pH Depression Research Articles

Chemistry of Tension Lysimeter Water and Lateral Flow in Spruce and Hardwood Stands

AbstractThe concentrations of H+, NO−3, SO2−4, soluble Al, and undissociated acidity were measured in throughfall, soil solution, and streamflow during five rainfall events on two steeply sloping forested sites in the Great Smoky Mountains. The sources and sinks of these chemical species on a spruce‐birch (Picea rubens Sarg.‐Betula lenta L.) site were compared to those on a hardwood site. The chemistry of water collected in zero‐tension lateral flow collectors during storm events was contrasted with water collected at corresponding depths in tension lysimeters. Tension lysimeter samples from the spruce site had much higher concentrations than those from the hardwood site of H+ (3–7 ×), SO2−4 (1.5–2 ×), Al (2–5 ×), and undissociated acidity (1.5–2 ×). Baseflow from a first‐order stream draining the spruce site was significantly higher in Al and H+ than hardwood site baseflow. On both sites the largest sources of H+ and undissociated acidity were throughfall (incident precipitation + canopy sources) and the O horizon; on the spruce site the O horizon was the predominant source of each. Aluminum and SO2−4 also increased dramatically with passage through the O horizons, especially on the spruce site. Only the spruce site generated appreciable lateral flow. Nitrate, undissociated acidity, and Al concentrations in spruce site lateral flow were not significantly (p <0.05) different from those in corresponding tension lysimeter samples. Electrical conductivity and concentrations of H+ and SO2−4, however, were higher in lateral flow from spruce site B horizons than in corresponding tension lysimeter water. Reduced soil contact time and contact surface area were hypothesized reasons for the ineffectiveness of these B horizon sinks with regard to rapid lateral flow. Lateral flow pathways on the spruce site may have also bypassed sinks for Al and undissociated acidity that exist in the lower mineral horizons and bedrock zone. Stream pH depressions during stormflow may be related to rapid subsurface flow and interflow emanating from these acidic spruce‐birch sites.

Effects of Elevated H + , SO 4   2- , NO 3   - and NH 4   + in Simulated Acid Precipitation on the Growth and Chlorophyll Content of 3 North American Sphagnum Species

Acid precipitation has been implicated as causing the loss of Sphagnum species, and thus of Sphagnum peatlands from the southern Pennines in Great Britain. Thus, the effects of pH, SO42-, NO,-, and NH4+, at levels feasible for acid precipitation in eastern North America, on the growth and chlorophyll contents of Sphagnum fallax, S. henryense and S. pulchrum were evaluated in 40-50 day laboratory studies. Growth responses were species-specific, and also differed between two populations of S. pulchrum collected from different locations. In general, growth was not correlated with chlorophyll concentrations. If the acidity in precipitation lowers wetland pH values to 3 or less, growth of Sphagnum species in general will be inhibited. Otherwise, our results do not suggest that elevated concentrations of H+, SO42-, NO,-, and NH4+ in acid precipitation will have severe negative short-term effects on Sphagnum growth, at least for these 3 species. One of the earliest suggestions that acid precipi- tation may negatively impact Sphagnum-dominat- ed peatland ecosystems was that of Tallis (1964), who commented that the disappearance of Sphag- num species from the southern Pennines in Great Britain may have been the result of atmospheric pollution dating from the Industrial Revolution. Only 5 Sphagnum species were present in 1964 as compared to 18 species in 1913 (Ferguson & Lee 1983). Ombrotrophic Sphagnum bogs may be es- pecially susceptible to the chemistry of precipita- tion, since these bogs rely exclusively on atmo- spheric deposition as a source of both water and nutrients (Kilham 1982; Gorham et al. 1983). In the absence of acid precipitation, bogs are nat- urally acidic, with surface water pH values of about 4.0 (Clymo 1984); however, in the presence of acid precipitation, a significant pH depression can result (Hemond 1980; Clymo 1984). Since pH is an im- portant environmental variable affecting the success of individual species of Sphagnum in the field (see review by Andrus 1986), increasing acidity of sur- face bog waters resulting from acid precipitation may affect Sphagnum species and thereby the struc- ture of Sphagnum communities. Atmospheric sul- fur compounds associated with acid precipitation (SO2, HS03-, SO42-) have inhibitory effects on the growth, photosynthesis, and survival of Sphagnum

