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The paper presents the influence of acid neutralization capacity in industrial waste samples as a decision indicator. For the analysis of the acid neutralization capacity, six samples of wastes from different sectors of activity were subjected. A successful method that can be applied to determine the properties of waste is acidneutralizing capacity. The acid-neutralizing capacity was evaluated with HCl 1 N by neutralizing the excess with NaOH 0.5 N after 15 min stirring. From the results obtained it is found that the acid neutralization capacity can provide essential information for the subsequent management of the waste.

Many Chinese croplands are suffering from soil acidification, defined as a decrease in soil acid neutralizing capacity (ANC), due to over-application of nitrogen (N) fertilizer and removal of base cations (BCs) in crop harvest. The contribution of fertilization and harvesting on soil acidification rates for different cropping systems is, however, seldom quantified under field conditions. Here, field experiments were conducted on a moderately acid silty clay soil in southwest China to quantify proton (H+) production rates under three fertilization management regimes, including control (non-N), optimized fertilization and farmers’ practices (i.e. over fertilization), by measuring the inputs and outputs of major element in three cropping systems, i.e. rice-fallow, rice-wheat and maize-wheat. The maize-wheat cropping system had the highest proton production rates (2.3–10.2 kmolc H+ ha−1 yr−1), followed by rice-fallow (3.2–4.6 kmolc H+ ha−1 yr−1) and rice-wheat (2.2–4.5 kmolc H+ ha−1 yr−1) systems. Crop removal, dominated by straw removal, was the main driver of proton production in all three cropping systems, contributing over 50% of the total H+ production. Compared to the control, N fertilizer application enhanced soil acidification rates among three cropping systems, but had no significant effects on H+ production per kg grain in the rice-fallow and rice-wheat systems. The same was true for the maize-wheat system in case of optimized fertilization, but over fertilization increased both soil acidification rate and H+ production per kg grain, while grain yield was comparable to that with optimized fertilization. The change in soil ANC was dominated by accumulation of SO42− (leading to potential soil acidification) that was mainly added to the soil with superphosphate containing high concentrations of both Ca2+ and SO42− sometimes even causing an increase in the base cation pool, despite BC crop removal. The low contribution of N transformation processes to the total H+ production (3–47%) was due to high denitrification in this specific soil. The soil pH and base saturation did not change significantly among the three fertilization management regimes, largely due to the large BCs pools in the soil. Although the common farmers’ practice does not strongly increase proton production in rice-fallow and rice-wheat systems, it still implies a waste of N fertilizer as the excess N input is either enhancing straw production or lost to air in this silty clay soil. Hence, optimized fertilization and localized BCs-rich straw return are suggested to reduce costs of N fertilizer without yield losses and mitigate soil acidification in those systems.

Mineral trace elements (MTE) constitute an environmental restriction on the recycling of municipal solid waste incineration-bottom ash (MSWI-BA). The study of the speciation of MTE and the factors that control their release allows to predict their behavior under different environmental conditions and, consequently, suggest different actions to expand the management of MSWI-BA.A geochemical modeling led to a better understanding of the speciation of MTE. In this study, target elements were barium, copper, lead, nickel and zinc and the factors that control their release were identified.The results show that the leaching of metals as a function of pH mainly depends on the mineralogical phases. On the other hand, the organic matter has an influence in the leaching of MTE (for Ni, Cu and Pb notably); organic matter presents adsorbent or complexation properties. Les éléments traces métalliques (ETM) constituent une restriction environnementale pour le recyclage des mâchefers d'incinération des déchets non dangereux (MIDND). L'étude de la spéciation des ETM et des facteurs qui contrôlent leur mobilité permet de prédire le comportement des MIDND dans différentes conditions environnementales et de suggérer ensuite des actions pour élargir leur gestion. Une modélisation géochimique des MIDND a permis de mieux comprendre la spéciation des ETM. Dans cette étude, les éléments ciblés étaient le baryum, le cuivre, le plomb, le nickel et le zinc et les facteurs qui régissent leur mobilité ont été définis. Les résultats montrent que la lixiviation des métaux en fonction du pH dépend principalement des phases minéralogiques ; la matière organique joue également un rôle en tant qu'adsorbant ou complexant dans la lixiviation de certains éléments (Ni, Cu et Pb, notamment). Mots-clés Mâchefers d'incinération des déchets non dangereux (MIDND), éléments traces métalliques, capacité de neutralisation acide, modélisation géochimique, PhreeqCI.

Modeling studies project that in the future surface waters in the northeast US will continue to recover from acidification over decades following reductions in atmospheric sulfur dioxide and nitrogen oxides emissions. However, these studies generally assume stationary climatic conditions over the simulation period and ignore the linkages between soil and surface water recovery from acid deposition and changing climate, despite fundamental impacts to watershed processes and comparable time scales for both phenomena. In this study, the integrated biogeochemical model PnET-BGC was applied to two montane forest watersheds in the Adirondack region of New York, USA to evaluate the recovery of surface waters from historical acidification in response to possible future changes in climate and atmospheric sulfur and nitrogen deposition. Statistically downscaled climate scenarios on average project warmer temperatures and greater precipitation for the Adirondack by the end of the century. Model simulations suggest under constant climate, acid-sensitive Buck Creek would gain 12.8 μeq L−1 of acid neutralizing capacity (ANC) by 2100 from large reductions in deposition, whereas acid insensitive Archer Creek is projected to gain 7.9 μeq L−1 of ANC. However, climate change could limit those improvements in acid-base status. Under climate change, a negative offset relative to the ANC increases with no climate change are projected for both streams by 2100. In acid-insensitive Archer Creek the negative offset (−8.5 μeq L−1) was large enough that ANC is projected to decrease by −0.6 μeq L−1, whereas in acid-sensitive Buck Creek, the negative offset (−0.4 μeq L−1) resulted in a slight decline of the projected future ANC increase to 12.4 μeq L−1. Calculated target loads for 2150 for both sites decreased when future climate change was considered in model simulations, which suggests further reductions in acid deposition may be necessary to restore ecosystem structure and function under a changing climate.

Acid deposition, resulting from the atmospheric transport of acidifying compounds emitted during the combustion of fossil fuels, has historically resulted in stream acidification in many headwater streams in the eastern United States, including streams in Shenandoah National Park (SHEN). Though restrictions on these emissions were established by an amendment to the Clean Air Act in 1990, reductions in stream acidification have not been observed in all regions of SHEN due to variations in the geological composition of SHEN watersheds. Before the implementation of these restrictions, fish assemblages were strongly controlled by a stream’s acid neutralizing capacity (ANC), which is the ability of a watershed to buffer acid inputs. This study investigated changes in the relationship between fish assemblages and ANC within SHEN 21 years after implementation of more stringent restrictions on the emission of sulfur and nitrogen oxides in 1995. Results indicated that recovery trends in water chemistry were observed in some SHEN watersheds; however, fish species richness and total fish biomass continue to be influenced by the legacy of acid deposition in acid sensitive watersheds. Temporal trend analysis indicated little change in ANC within acid sensitive watersheds and minor decreases in stream sulfate concentrations. These findings indicate a persistent impact from previously deposited sulfur oxides and the continued influence of these compounds on fish assemblages within SHEN. Though no further loss of fish species, and in some cases, increases in species richness, suggest the early stages of recovery, many SHEN streams remain as susceptible to acidification as they were over two decades ago, highlighting the need for continued regulation of acidifying emissions and conservation efforts in headwater streams.

