某废弃煤矿有机污染场地地下水修复治理中试研究

某废弃煤矿竖井经倾倒有机废液,导致环境污染事件,造成巷道及采空区内地下水污染。本文结合场地实际情况,选取倾倒竖井(事故井)及周边区域为中试区域,采用“抽出处理+原位氧化循环”两阶段联合修复技术对污染场地开展中试研究。本文介绍了场地污染概况、地下水修复中试方案设计和实施,以及对修复效果进行评价。结果表明,中试处理后地下水中COD和二氯甲烷最高去除率分别为97.88%和99.74%。中试试验表明, “抽出处理+原位氧化循环”两阶段修复技术,对处理矿区内巷道及采空区等复杂地层结构下深层地下水中有机污染物具有较好的去除效果,可以结合现场实际情形对整个污染场区进行规模应用。     

The geotechnical characteristics and stability of a spoil heap at a southwestern pennsylvania coal mine, U.S.A.

The mechanical and geotechnical properties of bulk samples and samples extracted from boreholes through a sliding spoil heap at a southwestern Pennsylvania coal mine are examined. Size gradation, moisture content, density and strength are found to vary considerably within the spoil. Gradation results suggest the material type to be more important than the age of spoil in degradation. There is also evidence from analysis that the heterogeneity of spoil and its associated density and strength do not significantly affect stability results. In other words, spoils can be sufficiently heterogeneous for purposes of stability analysis; they can be considered statistically homogeneous with regard to shear strength.     

Influence of water chemistry on the distribution of an acidophilic protozoan in an acid mine drainage system at the abandoned Green Valley coal mine,Indiana, USA

Euglena mutabilis, a benthic photosynthetic protozoan that intracellularly sequesters Fe, is variably abundant in the main effluent channel that contains acid mine drainage (AMD) discharging from the Green Valley coal mine site in western Indiana. Samples of effluent (pH 3.0–4.6) taken from the main channel and samples of contaminated stream water (pH 3.3 to 8.0) collected from an adjacent stream were analyzed to evaluate the influence of water chemistry on E. mutabilis distribution. E. mutabilis communities were restricted to areas containing unmixed effluent with the thickest (up to 3 mm) benthic communities residing in effluent containing high concentrations of total Fe (up to 12110 mg/l), SO₄ (up to 2940 mg/l), Al (up to 1846 mg/l), and Cl (up to 629 mg/l). Communities were also present, but much less abundant, in areas with effluent containing lower concentrations of these same constituents. In effluent where SO₄ was most highly concentrated, E. mutabilis was largely absent, suggesting that extremely high concentrations of SO₄ may have an adverse effect on this potentially beneficial Fe-mediating, acidophilic protozoan.     

Field scale remediation of mine wastes at an abandoned gold mine,Australia II: Effects on plant growth and groundwater

This second paper reports the results of plant growth, plant mortality, plant leaf tissue metal and salt concentrations and leachate quality monitoring from lysimeters in four large field trial treatments established on sulfidic waste rock/soil that was used for haul road construction at a closed gold mine in Australia. The TerraB™, lime and clay treatments allowed good tree growth of four Eucalypt species, compared to the control. There was no statistical difference in tree growth between the TerraB™, lime or clay treatments over the 2 years of monitoring in this paper. However, the growth of one tree species was poor in the TerraB™ treatment. Leaf tissue metal and major ion data are also presented. Leachate pH in the control became increasingly acidic (pH 4.57–3.95). The addition of Ca(OH)₂ and biosolids led to an initial increase in leachate pH, compared to the control; however, this has decreased over the duration of the study (pH 5.37–4.89) and may affect the sustainable growth of plants in the future. In the TerraB™ and biosolids treatment leachate pH increased to 6.92 after the first rainfall event and continued to increase over the duration of the study to pH 7.4 after 24 months. After 24 months average heavy metal leachate concentrations (mg/L) in the lysimeters for Al, Cd, Cu, Mn and Zn were, control: 32.55, 5.67, 12.71, 39.29, 121.80, TerraB™: 0.07, 0.02, 0.07, 0.57, 0.23, and lime: 2.19, 1.19, 2.33, 3.6, 28.4. No leachate was available for collection from the clay treatment indicating that this technique was functioning in terms of minimizing the infiltration of water into the mine soil.     

