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1.
To model the impacts of ecoroofs on building envelope heat transfer accurately, thermal property data for ecoroof soils are needed. To address this need we have measured thermal conductivity, specific heat capacity, thermal emissivity, short wave reflectivity (albedo) and density for ecoroof soil samples over a range of moisture states. To represent a wide range of commonly used ecoroof soils we created eight test samples using an aggregate (expanded shale or pumice), sand, and organic matter in varying volumetric composition ratios. The results indicate significant variability in properties as a function both of soil composition and soil wetness. Thermal conductivity ranged from 0.25 to 0.34 W/(m K) for dry samples and 0.31–0.62 W/(m K) for wet samples. Specific heat capacity ranged from 830 to 1123 J/(kg K) for dry samples and 1085–1602 J/(kg K) for wet samples. Albedo was consistently higher for dry samples (0.17–0.40) decreasing substantially (0.04–0.20) as moisture was added. Thermal emissivities were relatively constant at 0.96 ± 0.02 regardless of soil type or moisture status. These results are discussed in the context of their impacts on building energy consumption and the importance of including daily and seasonal property variation within models of the ecoroof energy balance.  相似文献   

2.
The aim of our study was to measure the amount of moisture absorption and desorption in clay–sand plaster mixed with “fibre-wool” from Typha spadixes and chips of Typha and Phragmites. Common cattail (Typha latifolia) and common reed (Phragmites australis) are the most common plants in constructed and semi-natural wetlands for wastewater treatment, as they are highly valued in ecologically oriented construction. The cattail and reed for the experiment were harvested in a wastewater treatment subsurface flow semi-natural wetland and in two free water surface constructed wetlands which showed reliable aboveground phytomass production over a 5 years period (for Typha, 0.37–1.76 kg DW m−2 in autumn and 0.33–1.38 kg DW m−2, and for Phragmites, 0.61–1.32 and 0.61–1.02 kg DW m−2, respectively). The quantity of moisture absorption and desorption was measured in a climatic chamber where the humidity of ambient air was suddenly raised from 50% to 80% (absorption) and reduced from 80% to 50% (desorption). Over 12 h, all of the samples released the same amount of water as they absorbed. The clay–sand plaster samples absorbed slower than they desorbed, whereas the gypsum wallboard required significantly more time for desorption. Added phytomass gave positive effects by reducing the weight of the clay–sand plaster, accelerating and increasing moisture absorption.  相似文献   

3.
4.
Experiments on the thermal decomposition of wet wood in air were carried out in this work. The samples (typically 100×100 mm exposed surface, 15 mm thick) of several species with moisture content from 5% to 30% were subjected to a uniform heat flux 20–70 kW m−2. A one-dimensional pyrolysis model is proposed to examine the influence of heat flux, species and moisture content on the process of thermal decomposition of wet wood. Temperature profiles at different points and solid conversion are calculated and compared with experimental data. There is good agreement between the experimental and calculated results.  相似文献   

5.
Profile storage of organic/inorganic carbon in soil: From forest to desert   总被引:3,自引:0,他引:3  
Understanding the distribution of organic/inorganic carbon storage in soil profile is crucial for assessing regional, continental and global soil C stores and predicting the consequences of global change. However, little is known about the organic/inorganic carbon storages in deep soil layers at various landscapes. This study was conducted to determine the soil organic/inorganic carbon storage in soil profile of 0-3 m at 5 sites of natural landscape from forest to desert. Landscapes are temperate forest, temperate grassland, temperate shrub-grassland, temperate shrub desert, and temperate desert. Root mass density and carbon contents at the profile were determined for each site. The results showed that considerable decrease in root biomass and soil organic carbon content at the soil profile of 0-3 m when landscape varied from forest to desert along a precipitation gradient, while soil inorganic carbon content increased significantly along the precipitation gradient. Namely, for density of soil organic carbon: forest > grassland > shrub-grassland > shrub desert > desert; for density of soil inorganic carbon: forest, grassland < shrub-grassland < shrub desert < desert (P < 0.05 in all cases). In landscapes other than forest, more than 50% soil carbon storage was found in 1-3 m depth. For grassland and shrub-grassland, the contribution from 1-3 m was mainly in the form of organic carbon, while for shrub desert and desert the contribution from this depth was mainly in the form of inorganic carbon. The comparison of soil C storage between top 0-1 m and 1-3 m showed that the using top 1 m of soil profile to estimate soil carbon storages would considerably underestimate soil carbon storage. This is especially true for organic soil carbon at grassland region, and for soil inorganic carbon at desert region.  相似文献   