Acid Mine Drainage (AMD) is produced when sulfide-bearing material is exposed to oxygen and water. The mine may accelerate this natural reaction due to the wide and rapid exposure of sulfide minerals. Although economical ores are considered environmental pollutants, there are several elements that act as acid neutralizing capacity (ANC) mineral are associated with the ore, especially silicate minerals. Currently, PT Agincourt Resources Martabe has only relying on the use of carbonates mineral groups to handle the AMD issue. In fact, the geological condition in this area is formed of typically alumina-rich and alkaline minerals which are capable to neutralize the AMD as well. The aim of this study is to determine ANC minerals from the rock formations that has impact to neutralize the AMD in Barani Pit. The methods are geological field observation, mineral determination using spectral analysis, and assay analysis that provides data to sort the recommended ANC minerals. The ANC minerals from the rock formations and wastes within Barani Pit, other than calcite, are muscovite, illite, smectite, kaolinite, dickite and gypsum. The knowledge about these alternative ANC minerals might give contribution to reduce and solve the risk of acid mine drainage polluting the environment.

A bark beetle attack in a Norway spruce forest in southwestern Sweden killed most trees, which however mostly remained standing, and caused elevated nitrate concentrations and subsequent acidification in the soil water. Long-term monitoring showed very low nitrate concentrations in the soil water before the bark beetle attack. High nitrate concentrations remained throughout five years after the initiation of the bark beetle attack until the monitoring was terminated. The increased nitrate concentrations in the soil water were accompanied by a decrease in both pH and the acid neutralizing capacity, ANC. The significance for future nitrogen and acidity leakage to ground- and surface waters is discussed in relation to the expected future increase in the frequencies of bark beetle attacks in boreal and northern temperate forests.

Mountain lakes are usually sensitive to the effects of global and regional environmental changes. Since the second half of the 20th century, surface-water acidification has become a significant ecological problem, and many lakes in Europe and North America have anthropogenically acidified. Additionally, following reduction in emissions of sulfur (S) and nitrogen (N) compounds, recovery from acidification has been observed in many lakes. In this study, we used changes in diatom communities to reconstruct the pH histories based on changes recorded in nine Tatra lakes (Western Carpathians, Poland) since approximately 1850 AD. Overall, results indicate that acidic precipitation had little influence on lake-water pH in the Tatra Mountain lakes. Changes in diatom-inferred pH (DI-pH) generally were small and showed little evidence of acidification during the time of the highest air pollution (since the 1960s), and have shown little change since the reduction of acidic deposition since the 1990s. Lakes that showed some evidence of acidification included dystrophic lakes with low acid neutralizing capacity. However, as illustrated by the PCA trajectories of the diatom assemblages, the majority of the lakes currently contain diatom assemblages that are unlike the diatom floras that existed ca. 1850.

Reconciliation of paleolimnology inference models with hindcasts from mechanistic water column models aided the reconstruction of past relationships for total phosphorus/dissolved oxygen and acid neutralizing capacity/pH in highly polluted lake ecosystems in New York State. Pre-disturbance Onondaga Lake, Syracuse, NY, was shown to have experienced seasonal hypolimnetic anoxia even under oligotrophic (

Acidic deposition used to cause severe surface water acidification in Europe and the North America, but no damage of surface water acidification was reported under continuous heavy acid deposition in China. We present the first detailed study on regional surface water acidification in southern and northeastern China based on a survey of 255 forested headwater streams, which were investigated during 2010–2015 to explore the status and mechanism of surface water acidification. South China has a subtropical climate with high acid deposition, whereas northeast China is located in a cold temperature zone with relatively low acid deposition. High pH and acid neutralizing capacity (ANC) were observed for almost all of the streams, indicating that surface water acidification may not be a serious regional issue in China both at present and in the future. In northeast China, where soil types are similar in low weathering rate to those in Northern Europe and North America, the ANC of surface waters was lower than that in South China, indicating a higher acid-sensitivity of the surface water. In comparison, the high pH and ANC of streams in southwest China resulted from high soil weathering and atmospheric calcium (Ca) deposition, despite elevated atmospheric acid inputs due to the high sulfur (S) and nitrogen (N) deposition. Comparison of stream nitrate (NO3−) and sulfate (SO42 −) concentrations with modeled N and S deposition showed significant N and possible S sinks in the catchments in south China, probably due to denitrification of NO3− in groundwater discharge zone and SO42 − adsorption by acid soils respectively, which may also buffer the acidifying effect of S and N depositions. It seems that considerable NO3− leaching to stream waters does not occur in China unless N deposition is higher than 1.8 keq·ha− 1·yr− 1 (2.50 g N·m− 2·yr− 1) (or greater values in certain regions).

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.

Este artículo contiene 13 páginas, 6 figuras, 2 tablas., Diatom assemblages are used widely as indicators of environmental conditions. They have been particularly useful in the assessment of some acute environmental problems such as water acidification, eutrophication and salinisation. High mountain lakes are currently a research focus as sentinels of global change, predominantly of long-distance atmospheric pollution and climate warming. The diatom assemblages in these lakes are extremely rich, and the sediment record provides short and long historical perspectives of the changes. We investigated the relative sensitivity of diatoms to the main environmental gradients found in mountain lakes and evaluated the strength and uncertainties for predicting simultaneously several environmental variables associated with these gradients based on a survey of 83 lakes in the Pyrenees. Variables related to the ionic composition and acid-base balance (calcium*, acid neutralizing capacity*, magnesium, sodium, and sulphates), trophic conditions (total phosphorus* and dissolved organic carbon) and physical factors (water temperature*, irradiance at the lake bottom*, and macrophyte cover) explained independently the variation in the diatomassemblages. However, the assemblage predictive capacity of these variables- tested by developing transfer functions (Weighted Averaging- Partial Least Squares) - was only acceptable for a subset of the variables (*). The spatial autocorrelation of the environmental variables had no influence on the performance of the transfer functions except forwater temperature,which is highly dependent on altitude. Our results indicate that diatom assemblages have great potential for assessments of multiple environmental variables in mountain lakes and, consequently, in applications of global change surveillance., This study was funded by the EU EMERGE Programme [EVK1-CT- 1999-00032], the Spanish Government LACUS [CGL2013-45348-P], CUL-PA [Parques Nacionales 998/2013] and TRANSFER [CGL2016- 80124-C2-1-P]. CRR was supported by a PhD scholarship from the Departamento Administrativo de Ciencia, Tecnología e Innovación de Colombia [COLCIENCIAS-ICETEX-LASPAU, 070-2007] and the Pontificia Universidad Javeriana [DJE-025-2007], and by a Pontificia Universidad Javeriana travel grant [PPTA 8084].