Depositional patterns of Pennsylvanian sediments in Sullivan County, West-Central Indiana, U.S.A.

Individual Pennsylvanian clastic sediment intervals above the Seelyville Coal were examined on electric logs from Sullivan County, Indiana, U.S.A. for vertical sequence, interval thickness, and sand content. This information was used to evaluate local variability of this area of the Illinois Basin depositional system.Each clastic interval is composed of a lateral association of vertical sequences of sediments, bounded above and below by a thin association of coal, limestone, black shale, and/or underclay. An “average” constructive clastic unit is characterized by the following thickness parameters: mean , standard deviation (s) = 3.4 m, minimum = 6.1 m, and

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sand content, as measured by electric log resistivity, is 37%.Clastic sediment intervals characterized as “deep water” sediments tend to be clayrich, have the greatest lateral continuity, are composed of 50% to 90% coarsening upward sequences, are comprised of less than 16% fining upward sequences, and are composed of less than 10% of sequences of facies which are transitional between coarsening and fining upward. Sandstone channels are linear to coarsely dendritic and probably postdate lower portions of the coarsening upward sequences. One example of longshore shoaling between the Springfield and Houchin Creek coals was discovered. This is the youngest stratigraphic evidence of longshore currents in Illinois Basin clastic sediments. This milieu probably represents a distal delta position.Shallow-water sediments are sand-rich, complex, and gradational. They tend to be interfingered and to display poor lateral continuity. Coarsening upward sequences comprise less than 20% of the data sites. Fining upward fluvial sequences are represented by well-developed dendritic map patterns and constitute 20–30% of the sites. Transitional sequences between coarsening and fining upward log profiles are represented by both interfingered and gradational sequences and constitute 20–55% of the sites.Each constructive vertical sequence represents only a portion of the overall progradational deltatic environment.Destructive linear erosional channels are oriented downdip into the basin. The first occurrence in Indiana of the Trivoli Sandstone channel facies, located between the Ditney and West Franklin horizons, was delineated. Destructive channel sands are found commonly between the Houchin Creek and Colchester coals.Clastic subintervals locally began to develop when compacted unit thickness exceeded 18 m.Average regional wedging contributes 0.13 m/km to local sediment interval thickness variability. The average compacted clastic interval thickness has a local range of 19 m owing to local depositional environments. This variation is related closely to the overall clastic ratio of end-member sequences which are situated in close proximity. The average clastic unit varies in thickness of ± 1.4 m owing to the influence of compaction of the underlying Pennsylvanian sediment filling the Mississippian unconformity valleys. Compactional effects between clastic units become negligible as composite interval thickness exceeds 30 m.     

Paleoenvironmental analysis of a middle Wisconsinan biota site, southwestern Virginia, U.S.A.

The Ratcliff Site in southwestern Virginia lies in a small second-order stream valley filled with approximately 3.5 m of organic-rich deposits that contain bones of mammoth, mastodon, deer (or antelope), logs, and plant macrofossils. Radiocarbon analyses indicate the age of the organic-rich sediment ranges from > 44,000 to 29,100 ¹⁴C yr BP, a time period with no fossil remains reported in this region of the Appalachians. Analyses of field observations, textural data, organic carbon content, and plant macrofossils indicate that the organic-rich sediments contain interbedded standing-water and debris-flow deposits. Up to 6 m of oxidized debris-flow sediments bury the organic-rich sediments. The presence of Rubus parviflorus (Thimble Berry) throughout the deposit indicates the site had a boreal environment from > 44,000 to 29,100 ¹⁴C yr BP. Plant macrofossil evidence indicates the uplands had stands of spruce/jack-pine forests while the valley contained ponds and associated wetlands. Three debris flows occurred at the site between approximately 38,000 and 29,000 ¹⁴C yr BP, suggesting a recurrence interval for major storms of approximately 3000 yr, even though the apparent stability of the boreal environment implies a climate not conducive to catastrophic rainstorms. This conflicting combination of features suggests that during the middle Wisconsinan this area experienced generally cool climates, dominated by polar air masses, but was punctuated by relatively brief warm periods marked by incursions of tropical air masses.     

