Geochemistry of ochreous precipitates from coal mine drainage in India

The deposition of ochreous is common by a consequence of acid mine drainage (AMD). The ochreous precipitated from the AMD sites around Tertiary coalfield of Assam, India were collected and characterized by X-ray diffractometry (XRD), Fe to S molar ratio, ammonium oxalate acid (pH 3.0) extraction, fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The ochreous mainly consists of goethite, schwertmannite, ferrihydrite and jarosite. Mineralogy of ochreous was controlled by the pH whereas formation of ferrihydrite was favored at high organic carbon content. Role of bacteria for the formation of secondary minerals was observed. Mobility of metals was controlled by the ochreous, and they were also retained during the process of phase transformation of poorly ordered iron-oxyhydroxysulfates into the stable forms.     

Seasonal variations in the composition of mine drainage-contaminated groundwater in Dalarna, Sweden

Groundwater down-gradient from a mine rock dump in Dalarna, Sweden was sampled from the onset of snowmelt runoff (April) until October in order to investigate seasonal variations in groundwater composition. The results demonstrate that considerable variation in solute concentration (Al, Cu, Fe, SO₄²⁻, Zn) and acidity occurs in groundwater; the greatest change in solute concentrations occurs during the melting of the snow cover, when sulfide oxidation products are flushed from the rock dump. During this period, groundwater flow is concentrated near the soil surface with an estimated velocity of 1 m/day. Groundwater acidity varied by a factor of four closest to the rock dump during the sampling period, but these variations were attenuated with distance from the rock dump. Over a distance of 145 m, groundwater pH increases from 2.5 to 4.0 and acidity decreases from 3–13 to 0.8–1.1 meq/L, which is the combined effect of ferric iron precipitation and aluminosilicate weathering. As a result of flushing from the upper soil horizons, peaks in total organic carbon and ammonium concentrations in groundwater are observed at the end of snowmelt. In soils impacted by acidic surface runoff, the sequential extraction of C horizon soils indicates the accumulation of Cu in well-crystallized iron oxyhydroxides in the upper C horizon, while Cu, Fe, Ni and Zn accumulate in a well-crystallized iron oxyhydroxide hardpan that has formed 2.5m below the ground surface. Surface complexation modeling demonstrates that SO₄²⁻ and Cu adsorb to the abundant iron oxyhydroxides at pH < 4, while Zn adsorption in this pH range is minimal.     

Seasonal variations of zinc in a eutrophic lake

Depth profiles of dissolved zinc were measured monthly over one year in Lake Greifen, a eutrophic lake. The concentrations are in the range 10–40 nM and show systematic variations over time and depth. Due to the increased binding to particles and subsequent settling, concentrations of zinc in the epilimnion decrease during summer stagnation. Clear correlations between Zn and major nutrients (P, Si) are, however, not observed in the water column. No accumulation of Zn occurs in the anoxic hypolimnion. The Zn sedimentation is related to the sedimentation of algae and of manganese oxide. A mass-balance calculation shows that 87% of the Zn input is retained in the sediments of Lake Greifen.     

Chemistry and mineralogy of ochreous sediments in a constructed mine drainage wetland

The objective of this study was to examine the mineralogy and geochemical stability of ochreous sediments accumulated in a compost wetland constructed in 1990 for acid mine drainage treatment. Intact sediment cores were collected in 1996 and 2000 from an area that had accumulated 33 cm of ochre. Solids and pore waters were subsequently separated by centrifugation and analyzed using conventional methods, including X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and wet chemical techniques. The solid phase had an average Fe content of 585 g/kg and was predominantly schwertmannite [Fe ₈O₈(OH)_4.8(SO₄)_1.6] in the upper portion of the sediment column, but transformed to goethite (α-FeOOH) with depth. The rate of transformation was calculated to be 30 mol/m³/yr in the initial 6 yr of sedimentation as compared to 10 mol/m³/yr for the 4-yr period from 1996 to 2000. Pore water composition was affected by this mineral transformation through production of acidity and the release of Fe and SO₄. These results demonstrate that the sediment column was not a static environment. In addition, the transformation of schwertmannite to goethite, which has been observed under laboratory conditions, also occurs in natural systems.     

