Reclaimed Mine Soils Research Articles

Soil quality index as a tool for Scots pine (Pinus sylvestris) monoculture conversion planning on afforested, reclaimed mine land

In Central Europe, a large portion of post-mining sites were afforested with Scots pine, which is characterized by good adaptability and a tolerance for poor habitat at the beginning of forest ecosystem development. Conversion of monoculture on mine sites into more biodiverse mixed hardwood forests, especially on more fertile deposits, can be an emerging need in this part of Europe in next decades. The ability to classify the forests at these post-mining sites will facilitate proper species selection as well as the management and formation of the developed ecosystem’s stability. This work describes the guidelines that can be followed to assess reclaimed mine soil (RMS) quality, using the mine soil quality index (MSQI) and a classification of developed forest sites as a basis of tree-stand species selection and conversion of pine monocultures. The research was conducted on four post-mining facilities (lignite, hard coal, sulphur, and sand pit mining areas) on different RMS substrates dominant in Central Europe. Soil quality assessment takes into account the following features of the soil: texture soil nutrients (Ca, Mg, K, Na, P); acidity (pH KCl); and Corg-to-Nt ratio in the initial organic horizon. An analysis was conducted of classification systems using the MSQI validation correlation (at p =0.05) with vegetation features affected by succession: aboveground biomass of forest floor and ecological indicators of vascular plants (calculated on the basis of Ellenberg’s (2009) system). Eventually, in the analysed data set, the MSQI ranged from 0.270 for soils on quaternary sands to 0.720 for a mix of quaternary loamy sands with neogene clays. Potential forest habitat types and the role of the pine in the next generation of tree stands on different RMS parent rock substrate were proposed.

Near infrared spectroscopy—A tool for chemical properties and organic matter assessment of afforested mine soils

The objectives of this study were to assess chemical and microbial properties of different post-mining barrens afforested with Scots pine (Pinus sylvestris) and to evaluate the potential of near infrared spectroscopy (NIRS) to predict these properties in the reclaimed soils. The samples were collected from four sites at different substrates and measured for the contents of organic C (Corg), total N (Nt), Corg-to-Nt ratio, dehydrogenase activity, contents of humified C, humic acid C and fulvic acid C, cation exchange capacity, exchangeable acidity, total exchangeable bases (TEB) and base saturation. The spectra of samples were recorded between 400 and 2500nm. A modified partial least squares method with cross-validation was used to develop calibration models for prediction of chemical and microbial properties of the samples from their spectra. There were significant differences in the contents of Corg, Nt, dehydrogenase activity, pH and sorption properties between the mine soils. The samples from the studied sites had different spectral characteristics suggesting differences in chemical composition of their organic matter. “Excellent” predictive models (coefficient of correlation between the predicted and reference values ≥0.90) based on NIR spectra were developed for Nt, Corg-to-Nt ratio, humified C, humic acid C and exchangeable acidity. For other soil properties (except the TEB), “satisfactory” (r=0.80–0.90) models useful for fast screening were developed. The results indicate the potential of NIRS to predict several properties of the reclaimed mine soils.

A soil quality index for reclaimed mine soils

The quality of soils found in mines is low if they do not receive any reclamation treatment; yet, to the authors’ knowledge, there are still no equations to evaluate the quality of metal-contaminated mine soils after the application of the most widely used reclamation treatments (planting vegetation and amending with wastes). Therefore, the purposes of the present study were 1) to propose a method for developing soil quality indexes (SQIs); 2) to develop the SQIs for 2 types of mine soils (settling pond and mine tailing) reclaimed by planting trees, amending with wastes, or both; and 3) to assess the quality of these soils under field conditions. The results obtained after the use of an SQI developed for reclaimed mine soils through the selection of an SQI with a factor analysis and the totaling of the scores of the selected variables revealed that this method is a valid tool for developing SQIs. Applying this index with reclaimed mine soils showed that the untreated sites had a very low quality and that the treatment that most improved the soils was amending with wastes (sewage sludges and paper mill residues). The authors recommend the periodic addition of sewage sludges and paper mill residues to degraded sites as they increase the quality of soils, but the effects decrease over time.

