Low Acid Neutralizing Capacity Research Articles

Assessing impacts of sulfur deposition on aquatic ecosystems: A decision support system for the Southern Appalachians

AbstractWith climate change and ongoing impacts from human development and resource extraction, US federal land management agencies are acutely concerned with managing for healthy aquatic ecosystems in the Southern Appalachian Mountain (SAM) Region. Here, we describe development of a spatial decision support application to assess the biological and ecological impacts of atmospheric S and N deposition on aquatic ecosystems of the region. We first summarize foundational published work to predict continuous maps of surface water acid neutralizing capacity (ANC) and soil base cation weathering (BCw). We use the predicted ANC and BCw maps to estimate steady‐state critical loads (CLs) of atmospheric S and N deposition. We included estimated CLs of atmospheric N to get a complete picture of CLs and potential exceedances. We then present a logic‐based decision support model for assessing effects of S and N deposition based on statistically modeled stream ANC and CL exceedance. The model is easily modified for continuous monitoring of CL exceedance patterns as new S and N deposition and ANC data become available. We present mapped model results for the SAM study area and an important subset of the region, the Great Smoky Mountains National Park. ANC modeling results revealed that predicted acid sensitivity was spatially variable, with areas of relatively low stream ANC (<50 μeq · L−1) and soil BCw (<50 meq · m−2 · year−1) predominantly found in certain critical areas. Within the Great Smoky Mountains National Park, evidence for S CL exceedance based on an ANC criterion of 50 μeq · L−1 was strong at locations where ambient S deposition was at least two times the CL. We also predicted likely impacts of CL exceedances on aquatic insect species richness and native fish abundance. Responses for insect species richness and fish impact showed variability similar to CL exceedance, with increasing impact positively correlated with elevation. Finally, we discuss ways that the decision support system can be used to prioritize management across the region.

Factors Influencing the Distribution of Freshwater Mollusks in the Lakes of the Pyrenees: Implications in a Shifting Climate Scenario

Climate warming is expected to drive an upward altitudinal shift of species distributions in mountain areas. In this study, we consider how environmental variables constrain the distribution of freshwater mollusks across elevations based on an extensive survey of the entire Pyrenean range. Results show that several altitude-related variables are significantly relevant for the distribution of all mollusks (i.e., temperature, sediment organic content). Others respond more precisely to some variables: fine substrate proportion increases the probability of finding Pisidium sensu lato (mostly Euglesa species), and the latter, the macrophyte presence, and Ampullaceana balthica. Despite the low acid-neutralizing capacity in many of the lakes, only the distribution of A. balthica was significantly constrained by this factor, independent from elevation. The results confirm a likely altitudinal expansion of the distributions of all species, particularly toward lakes with a summer surface temperature increasing above 12 °C. The pace of change is expected to differ among species according to different nonlinear thresholds in thermal response, which temperature value increases from Pisidium s.l. to Ampullaceana to Ancylus, and the taxon-specific sensitivity to substrates and chemical conditions.

Accelerated carbonation of ball-milling modified MSWI fly ash: Migration and stabilization of heavy metals

Mechanical ball-milling is an effective technique to reduce particle size, increase lattice defects, and enhance the activity of materials. After mechanical ball-milling modification, an accelerated carbonation technology of municipal solid waste incineration fly ash (FA) was proposed. The effects of ball-milling on carbonation efficiency, heavy metals stabilization, and heavy metals leaching characteristics were investigated. The results showed that the initial carbonation efficiency of ball-milled FA (MFA) was higher than that of the original FA (OFA) because of the in-situ carbonation reaction and the stability of Pb, Cu, and Cd in MFA was improved. The carbonation reaction of MFA was conducted thoroughly by the elevated ionic strength and mass transfer efficiency. The surface of carbonated OFA (COFA) and carbonated MFA (CMFA) stacked calcium carbonation in loose strips and compact spherical respectively, relating to the initial morphology. The dechlorination of CMFA was superior to COFA because the more in-depth carbonation eluted the chlorine from Friedel’s salt. The leaching concentrations of heavy metals in CMFA were lower than those in COFA, especially the immobilization efficiency of Pb and Zn reached 99.8 % and 98.5 %, respectively, contributed by the conversion of the Pb and Zn from ionic hydroxides to stable carbonates. Due to the low acid neutralization capacity of CMFA, when the pH dropped from 7 to 5, the heavy metals carbonate chemical precipitation dissolved, and the effect of calcium carbonation on heavy metals wrapping and adsorption disappeared, therefore the subsequent disposal of CMFA should avoid an acidic environment.

