The Swedish liming programme

To mitigate the acidification problem in surface waters the Swedish government is funding a liming programme. Limestone or dolomite powder has been applied to acidified waters since 1976 and on a large scale since 1982. In most projects, limestone is applied directly to the lake, but in several cases supplementary liming is carried out on wetlands and in streams using dosers or other techniques. At present 7,500 Swedish lakes and more than 11,000 kilometers of streams are limed repeatedly with a total of some 200,000 tonne of limestone every year. In 1994 about US$ 25 million was invested by the Swedish government in the liming programme. The biological objective of the liming operations is to detoxify the water so that the natural fauna and flora can survive or recolonize. The chemical aim is to raise the pH above 6.0 and the alkalinity above 0.1 meq/l, which gives an acceptable buffering capacity. In addition, dissolved metals will be deposited after liming, thus reducing their toxicity. Overdosing must be avoided, with natural softwater characteristics being the objective. The chemical and biological effects in water of the liming operations are encouraging. The Swedish liming programme has so far resulted in restoration in 80–90% of the limed surface waters. The fauna often shows an initial dominance by a few species but diversity increases with time, In general, flora and fauna in limed waters show a great resemblance to those in waters not acidified. An undesired effect of liming is significant changes in mosses and lichens after wetland liming.     

Integrated studies of the effects of liming acidified waters (ISELAW-programme)

To assess the long-term (>15 years) effects of liming, an integrated programme for studies of the effects of liming in acidified waters (ISELAW) was initiated in 1989. At present, 14 lakes and 14 streams are included in the programme. Although on average of 14 years have passed since the first lime treatment, and the chemical goal of liming have been achieved in all lakes, i.e. to raise pH over 6.0 and alkalinity over 0.1 meq 1–1, changes in biota could still be observed in several of the lakes. Species richness and species diversity was in general not different in the limed lakes as compared to circumneutral reference lakes, although the composition of the fauna did not resembled that of neutral lakes. Among zooplankton, rotifers were still more abundant than expected in limed lakes. The fish communities appeared unstable and the species proportions as well as population structures are changing, partly as a result of re-colonisation of acid-sensitive species after liming. The results indicate that the long-term changes may persist for more than 15 years after liming and emphasise the importance of comparable time series in non-limed lakes.     

Acidification and Liming of River Vikedal, Western Norway. A 20 Year Study of Responses in the Benthic Invertebrate Fauna

This paper deals with benthic invertebrate population responses to acidification and liming in the lower part of River Vikedal. In 1979 the river showed signs of increasing acidification. Highly sensitive invertebrates like the mayfly Baetis rhodani were present in the river in low abundance, but disappeared in the subsequent years. In order to re-establish a non-toxic water quality for fish, liming of the spring snowmelt to a minimum of pH 5.7 was started in 1987. During the later years liming has been successively increased. The invertebrate fauna showed a slow, but positive, response during the first years after liming, especially during autumn. B. rhodani recolonized the river in low density, but the spring cohort was still weak. Since 1994 the lime dosage was increased to secure a minimum pH of 6.3 during spring snowmelt. This has resulted in an overall increased biodiversity in the limed section of the river. Several acid-sensitive species, like both cohorts of B. rhodani and freshwater snails have colonized this part of the river. Simultaneously biodiversity in the unlimed reference sites has slightly improved during the last years. This is correlated with decreased sulphur deposition and improved surface water chemical conditions.     

Freshwater liming

Operational liming of surface waters is part of Sweden and Norway's strategy to counteract freshwater acidification caused by air pollutants. Smaller scale liming efforts are performed as research or experimental programs in other countries. Yearly, approx. 300,000 tons of fine-grained limestone (CaCO₃) is spread in lakes and streams and on wetlands to raise the pH in surface water at a cost of approximately 40–50 million $US. The chemical target is set by the biological goals and objectives. A total of over 11,000 lakes and streams are treated on a continuing basis. Dose calculations consider pH, inorganic monomeric Al, dissolved organic matter and the necessary buffering. Lake liming, limedosers at streams and terrestrial liming are used. A mix of different liming techniques is often preferred to get an optimal result. The vast majority of changes are desirable and expected Undesirable effects may appear and damaged wetlands are probably the most serious ones. Cost-benefit analysis show that liming may be profitable for the society. Recovery of the systems can take up to 10–20 years. Liming will in the long run restore the ecosystems but will not make them identical to what may be the original ones. In some cases, complementary measures, e.g. facilitation of recolonization, are necessary to enhance recovery. Reduced emissions of acidifying pollutants according to signed protocols will decrease the need for liming, but still liming is needed for several decades in large regions to preserve biodiversity.     