6.
This study was conducted to investigate the long-term effects of fire on soil phosphorus (P) and to determine the efficiency of different procedures in extracting soil P forms. Different P forms were determined: labile forms (Olsen-P, Bray-P, and P extracted by anion exchange membranes: AEM-P); moderately labile inorganic and organic P, obtained by NaOH-EDTA extraction after removing the AEM-P fraction; and total organic and inorganic soil P. 31P-NMR spectroscopy was used to characterize the structure of alkali-soluble P forms (orthophosphate, monoester, pyrophosphate, and DNA). The studied area was a Pinus pinaster forest located at Arenas de San Pedro (southern Avila, Spain). The soils were Dystric Cambisols over granites. Soil samples were collected at 0-2 cm, 2-5 cm, and 10-15 cm depths, two years after a fire in the burned area and in an adjacent unburned forest area. Fire increased the total N, organic C, total P, and organic and inorganic P content in the surface soil layer. In burned soil, the P extracted by the sequential procedure (AEM and NaOH + EDTA) was about 95% of the total P. Bray extraction revealed a fire-induced increase in the sorption surfaces. Analysis by chemical methods overestimated the organic P fraction in the EDTA-NaOH extract in comparison with the determination by ignition procedure. This overestimation was more important in the burned than unburned soil samples, probably due to humification promoted by burning, which increased P sorption by soil particles. The fire-induced changes on the structure of alkali-soluble P were an increase in orthophosphate-P and a decrease in monoester-P and DNA-P.  相似文献   

7.
Basic soil parameters of Kozlar high plateau in Mut (Mersin) have been investigated. Soil samples were collected from the eroded, maquis and forest habitats of the research area in January, October, April and July between 2000 and 2002. The average values for soil moisture, CaCO3, saturation percentage, field capacity, salinity, conductivity, pH, total carbon and total nitrogen were found in the range of 4.0–19.7%, 25.0–33.3%, 39.7–72.1%, 22.0–56.0%, 0.027–0.074 dS/m, 0.80–1.2 μS/cm, 7.5–8.1, 0.82–5.50%, and 0.10–0.58%, respectively. Generally, despite no significant differences among the soil parameters of the three habitats, only three parameters, saturation percentages, amount of total carbon and of carbon mineralization differed significantly.  相似文献   

8.
Estimating dermal absorption from contaminated soils typically requires extrapolations from measurements obtained on soils artificially contaminated at much larger concentrations. Such extrapolations should be constrained by the fact that maximum absorption will occur for the largest possible concentration of chemical on the soil without neat chemical being present; i.e., at the soil saturation limit (Ssoil). Saturation limits of two low-volatility model compounds (4-cyanophenol and methyl paraben) were determined on the 38-63 μm sieve fraction of four soils with different fractions of organic carbon (foc = 0.015-0.45) and specific surface areas (σsoil = 4-34 m2 g− 1) using two methods: equilibrium uptake into silicone rubber membranes and differential scanning calorimetry. Except for Pahokee peat, which had the largest foc, a model assuming contributions from both surface adsorption and organic carbon absorption provided excellent predictions of Ssoil. In all soils, the surface saturation concentration of both chemicals was estimated at 2.2 mg m− 2. The saturation concentration of 4-cyanophenol in the soil organic carbon was 1.7-fold higher than methyl paraben, which is consistent with the estimated solubility limits of these two chemicals in octanol.  相似文献   

