Enzymatic activity as an indicator of regeneration processes in degraded soil reclaimed with various types of waste

Soil material sampled from a reclamation experiment established in a former “Jeziórko” Sulphur Mine was analysed. The reclamation was carried out on a soil-less substrate with a particle size distribution of slightly loamy sand characterised by high acidity and poor sorption capacity. The different variants of the experiment consisted in the addition of post-flotation lime, mineral fertilisation, sewage sludge, and mineral wool to the reclaimed soil-less substrate. Next, the plots prepared in this way were sown with a mixture of grasses. A plot without any reclamation treatments served as a control. The analyses consisted in the determination of soil enzymatic parameters. The results obtained revealed a positive effect of the reclamation treatments on the analysed properties. All wastes and combinations thereof introduced into the degraded substrate stimulated catalase, protease, and urease activity. The activity of the other enzymes, i.e. dehydrogenases and acid phosphatase, as well as the level of fluorescein diacetate hydrolysis increased only in objects treated with sewage sludge. In turn, in objects receiving mineral fertilisation, a decline in the acid phosphatase activity was noted. In objects treated with mineral wool, the level of stimulation was dependent on the mode of application of this additive. In general, a mixture of 500 m³ ha^?1 of mineral wool with the substrate proved more beneficial (with the exception of the acid phosphatase activity and fluorescein diacetate hydrolysis). A higher increase in the analysed enzymatic parameters was also found in objects treated with sewage sludge combined with post-flotation lime than in objects where sewage sludge was used alone.     

Effects of biosolid application on soil properties and kiwi fruit nutrient composition on high-pH soil

Macro- and micronutrient availability in high-pH soil is a major constraint in crop production especially for the sensitive plants, such as kiwi fruit. A field study was conducted to investigate the multiyear effects of biosolid application on nutrient availability of agricultural soil and elemental sufficiency in kiwi fruit. Solar-dried biosolid applied at 0, 25, 50, 100 and 200 t ha^?1 annually for successive 2 years. The considered soil properties included pH, EC, organic matter, N, P, K, macro–microelements, heavy metals and DTPA-extractable elements were determined. Results showed that biosolid addition significantly reduced to initial soil pH from 8.2 to 7.8 at higher application doses. Optimization of pH resulted in increased levels of soluble elements in all treatments studied. Biosolid application particularly increased Fe, Cu, Zn, Mn and B concentrations to sufficient levels. Among the other elements analyzed, were not significantly affected by biosolid application. Biosolid addition also increased soil DTPA-extractable elements, especially Cd, Cu, Mn, Pb and Zn. Significant increases in DTPA-extractable elements occurred for increasing application rates at 50, 100 and 200 t ha^?1 compared to control. We conclude that municipal biosolid applied at an annual rate at or less than 200 t ha^?1 can be safely used for kiwi fruit production on high-pH soils.     

Sugarcane waste straw biochar and its effects on calcareous soil and agronomic traits of okra

Biochar has been considered a safe soil additive to enhance soil fertility and agronomic traits of different crops. This study was conducted to explore the impacts of sugarcane waste straw biochar on soil characteristics and some agronomic traits of okra. The experiment was carried out with four treatments, i.e., control, sugarcane waste straw biochar (10 ton ha^?1), farmyard manure (FYM, 10 ton ha^?1), and chemical fertilizers (NPK; 120:100:80 kg ha^?1) having three replications of each treatment. Soil samples were tested for texture, bulk density, particle density, pH, electrical conductivity (EC), organic matter content, nitrate nitrogen (NO₃-N), and extractable-P. The sugarcane waste straw biochar was characterized for plant major nutrient elements. The impact of various treatments was observed on soils and agronomic traits of okra like plant height, fruit size, fruit length, and yield of okra. Results revealed that sugarcane waste straw biochar expressed higher EC value and noticeable amounts of nitrogen (N), phosphorus (P), potassium (K), sulfur (S), and magnesium (Mg). The sugarcane waste straw biochar, in comparison with FYM and NPK, significantly improved the NO₃-N, extractable-P, OM and EC of the calcareous soil, and reduced the soil bulk density. Furthermore, plant growth and yield parameters were significantly improved under biochar application over the control, FYM and NPK. Overall, sugarcane waste straw biochar proved to be a good alternative to conventional organic and inorganic fertilizers under calcareous soil conditions.     

