Acidity status of surface waters in Massachusetts

The Massachusetts Acid Rain Monitoring project surveyed 80.5% of the state's 5294 named water bodies between 1983 and 1985. PH and acid neutralizing capacity (ANC) were measured monthly the first 14 mo and semi-annually afterwards. Sample collection and analysis were performed by volunteers. The majority of surface waters in Massachusetts were found to be sensitive to possible long term acidification, with 63% exhibiting ANC less than 200 μeq L^?1 and 22% with ANC less than 40 μeq L^?1. Seasonal patterns in ANC were observed, the median ANC being 384 μeq L^?1 in summer/fall and 134 μeq L^?1 in winter/spring. Geographical differences were also found across the state: the streams and lakes with lowest pH and ANC were located in the southeastern and north-central parts of the state, while the most alkaline surface waters were found in the western-most part of the state, which is the only area of the state with significant limestone deposits.     

Extreme acidification of a lake in southern Norway caused by weathering of sulphide-containing bedrock

In 1986 Lake Langedalstjenn in southern Norway was a weakly acidified lake with a pH of 5.2–5.6, and an average concentration of SO₄ of 330 μeq L^?1. The total Al concentration varied between 10 and 20 μeq L^?1 (expressed as Al³⁺). The lake supported populations of brown trout and perch and had supplied about 100 people with drinking water until the late 1980's. During 1986–1989, a dramatic change in the water chemistry occurred because of blasting of and weathering of sulphidic gneisses in the watershed. The oxidation of sulphide to sulphate (sulphuric acid) caused an increase in the SO₄ concentration of the draining stream of up to ≈ 4800 μeq L^?1. Weathering and/or cation exchange of Ca and Mg neutralized approximately 52% of the protons from the sulphuric acid production, while about 46% were consumed by mobilization of aluminium and iron. Nevertheless, about 2% of the hydrogen ions from the sulfuric acid were still present, which resulted in a stream pH of 4.0. In the lake, the pH was 4.4, and the concentrations of all major cations and anions were significantly lower than in the heavily affected stream. Mixing of the stream water with lake water, formation of aluminium-sulphate complexes and coprecipitation of Ca may explain the resulting concentrations of major ions in the lake.     

Chemical characteristics and temporal trends in eight streams of the Catskill Mountains,New York

Discharge to concentration relationships for eight streams studied by the U.S. Geological Survey (USGS) as part of the U.S. Environmental Protection Agency's (U.S. EPA) Long-Term Monitoring Project (1983–89) indicate acidification of some streams by H₂SO₄ and HNO₃ in atmospheric deposition and by organic acids in soils. Concentrations of major ions in precipitation were similar to those reported at other sites in the northeastern United States. Average concentrations of SO₄ ^2? and NO₃ ^? were similar among streams, but base cation concentrations differed widely, and these differences paralleled the differences in acid neutralizing capacity (ANC). Baseflow ANC is not a reliable predictor of stream acidity at high flow; some streams with high baseflow ANC (>150 Μeq L^?1) declined to near zero ANC at high flow, and one stream with low baseflow ANC (<50 Μeq L^?1) did not approach zero ANC as flow increased. Episodic decreases in ANC and pH during peak flows were associated with increased concentrations of NO₃ ^? and dissolved organic carbon (DOC). Aluminum concentrations exceeding 300 Μg L^?1 were observed during peak flows in headwater streams of the Neversink River and Rondout Creek. Seasonal Kendall Tau tests for temporal trends indicate that SO₄ ^2? concentrations in streamwater generally decreased and NO₃ ^? concentrations increased during the period 1983–1989. Combined acid anion concentrations (SO₄ ^2? + NO₃ ^?) were generally unchanged throughout the period of record, indicating both that the status of these streams with respect to acidic deposition is unchanged, and that NO₃ ^? is gradually replacing SO₄ ^2? as the dominant acid anion in the Catskill streams.     

