Calcium sulfate or coal combustion by-product spread on the soil surface to reduce evaporation, mitigate subsoil acidity and improve plant growth

Removal of sulfur dioxide from flue gas produced by coal-burning power plants has increased the availability of by-products that may be useful as soil amendments for agriculture. We studied the effects of surface layers (caps) of fluidized bed combustion residue-fly ash mixture (FBCR-FA) or calcium sulfate on reduction of evaporative water losses and improvements in subsurface acid soil chemical characteristics. Caps 3.8 cm thick of porous FBCR-FA, hydrated commercial calcium sulfate (CCS), or soil (check) were placed on columns of coarse-loamy, mixed, mesic Umbric Dystrochrept soil of pH 4.2. After the addition of 40 cm of water during a 16-week period, mean daily water loss from the column with the FBCR-FA cap was 0.51 mm compared to 0.98 mm in the check. Mean increase in soil exchangeable Ca in the 5- to 40-cm depth for the CCS treatment was 0.83 cmol_c kg^–1 and mean pH (H₂O) increase was 0.21 units. Mean KCl-extractable Al decreased from 6.08 to 5.52 cmol_c kg^–1. Roots of sudangrass (Sorghum bicolor (L.) Moench) planted in the columns after removal of the caps reached 2 cm depth in the control, 18 cm in the FBCR-FA and 38 cm in the CCS treated columns after 47 days of growth. The gypsum cap was effective in improving deep rooting in acid soils and the FBCR-FA cap reduced evaporative water losses.Abbreviations FBCR-FA fluidized bed combustion residue-fly ash mixture - CCS hydrated commercial calcium sulfate - ICP inductively coupled plasma - GLM general linear models.     

Gypsum amendment to soil can reduce selenium uptake by alfalfa grown in the presence of coal fly ash

Experiments in the field and greenhouse were conducted in the presence of coal fly ash to determine whether gypsum can reduce Se concentration in alfalfa (Medicago sativa L.). In the field experiment, conducted at a coal fly ash landfill, 11.2 t ha^-1 gypsum was applied to soil as a top dressing to test the effect of gypsum in reducing selenium (Se) concentration in aboveground plant tissue. There were four treatment combinations of gypsum over a two year period, 1990 and 1991: (0, 0), (0, 11.2) (11.2, 0) and (11.2, 11.2). In 1991, the Se concentration was lower in alfalfa grown with gypsum regardless of whether the gypsum was applied in both years or in only one year, indicating that the effect of gypsum application in the first year persisted into the second year. Since there was no increase in aboveground biomass with added gypsum, differences in Se concentration reflect a competitive interaction between S and Se. In the greenhouse experiment, 12 soil treatments were tested: three levels of fly ash (0, 10 and 20%) in combination with each of four levels of gypsum (0, 2.5, 5, and 7.5%). The Se concentration in alfalfa grown in 10% fly ash declined linearly with increasing gypsum dose, resulting in a reduction in Se concentration of 0.04±0.02 μg g^-1 for each 1% gypsum added for the first harvest and 0.06±0.03 μg g^-1 for each 1% gypsum added in the second harvest. Based on these results, gypsum may prove useful as a management tool to reduce the uptake of Se by plants growing on coal fly ash landfills. ei]H Lambers     

Effect of coal combustion wastes used as lime substitutes in nutrition of apples in three soils

Summary Fluidized bed combustion represents a feasible technology for energy production utilizing high S fossil fuels. The process generates not only bed waste (FBM) (coal ash plus CaSO₄ and unreacted CaO) but also flyash (FA). The later waste has not been evaluated for its effects on plants and soils. A greenhouse experiment, using apple seedlings, was carried out using FBM, FA and calcitic limestone applied at or up to twice the lime requirement on three soil materials. Seedling growth varied dependent upon the treatment-soil combination. Growth was reduced by 60% on the Manor soil from FA applied at twice the lime requirement and was attributed to the higher initial reactiveness of the FA compared to FBM or limestone. Leaf P, K, N, Cu and Al were not significantly affected by treatments over all soils while Ca, and N decreased and Mg varied depedent upon treatment. Soil pH was increased by all treatments. DTPA (diethylenetriaminepentaacetic acid) extractable Mn and Zn were good estimators of leaf Mn and Zn while DTPA Cu and Fe were not.     