Unprecedented rates of landslide and surface erosion along a newly constructed road in Yunnan, China

Field measurements conducted 4 years after the construction of a new portion of the Weixi?CShangri-La road in Yunnan, China, reveal that unprecedented rates of mass wasting occurred along the road with much of this sediment directly impacting the headwaters of the Mekong River. Landslide erosion (including dry ravel) exceeded 33,000 t ha^?1 year^?1 along the most severely eroded sections of the road and averaged more than 9,600 t ha^?1 year^?1 along the surveyed 23.5 km of road; these values are the highest ever reported for road-related landslides. While surface erosion was only about 7% of the total erosion from the road, it is still more than an order of magnitude higher than typical surface erosion rates from disturbed lands in Southeast Asia. Combined landslide and surface erosion from this road delivered an estimated 19 times more sediment to the river than the remaining 99.6% of the contributing catchment. These sediment inputs are aggrading local channels, promoting downstream sediment transport, degrading aquatic habitat, and creating the possibility for a future debris flood or hyperconcentrated flow.     

Rates of Biotite Weathering,and Clay Mineral Transformation and Neoformation,Determined from Watershed Geochemical Mass-Balance Methods for the Coweeta Hydrologic Laboratory,Southern Blue Ridge Mountains,North Carolina,USA

Biotite is a common constituent of silicate bedrock. Its weathering releases plant nutrients and consumes atmospheric CO₂. Because of its stoichiometric relationship with its transformational weathering product and sensitivity to botanical activity, calculating biotite weathering rates using watershed mass-balance methods has proven challenging. At Coweeta Hydrologic Laboratory the coupling of biotite to its transformational weathering product is only valid if the stoichiometric relationship for the two phases is known; this relationship is unlikely layer-for-layer. Rates of biotite weathering and transformation of its secondary weathering product at the Coweeta Hydrological Laboratory are comparable with other Appalachian watersheds. The magnitude and sign of the difference between field- and laboratory-determined biotite weathering rates are similar to those of other silicate minerals. The influence of major-cation proportions in biomass on the rates of biotite weathering and transformational weathering product is greatest for watersheds with high biomass aggradation rates. The watershed with the lowest bedrock reactivity and highest flushing rate yielded the highest gibbsite formation rate of ~500 mol ha^?1 year^?1 and lowest kaolin-group mineral formation rates of 4–78 mol ha^?1 year^?1. The kaolin-group mineral formation rate increases as bedrock reactivity increases and flushing rate decreases to a maximum of ~300 mol ha^?1 year^?1, with a similar minimum gibbsite formation rate. The relative differences in bedrock reactivity and flux of water through Coweeta Hydrological Laboratory watersheds studied appear to be invariant over geologic timescales.     

Growth dynamics of cordgrass,Spartina alterniflora loisel., on control and sewage sludge fertilized plots in a Georgia salt marsh

Seasonal plant growth dynamics were followed for a year in undisturbed plots of tall and short formSpartina alterniflora Loisel. and in plots of short formS. alterniflora which were enriched with sewage sludge at a rate of 100 g dry sludge m^?2wk^?1, corresponding to a nitrogen enrichment of 2 g N m^?2wk^?1. Monthly determinations of aboveground live and dead biomass, density of live stems, the ratio of number of young shoots to total number of shoots, and belowground mass of macro-organic matter to a depth of 30 cm were made for each area. Sludge fertilization increased the live biomass of the short formS. alterniflora by up to 150% of the control live biomass, but had little effect on the dead biomass, stem density, or proportion of young shoots. There was a trend of increased amount of belowground macro-organic matter in fertilized compared to control plots during the last 6 months of the study. In all areas, there was a marked decrease in the proportion of young shoots from winter to early summer, followed by a rapid increase in the percent of young shoots from late summer to fall. Sampling of plots 7 and 20 months after termination of sludge enrichment showed higher plant biomass and % N content in surface soils, but no difference in N content of live plant tissue, in fertilized compared to unfertilized marsh. After 20 months, about half of the sludge nitrogen remaining in the soils of the fertilized plots had disappeared.     