Acidic deposition is comprised of sulfuric and nitric acids, and ammonium derived from atmospheric emissions of sulfur dioxide, nitrogen oxides, and ammonia, respectively. These compounds are released to the atmosphere largely by the burning of fossil fuels and agricultural activities. Atmospheric deposition delivers acids and acidifying compounds to the Earth’s surface. The adverse ecological effects of acidic deposition on forests, streams, and lakes largely occur in eastern North America, northern and central Europe, and southwestern China. Acidic deposition has altered, and continues to alter, forest soil by accelerating the leaching of calcium and magnesium and increasing concentrations of dissolved inorganic aluminum in soil waters. At high concentrations, dissolved inorganic aluminum can hinder the uptake of water and essential nutrients by tree roots. The alteration of soils by acid deposition has serious consequences for acid-sensitive forest ecosystems. Soils that are compromised by acidic deposition are less able to neutralize additional inputs of strong acids, and provide poorer growing conditions for plants and delay the recovery of surface waters. Acidic deposition has impaired, and continues to impair, the water quality of lakes and streams in eastern North America and Europe in three important ways: lowering pH levels (i.e., increasing the acidity); decreasing acid-neutralizing capacity; and increasing aluminum concentrations. Many surface waters in acid-sensitive regions impacted by acidic deposition exhibit chronic and/or episodic (i.e., short-term) acidification. Moreover, elevated concentrations of dissolved inorganic aluminum have been measured in acid-impacted surface waters. High concentrations of aluminum and increased acidity have reduced the species diversity and abundance of aquatic life in many lakes and streams draining acid-sensitive regions. Fish have received the most attention to date, but entire food webs are often negatively affected. For example, in a survey of lakes in the Adirondack region of New York, 346 lakes (24% of the total) did not contain fish. These fishless lakes had significantly lower pH and higher concentrations of dissolved inorganic aluminum when compared to those lakes with fish.

Reductions in acidic deposition following the 1990 Amendments to the Clean Air Act have led to improvements in the acid/base status of many freshwater bodies in the eastern United States, but such recovery has not been as widespread in Virginia mountain streams. In the current analysis, water chemistry trends are determined for 63 streams within Shenandoah National Park, Virginia, and surrounding national forests, where water samples have been collected on a quarterly basis from 1987 to 2019. Over this timeframe, a majority of the most acid-sensitive streams – those with watersheds underlain by siliciclastic bedrock – have experienced reductions in acid neutralizing capacity (ANC). This outcome, which differs from the modest recovery predicted by earlier modeling studies, is likely due to further depletion of soil base cations and perhaps increases in organic acids. Meanwhile, stream water pH has increased for all watershed bedrock types, averaging between 0.05 and 0.10 pH units per decade. High-flow sampling was conducted at three sites from 1992 to 2019, revealing an assessment of episodic acidification that is more encouraging than that of chronic acidification. For two of these sites, pH during high-flow conditions increased much more rapidly than pH during low-flow conditions. Steep reductions in sulfur deposition over the three decades since the 1990 Amendments have led to a “flushing” of sulfate from shallow soils, which has contributed to the improved acid/base status during episodes of high flow. The findings suggest that continued low acidic deposition rates will lead to further improvements in stream water quality, with the timescales of recovery dependent upon bedrock geology of the watersheds.

Decades of acidic deposition have adversely affected aquatic and terrestrial ecosystems in acid-sensitive watersheds in parts of the eastern United States. The national Acid Rain Program (Title IV of the 1990 Clean Air Act Amendments - CAAA) helped reduce emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) and resulted in sharp decreases in the acidity of atmospheric deposition. The decrease in acidic deposition produced a steady decline in the acidity of streams in many poorly buffered waters across the western Adirondacks and parts of the Catskill Mountains of New York. Until recently, however, there has been little evidence of biological recovery in most acid-sensitive streams in both regions. Long-term deposition and stream-chemistry records and fish-community data from quantitative surveys done during 1991–93 and again during 2012–19 at 13 sites in the upper Neversink River and its tributaries were evaluated to determine if chemical and biological recovery were evident in this Catskill Mountain watershed and if they could be linked to regional declines in acidic deposition. Between 1991 and 2019, large decreases in sulfate and nitrate deposition in the basin mirrored declines in total nationwide SO2 and NOx emissions. There were corresponding decreases in sulfate and nitrate concentrations in deposition at a National Trends Network station at Frost Valley (NY68) and coincident declines in sulfate concentrations at four long-term monitoring sites in the Neversink River watershed. Mean acid neutralizing capacity and pH increased and inorganic aluminum (Ali) concentrations from routine summertime samples decreased significantly at most moderately to severely acidified sites between the two study periods. Richness, density, and biomass of fish communities increased at most sites, while the density and biomass of brook trout Salvelinus fontinalis populations increased at fewer sites that were undergoing chemical recovery. Although recovery is far from complete, trends in deposition chemistry, water quality, and fish assemblages in streams of the upper Neversink watershed indicate that the 1990 CAAA is having positive impacts on aquatic ecosystems in the Catskill Mountain region, New York.

The results of long-term studies (1990–2013) of dynamics of the main hydrochemical indices of the subarctic Shuonijavr Lake located in the zone of airborne pollution from a metallurgical plant have been considered. The following facts have been revealed: significant increase of alkalinity and acid neutralizing capacity (ANC) of the lake water; reduction in the range of seasonal fluctuations of ph and alkalinity; reduction of 2 4 SO − in the lake water during the observation period as a result of reducing the acid load due to the decrease of SO2 emission. Despite the stabilization of the lake water ANC the pollution indicators in six elements of polluters foreground for the region remain high values. Ключевые слова: Субарктика, озеро, закисление, кислотонейтрализующая способность, тяжелые металлы, формы металлов, восстановление.

During recent decades, increasing anthropogenic activities have affected natural ionic composition, including the strongest and most common relationship between ionic concentrations in the majority of natural global freshwaters, i.e., the Ca2+-ANC (acid neutralizing capacity) equilibrium. Using long-term monitoring data and MAGIC modelling, we evaluated effects of major present environmental stressors (synthetic fertilizers, liming, acidic deposition, forest disturbances, and climate change) on the Ca2+-ANC equilibrium. We evaluated the effects for three different types of terrestrial ecosystems, a circumneutral lowland agricultural catchment, two acid sensitive mountain forest catchments differing in forest health, and one acid sensitive alpine catchment. All catchments are in a region with the world-largest changes in fertilizing rates and acidic deposition in the 20th century, with increasing impacts until the late 1980s, and their subsequent abrupt, dramatic decreases. These strong changes resulted in a substantial disruption, followed by continuing re-establishment of the Ca2+-ANC relationship in all study waters. The shape of the disruption and the following re-establishment of its new value were dependent on the intensity, duration, and combination of stressors, as well as on catchment characteristics (bedrock composition, soil amount and composition, vegetation status, and hydrology). We conclude that a new equilibrium may deviate from its natural value due to the (1) legacy of fertilizing, acidic deposition and liming, affecting the soil Ca2+ pools, (2) forest disturbances and management practices, and (3) climate change.

Atmospheric wet deposition of base cations (BCs) plays a significant role in providing plant nutrients and buffering acidification. However, the temporal dynamic of wet BC deposition in China during the past two decades remain unclear. Here, we used long-term monitoring and literature data since 2000 to assess the temporal dynamics (seasonal and inter-annual variation), spatial patterns, main influencing factors, source apportionment, and capacity to neutralize the acidity of wet BC depositions at site, regional, and national scales. The results showed that total wet deposition of BCs was, on average, 2.12 keq ha−1 yr−1, where Ca2+ accounted for 65.57% of the total deposition, followed by Na+ (13.21%), Mg2+ (13.68%), and K+ (7.55%). Qinghai-Tibet had significantly lower BC deposition fluxes than northern, southern, and central China, as well as Inner Mongolia. Exchangeable BCs in soil, PM10 in the atmosphere, energy consumption, and cement production are significantly related to wet BC deposition, which account for 79.17% of the variation in the spatial deposition of BC. Influenced by the strategies to control acid rain and particulate matter in China, interannual variations showed a stabilization trend after a continuous decline from 2000 to 2017, which can be explained by inter-annual changes in PM10, energy consumption and cement production. Statistical methods confirmed that 45.95% of wet BC deposition was derived from crustal contributions, 27.78% from sea salt sources, and 26.27% from anthropogenic sources. Furthermore, we found that wet deposition of BCs neutralized 84.85% of the acidity due to NO3− and SO42− depositions. Under the emissions reduction strategy, there has been a decrease in the deposition of BC. However, SO42− and NO3− depositions decreased faster than BC deposition, which buffered a higher proportion of acidic depositions. Our findings contribute to an improved understanding of wet BC deposition in China, an evaluation of their capacity to neutralize acidity, and important parameters for acidification models.