Combustion influences on natural abundance nitrogen isotope ratio in soil and plants following a wildfire in a sub-alpine ecosystem

This before-and-after-impact study uses the natural abundance N isotope ratio (δ¹⁵N) to investigate the effects of a wildfire on sub-alpine ecosystem properties and processes. We measured the ¹⁵N signatures of soil, charred organic material, ash and foliage in three sub-alpine plant communities (grassland, heathland and woodland) in south-eastern Australia. Surface bulk soil was temporarily enriched in ¹⁵N immediately after wildfire compared to charred organic material and ash in all plant communities. We associated the enrichment of bulk soil with fractionation of N during combustion and volatilization of N, a process that also explains the sequential enrichment of ¹⁵N of unburnt leaves > ash > charred organic material in relation to duration and intensity of heating. The rapid decline in ¹⁵N of bulk soil to pre-fire values indicates that depleted ash, containing considerable amounts of total N, was readily incorporated into the soil. Foliar δ¹⁵N also increased with values peaking 1 year post-fire. Foliar enrichment was foremost coupled with the release of enriched NH₄ ⁺ into the soil owing to isotopic discrimination during volatilization of soluble N and combustion of organic material. The mode of post-fire regeneration influenced foliar ¹⁵N enrichment in two species indicating use of different sources of N following fire. The use of natural abundance of ¹⁵N in soil, ash and foliage as a means of tracing transformation of N during wildfire has established the importance of combustion products as an important, albeit temporary source of inorganic N for plants regenerating after wildfire.     

Control methods for mitigating biomass ash-related problems in fluidized beds

Embodiment of biomass combustion technologies in the Cretan energy system will play an important role and will contribute to the local development. The main biomass fuels of Crete are the agricultural residues olive kernel and olive tree wood. Future applications of these biofuels may create, among others, operational problems related to ash effects. In this regard, the thermal behavior of the ashes during lab-scale fluidized bed combustion tests was examined, in terms of slagging/fouling and agglomeration of bed material. Control methodologies for mitigating ash problems were applied, such as leaching the raw fuels with water and using different mineral additives during combustion. The ashes and the bed material were characterized in terms of mineralogical, chemical and morphological analyses and the slagging/fouling and agglomeration propensities were determined. The results showed that fly ashes were rich in Ca, Si and Fe minerals and contained substantial amounts of alkali, falling within the range of "certain or probable slagging/fouling". Leaching of the raw fuels with water resulted in a significant reduction of the problematic elements K, Na, Cl and S in the fly ashes. The use of fuel additives decreased the concentrations of alkali and iron minerals in the fly ashes. With clay additives calcium compounds were enriched in the bottom ash, while with carbonate additives they were enriched in the fly ash. Fuel additives or water leaching reduced the slagging/fouling potential due to alkali. Under the conditions of the combustion tests, no signs of ash deposition or bed agglomeration were noticed.     

The influence of organic soil amendments on sulfate adsorption and sulfur availability in a Brazilian Oxisol