Comparison of Acid-neutralizing capacity of antacids in Erbil City

Background and objective: Antacids are basic substances that can neutralize hydrochloric acid and reduce gastric acidity. They are over the counter drugs used to treat dyspepsia. The most commonly used antacids are sodium bicarbonate, magnesium hydroxide, aluminum hydroxide, and calcium carbonate. This study aimed to evaluate the effectiveness of antacids that are commonly used in Erbil city by finding their acid-neutralizing capacity. Methods: The method for acid-neutralizing capacity was adapted from pharmacopeia. The samples were prepared by dissolving the antacid in an excess amount of hydrochloric acid, then neutralizing the excess acid with sodium hydroxide solution by doing back titration. The number of milliequivalents that are neutralized by the antacid is the acid-neutralizing capacity of the antacid. Results: Rennie® chewable tablet showed the highest acid-neutralizing capacity, followed by AntacidAwa and Maalux® plus. The lowest acid-neutralizing capacity was for the suspensions Gaviscon® and Enoxon®. Conclusion: Acid-neutralizing capacity is an easy and quick method to evaluate the efficacy of antacids. Different combinations of salts and concentrations can affect the acid-neutralizing capacity of the antacid. The higher the neutralizing effect of the antacid, the more effective the antacid is. Keywords: Acid-neutralizing capacity; Antacid; pH; Dyspepsia; Erbil.

Effects of volcanic parent materials on the acid buffering capacity of forest soils on Yakushima Island, Japan

ABSTRACT Soil acidification is a natural pedogenetic process in forest ecosystems, but is accelerated by acidic deposition. Soils on Yakushima Island, in southwestern Japan, are derived from granitic bedrock and volcanic parent materials influenced by eolian dust inputs. Acid deposition and low acid-neutralizing capacity (ANC) of granite-derived soils are hypothesized to be the cause of acidic stream water that has been widely observed on Yakushima. It remains unclear, however, whether ANCs are also limited in volcanic soils, which contain weatherable minerals and have high buffering capacities. To compare acidification rates between granite-derived soils and volcanic soils, we estimated changes in ANCs between granite and volcanic parent materials and the resulting soils at a pedogenetic timescale, using the mass balance of titanium. After 7300 years of soil development following the eruption of the Kikai caldera, decreased ANCs and total base reserves were observed in both granite-derived and volcanic soils, compared to their respective parent materials. No difference in soil ANC was observed between granite and volcanic parent materials. Different cations contribute to acid neutralization in soils: decreasing ANC results primarily from the loss of Al in granite-derived soils, while acidity is neutralized by the loss of base cations from volcanic soils. In granite-derived soils, resistance to weathering and K retention in 2:1 type silicate clays limit the loss of bases while increasing the accumulation of exchangeable Al. In volcanic soil profiles, base leaching and the sorption of organic acids onto short-range order minerals can neutralize acidity, although erosion and admixing of granite or eolian dust-derived materials lead to a reduction of ANC in surface soil horizons.

PH dependent leachings of some trace metals and metalloid species from lead smelter slag and their fate in natural geochemical environment

The influence of pH on the leaching behaviours of As, Cd, Cu, Mo, Ni, Pb, Se and Zn from a lead smelter slag was assessed to understand the ground water pollution potential of slag and the toxicity in geo-environmental conditions. Leaching of slag was investigated by using European EN 12457-2 and prEN 14429 leaching tests. The results obtained from prEN 14429 leaching test were used to determine the acid neutralization capacity (ANC) of slag. The pH dependent leaching results were further assessed by considering existing geo-chemical modeling results of similar types of wastes. Results indicate that the concentrations of some toxic metal and metalloid species in the leachate are higher than their specified limits prescribed for safe landfill disposal as inert or non-reactive hazardous solid waste as well as for safe disposal of effluent in inland surface water. The ANC values obtained for slag at pH values 7, 5 and 4 are 0.75 meqv/g, 3.72 meqv/g and 37.30 meqv/g respectively. The low ANC values as well as the high concentrations of majority of the toxic elements in leachates especially at the pH range of 5–7 indicate hazardous nature of slag for disposal under open atmosphere. The leaching behaviours of iron and calcium under varying pH conditions have profound effect on the pH dependent mobilities of most of the trace elements present in the slag. The sodium, potassium and chloride leaching from slag particularly in the pH range of 4–12 are pH independent and therefore do not have any effect on the mobilities of toxic elements.