9.
The presence of energetic materials (used as explosives and propellants) at contaminated sites is a growing international issue, particularly with respect to military base closures and demilitarization policies. Improved understanding of the ecotoxicological effects of these materials is needed in order to accurately assess the potential exposure risks and impacts on the environment and its ecosystems. We studied the toxicity of the nitroaromatic energetic material 2,4-dinitrotoluene (2,4-DNT) on alfalfa (Medicago sativa L.), barnyard grass (Echinochloa crusgalli L. Beauv.), and perennial ryegrass (Lolium perenne L.) using four natural soils varying in properties (organic matter, clay content, and pH) that were hypothesized to affect chemical bioavailability and toxicity. Amended soils were subjected to natural light conditions, and wetting and drying cycles in a greenhouse for 13 weeks prior to toxicity testing to approximate field exposure conditions in terms of bioavailability, transformation, and degradation of 2,4-DNT. Definitive toxicity tests were performed according to standard protocols. The median effective concentration (EC50) values for shoot dry mass ranged from 8 to 229 mg kg− 1, depending on the plant species and soil type. Data indicated that 2,4-DNT was most toxic in the Sassafras (SSL) and Teller (TSL) sandy loam soils, with EC50 values for shoot dry mass ranging between 8 to 44 mg kg− 1, and least toxic in the Webster clay loam soil, with EC50 values for shoot dry mass ranging between 40 to 229 mg kg− 1. The toxicity of 2,4-DNT for each of the plant species was significantly (p ≤ 0.05) and inversely correlated with the soil organic matter content. Toxicity benchmark values determined in the present studies for 2,4-DNT weathered-and-aged in SSL or TSL soils will contribute to development of an Ecological Soil Screening Level for terrestrial plants that can be used for ecological risk assessment at contaminated sites.  相似文献   

10.
The effects of insect defoliators on throughfall and soil nutrient fluxes were studied in coniferous and deciduous stands at five UK intensive monitoring plots (1998 to 2008). Links were found between the dissolved organic carbon (DOC), nitrogen (N) and potassium (K) fluxes through the forest system to biological activity within the canopy. Underlying soil type determined the leaching or accumulation of these elements. Under oak, monitored at two sites, frass from caterpillars of Tortrix viridana and Operophtera brumata added direct deposition of ~ 16 kg ha−1extra N during defoliation. Peaks of nitrate (NO3-N) flux between 5 and 9 kg ha−1 (×5 usual winter values) were recorded in consecutive years in shallow soil waters. Synchronous rises in deep soil NO3-N fluxes at the Grizedale sandy site indicate downward flushing, not seen at the clay site. Under three Sitka spruce stands, generation of honeydew (DOC) was attributed to two aphid species (Elatobium abietinum and Cinara pilicornis) with distinctive feeding strategies. Throughfall DOC showed mean annual fluxes (6 seasons) ~ 45-60 kg ha−1 compared with rainfall values of 14-22 kg ha−1. Increases of total N in throughfall and NO3-N fluxes in shallow soil solution were detected — soil water fluxes reached  8 kg ha−1 in Llyn Brianne, ~ 25 kg ha−1 in Tummel, and ~ 40 kg NO3-N ha−1 in Coalburn. At Tummel, on sandy soil, NO3-N leaching showed increased concentration at depth, attributed to microbiological activity within the soil. By contrast, at Coalburn and Llyn Brianne, sites on peaty gleys, soil water NO3-N was retained mostly within the humus layer. Soil type is thus key to predicting N movement and retention patterns. These long term analyses show important direct and indirect effects of phytophagous insects in forest ecosystems, on above and below ground processes affecting tree growth, soil condition, vegetation and water quality.  相似文献   

11.
Arsenic bioaccessibility in soils near chromated copper arsenate (CCA)-treated structures has recently been reported, and results have shown that soil properties and arsenic fractionation can influence bioaccessibility. Because of the limited data set of published results, additional soil samples and a wider range of soil properties are tested in the present work. The objectives are: (1) to confirm previous results regarding the influence of soil properties on arsenic bioaccessibility in CCA-contaminated soils, (2) to investigate additional soil properties influencing arsenic bioaccessibility, and to identify chemical extractants which can estimate in vitro gastrointestinal (IVG) bioaccessibility, (3) to determine arsenic speciation in the intestinal phase of the IVG method and, (4) to assess the influence of two particle-size fractions on arsenic bioaccessibility. Bioaccessible arsenic in eight soils collected near CCA-treated utility poles was assessed using the IVG method. Five out of the eight soils were selected for a detailed characterization. Moreover, these five soils and two certified reference materials were tested by three different metal oxide extraction methods (citrate dithionite (CD), ammonium oxalate (OX), and hydroxylamine hydrochloride (HH)). Additionally, VMINTEQ was used to determine arsenic speciation in the intestinal phase. Finally, two particle-size fractions (< 250 μm, < 90 μm) were tested to determine their influence on arsenic bioaccessibility. First, arsenic bioaccessibility in the eight study-soils ranged between 17.0 ± 0.4% and 46.9 ± 1.1% (mean value 30.5 ± 3.6%). Using data from 20 CCA-contaminated soil samples, total organic carbon (r = 0.50, p < 0.05), clay content (r = − 0.57, p < 0.01), sand content (r = 0.48, p < 0.05), and water-soluble arsenic (r = 0.66, p < 0.01) were correlated with arsenic bioaccessibility. The mean percentage of total arsenic extracted from five selected soils was: HH (71.9 ± 4.1%) > OX (58.0 ± 3.1%) > water-soluble arsenic (2.2 ± 0.5%), while the mean value for arsenic bioaccessibility was 27.3 ± 2.8% (n = 5). Arsenic extracted by HH (r = 0.85, p < 0.01, n = 8) and OX (r = 0.93, p < 0.05, n = 5), showed a strong correlation with arsenic bioaccessibility. Moreover, dissolved arsenic in the intestinal phase was exclusively under the form of arsenate As(V). Finally, arsenic bioaccessibility (in mg/kg) increased when soil particles < 90 μm were used.  相似文献   