Soil management practices that involve additions of organic materials may influence plant sulfur availability in highly-weathered, acid soils. This study evaluated the effects of organic additions on sulfate adsorption and sulfur availability in a limed (3,4 t ha^-1) and unlimed Typic Haplustox soil of the Cerrado Region of Brazil. In unlimed soil, the proportion of applied sulfate (600 kg S ha^-1 as gypsum) that was adsorbed temporarily decreased over two cropping seasons by incorporation of 10 t dry matter ha^-1 crop^-1 of guinea grass (Panicum maximum Jacq.) but not when a similar quantity of a tropical legume, feijâo de porco (Canavalia ensiformis L.), was added. Liming reduced sulfate adsorption and resulted in sulfate leaching to a depth of 30 to 45 cm. Both plant materials temporarily reduced sulfate adsorption in laboratory studies when added to an unlimed soil at a rate equivalent to 40 t ha^-1. Analysis of soil properties affected by organic additions and liming showed significant correlations between sulfate adsorption and soil pH, extractable aluminum, calcium and magnesium, and surface charge. Maize dry matter yields increased by 1.3 to 3.5 t ha^-1 with addition of both organic materials. However, only the feijâo de porco treatment resulted in increases in sulfur uptake for the years in which organic materials were applied. Determining the effects of organic material additions on plant sulfur availability is complicated by the combined effects of sulfur mineralization, sulfate adsorption, and the plant's ability to utilize adsorbed subsoil sulfate.Joint contribution of Cornell University and CPAC-EM- BRAPA. This research was supported by USAID through the Title XII CRSP subgrant SM-CRSP-10 from North Carolina State University     

A life cycle comparison of disposal and beneficial use of coal combustion products in Florida

Background, Goal, and Scope

Currently, only 40%, or 44.5 million metric tons, of coal combustion products (CCPs) generated in the United States each year by electric utilities are diverted from disposal in landfills or surface impoundments and recycled. Despite promising economic and environmental savings, there has been scant attention devoted to assessing life cycle impacts of CCP disposal and beneficial use. The objective of this paper is to present a life cycle inventory considering two cases of CCP management, including the stages of coal mining and preparation, coal combustion, CCP disposal, and CCP beneficial use. Six beneficial uses were considered: concrete production, structural fills, soil amendments, road construction, blasting grit and roofing granules, and wallboard.

Methods

Primary data for raw material inputs and emissions of all stages considered were obtained from surveys and site visits of coal-burning utilities in Florida conducted in 2002, and secondary data were obtained from various published sources and from databases available in SimaPro 5.1 (PRé Consultants, Amersfoort, The Netherlands).

Results

Results revealed that 50 percent of all CCPs produced, or 108 kg per 1,000 kg of coal combusted, are diverted for application in a beneficial use; however, the relative amounts sold by each utility is dependent on the process operating parameters, air emission control devices, and resulting quality of CCP. Diversion of 50% of all CCPs to beneficial use applications yields a decrease in the total raw materials requirements (with the exception of gravel and iron) and most emissions to air, water, and land, as compared to 100% disposal.

Discussion

The greatest reduction of raw materials was attributed to replacing Portland cement with fly ash, using bottom ash as an aggregate in concrete production and road construction in place of natural materials, and substituting FGD gypsum for natural gypsum in wallboard. The use of fly ash as cementitious material in concrete also promised significant reductions in emissions, particularly the carbon dioxide that would be generated from Portland cement production. Beneficial uses of fly ash and gypsum showed reductions of emissions to water (particularly total dissolved solids) and emissions of metals to land, although these reductions were small compared to simply diverting 50% of all CCPs from landfills or surface impoundments.

Conclusions

This life cycle inventory (LCI) provides the foundation for assessing the impacts of CCP disposal and beneficial use. Beneficial use of CCPs is shown here to yield reductions in raw material requirements and various emissions to all environmental compartments, with potential tangible savings to human health and the environment.

Recommendations and Perspectives

Extension of this life cycle inventory to include impact assessment and sensitivity analysis will enable a determination of whether the savings in emissions reported here actually result in significant improvements in environmental and human health impacts.

