Mining Lakes Research Articles

Chemical controls on iron reduction in schwertmannite-rich sediments

In sediments of acidic mining lakes, iron is generally reduced in mixtures of schwertmannite and goethite and under strongly varying pH values of < 3 to 7. We examined the effects of iron sources (schwertmannite, goethite, dissolved Fe 3+), peat humic acid, and pH (3–6) on iron reduction rates in schwertmannite dominated sediment slurries. At pH 3, addition of schwertmannite and goethite and dissolved ferric iron strongly increased, and addition of the humic acid decreased iron reduction rates. Goethite promoted iron reduction more strongly than schwertmannite. Raising pH from 3 to 4.5–6 strongly decreased iron reduction rates. When the pH was not fixed, addition of schwertmannite increased (6.3 ± 0.9 mmol g − 1 day − 1 ) and addition of goethite decreased (1.9 ± 0.7 mmol g − 1 day − 1 ) iron reduction compared to a control (3.9 ± 1.0 mmol g − 1 day − 1 ). This effect can be attributed to pH values being higher and dissolved ferric iron concentrations being lower in the goethite amended samples, compared to control and schwertmannite treatment, which was acidified by transformation of the mineral. The study suggests that the acidifying effect of schwertmannite is more critical for maintaining high rates of iron reduction than bulk mineral properties.

Structural and functional properties of low- and high-diversity planktonic food webs

To test the consequences of decreased diversity and exclusion of keystone species, we compared the planktonic food webs in two acidic (pH≤3), species-poor mining lakes with those in two species-rich, neutral lakes. The ratio of heterotrophic to autotrophic biomass (H/A) was similar in acidic and neutral lakes with comparable productivity. However, food webs in both acidic lakes were largely restricted to two trophic levels in contrast to the four levels found in neutral lakes. This restriction in food chain length was attributed to the absence of efficient secondary consumers, rather than to productivity or lake size which resulted in unusually low predator–prey weight ratios, with small top predators hardly exceeding their prey in size. In contrast to the neutral lakes, plankton biomass size spectra of acidic lakes were discontinuous due to a lack of major functional groups. The unique size-dependence of feeding modes in pelagic food webs, with bacteria in the smallest size classes followed by autotrophs, herbivores and carnivores, was maintained for bacteria but the other feeding modes strongly overlapped in size. Thus, their characteristic succession along the size gradient was roughly preserved under extreme conditions but the flow of energy along the size gradient was truncated in the acidic lakes. For most but not all attributes studied, differences were larger between acidic and neutral lakes than between neutral lakes of different trophic state.

A review of acidity generation and consumption in acidic coal mine lakes and their watersheds

Lakes developing in former coal mine pits are often characterized by high concentrations of sulfate and iron and low pH. The review focuses on the causes for and fate of acidity in these lakes and their watersheds. Acidification is primarily caused by the generation of ferrous iron bearing and mineralized groundwater, transport through the groundwater–surface water interface, and subsequent iron oxidation and precipitation. Rates of acidity generation in mine tailings and dumps, and surface water are often similar (1 to >10 mol m−2 yr−1). Weathering processes, however, often suffice to buffer groundwaters to only moderately acidic or neutral pH, depending on the suite of minerals present. In mine lakes, the acidity balance is further influenced by proton release from transformation of metastable iron hydroxysulfate minerals to goethite, and proton and ferrous iron sequestration by burial of iron sulfides and carbonates in sediments. These processes mostly cannot compensate acidity loading from the watershed, though. A master variable for almost all processes is the pH: rates of pyrite oxidation, ferrous iron oxidation, mineral dissolution, iron precipitation, iron hydroxide transformation, and iron and sulfate reduction are strongly pH dependent. While the principle mechanism of acidity generation and consumption and several controls are mostly understood, this cannot be said about the fate of acidity on larger spatial and temporal scales. Little is also known about critical loads and the internal regulation of biogeochemical iron, sulfur, and carbon cycling in acidic mine lakes.

