Assessment of Hydrogeochemical Processes and Mine Water Suitability for Domestic,Irrigation, and Industrial Purposes in East Bokaro Coalfield,India

Mine water samples collected from the East Bokaro coalfield were analysed to assess suitability for domestic, irrigation, and industrial purposes. The pH of the samples ranged from 6.78 to 8.11 in the pre-monsoon season, 5.89–8.51 during the monsoon season, and 6.95–8.48 in the post-monsoon season. The anion chemistry was dominated by HCO₃^? and SO₄^2?, with minor amounts of Cl^?, NO₃^? and F^?. The Fe concentrations exceeded the maximum permissible limit of the BIS drinking water standard in about 44% of the collected samples. Turbidity, TDS, Fe, total hardness (TH), SO₄^2?, and Mg²⁺ also sometimes exceeded drinking water limits. The TDS, TH and SO₄^2? concentrations of the mine water makes it unsuitable for domestic purposes or for industrial use; high values of %Na, SAR, RSC, and Mg-hazard at certain sites restrict its suitability for agricultural use.     

Hydrogeochemistry,Elemental Flux,and Quality Assessment of Mine Water in the Pootkee-Balihari Mining Area,Jharia Coalfield,India

Ninety nine mine water discharge samples were collected and analyzed for pH, electrical conductivity (EC), major cations, anions, and trace metals in the Pootkee-Balihari coal mining area of the Jharia coalfield. The mines of the area annually discharge 34.80 × 10⁶ m³ of mine water and 39,099 t of solute loads. The pH of the analyzed mine waters ranged from 6.97 to 8.62. EC values ranged from 711 μS cm⁻¹ to 1862 μS cm⁻¹, and reflect variations in lithology, geochemical processes, and hydrological regimes in the mines. The cation and anion chemistry indicate the general ionic abundance as: Mg²⁺ > Ca²⁺ > Na⁺ > K⁺ and HCO₃ ⁻ > SO₄ ²⁻ > Cl⁻ > NO₃ ⁻ > F⁻, respectively. Elevated SO₄ ²⁻ concentrations in the Gopalichuck, Kendwadih, and Kachhi-Balihari mine waters are attributed to pyrite weathering. The water quality assessment indicated that TDS, hardness, Mg²⁺, and SO₄ ²⁻ are the major parameters of concern in the study area. Except for Fe, all of the measured metals in the mine water were well within the levels recommended for drinking water. With only a few exceptions, the mine water is of good to permissible quality and suitable for irrigation.     

Environmental Geochemistry and a Quality Assessment of Mine Water of the West Bokaro Coalfield,India

Mine water from the West Bokaro coalfield was qualitatively assessed with respect to domestic and irrigation criteria. Thirty water samples from different mines were collected and analyzed for pH, electrical conductivity, total dissolved solids (TDS), total hardness, major cations, anions, and dissolved silica. The pH of the samples ranged from 6.6 to 8.3 in the post-monsoon season and 6.7–8.4 in the pre-monsoon season, indicating its near-neutral to slightly alkaline nature. TDS ranged from 349 to 1029 mg L^?1 in the post-monsoon season and 499–1458 mg L^?1 in the pre-monsoon season. The spatial differences in TDS reflect the local lithology, surface activities, and hydrology. Ca–Mg–SO₄ and Ca–Mg–HCO₃ were the dominant hydrogeochemical facies; SO₄ ^2? and HCO₃ ^? were the dominant anions and Ca²⁺ and Mg²⁺ were the dominant cations during both seasons. High SO₄ ^2? concentrations are attributed to oxidative weathering of pyrite and gypsum dissolution. Computed supersaturation with respect to dolomite and calcite for most samples may result from the dissolution of gypsum after the water is saturated with respect to the carbonate minerals. Despite moderate to high TDS, total hardness, and SO₄ ^2? concentrations, most of the sampled mine water was of good to permissible quality for irrigation; however, locally higher salinity and Mg restrict its suitability for irrigation at some sites.     