Effects of liming on crayfish and fish in Sweden

The effects of lime treatment on crayfish (Astacus astacus and Pacifastacus leniusculus) populations in 17 lakes and fish populations in 47 lakes and 7 rivers within the trial period 1976–82 have been evaluated. An increase in the catch of crayfish per unit effort was observed in 7 lakes, although significantly in one lake only. The varying results in the other lakes indicate that factors other than pH may be of greater importance for the development of crayfish populations after liming. Recruitment of fish improved in waters where liming resulted in pH >5.5. In lakes with pH <5.5 before and pH >5.5 after treatment, there was a significant increase in the number of fish caught, from 12 to 34 per unit effort. Due to improved recruitment the individual average weight was smaller and hence the catch in weight per unit effort was about the same as before liming. After lime treatment in streams which resulted in a stable pH of >5.5, the abundance of juvenile salmonids increased to numbers found in non-acidified streams. In other streams acid spates reduced the positive influence of liming on the abundance of juvenile salmonids.     

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.     

The effects of liming on juvenile stocks of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) in a Norwegian river

The effects of liming on juvenile stocks of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) in the river Vikedalselva in southwestern Norway were assessed. From 1987 to 1989, the river was limed only during the spring snow melt, and pH varied in the range between 5.5 and 7.0. In 1990 to 1993, the river was limed to pH 6.2 from 15 February to 1 June and to pH 5.7 during the rest of the year. Since 1994, the pH during late winter and spring was maintained above 6.5. Prior to liming fish kills were evident during spring snow melt, but these have not occurred since liming. Electrofishing in the autumn between 1981 and 1994 showed no significant change in densities of juvenile salmon and brown trout after liming, mean densities ranged between 19–50 and 9–32 individuals 100 m^–2 respectively. A significant linear correlation between production and biomass of both species was found, indicating that factors directly controlling density affect juvenile production and cause production to remain below carrying capacity. In spite of a clear increase in pH and a reduction in the concentration of labile aluminium after liming, the conditions still do not seem to be optimal for juvenile salmonids. We suggest that a complexity of different factors impose limitations on fish production in the river: inadequate egg deposition, environmental factors such as water temperature and flow, osmoregulatory failure in mixing zones between limed and acidic water and gill damage through deposition of aluminium and iron. However, there are several indications of a reduction in toxic effects after the pH was raised to 6.5 during spring snow melt.     

Liming the acid lake Hovvatn,Norway: A whole-ecosystem study

Hovvatn, a 1-km² chronically-acidified lake in southernmost Norway, was treated with 200 tonne of powdered limestone in March 1981. An additional 40 tonne were added to a 0.046 km² pond (Pollen) draining into Hovvatn. The lakes were stocked with brown trout in June 1981 and in each subsequent year. At ice-out pH rose from 4.4 to 6.3 (Hovvatn) and 7.5 (Pollen), Ca and alkalinity increased, and total Al decreased by 120 μg L^?1. None of the other major ions exhibited significant changes in concentration. Total organic Cand Pincreased after liming. The phytoplankton community was dominated by chrysophytes and did not change significantly following liming. The zooplankton community was typical of acid lakes prior to liming. There was a clear succession in species dominance following treatment, although no new species immigrated to the lakes. Zoobenthos changed from a community characterized by low abundance and reduced number of species to increased abundances of oligochaetes, mayflies and chironomids. Hovvatn and Pollen were barren of fish prior to stocking. The stocked fish showed remarkably high growth rate during the first years. Liming apparently improved conditions for zoobenthos, enhancing the processing of fine detritus which in turn resulted in elevated levels of TOC and P in the lakewaters during the first year after liming. The “oligotrophication” process typical of acid lakes was temporarily reversed by liming. The interactions between groups of organisms in Hovvatn and Pollen indicates that many years are required before a new steady-state can be attained following liming.     

Liming restores the benthic invertebrate community to “pristine” state

After liming of twelve acidified rivulets in central Sweden, the fauna increased its mean similarity to the fauna in unlimed non-acidified references. All species which were found after liming were also found in other waters north and south of the limed area. The species composition after liming should thus be considered as typical of the limed geographical area. Before liming, the fauna was characterized by the acid tolerant mayfly Leptophlebia spp. After liming the fauna was characterized by the acid sensitive mayfly genus Baetis, an important food organism for young brown trout. The restoration of the water quality by liming resulted in an apparently “pristine” benthic invertebrate community, enhancing the conditions for salmonid fish.     