Some effects of human modifications on sand-bed channels in southwestern Mississippi,U.S.A.

This study examines the effects of land-use changes and channel foreshortening on the sediment regime and channel morphology of two sand-bed rivers in southwestern Mississippi. Historical data including sequences of channel surveys at various bridge sites document the impact of these human modifications. Land-use changes caused an increase in point bar size, but this trend was found to be reversed as the result of conservation and reforestation practices. Channel foreshortening has produced a knickpoint that has migrated 50 km upriver. River response to this disturbance included 5 m of channel incision, a 4.5-fold increase in bankfull width, and a fourfold increase in point bar size.     

Primitive and contaminated basalts from the Southern Rocky Mountains,U.S.A.

Basalts in the Southern Rocky Mountains province have been analyzed to determine if any of them are primitive. Alkali plagioclase xenocrysts armored with calcic plagioclase seem to be the best petrographic indicator of contamination. The next best indicator of contamination is quartz xenocrysts armored with clinopyroxene. On the rocks and the region studied, K₂O apparently is the only major element with promise of separating primitive basalt from contaminated basalt inasmuch as it constitutes more than 1 % in all the obviously contaminated basalts. K₂O: lead (> 4 ppm) and thorium (> 2 ppm) contents and Rb/Sr (> 0.035) are the most indicative of the trace elements studied. Using these criteria, three basalt samples are primitive (although one contains 1.7% K₂O) and are similar in traceelement contents to Hawaiian and Eastern Honshu, Japan, primitive basalts.Contamination causes lead isotope ratios, ²⁰⁶Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb, to become less radiogenic, but it has little or no effect on ⁸⁷Sr/⁸⁶Sr. We interpret the effect on lead isotopes to be due to assimilation either of lower crustal granitic rocks, which contain 5–10 times as much lead as basalt and which have been low in U/Pb and Th/Pb since Precambrian times, or of upper crustal Precambrian or Paleozoic rocks, which have lost much of their radiogenic lead because of heating prior to assimilation. The lack of definite effects on strontium isotopes may be due to the lesser strontium contents of granitic crustal rocks relative to basaltic rocks coupled with lack of a large radiogenic enrichment in the crustal rocks.Lead isotope ratios were found to be less radiogenic in plagioclase separates from an obviously contaminated basalt than in the primitive basalts. The feldspar separate that is rich in sodic plagioclase xenocrysts was found to be similar to the whole-rock composition for ²⁰⁶Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb whereas a more dense fraction probably enriched in more calcic plagioclase phenocrysts is more similar to the primitive basalts in lead isotope ratios.The primitive basalts have: ²⁰⁶Pb/²⁰⁴Pb 18.09–18.34, ²⁰⁷Pb/²⁰⁴Pb 15.5, ²⁰⁸Pb/²⁰⁴Pb 37.6–37.9, ⁸⁷Sr/⁸⁶Sr 0.704–0.705. In the primitive basalts from the Southern Rocky Mountains the values of ²⁰⁶Pb/²⁰⁴Pb are similar to values reported by others for Hawaiian and eastern Honshu basalts and abyssal basalts, whereas ²⁰⁸Pb/²⁰⁴Pb tends to be equal to or a little less radiogenic than those from the oceanic localities. ⁸⁷Sr/⁸⁶Sr appears to be equal to or a little greater than those of the oceanic localities. These ²⁰⁶Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios are distinctly less radiogenic and ⁸⁷Sr/⁸⁶Sr values are about equal to those reported by others for volcanic islands on oceanic ridges and rises.Publication authorized by the Director, U.S. Geological Survey     

Modeling and monitoring of mine water rebound in an abandoned coal mine complex: Siersza Mine, Upper Silesian Coal Basin, Poland

A variable-volume, head-dependent mine water filling model (MIFIM) has been utilized to simulate the post-abandonment flooding of the Siersza coal mine in the Upper Silesian Coal Basin of southern Poland. It is demonstrated that desaturated pore space in the aquifer adjacent to the mine comprises a significant component of the resaturable mine-related void. The model results are very sensitive to the value of this poorly constrained parameter. Nevertheless, the model successfully predicted the first appearance of mine water in an observation well and its subsequent rise. Despite this apparent success, it is concluded that such modeling approaches generally lack predictive power for mines in permeable, porous host rocks. As real monitoring data accumulate, however, such models can be calibrated and their utility increased.     