Guwahati, the largest urban corridor of Northeast India, is one of the United Nations Educational, Scientific and Cultural Organization (UNESCO) world heritage sites and one of the 200 eco-regions in the world. The present study investigates the characterization of chemical components and sources of precipitation samples collected in Guwahati during June 2016–June 2017. Acidic rain events occurred throughout the year, with a frequency of 64% and 87% during monsoon and non-monsoon seasons, respectively. Higher contributions of the acidic species (SO42− and NO3−) coinciding with poor neutralizing capacity of crustal species (Ca2+, K+ and Mg2+) led to acid rain in this region. Isotope analysis (δ18O and δD) indicated that monsoonal and non-monsoonal rains were of marine and non-marine origins, respectively. This is further supported by the back trajectory analysis as majority of the individual rain events during d-excess 10‰ i.e. non-monsoon, the trajectories originated from water-inland. The enrichment factors (EF) for Pb, Zn, Co and Cu were >5, indicating the dominance of anthropogenic sources in this region. The Positive Matrix Factorization (PMF) along with isotope analysis identified marine (40%) as the major source in monsoon and industrial emissions (28%) in non-monsoon, indicating rainwater evaporation is more of ocean and continental origin during monsoon and non-monsoons, respectively. This study suggests the need of further studies and implementation of stringent anthropogenic regulations not only in local but also at regional and global scale, in this acid rain prone region.

Municipal solid waste incineration fly ash is directly landfilled after solidification in the industry. The rapid evaluation of contaminant leaching is required before the landfill of fly ash. In order to reduce the time to evaluate the effect of solidification, a set of rapid evaluation method was developed through the determination of characteristic index, heavy metal leaching analysis, principal component analysis, and mathematical model construction. It was found that f-CaO, acid neutralizing capacity, pH and soluble calcium were negatively correlated with heavy metal leaching. The soluble chlorine was positively correlated with heavy metal leaching. The effect of each feature indicators on heavy metal leaching was evaluated using principal component analysis and mathematical analysis software R.3.4.4. Furthermore, R.3.4.4 was used to detect the optimal model and the excess probability formula by stepwise linear regression and logistic regression analysis method. By introducing the measured value of feature indicator into the excess probability formula, the rate of excess-standard of heavy metals leaching can be preliminarily determined. Based on the above ideas, a rapid detection and evaluation system could be developed according to the local leaching standards and the components of fly ash selected locally.

Rain, throughfall, soil waters from surface peaty O horizon and deeper mineral B horizon, and stream water, were collected every four weeks for one year in a moorland catchment, and in four forested catchments. The four forested catchments represented an age sequence of first rotation Sitka spruce plantations, aged 14, 28, 37 and 53 years. All water samples were analysed for all major solutes, including dissolved organic nitrogen (DON-N); stream water and B horizon soil waters were also subjected to aluminium speciation. In each catchment, soil samples were collected on one occasion and pH was measured. Concentrations of most solutes were substantially higher in the 37 year old forest stand than in the moorland catchment, with intermediate concentrations in the two younger stands and 53 year old stand. In particular, higher nitrate-N concentrations were found in the soils and streams of the older forests, although these concentrations tended to be highest in the 37 year old stand. Acid neutralizing capacity (ANC) of soil waters was lower in the B horizon of the forest stands than in the moorland, and tended to decline with increasing forest age. Soil water from both O and B horizons was most acid in the 37 year old stand, and the water from the soil O horizon in all four forest stands was more acid than that in moorland sites. The pH of the soil itself (as measured in a deionised water slurry) was lower in the forest stands than in moorland, although trends with forest age were complex.

The contribution of forest harvesting to base cation losses and soil acidification has increased in recent years in Sweden, as the demand for bioenergy has increased and the sulphur deposition has decreased. Thus, new policy tools are required to evaluate the progress of the recovery from acidification, and as a basis for forest management recommendations. In this study we introduce and test a concept, “Critical biomass harvesting”. The concept builds on the concept “Critical loads”, which has been used world-wide for several decades as a bridge between science and policies related to transboundary air pollution and acidification. The basis for the concept is an acidity mass balance, with sources and sinks of acidity. A critical limit defines the highest acceptable acidification status of the water leaving the root zone. Based on the critical limit, the highest allowed biomass harvesting can be calculated, keeping the other parameters constant. In this study the critical limit was set to ANC (Acid Neutralizing Capacity) = 0. Nitrogen was assumed to be affecting acidity only if it leaches from the root zone. The critical biomass harvesting was calculated for almost 12 000 National Forest Inventory sites with spruce and pine forest, using the best available data on deposition, weathering and nitrogen leaching. The exceedance of critical biomass harvesting was calculated as the difference between the estimated harvest losses and the critical biomass harvesting. The results were presented as median values in merged catchments in a catchment database, with totally 2079 merged catchments in Sweden. According to the calculations, critical biomass harvesting was exceeded in the southern half of Sweden already at stem harvesting in spruce forests. Whole-tree harvesting expanded the exceedance area, and increased the exceedance levels in southern Sweden. The exceedance in pine forest was lower and affected smaller areas. It was concluded that the concept of critical biomass harvesting can be successfully applied on the same database that has been used for critical load calculations in Sweden, using basically the same approach as has been extensively applied, evaluated and discussed in a critical load context. The results from the calculations in Sweden indicate that whole-tree harvesting, without wood ash recycling, can be expected to further slow down recovery, especially in the most acidified parts of the country, in the southwest.

Significance Salinization and alkalinization impact water quality, but these processes have been studied separately, except in arid regions. Globally, salinization has been largely attributed to agriculture, resource extraction, and land clearing. Alkalinization has been attributed to recovery from acidification, with less recognition as an environmental issue. We show that salinization and alkalinization are linked, and trends in these processes impact most of the drainage area of the United States. Increases in salinity and alkalinity are caused by inputs of salts containing strong bases and carbonates that originate from anthropogenic sources and accelerated weathering. We develop a conceptual model unifying our understanding of salinization and alkalinization and its drivers and impacts on fresh water in North America over the past century., Salt pollution and human-accelerated weathering are shifting the chemical composition of major ions in fresh water and increasing salinization and alkalinization across North America. We propose a concept, the freshwater salinization syndrome, which links salinization and alkalinization processes. This syndrome manifests as concurrent trends in specific conductance, pH, alkalinity, and base cations. Although individual trends can vary in strength, changes in salinization and alkalinization have affected 37% and 90%, respectively, of the drainage area of the contiguous United States over the past century. Across 232 United States Geological Survey (USGS) monitoring sites, 66% of stream and river sites showed a statistical increase in pH, which often began decades before acid rain regulations. The syndrome is most prominent in the densely populated eastern and midwestern United States, where salinity and alkalinity have increased most rapidly. The syndrome is caused by salt pollution (e.g., road deicers, irrigation runoff, sewage, potash), accelerated weathering and soil cation exchange, mining and resource extraction, and the presence of easily weathered minerals used in agriculture (lime) and urbanization (concrete). Increasing salts with strong bases and carbonates elevate acid neutralizing capacity and pH, and increasing sodium from salt pollution eventually displaces base cations on soil exchange sites, which further increases pH and alkalinization. Symptoms of the syndrome can include: infrastructure corrosion, contaminant mobilization, and variations in coastal ocean acidification caused by increasingly alkaline river inputs. Unless regulated and managed, the freshwater salinization syndrome can have significant impacts on ecosystem services such as safe drinking water, contaminant retention, and biodiversity.