Low cost limestone treatment of acid sensitive trout streams in the appalachian mountains of Virginia

The method of single point, single application liming has been studied as a means of mitigating anthropogenic acid in trout streams in Virginia. Three critically acid sensitive streams were dosed with a total of five applications of limestone sand and monitored before, during and after the treatments to assess changes in water chemistry and biota. Limestone treatments of 8 to 50 tons (particle sizes 150–1000 μm), with the amounts based on sulfate deposition loading and existent stream water chemistry, were used to restore ‘lost’ acid neutralizing capacity (ANC). Contact time between the limestone bed in the stream bottom and the water was the limiting factor affecting the degree of treatment with bed length primarily controlled by the gradient of the stream at the dosing site. A single site application was able to restore approximately 2/3 of the ANC. Exponential fits of limestone consumption data were used to predict that treaments of similar streams would last from two five years before reliming was necessary. Both total and monomeric aluminum levels were reduced up to 50%, and aquatic biota increased below the treatment sites. Post-liming average values for the three streams were pH 6.66, 82.7 μeq L^?1 ANC and 2.63 mg L^?1 Ca. The average ANC improvement suggests that some 88% of the native trout streams in Virginia, which average 29 μeq L^?1 ANC reduction from acid deposition, could be temporarily restored using single application liming.     

Responses of phyto- and zooplankton to liming in a small acidified humic lake

Liming resulted in an immediate and transitory decrease of plankton biomass and phytoplankton primary production in the limed part of an acidified humic lake. In the longer term liming has changed species composition and dominance of phyto- and zooplankton. Due to increased transparency and improved oxygen conditions plankton biomass peaked deeper in the water column after liming. During the three years post-liming period phyto- and zooplankton communities have changed less than reported in several other studies. This is largely because liming was carried out well before the collapse of perch population, which has controlled zooplankton both in the pre- and post-treatment period.     

Reappearance of Highly Acid-Sensitive Invertebrates After Liming of an Alpine Lake Ecosystem

The amphipod Gammarus lacustris was earlier a main food item of brown trout in Lake Svartavatnet at the Hardangervidda mountain plateau in South Norway. In the middle of the 1980's, G. lacustris disappeared from the trout diet due to increased acidification. In order to preserve a unique genetic variant of brown trout living in the area, a liming programme was initiated in 1994. During the first years after liming, G. lacustris was absent both in fish stomachs and in lake littoral samples. In 1999, it reappeared in brown trout stomach samples together with two other strongly sensitive species, the tadpole shrimp Lepidurus arcticus and the freshwater gastropod Lymnaea peregra. Data from monitoring indicate that the water chemical conditions of L. Svartavatnet are still close to the critical limits of these animals. They have probably survived in small refuges of acceptable water quality, either in areas of inflowing groundwater or in the littoral, below the more acidic surface layer. The fact that these sensitive animals have not yet been found in benthic samples emphasise fish diet as an important tool in early registration of the presence/absence of invertebrates with low abundance or patchy distribution.     

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.     

Side Effects of Liming - A Study of Four Dimictic Lakes in Southern Norway

Side effects related to liming have been studied in four dimictic lakes (553–642 m?a.s.l.; 59°57′N) in Finnemarka, a forested area in Southern Norway with poor catchment buffer capacity. Data series from lake profiles have been sampled two decades apart; 10 years prior to liming and after 10 years of liming. Water samples were collected during spring after ice breakup and during summer after the development of thermal stratification. Before liming, there were very low concentrations of bicarbonate (HCO ₃ ^– ; or alkalinity) in the lakes. After 10 years of liming, up to 90% of the ions in hypolimnion originate from lime products. Hence, liming strengthened the chemical stratification and increased the vertical stability. Differences in chemocline developments between lakes were explained by differences in physical properties, i.e. their depth/surface area ratio. The chemocline developments lead to increased concentrations of organic matter in the hypolimnion with a subsequent reduction in oxygen concentrations. Lime additions during late spring, as an alternative to early autumn, lead to pronounced anoxic conditions in the hypolimnion.     

The loch fleet and other catchment liming programs

The circumstances under which catchment liming is an advisable economic alternative to direct water liming are described, as are research and operational experiences of catchment liming, drawing mainly on the Loch Fleet Project results and other European data. The arguments for and against catchment liming as a means of restoring acidified aquatic habitat are presented. In general, it is concluded that there are conditions, such as lakes with short retention times and/or where stream spawning fish species are involved, where catchment liming is a sensible option.     

Effects of lime applications to parts of an upland catchment on soil properties and the chemistry of drainage waters

The liming of soils in the lower part of an upland catchment was found to have a major effect on both soil properties and the chemistry of drainage waters. Exchangeable Al was closely correlated with soil pH and showed a very steep rise from 2.6-4.8 meq 1⁻¹ over the pH range 5.5-4.5. As streams flowed from unimproved through improved land there was an increase in pH and the concentration of all major anions and basic cations. The greatest increase was in Ca (approximately 3.5-fold). The concentrations of all dissolved Al species decreased, with inorganic monomeric Al falling to near zero. Leachates were examined from soils representative of the most acidic and the least acidic. Calcium concentrations differed by almost tenfold. Aluminium was present in leachates from the limed soil, but most was unreactive and none was inorganic monomeric. Most of the Al leached from the acid soil was monomeric.
A model of soil acidification is proposed in which soil Ca is depleted at a rate of 8% of the exchangeable Ca per annum. The model predicts that liming a soil to neutrality would be likely to influence drainage water chemistry for 30-40 years and that the most acidic soils of the catchment show no net loss of Ca to drainage.     