Integration of geospatial technologies with RUSLE for analysis of land use/cover change impact on soil erosion: case study in Rib watershed,north-western highland Ethiopia

In recent times, soil erosion interlocked with land use and land cover (LULC) changes has become one of the most important environmental issues in developing countries. Evaluation of this complex interaction between LULC change and soil erosion is indispensable in land use planning and conservation works. This paper analysed the impact of LULC change on soil erosion in the north-western highland Ethiopia over the period 1986–2016. Rib watershed, the area with dynamic LULC change and severe soil erosion problem, was selected as a case study site. Integrated approach that combined geospatial technologies with revised universal soil loss equation model was utilized to evaluate the spatio-temporal dynamics of soil loss over the study period. Pixel-based overlay of soil erosion intensity maps with LULC maps was carried out to understand the change in soil loss due to LULC change. Results showed that the annual soil loss in the study area varied from 0 to 236.5 t ha^?1 year^?1 (tons per hectare per year) in 1986 and 0–807 t ha^?1 year^?1 in 2016. The average annual soil loss for the entire watershed was estimated about 40 t ha^?1 year^?1 in 1986 comparing with 68 t ha^?1 year^?1 in 2016, a formidable increase. Soil erosion potential that was estimated to exceed the average soil loss tolerance level increased from 34.5% in 1986 to 66.8% in 2016. Expansion of agricultural land at the expense of grassland and shrubland was the most detrimental factor for severe soil erosion in the watershed. The most noticeable change in soil erosion intensity was observed from cropland with mean annual soil loss amount increased to 41.38 t ha^?1 year^?1 in 2016 from 26.60 in 1986. Moreover, the most successive erosion problems were detected in eastern, south-eastern and northern parts of the watershed. Therefore, the results of this study can help identify the soil erosion hot spots and conservation priority areas at local and regional levels.     

Effects of nitrogen fertilization on soil labile carbon fractions of freshwater marsh soil in Northeast China

During the past 50 years, the amount of agricultural fertilizer used in Northern China increased from about 7.5 kg ha^?1 in the 1950s to approximately 348 kg ha^?1 in the 1990s. Given that little is known about the effects of nitrogen fertilization on soil labile carbon fraction in Northern China, this paper evaluated such effects in terms of microbial biomass and dissolved organic carbon in the Sanjiang Plain located in Northeast China. Soils with different cultivation time and undisturbed marsh with Deyeuxia angustifolia were selected to study the effects of nitrogen fertilization on the soil labile organic fractions microbial C (biomass C, microbial quotient, and basal respiration) and to estimate the contributions of nitrogen input on the dynamics of soil labile carbon. Continuous nitrogen application decreased total organic and dissolved organic carbon concentrations significantly, leading to the lack of carbon source for microbes. Therefore, continuous nitrogen fertilizer application induced negative effects on measured soil microbiological properties. However, a moderate nitrogen application rate (60 kg N ha^?1) stimulated soil microbial activity in the short term (about 2 months), whereas a high nitrogen application rate (150 kg N ha^?1) inhibited measured soil microbiological properties in the same period.     

Effects of biochar on aggregate characteristics of upland red soil in subtropical China

Soil aggregation is one of the key properties affecting the productivity of soils and the environmental side effects of agricultural soils. In this study, we aimed to identify whether biochar could be used to improve aggregate stability. A 2-year field experiment was conducted to investigate the effect of biochar application (0, 2.5, 5, 10, 20, 30 and 40 t ha^?1) on aggregate characteristics of upland red soil under a rapeseed–sweet potato rotation in subtropical China. Percentage of aggregate destruction (PAD_0.25), mean weight diameter (MWD), geometric mean diameter (GMD) and fractal characteristics of soil aggregates were measured using both wet and dry sieving methods. Results showed that applying biochar significantly decreased the percentage of aggregate destruction and soil fractal dimension and increased the MWD and GMD. The optimal amelioration was observed when biochar was applied at a rate of 40 t ha^?1. The decline of the fractal dimension of dry aggregates was 2–9 times as much as that of water-stable aggregates in the 0–15 soil layer and 1–4 times in the 15–30 cm soil layer. These results suggested that biochar could improve the resistance of aggregates to stresses and provide scientific strategies for the agricultural production.     