Experimental inflow of groundwater induces a “biogeochemical regime shift” in iron‐rich and acidic sediments

In acid mine drainage (AMD) polluted lakes, sediments may show a stable iron‐ or sulphate‐reducing regime. We tested the hypothesis that increased inflow of groundwater can trigger a shift between these regimes. Schwertmannite‐bearing sediment, rich in iron (40–43%), sulphur (2.5%), and carbon (4.5%), was sampled from an acidic mine lake, and percolated (0, 5, and 20 L m−2 d−1) with two solutions (1/1 mmol L−1 versus 10/15 mmol L−1 sulphate/ferrous iron, pH 5) in sediment columns. A dissolved organic carbon (DOC) source was added after 46 days (∼2.5 mmol C L−1) to ease the carbon limitation of reductive processes. The sediment remained in an iron‐reducing and acidic regime during percolation without DOC. Percolation at a high rate and addition of DOC raised pH values in schwertmannite‐rich layers from 2.8 to 4.5–5. Schwertmannite transformation to goethite partly accelerated by a factor of &gt;2 but effectively buffered proton consumption only at the low percolation rate. Input of dissolved ferrous iron and sulphate reduced the mobilization of ferrous iron from the sediment. With pH increase, iron reduction slowed relative to CO2 production, sulphate was reduced, and iron sulphides were formed. Input of alkalinity and electron donors by percolation thus shifted the biogeochemical regime from iron to sulphate reduction. Similar regime shifts can be expected for other sediments containing immobile proton or redox buffers when exposed to the advective input of alkalinity and acidity, or electron acceptors and donors.

Temporal dynamics and growth of Actinophrys sol (Sarcodina: Heliozoa), the top predator in an extremely acidic lake

Summary1. The in situ abundance, biomass and mean cell volume of Actinophrys sol (Sarcodina: Heliozoa), the top predator in an extremely acidic German mining lake (Lake 111; pH 2.65), were determined over three consecutive years (spring to autumn, 2001–03).2. Actinophrys sol exhibited pronounced temporal and vertical patterns in abundance, biomass and mean cell volume. Increasing from very low spring densities, maxima in abundance and biomass were observed in late June/early July and September. The highest mean abundance recorded during the study was 7 × 103 Heliozoa L−1. Heliozoan abundance and biomass were higher in the epilimnion than in the hypolimnion. Actinophrys sol cells from this acidic lake were smaller than individuals of the same species found in other aquatic systems.3. We determined the growth rate of A. sol using all potential prey items available in, and isolated and cultured from, Lake 111. Prey items included: single‐celled and filamentous bacteria of unknown taxonomic affinity, the mixotrophic flagellates Chlamydomonas acidophila and Ochromonas sp., the ciliate Oxytricha sp. and the rotifers Elosa worallii and Cephalodella hoodi. Actinophrys sol fed over a wide‐size spectrum from bacteria to metazoans. Positive growth was not supported by all naturally available prey. Actinophrys sol neither increased in cell number (k) nor biomass (kb) when starved, with low concentrations of single‐celled bacteria or with the alga Ochromonas sp. Positive growth was achieved with single‐celled bacteria (k = 0.22 ± 0.02 d−1; kb = −0.06 ± 0.02 d−1) and filamentous bacteria (k = 0.52 ± &lt;0.01 d−1; kb = 0.66 d−1) at concentrations greater than observed in situ, and the alga C. acidophila (up to k = 0.43 ± 0.03 d−1; kb = 0.44 ± 0.04 d−1), the ciliate Oxytricha sp. (k = 0.34 ± 0.01 d−1) and in mixed cultures containing rotifers and C. acidophila (k = 0.23 ± 0.02–0.32 ± 0.02 d−1; maximum kb = 0.42 ± 0.05 d−1). The individual‐ and biomass‐based growth of A. sol was highest when filamentous bacteria were provided.4. Existing quantitative carbon flux models for the Lake 111 food web can be updated in light of our results. Actinophrys sol are omnivorous predators supported by a mixed diet of filamentous bacteria and C. acidophila in the epilimnion. Heliozoa are important components in the planktonic food webs of ‘extreme’ environments.