Evaluation of the Potential for Beneficial Use of Contaminated Water in a Flooded Mine Shaft in Butte,Montana

The mines of Butte, Montana include over 16,000 km of abandoned underground workings, most of which are now filled with water. The feasibility of using the flooded mine workings as a source of irrigation water was investigated. The geochemistry and stable isotopic composition of water produced during a 59 day pumping test of the flooded Belmont Mine workings are described. Although static water in the pumping well initially met proposed irrigation standards, the quality deteriorated during pumping as water from deeper in the mine complex was drawn into the well. Stable isotopes show that this lower-quality water was not sourced from the nearby Berkeley Pit lake, but most likely came from the mine shaft itself. At steady state, the water pumped to the surface had pH 5.5–6.0 with high concentrations (in mg/L) of dissolved SO₄ (1,600), Fe (160), Mn (19), Zn (15), and As (1.8). Despite substantial bicarbonate alkalinity (≈150 mg/L as CaCO₃), the water became strongly acidic after equilibration with air due to oxidation and hydrolysis of Fe²⁺. Benchtop experiments were performed to test different strategies for low-cost chemical treatment prior to irrigation. The most feasible alternative involved aeration (to remove large quantities of dissolved CO₂) prior to pH adjustment to >9 with lime or NaOH. Further work is needed to see if such treatment is economically viable compared to the cost of using municipal water. Another concern is whether irrigation of grass with high TDS, high sulfate water is sustainable. The mine water reached a steady-state temperature of 19°C during pumping, and therefore the possibility of using this water to help heat nearby buildings should also be explored.     

The Combined Impact of Mine Drainage in the Ankobra River Basin,SW Ghana

This study assessed the combined effects of seven large-scale gold mines, one manganese mine, and scattered artisanal gold mining sites on the quality of water in the Ankobra Basin in a geologically complex terrain. Water samples from streams, boreholes, hand dug wells, and mine spoil were analysed. Scatter plots of trends among measured parameters were used to assess drainage quality and differential impacts. Drainage quality exhibits wide seasonal and spatial variations; the geology strongly influences the water chemistry. Areas with low pH (<5.5), and high sulphate ions and trace ions are suggestive of acid mine drainage while sites with high pH (>7.5), HCO₃ ⁻, subdued SO₄ ²⁻, and high trace ions are suggestive of sites where acid neutralization is effective. High metal sources are largely confined to mining operations in the Birimian formation with ores containing more than 2% sulphides. However, restricted high metal regimes are observed in drainage in the Tarkwaian formation associated with scatted sulphide-bearing dolerite dykes in the operational areas of the Tarkwa and Damang mines. Earlier studies disputed sulphides in the Tarkwaian formation until recently, when acid-generating dykes were discovered in operating pits. The most degraded waters emanate from the Prestea and Iduapriem mines, and to a lesser extent, the Nsuta mine sites, all mining Birimian rocks. The Tarkwa mine showed minimal metal loading. Zn, Cu, Ni, As, SO₄, pH, and specific conductance are essential and adequate parameters in determining if acid drainage is taking place at these sites, and are recommended for routine mine environmental monitoring.     

Geochemistry,Hydraulic Connectivity and Quality Appraisal of Multilayered Groundwater in the Hongdunzi Coal Mine,Northwest China

This study assessed the geochemistry and quality of groundwater in the Hongdunzi coal mining area in northwest China and investigated the mechanisms governing its hydrogeochemistry and the hydraulic connectivity between adjacent aquifers. Thirty-four groundwater samples were collected for physicochemical analyses and bivariate analyses were used to investigate groundwater quality evolution. The groundwater in the mine was determined to be neutral to slightly alkaline, with high levels of salinity and hardness; most samples were of SO₄·Cl–Na type. Fluoride and nitrate pollution in the confined aquifers were identified, primarily sourced from coals. Natural geochemical processes, such as mineral dissolution, cation exchange, and groundwater evaporation, largely control groundwater chemistry. Anthropogenic inputs from agricultural and mining activities were also identified in both shallow unconfined aquifers and the deeper confined aquifers, respectively. It was determined that the middle confined aquifer has a high hydraulic connectivity with the lower coal-bearing aquifer due to developed fractures. Careful management of the overlying aquifers is required to avoid mine water inrush geohazards and groundwater quality deterioration. The groundwater in the mining area is generally of poor quality, and is unsuitable for direct human consumption or irrigation. Na⁺, SO₄^2?, Cl^?, F^?, TH, TDS, NO₃^?, and COD_Mn are the major factors responsible for the poor quality of the phreatic water, while Na⁺, SO₄^2?, F^?, and TDS are the major constituents affecting the confined groundwater quality. This study is beneficial for understanding the impacts of coal mine development on groundwater quality, and safeguarding sustainable mining in arid areas.     

