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1.
A two-year study was carried out in the lower part of the Palmones River to describe the role of a small dam controlling the nutrient fluxes to the estuary. Results showed an important spatial heterogeneity in the nutrient content and water properties of lowland catchment due to the effects of the small dam and the effluents of a sewage treatment work. Taking into account the values of hydraulic retention time, the dam could be considered as an optimally dimensioned pre-dam. Therefore, it removed on average more than 25% of total phosphorus (TP) while no net removal was obtained for TN during the studied period. Palmones River exported 11.3 TonsP year?1 of TP and 72.1 TonsN year?1 of TN to the estuary showing important seasonal differences. Less than 10% from the total amount of nutrient was exported during low flow conditions, while in four months with important flooding events, the percentage of total nitrogen exported exceeded 64%.  相似文献   

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3.
The sequestration of carbon (C) in soil is not completely understood, and quantitative information about the amounts of organic carbon in the various fractions and their rates of turnover could improve understanding. We aimed (i) to quantify the amounts of C derived from maize at various depths in the soil in a long‐term field experiment with and without fertilization using 13C/12C analysis, (ii) to model changes in the organic C, and (iii) to compare measured and modelled pools of C. The organic C derived from the maize was measured in soil samples collected to a depth of 65 cm from four plots, two of which had been under continuous maize and two under continuous rye during long‐term field experiments with NPK and without fertilization. The fractionation procedures included particle‐size fractionation and extractions in water and in pyrophosphate solution. We used the Rothamsted Carbon Model to model the dynamics of the carbon from 13C data. The amounts of C derived from maize in the Ap horizon after 39 years of continuous maize cropping were 9.5% of the total organic C (where unfertilized) and 14.0% where NPK had been applied. Fertilization did not affect the residence time of carbon in the soil. The amounts of C derived from maize in water extracts were 21% of the total organic C (where unfertilized) and 22% where NPK had been applied. The extracts that were soluble in pyrophosphate and insoluble in acid were depleted in C from maize (the amounts were 5% and 7% of the total organic C, respectively). The results of the 13C natural abundance technique were used to model the dynamics of the organic C. Both the total organic C and the C derived from maize in the particle‐size fraction 0–63 μm agreed well with the total and maize‐derived sums of the model pools ‘inert organic matter’, ‘humified organic matter’ and ‘microbial biomass’. The model suggested that 64% (unfertilized) or 53% (NPK) of the organic C in the Ap horizon were inert. Only one of three published equations to determine the size of the inert pool agreed well with these model results.  相似文献   

4.
Summary A bis-(p-nitrophenyl) phosphatase (BPN-Pase) was extracted from a forest soil and fractionated by DEAE-cellulose column chromatography into seven fractions (1, 2, 3, 4, 5, 6 and 7). The main fraction (fraction 5) was further fractionated into 3 subfraction (fractions 1, 2 and 3) by affinity chromatography for nuclease. The properties of the BPNPase in subfraction 3 were characterized and the results are reported in this article. Subfraction 3, which had a peak at about 278 run in the UV absorption spectrum, hydrolyzed 2,3-cyclic-nucleotides more readily than 3,5-cyclicnucleotides, adenylyl-(3 5)uridine, uridylyl-(3 5)adenosine, thymidine 3-p-nitrophenyl phosphate, thymidine 5-p-nitrophenyl phosphate, p-nitrophenyl phosphate and BPNP. Subfraction 3 hydrolyzed BPNP into 2 mol p-nitrophenyl and 1 mol inorganic phosphate during incubation. Apparent molecular weight of the BPNPase was estimated to be about 58 000 by gel filtration. The BPNPase activity had a pH optimum at 5.0 and was inhibited by Hg2+ and slightly inhibited by F– and PO 4 3– .These observations suggest that the BPNPase is subfraction 3 has been constituted mainly with 2,3cyclic-nucleotide 2-phosphodiesterase [EC 3.1.4.16] or 2,3-cyclic-nucleotide 3-phosphodiesterase [EC 3.1.4.37].  相似文献   

5.
A quasi steady state respiration test based on Fick’s law with a correction term for advective flux, for estimating petroleum hydrocarbon degradation rates, was evaluated in a full-scale (3,000 m3) biopile study. A contaminated clayey sand soil with an average TPH content of 1,421?±?260 mg kg?1 soil was treated in a biopile with a fixed venting and heating system. Temperature in the biopile ranged from 12.1 to 36.6°C and soil water content from 15.2 to 35.8 m3 H2O m?3 soil. Oxygen concentrations in the biopile showed a rapid decrease with depth, before venting and reached constant atmospheric concentration during venting. Measured oxygen consumption in the biopile ranged from ?0.04 to ?0.68 mol O2 m?3 soil day?1. Average oxygen consumption rates calculated with the quasi-steady-state method were significantly (P?<?0.05) lower then the oxygen consumption rates calculated with the transient method. It was suggested that the oxygen diffusion was underestimated by the diffusivity models used and that further research is needed to determine relative effective diffusion coefficients in biopiles. Although both respiration testing and petroleum hydrocarbon concentration showed a decrease of oxygen consumption in time, the estimated degradation rate was low compared to the actual decrease in petroleum hydrocarbon concentration. Additional work will have to be done to acquire a more precise knowledge of the relationship between respirometrically determined degradation rates and the actual change in petroleum hydrocarbon concentration in the soil.  相似文献   