Reuse of dewatered sewage sludge conditioned with skeleton builders as landfill cover material

High water and organic content of sewage sludge constricts its reuse and disposal. It is often necessary to solidify/stabilize the dewatered sludge with solidifying agents before landfill disposal. In this study, the sewage sludge was conditioned with skeleton builders, i.e., fly ash and lime combined with ferric chloride for the purpose of improving the dewatering efficiency. The dewatered sewage sludge was then directly reused as landfill cover materials since the skeleton builders also play a role in solidification of sludge. The geotechnical properties of the dewatered sewage sludge were investigated. The results show that the plasticity index of the dewatered sludge increases compared to that of the dewatered sludge without any conditioner, and the permeability coefficient changes from 10^?8 to 10^?5 cm s^?1. Furthermore, the strength of specimens increase with curing days. Microstructure analyses reveal that the main hydrated products are calcium silicate hydrate and ettringite, which contribute to the solidification/stabilization of the dewatered sludge. The results indicate that the dewatered sewage sludge conditioned with skeleton builders can be used as landfill covers. This study provides an alternative for traditional sewage sludge treatment and disposal.     

Experimental investigation on shear strength and permeability of a deeply dewatered sewage sludge for use in landfill covers

This paper presents an experimental study on a deeply dewatered sewage sludge produced by using a new technique of membrane filter press. The experiments involve measurements of sludge composition, basic physical properties, shear strength, water permeability, and leaching toxicity. The measurements of shear strength and permeability were also performed on the sludge specimens soaked in a low acid leachate or distilled water for 1 and 2 months. This is to investigate the influence of chemical change in pore fluid as a result of rainfall infiltration or leachate seepage at landfills. Comparison tests were also carried out on silty clay that is commonly used for landfill cover material. The experimental results show that the deeply dewatered sludge contains 66 % organic content and 85 % water content (dry mass basis). The undrained shear strength of the sludge is >25 kPa even after 2-month soaking in the leachate and distilled water, meeting the requirement of the Chinese standard [CJ/T249-2007, Disposal of sludge from municipal wastewater treatment plant: sludge quality for co-landfilling. Ministry of Building and Construction, P.R. China (in Chinese), 2007]. The measured cohesion and friction angle for the sludge are >20 kPa and 22.3°, respectively. The soaking of sludge specimens in either leachate or distilled water resulted in an increase in frictional angle by several degrees. The water permeability for the sludge ranges from 0.68 × 10^?8 to 1.3 × 10^?8 cm/s, and permeability after 2-month soaking is less than the minimum requirement for the barrier layer of landfill covers (i.e., 1.0 × 10^?7 cm/s). The concentrations of heavy metals leaching from the dewatered sludge are lower than the limit values of leaching toxicity for the wastewater discharge standard of China. The experimental results indicate that deeply dewatered sludge can be used as an alternative material for the barrier layer of landfill covers.     

A comparative study on energy balance and economical indices in irrigated and dry land barley production systems

This study was conducted to determine how energy balances and economical indices of barley production are affected by irrigated and dry land farming systems. Data were collected from 26 irrigated and 68 dry land barley farms. The complimentary data were collected through questionnaires filled by farmers in face-to-face interviews during 2010. The results indicated that total energy input for irrigated barley was 19,308.96 MJ ha^?1 and for dry land barley was 7,867.82. The non-renewable energy was about 66.83 and 71.02 % in irrigated and dry land systems while the renewable energy was 33.17 and 28.98 %, respectively. Energy use efficiency is energy output MJ ha^?1 divided by energy input MJ ha^?1. Energy use efficiency was 5.3 and 3.96 in dry land and irrigated systems, respectively. Although net return in the irrigated system (266.13$ ha^?1) was greater than that in the dry land system (208.64) but the benefit to cost ratio in irrigated system (1.38) was lower than that in the dry land system (1.58). Results showed that human labor as well as machinery energy inputs were the most important inputs influencing the dry land and irrigated barley production systems, respectively. The second important input in the irrigated barley was electricity (with 0.16) which was followed by water for irrigation and diesel fuel (0.14 and 0.13, respectively). In total energy consumption, the ratio of non-renewable energy was greater than that of renewable energy. Since the main non-renewable energy input was diesel, electricity, and chemical fertilizers; therefore, management and improvement in the application of these inputs would increase the proportion of renewable energy.     