Change in the acid-base status of an appalachian mountain catchment following forest defoliation by the gypsy moth

Infestation by the gypsy moth (Lymantria dispar) can alter biogeochemical conditions in affected catchments. Stream-water concentration data obtained over the period of 1980–1993 for White Oak Run, a stream in Shenandoah National Park, Va., indicate that change in catchment acid-base status is associated with forest defoliation by the moth larva. Stream-water concentration changes following defoliation included increasing concentrations of strong-acid anions, base-cations, and hydrogen ion, as well as decreasing concentrations of acid-neutralization capacity (ANC) and sulfate. The largest change was in the concentration of nitrate; annual discharge-weighted mean concentrations increased from predefoliation levels consistently less than 5 μeq L^?1 to postdefoliation levels greater than 50 μeq L^?1. An intensification of acidification was indicated by record-high hydrogen ion concentrations and record-low ANC concentrations. The long-term biogeochemical implications of the infestation are uncertain due to the nonlinearity of the observed responses and unknown patterns of recovery and recurrence.     

Acid-base chemistry of high-elevation streams in the great smoky mountains

Longitudinal and temporal variations in water chemistry were measured in several low-order, high-elevation streams in the Great Smoky Mountains to evaluate the processes responsible for the acid-base chemistry. The streams ranged in average base flow ANC from ?30 to 28 μeq L^?1 and in pH from 4.54 to 6.40. Low-ANC streams had lower base cation concentrations and higher acid anion concentrations than did the high-ANC streams. NO₃ ^? and SO₄ ^2? were the dominant acid anions. NO₃ ^? was derived from a combination of high leaching of nitrogen from old-growth forests and from high rates of atmospheric deposition. Streamwater SO₄ ^2? was attributed to atmospheric deposition and an internal bedrock source of sulfur (pyrite). Although dissolved Al concentrations increased with decreasing pH in the study streams, the concentrations of inorganic monomeric Al did not follow the pattern expected from equilibrium with aluminum trihydroxide or aluminum silicate phases. During storm events, pH and ANC declined by as much as 0.5 units and 15 μeq L^?1, respectively, at the downstream sites. The causes of the episodic acidification were increases in SO₄ ^2? and DOC.     

Dose-response relationships for the addition of limestone to lakes and ponds in the Northeastern United States

A titration based model (DeAcid) has been used to predict treatment dose and times for reacidification for CaCO₃-treated lakes in the Living Lakes, Inc. (LLI) aquatic liming program. Water quality constitutents (pH, ANC and Ca) were used to measure the effectiveness of the dosing model and reacidification rates. Data from 22 lakes or ponds in 5 northeast states have been collected since June 1986. With few exceptions, pH and ANC values ranged from 4.5 to 6.5 and ?30 to +65 ueq L^?1, respectively, in untreated sites and 6.5 to 7.8 and 120 to 300 ueq L^?1, respectively, in sites approximately 30 days after treatment. Changes in Ca concentration levels have been used to evaluate the utility of the dose model for treatment of both inland and coastal waters. For coastal, seepage lakes application of a single-box mass transfer model to observed post-liming changes in ANC and Ca adequately simulates lake response.     

Spatial Distribution of Acid-sensitive and Acid-impacted Streams in Relation to Watershed Features in the Southern Appalachian Mountains