Trends of two decadal precipitation chemistry in a subtropical rainforest in East Asia

Long-term monitoring of precipitation chemistry provides a great opportunity to examine the evolution of air pollutant emissions and effectiveness of air pollution control measures. We evaluated the characteristics and trends of precipitation chemistry at both annual and seasonal scales based on the records of 1994–2013 at Fushan Experimental Forest (FEF) of northeastern Taiwan. The results showed that 77% of the weekly precipitation had pH<5.0. The two-decadal average annual pH was 4.62, without a significant inter-annual trend, possibly due to the concurrent declines of both acidic pollutants and base cations. There was a significant positive relationship between [SO42−+NO3−] and [Ca2++NH4+] indicating that their deposition was likely dominated by NH4NO3, (NH4)2SO4, Ca(NO3)2, and CaSO4. There was a significant negative relationship between precipitation pH and the difference between [SO42−+NO3−] and [Ca2++NH4+], not just [SO42−+NO3−], suggesting that precipitation acidity was not solely determined by acidic pollutants but by the balance between acidic pollutants and base cations. We also found temporal decreases of Ca2+ and NH4+ concentrations in precipitation which contributed to the low acid neutralization capacity of precipitation. Annual deposition of NO3− and SO42− was 23 and 55kgha−1yr−1, which is much higher than most forest sites in the industrialized countries suggesting that acid deposition is still a major environmental issue in Taiwan. Annual deposition of NH4+, Ca2+ and NO3− showed significant decreasing trends during the 20-year period, which was mostly due to the decreases in the summer deposition associated with air pollution mitigation strategies. Winter deposition showed no decreasing patterns for the same period. The high contribution to annual acid deposition from autumn-winter and spring rains (50%) associated with northeast monsoon implies that long-range transport of anthropogenic emissions from East Asia played a key role on acid depositions at FEF and possibly many areas in the region. Therefore, intergovernmental cooperation is urgently needed to effectively mitigate the threat of acid deposition in East Asia.

Limited acid deposition inferred from diatoms during the 20th century — A case study from lakes in the Tatra Mountains

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 1850AD. 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.

The effects of wildfire on the water chemistry of dilute, acidic lakes in southern Norway

Changes in lake water chemistry were studied for >4 years following a large wildfire in a boreal forest area in Mykland, southern Norway, an area characterized by thin and patchy, base-poor and slow-weathering soils and bedrock. Accordingly, the lakes have low acid neutralizing capacity (ANC), calculated as the difference between the total concentration of base cations ([ΣBC]) and strong acid anions ([SAA]). During the initial post-fire period, and peaking about two months after the fire, the mobilization of SAA from terrestrial to aquatic systems caused a dramatic drop in ANC. In one of the lakes, ANC dropped from about 20 to −80 μeq L−1, while [H+] and inorganic aluminum ([Ali]) increased to 38 μeq L−1 (pH 4.42) and 326 μg Al L−1 (36.2 μeq L−1 as Al3+), respectively. Sulfate and chloride were the predominant anions responsible for this decline in ANC, as the nitrate increase was small. After the severe chemical episode, [SAA] in the lakes declined faster than [ΣBC], and within about one year after the wildfire, ANC was back to almost pre-fire values. However, despite the fact that [SAA] also continued to decline faster than [ΣBC] the following years, no further increase in ANC was documented. The strong ionic strength decline and the increase in TOC during the same period have likely counteracted for the potential ANC increase. There were large lake-to-lake variations in water chemistry of the wildfire affected lakes. Hydrology, geology, lake residence time and the catchment area to lake area ratio are important explanatory factors.