Challenges of governing groundwater in U.S. western states

Over the last several decades, water users in the western United States have increasingly turned to groundwater resources to support economic development, but few institutional arrangements were in place to govern groundwater use. Over time, numerous groundwater problems have emerged. Two closely related explanations for this are explored. Surface water sources were the first to be developed, and institutional arrangements to allocate surface water were the first to be devised. These arrangements are not particularly well suited for governing groundwater. Furthermore, the physical differences between rivers and aquifers lead to differences in the development of each type of water, and in production and organization costs. Groundwater development involves low upfront production costs, which individual water users can cover. Once groundwater users have individually invested in productive activities problems emerge, such as declining water tables. Thus, unlike surface water users, groundwater users are faced with devising institutional arrangements to coordinate their water uses after they have invested in and developed productive economic activities. Most western states regulate pumping, although groundwater users, in general, resist pumping limits. The discussion concludes with proposals for modifying the prior appropriation doctrine to better accommodate the active management of groundwater basins for long-term sustainability.

The hydrologic effects of intense groundwater pumpage in east-central Hillsborough County,Florida, U.S.A.

Well problems, water shortages, local flooding, and induced sinkholes have been periodic problems for residents in east-central Hillsborough County, Florida. This agricultural area has experienced dramatic short-term water-level declines in the Floridan aquifer from seasonal groundwater withdrawals. The sudden declines in the potentiometric surface have been caused from intense irrigation pumpage, primarily for frost and freeze protection and fruit setting. Citrus and strawberry crops are protected from occasional freezes by the application of warm groundwater to maintain minimum soil temperatures of 32°F(0°C). Local residents with inadequately constructed wells lose their source of water when the potentiometric surface is lowered to depths where their wells do not function. Some residents have lost their water supply for a week or more, and many have incurred damage to their pumps. The drawdown of the potentiometric surface in some areas has induced sinkholes causing property damage for some residents and concern for others. In addition, the high application rates for frost and freeze irrigation have created run-off problems resulting in local flooding to some residents. Fortunately, there has been no damage to resident homes from the flooding or sinkholes. This report summarizes the area's hydrogeology, and the consequences of heavy freeze irrigation. A finite-difference, numerical model is used to quantify the regional impacts to the potentiometric surface of the Floridan aquifer from estimated irrigation pumpage. Management recommendations for alleviating the problems are also discussed in the report.     

Selenium mobilization in a surface coal mine,Powder River Basin,Wyoming, U.S.A.

Elevated concentrations (0.6–0.9 mg/l) of selenium were detected in the groundwater of a small backfill area at a surface mine in the Powder River Basin, Wyoming. This report focuses on the source of selenium, its modes of occurrence in overburden deposits and backfill groundwater, and its fate. The immediate source of the selenium appeared to be the dissolution of preexisting soluble salts from the unsaturated zone of the overburden. The ultimate source of selenium was probably the oxidation of selenium-bearing pyrite in the geologic past. Overburden was placed partially in the saturated zone of the backfill where, upon resaturation, soluble salts dissolved in the groundwater. Water standing in the pit at the time of backfilling might have contributed to the elevated concentrations of selenium and other solutes. Selenium was found in an ash-rich coal and in clastic sediments in seven different modes of occurrence.The concentration of soluble selenium in the groundwater at this site has been decreasing since monitoring began in late 1982, and at the present rate of decrease, the concentration should drop below the State of Wyoming guideline of 0.05 mg/l for selenium in water intended for use by livestock by about mid-1992. The decrease in soluble selenium concentration may in part be due to microbially assisted reduction of selenate followed by sorption on clays and other sorbents.     