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

On the prediction of acid precipitation events and their effects on fishes

It is possible to predict acid rain events and melts of acid snow some 12 to 24 hr in advance, including estimation of the magnitude and duration of such events. This is sufficient notice to permit monitoring of stream chemistry and fish plasma and muscle ions before acid stress, and to continue this monitoring throughout and after specific events. Such a program has been in place for 2 yr in waters tributary to the Milford Bay Trout Hatchery, Ontario. During one snow melt in February 1984 surface waters showed a decline to pH 4 and associated negative ANC. Rainbow trout held in such water lost plasma Na and Cl rapidly and died within 28 hr. The hatchery water supply, consisting of a mixture of spring and surface water, showed a decline in alkalinity from 300 to 30 μeq.L^?1, and a pH change from 6.6 to 5.4, during snow melt. Total A1 concentration increased from 42 to 222 μg.L^?1 during snow melt with the “reactive” component increasing from 17 to 112 μg.L^?1. Rainbow trout held in this water did not show physiological stress. More rapid run-off of melt water could be expected to exhaust all of the alkalinity in the hatchery water supply permitting the pH to decline and A1 concentration to rise to levels lethal to the hatchery stock of rainbow trout.     

Recent trends in the acid-base status of surface waters in Maine,USA

Data from the EPA Long Term Monitoring Program lakes at the Tunk Mountain Watershed, Maine, indicate that decreases of ≤1 Μeq L^?1 yr^?1 in SO₄, and increases of ≤2 Μeq L^?1 yr^?1 in ANC occurred in the 1980s. The sum of base cations also increased. These changes in aquatic chemistry were coincident with decreased concentrations of all solutes in precipitation during the 1980s. Other data on lakes and streams in Maine collected between the 1930s and 1990 generally confirm these trends and further indicate that larger increases in ANC may have occurred in some lowland lakes since 1940. Paleolimnologic studies indicate that decreases of 0.1 to 0.5 pH units occurred in a few small mountain lakes during the past 20 to 70 yr. However, ongoing acidification of lakes is indicated based on available data. Only lakes that were already at least marginally acidic (pH ≤5.8, ANC approximately 0) appear to have acidified.     

Acid deposition and lake chemistry in southwest China

A water quality survey has been performed on selected lakes and streams in southwest China. The purpose of the study was to measure the concentrations of acidic deposition and surface water chemistry in a region of severe air pollution, forest decline, and relatively sensitive geology to acidic deposition. We show that, although there are some high elevation lakes of low acid neutralizing capacity (ANC<150μeq L^?1, acidification of lakes has not occurred in southwest China due to production of base cations in soil and dry deposition of dust that serves to neutralize acidic deposition. Water chemistry is buffered by high base cation concentrations (Ca²⁺, Mg²⁺, Na⁺, and K⁺ greater than 300μeq L^?1, and pH values are always greater than 6.5.     

Evaluation of three experimental low-technology approaches to acid mitigation in headwater streams

Although powered dosing devices may be effective in regulating pH and acid neutralizing capacity in acid-sensitive streams, their high costs and maintenance requirements may make them unsuitable for most sites. Three alternative approaches were tried on a mountain trout stream with pH 4.5 to 5.3 and essentially no acid neutralizing capacity: (1) A barrier of wire gabions across the stream, filled with limestone chunks, raised pH about 0.5 unit for about 2 weeks. Its effect then became undetectable. Effectiveness could have been improved by using high-Ca (>95%) stone of more uniform size (5 cm in diameter), and improving the control of leaf accumulation. No biological effects of the device were detected. (2) Metal mesh baskets fed by gravity with soda ash (sodium carbonate) briquettes worked well in raising pH by as much as 1.5 units and acid neutralizing capacity by as much as 40 ueq.L^?1 for several months. However, it proved difficult to provide adequate replenishment to keep these flow-regulated devices operating during high-flow periods. (3) To reduce consumption of soda ash, we tested devices that dissolved the briquettes in an enclosed chamber and fed the concentrated sodium carbonate solution into the stream. These provided adequate neutralization when operating properly but frequently failed due to pipe clogging and to the hardening of the briquettes into a solid mass. Studies of benthic invertebrate drift and abundance associated with the soda ash treatment showed no significant effect in a few hours or in 60 days.     

