Alteration to lake trophic status as a means to control arsenic mobility in a mine-impacted lake (original) (raw)
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A greenhouse microcosm study investigated the impacts of recovered iron oxyhydroxide mine drainage residuals (MDRs) on phosphorus (P) and trace metal distributions at the sediment layer/water column interface in Grand Lake o’ the Cherokees, a large reservoir receiving waters impacted by both historic mining and current agricultural land uses. Each mesocosm included 5 kg of lake sediment and 20 L of on-site groundwater. Three treatments were examined in triplicate: control (C) with no additions, low MDR (LM) with 0.3 kg added MDR, and high MDR (HM) with 0.9 kg added MDR. In the first 10 days, aqueous soluble reactive phosphorous (SRP) concentrations decreased likely due to colonizing biomass uptake with no significant differences among the three treatments. LM and HM treatments showed delayed peaks in dissolved oxygen (DO) and lesser peaks in chlorophyll-a (Chl-a) concentrations compared to the C treatment, indicating MDR addition may suppress biomass growth. During days 11 to 138, t...
Redox processes in a eutrophic coal-mine lake
Mineralogical Magazine, 2005
The water column chemistry of lake St Eloy (St Eloy-les Mines, Allier, France) was monitored over a period of a year. This is a small stratified lake created by subsidence of an underground coal mine. The results show a permanent stratification and the development of two water bodies with contrasting chemistry. The superficial oxic layer (i.e. the upper 5 m) is of high water quality and the water, not affected by seasonal changes, is suitable as a source of drinking water. In contrast, the deeper layer is permanently anoxic and the waters have a conductivity which is six times greater than in the epilimnion. Due to density difference and the small size of the lake, no turn-over occurs and all elements that diffuse from bottom sediments are strongly concentrated in the hypolimnion. Arsenic concentrations are very low in the epilimnion, but they increase quickly with depth below the oxycline, to reach up to 7 μm below 8 m depth. Different solid phases could control the fate of arsenic...
Role of sediment porewater in the cycling of arsenic in a mine-polluted lake
Environment International, 1994
The surficial sediments of Moira Lake averaged 545 lag.g 1 of arsenic, with maximum values close to l mg.g -~ at depths of 23-27 cm below the sediment water interface. The sediment porewater is the linking agent between the sediment solid phase and the overlying lake water. The depth distributions of total As in interstitial waters at all stations are characterized by subsurface maxima, with concentrations four to six times greater than in the lake waters. In all the porewater profiles examined, inorganic As [As(III)+As(V)] comprised most of the As. The As(Ill) (arsenite) percentage ranged from 66-83%. Methylated-As compounds represented <2% of the total As. The strong correlation of As with Fe and Mn together suggests that both Fe and Mn are involved in the As mobility. The elevated As concentrations in bottom sediments represent a continuous internal mining of As towards the interface all year around, The concentration gradient of total dissolved As indicates that an upward diffusion of As towards the water column with the estimated annual fluxes being 0.8-3.8 p.g.cm'2.y "t.
Appl Geochem, 2010
Lacustrine sediments, submerged tailings, and their pore waters have been collected at several sites in Yellowknife Bay, Great Slave Lake, Canada, in order to investigate the biogeochemical controls on the remobilization of As from mining-impacted materials under different depositional conditions. Radiometric dating confirms that a mid-core enrichment of Pb, Zn, Cu and Sb corresponds to the opening of a large Au mine 60 a ago. This was evident even in a relatively remote site. Arsenic was enriched at mid-core, coincident with mining activity, but clearly exhibited post-depositional mobility, migrating upwards towards the sediment water interface (SWI) as well as down-core. Deep-water (15 m) Yellowknife Bay sediments that contain buried mine waste are suboxic, relatively organic-rich and abundant in microbes with As in pore waters and sediments reaching 585 μg/L and 1310 mg/kg, respectively. Late summer pore waters show equal proportions of As(III) and As(V) (16–415 μg/L) whereas late winter pore waters are dominated by As(III) (284–947 μg/L). This can be explained by As(III) desorption mechanisms associated with the conversion of FeS to FeS2 and the reduction of As(V) to As(III) through the oxidation of dissolved sulfide, both microbially-mediated processes. Processes affecting As cycling involve the attenuating efficiency of the oxic zone at the SWI, sediment redox heterogeneity and the reductive dissolution of Fe(hydr)oxides by labile organic matter, temporarily and spatially variable.