Empirical analysis of electromagnetic profiles for groundwater prospecting in rural areas of Ibadan, southwestern Nigeria

The Slingram electromagnetic (EM) survey using a coil separation of 60 and 100 m was carried out in ten villages in the Akinyele area of Ibadan, southwestern Nigeria to aid in the development of groundwater. Five main rock types including an undifferentiated gneiss complex (Su), biotite-garnet schist/gneiss (Bs), quartzite and quartz schist (Q), migmatized undifferentiated biotite/hornblende gneiss (M) and pegmatite/quartz vein (P) underlie the study area. A total of 31 EM profiles was made to accurately locate prospective borehole sites in the field. Four main groups with different behavioural patterns were categorized from the EM profiles. Group 1 is characterized by a high density of positive (HDP) or a high density of negative (HDN) real and imaginary curves, Group 2 by parallel real and imaginary curves intersecting with negligible amplitude (PNA), Group 3 by frequent intersection of a high density of negative minima (FHN) real and imaginary curves, and Group 4 by separate and approximately parallel (SAP) real and imaginary curves. Qualitative pictures of the overburden thickness and the extent of fracturing have been proposed from these behavioural patterns. A comparison of the borehole yield with the overburden thickness and the level of fracturing shows that the borehole yield depends more on the fracture density than on the overburden thickness. The asymmetry of the anomaly was also found to be useful in the determination of the inclination of the conductor/fracture.

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Résumé Une prospection électromagnétique Silgram (EM) utilisant une séparation de 60 et 100 m, a été réalisée sur 10 sites villageois dans la zone d’Akinyele, Ibadan, au Sud-Ouest du Nigeria, pour le développement de l’exploitation des eaux souterraines. De cette manière il a été possible de définir cinq principaux types de roches comprenant un complexe gneissique indifférencié (Su), un schiste gneissique à biotite et garnet (Bs), une quartzite et un schiste quartzitique (Q), un gneiss migmatisé à hornblende et biotite indifférenciées (M) et une veine de pegmatite et quartz recouvrant la zone d’étude. Un total de 31 profils EM a été réalisé de manière à améliorer sérieusement la localisation des forages de reconnaissance. Quatre groupes principaux ont été définis sur base de leur comportement dans les profils EM. Le Groupe 1 est caractérisé par une forte densité de courbes réelles et imaginaires, positives ou négatives (HDP ou HDN). Le Groupe 2 est caractérisé par des courbes parallèles, réelles et imaginaires, superposées à une amplitude négligeable (PNA). Le Groupe 3 rassemble les densités importantes de courbes réelles et imaginaires, d’amplitude négative minimum, fréquemment intersectées. Le Groupe 4 rassemble les courbes réelles et imaginaires, distinctes et sensiblement parallèles (SAP). Les images qualitatives de l’épaisseur de la couverture et la largeur des fractures ont pu être déterminées sur base du comportement des éléments précédemment cités. La comparaison des débits de forage, de l’épaisseur de la couche supérieure, et du degré de fracturation, montre que le débit du forage dépend plus de la densité de forage que de l’épaisseur de la couverture. L’asymétrie des anomalies a par ailleurs été très utile pour déterminer l’inclinaison des fractures conductrices.