WHOLE-CATCHMENT LIMING AT TJØNNSTROND,NORWAY: AN 11-YEAR RECORD

In June 1983 a whole-catchment liming experiment was conducted at Tjønnstrond, southernmost Norway, to test the utility of terrestrial liming as a technique to restore fish populations in remote lakes with short water-retention times. Tjønnstrond consists of 2 small ponds of 3.0 and 1.5 ha in area which drain a 25-ha catchment. The area is located at about 650–700 meters above sea-level in sparse and unproductive forests of spruce, pine and birch with abundant peatlands. A dose of 3 ton/ha of powdered limestone were spread by helicopter to the terrestrial area. No limestone was added to the ponds themselves. The ponds were subsequently stocked with brown and brook trout. Liming caused large and immediate changes in surface water chemistry; pH increased from 4.5 to 7.0, Ca increased from 40 to 200 μeq/L, ANC increased from –30 to +70 μeq/L, and reactive-Al decreased from about 10 to 3 μmol/L. During the subsequent 11 years the chemical composition of runoff has decreased gradually back towards the acidic pre-treatment situation. The major trends in concentrations of runoff Ca, ANC, pH, Al and NO₃ in runoff are all well simulated by the acidification model MAGIC. Neither the measured data nor the MAGIC simulations indicate significant changes in any other major ion as a result of liming. The soils at Tjønnstrond in 1992 contained significantly higher amounts of exchangeable Ca relative to those at the untreated reference catchment Storgama. In 1992 about 75% of the added Ca remains in the soil as exchangeable Ca, 15% has been lost in runoff, and 10% is unaccounted for. The whole-catchment liming experiment at Tjønnstrond clearly demonstrates that this liming technique produces a long-term stable and favourable water quality for fish. Brown trout in both ponds in 1994 have good condition factors, which indicate that the fish are not stressed by marginal water quality due to re-acidification. The water quality is still adequate after 11 years and >20 water renewals. Concentrations of H⁺ and inorganic Al have gradually increased and approach levels toxic to trout, but the toxicity of these are offset by the continued elevated Ca concentrations. Reduced sulphate deposition during the last 4 years (1990–94) has also helped to slow and even reverse the rate of reacidification. The experiment at Tjønnstrond demonstrates that for this type of upland, remote terrain typical of large areas of southern Norway, terrestrial liming offers a suitable mitigation technique for treating acidified surface waters with short retention times.     

Can forest-soil liming mitigate acidification of surface waters in Sweden?

Acidification of surface waters and forest soils is severe in large parts of southern Sweden. The shallow groundwaters are also affected. Large scale liming of surface waters and streams is in operation, often combined with wetland liming to limit the effects of acid episodes, e.g. at snow melt. Acid episodes are perhaps the most severe problem in limed surface waters and in many as yet well buffered waters, because of temperature-layered acid inflow, often superficial. As a result of some investigations, a large scale forest liming programme covering 6.500–10.000 km² was recently suggested. The main objectives of this forest liming programme are to retard cation depletion and to prevent nutrient imbalance and forest decline in acidified areas. This paper deals with the effects of forest soil liming on streams and surface waters. The response of water chemistry is very dependent on hydrological and soil properties. Although pH itself may be little affected by liming, the acidity (or negative ANC) decreases, inorganic Al-species decrease and the Al/BC-ratio increases in the runoff water. Especially interesting is that this is also true during acid episodes. This means that toxicity for acid sensitive biota decreases. These results indicate that large scale liming may have beneficial effects on surface water chemistry. Furthermore, as surface waters are expected to respond to smaller decreases in acid deposition than do forests soils, forest soil liming may allow less frequent liming of lakes. Consequently, forest soil liming in combination with the anticipated emission reductions may have very beneficial results on surface waters in certain areas of Sweden.     