Critical Loads of Acid Deposition for Wilderness Lakes in the Sierra Nevada (California) Estimated by the Steady-State Water Chemistry Model

Major ion chemistry (2000–2009) from 208 lakes (342 sample dates and 600 samples) in class I and II wilderness areas of the Sierra Nevada was used in the Steady-State Water Chemistry (SSWC) model to estimate critical loads for acid deposition and investigate the current vulnerability of high elevation lakes to acid deposition. The majority of the lakes were dilute (mean specific conductance = 8.0 μS cm−1) and characterized by low acid neutralizing capacity (ANC; mean = 56.8 μeq L−1). Two variants of the SSWC model were employed: (1) one model used the F-factor and (2) the alternate model used empirical estimates of atmospheric deposition and mineral weathering rates. A comparison between the results from both model variants resulted in a nearly 1:1 slope and an R 2 value of 0.98, suggesting that the deposition and mineral weathering rates used were appropriate. Using an ANClimit of 10 μeq L−1, both models predicted a median critical load value of 149 eq ha−1 year−1 of H+ for granitic catchments. Median exceedances for the empirical approach and F-factor approach were −81 and −77 eq ha−1 year−1, respectively. Based on the F-factor and empirical models, 36 (17 %) and 34 (16 %) lakes exceeded their critical loads for acid deposition. Our analyses suggest that high elevation lakes in the Sierra Nevada have not fully recovered from the effects of acid deposition despite substantial improvement in air quality since the 1970s.

Recycling of air pollution control residues from municipal solid waste incineration into lightweight aggregates

This work focuses on the assessment of technological properties and on the leaching behavior of lightweight aggregates (LWA) produced by incorporating different quantities of air pollution control (APC) residues from municipal solid waste (MSW) incineration. Currently this hazardous waste has been mostly landfilled after stabilization/solidification. The LWA were produced by pelletizing natural clay, APC residues as-received from incineration plant, or after a washing treatment, a small amount of oil and water. The pellets were fired in a laboratory chamber furnace over calcium carbonate. The main technological properties of the LWA were evaluated, mainly concerning morphology, bulk and particle densities, compressive strength, bloating index, water adsorption and porosity. Given that APC residues do not own expansive (bloating) properties, the incorporation into LWA is only possible in moderate quantities, such as 3% as received or 5% after pre-washing treatment.The leaching behavior of heavy metals from sintered LWA using water or acid solutions was investigated, and despite the low acid neutralization capacity of the synthetic aggregates, the released quantities were low over a wide pH range.In conclusion, after a washing pre-treatment and if the percentage of incorporation is low, these residues may be incorporated into LWA. However, the recycling of APC residues from MSW incineration into LWA does not revealed any technical advantage.

Mobilization and Toxicity Potential of Aluminum from Alum Floc Deposits in Kensico Reservoir, New York

AbstractThere is detailed literature on the mobilization of aluminum (Al) from soil to surface waters as a result of elevated acidic deposition to base‐poor forest watersheds. There is considerably less information on the mobilization and effects of Al from the application of alum that is used in some water supplies to control turbidity during high‐flow events. We report on the results of field measurements, laboratory sediment release experiments, and chemical equilibrium calculations conducted to evaluate the potential for the mobilization of Al from alum floc deposits in sediments of Kensico Reservoir, New York. Under ambient water quality conditions, mobilization of sediment Al is not a noteworthy concern at Kensico Reservoir. However, under experimental conditions of low pH, low acid neutralizing capacity (ANC), and low temperature, the inorganic fraction of monomeric Al can be mobilized from Kensico sediments to concentrations that would likely impair the health of aquatic organisms (&gt;2 μmol/l). Elevated concentrations of monomeric Al were observed only when ANC decreased below 50 μeq/l, which is outside the range of values observed in Kensico during the 1997‐2007 interval (120‐460 μeq/l). Concentrations of complexing ligands are relatively low in Kensico waters (i.e., fluoride, naturally occurring organic solutes) and do not appear to substantially contribute to potential Al mobilization. For other water supplies with low ANC, the potential for sediment release of Al may exist.

