. Since Niigata and Gifu receive the highest level of acid loading from the atmosphere in Japan, river water acidification in several watersheds may be attributable to the effects of the acid deposition. Other factors, such as hot spring drainage, changes in land use, and natural sea salt deposition, cannot adequately explain the acidification phenomena observed in this study. [ABSTRACT FROM AUTHOR]

In the present study, different leaching tests were applied on well-characterised samples in order to obtain information on the potential mobility of heavy metals and arsenic. The information deduced from the different methods was compared and evaluated. Besides the comparison of heavy metal release in cascade-, column- and pHstat leaching tests, attention was also paid to the assessment of release kinetics during leaching tests and to the mathematical modelling of leaching behaviour. The aim of this study was to understand the origin of possible discrepancies between the results of different leaching tests. The compatibility of the results of different leaching tests is, besides the inherent differences between methods (single batch tests versus dynamic leaching tests, the duration of the tests, liquid/solid ( L/ S) ratio,...) to a major extent determined by key-factors such as pH and redox potential. Depending on soil and sediment properties (e.g. acid neutralizing capacity (ANC)) these ‘key-factors’ varied during and at the end of extractions and leaching tests, even when the initial test conditions (e.g. the pH of the reagent) were equal for all test cases. During cascade- and column leaching tests, pH (which is initially 4) will mostly increase, but the extent of this pH-increase mainly depends on the acid neutralizing capacity of the sample. Therefore, measuring the pH of all leachates that are collected during these tests is mandatory for the interpretation of the results. Moreover, the monitoring of other variables such as DOC, anions and major elements can give indications on the reactions that are responsible for the release of elements (e.g. the dissolution of organic matter) and greatly improve the interpretation of the results. [ABSTRACT FROM AUTHOR]

A geologic classification scheme was combined with elevation to test hypotheses regarding watershed sensitivity to acidic deposition using available regional spatial data and to delimit a high-interest area for streamwater acidification sensitivity within the Southern Appalachian Mountains region. It covered only 28% of the region, and yet included almost all known streams that have low acid neutralizing capacity (ANC ≤20 μeq l−1) or that are acidic (ANC ≤0). The five-class geologic classification scheme was developed based on recent lithologic maps and streamwater chemistry data for 909 sites. The vast majority of the sampled streams that had ANC ≤20 μeq l−1 and that were totally underlainby a single geologic sensitivity class occurred in the siliceous class, which is represented by such lithologies as sandstone and quartzite. Streamwater acid-base chemistry throughout the region was also found to be associated with a number of watershed features that were mapped for the entire region, in addition to lithology and elevation, including ecoregion, physiographic province, soils type, forest type and watershed area. Logistic regression was used to model the presence/absence of acid-sensitive streams throughout the region. [ABSTRACT FROM AUTHOR]

We adapted a reduced-form model, built to predict the aquatic effects of alternative nitrogen and sulfur emissions scenarios on Adirondack lakes, New York, for use on high elevation lakes of Maine (HELM), USA. The Tracking and Analysis Framework (TAF) model was originally designed to evaluate the biotic, economic, and health effects of acid deposition. The TAF model developed in our study was used to assess the biotic effects of different levels of sulfate deposition resulting from alternative emissions scenarios. The aquatic portion of the model is based on a lumped-parameter watershed chemistry model, MAGIC (Model of Acidification of Groundwater in Catchments). The original TAF model was built by calibrating MAGIC to 33 lakes in the Adirondack Mountains. We calibrated MAGIC to 78 HELM lakes, and built reduced-form models from these MAGIC predictions. We evaluated TAF predictions of acid neutralizing capacity (ANC), a fish acid stress index (ASI), and the probability of fish presence in 2030 for four different SO2 emissions-reduction scenarios. The most dramatic emissions reduction scenario produced only modest increases in mean ANC (16.8 μeq/L ± 7.9 μeq/L) and slight increases in mean predicted probability of presence of acid-sensitive fish (0.07± 0.09) across all lakes. However, a small number of lakes were predicted to have more substantial increases in ANC and improvements in other conditions for acid-sensitive fish. Our results reflect the reality that many of the high elevation lakes of Maine historically had low ANC and that some were even acidic in pre-industrial times. Thus, ’recovery’ for most of the high elevation lakes of Maine will be modest under any scenario of reduced acidic deposition. [ABSTRACT FROM AUTHOR]

Snowcover surveys were carried out in Hokkaido, northern Japan. Snowpack samples were collected using a steel pipe at 80 sites in 1988, 69 sites in 1992, and 66 sites in 1996 and 2000 during the time when the water equivalents of the snowcover are the greatest. Spatial distribution maps of water equivalents and of the concentrations and the accumulated amounts of hydrogen, non-sea-salt sulfate and non-sea-salt calcium ion of the snowcover drawn by Kriging method are discussed. The distribution maps show that water equivalents and the accumulated amounts of hydrogen and non-sea-salt sulfate in all the sample years were largest in the Japan Sea region, as were the ion concentrations of hydrogen and non-sea-salt sulfate. It was estimated this was caused by air pollutants transported from a great distance. The ratio of areas below pH 5.0 increased temporally from 1988 (20%) to 1992, 1996 and 2000 (66–80%). This trend was estimated to be affected by a decline of non-sea-salt calcium concentrations derived from alkaline road dust. In addition, the effect of snowcover components was assessed by comparison between the acid loads of the snowcover and the acid neutralizing capacity of lake water. We found that lakes in the middle of the Japan Sea coast have the potential to be acidified by snowmelt. [ABSTRACT FROM AUTHOR]