Effects of liming on nutrient limitation of epilithic algae in an acid lake

The processes of lake acidification and lake restoration frequently involve major changes in DIC and DIN, both of which may potentially limit algal growth. We evaluate nutrient limitation of benthic algal biomass and species abundances during summers 1987 and 1989, before and after the liming of Lake Earnest (NE Pennsylvania) in November 1988. Limestone addition caused immediate increases in pH from 4.7 to 7.2. Alkalinity was ?34 μeq L^?1 in summer 1987, but rose to 620 μeq L^?1 in summer 1989, whereas DIN declined from 10.7 μmol L^?1 to 1.1 μmol L^?1 The algae were sampled after 45 to 46 d from clay flower pot substrates diffusing combinations of N, P and C. Algal biomass was strongly C-limited in 1987, but NP-limited in 1989. Mougeotia sp., which comprised >99% of total algal biovolume prior to liming, declined to < 1% of the community on control substrates, while Oedogonium sp. increased to 43% of total biovolume in 1989. The stimulation of chlorophyll-a accrual with C-enrichment during 1987 was consistent with the later increase in chlorophyll-a on control substrates following liming. Species enhanced by the diffused nutrients, however, generally differed from those which dominated the natural community.     

Liming effects on some chemical and biological parameters of soil (spodosols and histosols) in a hardwood forest watershed

Acidic lakes and streams can be restored with base application (usually limestone) provided that the base does not wash out before the benefits of alkalization can be realized; liming soils of the adjoining watershed may be an alternative approach. This study was conducted to provide a scientific basis for soil liming. Plots (50 m²) with different limestone dosages (e.g. 0, 5, 10 or 15 Mg CaCO₃ ha^?1) were established on each of two different soils (a Spodosol and a Histosol) in the Woods Lake watershed of the Adirondack Park Region of New York, USA. Six months after soil liming much of the added limestone was still present in both the Spodosol and in the Histosol. Ten months after soil liming results indicated that: (1) soil pH increased (>1 unit) but mostly in the top 1 cm; (2) net N mineralization increased from 9.6 to ca. 15 µg N g^?1 d^?1 and nitrification increased from 2.8 to ca. 8 µg N g^?1 d^?1; (3) denitrification was not affected (98 µg N g^?1 d^?1); (4) CO₂ production potential decreased in the surface soil and as a function of limestone dosage (60 to 6 µmol g^?1 d^?1); and (5) soluble SO ₄ ^2? concentrations in the Histosol were not affected (105 µmol L^?1). Liming acidic forest soils with >5 Mg CaCO₃ ha^?1 may increase the soil's acid neutralizing capacity, which could provide long-term benefits for surface water acidification.     

Critical Loads of Acidity to Protect and Restore Acid-Sensitive Streams in Virginia and West Virginia

The purpose of the research described here is to apply a new approach for generating aquatic critical load (CL) and exceedance calculations for an important acid-sensitive region of the eastern USA. A widespread problem in regional aquatic acidification CL modeling for US ecosystems has been the lack of site-specific weathering data needed to derive accurate model CL estimates. A modified version of the steady-state water chemistry CL model was applied here to estimate CL and exceedances for streams throughout acid-sensitive portions of Virginia and West Virginia. A novel approach for estimating weathering across the regional landscape was applied, based on weathering estimates extracted from a well-tested, process-based watershed model of drainage water acid?Cbase chemistry and features of the landscape that are available as regional spatial data coverages. This process allowed extrapolation of site-specific weathering data from 92 stream watersheds to the regional context in three ecoregions for supporting CL calculations. Calculated CL values were frequently low, especially in the Blue Ridge ecoregion where one-third of the stream length had CL?<?50?meq/m²/year to maintain stream ANC at 50???eq/L under steady-state conditions. About half or more of the stream length in the study region was in exceedance of the CL for long-term aquatic resource protection under assumed nitrogen saturation at steady state. Land managers and air quality policy makers will need this information to better understand responses to air pollution emissions reductions and to develop ecoregion-specific air pollution targets.     