APPLICATION OF THE ILWAS MODEL TO THE NORTHERN GREAT LAKES STATES

ABSTRACT In the northern Great Lakes States, seepage lakes are considered more vulnerable to acidification than drainage lakes. The ILWAS model, which was developed for drainage lakes in the Adirondack Mountain Region of New York, has been revised for use in seepage lake systems. Contrasts were observed between the Wisconsin seepage lakes and the drainage lakes in the Adirondack Region of New York. (1) Atmospheric loading of hydrogen and sulfate ions was 77 and 62 percent respectively, lower in Wisconsin. (2) In contrast to the low alkalinity flow-through lakes in the Adirondacks, there are no observed spring pH depressions associated with snowmelt in Wisconsin seepage lakes. (3) Because of deep glacial deposits (32–190 m) at the Wisconsin sites, a longer contact time between groundwater and weatherable minerals provides a substantial buffering capacity via silicate hydrolysis. (4) Inlake alkalinity production by bacterial sulfate reduction in the sediments of Wisconsin seepage lakes plays a significant r...

Behaviour and ecology of salmonid fishes exposed to episodic pH depressions

The behaviour and ecology of lake charr Salvelinus namaycush, brook charr S. fontinalis, and Atlantic salmon Salmo salar, are reviewed to assess the susceptibility of these species to mortality from exposure to episodic pH depressions and accompanying changes in water quality. Critical life history periods are identified from an examination of: spawning site characteristics, timing of ‘acidic pulses’, changes in the sensitivity of developing fish to acidic water, and the ability of these species to detect and avoid deleterious chemical conditions. The three species appeared to be most vulnerable to pH depressions during Snowmelt as: alevins emerging from the redd (brook charr); free embryos in the interstitial spaces of the spawning rubble (lake charr); and embryos during hatching and juveniles during smoltification (Atlantic salmon). Factors that may modify the toxic effects of or the behavioural responses to low pH included: water temperature, acclimation and body energy reserves. The effect of site-specific or episodic mortality of early life history stages on recruitment to the population could not be evaluated due to the lack of information on compensatory mechanisms.

Water quality improvements in the Sudbury, Ontario, Canada area related to reduced smelter emissions

Data from water quality studies conducted in the Sudbury, Ontario, Canada area indicate that substantial decreases in the acidity of surface waters have accompanied reductions in SO2 emissions from the Sudbury smelting industry since 1977. On average, acidic lakes in the Sudbury area showed a decrease in H+ of ∼ 50% between 1974–76 and 1981–83, and the severity of springtime pH depressions in streams decreased. Although many Sudbury area surface waters remain highly acidic, general decreases in acidity appear to be continuing. The results demonstrate that reductions in emissions of acids and acid precursors result in concomitant improvements in water quality.

Oxygen-18 studies of snowmelt runoff in a small Precambrian shield watershed: Implications for streamwater acidification in acid-sensitive terrain

Oxygen-18 tracer studies of snowmelt runoff in the Turkey Lakes watershed, Ontario, Canada indicate that 50–60% of the peak runoff is derived from premelt groundwater in storage in the surficial deposits. Groundwater in the stream valleys has relatively high alkalinity concentrations from silicate and minor detrital carbonate dissolution which neutralize much of the acidity in the meltwater component of runoff when it is discharged into the stream during meltwater infiltration. However shallow groundwater on the hillslopes is susceptible to acidification from infiltrating meltwater and rapid flushing to small, first-order streams. For this reason first-order headwater streams experience greater pH depression than do higher-order streams in well defined stream channels, despite having similar premelt components.

Acid-base regulation and ion transfers in the carp (Cyprinus carpio): pH compensation during graded long- and short-term environmental hypercapnia, and the effect of bicarbonate infusion.