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Resumen Se llevó a cabo un levantamiento electromagnético (EM) Slingram utilizando una separación de bobinas de 60 y 100 metros en 10 comunidades en el área Akinyele de Ibadan, suroeste de Nigeria para ayudar en el desarrollo de agua subterránea. Cinco tipos de rocas principales incluyendo un complejo de gneiss no diferenciado (Su), gneiss/esquisto de granate-biotita (Bs), cuarzita y esquisto de cuarzo (Q), gneiss de hornblenda/biotita migmatizado no diferenciado (M) y vetas de cuarzo/pegmatita (P) se encuentran en el área de estudio. Se levantaron un total de 31 perfiles EM para localizar con precisión sitios prospectivos para pozos en el campo. Se distinguieron cuatro grupos principales con diferente patrón de comportamiento a partir de los perfiles EM. El Grupo 1 se caracteriza por una alta densidad de curvas reales e imaginarias positivas (HDP) o negativas (HDN); el Grupo 2 por curvas paralelas reales e imaginarias que se interceptan con amplitud despreciable (PNA); el Grupo 3 por intersección frecuente de curvas reales e imaginarias con mínimos negativos de alta densidad (FHN); y el Grupo 4 por curvas imaginarias y reales separadas y aproximadamente paralelas (SAP). A partir de estos patrones de comportamiento se han propuesto cuadros cualitativos del espesor del material superficial y la extensión de fracturamiento. Una comparación de la productividad del pozo en relación al espesor del material superficial y el nivel de fracturamiento muestra que la productividad del pozo depende más de la densidad de fracturamiento que del espesor del material superficial. También se encontró que la asimetría de la anomalía era útil en la determinación de la inclinación de la fractura/conductor.

     

A comparison of metal attenuation in mine residue and overburden material from an abandoned copper mine

The metal attenuation capacities of secondary acid mine water precipitates is dependent upon such factors as pH, ionic strength, the presence of competing ions, and tailings mineralogy. At the abandoned Spenceville Cu mine in Nevada County, California, approximately 6800 m³ of jarosite overburden and 28,000 m³ of hematite residue are potential sources of heavy metals loading to infiltrating surface waters. A column study was performed to assess the ability of the overburden and the residue to attenuate heavy metals from acidic mine drainage. The study information was needed as part of a remedial design for the abandoned mine, and was designed to simulate a worst-case scenario to examine the plausibility of backfilling a large open pit with the waste materials. Ten pore volumes of acidic mine drainage were allowed to pass through the materials, and the column effluents were analyzed for dissolved Fe, Al, Ca, Mg, Na, K, Mn, Cu, Zn, Pb and Ni using ICP-AES. The oxidation-reduction potential (Eh) was measured with a combination PtAg/AgCl electrode and also calculated from Fe(II) and Fe(III) measurements using the Nernst equation. Ion activities in solution and saturation index (SI) values for various solid phases were calculated using the geochemical speciation model MINTEQA2, and mineralogical compositions of fine (< 2 mm) and coarse ( > 2 mm) fractions were determined by XRD. Geochemical modeling of the column effluent compositions indicate that goethite, jarosite, jurbanite and gypsum are potential solid phases that may control metal solubilities in the column effluents. Excellent agreement was observed between the measured Eh values and those calculated from the activity ratio of Fe²⁺(aq) to Fe³⁺(aq). The large attenuation capacities for Cu and Zn exhibited by the jarosite overburden also suggest that solid solution substitution plays a large role in controlling metal concentrations in the pore waters. Relatively little metal attenuation, however, was provided by the hematite residue.     

Balance of S in a constructed wetland built to treat acid mine drainage, Idaho Springs, Colorado, U.S.A.

The wetland constructed at the Big Five Tunnel in Idaho Springs, Colorado was designed to remove, passively, heavy metals from acid mine drainage. In optimizing the design of such a wetland, an improved understanding of the chemical processes operating there was required, particularly SO₄²⁻ reduction and sulfide precipitation. For this purpose, field and laboratory data were collected to study the balance of S in the system. Field data collected included water analyses of the mine drainage and wetland effluents and measurements of H₂S gas emissions from the wetland. The concentration of sulfide in the wetland effluent ranged from 10⁻⁴ to 10⁻³ mol/l. The average rates of H₂S emission from the surface of the substrate were 150 nmol/cm²/d in the summer and 0.17 and 0.35 nmol/cm²/d in the winter. This maximum estimated loss of sulfide was not significant in reducing the amount of sulfide available for precipitation with metals. Sequential extraction experiments for S on wetland substrates showed that acid volatile sulfides (AVS) increased with time in the wetland substrate. A serum bottle experiment was conducted to study the S balance in the Big Five wetland by quantitatively measuring the amount of S in different phases as microbial SO₄²⁻ reduction progressed. The increase in AVS reasonably balanced the decrease in SO₄²⁻ concentration in the experiment, suggesting that the decrease in SO₄²⁻ concentration represented the amount of SO₄²⁻ reduced and that nearly all of the sulfide produced was precipitated as AVS. Sulfide precipitation was determined to be the primary metal removal process in the wetland system and amorphous FeS is the primary iron sulfide formed in the substrate.     