Seasonal variations of microbial sulfate and iron reduction in alkaline Pb–Zn mine tailings (Ontario, Canada)

Several studies have shown that SO₄-reducing bacteria (SRB) are active in acidic sulfide-rich mine tailings and sediments impacted by mining activities. SRB activity in acidic tailings has been shown to vary with seasons as a result of fluctuating in situ physico-chemical conditions. Iron-reducing bacteria (FeRB) also play an important role in Fe cycling in sediments impacted by mining activities, but their activity in mine tailings is poorly understood, despite the fact that geochemical evidence indicates that they might be active. The present study was undertaken to assess the seasonal changes in SRB and FeRB abundance and activity in alkaline Pb–Zn mine tailings (Calumet tailings) located near Ottawa, ON, Canada. Results showed that FeRB and SRB populations were present throughout the year at two different sampling sites at the Calumet tailings, but SO₄ reduction rates (SRR) were lower in the spring than in the summer, indicating that SRB activity was affected by organic C availability and/or temperature. Surface agricultural runoff at one site provided ample nutrients and organic C to the tailings, but SRB activity remained lower than the site not impacted by nutrient runoff, suggesting that the type of organic C was different between the two sites and that less labile organic substrates were available to SRB in the organic-rich site. High SRB activity in the site containing low organic C inhibited the abundance of FeRB, and possibly their activity, as a result of abiotic reduction of Fe(III)-rich minerals by biogenic sulfides, which lowered the pool of final electron acceptors. The abiotic reduction pathway was consistent with the porewater data which showed that sulfide was consumed and SO₄ produced, along with Fe(II). These results show a strong interdependence between SRB and FeRB activity, as observed in other environments, such as saltmarsh sediments. Low temperature did not appear to hinder FeRB abundance in alkaline tailings. Finally, despite evidence that SRB populations were active at both sites, the |S isotopic composition of the AVS and CRS fractions were not representative of biogenic sulfides, indicating that the overall S-isotope signature of mine tailings is more representative of abiotic sulfides originating from the ore body.     

Characterization of manganese oxide precipitates from Appalachian coal mine drainage treatment systems

The removal of Mn(II) from coal mine drainage (CMD) by chemical addition/active treatment can significantly increase treatment costs. Passive treatment for Mn removal involves promotion of biological oxidative precipitation of manganese oxides (MnO_x). Manganese(II) removal was studied in three passive treatment systems in western Pennsylvania that differed based on their influent Mn(II) concentrations (20–150 mg/L), system construction (±inoculation with patented Mn(II)-oxidizing bacteria), and bed materials (limestone vs. sandstone). Manganese(II) removal occurred at pH values as low as 5.0 and temperatures as low as 2 °C, but was enhanced at circumneutral pH and warmer temperatures. Trace metals such as Zn, Ni and Co were removed effectively, in most cases preferentially, into the MnO_x precipitates. Based on synchrotron radiation X-ray diffraction and Mn K-edge extended X-ray absorption fine structure spectroscopy, the predominant Mn oxides at all sites were poorly crystalline hexagonal birnessite, triclinic birnessite and todorokite. The surface morphology of the MnO_x precipitates from all sites was coarse and “sponge-like” composed of nm-sized lathes and thin sheets. Based on scanning electron microscopy (SEM), MnO_x precipitates were found in close proximity to both prokaryotic and eukaryotic organisms. The greatest removal efficiency of Mn(II) occurred at the one site with a higher pH in the bed and a higher influent total organic C (TOC) concentration (provided by an upstream wetland). Biological oxidation of Mn(II) driven by heterotrophic activity was most likely the predominant Mn removal mechanism in these systems. Influent water chemistry and Mn(II) oxidation kinetics affected the relative distribution of MnO_x mineral assemblages in CMD treatment systems.     