To study both temporal and quantitative effects of hypercapnia on the extent of pH compensation in the arterial blood, specimens of carp (Cyprinus carpio) were exposed to a PCO2 of about 7.5 mmHg (1 mmHg = 133.3 Pa) (1% CO2) in the environmental water for several weeks, and a second group of animals was subjected to an environmental PCO2 of about 37 mmHg (5% CO2) for up to 96 h. A third series of experiments was designed to test the possibility that infusion of bicarbonate would increase the extent of plasma pH compensation. Dorsal aortic plasma pH, PCO2 and [HCO3-], as well as net transfer of HCO3- -equivalent ions, NH4+, Cl- and Na+, between fish and ambient water, were monitored throughout the experiments. Exposure to environmental PCO2 of 7.5 mmHg resulted in the expected respiratory acidosis with the associated drop in plasma pH, and subsequent compensatory plasma [HCO3-] increase. The compensatory increase of plasma bicarbonate during long-term hypercapnia continued during 19 days of exposure with plasma bicarbonate finally elevated from 13.0 mmoll-1 during control conditions to 25.9 mmoll-1 in hypercapnia, an increase equivalent to 80% plasma pH compensation. Exposure to 5% hypercapnia elicited much larger acid-base effects, which were compensated to a much lesser extent. Plasma pH recovered to only about 45% of the pH depression expected at constant bicarbonate concentration. At the end of the 96-h exposure period, plasma [HCO3-] was elevated by a factor of 2.5 to about 28.2 mmoll-1. The observed increase in plasma bicarbonate concentration during 5% hypercapnic exposure was attributable to net gain of bicarbonate equivalent ions from (or release of H+-equivalent ions to) the environmental water. Quantitatively, the gain of 15.6 mmol kg-1 was considerably larger than the amount required for compensation of the extracellular space, suggesting that acid-base relevant ions were transferred for compensation of the intracellular body compartments. The uptake of bicarbonate-equivalent ions from the water was accompanied by a net release of Cl-and, to a smaller extent, by a net uptake of Na+, suggesting a 75% contribution of the Cl-/HCO-3 exchange mechanism. Infusion of bicarbonate after 48 h of exposure to 7.5 mmHg PCo2 had only a transient effect on further pH compensation. The infused bicarbonate was lost to the ambient water, and pre-infusion levels of bicarbonate were reattained within 24 h. Repetition of the infusion did not result in a notable improvement of the acid-base status.(ABSTRACT TRUNCATED AT 400 WORDS)

Chemical Factors Involved in Ruminal Fiber Digestion

In the United States, cattle are commonly fed diets containing cereal grains. The presence of starch and sugars reduces fiber digestion, which may in turn depress intake.In this paper, chemical constraints that may be responsible for the decrease in fiber digestion are explored. A major factor appears to be rumen pH. Moderate depression in pH, to approximately 6.0, results in a small decrease in fiber digestion, but numbers of fibrolytic organisms are usually not affected. Further decreases to 5.5 or 5.0 result in depressed growth rates and decreased fibrolytic microbes, and fiber digestion may be completely inhibited.Proliferation of organisms on readily fermentable carbohydrates may increase the need for total nitrogen as both ammonia and amino acids. The value of amino acids to cellulolytic organisms appears to be primarily as sources of isobutyric, isovaleric, and 2-methylbutyric acids. This reinforces the need to establish dietary requirements for nonprotein nitrogen, degradable protein, and isoacids.Other factors affecting fiber digestion, such as inhibition of cellulytic enzymes and plant concentrations of lignins and phenyl propanoids, are also discussed.

Aluminum speciation in running waters on the Canadian pre-Cambrian Shield: Kinetic aspects

To evaluate the extent to which chemical disequilibrium may exist in stream waters following naturally occurring short-term pH changes, surface water samples were collected from two streams in the Lake Laflamme watershed north of Quebec City, placed in large polyethylene containers and stirred continuously at the in situ temperature; changes in Al speciation were followed with time for up to 24 hr. The original samples were collected during the spring snow-melt period and during summer low flows. In this latter case, a pH depression was induced by artificial acidification (H2SO4; pH 4) and changes in Al speciation with time were followed in both the acidified and the unacidified samples. Aluminum speciation as operationally defined did respond to artificial acidification (pH lowered; non-exchangeable and non-extractable Al decreased), and these pH-induced changes occurred rapidly (< 4 hr). During storage of natural water samples at in situ T for up to 24 hr, little change in Al speciation was noted, even in the case of samples collected during spring snow-melt; no clear cases of chemical disequilibrium existed among the studied samples. The distribution of Al among its various physico-chemical forms thus appears to be established within the stream itself; at a given stream sampling point the speciation of A1 will not necessarily reflect its geochemical origins, but rather the prevailing in situ conditions (e.g. pH, ligand concentrations).