Understanding compost effects on water availability in a degraded sandy soil of Patagonia

Disturbances have the potential to reduce soil water and nutrient retention capacity by decreasing soil organic matter (SOM), which is particularly true for sandy soils characterized by an inherent low capacity to retain nutrients and water. To restore degraded areas, several works have shown positive effects of organic matter inputs on soil properties and plant growth. Despite these promising results, it is still unclear how organic matter inputs and plant growth modify the balance between soil nutrient and water supply. The objectives of the present work were (1) to evaluate the effects of biosolids compost and municipal compost addition on plant available water (PAW), soil moisture and soil temperature in a burned sandy soil of NW Patagonia (Argentina), and (2) to relate PAW and soil moisture with bulk density, soil organic carbon, nutrient availability (inorganic and potential mineralized nitrogen (N), extractable phosphorous) and aboveground phytomass. An experiment with excised vegetation and watering was also conducted. Compost application increased SOM, but it was insufficient to increase PAW. The increase in potential mineralized N in the amended soils indicated that during moist periods (and adequate temperatures), N uptake was increased, enhancing plant growth. As a consequence, higher plant water consumption in amended treatments resulted in lower soil moisture than in non-amended plots during the vegetative growth period that coincides with decreasing precipitation. Results indicate that a relatively high dose of compost (40 Mg ha^?1) applied to a sandy soil, contributed to increase nutrient availability and consequently, aboveground phytomass and water consumption.     

Bright side? The impacts of Three Gorges Reservoir on local ecological service of soil conservation in southwestern China

Three Gorges Reservoir in China was running since June 2003, and its impacts on soil erosion (SE) and soil conservation (SC) have attracted major public attentions. We quantified the soil conservation service of ecosystems in the Three Gorges Reservoir Area (TGRA) based on a GIS platform using the universal soil loss equation. We revealed the changes of spatial and temporal patterns of soil conservation (SC) and soil erosion (SE) after project construction as well as impact factors on local SE and SC. Results showed that the total amounts and mean capacity of soil conservation services in the TGRA were 15.38-billion t a^?1 and 2134.73 t ha^?1 a^?1, respectively. Northeast reservoir area owned better services than the southwest, and the regions with a capacity of >5000 t ha^?1 a^?1 were primary located in mountain areas. An increasing trend in SC appeared in the TRGA and “with increasing SC” totaled 22690.5 km² (38.9%), while the areas “with decreasing SC” amounted to 3460.4 km² (5.9%) between 2000 and 2010. Moreover, the pattern of changing SC was continuous in this area. The spatial characteristics of soil conservation service in the TGRA were primarily affected by slope, climate and terrain features. In addition, the reforestation and/or forest protection would contribute to soil erosion control in the TGRA. The results revealed a great spatial heterogeneity of soil conservation service in this region, which may provide useful suggestions for land management, soil erosion control and ecosystem protection in the TGRA in China.     

Land use,sediment loads and dispersal pathways from two catchments at the southern end of Lake Tanganyika,Africa: implications for lake management

Increasing sediment loads entering the Lake Tanganyika ecosystem are hastening the need for improved understanding of the linkages between catchment characteristics and influent sediment transport and loading. Sediment loads of two catchments at the southern end of the lake were estimated for October 1998–December 1999, and catchment characteristics determined using GIS. It was found that both sediment yields and loads were higher from the catchment of the Lunzua River (19.8 t km^?2 and 20,114 t, respectively) compared with that of the Kalambo (4.1 t km^?2 and 12,197 t) in 1999. These differences were both attributed to the smaller size and higher road density of the Lunzua catchment, and suggest that previous recommendations regarding the positioning of underwater lake reserves fail to take into account the low sediment retention capacity of small mountainous rivers. Differences between the study rivers in the transport of suspended sediments, organic matter, and bedload sediments into the lake were also found, the latter determined by the novel application of the 'McLaren Model'.     