Mercury exposed: Advances in environmental analysis and ecotoxicology of a highly toxic metal

Mercury exposed: Advances in environmental analysis and ecotoxicology of a highly toxic metal

Machine learning and hurdle models for improving regional predictions of stream water acid neutralizing capacity

[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 < 100 µeq L−1), while <10% displayed much lower ANC (<50 µeq L−1). These methods may be readily adapted in other regions to assess stream water quality and potential biotic sensitivity to acidic inputs.

Lake/watershed sulfur budgets and their response to decreases in atmospheric sulfur deposition: watershed and climate controls

AbstractAtmospheric sulfur (S) emissions peaked in North America in the early 1970s followed by declines in S deposition and sulfate (SO42−) concentrations in surface waters. Changes in S biogeochemistry affect the mobilization of toxic (Al+3, H+) and nutrient (Ca2+, Mg2+, K+) cations, and the acid–base status of ecosystems. We focused on lake/watersheds in the Adirondack Mountains of New York, USA, one of the most acid‐sensitive and acid‐impacted regions in North America. We used 16 of the 17 original Adirondack Long‐Term Monitoring Lakes from 1984 through 2010 and found significant declines (−2.14 µmolc l−1 year−1) in SO42− concentrations. There were significant declines (−0.28 kg S ha−1 year−1) in total S deposition for all lake/watersheds. We constructed S mass balances for 14 lakes/watersheds from wet and dry S deposition and SO42− loss from drainage and found a comparable decline (−0.26 kg S ha−1 year−1) in lake SO42− export. There was a discrepancy (mean 2.34 kg S ha−1 year−1) between atmospheric S deposition and watershed S loss due to internal S sources. Using major solute chemistry including dissolved silica and watershed characteristics, it was evident that the watershed S budget discrepancy increased with thickness of surficial deposits. The annual discrepancies in S mass balances were strongly linked with annual watershed discharge. These results suggest that internal S sources are becoming increasingly important as atmospheric S inputs have declined. The internal SO42− supply of watersheds decreased concomitantly with lake acid neutralizing capacity (ANC). These findings suggest that the limited contributions from internal sources of SO42− will facilitate the recovery of ANC from those lake/watersheds with the lowest ANC. With long‐term decreases in atmospheric S deposition, the effects of climate, especially increases in precipitation, will play an increasingly important role in regulating S budgets and the amount of SO42− mobilized from internal watershed sources. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Evaluation of cost effectiveness and efficacy of commonly used different antacid gel preparations

Background: Gastroesophageal reflux disease (GERD) is a common clinical condition in Indian population. Antacids, which are available as over the counter (OTC) are the commonly prescribed drugs for treatment of GERD. Antacids manufactured and marketed by various multinational and local companies are available in the market. There is need for evaluating the cost effectiveness and efficacy of these antacids as a matter of public concern. Hence the present study was conducted to evaluate the cost effectiveness and efficacy of the commonly prescribed antacid gel preparations. Methods: Seven different gel formulations of antacids manufactured by different companies were evaluated. Cost effectiveness was done by calculating the cost per ml of antacid and also by palatability test. Efficacy was evaluated based on acid neutralizing capacity (ANC) of antacid preparations. Results: The highest cost was 0.305 Rs. per ml and lowest was 0.135 Rs per ml. Palatability score was high at 26.80 and low at 23.85. The antacid with lowest ANC was 20.5 mEq and the highest was 26.5 mEq. Conclusion: Cost effectiveness studies are beneficial in improving the prescribing pattern. It will be a benefit for both doctor as well as patient.

Watershed-Level Responses to Calcium Silicate Treatment in a Northern Hardwood Forest