Development and Validation of a Spectrophotometric Method to Measure Sulfate Concentrations in Mine Water without Interference

Sulfate concentrations are determined in mine water by gravimetric, titrimetric, colorimetric, turbidometric, ion chromatographic, inductively coupled plasma absorption spectrophotometric, and other methods. Accurate sulfate measurement of mine water can be difficult due to interfering groups, cations, and anions, mainly arsenate (AsO₄ ³⁻) and phosphate (PO₄ ³⁻). In this paper, a simple and effective spectrophotometric method is described for the determination of sulfate in mine water. When the SO₄ ²⁻ reacts with barium chloranilate at pH 4.5 in aqueous ethyl alcohol solution, it releases acid-chloranilate, which shows maximum absorption at 350 nm and obeys Beer’s law over the concentration range of 10–1,000 mg/L. Results show that the proposed method was significantly more accurate than a conventional method. Absorbance was found to increase linearly with increasing concentration of sulfate, which is corroborated by the calculated correlation coefficient value of 0.999 (n = 7). The slope and intercept of the equation of the regression line were 0.00091 and 0.00778, respectively. The limit of detection and limit of quantification were found to be 0.03861 and 0.06774 mg/L, respectively. The validity of the described procedure was assessed. Statistical analysis of the result indicated high accuracy and good precision. The proposed method was successfully applied in mine water without interference from common groups like AsO₄ ³⁻ and PO₄ ³⁻. The relative standard deviations of the proposed method ranged from 0.03 to 0.26%, with recoveries of 99.79–101.57%.     

Impact of lead/zinc ore mining on groundwater quality in Trzebionka mine (southern Poland)

The intensive mining activity carried out by “Trzebionka” zinc-lead mine causes changes in the hydrodynamic regime of the triassic aquifer as well as essential changes in the chemical composition of the groundwater. The mine water, in comparison with groundwaters collected directly from fractures and Karstic channels and with groundwaters pumped out from wells situated in Chrzanow region, is characterized by higher contents of almost all major dissolved constituents as, well as, many trace elements. Hydrogeochemical background of triassic carbonate series aquifer has been elaborated. Largest anomalies in extent of almost all elements have occurred in area of the “Trzebionka” mine. In this water general trend of increase of pH, total dissolved solids and SO₄ ²⁻ concentration with simultaneous trends of decrease of Zn²⁺ and Pb²⁺ concentrations have been noticed. Water pumped out from the mine in spite of its low quality, is utilized in about 80% as potable water after undergoing complicated treatment.     

Research on mechanism of groundwater pollution from mine water in abandoned mines

In order to understand the mechanism and regularity of the groundwater contamination from mine water of abandoned mines, experiments were conducted on an abandoned coal mine in Fuxin, a representative city with lots of mine water in northeast China. The groundwater pollution from different contaminants of coal-mining voids (total hardness, SO₄²⁻, Cl⁻ and total Fe) and pollution factors transportation situation in the coal rock were simulated by soil column experiment under the conditions of mine water leaching and main water leaching (similar to rainwater leaching), and the water-rock interaction mechanism was discussed during mine water infiltration through saturated coal rock by application of principle of mass conservation, based on physical properties of coal rock, as well as monitored chemical composition. The results show that, compared with the clear water leaching process, trends of change in pollutant concentrations presented different characteristics in the mine water leaching process. Groundwater is contaminated by the water rock interactions such as migration & accumulation, adsorption & transformation, dissolution & desorption and ion exchange during the mine water permeation. The experiments also suggest that at first dissolution rate of some kinds of dissoluble salts is high, but it decreases with leaching time, even to zero during both the mine water leaching and main water leaching. Supported by the National Natural Science Foundation of China(50434020, 50374042), Science & Technology Found of Liaoning Province (20022155); Specialized Research Fund for the Doctoral Program of Higher Education (20040147003)     

Alkalinity generation and metals retention in a successive alkalinity producing system