Utilisation of dissolved organic carbon from different sources by pelagic bacteria in an acidic mining lake

We compared growth rates and efficiencies of pelagic bacteria from an extremely acidic mining lake (pH 2.6, mean depth 4.6 m) supplied with different sources of carbon: (1) excreted by phytoplankton, (2) derived from benthic algae, (3) entering the lake via ground water, and (4) leached from leaf litter. Bacteria exhibited high growth rate and efficiency on exudates of pelagic and benthic algae. In contrast, they showed a lower growth rate and efficiency with organic carbon from ground water, and grew at a very high rate but a very low efficiency on leaf leachate. Results from stable isotope analyses indicate a greater importance of benthic exudates and leaf leachate for bacteria in the epilimnion, and a higher impact of ground water sources in the hypolimnion. Given the magnitude of differential source inputs into the lake, we suggest that benthic primary production was the most important carbon source for pelagic bacteria. The benthic-pelagic coupling seems to be more relevant in this shallow acidic lake with low pelagic carbon dioxide concentrations than in neutral lakes.

Abundance and primary production of filamentous green algae Zygogonium ericetorum in an extremely acid (pH 2.9) mining lake and its impact on alkalinity generation

Summary1. In extremely acid mining lakes, benthic filamentous green algae (Zygnemataceae, Chlorophyta) thrive as effective competitors for limited carbon (C). These algae could supply C for microbial‐mediated benthic alkalinity generation. However, biomass, productivity and impact of the acidobiontic filamentous green algae at pH ≤3 have not previously been determined.2. Periphytic filamentous green algae was mapped by harvesting their biomass from 85 1 × 1 m quadrats in mining lake Grünewalder Lauch. Zygogonium ericetorum colonised water depths between 1.6 and 10.5 m covering 88% of total area. Biomass peaked at 5–6 m depth. Total Zygogonium biomass amounted to 72.2 t dry weight for the whole lake (0.94 km2), which corresponds to 16.1 t C and the accumulation of primary production from 2.2 years.3. Growth of Zygogonium is moderately N, C and extremely P deficient, and seriously stressed by high rates of Fe deposition during summer. Consequently, net primary production (NPP) of Zygogonium, calculated from measured photosynthesis versus irradiance characteristics and calculated underwater irradiance (0.13 g C m−2 year−1) and in situ oxygen measurements (7.8 g C m−2 year−1), corresponds to only 0.3% and 18.1% of pelagic NPP.4. Neither pelagic nor benthic Zygogonium primary production can supply enough C for efficient acidity removal. However, at rates of benthic NPP in summer of 21.4 mg C m−2 day−1, Zygogonium contributed 26% of the C equivalents to remove acidity associated with ferric iron, contributing at least seasonally to efficient alkalinity generation.

Effects of winter temperature on phytoplankton development in acidic mining lakes

(2006). Effects of winter temperature on phytoplankton development in acidic mining lakes. SIL Proceedings, 1922-2010: Vol. 29, No. 3, pp. 1423-1426.

Hydrogeochemistry of groundwater seepage into an acidic mining lake

(2006). Hydrogeochemistry of groundwater seepage into an acidic mining lake. SIL Proceedings, 1922-2010: Vol. 29, No. 3, pp. 1452-1456.

Characterization of acidic mining lakes by titration curves

Characterization of acidic mining lakes by titration curves

Flooding Induced Effects from the Mining Lake Goitzsche on Groundwater and Land‐use in the Bitterfeld Area