Arsenic forms in mine-polluted sediments of Moira Lake, Ontario
Environment International, 1993
The sediments of Moira Lake, Ontario, have accumulated large quantities of arsenic and toxic metals since the 1830's when mining began in its drainage basin. Despite the fact that the mine activities ceased in 1961, leachates from the abandoned mine wastes still deliver large quantities (about 3.5 Mg.y "t) of arsenic to the lake. The As concentrations at the top of the sediments average about 545 p.g.g-t with maximal concentrations of about 1000 Ixg.g -1 occurring at depths of 23-27 era. Approximately 56% of the As in the sediments is bound to the iron and manganese oxides. Observed changes in the profiles of As bound to the different chemical fractions suggest that some of the oxide-bound As is being converted to the residual phases. In view of the dominant form of As in the sediments, changes in the Eh or pH may trigger the release of large quantities of As to the overlying water.
The Potential of Organic Matter Additions for Neutralizing Surface Mine Lakes
Transactions of the Illinois State Academy of Science. Illinois State Academy of Science
The potential of anaerobic bacterial metabolism to raise the pH of acid lakes was tested by adding 9.1 metric tons of fresh cow manure to a 2.1 ha, 6 m deep, pH 2.9 coal mine lake near DeSoto, Illinois. This additive was expected to provide a substrate for sulfate-and iron-reducing bacteria that generate alkalinity. Lake water chemistry was monitored for 2.5 years in the treated lake and in a nearby untreated lake. The main effects of this cow manure addition were a rise in pH, iron, and sulfide and a decrease in oxygen, acidity, and aluminum in deep water of the treated lake during summer stratification. Surface water chemistry remained unchanged except for a decline in oxygen con-centrations. During fall turnover, the chemistry of the entire lake returned to its pre-treatment condition. The results of this investigation indicate that anaerobic bacterial decay of organic matter can raise the pH of acid mine water. In our experiment low hydraulic retention time probably prevented a ...
Biogeosciences Discussions, 2010
In the last decades, the mining exploitation of large areas in Lusatia (South-eastern Germany) but also in other mining areas worldwide has led to the formation of hundreds of pit lakes. Pyrite oxidation in the surrounding dumps makes many such lakes extremely acidic (pH < 3). The biogeochemical functioning of these lakes is mainly governed by cycling of iron. This represents a relevant ecological problem and intensive research has been conducted to understand the involved biogeochemical processes and develop bioremediation strategies. Despite some studies reporting the presence of living organisms (mostly bacteria, algae, and macro-invertebrates) under such acidic conditions, and their trophic interactions, their potential impact on the ecosystem functioning was poorly investigated. The present study aimed to assess the influence of chironomid larvae on oxygen dynamics and iron cycle in the sediment of acidic pit lakes. In the Mining Lake 111, used as a study case since 1996, Chironomus crassimanus (Insecta, Diptera) is the dominant benthic macro-invertebrate species and occurs at relatively high abundances in shallow water. A 16-day laboratory experiment using microcosms combined with high resolution measurements (DET gel probes and O2 microsensors) was carried out. The burrowing activity of C. crassimanus larvae induced a 3-fold increase of the oxygen consumption by sediment, and stimulated the mineralization of organic matter in the upper layers of the sediment. The iron cycle was also impacted (e.g. lower rates of reduction and oxidation, increase of iron-oxidizing bacteria abundance, stimulation of mineral formation) but with no significant effect on the iron flux at the sediment-water interface, and thus on the water acidity budget. This work provides the first assessment of bioturbation in an acidic mining lake and shows that its influence on biogeochemistry cannot be neglected.