12.
One feature of climate warming is that increases in daily minimum temperature are greater than those in daily maximum temperature. Changes in soil microclimate in response to the asymmetrically diurnal warming scenarios can help to explain responses of ecosystem processes. In the present study, we examined the impacts of day, night, and continuous warming on soil microclimate in a temperate steppe in northern China. Our results showed that day, night, and continuous warming (approximately 13 W m− 2 with constant power mode) significantly increased daily mean soil temperature at 10 cm depth by 0.71, 0.78, and 1.71 °C, respectively. Night warming caused greater increases in nighttime mean and daily minimum soil temperatures (0.74 and 0.99 °C) than day warming did (0.60 and 0.66 °C). However, there were no differences in the increases in daytime mean and daily maximum soil temperature between day (0.81 and 1.13 °C) and night (0.81 and 1.10 °C) warming. The differential effects of day and night warming on soil temperature varied with environmental factors, including photosynthetic active radiation, vapor-pressure deficit, and wind speed. When compared with the effect of continuous warming on soil temperature, the summed effects of day and night warming were lower during daytime, but greater at night, thus leading to equality at daily scale. Mean volumetric soil moisture at the depth of 0-40 cm significantly decreased under continuous warming in both 2006 (1.44 V/V%) and 2007 (0.76 V/V%). Day warming significantly reduced volumetric soil moisture only in 2006, whereas night warming had no effect on volumetric soil moisture in both 2006 and 2007. Given the different diurnal warming patterns and variability of environmental factors among ecosystems, these results highlight the importance of incorporating the differential impacts of day and night warming on soil microclimate into the predictions of terrestrial ecosystem responses to climate warming.  相似文献   

13.
Riparian ecosystems have critical impacts on controlling the non-point source pollution and maintaining the health of aquatic ecosystems. In this study, a process oriented soil denitrification model was extended with algorithms from a simple nitrogen (N) cycle model and coupled to land surface remote sensing data to enhance its performance in spatial and temporal prediction of gaseous N emissions from soils in the riparian buffer zone surrounding the Guanting reservoir (China). The N emission model is based on chemical and physical relationships that govern the heat budget, soil moisture variations and nitrogen movement in soils. Besides soil water and heat processes, it includes nitrification, denitrification and ammonia (NH3) volatilization. SPOT-5 and Landsat-5 TM satellite data were used to derive spatial land surface information and the temporal variation in land cover parameters was also used to drive the model. A laboratory-scale anaerobic incubation experiment was used to estimate the soil denitrification model parameters for the different soil types. An in situ field-scale experiment was conducted to calibrate and validate the soil temperature, moisture and nitrogen sub-models. An indirect method was used to verify simulated N emissions, resulting in a coefficient of determination of R2 = 0.83 between simulated and observed values. Then the model was applied to the whole riparian buffer zone catchment, using the spatial resolution (10 m) of the SPOT-5 image. Model sensitivity analysis showed that soil moisture was the most sensitive parameter for gaseous N emissions and soil denitrification was the main process affecting N losses to the atmosphere in the riparian area. From the aspect of land use management around the Guanting reservoir, the spatial structure and distribution of land cover and land use types in the riparian area should be adapted, to enhance faster ecological restoration of the wetland ecological system surrounding this strategically important water resource.  相似文献   