Effects on nutrient regime in two recipients of nitrogen-rich mine effluents in northern Sweden

The question of the limiting nutrient(s) for production of phytoplankton and macrophytes was explored in two contrasting freshwater systems receiving N- and P-rich mine effluents from the Boliden and Kiruna mine sites, northern Sweden. For both sites, total N (TN), total P (TP) and TN:TP mass ratios in water, sediment and macrophytes were used to examine (1) spatial variations within the systems, (2) differences between the systems and (3) seasonal variations. The TN concentration from the discharge point at the Kiruna site was about seven times higher than at the Boliden discharge point, while the TP concentration was 10 times lower than in the discharge point at the Boliden site. The majority of the studied lakes showed elevated biomass of phytoplankton, with maximum values found in Lake Bruträsket (Boliden). Mining activities have affected the nutrient regime of the two recipients by contributing to elevated TN and TP concentrations and TN:TP mass ratios as well as elevated production of phytoplankton and macrophytes compared to the reference sites. Depending on the NH₄ concentration in the effluent at the Boliden site, water column TN:TP mass ratios shifted from being >22, indicating P-deficiency, to between 9 and 22, indicating a transition from N- to P-deficiency (co-limitation). However, water column TN:TP mass ratios at the Kiruna site always indicated P-deficiency, while TN:TP mass ratios of macrophytes indicate that both sites may vary from N- to P-limitation. The study suggests that for the design of efficient monitoring programmes and remediation measures, it is important to consider the major N and P species in water, phytoplankton, sediment and macrophytes.     

Assessing mine drainage pH from the color and spectral reflectance of chemical precipitates

The pH of mine impacted waters was estimated from the spectral reflectance of resident sediments composed mostly of chemical precipitates. Mine drainage sediments were collected from sites in the Anthracite Region of eastern Pennsylvania, representing acid to near neutral pH. Sediments occurring in acidic waters contained primarily schwertmannite and goethite while near neutral waters produced ferrihydrite. The minerals comprising the sediments occurring at each pH mode were spectrally separable. Spectral angle difference mapping was used to correlate sediment color with stream water pH (r²=0.76). Band-center and band-depth analysis of spectral absorption features were also used to discriminate ferrihydrite and goethite and/or schwertmannite by analyzing the ⁴T₁←⁶A₁ crystal field transition (900–1000 nm). The presence of these minerals accurately predicted stream water pH (r²=0.87) and provided a qualitative estimate of dissolved SO₄ concentrations. Spectral analysis results were used to analyze airborne digital multispectral video (DMSV) imagery for several sites in the region. The high spatial resolution of the DMSV sensor allowed for precise mapping of the mine drainage sediments. The results from this study indicate that airborne and space-borne imaging spectrometers may be used to accurately classify streams impacted by acid vs. neutral-to-alkaline mine drainage after appropriate spectral libraries are developed.     

Seasonal and interannual variations in pigments in the Adriatic Sea

Spatial and temporal variability of pigments was studied from the CZCS satellite data and fromin situ chlorophyll and transparency for the period 1979-1985. The three Adriatic sites, Northern, Middle, and Southern Adriatic are differently influenced by meteorological, hydrological and oceanographic parameters. The differences between seasonalin situ chlorophyll and remotely sensed pigment concentrations (from CZCS satellite data) from the Adriatic are large in winter. Through the correlation analysis, pigments were compared to meteo-oceanographic and hydrological parameters from different Adriatic sites. The PCA (principal component analysis) was applied to the pigment data series and significant components were compared. Different correlations are obtained for warm and cold periods of the year pointing to seasonal differences in the underlying mechanism of pigment variability. The first PC is influenced mainly by temperature. In the warm period more parameters seem to influence the pigment field, than in the cold period. The pigments in the Adriatic are in good correlation to a number of hydrologic and meteo-oceanographic factors.     