     

Availability of iron,manganese, zinc and phosphorus in submerged sodic soil as affected by amendments during the growth period of rice crop

Summary Effect of amendments, gypsum (12.5 tonnes/ha), farmyard manure (30 tonnes/ha), rice husk (30 tonnes/ha) and also no amendment (control) on the availability of native Fe, Mn and P and applied Zn in a highly sodic soil during the growth period of rice crop under submerged conditions was studied in a field experiment. Soil samples were collected at 0, 30, 60 and 90 days of crop growth. Results showed that extractable Fe (1N NH₄OAC pH 3) and Mn (1N NH₄OAC pH 7) increased with submergence upto 60 days of crop growth but thereafter remained either constant or declined slightly. Application of farmyard manure and rice husk resulted in marked improvement of these elements over gypsum and control. Increases in extractable Mn (water soluble plus exchangeable) as a result of submergence and crop growth under different amendments were accompanied by corresponding decreases in easily reducible Mn content of the soil. Application of 40 kg zinc sulphate per hectare to rice crop could substantially raise the available Zn status (DTPA extractable) of the soil in gypsum and farmyard manure treated plots while the increase was only marginal in rice husk and control plots indicating greater fixation of applied Zn. Available P (0.5M NaHCO₃ pH 8.5) behaved quite differently and decreased in the following order with crop growth: gypsum>rice husk>farmyard manure>control.     

The independent effects of heat,smoke and ash on emergence of seedlings from the soil seed bank of a heathy Eucalyptus woodland in Grampians (Gariwerd) National Park,western Victoria

Abstract The independent effects of smoke, ash, and wet and dry heat treatments on seedling emergence from the soil seed bank were tested for soils from fire-prone heathy woodlands in western Victoria. A total of 763 individuals from 56 species were recorded from the surface soil samples (which covered a total area of 1 m²). Both species richness and density of seedlings was greater for smoke- and heat-treated samples than for controls and ash-treated samples. However, only the density differences were significant. Mean seed bank densities for the smoke and heat treatments ranged from 855 ± 70m^?2 to 1080 ± 58 m^?2 and are similar to estimates obtained elsewhere in Australia for heat-treated soils from dry sclerophyll communities. Of the 56 species recorded, 46 occurred in the smoke and heat treatments but only 33 in the control and ash treatments. The sudden increase in surface soil pH, exchangeable cations and extractable phosphorus which was associated with the ash treatment did not act as a trigger for germination in any of the species recorded here. Chemical constituents from smoke do appear to provide a stimulus separate from the effects of heat, but were not identified with any particular taxa.     

Utilization of Illinois PCC Dry Bottom Ash for Compacted Landfill Barriers

Compacted soil barriers are one of the most important components of municipal waste landfills. The material used to construct a landfill liner and/or cap must prevent the flow of fluids through them. Soils with low values of permeability (such as compacted clays) are often used to construct landfill barriers. Natural sands and other cohesionless materials are used to construct hydraulic barriers by adding admixtures to modify their properties. Several studies have been conducted that dealt with determining geotechnical engineering properties of sand-bentonite mixtures. Pulverized coal combustion (PCC) dry bottom ash is a coal combustion by-product of burning coal to produce electricity. Because of the increasing costs associated with the disposal of bottom ash and the environmental regulations in place, there is a need to develop alternate methods for profitable and environmentally safe uses of this waste material. Most scientists and researchers have concluded that bottom ash has geotechnical characteristics similar to those of sands. However, information on the use of bottom ash, with or without admixtures, in the construction of landfill barriers is limited. Most of the available literature on the engineering properties of bottom ash deals with its use as a fill material. The physical and chemical characteristics of bottom ash depend on several factors including type of coal used and type of boiler and collection system. This paper presents the results of an experimental study conducted to determine the possible use of Illinois PCC dry bottom ash amended with bentonite to construct landfill barriers. Test results presented show that the average value of hydraulic conductivity of Illinois PCC dry bottom ash with 15% bentonite content is close to the acceptable value required for its use as hydraulic barrier. Therefore, it was concluded that Illinois PCC dry bottom ash, modified with 15% or higher bentonite content, is likely to provide adequate hydraulic conductivity for its use to construct landfill barriers.     