14.
This paper reports the results of laboratory study performed on expansive soil reinforced with geofibers and demonstrates that discrete and randomly distributed geofibers are useful in restraining the swelling tendency of expansive soils. Swelling characteristics of remoulded expansive soil specimens reinforced with varying fiber content (f = 0.25% and 0.50%) and aspect ratio (l/b = 15, 30 and 45) were studied. One-dimensional swell-consolidation tests were conducted on oedometer specimens. Reduction in heave and swelling pressure was the maximum at low aspect ratios at both the fiber contents of 0.25% and 0.50%. Finally, the mechanism by which discrete and randomly distributed fibers restrain swelling of expansive soil is explained with the help of soil–fiber interaction.  相似文献   

15.
This paper presents data obtained from a series of laboratory plate load tests performed on geogrid-reinforced sand beds. Fine, medium and coarse sands were used as test sand beds. Circular geogrids of diameter 120 mm were used as reinforcement layers. Improvement in load–settlement response was studied. The test sand beds were compacted to a relative density of 50%. A surface footing plate of diameter 60 mm was used as the shallow foundation. It was found that the horizontal geogrid reinforcement improved the load–settlement response. The applied load for a deformation of 0.5 mm in the case of geogrid-reinforced fine sand, medium sand and coarse sand was, respectively, 83 N, 44 N and 87 N, whereas it was 63 N, 38 N and 47 N when the sands were unreinforced. Load–settlement response was found to improve further with increase in number of geogrid layers and with decrease in spacing between them. Load improvement ratio (LIR), defined as the ratio of load for a given settlement in geogrid-reinforced case to that for the same settlement in unreinforced case, increased with number of geogrids (n) for all sands, but the improvement was significant in the case of coarse sand.  相似文献   

16.
Wood is a hygroscopic material and has ability to exchange its moisture content with air. Many mechanical properties are affected by changes in moisture content below the fiber saturation point of wood. This study evaluates the formaldehyde emission and some mechanical properties of poplar and spruce plywood panels manufactured from rotary cut veneers having different moisture content by using urea–formaldehyde (UF) and modified urea formaldehyde by melamine (M+UF). Rotary cut veneers obtained from poplar and spruce logs were classified into three groups and veneers in each group were then conditioned in a climate chamber to either 4–6%, 10–12% or 16–18% moisture content. Plywood panels with three plies and in 6 mm thickness were manufactured for each group. Formaldehyde emission, shear strength, bending strength and modulus of elasticity values of plywood panels were determined. Best bonding results were obtained in plywood panels with veneers having 4–6% moisture content. Lowest mechanical properties were found for plywood panels manufactured from veneers conditioned to 16–18% moisture content. Formaldehyde emission values of poplar and spruce plywood panels decreased with increasing veneer moisture content for both glue types. Formaldehyde emission content of panels decreased with melamine addition into the urea formaldehyde glue mixture.  相似文献   

17.
This paper reports the potential of heterogeneous photocatalysis as an advanced oxidation technology for removal of toluene from air using TiO2 as a photocatalyst in building materials. First, the photocatalytic activity of two types of TiO2 containing building materials, i.e. roofing tiles and corrugated sheets, has been investigated at ambient conditions (T=25.0 °C; relative humidity RH=47%; toluene inlet concentration [TOL]in=17–35 ppbv). Toluene removal efficiencies up to 63% were observed at a gas residence time (τ) of 17 s. Second, the effect of RH (1–77%), [TOL]in (23–465 ppmv) and τ (17–115 s) on toluene removal has been systematically investigated using TiO2 containing roofing tiles as photocatalytic building materials. Results revealed lower toluene removal efficiencies at higher RH and [TOL]in, whereas a positive effect was observed with increased τ. Under optimal conditions, toluene removal efficiencies up to 78±2% and elimination rates higher than 100 mg h−1 m−2 roofing tile were obtained. A decline in photocatalytic activity by a factor of 2 was observed after operation at gas residence times shorter than 69 s and [TOL]in higher than 76 ppmv. Washing the building materials with deionized water, simulating rainfall, could partially (i.e. by a factor 1.3) regenerate the catalyst activity.  相似文献   