Acid rain, or acid deposition, was determined to be a widespread environmental problem in the late 1960s and early 1970s in eastern North America and northwestern Europe. Acid deposition is largely attributed to the burning of fossil fuels, which in turn releases the acid deposition precursors, sulfur dioxide (SO 2 ), mainly from power plants, and nitrogen oxides (NO x ), mainly from vehicles. Early signs of environmental damage from acid deposition include the loss of fish populations in remote lakes and streams, and the die back of forests in Europe and eastern North America. Scientific evidence and public outcry in these regions led to legislation to reduce emissions of SO 2 , and then NO x , which resulted in dramatic declines in acid deposition and other related pollutants (e.g., particulates), and in many areas an improvement in ecosystem and human health. Some areas have only seen minor improvements due to long-term loss of acid neutralizing capacity in soils of acid sensitive landscapes, brought about by decades of acid deposition. SO 2 and NO x emissions are increasing in Asia, where the high potential for future problems related to acid deposition still exists.

Great Smoky Mountains National Park (GSMNP) is subject to high levels of sulfur (S) and nitrogen (N) deposition, which can adversely affect forest vegetation and aquatic biota. We used multiple chemical criteria to calculate critical loads for S and N deposition (CL (S+N)) and nutrient N (CLnutN) and used the Very Simple Dynamic (VSD) model to predict the effects of deposition reduction scenarios on critical thresholds for four forested sites in GSMNP. Critical loads were exceeded for current deposition at three of four sites using critical thresholds of aluminum to base cations (Al:Bc) = 0.1 or no decrease in base saturation but were not exceeded using the chemical criteria of Al = 0.2 meq L-1, Al:Bc = 1.0, and pH = 4.2. With deposition reductions of 48 percent S and 56 percent nitrate (NO3‾), neither the critical thresholds of acid neutralizing capacity (ANC) = 20 μeq L-1 nor a decrease in base saturation was achieved. With deposition reductions of 90 percent S and 90 percent NO3‾, ANC = 100 μeq L-1 was achieved at a single site. Historical ANC values affected a site's ability to achieve ANC critical thresholds. The critical threshold for soil solution NO3‾ was exceeded for all but the most stringent deposition scenarios (–90 percent S and –90 percent NO3¯). Deposition reductions of 90 percent for NO3‾ and 80 percent for ammonium (NH4+) were not sufficient to lower deposition below the CLnutN at all sites. Data indicate that upper sites at GSMNP are N saturated; to protect these sites from acidification, the more protective chemical criteria of no decrease in base saturation and Al:Bc = 0.1 should be used when determining critical loads. When choosing chemical criteria in deposition reduction modeling, care should be taken to ensure that the criteria chosen will protect sensitive ecosystem elements.

Soil acidification is defined as the process in which exchangeable cations are leaching and soil H+ concentration is raising thereby increases soil acidity. Changes in soil pH value and acid neutralizing capacity are mainly indicators of soil acidification. Soil acidification is considered to be a serious ecological and environmental issue, which not only reduces soil quality, but also decreases biodiversity of forest ecosystem and induces forest decline. With nitrogen (N) deposition rapidly increasing, its contribution to soil acidification becomes a major concern in the world. However, the impact of increased N deposition on soil acidification is not well addressed highlighting the need for further attention to the issue. In this paper, the studies on forest soil acidification induced by N deposition were reviewed. The factors related to soil acidification driven by N deposition were classified and discussed, which included soil acidic buffering capacity, N components in atmospheric N deposition, climate, plant species in forests, and N status in ecosystem. Iron (Fe) buffering phase and the consequent Fe toxicity occurring to the acidified soil caused by high N deposition were concerned. The scarcity of phosphorus (P) element induced by soil acidification was particularly emphasized. The research methods used to study soil acidification driven by N deposition were also evaluated. In the end we stressed the importance of the study on soil acidification especially in tropical and subtropical regions driven by N deposition and its mechanisms. This paper can serve for maintaining sustainable forest and agricultural ecosystems.

At the Kidston gold mine, Australia, the direct establishment of vegetation on tailings was considered as an alternative to the use of a waste rock cover. The tailings acid/base account was used to predict plant growth limitation by acidity, and thus methods capable of identifying tailings that would acidify to pH 4.5 or lower were sought. Total S was found to be poorly correlated with acid-generating sulfide, and total C was poorly correlated with acid-neutralizing carbonate, precluding the use of readily determined total S and C as predictors of net acid generation. Therefore, the selected approach used assessment of sulfide content as a predictor of acid generation, and carbonate content as a measure of the acid-neutralizing capacity available at pH 5 and above. Using this approach, the majority of tailings (67%) were found to be non-acid generating. However, areas of potentially acid-generating tailings were randomly distributed across the dam, and could only be located by intensive sampling. The limitations imposed by the large sample numbers, and costly analysis of sulfide and carbonate, make it impractical to identify and ameliorate acid-generating areas prior to vegetation establishment. However, as only a small proportion of the tailings will acidify, a strategy of re-treating acid areas following oxidation is suggested. The findings of the present study will assist in the selection of appropriate methods for the prediction of net acid generation, particularly where more conservative measurements are required to allow vegetation to be established directly in tailings.

Tropical forests are characterized by highly weathered and acidified soils, whilst patterns and processes of soil acidification are diverse under different geological and climatic conditions. To identify the dominant processes of soil acidification in Southeast Asia, proton budgets were quantified for plant-soil systems in Indonesia and Thailand. The net proton generation by plant uptake was consistently high in the tropical forests. Acidification of soils can function as nutrient acquisition strategies of plants that promote cation mobilization through mineral weathering and cation exchange reaction. Soil solution composition indicated that organic acids are dominant anions that drive acidification in the highly acidic soils from sandy sedimentary rocks. Production of organic acids in the O horizons can be enhanced by the high activities of fungal enzymes (peroxidases) especially in the lignin-rich and P-poor litters on the highly acidic soils. On the other hand, bicarbonate also contributed to cation mobilization in the moderately acidic soils from clayey sedimentary rocks and ultramafic rocks (Indonesia) and under monsoon climate with distinct dry season (Thailand). The spatiotemporal variation in fine roots (plant uptake) and organic and carbonic acids can lead to different pathways of pedogenesis, i.e., incipient podzolization (Al eluviation/illuviation) and ferralitization (in situ weathering). The differences in acid-neutralizing capacities of parent materials and climatic patterns can generate the variability in soil acidity, and plant and microbial feedbacks can further reinforce the patterns of soil acidification.

Liming of acidic soils increases crop yield and farming profitability. The effectiveness of a liming material for neutralizing soil acidity depends mainly on its calcium carbonate (CaCO3) equivalent (CCE) and its fineness. The Iowa Department of Agriculture and Land Stewardship (IDALS) rules for agricultural lime (aglime) sales requires measuring Effective CCE (ECCE), which combines CCE and fineness efficiency estimates. Use of pelleted finely ground limestone has increased in recent years, but scarce field research has evaluated how ECCE evaluates the granulation effect on its acid neutralizing capacity compared with aglime. Therefore, a study was conducted at two Iowa State University (ISU) central Iowa farms to compare the effectiveness of calcium carbonate, calcitic aglime, and pelleted calcitic aglime at increasing soil pH and crop yield.