The Change Law of RMSs Characteristics in Grassland Opencast Coal Mine Dump of China

With construction and development of opencast coal mine, its damage to the land resources and ecological environment in mine area become increasingly serious. Thus, assessing change law of reclaimed mine soils is essential for land reclamation and ecological restoration in ecological fragile area. Is this study, soil Bulk Density, Organic matter, Available P, Available K, Alkali-hydrolyzed N, Total N, pH value, Electrical Conductivity was analyzed in different sampling sites with different reclamation age and an unmined site as a reference in Inner Mongolia mining waste dump. The soil Organic matter, Available P, Available K, Alkali-hydrolyzed N and Total N increased with reclamation age, all the soil factors gradually arrived at their content in original landform. A model of RMSs characteristics was constructed using index sum method. RMSs characteristics had been improved in study area, and gradually arrived at the original landform level.

Use of Reclaimed Mine Soil Index (RMSI) for screening of tree species for reclamation of coal mine degraded land

In India forest tree species are commonly used for reclamation of coal mine degraded land, thus selection of appropriate species is essential. Degree of amelioration of rhizosphere mine soil quality by different tree species provides an important guideline for screening of suitable species. Rhizosphere soil samples collected from six common tree species growing in the reclaimed coal mine overburden dumps of Jharia coalfield, Dhanbad, India, were analysed for physico-chemical and biological properties. Principal component analysis (PCA) was employed to derive a Reclaimed Mine Soil Index (RMSI) which was used for ranking of suitability of the species. By using PCA it was found that soil CO2 flux, dehydrogenase activity, organic carbon, soil coarse fraction and moisture content are the most critical properties controlling health of reclaimed coal mine soil. The observed values of the above properties were converted into a unitless score (0–1.00) and the scores were integrated into RMSI. The RMSI values were validated by regression analysis with the plant growth parameters (aerial height, diameter at breast height and canopy cover) for each species. Among the different species growing on the overburden dump, the canopy cover and height was more for Cassia siamea whereas, the diameter was higher for Dalbergia sissoo. Tree species having higher RMSI values could be recommended for reclamation of degraded lands, and could be grouped as: high RMSI (>0.500) – Cassia siamea and Dalbergia sissoo, moderate RMSI: (0.300–0.499) – Leucanea leucocephala, Acacia auriculiformis and Gmelina arborea; and low RMSI (<0.300) – Terminalia arjuna. Based on RMSI it is suggested that C. siamea and D. sissoo are most suitable. Thus tree species growing on reclaimed areas had diverse effects on their respective rhizosphere soil properties, which could directly or indirectly determine the growth and survival of the tree species.

Scots pine needles macronutrient (N, P, K, CA, MG, and S) supply at different reclaimed mine soil substrates—as an indicator of the stability of developed forest ecosystems

A main objective of restoration and afforestation at post-mining sites is establishing a long-term sustainable ecosystem which depends on adaptations of tree species and which in turn depends on the soil nutrient flux. The nutrient concentration (nitrogen (N), P, K, Ca, Mg, and sulfur (S)) of Scots pine needles was investigated in reclaimed mine soils (RMS) located at the following post-mining sites: a sand mine pit, spoil heap from a lignite mine, spoil heap from a S mine, and a carbonaceous spoil heap from an underground coal mine. The control plots were arranged on natural forest sites adjacent to the post-mining sites. A higher level of foliar nutrients was noted in the carbonaceous RMS, while lower levels were found in RMS on the spoil heap following lignite mining. The characteristics of the substrate were found to exert greater effect than mineral fertilization (performed at the onset of reclamation) on the tree stand characteristics, needle length and foliar nutrient concentration. While the soils and trees were most deficient in N, negative symptoms have not been noted to this date in tree stands at reclaimed mine sites. Trophic ratings were recommended based on statistical correlations and groupings between N and P contents in needles and needles length (mean length of 300 needles) while nutrient ratings were recommended from statistical differences and groupings of the RMS substrates.