The essential parameters needed for the calculation of critical load of sulfur, CL(S), are base cation weathering rate, base cation uptake, acid neutralizing capacity leaching and base cation deposition. These parameters are estimated and mapped for the most area of terrestrial ecosystems of Thailand using data of national data soil survey. The values of CL(S) range from <200 to 2,225 eq.ha-1yr-1 and about 70% of terrestrial ecosystems are characterized by low values (<200 eq.ha-yr-1). These CL values reflect the sensitivity of Thai ecosystems to sulfur deposition. [ABSTRACT FROM AUTHOR]

Concern about acidification in upland areas has brought about the need to model the stream hydrochemical response to deposition and land-use changes and calculate critical loads. Application of dynamic models such as MAGIC are preferable to steady-state methods, since they are able to produce an estimate of the time scale required to meet some water chemistry target given a reduction in acid deposition. These models typically consider annual changes in stream chemistry at one point. However, in order to protect biota from 'acid episodes', quantification of temporal variability needs to encompass event responses; in addition spatial variability across the catchment also needs to be considered. In this paper, modelling of both spatial and temporal variability is combined in a new framework which enables quantification of catchment hydrochemical variability in time and space. Both low and high flow hydro-chemical variability are quantified in terms of statistical distributions of ANC (Acid Neutralisation Capacity). These are then input as stochastic variables to an EMMA (End-Member Mixing Analysis) model which accounts for temporal variability and ANC is hence predicted as a function of time and space across the whole catchment using Monte-Carlo simulation. The method is linked to MAGIC to predict future scenarios and may be used by iteration to calculate critical loads. The model is applied to the headwaters of the River Severn at Plynlimon, Wales, to demonstrate its capabilities. [ABSTRACT FROM AUTHOR]

This study is based on research of throughfall formation and soil chemistry processes. Through the experimental verification of the cation exchange part of the simulation model; making use of results of the flux of acid deposition on the forest and the chemical weathering of soil mineral, we predicted the future soil acidification. The result indicated that chemical weathering occupies the important portion of acid neutralization capacity of the soil and that significant soil acidification will not occur in this field within 40 years, even if the present acid load continues in the future. [ABSTRACT FROM AUTHOR]

The sublittoral chironomid fauna of 22 lakes in Killarney Park, Ontario, Canada were examined for their response to different levels of acidification. Included in the analysis were naturally acidic lakes, lakes acidified by atmospheric deposition but now recovering, and unacidified circumneutral lakes. pH in the study lakes ranged from 4.6 to 7.7. No correlation was found between species richness and pH, nor between abundance and pH. Acid neutralizing capacity (ANC), the temperature at the sampling depth, pH, and dissolved organic carbon were the variables contributing significantly in a canonical correspondence analysis of the abundance data. ANC was the most important variable in describing the chironomid community, accounting for about 9% of the variance in the species data. This study is the first step in an effort to model the changes in the chironomid community of recovering acidified lakes and the results suggest that ANC may be an important predictor variable. [ABSTRACT FROM AUTHOR]

Chemicals leached from concrete are an important way that urban stormwater can influence water quality. In this study, we evaluated the weathering properties of sidewalk samples and tested how carbonation (exposure to elevated levels of gaseous CO2) can be used to simulate natural aging of concrete. The experiments focused on acid neutralizing capacity (ANC), which is known to be released by concrete in large amounts, and Cr(VI), because of its established carcinogenicity and prevalence in concrete. Chemical weathering of crushed sidewalk samples was measured with upflow recirculating columns carrying simulated acid rain. The weathering rate of ANC from four different samples was found to decrease after 1 week of exposure to a 5% carbon dioxide atmosphere and to remain constant thereafter through 8 weeks of carbonation treatment. In contrast, weathering of chromium (VI) increased after exposure to a 5% carbon dioxide atmosphere for 1 week, though it also remained stable from then through 8 weeks of carbonation. Almost all ions approached steady state after 2.5 h in the recirculation columns irrespective of carbonation time. The main contributor of ANC was Ca2+ ion, though this was partly balanced by an unexpectedly high amount of SO42−. A notable exception to the temporal leaching pattern was largely un-ionized Si, which continued to increase in concentration for at least 3 days of recirculation. Si levels were also higher than is generally observed for aluminosilicate weathering in small watersheds, a novel finding. [ABSTRACT FROM AUTHOR]

Soil acidification impacts arising from depositions of industrial air emissions may become a serious environmental concern. Currently, inthe literature quantitative mechanistic modeling and the experimental acid neutralizing capacity (ANC) approach and a qualitative evaluation approach classifying soils into various levels of sensitivity to acid additions have been reported to assess the long-term soil acidification impacts due to industrial air emissions. Another alternative quantitative approach proposed by this study is the geochemical modeling approach that can be used to simulate an ANC curve based on relevant soil chemistry data by calculating the equilibrium distributions of chemical species in the soil solution according to the specified geochemical processes. The purpose of this study was essentially to illustrate the potential applications and practical utility of the proposed geochemical modeling approach to assessing soil acidification impacts due to industrial air emissions. The application of the geochemical modeling approach was illustrated by comparisons of the experimental and simulated ANC curves for a calcareous and a noncalcareous soil representing insensitive and sensitive soil cases, respectively. Results obtained from these comparisons reveal that, in terms of producing the ANC curve for the soil solution, the geochemical modeling approach seems to perform well and produce more reliable results for calcareous soil than for noncalcareous soil. However, the approach can also be used for noncalcareous soils when the air emission rates are low and may need further testing with additional measured data for a wide range of soils other than those presented in this study. [ABSTRACT FROM AUTHOR]