Acidic deposition has impaired acid-sensitive surface waters in the Adirondack region of New York by decreasing pH and acid neutralizing capacity (ANC). In spite of air quality programs over past decades, 128 lakes in the Adirondacks were classified as “impaired” under Section 303(d) of the Clean Water Act in 2010 due to elevated acidity. The biogeochemical model, PnET-BGC, was used to relate decreases in atmospheric sulfur (S) and nitrogen (N) deposition to changes in lake water chemistry. The model was calibrated and confirmed using observed soil and lake water chemistry data and then was applied to calculate the maximum atmospheric deposition that the impaired lakes can receive while still achieving ANC targets. Two targets of ANC were used to characterize the recovery of acid-impaired lakes: 11 and 20 meq L � 1 . Of the 128 acid-impaired lakes, 97 currently have ANC values below the target value of 20 meq L � 1 and 83 are below 11 meq L � 1 . This study indicates that a moderate control scenario (i.e., 60% decrease from the current atmospheric S load) is projected to recover the ANC of lakes at a mean rate of 0.18 and 0.05 meq L � 1 yr � 1 during the periods 2022e2050 and 2050e2200, respectively. The total maximum daily load (TMDL) of acidity corresponding to this moderate control scenario was estimated to be 7.9 meq S m � 2 yr � 1 which includes a 10% margin of safety.

Forest biofuel is a main provider of energy in Sweden and the market is expected to grow even further in the future. Removal of logging residues via harvest can lead to short-term acidification but the long-term effects are largely unknown. The objectives of this study were to 1) model the long-term effect of whole-tree harvest (WTH) on soil and stream water acidity and 2) perform sensitivity analyses by varying the amounts of logging residues, calcium (Ca 2 + ) concentrations in tree biomass and site productivity in nine alternate scenarios. Data from three Swedish forested catchments and the Model of Acidification of Groundwater in Catchments (MAGIC) were used to simulate changes in forest soil exchangeable Ca 2 + pools and stream water acid neutralizing capacity (ANC) at Gammtratten, Kindla and Aneboda. Large depletions in soil Ca 2 + supply and a reversal of the positive trend in stream ANC were predicted for all three sites after WTH. However, the magnitude of impact on stream ANC varied depending on site and the concentration of mobile strong acid anions. Contrary to common beliefs, the largest decrease in modelled ANC was observed at the well-buffered site Gammtratten. The effects at Kindla and Aneboda were much more limited and not large enough to offset the general recovery from acidification. Varying the tree biomass Ca 2 + concentrations exerted the largest impact on modelled outcome. Site productivity was the second most important variable whereas changing biomass amounts left on site only marginally affected the results. The outcome from the sensitivity analyses pointed in the same direction of change as in the base scenario, except for Kindla where soil Ca 2 + pools were predicted to be replenished under a given set of input data. The reliability of modelled outcome would increase by using site-specific Ca 2 + concentrations in tree biomass and field determined identification of site productivity.

Elevated anthropogenic nitrogen (N) deposition has greatly altered terrestrial ecosystem functioning, threatening ecosystem health via acidification and eutrophication in temperate and boreal forests across the northern hemisphere. However, response of forest soil acidification to N deposition has been less studied in humid tropics compared to other forest types. This study was designed to explore impacts of long-term N deposition on soil acidification processes in tropical forests. We have established a long-term N-deposition experiment in an N-rich lowland tropical forest of Southern China since 2002 with N addition as NH4 NO3 of 0, 50, 100 and 150 kg N ha(-1) yr(-1) . We measured soil acidification status and element leaching in soil drainage solution after 6-year N addition. Results showed that our study site has been experiencing serious soil acidification and was quite acid-sensitive showing high acidification (pH(H2O)

Forest management planning is increasingly focused at the landscape scale. The resulting increase in planning unit size has fueled debate about forest sustainability, particularly at local scales. In boreal and temperate regions, Ca depletion in forest and aquatic ecosystems is a recently debated issue. Planning decisions that sustain forest soil and surface water Ca require identification of sites sensitive to Ca loss and application of silvicultural prescriptions that maintain background Ca pools and fluxes. Therefore, I synthesized data on forest Ca cycling and export and long-term (>10 yr) soil exchangeable Ca pools and changes in surface water quality. Findings indicated that hardwood forest soils contained over three-times more (P < 0.05), their catchments exported three-times more (P < 0.05), and through leaf-litter fall they recycled twice (p < 0.01) as much Ca as conifer–mixedwood forests. Nonetheless, over similar timeframes, forest floor in mature hardwood stands lost more (P < 0.05) Ca than did conifer–mixedwood soils, which was consistent with net stream and lake Ca losses (P < 0.01). However, surface water acid neutralizing capacity increased (P < 0.01), possibly due to greater sulfate declines relative to Ca. On average, based on soil concentrations and contents, forestry practices did not significantly deplete Ca in either cover type. Study results indicate that stand- and catchment-scale forest Ca pools and fluxes can be used to identify areas potentially sensitive to Ca depletion and water quality degradation. However, considerable variation exists in Ca and acidification responses to external stressors, limiting spatial and temporal projections.

While North America and Europe have been recovering from acidification, China is experiencing impacts of acid deposition. The Taihu region is a seriously impacted area by acid rain in China, with the average rainfall pH < 5. However, the acid neutralizing capacity (ANC) and pH of Taihu Lake have significantly increased over the past 60 years (p < 0.05). Analyses showed that watershed neutralization by carbonates and in-lake alkalinization by algae activities were the two major reactions responsible for the increase. In the Taihu basin, the dominant carbonate bedrocks are the major source of base cations (particularly Ca2+ and Mg2+) and act as the acidification buffer. In addition, our field measurements across the lake showed that the pH values were significantly higher in algal bloom waters than in areas without blooms. This observation was further supported by our statistical analysis showing that the Taihu ANC and pH were significantly correlated with the chlorophyll increase (p < 0.05; 1985–2015). How...

[1] In many industrialized regions of the world, atmospherically deposited sulfur derived from industrial, nonpoint air pollution sources reduces stream water quality and results in acidic conditions that threaten aquatic resources. Accurate maps of predicted stream water acidity are an essential aid to managers who must identify acid-sensitive streams, potentially affected biota, and create resource protection strategies. In this study, we developed correlative models to predict the acid neutralizing capacity (ANC) of streams across the southern Appalachian Mountain region, USA. Models were developed using stream water chemistry data from 933 sampled locations and continuous maps of pertinent environmental and climatic predictors. Environmental predictors were averaged across the upslope contributing area for each sampled stream location and submitted to both statistical and machine-learning regression models. Predictor variables represented key aspects of the contributing geology, soils, climate, topography, and acidic deposition. To reduce model error rates, we employed hurdle modeling to screen out well-buffered sites and predict continuous ANC for the remainder of the stream network. Models predicted acid-sensitive streams in forested watersheds with small contributing areas, siliceous lithologies, cool and moist environments, low clay content soils, and moderate or higher dry sulfur deposition. Our results confirmed findings from other studies and further identified several influential climatic variables and variable interactions. Model predictions indicated that one quarter of the total stream network was sensitive to additional sulfur inputs (i.e., ANC

Describing the distribution of aquatic habitats and the health of biological communities can be costly and time-consuming; therefore, simple, inexpensive methods to scale observations of aquatic biota to watersheds that lack data would be useful. In this study, we explored the potential of a simple "hydrogeomorphic" model to predict the effects of acid deposition on macroinvertebrate, fish, and diatom communities in 28 sub-watersheds of the 176-km2 Neversink River basin in the Catskill Mountains of New York State. The empirical model was originally developed to predict stream-water acid neutralizing capacity (ANC) using the watershed slope and drainage density. Because ANC is known to be strongly related to aquatic biological communities in the Neversink, we speculated that the model might correlate well with biotic indicators of ANC response. The hydrogeomorphic model was strongly correlated to several measures of macroinvertebrate and fish community richness and density, but less strongly correlated to diatom acid tolerance. The model was also strongly correlated to biological communities in 18 sub-watersheds independent of the model development, with the linear correlation capturing the strongly acidic nature of small upland watersheds (1 km2). Overall, we demonstrated the applicability of geospatial data sets and a simple hydrogeomorphic model for estimating aquatic biological communities in areas with stream-water acidification, allowing estimates where no direct field observations are available. Similar modeling approaches have the potential to complement or refine expensive and time-consuming measurements of aquatic biota populations and to aid in regional assessments of aquatic health.