Effectivity of arbuscular mycorrhizal fungi collected from reclaimed mine soil and tallgrass prairie

We examined suitability of arbuscular mycorrhizal fungi (AMF) associated with cool-season nonnative forages on reclaimed surface-mined land in southeast Ohio for establishment of native warm-season grasses. The goal of establishing these grasses is to diversify a post-reclamation landscape that is incapable of supporting native forest species. A 16-week glasshouse study compared AMF from a 30-year reclaimed mine soil (WL) with AMF from native Ohio tallgrass prairie soil (CL). Four native grasses were examined from seedling through 16 weeks of growth. Comparisons were made between CL and WL AMF on colonized (+AMF) and non-colonized plants (–AMF) at three levels of soil phosphorus (P). Leaves were counted at 4 week intervals. Shoot and root biomass and percent AMF root colonization were measured at termination. We found no difference between WL and CL AMF. Added soil P did not reduce AMF colonization, but did reduce AMF efficacy. Big bluestem (Andropogon gerardii Vitman), Indiangrass (Sorghastrum nutans (L.) Nash), and tall dropseed (Sporobolus asper (Michx.) Kunth) benefited from AMF only at low soil P while slender wheatgrass (Elymus trachycaulus (Link) Gould ex Shinners) exhibited no benefit. Establishment of tallgrass prairie dominants big blue-stem and Indiangrass would be supported by the mine soil AMF. It appears that the non-native forage species have supported AMF equally functional as AMF from a regionally native tallgrass prairie. Tall dropseed and slender wheatgrass were found to be less dependent on AMF than big bluestem or Indiangrass and thus would be useful in areas with little or no AMF inoculum.

Soil compaction and arbuscular mycorrhizae affect seedling growth of three grasses

Soil compaction is a limitation to establishment of native forest species on reclaimed surfacemined lands in Appalachia. Previously, non-native forage species such as tall fescue (Schedonorus arundinaceus(Schreb.) Dumort., nom. cons.) have been planted because they easily established on reclaimed mine soil. There is now interest in establishing robust native prairie species to enhance biodiversity and provide greater potential for root activity in the compacted soil. We conducted a 10-week glasshouse study comparing growth of “Pete” eastern gamagrass (Tripsacum dactyloidesL.), “Bison” big bluestem (Andropogon gerardiiVitman), and “Jesup MaxQ” tall fescue at soil bulk densities (BD) of 1.0, 1.3, and 1.5 g·cm-3. We also examined effects of arbuscular-mycorrhizal fungi (AMF) on plant growthin relation to compaction. Sources of AMF were a reclaimed surface coal mine soil and a native tallgrass prairie soil. Shoot and root biomass of tall fescue and big bluestem were reduced at 1.5 BD while eastern gamagrass growth was not affected. Growth ofbig bluestem and eastern gamagrass was greaterwith AMF than without, butsimilar between AMF sources. Tall fescue growthwas not enhanced by AMF. Overall, tall fescue biomass was 3 times greater than eastern gamagrass and 6 times greater than big bluestem when comparing only AMF-colonized grasses. Eastern gamagrass and big bluestem are both slower to establish than tall fescue. Eastern gamagrass appears to be more tolerant of compaction, while big bluestem appears somewhat less tolerant.

Effects of AMF on soil enzyme activity and carbon sequestration capacity in reclaimed mine soil

A series of pot experiments and field trials were carried out to evaluate the effects of arbuscular mycorrhizal fungi (AMF) on activities of soil enzymes and carbon sequestration capacity in reclaimed mine soil. A complex substrate of coal gangue, fly ash and sludge was used as reclaimed mine soil, and ryegrass was planted with AMF inoculation to construct a plant-complex substrate-microbe ecological restoration system. The changes to the soil organic carbon (SOC), activities of soil enzymes and glomalin-related soil protein (GRSP) were measured and the effects of AMF on activities of soil enzymes and carbon sequestration capacity in reclaimed mine soil were analyzed. The results show that the contents of GRSP (total glomalin (TG) and easily extractable glomalin (EEG)), SOC and activities of enzymes increased, and the increments were higher in the AMF inoculation treated plant-complex substrate-microbe ecological restoration systems than those with no AMF inoculated treatments after 12months of ryegrass growth. TG, EEG and soil enzyme activity have a significant positive correlation, and the correlative coefficient was 0.427–0.573; SOC and TG, EEG have a significant positive correlation (p<0.01), indicating that AMF plays an important role in carbon sequestration of reclaimed mine soils.