Bioremediation of sulphate rich mine effluents using grass cuttings and rumen fluid microorganisms

Acid Mine Drainage (AMD) needs to be treated before it can be re-used or discharged in receiving water bodies due to the low pH, high salinity and high sulphate concentrations of the water. Several treatment methods are currently applied including chemical treatment (e.g. neutralisation of the low pH waters), physical treatment (e.g. reverse osmosis) and biological treatment to reduce the high sulphate concentration. When treating AMD biologically, sulphate reducing bacteria (SRB) reduce sulphate to sulphide, provided that a suitable and cost effective carbon and energy source is present. In the present study mine water was remediated biologically, using the degradation products of grass-cellulose, as carbon and energy sources for the sulphate reducing bacteria. A laboratory scale one stage anaerobic bioreactor (20 L volume) containing grass cuttings and biomass consisting of rumen fluid microorganisms and immobilized SRB, was initially fed with synthetic sulphate rich water and later with diluted AMD. The results indicated an average of 86% sulphate removal efficiency when feeding synthetic sulphate rich feed water to the reactor. When feeding diluted AMD, the highest sulphate removal efficiency was 78%. The sulphate removal was dependant on Chemical Oxygen Demand (COD) concentrations in the reactor. Increased COD concentrations were obtained when fresh grass was added to the reactor on a regular basis. Metal removal, especially iron, was observed due to the metal sulphide precipitates formed during biological sulphate removal.     

Mineralogical and geochemical characterization of precipitates on stream receiving acid mine water, Korea

Seasonal variations of water chemistry occurred in acid mine drainage receiving mine and leachate water. Sulfate and metal concentrations were low in winter but high in spring and summer. Mine waters were highly acidic (up to pH 3.4) in nature with high concentrations of manganese, copper and zinc but high electrical conductivity and sulfate in leachate. The blue and brownish yellow precipitates were formed under different chemical environments of acid mine drainage. Brownish yellow (Munsell color 7.5YR 8/12), blue (Munsell color 2.5B 9/7) and light blue (Munsell color 2.5B 9/3) precipitates deposited on the stream bottom receiving acid mine water. The brownish yellow precipitates formed in the acid mine water, whereas the blue and light blue precipitates formed in the leachate water. The brownish yellow precipitates consisted mainly of ferrihydrite, whereas the blue and light blue precipitates consisted of glaucocerinite and/or woodwardite.     

Characterization of suspended solids in a stream receiving acid mine effluents,Bersbo, Sweden

Suspended particulate matter was recovered by filtration (0.40 μm) of water from a stream receiving acidic effluents from a mine tailings deposit. This solid phase formed rapidly as pH increased from 3.5 at the release point to 6.5, approximately 2 km downstream. The suspended solid was present in concentrations that ranged from 10–20 mg/l for anoxic conditions (winter) to 30–120 mg/l for oxic conditions (early spring). The solid consisted of FeOOH + Fe(OH)₃(am) and AlOOH + Al(OH)₃(am), as well as silicates. The organic content (of natural origin) was up to 30% (dry wt). Most of the Fe and Al from the leachate was precipitated in the particulate phase, approximately 98% of total metal content in the aqueous phase, as well as ∼50% of Mn, Cu, Zn, Cd and Pb. These elements were predominantly adsorbed on the hydrous oxide precipitate, or to some extent (Mn and Pb) coprecipitated, as indicated from a sequential leaching procedure and powder X-ray diffractometry. All the elements, particularly Cu, were to a significant degree associated with organic matter.     

Seasonal variations in chlorophyll and nutrients in a Canadian arctic estuary

The Eskimo Lakes and Liverpool Bay constitute a series of estuarine waters to the Beaufort Sea in arctic Canada. Salinity ranges in summer from 20‰ at the mouth to less than 1‰ at the head of the system. Arctic features include an ice cover lasting for about 8 months annually and water temperatures which fluctuate from ?1°C in winter to as high as 12°C in late summer. Subsurface light is severely attenuated. Reactive phosphate varies from a spring high of 0.3 μg-at P per 1 to undetectable levels during summer. Nitrate is more abundant, and silicate is consistently plentiful. Chlorophyll a reaches a maximum only occasionally higher than 3 mg per m³ in June and July, rising from undetectable levels in winter. Photosynthetic rates are low by all standards, and have not been measured at greater than 6.4 mg C per m² per hour in summer. Low levels of subsurface light and reactive phosphate and nitrate characterize this exceptionally oligotrophic arctic estuary.     