Acid deposition has impacted sensitive streams, reducing the amount of habitat available for fish survival in the Great Smoky Mountains National Park (GRSM) and portions of the surrounding Southern Appalachian Mountains by decreasing pH and acid neutralizing capacity (ANC) and mobilizing aluminum dissolved from soil. Land managers need to understand whether streams can recover from the elevated acid deposition and sustain the healthy aquatic biota, and if so, how long it would take to achieve this condition. We used a dynamic biogeochemical model, PnET-BGC, to evaluate past, current, and potential future changes in soil and water chemistry of watersheds of the GRSM in response to the projected changes in acid deposition. The model was parameterized with soil, vegetation, and stream observations for 30 stream watersheds in the GRSM. Using model results, the level of atmospheric deposition (known as a “critical load”) above which harmful ecosystem effects (defined here as modeled stream ANC below a defined target) occur was determined for the 30 study watersheds. In spite of the recent marked decreases in atmospheric sulfur and nitrate deposition, our results suggest that stream recovery has been limited and delayed due to the high sulfate adsorption capacity of soils in the park resulting in a long lag time for recovery of soil chemistry to occur. Model simulations suggest that over the long term, increases in modeled stream ANC per unit decrease in NH4+ deposition are greater than unit decreases in SO42− or NO3− deposition, due to high SO42− adsorption capacity and the limited N retention of the watersheds. Watershed simulations were used to extrapolate the critical load results to 387 monitored stream sites throughout the park and depict the spatial pattern of atmospheric deposition exceedances. These types of model simulations inform park managers on the amount of air quality improvement needed to meet the stream restoration goals.

Elevated anthropogenic acid deposition can significantly affect forest ecosystem functioning by changing soil pH, nutrient balance, and chemical leaching and so on. These effects generally differ among different forests, and the dominant mechanisms for those observed responses often vary, depending on climate, soil conditions and vegetation types. Using soil monoliths (0–40 cm) from pine forest (pioneer), coniferous and broadleaved mixed forest (transitional) and broadleaved forest (mature) in southern China, we conducted a leaching experiment with acid treatments at different pH levels (control: pH ≈ 4.5; pH = 3.5; pH = 2.5). We found that pH 3.5 treatment significantly reduced dissolved organic carbon (DOC) concentrations in leachate from the pioneer forest soil. pH 2.5 treatment significantly increased concentrations of NO3−, SO42 −, Ca2 +, Mg2 +, Al3 +, Fe3 + and DOC in leachate from the pioneer forest soil, and also concentrations of NO3−, SO42 −, Mg2 +, Al3 +, Fe3 + and DOC in leachate from the transitional forest soil. All acid treatments had no significant effects on concentrations of these chemicals in leachate from the mature forest soil. The responses can be explained by the changes in soil pH, acid neutralizing capacity (ANC) and concentrations of Al and Fe. Our results showed that acid buffering capacity of the pioneer or transitional forest soil was lower than that of the mature forest soil. Therefore preserving mature forests in southern China is important for reducing the adverse impacts of high acid deposition on stream water quality at present and into the future.

A regional survey of surface water acidification in Sichuan Basin was carried out during 2009–2011. Analysis of more than 90 samples revealed high pH and acid neutralizing capacity (ANC) in most surface waters, indicating that surface water acidification might not be a serious environmental issue in Sichuan Basin. However, some acidified surface water systems were present. Comparison of the results with a survey conducted 20 years ago revealed a significant decrease in ANC and increasing sulfate (SO42 ) and nitrate (NO3) concentrations. Rapid increases in sulfur dioxide (SO2 ) and nitrogen oxides (NOx ) emissions were likely the primary cause of surface water acidification, while high weathering of the purple soil in Sichuan Basin likely enabled strong buffering against acidification of surface water. However, low weathering occurred in areas of yellow earth and yellow-brown earth in the surrounding mountains, indicating that serious acid deposition could lead to acidification of surface water in these areas.

The ratio of the spatial and temporal distribution of dissolved organic carbon to acid neutralizing capacity in the surface waters of the Lake Baikal Basin was studied. This ratio reflects the geological and geographical conditions of the watershed. In the warm season, the ratio depends on the watershed's size and relief; in the cold season, it depends on the watershed's chemistry. The ratio was used to estimate the contributions of dissolved matter sources, such as subsoil, topsoil, and the atmosphere, to the surface water. A correlation analysis was performed to establish relationships between the sources and solutes. The processes with the greatest effect on water chemistry were determined by analyzing these relationships.

A sudden geometric increase in population of Akoko North West Local Government Area of Ondo State has led to an increase in demand for water and harnessing of subsurface water reserve. A total of twenty six water samples obtained from both boreholes and hand-dug wells were analyzed for their physico-chemical characteristics with the aim of assessing their quality, usability and also to determine the level of their contamination in the local government which is dominated by granite gneisses, charnockites, and augen gneisses as the main rock types. The following physico-chemical properties were analyzed for in the samples collected: electrical conductivity (EC), pH, total alkalinity (TA), total dissolved solids (TDS), total suspended solids (TSS), acid neutralizing capacity (ANC) with major cations (Na + , Mg 2+ , Ca 2+ ), anions (PO4 3- , HCO3 - , SO4 3- ) and several heavy metals (Zn 2+ , Fe 2+ , As + , Ni + , Pb 2+ , Cd + , Cu 2+ ). The following results were obtained from the analysis: Zn 2+ (0.109 – 0.437 ppm), Fe 2+ (0.216 – 0.726 ppm), As + (0.01 – 0.03 ppm), Ni + (0.036 – 0.074), Pb 2+ (0.003 – 0.010), Cd + (0.002 – 0.007), Cu 2+ (0.086 – 0.241) with appreciable abundances of PO4 3- , Cd + , Fe 2+ and Ni + some exceeding while some others are below the WHO acceptable level for drinking water, thereby making it a serious source of concern as it indicates varying levels of faecal contamination (from leaky septic tanks, interception with pit latrines) and heavy metal liberation into the water consumed by the residents. It was also noticed that the water was fresh based on the analysis of the Total Dissolved Solids and the Pb 2+ concentrations almost exceeded the standard permissible limit. Generally, it was concluded that the overall quality of the ground water is averagely good physico-chemically.