Effect of European Black Alder Monocultures on The Characteristics of Reclaimed Mine Soil

The effect of European black alder (Alnus glutinosa L.) on the contents of carbon and nitrogen,exchangeable base cations, and plant available forms of phosphorus in the reclaimed mine soils formed bywaste deposition from opencast lignite mines was researched in central Serbia. It was concluded that thegreatest part of dead organic residues reaching the soil under European black alder monocultures was liable torapid decomposition into end products. This was the consequence of a narrow C/N ratio in the European blackalder litterfall which amounted on average to 12.77 in the study monocultures. Only a small part of organicresidues was transformed into humus. On that account, European black alder monocultures did not have amajor impact on the accumulation of organic carbon and total nitrogen in the soil. The content of carbon in thesurface layers accounted for 1.55-1.57%, and the content of nitrogen to 0.085-0.132%. Fast mineralisation oforganic matter, and thus also of the organic forms of nitrogen, resulted in the surplus of soil nitrates, whichwere liable to washing through the soil. Nitrate movement resulted in the soil leaching and the movement ofbase cations, primarily calcium, to the deeper layers of the solum. The total soil phosphorus content was low,and also the level of plant available forms. A significant portion of total phosphorus in the surface layers of thereclaimed mine soils was composed of its organic forms.

Plant Cover and Soil Biochemical Properties in a Mine Tailing Pond Five Years After Application of Marble Wastes and Organic Amendments

Tailing ponds pose environmental hazards, such as toxic metals which can contaminate the surroundings through wind and water erosions and leaching. Various chemical and biochemical properties, together with extractable and soluble metals were measured five years after reclamation of a polluted soil affected by former mining activities. This abandoned mine site contains large amounts of Fe-oxyhydroxides, sulphates, and heavy metals. As a consequence, soils remain bare and the soil organic matter content is low (< 3 g kg −1). Marble waste, pig manure and sewage sludge were applied in 2004. Plant cover and richness, and soil chemical, biochemical and biological parameters were analysed five years later. Results showed that all soil biochemical properties as well as vegetation cover and richness were higher in treated soils than in the untreated contaminated plots (control), although organic matter, pH values and extractable metals concentrations were similar among treatments. Soluble cadmium and zinc were lower in the amended plots than in control. As a general pattern, soil amended with pig manure showed higher values of most biochemical properties compared to sewage sludge application, while the doses did not have a great effect, being only significant for β-glucosidase, phosphodiesterase and arylsulfatase. Significant correlations were found between vegetation cover, richness and soil biochemical properties, suggesting a high interdependence between plant colonization and reactivation of biogeochemical cycles during five years. This study confirms the high effectiveness of an initial application of the amendments tested to initialize the recovery of ecosystems in bare mine soils under Mediterranean semiarid conditions. This research also shows the high sensitivity of certain biochemical properties in order to evaluate soil quality and reactivation of nutrients cycles in reclaimed mine soils.

Prairie Grass Establishment on Calcareous Reclaimed Mine Soil

Reclaimed Appalachian surface mined lands have difficulty in sustaining native deciduous forest communities. Establishing prairie communities could increase ecosystem function; however, a native model system does not exist. We evaluated establishment of 15 North American prairie grasses as monocultures on reclaimed mine soil in southeast Ohio in four randomized complete blocks planted May 2005 and 2006. Population density was assessed 30 d after planting (30 DAP) and in October of the planting year (YR1) and second year following planting (YR2) and expressed as percentage of viable seeds sown (PVSS). Canopy cover of nonnative species reestablishing in the plots was measured in 2007. Eastern gamagrass ( L.) population was >50 PVSS in all censuses. Western wheatgrass [ (Rydb.) A. Löve] was initially 7 PVSS at 30 DAP, but increased to 154 PVSS by YR2 from rhizomes spreading into gaps. Big bluestem ( Vitman) was 7 PVSS at 30 DAP and 4 PVSS at YR2. Blue grama [ (Willd. ex Kunth) Lag. ex Griffiths] and sideoats grama [ (Michx.) Torr.] did not survive past YR1. Gaps left from poor stand establishment were primarily recolonized by nonnative Kentucky bluegrass ( L.) in the 2005 planting and birdsfoot trefoil ( L.) in the 2006 planting, but was least in eastern gamagrass and tall dropseed [ (P. Beauv.) Kunth]. This research demonstrates the potential for increasing diversity and species richness on mine soil habitats with regionally native grasses that could increase functional quality through ecological resilience.