Calcium and temperature effects on seedling exudation and root rot infection of common bean on an acid sandy soil

Soil born fungi such as Phytium ultimum, Fusarium ssp., and Rhizoctonia solani (Kühn) severely restrict stand establishment of common bean (Phaseolus vulgaris L.) on acid soils of the Tropics. Calcium application is known to alleviate fungal infection in many legumes but the causes are still unclear. To investigate environmental factors and physiological mechanisms involved, growth chamber experiments were conducted with an acid sandy soil from Mexico. Treatments were soil liming at a rate of 0.67 g Ca(OH)₂ kg^-1, gypsum application at 0.49 g CaSO₄ 2H₂O kg^-1 soil placed around the seed, and an untreated control. Beans were grown under three temperature regimes with constant night and one constant day vs. two sinusoidal day temperatures. To examine patterns of seed and seedling exudation at regular intervals leachates of germinating seeds were collected on filter paper soaked with equilibrium solutions from soils of the three treatments. The severity of root rot in the control treatment was highest when plants were stressed by temperature extremes. At a sinusoidal day temperature peaking at 40°C soil liming and gypsum application to the seed increased the number of healthy seedlings similarly by over 60%. However, only liming which effectively eliminated growth constraints by low pH and high aluminum concentrations led to an increase in hypocotyl elongation by 22% and in total root length by 8%. Both calcium amendments increased the calcium and potassium contents in the hypocotyl tissue. From seeds exposed to the equilibrium solution of unlimed soil with pH 3.7, 1 mM Ca, and 0.6 mM Al considerable amounts of amino acids and carbohydrates were leached. In contrast, exposure to the equilibrium solution from limed soil with pH 4.3, 3 mM Ca, and negligible concentrations of Al led to a net uptake of amino acids and decreased leaching of carbohydrates. Exposure to the equilibrium solution of the gypsum treatment with pH 3.6, 20 mM Ca, and 1.2 mM Al resulted in a somewhat smaller net uptake of amino acids compared to liming. During germination pH around the seeds steeply increased in the untreated control but significantly less with both amendments. The results indicate that pH and the Ca/Al ratio in the soil solution around bean seeds determine their pattern of exudation and solute uptake. For bean germination and early growth on acid soils locally placed application of small amounts of gypsum as seed pelleting seems as effective as soil liming in reducing the incidence of root rot. The results indicate that this may be accomplished by decreasing the amount of leachates available for fungal development.     

Turf culture under declining volume and frequency of irrigation on a sandy soil amended with fly ash

The effects of four rates (0, 5, 10 and 20%, wt/wt) of fly ash amendment in a sandy soil (top 100–120 mm) on soil properties, turf (Cynodon dactylon (L.) Pers., cv. Wintergreen) water relations, growth and colour, were assessed during 84 days of irrigation treatments (irrigated daily, every 3^rd day, or every 4^th day) imposed during summer in a Mediterranean-type climate. In plots irrigated at 40% of net evaporation summed and applied every 3^rd day: (i) soil water contents were 14–33% higher in the fly ash amended soil zone when compared to values in plots with non-amended soil; (ii) soil water content below the root zone (i.e., 1500 mm) during that period remained low (being only 1–2% above the permanent wilting point), indicating minimal, if any, deep drainage. Extractable soil P was 2.0- to 3.8-fold higher in the fly ash amended soil compared to non-amended soil. By contrast extractable P was 1.7- to 2.1-fold higher in the soil 100–500 mm below the surface in non-amended plots, compared with fly ash amended plots. Irrigation at 40% replacement of net evaporation summed and applied every 3^rd day did not adversely impact on turf growth or colour, when compared to plots irrigated daily, irrespective of fly ash treatments. However, extending irrigations (at 40% of net evaporation) to every 4^th day reduced turf growth and colour, but the turf recovered fully from the mild water stress within 21 days of being irrigated daily at 100% replacement of net evaporation. Therefore, 40% replacement of net evaporation summed and applied every 3^rd day was a suitable watering schedule for maintenance of turf, with minimal risks of deep drainage.     