AbstractThe exceptional flooding event of the river Mulde in August 2002 led to an unexpected filling of the Goitzsche, an open‐pit lignite mining lake, within two days. Due to this exceptional situation, the groundwater table in the vicinity of the lake rose several meters in the area of Bitterfeld. Over the last 100 years, this region has been affected by a large‐scale contaminated aquifer of the former chemical industry complex Bitterfeld/Wolfen. Consequent to the rising groundwater level, the regional hydraulic situation and the groundwater flow direction changed entirely, as proven by hydraulic modelling results. Due to the heterogeneous aquifer conditions, the hydraulic importance was shown of a small scale channel‐fill at the bottom of the upper aquifer. This predominant geological structure evidently affects the groundwater flow direction indicated by the modelled path lines. The resulting pathways of the contaminants can be used for the identification of exposure routes related to areas of high ecological sensitivity. The monitoring of highly soluble groundwater contaminants (e.g. benzene, TCE, cis‐1,2‐DCE), close to the flooding event, shows (irregular patterns of increasing, as well as decreasing, concentration values of related groundwater contaminants. Until the present, no consistent regional pattern can be recorded in the shift of the distribution of the concentration induced by the flooding event. Local differences in the concentration values are obviously more related to small scale variations within the Quaternary aquifer in terms of hydraulic conductivity and higher residual concentration of the contaminated matrix sediments. The temporal effects of concentration values ca be traced back, by most of the organic compounds, to distinct observation wells within the monitored time span at the starting point before flooding.

Environmental Risks Associated with Beneficial End Uses of Mine Lakes in Southwestern Australia

Lakes develop when pits from open cut mines are left to fill with groundwater. In recent years, mining companies, mining communities, and regulatory agencies have begun to consider potential beneficial end uses for mine lakes. Beneficial end uses are unlikely to be without environmental impacts, however, and a proper consideration of the total benefit to the community should consider them. This paper briefly reviews potential beneficial end uses and possible environmental impacts that might arise with them for mine lakes in the Collie Basin, a coal mining region in Western Australia. We identified eight distinct, but not necessarily incompatible, end uses from a search of the literature on mine lakes throughout the world: recreation and tourism, wildlife conservation, aquaculture, irrigation, livestock water, potable water, industrial water, and chemical extraction. Recreation, conservation, and possibly aquaculture use the mine lake directly, whereas the other end uses utilise extracted water. All end uses have the potential to have environmental effects, with the most common being an actual or perceived impact on human health and safety. A semi-quantitative risk assessment, using published literature sources, identified wildlife conservation as the end use with the least environmental risk, and irrigation as the end use with the greatest environmental risk. Such risks need to be balanced against economic and social benefits. There is an urgent need for a regulatory framework to address mine lake options.

Diversity and Community Structure of Littoral Zone Macroinvertebrates in Southern Illinois Reclaimed Surface Mine Lakes

Abstract Surface mine lakes are common in parts of the Midwest, but little is known about the communities that inhabit them or the factors shaping them. Our objectives were to: (1) characterize littoral zone macroinvertebrate communities in surface mine lakes; (2) identify factors that influence macroinvertebrate diversity and community structure; and (3) examine the utility of some commonly used bioassessment metrics to assess habitat quality based on macroinvertebrates. Fourteen lakes on a 1133 ha parcel in southern Illinois were sampled in spring 2003 using a dip net that was swept over two (small lakes) or three (large lakes) littoral zone transects. Three hundred macroinvertebrates were randomly removed from each sample and identified. Stepwise multiple regressions were used to examine relationships between several physicochemical and biological variables and macroinvertebrates. Oligochaetes were typically the most abundant taxon, followed by Hyalella, Chironomidae, Physella and Caenis. Seventy perce...

Inorganic Carbon Limitation and Mixotrophic Growth in Chlamydomonas from an Acidic Mining Lake

Plankton communities in acidic mining lakes (pH 2.5-3.3) are species-poor because they face extreme environmental conditions, e.g. 150mg l(-1) Fe2+ +Fe3+. We investigated the growth characteristics of the dominant pigmented species, the flagellate Chlamydomonas acidophila, in semi-continuous culture experiments under in situ conditions. The following hypotheses were tested: (1) Low inorganic carbon (IC) concentrations in the epilimnion (e.g. 0.3 mg l(-1)) arising from the low pH limit phototrophic growth (H-1); (2) the additional use of dissolved organic carbon (mixotrophy) leads to higher growth rates under IC-limitation (H-2), and (3) phagotrophy is not relevant (H-3). H-1 was supported as the culture experiments, in situ PAR and IC concentrations indicated that IC potentially limited phototrophic growth in the mixed surface layers. H-2 was also supported: mixotrophic growth always exceeded pure phototrophic growth even when photosynthesis was saturated. Dark growth in filtered lake water illuminated prior to inoculation provided evidence that Chlamydomonas was able to use the natural DOC. The alga did not grow on bacteria, thus confirming H-3. Chlamydomonas exhibited a remarkable resistance to starvation in the dark. The compensation light intensity (ca. 20 micromol photons m(-2) s(-1)) and the maximum phototrophic growth (1.50 d(-1)) fell within the range of algae from non-acidic waters. Overall, Chlamydomonas, a typical r-strategist in circum-neutral systems, showed characteristics of a K-strategist in the stable, acidic lake environment in achieving moderate growth rates and minimizing metabolic losses.