Watershed 1 (W1) at the Hubbard Brook Experimental Forest in New Hampshire, with chronically low pH and acid neutralizing capacity (ANC) in surface water, was experimentally treated with calcium silicate (CaSiO3; wollastonite) in October 1999 to assess the role of calcium (Ca) supply in the structure and function of base-poor forest ecosystems. Wollastonite addition significantly increased the concentrations and fluxes of Ca, dissolved silica (Si), and ANC and decreased the concentrations and fluxes of inorganic monomeric Al (Ali) and hydrogen ion (H+) in both soil solution and stream water in all sub-watersheds of W1. Mass balances indicate that 54% of the added Ca remained undissolved or was retained by vegetation during the first 6 years after treatment. Of the remaining added Ca, 44% was retained on O horizon cation exchange sites. The Ca:Si ratio in the dissolution products was greater than 2.0, more than twice the molar ratio in the applied wollastonite. This suggests that Ca was preferentially leached from the applied wollastonite and/or Si was immobilized by secondary mineral formation. Approximately 2% of the added Ca and 7% of the added Si were exported from W1 in streamwater in the first 6 years after treatment. Watershed-scale Ca amendment with wollastonite appears to be an effective approach to mitigating effects of acidic deposition. Not only does it appear to alleviate acidification stress to forest vegetation, but it also provides for the long-term supply of ANC to acid-impacted rivers and lakes downstream.

Rapid synthesis of hydrotalcite with high antacid activity

The hydrotalcite has been synthesized using Al/Mg molar ratios of 1.0–3.0 by grinding at room temperature for 5min. It shows maximum acid neutralization capacity (285ml). When hydrotalcite was prepared hydrothermally (175°C) and by refluxing (80°C) method it shows low acid neutralization capacity (i.e. 20 and 200ml respectively). Hydrotalcite has been characterized by FT-IR, TG and P-XRD. The powder X-ray diffraction analysis values 77.638, 3.777, 2.362, 2.218, 1.876Å support double layer hydroxide structure. It is a rapid and cost effective procedure.

Relating hydrogeomorphic properties to stream buffering chemistry in the Neversink River watershed, New York State, USA

AbstractMonitoring the effects of acidic deposition on aquatic ecosystems in the Northeastern US has generally required regular measurements of stream buffering chemistry (i.e. acid‐neutralizing capacity (ANC) and calcium Ca2+), which can be expensive and time consuming. The goal of this paper was to develop a simple method for predicting baseflow buffering chemistry based on the hydrogeomorphic properties of ten nested watersheds in the Neversink River basin (2·0–176·0 km2), an acid‐sensitive basin in the Catskill Mountains, New York State. The tributaries and main reach watersheds have strongly contrasting mean baseflow ANC values and Ca2+ concentrations, despite rather homogeneous vegetation, bedrock geology, and soils. A stepwise regression was applied to relate 13 hydrogeomorphic properties to the mean baseflow ANC values and Ca2+ concentrations. The regression analysis showed that watersheds with lower ANC values had a higher mean ratio of ‘quickflow’ runoff to precipitation during 20 non‐snowmelt runoff events (referred to as mean runoff ratio). The mean runoff ratio could explain at least 80% of the variability in mean baseflow ANC values and Ca2+ concentrations among the ten watersheds. Greater mean runoff ratios also correlated with steeper slopes and greater drainage densities, thus allowing the prediction of baseflow ANC values (r2 = 0·75) and Ca2+ concentrations (r2 = 0·77) with widely available spatial data alone. These results indicate that hydrogeomorphic properties can predict a watershed's sensitivity to acid deposition in regions where the spatial sources of stream buffering chemistry from the bedrock mineralogy and soils are fairly uniform. Copyright © 2010 John Wiley &amp; Sons, Ltd.

The Relationship between Adirondack Lake pH and Levels of Mercury in Yellow Perch

Levels of total mercury in yellow perch Perca flavescens from Adirondack lakes were studied in relation to characteristics of the lakes to determine why some lakes had fish with higher concentrations of mercury. Almost all mercury in fish is in the form of methylmercury, which can pose significant health hazards to humans who consume such fish. Fish mercury concentrations and water chemistry data were analyzed from eight Adirondack lakes. Four lakes (Halfmoon Lake, Sand Pond, Rock Pond, and Upper Sister Lake) had pH values of less than 5.0. Four other lakes (Lake Adirondack, Kings Flow, Harris Lake, and Lake Kushaqua) had pH values of more than 7.0. The acidic lakes also had high levels of aluminum and low acid-neutralizing capacity relative to the neutral lakes. Yellow perch (n = 100) from the acidic lakes had significantly higher levels of mercury than did those (n = 102) from the neutral lakes (P < 0.001), and the total mercury concentration increased with both length and weight of the fish. We conclude that the pH of the lake water is a major factor in determining the concentration of methylmercury in yellow perch.