Fungal biodiversity in sewage water under the effect of calcium hydroxide and hydrogen peroxide into two-steps treatment

Microorganisms, organic matter, heavy metals are the main pollutants in sewage water. The increasing water demand pressurized people to use the sewage water. Different systems, chemicals and physical treatments were used in sewage water treatment. The aim of this work is to study the effect and correlations of primary (Ca(OH)₂ filtration and H₂O₂) and secondary (dissolved oxygen, organic matter, conductivity, pH and OD) factors on fungi present in sewage water in addition to proving the sequence of the system used in the current study. After treatment, fungi were examined, identified on Czapek agar and analyzed using multivariate tools (CANOCO: DCA and CCA) and R software. The treatment includes two main steps: liming filtration and oxidation, respectively. All parameters were negatively or positively correlated (organic matter, pH, conductivity %, optical density, fungal CFU ml^?1, dissolved oxygen). Heavy metals were decreased due to the application of Ca(OH)₂ and H₂O₂, respectively. There were two main groups of fungi. The larger was correlated with the organic matter, whereas the second was tolerating calcium hydroxide concentrations. Aspergillus sydowii tolerated hydrogen peroxide (0.2 mll^?1(33%); Ca(OH)₂, 0.25 gl^?1). Sequential steps treatment was healthy and economically efficient. The proposed system improved water characteristics. The recommended amount of Ca(OH)₂ and H₂O₂ was 0.25 gl^?1 and 0.2 mll^?1(33%), respectively, and can remove more than 99.9% of fungal CFUs. The current study minimized the optimum dose of hydrogen peroxide used in the disinfection of sewage water from 1.5 (Mohamed in Chem Eng J 119:161–165, 2006) to 0.2 mll^?1 of H₂O₂ (the current study).     

Geospatial assessment of soil erosion intensity and sediment yield: a case study of Potohar Region,Pakistan

Estimation of spatial extent of soil erosion, one of the most serious forms of land degradation, is critical because soil erosion has serious implications on soil fertility, water ecosystem, crop productivity and landscape beauty. The primary objective of the current study was to assess and map the soil erosion intensity and sedimentation yield of Potohar region of Pakistan. Potohar is the rainfed region with truncated and complex topography lying at the top of the Indus Basin, the world’s largest irrigation networks of canals and barrages. Spatially explicit Revised Universal Soil Loss Equation (RUSLE) Model integrated with Remote Sensing-GIS techniques was used for detecting/mapping of erosion prone areas and quantification of soil losses. The results show that the Potohar region is highly susceptible to soil erosion with an average annual soil loss of 19 tons ha^?1 year^?1 of which the maximum erosion (70–208 tons ha^?1 year^?1) was near the river channels and hilly areas. The sediment yield due to the erosion is as high as 148 tons ha^?1 year^?1 with an average of 4.3 tons ha^?1 year^?1. It was found that 2.06% of the total area falls under severe soil erosion, 13.34% under high erosion, 15.35% under moderate soil erosion while 69.25% of the area lies in the low (tolerable) soil erosion. Chakwal and Jhelum districts of the region are seriously affected by erosion owing to their topography and soil properties. The information generated in this study is a step forward towards proper planning and implementation of strategies to control the erosion and for protection of natural resources. It is, hence, necessary that suitable water harvesting structures be made to control water to prevent soil erosion and provision of water in the lean season in this region. Tree plantation and other erosion control practices such as strip cropping can also minimize soil erosion in this region.     