Desodification from calcareous saline sodic soil through phytoremediation with Phragmites australis (Cav.) Trin. ex Steud. and gypsum

The reclamation of saline sodic soils requires sodium removal and the phytoremediation is one of the proven low-cost, low-risk technologies for reclaiming such soils. However, the role of Phragmites australis in reclaiming saline sodic soils has not been evaluated extensively. The comparative reclaiming role of P. australis and gypsum was evaluated in a column experiment on a sandy clay saline sodic soil with EC_e 74.7 dS m^?1, sodium adsorption ratio (SAR) 63.2, Na⁺ 361 g kg^?1, and pH 8.46. The gypsum at 100% soil requirement, planting common reed (P. australis) alone, P. australis + gypsum at 50% soil gypsum requirements, and leaching (control without plant and gypsum) were four treatments applied. After 11 weeks of incubation, the results showed that all treatments including the control significantly reduced pH, EC, exchangeable Na⁺, and SAR from the initial values, the control being with least results. The gypsum and P. australis + gypsum were highly effective in salinity (EC_e) reduction, while sodicity (SAR) and Na⁺ reductions were significantly higher in P. australis + gypsum treatment. The reclamation efficiency in terms of Na⁺ (83.4%) and SAR (86.8%) reduction was the highest in P. australis + gypsum. It is concluded that phytoremediation is an effective tool to reclaim saline sodic soil.     

Soil factors affecting selenium concentration in wheat grain and the fate and speciation of Se fertilisers applied to soil

UK crops have a low selenium (Se) status, therefore Se fertilisation of wheat (Triticum aestivum L.) at 10 field sites was investigated and the effect on the content and speciation of Se in soils determined. Soil characterisation was carried out at each field site to determine the soil factors that may influence wheat grain Se concentrations in unfertilised plots. Soil samples were taken after harvest from each treatment to determine the fate and speciation of selenate fertiliser applied to soil. Wheat grain Se concentrations could be predicted from soil Se concentration and soil extractable sulphur (S) using the following regression model: Grain Se?=?a?+?b(total soil Se)?+?c(extractable soil Se) - d(extractable soil S), with 86 % of the variance being accounted for, suggesting that these properties control Se concentrations in grain from unfertilised plots. Extractable soil Se concentrations were low (2.4 – 12.4 µg kg^?1) and predominantly consisted of selenite (up to 70 % of extractable Se) and soluble organic forms, whereas selenate was below the detection limit. Little of the added Se, in either liquid or granular form was left in the soil after crop harvest. Se fertilisation up to 20 g ha^?1 did not lead to a significant Se accumulation in the soil, suggesting losses of Se unutilised by the crop.     

Gains and losses in soil nutrients associated with harvesting and burning eucalypt rainforest

In mixed eucalypt/rainforest in southern Tasmania, samples of surface soil 0 to 2 cm, 2 to 5 cm, and 5 to 10 cm were taken from a clear-felled coupe before and after burning in 1982, from a similar coupe after burning in 1979, and from an uncut area adjacent to each coupe. Factors compared were bulk density; total organic C, N, P, Ca, Mg, and K; pH; exchangeable Ca, Mg, and K; cation exchange capacity; extractable P; and N-mineralisation rates. The effect of burning was found to be restricted mainly to the upper 2 cm of soil. The combustion of organic matter caused losses of 7360 kg organic C and 211 kg N/ha; 348 kg Ca and 282 kg Mg and 151 kg K/ha were added to the soil in ash. Burning caused significant increases in pH, exchangeable Ca, Mg, and K, and in extractable P; cation exchange capacity was reduced. In the 6 months after burning only K was leached from the upper 2 cm of soil. Equilibrium levels of NH₄?N increased initially after the fire, but between 6 and 18 months, equilibrium levels and rate of production of NH₄?N during anaerobic incubation in soil of burned coupes differed little from that in adjacent uncut forest. Rates of production of NO₃?N during aerobic incubation were very low throughout the period of study. It is concluded that for soils developed on dolerite in mixed eucalypt/rainforest, a single regeneration burn probably improves the nutritional status of the soil. Nutrients lost from the area as particulate ash are in quantities that will probably be replaced in rainfall in 15 to 20 years.     