Alkalinity generation and metals retention were evaluated during the initial year of operation of a treatment wetland, consisting of four 185 m² inseries cells comprised of alternating vertical-flow anaerobic substrate wetlands (VFs) and surface-flow aerobic settling ponds (SFs). The substrate in the VFs consists of spent mushroom substrate (SMS) and limestone gravel, supplemented with hydrated fly ash in a 20∶10∶1 ratio by volume. Approximately 15±4 L/min of acid mine drainage (AMD) from an abandoned underground coal mine in southeastern Oklahoma, USA, was directed to the system in October 1998 (mean influent water quality: 660 mg L⁻¹ net acidity as CaCO₃ eq., pH 3.4, 215 mg L⁻¹ total Fe, 36 mg L⁻¹ Al, 14 mg L⁻¹ Mn, and 1000 mg L⁻¹ SO₄ ⁻²). Flow through the first VF resulted in substantial increases in alkalinity, decreased metal concentrations and circumneutral pH. 258±84 mg L⁻¹ of alkalinity was produced in the first VF by a combination of processes. Final discharge waters were net alkaline on all sampling dates (mean net alkalinity=136 mg L⁻¹). Total Fe and Al concentrations decreased significantly from 216±45 to 44±28 mg L⁻¹ and 36±6.9 to 1.29±4.4 mg L⁻¹, respectively. Manganese concentrations did not change significantly in the first two cells, but decreased significantly in the second two cells. Mean acidity removal rates in the first VF (51 g m⁻² day⁻¹) were similar to those previously reported.     

Dissolution Kinetics of Sulfate from Schwertmannite Under Variable pH Conditions

Sulfate mobilization was investigated under controlled laboratory conditions. Microbially synthesized schwertmannite (14.7 m²/g specific surface area with 4.7 Fe:S molar ratio) was interacted at room temperature for 4 months with aqueous solutions between pH 5 and 8. More than 50% of the solid-phase sulfate was released during the initial 2 months and the rate was positively influenced by pH due to the competition of hydroxyl ions for SO₄ ²⁻. More than 90% of the solid-phase sulfate was released within 4 months at pH 8. Infrared spectra demonstrate diminution and splitting of SO₄ ²⁻ adsorption bands, indicating possible structural changes within the solid phase as a result of SO₄ ²⁻ release. Transformation of schwertmannite to goethite was triggered by pH increase and was primarily responsible for the sulfate mobilization. Thus, schwertmannite that interacts with neutral to alkaline water can add significantly to the sulfate load of a stream.     

Hydrotalcite Formation for Contaminant Removal from Ranger Mine Process Water

Process water from the Ranger Uranium Mine requires treatment to meet stringent environmental water quality criteria. The acidic water contains substantial SO₄, metals, and U. One novel treatment method under consideration is the use of Na-aluminate to both neutralise the process water and precipitate hydrotalcites. Hydrotalcites are a class of Mg–Al layered double hydroxide minerals with a typical endmember chemical composition: Mg₆Al₂(A)(OH)₁₆·n(H₂O), where A = CO₃ ²⁻, SO₄ ²⁻, etc. Many acidic wastewaters contain Mg and/or Al in sufficient abundance for hydrotalcite formation upon addition of alkali to achieve solution pH > 5, and Mg and/or Al to attain a Mg:Al ratio of 2 to 3:1. The utility of hydrotalcites lies in their ability to incorporate a range of cationic (Cu²⁺, UO₂ ²⁺), metalloid (AsO₄ ³⁻), and (oxy)anionic contaminants (CrO₄ ²⁻). The broad spectrum removal of contaminants, including U, also indicates that hydrotalcites and their derivatives could potentially be used as a containment material in nuclear waste repositories. In this study, Ranger process water derived from extraction of U from chloritic schist was treated with Na-aluminate sourced from Bayer process liquor, in combination with NaOH or Ca(OH)₂. Hydrotalcites formed as the primary mineral during process water neutralisation with the ability to simultaneously remove a suite of contaminants from solution.     

The Sustainability of Irrigation with Gypsiferous Mine Water and Implications for the Mining Industry in South Africa

The sustainability of irrigation with gypsiferous mine water and different irrigation management practices was evaluated using a milti-disciplinary approach, where crop response was investigated along with the impact on soil and groundwater resources. Field trials carried out at two mines (Landau and Kleinkopje Colliery, Mpumalanga Province, South Africa) indicated that a wide range of species can be cropped for commercial purposes under irrigation with this water. Chemical analyses of groundwater underlying irrigated areas indicated that contamination of groundwater did not occur after three years. The results of a glasshouse trial indicated that the inclusion of NH₄ ⁺ for N-fertilization in a NO₃ ⁻-NH₄ ⁺ ratio of 2:1 to 1:1 is advantageous to root and top growth of wheat. According to simulations run with the Soil Water Balance (SWB) model and the CLIMGEN weather data generator, soil chemical and physical properties will not be irreparably damaged after thirty years of irrigation. Perennial pastures, irrigated at high frequency, provided the highest net farm income and water utilization.     