Microfungi in coniferous forest soils treated with lime or wood ash

Summary Microfungal species composition was studied in coniferous forest soils which had been treated with lime or wood ash. The pH increased by about 2.5 units at the highest rate of application. Fungi were isolated 4–5 years after the treatments using a soil washing technique. At one site, Öringe, clear differences in species composition due to liming were found. Penicillium spinulosum, Oidiodendron cf. truncatum, Mortierella spp., and two sterile taxa decreased in abundance in limed areas, while Geomyces pannorum, Penicillium cf. brevicompactum, Trichoderma polysporum, and Trichosporiella sporotrichioides increased in isolation frequency. At another site, Torrmyra, the effect of liming was less pronounced, although the pH changes due to the treatments were larger compared to the Öringe site. However, T. polysporum increased, while a sterile taxon decreased in abundance in lime- and wood ash-treated plots. The changes in microfungal species composition after liming were similar to those found earlier in urea-treated soils, and opposite to those found in artifically acidified or ammonium nitrate-fertilized soils.     

Liming of acidified lakes: Induced long-term changes

This study presents data concerning long-term trends after neutralization of four acidified lakes in two regions on the Swedish west coast. Neutralization was achieved by a di-Ca-silicate with 52% CaO and about 11.5% MgO. Between 61 and 74% of the spread lime product dissolved during a 5 to 7 yr period. The liming increased pH, from a range of 4.5 to 5.2 to near neutral and restored alkalinity in the range of 0.2 to 0.3 meq l^?1 and the Ca-content became 3 to 4 times higher than before liming. In two lakes transparency decreased significantly presumably due to changed phytoplankton composition. These changes successively declined due to dilution and continuous acid loading. The changes in water chemistry and development of stocked brown trout (Salmo trutta) populations initiated biotic changes. Phyto- and zooplankton communities reacted both instantly and later with successions in species composition. Changes of benthic macroinvertebrate species occured over several years, but some pelagic species, e.g. corixids were rapidly reduced due to predation of fish. Observed changes were predominantly due to expanding populations of species present at very low abundances even during acid state of the lakes. Some organisms found during preacid state of the lakes did not establish new populations and this process may need a prolonged time with favorable conditions. Reacidification towards the end of the study period significantly stressed the brown trout population and also favored expansion of the filamentous algaMougeotia sp. andSphagnum sp. that almost vanished during the first year after liming. Decreasing concentration of total P was not influenced by neutralization and may be mostly dependent on negative changes in the soils surrounding the lakes. If generally valid, this process may be an important factor for the oligotrophication of lakes in areas where acid deposition is high.     

Liming effects on soil pH and crop yield depend on lime material type,application method and rate,and crop species: a global meta-analysis

Purpose

The aim of this meta-analysis was to investigate the interactive effects of environmental and managerial factors on soil pH and crop yield related to liming across different cropping systems on a global scale.

Materials and methods

This study examined the effects of liming rate, lime application method, and liming material type on various soil chemical properties and crop yield based on data collected from 175 published studies worldwide since 1980.

Results and discussion

The most important variables that drive changes in soil pH and crop yield were liming rate and crop species, respectively. Soil conditions, such as initial soil organic matter and soil pH, were more important for increasing soil pH in field-based experiments, while lime material type and application method were more important for improving crop yield. To effectively neutralize soil acidity, the optimum liming duration, rate, and material type were?<?3 years, 3–6 Mg ha^?1, and Ca (OH)₂, respectively. Averaged across different crop species, the application of CaO, CaCO₃, Ca (OH)₂, and CaMg (CO₃)₂ increased yield by 13.2, 34.3, 29.2, and 66.5%, respectively.

Conclusions

This meta-analysis will help design liming management strategies to ameliorate soil acidity and thus improve crop yield in agroecosystems.

     

A Strategic Appraisal of Options to Ameliorate Regional Acidification

Studies in the 1980's showed that there had been extensive loss of fish and invertebrates in lakes and streams in upland Wales due to acid deposition. A regional survey of these waters in 1995 showed that, despite large reductions in sulphur emissions, acidification was still widespread and no biological improvement was detectable. Policy options are needed which should include reductions in nitrogen as well as sulphur, the contribution of land use (especially conifer afforestation), liming and the introduction of species. This paper describes a screening study comprising the construction of an evaluation matrix, the use of decision workshops of expert stakeholders and trade-off analysis to identify possible combinations of options. The resulting output is being used to construct a regional strategy for achieving measurable ecosystem recovery within the next 10 years.