18.
An exponential formula is used to best-fit theoretical and measured time–settlement (or excess pore pressure) data over the full range of consolidation. The formula fits well theoretical consolidation solutions and measured data regardless of using the incompletely consolidated data, and it is possible to reliably predict the ultimate values. This result has a different trend from those of the hyperbolic and Asaoka (1978) methods. Thus the coefficients of horizontal consolidation and the mobilised discharge capacity qw(mob) can be expressed in terms of parameters of the exponential formula corresponding to the measured data and the theoretical solutions. The application of the proposed method to six case records on three construction sites (with a maximum drainage path lm of 7−50 m) indicates that the coefficient of horizontal consolidation for the ideal condition are likely to be used to reconstruct the monitored time–settlement curve and also to adjust the hydraulic and consolidation properties of each monitored point. Based on back-analysis, the mobilised and required discharge capacity for a preliminary design guideline are recommended as: qw(mob) = (1–5)khlm2 and qw(req) = 19.63khlm2, where kh is the horizontal permeability of soil.  相似文献   

19.
Soil contamination due to petroleum-derived products is an important environmental problem. We assessed the impacts of diesel oil on plants (Trifolium repens and Lolium perenne) and soil microbial community characteristics within the context of the rhizoremediation of contaminated soils. For this purpose, a diesel fuel spill on a grassland soil was simulated under pot conditions at a dose of 12,000 mg diesel kg− 1 DW soil. Thirty days after diesel addition, T. repens (white clover) and L. perenne (perennial ryegrass) were sown in the pots and grown under greenhouse conditions (temperature 25/18 °C day/night, relative humidity 60/80% day/night and a photosynthetic photon flux density of 400 μmol photon m− 2 s− 1) for 5 months. A parallel set of unplanted pots was also included. Concentrations of n-alkanes in soil were determined as an indicator of diesel degradation. Seedling germination, plant growth, maximal photochemical efficiency of photosystem II (Fv/Fm), pigment composition and lipophylic antioxidant content were determined to assess the impacts of diesel on the studied plants. Soil microbial community characteristics, such as enzyme and community-level physiological profiles, were also determined and used to calculate the soil quality index (SQI). The presence of plants had a stimulatory effect on soil microbial activity. L. perenne was far more tolerant to diesel contamination than T. repens. Diesel contamination affected soil microbial characteristics, although its impact was less pronounced in the rhizosphere of L. perenne. Rhizoremediation with T. repens and L. perenne resulted in a similar reduction of total n-alkanes concentration. However, values of the soil microbial parameters and the SQI showed that the more tolerant species (L. perenne) was able to better maintain its rhizosphere characteristics when growing in diesel-contaminated soil, suggesting a better soil health. We concluded that plant tolerance is of crucial importance for the recovery of soil health during rhizoremediation of contaminated soils.  相似文献   

20.
The precipitation chemistry, deposition, nutrient pools and composition of soils and soil water, as well as an estimate of historical deposition of sulphur (S) and inorganic nitrogen (N) for the period 1860-2008, were determined in primeval deciduous and coniferous forests at the sites Javornik and Pop Ivan, respectively. Measured S throughfall inputs of 10 kg ha− 1 year− 1 in 2008 were similar to those estimated for the period 1900-1950 at both sites. The highest estimated S inputs were in the 1980s. Measured bulk deposition of N in 2008 was lower at Pop Ivan (5.6 kg ha− 1 year− 1) compared to Javornik (12 kg ha− 1 year− 1). Significantly lower NO3 deposition was both estimated and measured at Pop Ivan. Higher soil base cation concentrations were observed at well-buffered Javornik underlain by flysch (Ca pool of 2046 kg ha− 1 and base saturation of 29%) compared to Pop Ivan underlain by crystalline schist (Ca pool of 186 kg ha− 1 and base saturation of 6.5%). The soil pool of organic carbon (C) was higher at Pop Ivan (212 t ha− 1) compared to Javornik (127 t ha− 1). The C concentration was positively correlated with organic N in the soil (p < 0.001) at both sites, but the mass average C/N ratio in the forest floor was lower at Javornik (22) than at Pop Ivan (26). High N leaching of 17 kg ha− 1 year− 1 at the 90 cm depth was measured in the soil water at Javornik, suggesting high mineralization and nitrification rates in old growth deciduous forests in the area. Despite relatively low Al concentrations in the soil water, a low soil water Bc/Al ratio (0.9) (Bc = Ca + Mg + K) was found in the upper mineral soil at Pop Ivan. This suggests that the spruce forest ecosystems in the area are vulnerable to anthropogenic acidification and to the adverse effects of Al on forest root systems.  相似文献   

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