Urease activity in soils

Summary The availability of Ca from different levels of gypsum and calcium carbonate in a non-saline sodic soil has been investigated. Different levels of tagged gypsum (Ca⁴⁵SO₄.2H₂O) and calcium carbonate (Ca⁴⁵CO₃) (i.e. 0, 25, 50, 75, and 100 per cent of gypsum requirement) were mixed thoroughly in 3.5 Kg of a non-saline alkali soil (ESP, 48.4; ECe, 2.68 millimhos/cm). Dhaincha (Sesbania aculeata) — a legume and barley (Hordeum vulgare L.) — a cereal were taken as test crops. Increasing levels of gypsum caused a gradual increase in the yield of dry matter, content of Ca and K in the plant tops and Ca:Na and (Ca+Mg):(Na+K) ratios in both the crops. Application of calcium carbonate caused a slight increase in the dry matter yield, content of Ca and Mg and Ca:Na and (Ca+Mg):(Na+K) ratios in barley, however, in case of dhaincha there was no such effect. Gypsum application caused a gradual decrease in the content of Na and P in both the crops. Total uptake of Ca, Mg, K, N and P per pot increased in response to gypsum application. The effect of calcium carbonate application on the total uptake of these elements was much smaller on dhaincha, but in barley there was some increasing trend.Increasing application of tagged gypsum and calcium carbonate caused a gradual increase in the concentration and per cent contribution of source Ca in both the crops, although, the rate of increase was considerably more in dhaincha. The availability of Ca from applied gypsum was considerably more than that from applied calcium carbonate. Efficiency of dhaincha to utilize Ca from applied sources was considerably more (i.e. about five times) than that of barley     

Polycyclic Aromatic Hydrocarbon (PAH) Contamination in the Urban Topsoils of Shenyang,China

Polycyclic aromatic hydrocarbons (PAHs) in the surface urban soils of Shenyang in Northeastern China were investigated. The total concentration of the PAHs ranged from 0.09 to 8.35 mg kg^?1, with an average value of 1.51 ± 1.64 mg kg^?1. 3–5-ring PAHs accounted for 90% of total PAHs. The functional areas, such as the industrial regions (4.95 mg kg^?1) and main roads (1.56 mg kg^?1), as well as the administrative divisions, including the districts of Shenhe (1.49 mg kg^?1), Heping (2.08 mg kg^?1), and Tiexi (2.14 mg kg^?1), were heavily polluted by PAHs. The diagnostic ratios and principal component analysis (PCA) for PAHs indicate that the pollutants probably originated primarily from coal combustion and petroleum sources. The Nemerow composite index, used to assess environmental quality, shows that the soil samples were heavily polluted with PAHs, and although 52.8% of the soil sampling sites were safe, 47.2% of the soil sampling sites registered different grades of PAH pollution. The PAH contamination in Shenyang emphasizes the need for controlling fossil fuel combustion and traffic exhaust.     

Effects of Adding Alkaline Material on the Heavy Metal Chemical Fractions in Soil under Flooded and Non-Flooded Conditions

We investigated the effect of adding an alkaline material (containing calcium carbonate and gypsum) on the immobilization of heavy metals (Cd, Cu, Pb, and Zn) in a paddy soil slightly contaminated with Cd and Zn under flooded and non-flooded conditions in the laboratory. Adding the alkaline material increased the soil pH and significantly decreased the exchangeable fraction of all of the metals, especially for Cd (>75% decrease) and Zn (ca. 90% decrease), under both flooded and non-flooded conditions. Drying the flooded soil samples increased the ratio of exchangeable fraction to the total fraction, particularly for Cd. The exchangeable fraction ratio was lower in the dried, previously flooded samples that contained the alkaline material than in the samples that did not contain the alkaline material, indicating that adding the alkaline material would be an effective way of immobilizing heavy metals during the oxidation of anoxic soils. These results show that the alkaline material can be used to immobilize heavy metals under both anoxic and oxic conditions, and that the effects of flooding and amending a paddy soil with alkaline material on the chemical forms will be different between heavy metals.     