Near‐infrared spectroscopy for rapid estimation of microbial properties in reclaimed mine soils

AbstractSeveral chemical and microbial properties of mine soils need to be measured for comprehensive assessment of the reclamation success. The objective of this study was to evaluate the ability of NIR spectroscopy to predict organic C (Corg), total N (Nt), and several microbial properties of mine soils reclaimed for forestry. Soils samples (n = 154) were collected at two reclaimed areas in central and S Poland, and their spectra in the NIR region (including the visible range, 400–2500 nm) were recorded. A half of the samples was used to develop calibration equations, and another half was used for validation. The modified partial least squares regression was applied to build calibration equations using the whole spectrum (0 to 2nd derivative). The best predictions were obtained for Corg and Nt (ratio of standard deviation to standard error of prediction in the validation stage [RPD] = 3.4 and 4.1; the regressions coefficients [a] of linear regression [measured against predicted values] = 0.94 and 0.96; correlation coefficients [r] = 0.96 and 0.97, respectively). Very well predictive models applicable for quantitative measurements were obtained also for microbial biomass, basal respiration, and the activities of dehydrogenase and acid phosphatase (RPD = 2.3–2.5, a = 0.90–0.99, r = 0.90–0.92). Prediction of urease activity was slightly worse (RPD = 2.1, a = 0.88, r = 0.87) but sufficient for rough estimation. The obtained results indicated the ability of NIR spectroscopy to predict complex soil microbial properties. Therefore, application of this analytical method may improve the assessment of recovery of microbial functions in reclaimed post‐mining barrens.

Effect of combined application of microbial inoculum and fertilizer on white clover growth in reclaimed mine soil

采用盆栽试验研究了矿区复垦土壤菌剂与肥料的不同配施对白三叶草(<em>Trifolium repens</em> Linn)生长的影响。结果表明: 双接种VA 菌根真菌(<em>Glomus mossea</em>)和根瘤菌(<em>Rhizobium</em>)能显著提高白三叶草根瘤数、根瘤鲜重和固氮酶活性, 根瘤数在有机肥双接种与无机肥双接种处理之间差异不显著, 而根瘤鲜重和固氮酶活性差异显著; 肥料与各菌剂组合处理中, 有机肥双接种处理的白三叶草分枝数、干物质重最大; 在白三叶草生长40 d 和150 d 时, 双接种处理的叶片数均为各处理中最大值; 接种VA 菌根真菌、根瘤菌和双接种均可增加白三叶草根系的菌根侵染率和土壤孢子数, 总体表现为双接种处理＞接种VA 菌根真菌＞接种根瘤菌, 有机肥相应处理＞无机肥相应处理＞对照; 肥料与菌剂的配合施用可有效提高植物对土壤氮、磷、钾养分的吸收。在矿区复垦土壤上有机肥与VA 菌根真菌和根瘤菌菌剂配施能显著促进白三叶草的生长, 是提高矿区复垦土壤植被恢复中比较适宜的组合方式。

Land Use Effects on Sample Size Requirements for Soil Organic Carbon Stock Estimations

Soil organic carbon (SOC) stock (in metric tons of carbon per hectare) is calculated from SOC concentration (in grams per kilogram) and soil bulk density (ρb; in grams per cubic centimeter). Temporal changes in SOC stock are used to calculate terrestrial carbon sequestration rates used in global climate change models. The inherent variability in soil properties like SOC and ρb means that larger sample sizes may be needed to accurately determine SOC stocks. Our objective was to calculate the minimum sample size required to detect changes in ρb, SOC, and SOC stock for two land uses. Surface soils (0-5 cm) from two reclaimed mine soils and two managed hay fields in northern West Virginia were intensively sampled (60-74 samples each). Mean SOC and SOC stock values were larger in the hay fields (40 g/kg, 29 Mg ha−1) than in the mine soils (20 g/kg, 20 Mg ha−1), but ρb was larger in reclaimed mine soils (1.4 g cm−3) than in hay field soils (1.2 g cm−3). The ρb variance was larger in mine soils than that in hay field soils, but field variances for a given land use were similar (0.09 and 0.11 [g cm−3]2 in mine soils; 0.02 and 0.03 [g cm−3]2 in hay field soils). The variances in SOC concentration and SOC stock were not related to land use and were not similar within a land use. As a result, the minimum number of samples required to detect a change in ρb, SOC, and SOC stock was a site-specific property and cannot be assumed a priori.