High Heterotrophic Bacterial Production in Acidic, Iron-Rich Mining Lakes

The acidic mining lakes of Eastern Germany are characterized by their extremely low pH and high iron concentrations. Low concentrations of CO2 in the epilimnion due to the low pH and reduced light transmission due to dissolved ferric iron potentially limit phytoplankton primary production (PP), whereas dissolved organic carbon (DOC) may promote heterotrophic production of bacteria (HP). We, therefore, tested whether HP exceeds PP in three lakes differing in pH and iron concentration (mean pH 2.3-3.0, 23-500 mg Fe L(-1)). Bacterial biomass and HP achieved highest values in the most acidic, most iron-rich lake, whereas PP was highest in the least acidic lake. HP was often higher than PP (ratio HP/PP up to 11), indicating that planktonic PP was not the main carbon source for the bacteria. HP was not related to PP and DOC, but HP as well as bacterial biomass increased with decreasing pH. Light stimulated the formation of ferrous iron, changed the DOC composition, and increased the HP in laboratory experiments, suggesting that iron photoreduction caused DOC degradation. This may explain why we found the highest HP in the most acidic and most rich lake. Overall, the importance of bacteria in the cycling of matter and as a basis for the whole food web seemed to increase in more acidic lakes with higher iron concentrations.

Overland flow, erosion, and related phosphorus and iron fluxes at plot scale: a case study from a non-vegetated lignite mining dump in Lusatia

Long-term high resolution measurements of precipitation, soil water budget, surface runoff, and sediment transport as well as rainfall simulations at plot scale have been accomplished on a non-vegetated lignite mining dump (Germany, Lusatia, Schlabendorf-North), completed by measurements of infiltration and water drop penetration time. The investigations revealed that the distribution of hydraulic properties is mainly related to ridges, rills, and gullies, structuring the dumps. Soil moisture time series on a ridge showed nearly no response to rainfall events. Infiltration measurements and rainfall simulations indicate, that the ridges bare of vegetation predominantly have a very low infiltration capacity, which is caused by water repellency. Even low rainfall intensities generate surface runoff. In contrast, gullies show no hydrophobic properties but high infiltration capacities, although the tipped sediment is identical in texture. Surface runoff and erosion may only be explained by the spatial pattern of ridges, gullies, and rills. The current P loss from those non-vegetated sites is very low due to low P contents in eroded matter. Since the very low P fluxes and the very low portions of water-extractable P are accompanied by higher Fe portions, which result in Fe/P ratios of up to 130, the P losses are not relevant for a eutrophication of the adjacent acid mining lakes. Hence, this study aims to the estimation of the runoff and erosion processes and the related P and Fe fluxes at plot scale, as a contribution to the development of the post mining landscape at the interface of soil and surface water.

System dynamics approach to assess the sustainability of reclamation of disturbed watersheds

The mining of oil sands in northern Alberta leaves behind large open pits, tailings, and overburden piles in which the surface and subsurface hydrology has been completely disrupted. Extensive reclamation work is required to reconstruct the entire landscape and reestablish the various elements of the hydrologic cycle. Syncrude Canada Ltd. has established a series of small instrumented watersheds in a reclaimed overburden pile at the Mildred Lake mine in northern Alberta, Canada, to test the sustainability of different reclamation strategies. The purpose of these field sites is to assess the performance of different reclamation strategies and track the evolution of the reclaimed landscape with time. The saline–sodic shale overburden has been covered with different (in type and depth) soil layers to provide sufficient moisture storage for vegetation while minimizing runoff and salt transport into the cover from the underlying overburden shale. In this paper, a system dynamics watershed model (SDWM) is developed to simulate one of the reconstructed watersheds and assess its ability to provide common watershed functions. The model is at an early stage, but preliminary results point to the potential of the system dynamics approach in simulating watersheds and testing different scenarios. The tested reclamation strategy seems to be satisfactory within a certain range of hydrologic conditions. Further validation of the SDWM is required, however, before relying on its results for decision support with regard to reclamation strategies.Key words: sustainability, watershed simulation, system dynamics, reclamation, STELLA.