Comparison between two methods of feeding concentrate to sheep given a diet high or low in concentrate with or without buffering substances

The disappearance of washed hay from nylon bags incubated in the rumen was compared when rumen cannulated sheep were fed concentrate separately twice daily, four times daily or mixed with the hay in diets consisting of 0.65 concentrate and 0.35 hay. In another trial, two ratios of concentrate were compared (either 0.40 or 0.65) and two methods of feeding the concentrate, either twice daily or completely mixed with the hay. At the high level of feeding the concentrate (0.65), the rate of dry matter disappearance of hay was greater in the rumen of animals receiving concentrate twice daily in comparison with completely mixed or four times daily. In vivo digestibility of hay was also greatest. At the lower level of concentrate feeding (0.40), there were no differences between feeding methods. A considerable part of the differences between treatments and methods of feeding could be explained by changes in rumen pH, but while the average rumen pH was a poor indicator of depression in fibre digestion ( r = 0.47) it was better correlated with the summation of pH depression below pH 6 (pH × h; r = 0.74). Addition of bicarbonate in the experiments here had no significant effect on dry matter losses in the rumen.

Acid‐base disturbances following exercise in a high‐shore crab,Cyclograpsus lavauxi

Abstract Cyclograpsus lavauxi, a high‐shore crab, suffered a marked acidosis after 10 minutes of moderate exercise in air because of increases in haemolymph lactate concentration and PCO2. During recovery in sea water, the levels of lactate and PCO2 decreased rapidly and resting pH was restored within 2 h. In air, lactate was also metabolised rapidly, but PCO2 levels declined more slowly than in water and were partly the reason for the continued depression of haemolymph pH at 24 h. There were discrepancies between the concentrations of lactate anions and metabolic protons in the haemolymph during recovery. Protons were removed more rapidly than lactate anions in sea water, which suggests that branchial excretion of acid, and/or uptake of base, was involved in acid‐base regulation. The metabolic acid load persisted throughout recovery in air and was, despite possible buffering by mobilisation of CaCO3, mainly responsible for the continued depression of haemolymph pH. It is concluded that sea water is neces...

The effect of short-term acidification during spring snovvmelt on selected Mollusca in south-central Ontario

Limestone and sulfuric acid were used to manipulate the pH of water in three artificial channels in the outflow of Plastic Lake, south-central Ontario, during the spring of 1982. Using artificial channels allowed the manipulation of pH during a natural pH depression (i.e., spring snowmelt) while minimizing confounding factors such as mobilization of metals from aquatic sediments. Addition of sulfuric acid extended and exaggerated the natural pH depression (from pH 5.8 to 4.8) to as low as pH 3.5 over 5 days, while addition of limestone prevented depression of pH below 6.4. Survival and reproduction of the pisidiid clams Pisidium equilaterale Prime and Pisidium casertanum (Poli) and the hydrobiid snail Amnicola limosa Say held in artificial channels were not significantly different (p &gt; 0.05) among treatments. The survival and reproduction of A. limosa was also not affected by exposure to short-term pH depressions (e.g., 5.8 to 4.8; 4.8 to 4.3) in three south-central Ontario streams during spring snowmelt. For various life stages of both P. equilaterale and A. limosa, 96-h LC50 values were below pH 4.0, which was well below the pH observed in any stream in this study. These results suggest that recruitment failure and elimination of A. limosa from acidifying lakes noted in other studies was not a direct result of short-term pH depression during snowmelt.

Impact of acid mine-drainage from abandoned spoils on the chemistry of an intermittent stream in the arid Southwest

Drainage from an orphaned copper mine (Sheldon Mine Complex) contributes highly mineralized, acidic waters to Lynx Creek, a small intermittent, arid-climate stream. This results in localized elevation of major cations, silica, sulfate, and heavy metals (Cu, Fe, Mn, Zn), depression in pH, and complete neutralization of bicarbonate alkalinity. Levels of chloride, nitrogen and phosphorus are unaffected by mine-drainage. During stable flow, water quality of the creek improves downstream through precipitation of metal salts, dilution by less mineralized tributaries, and additional buffering from the creek channel and tributaries. Climatic aridity, via high evaporation, concentrates and precipitates metal salts during summertime periods of low flow. Creek sediments thus contain large amounts of heavy metals and phosphorus that are transported downstream in suspended particulates during spates. This reflects an annual cycle of temporary creek-bed storage followed by episodic mobilization toward Lynx Lake, a downstream reservoir. Although the influence of mine drainage is not overtly apparent in the dissolved chemistry of the Lake, high concentrations of metals and phosphorus occur in lake sediments.