Changes in physical and chemical properties of soil after surface mining and reclamation

Mining causes drastic disturbances in landscape and soil properties, and reclamation can restore soil quality over time. Thus, assessing changes in properties of reclaimed mine soils is essential to understanding the effects of the reclamation techniques. This study was aimed at quantifying the effects of mining and reclamation processes on physical and chemical properties of reclaimed soils for three dominant soil series in Ohio: Mahoning–Canfield–Rittman–Chili, Coshocton–Westmoreland–Berks, and Gilpin–Upshur–Lowell–Guernsey. Three newly reclaimed mine sites (< 1 year since reclamation) were identified from each of the three soil series. Three sampling locations were identified for each mine site. Each sampling location consisted of a paired, undisturbed reference site adjacent to the reclaimed mine sites (RMSs). Thus, there were 54 sampling locations distributed throughout eight counties in eastern Ohio. Composite and core samples were obtained from 0–15, 15–30, and 30–45 cm depths in 2008. Soil physical and chemical properties were measured and changes in properties of the RMSs in reference to the adjacent, undisturbed sites were quantified. The bulk density (BD) of the RMSs (1.11 to 1.69 Mg m − 3 ) significantly increased by up to 54% compared to that of the undisturbed sites (0.98 to 1.41 Mg m − 3 ) at the 0–15 cm depth but not at the lower depths. The BD of the RMS was also affected by soil series, a high BD in the Mahoning–Canfield–Rittman–Chili soil series. Mining and reclamation activities increased soil pH and electrical conductivity (EC), and decreased soil organic carbon (SOC) and nitrogen (N) pools. At the 0–15 cm depth, soil pH in RMSs (4.9 to 8.1) was 4 to 31% higher than that of the undisturbed sites (4.6 to 7.0). Likewise, EC in RMS (119 to 349 μS cm − 1 ) was > 200% higher than those for the undisturbed sites (43 to 154 μS cm − 1 ). In the 0–15 cm depth, SOC pools in RMSs (1.2 to 2.5 Mg ha − 1 ) declined by 52 to 83% of undisturbed sites (11 to 29 Mg ha − 1 ). Similarly, N pools in RMSs (1.2 to 2.5 Mg ha − 1 ) declined by 42 to 75% of undisturbed sites (3.1 to 5.1 Mg ha − 1 ). Clay content was positively correlated with SOC concentration in the RMSs but not in the undisturbed site. This trend indicates that a RMS high in clay content has a relatively high SOC sink capacity. The SOC, N, C:N ratio, and EC in the subsurface layer of RMSs were similar to those of the surface soil, although later received a topsoil cover. Such a trend suggests that topsoil materials require better handling during removal, storage, and application so as to preserve soil structure, nutrients, SOC, and N pools.

In Situ Generated Colloid Transport of Cu and Zn in Reclaimed Mine Soil Profiles Associated with Biosolids Application

Areas reclaimed for agricultural uses following coal mining often receive biosolids applications to increase organic matter and fertility. Transport of heavy metals within these soils may be enhanced by the additional presence of biosolids colloids. Intact monoliths from reclaimed and undisturbed soils in Virginia and Kentucky were leached to observe Cu and Zn mobility with and without biosolids application. Transport of Cu and Zn was observed in both solution and colloid associated phases in reclaimed and undisturbed forest soils, where the presence of unweathered spoil material and biosolids amendments contributed to higher metal release in solution fractions. Up to 81% of mobile Cu was associated with the colloid fraction, particularly when gibbsite was present, while only up to 18% of mobile Zn was associated with the colloid fraction. The colloid bound Cu was exchangeable by ammonium acetate, suggesting that it will release into groundwater resources.