Treatment of a Jordanian Phosphate Mine Wastewater by Hybrid Dissolved Air Flotation and Nanofiltration

Approximately 10,000?m3/day of untreated wastewater is produced during phosphate beneficiation at Eshydia phosphate mine in southern Jordan. The effluent contains 21?wt% phosphates (P₂O₅) and 12–14?wt% solids. Dissolved air flotation (DAF) and subsequent nanofiltration (NF) were investigated as potential treatment methods. DAF combined with the use of a commercial flocculant effectively removed the suspended solids and decreased total dissolved solids (TDS) by 50?%; NF effectively treated the DAF effluent and produced water with only 860?ppm TDS. The treated water can be recycled for use by Eshydia phosphate mine or for irrigation.     

The removal of sulfate and metals from mine waters using bacterial sulfate reduction: Pilot plant results

A treatment process that bacterially converts sulfate into elemental sulfur via a hydrogen sulfide intermediate was demonstrated at pilot scale for the treatment of three mine waters that contained metals and sulfate. Ethanol served as the bacterial carbon and energy source. The mine waters were treated at rates that ranged from 50–150 L day⁻¹. Contaminant concentrations up to 13 mg L⁻¹ copper, 0.1 mg L⁻¹ mercury, 0.04 mg L⁻¹ cadmium, 3.5 mg L⁻¹ zinc, 0.68 mg L⁻¹ cobalt, 1.3 mg L⁻¹ nickel, 49 mg L⁻¹ iron, and 63 mg L⁻¹ aluminum were removed to meet water quality effluent limits. Manganese removal was about 80% under normal operating conditions but increased to 96% when the process was optimized for manganese removal. The process was shown to be capable of decreasing sulfate concentrations from 1800 mg L⁻¹ to less than 250 mg L⁻¹, nitrate from 100 mg L⁻¹ to less than 1 mg L⁻¹, arsenic from 8 mg L⁻¹ to less than 0.03 mg L⁻¹, and calcium from 310 mg L⁻¹ to less than 100 mg L⁻¹. Acid mine waters were neutralized using bacterially-generated alkalinity; no external alkalinity source was needed.     

矿区地下水环境演化的模拟试验研究

以皖北矿区恒源煤矿作为研究区域,通过室内模拟淋滤试验,检测淋滤液中的Na+,SO42-,F-,Fe,总溶解固体,总硬度等污染组分的质量浓度以及pH,电导率,分析研究岩样在淋滤作用下的污染组分的溶出规律以及其随淋滤量增加而衰减的拟合衰减幂数曲线。结果表明,淋滤液中pH值变化不明显,呈中性偏弱酸性,SO42-,F-,Mn等组分超标,其他重金属Cr,Cu,Pb,Cd等未检出;在淋滤试验前期,部分污染组分浓度很高,如Na+,总溶解固体和总硬度等,后期随着淋滤量的增加而呈现衰减趋势,并趋于稳定,其衰减方程基本符合幂数关系。表明在淋滤作用下岩样污染组分对地下水水质存在影响,且在一定程度上影响着地下水环境演化过程。     

Groundwater Geochemical Variation and Controls in Coal Seams and Overlying Strata in the Shennan Mining Area,Shaanxi, China