Spatial variations and controls of acid mine drainage generation

Spatial variations of historical and ongoing pyrite oxidation rates were quantified near the Nanisivik Mine on Baffin Island in northern Canada. The variations observed depend mainly on the degree of water saturation, pH and temporal trends in mineral reactivity. Maximum oxidation rates were observed in an untreated tailings spill, while minimum oxidation rates were noted for tailings deposited under water. Spatial trends in oxidation rates were in the order of three orders of magnitude. Spatial trends were only possible to quantify by a combination of closed chambers (well-drained conditions) and micro sensors (water-covered conditions). Oxygen uptake rates in tailings at various ages (up to 7 years) indicate a decrease by more than a factor of 3 over time. Total oxygen uptake over 7 years was calculated and found to be in a fair agreement with the overall pyrite depletion evaluated as high-resolution mineral mass balance (by quantitative powder X-ray diffraction).     

Seasonal residence and counterurbanization: the role of second homes in population redistribution in Finland

Since the late twentieth century, many developed countries have experienced population deconcentration, labelled as counterurbanization. There has been an academic discussion on the meaning, validity and universality of this concept, drivers of counterurbanization and its impacts on rural areas. To date, research on counterurbanization mostly apply static and discrete definitions of residence, migration and population, which is an increasingly simplistic view in the contemporary reality of a growing multitude of forms of mobility, often related to dual residence. Particularly large-scale quantitative studies on counterurbanization are confined by existing statistical practices. This paper attempts to overcome this obstacle and describe the transformation of the settlement system in Finland acknowledging the role of second home mobility. To achieve this goal, it introduces two alternative measures of population, seasonal and average population, and analyses their spatial dynamics between the years 1990 and 2010 based on georeferenced grid statistical data. The study finds that although registered population has been concentrating during the period in analysis, seasonal population has been increasingly dispersed due to the growing number of second homes. It shows that the counterurbanization process, though not noticed by conventional statistics, does occur in Finland, manifested by seasonal rather than permanent moves. The article concludes that various forms of mobility should be taken into account when analysing the urban–rural population dynamics and transformations of settlement systems as well as in rural development planning.     

Seasonal variations in sediment sulfur cycling in the Ballastplaat mudflat, Belgium

Sulfate reduction rate (SRR) and pools of reduced inorganic sulfur, acid volatile sulfide (AVS), chromium reducible sulfur (CRS), and elemental sulfur (S^o), were studied from June 1990 till March 1992 at two locations on the Ballastplaat mudflat in the Scheldt estuary. The sediment composition at station A was mainly sand with low organic content whereas sediments at station B were dominated by silt and clay with high organic content. SRR was positively related to temperature; more pronounced at station B (Ea=190 kJ mol⁻¹) than at station A (Ea=110 kJ mol⁻¹). The maximum SRR values observed equalled 14 μmol cm⁻³ d⁻¹ at station B and 1 μmol cm⁻³ d⁻¹ at station A. AVS was the dominant radiolabelled end product of the sulfate reduction reaction, except in surface sediments where pyrite and S^o were more dominant. However, CRS was the predominant reduced inorganic sulfur pool in the sediments. Both AVS and CRS pools showed temporal variations out of phase with SRR. SRR peaked in summer, while the concentrations of AVS and CRS were highest in fall. The accumulation of AVS and CRS started late summer after depletion of oxidants, which had accumulated during winter and spring. The estimated annual SRR and thus sulfide production in the upper 15 cm of station B was of the order of 100 mol m⁻² yr⁻¹, and at station A of the order of 12 mol m⁻² yr⁻¹. The sulfur mass balance shows that only a very small fraction, if any, of the produced sulfide is retained as reduced inorganic sulfur in the sediment.     