Journal of Environment Quality, 2008
Ocoee Lake No. 3 is the fi rst reservoir receiving suspended sediments contaminated with trace metals discharged by acid mine effl uents from the Ducktown Mining District, Tennessee. Bottom sediments (0-5 cm) from the lake were sampled to assess the potential for future adverse environmental eff ects if no remediation controls or activities are implemented. Th e sediments were found to include a major component (173 ± 19 g kg −1) that dissolved in 6 mol L −1 HCl within 24 h. Th is acid-soluble and relatively labile fraction contained high concentrations of Fe (460 ± 40 g kg −1), Al (99 ± 11 g kg −1), Mn (10 ± 8 g kg −1), Cu (2000 ± 700 mg kg −1), Zn (1300 ± 200 mg kg −1), and Pb (300 ± 200 mg kg −1). When the pH of water in contact with the sediment was decreased experimentally from 6.4 to 2.6, the concentrations of dissolved trace metals increased by factors of 2200 for Pb, 160 for Cu, 21 for Zn, 9 for Cd, 8 for Ni, and 5 for Co. Th e order in which metals were released with decreasing pH was the reverse of that reported for pH-dependent sorption of these metals in upstream systems. Substantial release of trace metals from the sediment was observed even by a modest decrease of pH from 6.4 to 5.9. Th erefore, the metal-rich sediment of the lake should be considered as potentially hazardous to bottom-dwelling aquatic species and other organisms in the local food chain. In addition, if the reservoir is dredged or if the dam is removed, the accumulated sediment may have to be treated for recovery of sorbed metals.
Minerals, 2020
The oxidation state of sulfur [S] is a primary control on mobility of metals in sediments impacted by legacy mining practices. Coeur d'Alene Lake of northern Idaho, USA, has been impacted by upstream legacy mining practices that deposited an estimated 75 Mt of metal(loid)-and S-rich sediments into the lake. Future lake conditions are expected to include algal blooms, which may alter S and metal remobilization during the seasonal euxinic environment. Cores of the lake sediments were exposed to anoxic and anoxic + algal detritus conditions for eight weeks at 4.5 • C through introduction of a N 2 atmosphere and addition of algal detritus. At a location 2.5 cm below the sediment-water interface, anoxic conditions promoted a shift in S species to continually larger concentrations of reduced species and an associated shift in the bonding environment reflective of increased S-metal bonds. Anoxic + algal detritus conditions suppressed the increasing trend of reduced S species and induced greater release of Mn compared to the anoxic-only conditions but did not appear to enhance the release of As, Cd, or Fe. The addition of algal detritus to the sediment-water interface of these Fe-and S-rich sediments enhanced mobilization of Mn likely because of dissimilatory metal reduction where the anaerobic oxidation of the algal detritus stimulated Mn reduction. Results of the study indicate that future metal release from the lake sediments will be altered with the likely deposition of algal detritus, but the effect may not enhance the release of acutely toxic metals, such as As or Cd, or substantially impact Fe cycling in the sediments.
Redox and pH conditions in the water column and in the sediments of an acidic mining lake
Journal of Geochemical Exploration, 2001
Physico-chemical parameters of the acidic mining lake (ML) 111 in the Lusatian region (Germany) were determined in April and August 1997 using a multiparameter probe for the water column and punch-in pH and Eh electrodes for the sediment, respectively. Samples of the sediment pro®le were taken by a gravity corer. Besides determination of the physico-chemical parameters, grain size and water contents were determined after sediment slicing. Differences in the redox state of the water body, deduced from oxygen saturation between April and August, could not be inferred. However, a shift in pH to lower values was apparent. Data support the conclusion that the enhanced oxygen content was consumed for oxidation of ferrous iron to ferric iron (oxides/hydroxides) coupled with the release of protons. In the sediment, different buffer systems of iron compounds could be detected within separate zones with values below and above pH 3. At higher pH values, the redox conditions are controlled and stabilized by the presence of Fe-oxide-hydroxides and possibly Fe-sulfates.