After years of adverse impacts to the acid-sensitive ecosystems of the eastern United States, the Acid Rain Program and Nitrogen Budget Program were developed to control sulfur dioxide (SO2) and nitrogen oxide (NOx) emissions through market-based cap and trade systems. We used data from the National Atmospheric Deposition Program’s National Trends Network (NTN) and the U.S. EPA Temporally Integrated Monitoring of Ecosystems (TIME) program to evaluate the response of lake-watersheds in the Adirondack region of New York to changes in emissions of sulfur dioxide and nitrogen oxides resulting from the Acid Rain Program and the Nitrogen Budget Program. TIME is a long-term monitoring program designed to sample statistically selected subpopulations of lakes and streams across the eastern U.S. to quantify regional trends in surface water chemistry due to changes in atmospheric deposition. Decreases in wet sulfate deposition for the TIME lake-watersheds from 1991 to 2007 (−1.04 meq m−2-yr) generally corresponded with decreases in estimated lake sulfate flux (−1.46 ± 0.72 meq m−2-yr), suggesting declines in lake sulfate were largely driven by decreases in atmospheric deposition. Decreases in lake sulfate and to a lesser extent nitrate have generally coincided with increases in acid neutralizing capacity (ANC) resulting in shifts in lakes among ANC sensitivity classes. The percentage of acidic Adirondack lakes (ANC

Acid atmospheric emissions within Europe and North America have decreased strongly since 1985 and most recent acidification studies have focused on the changes occurring within ecosystems as a result of this decreased deposition. This current study documents a soil acidification trend under ambient N deposition conditions over a 13 year period, suggesting that acidification continues to be a process of concern at this Calluna vulgaris dominated heathland with an acidic sandy soil. The annual manipulation of climatic conditions on this heathland simulated the predicted summer rainfall reduction (drought) and resulted in a long term retardation of the soil acidification trend. The pH of the soil solution significantly decreased over the course of the trial for both treatments, however, in the final two years the decline continued only in the Control treatment. This retardation is primarily associated with the reduction in rainfall leading to lower drainage rates, reduced loss of cations and therefore reduced lowering of the soil acid neutralizing capacity (ANC). However, a change in the underlying mechanisms also indicated that N transformations became less important in the Drought treatment. This change corresponded to an increase in groundcover of an air-pollution tolerant moss species and it is hypothesized that this increasing moss cover filtered an increasing quantity of deposited N, thus reducing the N available for transformation. A soil acidification lag time is expected to increase between the two treatments due to the cumulative disparity in cation retention and rates of proton formation. To the authors knowledge, this is the first study in which such acidification trends have been demonstrated in a field-scale climate manipulation experiment.

We used data collected from 1989 to 2009 from 151 shallow (mean depth

The model of acidification of groundwater in catchments (MAGIC) was used to simulate a matrix of target load (TL) values for use in protection and restoration of forest resources in the Adirondack Mountains of New York against soil acidification by acidic deposition. Modeling results were extrapolated to the population of 1,320 watersheds in the Adirondack Ecoregion that contain lakes expected to be >1 ha and >1 m deep and that have acid neutralizing capacity

Recovery from anthropogenic acidification in streams and lakes is well documented across the northern hemisphere. In this study, we use 1996–2009 data from the four Swedish Integrated Monitoring catchments to evaluate how the declining sulfur deposition has affected sulfate, pH, acid neutralizing capacity, ionic strength, aluminum, and dissolved organic carbon in soil water, groundwater and runoff. Differences in recovery rates between catchments, between recharge and discharge areas and between soil water and groundwater are assessed. At the IM sites, atmospheric deposition is the main human impact. The chemical trends were weakly correlated to the sulfur deposition decline. Other factors, such as marine influence and catchment features, seem to be as important. Except for pH and DOC, soil water and groundwater showed similar trends. Discharge areas acted as buffers, dampening the trends in streamwater. Further monitoring and modeling of these hydraulically active sites should be encouraged.

The ecological effects of elevated atmospheric nitrogen (N) deposition on high-elevation lakes of the western and northeastern United States include nutrient enrichment and acidification. The nutrient enrichment critical load for western lakes ranged from 1.0 to 3.0 kilograms (kg) of N per hectare (ha) per year, reflecting the nearly nonexistent watershed vegetation in complex, snowmelt-dominated terrain. The nutrient enrichment critical load for northeastern lakes ranged from 3.5 to 6.0 kg N per ha per year. The N acidification critical loads associated with episodic N pulses in waters with low values of acid neutralizing capacity were 4.0 kg N per ha per year (western) and 8.0 kg N per ha per year (northeastern). The empirical critical loads for N-caused acidification were difficult to determine because of a lack of observations in the West, and high sulfur deposition in the East. For both nutrient enrichment and acidification, the N critical load was a function of how atmospheric N deposition was deter...

Despite decades of research about episodic acidification in many regions of the world, the understanding of what controls the transient changes in stream water chemistry occurring during rain and snow melt events is still limited. Here, we use 20 years of hydrological and stream chemical data from the paired watershed study at Bear Brook Watershed in Maine (BBWM), USA to improve the understanding of the effects of acid deposition on the causes, drivers, and evolution of episodic acidification. The long-term experimental study at BBWM includes 18 years of chemical treatment of the West Bear Brook (WB) watershed with (NH4)2SO4. East Bear Brook (EB) serves as reference. The treatment started in 1989 following a 2-year pretreatment period. We analyzed 212 hydrological episodes using an episode model that can separate and quantify individual drivers of the transient change in acid-neutralizing capacity (ANC) during hydrological events. The results suggest that 18 years of N and S addition have not affected the natural drivers of episodic acidification of base-cation dilution, marine sea salt episodes, or organic acidity during rain and snow melt events. The contribution of SO\(_{4}^{2-}\) to the ANC decline in WB has been increasing linearly since the beginning of watershed treatment, while the role of NO\(_{3}^{-}\) has remained relatively constant after an initial increase. This is contradictory to many previous shorter-term studies and illustrates the need for a more mechanistic understanding of the causes and drivers of episodic acidification during rain- and snow melt-driven hydrological events.

Macrocomponent chemical composition data for the waters and the volume of streamflow were used to quantify the contributions from alkaline and alkaline-earth metal cation sources in surface waters (atmospheric depositions, and mineral and organic matter of soils). It is shown that the proportion of matter of organogenic origin in surface waters is decreasing from spring to autumn, as opposed to the increase in the contribution from weathering. The largest values of removal of cations of both mineral and organic origin are observed in mid-summer.

Studies on the chemical composition of wet precipitation were carried out from September 2005 to September 2007 at three Chinese regional background stations. All samples were analyzed for pH and major ions (F − , Cl − , NO − 3 , SO 4 2− , K + , Na + , Ca 2+ , Mg 2+ and NH 4 + ). Of the three stations, the lowest pH value was observed at Lin'an. The highest ion concentrations (SO 4 2− , NO 3 − and NH 4 + ) occurred at Shangdianzi. By referring to former studies and observations of reactive gases at the three stations, pH and chemical composition trends from 1985 to 2007 were analyzed. Compared to values from 1985 to 1997, the pH values in the precipitation of all three stations were significantly lower and [NO 3 − ] was higher. [SO 4 2− ] in the precipitation also increased at Shangdianzi and Longfengshan. Due to the neutralization of alkaline aerosols in northern China, precipitation at Shangdianzi and Longfengshan was not as severely acidified as at Lin'an. However, the neutralizing effects of the aerosols have decreased in recent years. Significant correlations between ions were found at each of the three stations. Principal component analysis was also performed to find possible sources of the major ionic species. Acid rain research in China has traditionally focused on urban sites, however the present study of background stations revealed significant effects of long-range transported air pollutants on rural areas in China.