Biological indicators provide short term soil health assessment during sodic soil reclamation

Sodic soil remediation is an expensive, lengthy process during which producers need tools to demonstrate that sodium (Na⁺) remediation practices are improving soil health. The objective of this study was to determine if soil biological indicators can provide a short term assessment of the effectiveness of chemical management strategies used to remediate northern Great Plains sodium affected soils. This randomized complete block split-plot research experiment was conducted in a grassland which was converted to annual row crops. The soil at the site was an Exline (fine, smectitic, frigid Leptic Natrudolls). The experiment contained two drainage treatments (tile drained and no-drainage) and four chemical amendments (4.5 Mg ha⁻¹ of gypsum, 9.1 Mg ha⁻¹ of gypsum, 9.1 Mg ha⁻¹ spent sugar beet lime, and a no amendment control). Base-line soil samples for biological assessment were collected in the fall of 2012 after tile drainage was installed. The sodium adsorption ratio (SAR) ranged from 0.4 to 16.7 with a range of electrical conductivity (EC) of 0.4–0.8 dS m⁻¹. Gypsum and lime amendments were applied in 2013. Soil samples were collected for assessing soil health before and after application of amendments and throughout the growing season. This study utilizes a novel application of successional vector trajectories to compare shifts in measured soil health parameters associated with land use change and remediation of sodicity. Soil samples were analyzed for percent total soil carbon (C), nitrifier and denitrifier gene copies, soil enzyme assays (nitrate reductase, ammonia monooxegenase, urease, β glucosidase, alkaline phosphatase, arylsulfatase and fluorescein diacetate hydrolysis), EC, pH, SAR, and soil texture. Gene copies and enzyme activities were successfully used to differentiate between land uses and amendment applications. Ammonia oxidizing bacterial gene copies were higher where cropland was amended with gypsum. Successional vectors verified a significant shift in soil health due to land use change and amendment application. Gypsum applications reduced SAR, but increased soil EC. This work demonstrates that soil enzyme activities and gene copy numbers can be used to detect improvements in soil health.     

Soil Algae in Brown Coal and Lignite Post-Mining Areas in Central Europe (Czech Republic and Germany)

Algal communities were investigated in two contrasting chronosequences established on reclaimed spoils in the west Bohemian brown coal mining district near Sokolov (Czech Republic) and in the Lusatian lignite mining district near Cottbus (Germany). The Sokolov chronosequence was characterized by tertiary cypric clay substrate, afforestation with Alnus glutinosa (L.) Gaertn., and high pH of deposited spoil material, Cottbus chronosequence by tertiary carboniferous and pyritic sand of extremely low pH ameliorated by fly ash, and afforestation with Pinus sylvestris L. and P. nigra Arnold. A total of 122 species of algae was found in both areas. Although the same species number (80) was identified from Sokolov and Cottbus, both proportion of individual algal groups and species composition were different. Green algae prevailed in both areas, but in Sokolov cyanobacteria and diatoms were also quite diverse, and in younger sites they were also abundant. Total abundance of algae ranged mostly between 10⁴–10⁷ cells/g dry soil, and was one order higher in Cottbus than in Sokolov. Species number was high in young sites, decreased with increasing age, and was the lowest in control forests. In Sokolov, the highest abundance was recorded in the youngest alder plantation. In Cottbus, sludge and compost fertilization used in the youngest pine plantations resulted in rapid formation of visible algal crusts dominated by Klebsormidium crenulatum (Kütz) Lokhorst.