The Role of Groundwater in Delaying Lake Acidification

Models used to study lake acidification generally divide a watershed into several zones or compartments (e.g., soil and groundwater zones) through which water and chemicals are routed. To date most emphasis has been placed on the buffering of acid inputs by chemical reactions in the soil zone. Although buffering in the soil zone undoubtedly is important, the focus of this paper is the role of the groundwater system in delaying lake acidification. In this study, a deterministic approach was selected over the standard parametric modeling used in watershed models. Specifically, an advection‐dispersion model of the groundwater system was linked to a simple groundwater‐rain‐lake mixing model, which in turn was linked to a geochemical speciation and reaction path model. Simulations of hypothetical groundwater‐lake systems utilized chemical data from small lake systems in northern Wisconsin, an area which is currently experiencing acid rain (pH = 4.6) and is potentially sensitive to acid rain impacts owing to the absence of carbonate minerals in the underlying glacial tills and bedrock. Results of the modeling studies demonstrated that even when the effects of chemical reactions are ignored, groundwater inflow can mitigate the effects of acid deposition on lakes. When chemical reactions in the groundwater system were included in the model using a retardation factor, the acidification rate of the lake was significantly decreased. When speciation reactions between lake water and net acid additions were simulated using the geochemical model PHREEQE (Parkhurst et al., 1980), the depression of lake water pH was markedly reduced, indicating that low alkalinity lakes, like the ones in northern Wisconsin, may have appreciable buffering capacity.

Depression of iron uptake from transferrin by isolated hepatocytes in the presence of ethanol is a pH-dependent consequence of ethanol metabolism.

Incubation of freshly isolated rat hepatocytes with highly purified radiolabeled rat transferrin in weakly buffered medium in the presence of 10 mM ethanol resulted in a marked diminution of iron uptake by these cells, associated with a greater pH depression than in ethanol-free control studies. This effect on iron uptake persisted, even when the cells were preincubated for 90 min with ethanol before the addition of transferrin. Increasing the buffering capacity of the system or the addition of a metabolic inhibitor of alcohol dehydrogenase (4-methylpyrazole) returned iron uptake to control values. Acetaldehyde, acetate, lactate (products of ethanol metabolism), and 3-butanol (an alcohol not metabolized by alcohol dehydrogenase) had no influence on iron uptake. Further investigation of iron uptake over the pH range 6-8.5 revealed a marked dependency of iron uptake on the extracellular pH. Leucine incorporation into cell protein was also found to be pH dependent. It is suggested that, in the light of current understanding of transferrin recycling by other cell types, the disturbances of iron homeostasis observed in alcoholics can be partially accounted for by alterations in their acid-base metabolism.

Effects of fluorides on in vitro acid production by dental plaque.

A method that holds human dental plaque on a glass micro-electrode has been used to measure the pH depressions in plaque samples exposed to different concentrations of fluoride from sodium fluoride or sodium monofluorophosphate. Fluoride from both sources gave some inhibition of sucrose-induced acid formation at levels as low as 10 ppm and parallel results at other test concentrations of up to 200 ppm F. Repeated exposures of plaque to fluoride solutions did not interfere with its subsequent ability to ferment sucrose.

Model for Streamwater Chemistry of a Tributary to Harp Lake, Ontario

The model is an extended version of the "Birkenes" model and consists of a hydrological submodel with a snow reservoir and two soil reservoirs, a sulphate submodel, and a submodel including H+, Ca2+ + Mg2+, Al, Na+, [Formula: see text], and organic anions. Major processes incorporated are different hydrologic flow patterns during highflow and lowflow, [Formula: see text] adsorption/desorption, ion exchange, weathering, gibbsite solubility, and equilibria with CO2 in soil and stream water. The model reproduces important daily and seasonal trends in the observed streamwater chemistry. Tentative model runs have been carried out to simulate the effects of both a doubling and a 50% reduction in the present sulphur deposition. At present the pH of the stream is generally above 5.7, with values approaching pH 5.3 during snowmelt highflow. According to the simulations, lowflow pH is not sensitive to changes in deposition. At snowmelt highflow, however, a 50% reduction in the deposition could cause a pH increase of 0.2–0.5 unit whereas a doubling could result in pH depressions of 0.5–0.9 unit.