Seasonal variations and mechanisms of groundwater nitrate pollution in the Gaza Strip

Nitrate represents one of the major pollutants of groundwater in the Gaza Strip. Several cases of blue babies disease were reported in the last couple of years. The present study is an investigation of the seasonal variations in nitrate concentration to better understand the mechanisms and parameters controlling this perilous pollutant. Nitrate was analysed in 100 wells (47 agricultural and 53 domestic) in five governorates. The results showed that 90% of the tested wells have nitrate far beyond the allowed values set by the World Health Organization (WHO). The average concentration of nitrate in domestic wells is 128 mg/L in June-July and 118 mg/L in Jan-Feb, and for the agricultural wells, the average is 100 mg/L in June-July, and 96 mg/L for Jan-Feb. The results suggest that the seasonal differences in nitrate concentrations of the domestic wells are slightly more observable than those of the agricultural wells. The environmental factors that control nitrate in groundwater are: a partially-confined aquifer, lack of a sewage system, population density, the presence of refugee camps, the presence of fertilizers and the annual rain. The variations in nitrate concentration of the domestic wells are not of considerable values. It is suggested that concrete policies in pollution control and/or prevention measures could be formulated upon better understanding of the environmental factors.     

Seasonal variations of phosphorus species in sediment from the middle Adriatic Sea

Phosphorus (P) species concentrations in 0–2 cm surface sediment layer were investigated monthly from November 2001 to December 2002 at the bay, channel and open sea stations in the middle Adriatic. Modified SEDEX method was used for inorganic phosphorus species determination [P in biogenic (P-FD), authigenic (P-AUT), detrital apatite (P-DET) and P adsorbed on to iron oxides and hydroxides (P–Fe)], and organic phosphorus (P-ORG). P-FD, P-AUT and P-DET concentration ranges (1.5–5.4, 0–2.7 and 0.4–3.4 μmol g⁻¹, respectively) were similar at all stations, and showed no obvious common trend of seasonal changes. P–Fe ranged from 1.9 to 11.9 μmol g⁻¹ with the highest values at bay station and higher seasonal oscillations than other inorganic P forms. P-ORG ranged from 0.3 to 18.7 μmol g⁻¹ with higher concentrations at stations of fine-sized sediments and showed increased concentrations in warm part of the year at all stations. Correlation between concentrations of P–Fe in the surface sediment layer and orthophosphate sediment-water interface concentration gradients at bay and channel stations indicated to P–Fe importance in the orthophosphate benthic flux. For the bay station, linkage between sediment P-ORG and chlorophyll a concentrations, primary production and microzooplankton abundance was established, indicating a 1 month delay of sediment response to production fluctuations in the water column.     

胶州湾东北部营养盐的季节和多年变化

根据1991-2004年的调查资料,探讨了胶州湾东北部水域营养盐及其摩尔比的月、旬的变化和多年变化以及与年、Chla的关系.月和旬的变化表明春、夏季,各种营养盐浓度以锯齿状的形式呈缓慢上升趋势,与外源性营养盐增加密切相关,只有SiO₃-Si在8月份出现明显峰值,SiO₃-Si/DIN和SiO₃-Si/PO₄-P比也有相似的变化;秋季以后营养盐浓度急剧增加,特别是SiO₃-Si和DIN,导致了冬季赤潮的爆发.在赤潮高峰时,营养盐大量消耗,特别是SiO₃-Si几乎耗尽(0.49μmol/L),SiO₃-Si/DIN和SiO₃-Si/PO₄-P比迅速下降(分别为0.01和1.04),SiO₃-Si成为浮游植物生长的限制因子,控制了赤潮的进一发展,并初步讨论了赤潮发生的化学海洋学机制.营养盐的季节变化与Chla含量呈明显的消长关系.营养盐及其结构的多年变化表明,1999年以后比1991-1998年DIN和SiO₃-Si的平均浓度分别增加了1.0和2.2倍,DIN/PO₄-P比和SiO₃-Si/PO₄-P比分别增加了0.4和0.9倍,PO₄-P、SiO₃-Si/DIN比略有增加,营养盐之间的摩尔比都偏离了Redfield比,这与青岛市社会经济发展密切相关.