Applicability of upflow anaerobic sludge blanket (UASB) reactor for typical sewage of a small community: its biomass reactivation after shutdown

In this study, the characteristics of sewage of small community were determined for 6 months to ascertain the type of treatment required in subtropical conditions. The results demarcated sewage of this community as a medium-strength wastewater (chemical oxygen demand: 475 mg/L, biochemical oxygen demand: 240 mg/L and total suspended solids: 434 mg/L). Chemical oxygen demand to sulphate ratio of the sewage (11.6) established that it was amenable to anaerobic digestion. The temperature, strength, biodegradability and components of sewage were suitable for anaerobic digestion, and thus, upflow anaerobic sludge blanket reactor (UASB) was selected for its treatment. These reactors are often shutdown in small communities due to environmental and/or socio-economic factors. The ability of two UASB reactors, seeded with cow dung (UASB_CD) and activated sludge of a dairy treatment plant (UASB_ASDIT) to restart after a long idle period of 12 months, was investigated along with sludge analysis by scanning electron microscope. Biomass in both reactors reactivated rapidly after shutdown period and within 30 days after substrate feeding achieved uniform removal efficiencies for chemical oxygen demand, total suspended solids, total dissolved solids, chloride and oil and grease. Chemical oxygen demand removal efficiency of both reactors became uniform and remained close to 80% after 30 days through reactivation of microbes in sludge bed due to adequate food and temperature conditions. During restart-up, at an average organic loading rate of 0.902 kg COD/m³ per day, methane yields of 0.091 and 0.084 m³/kg COD removed were achieved for UASB_CD and UASB_ASDIT reactors, respectively.     

Influence of insecticides alone and in combination with fungicides on enzyme activities in soils

Two insecticides, monocrotophos and chlorpyrifos alone and in combination with two fungicides, mancozeb and carbendazim, respectively, were assessed for their effects on the activities of arylamidase (as glucose formed from sinigrin), dehydrogenase (in terms of triphenyl formazan formed from triphenyl tetrazolium chloride) and myrosinase (as β-naphthylamine formed from l-leucine β-naphthylamide) in vertisol and laterite soils collected from a fallow groundnut (Arachis hypogaea L.) field. The influence of selected pesticides, alone and in combination on enzyme activities was concentration dependent; the activities increased with increasing concentration of the pesticides up to 2.5 kg ha^?1, whereas application of monocrotophos alone showed maximum enzyme activities up to 5.0 kg ha^?1, in both soils. However, higher concentrations (7.5 and 10 kg ha^?1) of the pesticides were either innocuous or toxic to the enzyme activities. The significant stimulation in the activities of arylamidase, dehydrogenase and myrosinase, was associated with 2.5 kg ha^?1. The maximum stimulation in arylamidase and myrosinase activity was observed at 20-day incubation, and the enzyme activities decreased gradually at 30 and 40 days of incubation. Significant increase in dehydrogenase activity was observed at 21-day incubation, and the enzyme activity decreased gradually at 28 and 35 days of incubation in both vertisol and laterite soils. The results of the present study thus, clearly, indicate that application of the insecticides alone or in combination with fungicides, in cultivation of groundnut, at field application rates improved the activities of arylamidase, dehydrogenase and myrosinase in soils.     

Chemical stabilization of metals in the environment: a feasible alternative for remediation of mine soils

Initial risk assessment characterization carried out in a tailing pond, called “El Lirio”, came from metal mining showed that these soils have low fertility; low amounts of nitrogen, organic carbon, phosphorous, and carbonates; and high concentrations of total metals (10,719 mg Zn kg^?1, 2,821 mg Pb kg^?1, and 30 mg Cd kg^?1), diethylenetriaminepentaacetic acid (DTPA)-extractable metals, and water-soluble metals, which suggest an urgent need for remediation. Different amendments have been selected, including three anthropogenic wastes: pig manure, sewage sludge, and lime; all were added to the constructed plots in the mine pond. The objectives were to: (1) reduce acid mine drainage, metal mobilization, and toxicity and (2) provide nutrients which enable plant establishment. Results showed an increase in pH, electrical conductivity, total nitrogen, organic carbon, and equivalent calcium carbonate contents. Although water- and DTPA-extractable Zn, Pb, and Cd were reduced, there was an increment in DTPA- and water-extractable Cu due to the addition of organic matter. The amendments also enhanced the establishment of plants. This study constitutes the first stage of a successful remediation programme that can be applied in similar mining areas. The chemical stabilization of metals is a cost-effective alternative for remediation of mine areas in SE Spain.