In situ colloid generation and transport in 30-year-old mine soil profiles receiving biosolids

Colloid mobility has been tied to contaminant transport in many agricultural soils, and may be a factor in reclaimed mine soils as well. Before contaminant transport can be predicted, the actual patterns in colloid generation and transport following disturbance needs to be elucidated. A site in the Appalachian region of southwest Virginia was chosen to observe colloid transport within natural forest soils (F), reclaimed soils (R) and reclaimed soils underlain by spoil material (RS). A fourth treatment included the application of lime-stabilised biosolids to separate RS monoliths (RSB). These intact soil monoliths were leached with de-ionised water at a rate of 1.0 cm/h for at least 2 pore volumes. Total eluted colloid loads were greatest within natural forest (F) soil monoliths (2205 mg), followed by R (1460 mg) and RS (76 mg) monoliths. The addition of biosolids (RSB) induced greater colloid transport (871 mg) compared to RS monoliths not receiving biosolids. This was likely due to an increase in pH and EC from the applied biosolids. The results suggested that colloid and potentially contaminant transport should indeed be a concern in soils disturbed by mining activities, but predicting the magnitude and patterns of colloid behaviour may be difficult due to variations in physical and chemical properties of the reclaimed soils.

Carbon and nitrogen pools in reclaimed land under forest and pasture ecosystems in Ohio, USA

The long-term changes of ecosystem carbon (C) and nitrogen (N) pools in reclaimed mine soils remains poorly understood. Thus, age chronosequence sites, ranging from < 1 to 25 years of reclamation, under forest and pasture land use, were identified to determine ecosystem C and N pools. Ecosystem C and N pools and selected soil properties were measured for 42 reclaimed sites across northeast Ohio. Soil organic C (SOC) was estimated by determining coal C and inorganic C, and subtracting these from the total soil C. Of the total soil C in reclaimed soil, coal C ranged from 0.2 to 15%, and inorganic C from < 1 to 42%, depending on soil depth and land use. The C sequestered in the minesoil ecosystem followed a polynomial function, with the highest rate of sequestration of 6.59 Mg ha − 1 after 14 years of reclamation in the forest and 1.61 Mg ha − 1 after 6 years under pasture. After 25-year of reclamation, C sequestration was 107 Mg ha − 1 under forest ecosystem and 21 Mg ha − 1 under pasture. In the forest ecosystem, a major portion of ecosystem C consisted of soil C (94%) during the initial period (< 1 year) and biomass C (66%) during the later period (> 14 year). In the pasture ecosystem, soil C contributed a major portion of ecosystem C throughout the reclamation period: 95% for < 1 year and 89% for > 25 years of reclamation. However, soil N contributed a significant portion of ecosystem N in both the forest and pasture ecosystems. Ecosystem C and N pools and bulk densities were strongly related with reclamation age for both forest and pasture. The rates of ecosystem C and N sequestration peaked at about 10 to 15 years of reclamation. After 10 to 15 years of reclamation, the rate of sequestration decreased as reclamation age increased.

The effect of different tree species on the chemical and microbial properties of reclaimed mine soils

The chemical and microbial properties of afforested mine soils are likely to depend on the species composition of the introduced vegetation. This study compared the chemical and microbial properties of organic horizons and the uppermost mineral layers in mine soils under pure pine (Pinus sylvestris), birch (Betula pendula), larch (Larix decidua), alder (Alnus glutinosa), and mixed pine–alder and birch–alder forest stands. The studied properties included soil pH, content of organic C (Corg) and total N (Nt), microbial biomass (Cmic), basal respiration, nitrogen mineralization rate (Min-N), and the activities of dehydrogenase, acid phosphomonoesterase, and urease. Near-infrared spectroscopy (NIR) was used to detect differences in the chemical composition of soil organic matter under the studied forest stands. There were significant differences in Corg and Nt contents between stands in both O and mineral soil horizons and also in the chemical composition of the accumulated organic matter, as indicated by NIR spectra differences. Alder was associated with the largest Corg and Nt accumulation but also with a significant decrease of pH in the mineral soil. Microbial biomass, respiration, the percentage of Corg present as Cmic, Min-N, and dehydrogenase activity were the highest under the birch stand, indicating a positive effect of birch on soil microflora. Admixture of alder to coniferous stand increased basal respiration, Min-N, and activities of dehydrogenase and acid phosphomonoesterase as compared with the pure pine stand. In the O horizon, soil pH and Nt content had the most important effects on all microbial properties. In this horizon, the activities of urease and acid phosphomonoesterase did not depend on microbial biomass. In the mineral layer, however, the amount of accumulated C and microbial biomass were of primary importance for the enzyme activities.