Water resource conservation and ecological protection are key coal mining issues in northern Shaanxi Province and the Yellow River Basin. Revealing the characteristics and variation patterns of groundwater quality in the coal series and its overlying aquifers can provide a geological foundation for solving or optimizing these issues. Taking the Zhangjiamao coal mine of the Shennan mining area in northern Shaanxi Province, western China, as an example, water samples were collected for analysis from the: quaternary strata, weathered bedrock, burnt rock, coal series, and coal seam. Test parameters included conventional ion concentrations, total dissolved solids (TDS), and pH. Key water chemistry indicators such as oxidation/reduction index (ORI) and groundwater chemical closure index (GCCI) were used to explain the water quality differences. The Quaternary water, burnt rock water, and weathered bedrock water were dominantly the Ca–HCO₃ type, the coal series water (Yan’an Formation) was dominantly Ca–HCO₃ and Na–Cl types, and the coal seam water was dominantly Na–Cl type. From the shallow groundwater to coal seam water, dissolution and leaching gradually decrease and degree of retention gradually increases. Coal seam water was characterized by high TDS, high GCCI, and low ORI, reflecting a closed hydrogeochemical environment and moderate sulfate reduction. Leaching, salt accumulation, sulfate reduction, and cation exchange jointly control the groundwater chemical characteristics and evolution of the coal series and its overlying aquifers. Salt accumulation and cation exchange reactions of the stagnant coal seam water in the arid and semiarid climates and shallow buried conditions result in increased mineralization; the water quality is vastly different from that of the overlying aquifers, which are dominated by leaching. Groundwater circulation in the coal series and coal seam are of the infiltration–retention type, and the overlying aquifer of the coal series are of the infiltration–runoff type. A comprehensive hydrogeological model was constructed of the Middle Jurassic coal series and its overlying aquifers in the area. The results of this study have implications for the identification of mine water influx sources in the Shennan mining area, and the understanding of controls on the groundwater geochemical variation in Jurassic coal field of western China.

     

The Effects of Sulfate on the Physical and Chemical Properties of Actively Treated Acid Mine Drainage Floc

It is important to consider floc properties when designing acid mine drainage treatment (AMD) systems. Relatively few studies have evaluated the effects of neutralizing base, neutralization pH, and sulfate in solution on floc properties in active treatment systems. We used NaOH and NH₄OH as neutralizing bases, 0:1, 2.5:1, and 5:1 SO₄:Fe molar ratios, and neutralization pH of 7, 8, and 9 in laboratory studies. Neutralizing cation, sulfate content, and neutralization pH had significant effects on floc mass and volume, but SO₄:Fe ratio was the most important parameter. Settled floc volumes were slightly larger in the sodium system. Floc mass and volume both decreased with increasing pH. Floc generated in the presence of sulfate required significantly more time to reach a total suspended solids discharge limit of 70 mg L⁻¹, had slower initial settling rates, and smaller settled volumes than floc generated without sulfate. The systems we studied were less complicated than actual AMD, but understanding the effects of sulfate, neutralizing cation, and neutralization pH on floc properties may help to design more efficient treatment systems. Choosing the appropriate treatment chemical and designing adquate pond sizes will ultimately increase treatment efficiency and improve stream water quality.     

Alkalinity Generation in a Novel Multi-stage High-strength Acid Mine Drainage and Municipal Wastewater Passive Co-treatment System

Passive co-treatment of high-strength acid mine drainage (AMD) and municipal wastewater (MWW) was examined in a laboratory-scale, four-stage continuous flow reactor system with a total residence time of 6.6 d. Synthetic AMD of pH 2.60 and an acidity of 1,870 mg/L (as CaCO₃) was mixed at a 1:2 ratio with raw MWW (pH 7.67, 288 mg/L alkalinity (as CaCO₃), and 265 mg/L BOD₅) from the City of Norman, Oklahoma and introduced into the system. Alkalinity generated by limestone dissolution and bacterial SO₄ ²⁻ reduction (BSR) processes was sufficient to support various metal removal processes and produce an effluent with circumneutral pH (6.98) and a net alkalinity of 10.4 mg/L (as CaCO₃). Alkalinity generation from limestone dissolution was comparable with conventional AMD passive treatment systems. BSR proceeded at a relatively high rate (0.56 mol/m³ day) despite inhibitory pH and metals concentrations. Results indicate that the diverse electron donors in the MWW may be as suitable for BSR and their supporting microbial communities as commonly used substrates, presenting an opportunity to use a common waste as a resource for passive treatment.     

Mine Water Tracing – A Tool for Assessing Flow Paths in Flooded Underground Mines

A tracer test developed for hydrodynamic investigations has been successfully tested in German underground mines and the results of one of those tests are reported on here. The objectives of the test were to investigate the kind and rate of flow within a flooded mine. At each sampling point, coloured spores were injected using a Lycopodium apparatus. Beginning one day after injection, two samples were collected per weekday at each sampling point. A considerably good recovery rate of 2% was obtained. The mean velocity of the mine water within the investigated part of the mine was 2.6 m min⁻¹ and the different parts of the mine proved to be hydraulically well connected with each other. It appears that the hydrodynamic system within the flooded mine is dominated by convective flow from deeper parts of the mine to higher ones.