Kinetics of selenomethionine disappearance from reclaimed coal mine soils of Wyoming, U.S.A.

 Selenomethionine (SeM) is an organic toxicant that is present in seleniferous environments. No kinetic data is yet available regarding SeM reactions in coal mine environments, where selenium (Se) toxicity is a potential concern. A kinetic study was conducted on two reclaimed coal mine soils (Typic Torriorthents) from Wyoming having sandy and clayey textures. Four levels of SeM treatments (0, 50, 100 μM, and plant amendment from the mine vegetation) were reacted with the soils for 4, 7, 14, 28, 42, 56, and 84 days to characterize the kinetic behavior of overall SeM disappearance from soil solutions. Detection of SeM in soil solutions at the control level (0 μM SeM) indicated occurrence of indigenous SeM in the soils. In the plant-amended soil solutions, much greater concentrations of SeM were observed as compared with the soil-only systems. This indicated the plant material was a more potential source of SeM than the mine soils. A time-dependent loss in solution SeM concentrations was observed for both soils under 0, 50, 100 μM SeM treatments. For the soil-plant mixtures, the solution SeM concentration increased initially, reached a maximum after 14 days, and then decreased thereafter. In the plant-amended soil solutions, SeM concentrations at all time intervals were higher for the sandy as compared to the clayey soil. At 50 and 100 μM SeM treatments, the solution pH was linearly related to the percentages of SeM disappeared from the solutions; greater percentage of SeM was removed from solutions at comparatively lower pH levels, which was ≥90% at pH 7.7 for both soils. Solution SeM concentrations decreased exponentially with time following first-order kinetic reactions. Under all applications (except for the control), C ₀ (SeM concentration at t=0) values for the sandy soil were greater than those determined for the clayey soil, indicating higher solution SeM availability for the former and more SeM retention by the latter at t=0. Comparison of C ₀ in controls (0 μM SeM addition) suggested greater indigenous SeM in the clayey soil. For both soils, C ₀ values under different treatments followed the order, (soil+100 μM)>(soil+50 μM)>(soil+0 μM). The specific reaction rate constants (K _r) of SeM for both soils were similar (0.031 and 0.029 day^–1 for sandy and clayey soils, respectively); low K _r values indicated that SeM loss from our reclaimed coal mine soil solutions would follow rather slow kinetics. The half-life (t _0.5) of SeM varied from 15 to 55 days depending on treatment level. The knowledge obtained from this study should contribute in developing time-based Se reclamation strategies in coal mine environments. Received: 18 September 1995 · Accepted: 28 December 1995     

Hydrogeochemical characteristics of acid mine drainage in the vicinity of an abandoned mine, Daduk Creek, Korea

Acid mine drainage discharged from the abandoned Daduk mine towards the Daduk creek has a pH of 3.3, and concentrations of Al, Mn, Fe, Zn and SO₄ of 18, 41, 45, 38 and 1940 mg/L, respectively. In particular, As concentration in acid mine drainage is 1000 μg/L. Removing order of metal ions normalized by SO₄ concentration downstream from discharge point is Fe > As > Al > Cu > Zn > Mn > Cd > Pb. In the Daduk creek, Fe and As are the most rapidly depleted downstream from acid mine drainage because As adsorbs, coprecipitates and forms compounds with ferric oxyhydroxide. From the results of geochemical modeling using the Phreeq C program, goethite (FeOOH) is oversaturated, and schwertmannite (Fe₈O₈(OH)_4.5(SO₄)_1.75) is the most stable solid phase at low pH in the Daduk creek. Yellowish red (orange ochre) precipitates that occurred in the study area are probably composed of goethite or schwertmannite.