Impact of Acid Mine Drainage (AMD) on Water Quality, Stream Sediments and Periphytic Diatom Communities in the Surrounding Streams of Aljustrel Mining Area (Portugal)

Aljustrel mining area is located in the Iberian Pyrite Belt, one of the greatest concentrations of massive sulphide deposits that extends from Lousal (Portugal) to Aznalcóllar (Spain). The surrounding streams, Roxo, Água Azeda and Água Forte, are influenced by the erosion of the tailing deposits and the input of acid mine drainage (AMD) from the abandoned Aljustrel pyrite mines, recently reopened in 2007. The purpose of this study was to understand how these adverse conditions influenced the stream sediments, water quality and periphytic diatom communities and establish the pre-restoration local conditions to judge the success of rehabilitation program now under way. For stream sediments, the highest metal concentration samples were found at sites F, G and H. Arsenic, Cu, Fe, Pb and Sb detected concentrations, generally exceeded the probable effect concentration values reaching level 4: the highest toxicity level. In surficial water samples of AMD affected sites (F, G and H), low pH values (1.5 to 3.5) and high metal concentrations of As (6,837 μg L^?1), Cd (455 μg L^?1), Cu (68,795 μg L^?1), Fe (1,262,000 μg L^?1), Mn (19,451 μg L^?1), Pb (136 μg L^?1), and Zn (264,377 μg L^?1) were found. In these sites, the diversity index (H′) for diatoms was low (0.6 to 2.8) and the dominant taxa were Eunotia exigua (site F, 33.5%) and Pinnularia acoricola (abundances in sites: F, 86.8%; G, 88.5%; and H, 91.1%). In opposition, in less AMD impacted, H′ was high (1.5 to 4.6) and low metal concentrations and high pH were found. Achnanthidium minutissimum was the dominant taxon in (abundances in sites: A, 76.1% and B, 24.39%). Canonical correspondence analysis showed that spatial variation due to mine influence was more important than seasonal variation, which did not show any pattern.     

The effects of stream liming on water chemistry and anadromous yellow perch spawning success in two Maryland coastal plain streams

Automated stream dosers that deliver a wet slurry of calcite were installed in 1987 on two Maryland Coastal Plain streams subject to acidic pulses during rainstorms to evaluate the use of stream liming technology to maintain suitable water quality for early life stages of anadromous fish. Results of water quality sampling during baseflow conditions and hydrologic events indicated that significant changes in water chemistry occurred at the upstream (untreated) site during elevated flows on each stream. Observed responses in stream chemistry during the events included declines in pH, acid neutralizing capacity (ANC), and Ca, and increases in monomeric Al concentrations. With the addition of calcite, stream chemistry conditions at the downstream (treated) sites during each event were similar to those observed during baseflow. In situ bioassay experiments indicated that survival of yellow perch eggs and newly-hatched larvae may be enhanced by stream liming.     

Reduced Acid Deposition Leads to a New Start for Brown Trout (<Emphasis Type="Italic">Salmo trutta</Emphasis>) in an Acidified Lake in Southern Norway

Acid deposition has led to acidification and loss of fish populations in thousands of lakes and streams in Norway. Since the peak in the late 1970s, acid deposition has been greatly reduced and acidified surface waters have shown chemical recovery. Biological recovery, in particular fish populations, however, has lagged behind. Long-term monitoring of water chemistry and fish populations in Lake Langtjern, south-eastern Norway, shows that around 2008, chemical recovery had progressed to the point at which natural reproduction of brown trout (Salmo trutta) reoccurred. The stocked brown trout reproduced in the period 2008–2014, probably for the first time since the 1960s, but reproduction and/or early life stage survival was very low. The results indicate that chemical thresholds for reproduction in this lake are approximately pH?=?5.1, Al_i?=?26 μg l^?1, ANC?=?47 μeq l^?1, and ANC_oaa?=?10 μeq l^?1 as annual mean values. These thresholds agree largely with the few other cases of documented recovery of brown trout in sites in Norway, Sweden, and the UK. Occurrence and duration of acidic episodes have decreased considerably since the 1980s but still occur and probably limit reproduction success.