Dietary cimetidine and copper in Eimeria acervulina-infected chicks.

The effects of varying levels of cimetidine (N"-cyano-N-methyl-N'-(2-[(5-methylimidazol-4-yl)methylthio]-ethyl ) guanidine) on Eimeria acervulina (duodenal coccidiosis)-induced changes in gain, efficiency, duodenal pH, and liver copper concentration of chicks were investigated. In a preliminary trial, gain, efficiency, and duodenal pH were significantly reduced in chicks inoculated one time with 1 X 10(6) sporulated oocysts. Dietary addition of 121 ppm monensin (2-[5-ethyltetrahydro-5-[tetrahydro-3-methyl-5-[tetrahydro-6-hydro xy-6- (hydroxymethyl)-3,5-dimethyl-2H-pyran-2-yl]-2-furyl]-2-furyl]-9-hydroxy- beta-methoxy-alpha, gamma, 2,8-tetramethyl-1,6-dioxaspiro[4.5]decane-7-butyric acid) prevented these coccidiosis-induced aberrations. In subsequent trials, growth rate, feed efficiency, and duodenal pH were reduced by E. acervulina infection, but were unaffected (P greater than 0.10) by dietary addition of 0.01% cimetidine. Linear depressions (P less than 0.05) in gain and efficiency, however, were observed from 0.05 and 0.10% cimetidine additions. Dietary addition of 500 ppm copper increased liver copper levels thirtyfold (P less than 0.01) after 2 weeks. Significant coccidiosis X copper interactions were detected in gain, efficiency, duodenal pH reduction, and liver copper elevation of chicks repeatedly inoculated with 4 X 10(5) sporulated E. acervulina oocysts. Coccidiosis increased liver copper levels (P less than 0.01) of chicks fed excess copper an additional threefold compared with uninfected chicks fed excess copper. Dietary additions of 0.01, 0.05 or 0.10% cimetidine were ineffective in preventing coccidiosis-associated performance and duodenal pH depressions as well as the coccidiosis-induced liver copper elevation. Apparently, host response to cimetidine is minor in comparison to effects of coccidia on duodenal pH. Increased copper solubility at low duodenal pH may explain high tissue copper levels and enhanced copper toxicity due to coccidiosis.

Lake Acidification as a Limiting Factor in the Distribution of the Freshwater Amphipod Hyalella azteca

The distribution of the freshwater amphipod Hyalella azteca in 79 Ontario lakes suggests that its absence may be a good indicator of lake acidification. Hyalella azteca was present in 69 of 71 nonacidified lakes, and absent in 8 of 8 lakes which either are now ar recently were considered acidified. Bioassay data indicate a 96-h LC50 of pH 4.4 and a 10-d threshold LC50 of pH 4.5 for H. azteca in a natural surface water. Hyalella azteca is extremely rare in Plastic Lake, which undergoes severe short-term acidification in spring, and recruitment is delayed 2 wk in Heeney Lake which undergoes similar short-term acidification, in Dickie, Harp, Red Chalk, and Blue Chalk lakes, where springtime pH depressions below pH 4.7 were not recorded, H. azteca is abundant.

Changes in Plaque pH in vitro by Sweeteners

A new in vitro pH method was used to compare the ability of natural dental plaque to convert nine sweeteners to acid. Tests made in 0.1, 1.0, and 10.0% concentration, or sucrose sweetener equivalents, showed that isomaltulose gave the lowest pH, followed in order by Lycasin, mannitol, palatinit, sorbitol, sorbose, and then, with negligible acid production, aspartame, saccharine, and xylitol. Unlike the other sweeteners, xylitol and saccharine gave smaller pH depressions in higher concentrations of test solutions. At the concentrations tested, none of the sweeteners interfered with acid production from sucrose.