Detection of enteric viruses and bacterial indicators in German environmental waters

A German mining lake and the supplying surface waters, which are located downstream of a sewage plant, were examined regarding their microbiological and virological quality. Between October 2002 and September 2003, specific PCR methods were used to determine the occurrence of enteric viruses in 123 water specimens drawn at different sites downstream of the waste water treatment plant and in 9 samples from the sewage plant influent. Detection rates in sewage plant effluents and surface water samples depended on sampling sites and were: 29-76% for enterovirus (EntV), 24-42% (astrovirus, AstV), 15-53% (norovirus, NV), 3-24% (rotavirus, RoV), 5-20% (hepatitis A virus, HAV) and 20% (adenovirus, AdV). AstV genome load of selected samples was between 3.7 x 10(3) to 1.2 x 10(8) genome equivalents per liter (gen.equ./l), depending on sampling location; NV average genome load ranged from 1.8 x 10(4) to 9.7 x 10(5) gen.equ./l. Cell culture methods showed that three out of 18 PCR positive samples contained infectious EntV. Even though microbiological parameters such as Escherichia coli, enterococci and coliphages indicated acceptable microbiological water quality, the virological data of this study suggest the possibility that surface waters may be a source for enteric viral infections.

Mining lakes in a disturbed landscape: Application of the EC Water Framework Directive and future management strategies

Some of the several hundred Lusatian mining lakes originating from lignite mining will be among the largest and deepest lakes in Germany. A special problem of many of these lakes is severe acidification. According to the EC Water Framework Directive (WFD), artificial lakes larger than 0.5 km 2 have to be monitored and managed in order to establish or maintain a state of so-called good ecological water quality. Therefore the WFD demands the definition of type-specific reference conditions as those of the closest comparable surface water body type in nature, such as natural acidic volcanic crater lakes or oligo- to mesotrophic neutral hard water lakes. We propose a classification scheme for mining lakes applying acidity and planktonic colonization as criteria. Five types of lakes are distinguished ranging from extremely acidic to neutral hard water lakes. Phytoplankton and especially metazoan zooplankton are introduced as intriguing and simple indicators for different states of ecological quality in highly acidic mining lakes. We recommend that extremely and very acidic lakes should remain in the acidic state to protect these as valuable ecosystems, whereas moderately and weakly acidic lakes can be managed by external flooding, chemical or ecotechnological measures to achieve neutral water quality conditions necessary for recreation or fishery use.

Phosphorus mobility in sediments of acid mining lakes, Lusatia, Germany

Changes in benthic retention and mobility of P were studied in a chronosequential approach in acid (pH 2.5–3.5) to moderately acid (pH 5.6–6.8) mining lakes (MLs) with respect to the threat of eutrophication during maturation. Although various MLs exhibit a high pelagic P availability there is currently no distinct threat of an enhanced eutrophication due to a C limitation and a high benthic P immobilization potential. The sequential P extraction applied revealed an increase in sedimentary total P with increasing pH due to the additional uptake of P by Al- and Fe-hydroxides, but no increase in mobile P forms. Currently, the excess in reactive Fe at a high Fe:P ratio in surface sediment at pH ∼3 favours an efficient P precipitation of Fe-oxi-hydroxides with a high specific surface area for P adsorption. However, an enhanced future P mobility of ML sediments and a threat of eutrophication results from: (1) a distinct reduction of the import of Fe and Al from the catchment over time, resulting in a lower supply towards the sediments, and (2) a reduction in the sedimentary Fe mineral surface area due to the future rise in pH.