6.
The capacity of different microbial groups to recolonise soil after a fire event will be decisive in determining the microbial community after the fire. Microbial recovery after a wildfire that occurred in Sierra la Grana (Alicante province, southeast Spain) was tracked for 32 months after the fire. Colony forming units (CFUs) of different microbial groups, microbial biomass, soil respiration, bacterial growth (leucine incorporation) and changes in the microbial community structure (phospholipid fatty acid (PLFA) analysis) were determined directly after the fire and four times during the recovery period. Direct effects were reflected by low values of most microbiological variables measured immediately after the fire. Microbial biomass increased during the first year after the fire but was below the unburned reference site 32 months after the fire. Bacterial activity and soil respiration showed the highest values immediately after the fire, but decreased to values similar to that of the unburned reference site or even lower (respiration) 32 months after the fire. Colony forming units of bacterial groups estimated by the plate count method peaked 8 months after the fire, but then decreased, showing values similar to the unburned reference site at the end of the study, with the exception of spore formers, which were 20 times higher than the reference site 32 months after the fire. Fungal CFUs were more sensitive to the fire and recovered more slowly than bacteria. Fungi recovering less rapidly than bacteria were also indicated by the PLFA pattern, with PLFAs indicative of fungi being less common after the fire. The recovery of microbial biomass and activity was mirrored by the initially very high levels of dissolved organic carbon being consumed and decreasing within 8 months after the fire. The wildfire event had thus resulted in a decrease in microbial biomass, with a more bacteria-dominated microbial community.  相似文献   

7.
Abstract

The movement of water from the watertable to the atmosphere is one of the most common causes for CaCO3 accumulation on top of the soil. In the Flooding Pampa, the increase in water evaporation due mainly to the reduction of soil cover as a result of grazing has given place to pulses of topsoil salinization. We investigated the influence of this process on lime precipitation in the upper horizon. Data from continuous grazed and ungrazed areas were considered. The relative ion concentrations in the upper horizon of the ungrazed area and in the phreatic water were very similar. Under grazing, absolute ion concentration was larger than in the water table. The anionic constituents did not increase directly and linearly. Chlorides and sulfates showed increments. The carbonate proportion did not change, but bicarbonates showed a relative decrease. This latter reduction could be related to the precipitation of CaCOs in the uppper horizon of the soil. In agreement, the Ion Activity Product (IAP) of the calcite of the soil solution indicated conditions for saturation of CaCO3 in the grazed area. Conversely, the IAP showed CaCO3 undersaturation in the ungrazed area. In spite of the evidence for the ocurrence of lime precipitation, the top horizon did not show measurable lime under grazing. This fact could be explained by considering both the usual time taken by CaCO3 precipitation, and the recent and episodic process of top soil salinization in this region after the introduction of livestock.  相似文献   

8.
Soils of former coking plant sites are frequently contaminated with cyanide, which mainly occurs as the pigment Berlin blue, FeIII4 [FeIICN)6]3, and soluble iron cyanide complexes, Fe(CN)63-/4?. Berlin blue is only slightly soluble under acidic conditions. The cyanide mobility in a strongly acid soil (pH about 3) of such a site was studied by assessing the distribution of cyanides in the soil and sediment and by conducting batch experiments at different pH levels. The soil is based on a disposal layer (0–32 cm) overlying sandy loess (32–145 cm) overlying glaciofluvial sand (145–250 cm) overlying marlstone (250–500 cm). Highest cyanide concentrations were found in the disposal layer (62–2865 mg CN? kg?1), medium concentrations in the sandy loess (16–29 mg CN? kg?1), concentrations of about 100 mg CN? kg?1 in the glaciofluvial sand and lowest concentrations in the marlstone (0.22–0.49 mg CN?1 kg?1). The surfaces of macropores, which occur in the sandy loess and finish in the glaciofluvial sand, are dark-blue dyed and have much higher cyanide concentrations than the surrounding bulk soil. Thus, the accumulation of cyanides in the sand layer may partly be the result of macropore flow. Batch experiments show a strong pH dependence of the solubility of cyanide in the soil as well as of Berlin blue which was found by Mössbauer spectroscopy to be the dominating or sole iron cyanide. The time necessary to transport the cyanides solely as hexacyanoferrate into the undisturbed horizons is estimated to 1000 yr. However, because Berlin blue is known to form colloids, we discuss the possibility of cyanide transport as colloid not requiring dissolution and reprecipitation. We postulate that colloidal Berlin blue transported by macropore flow is responsible for the high mobility of cyanides in this acid soil.  相似文献   

9.
An experimental microcosm has been designed for simulating and studying impacts of a wastewater treatment plant (WTP) discharge on a freshwater/sediment ecosystem. The study was focused on the changes in biodiversity of benthic populations, especially bacteria and oligochaetes. Effluents were discharged in the Saône river, near Lyon (France) from a small treatment plant which treated domestic raw water by an activated sludge process. Freshwater and sediments were sampled in the Saône river upstream of the discharge point and placed in microcosms. Following the WTP discharge, physicochemical parameters of the overlying water column and sediments exhibited only a slight change, as compared to a reference. Characterization of the sediment bacterial populations was conducted with the Biolog and API systems. Strain identification and interpretation of data was difficult using thesetwo systems. Bacterial taxa in the sediments increased slightly below the WTP discharge. Gram negative strains dominated in the effluents, but G+ and G- bacteria were balanced in the sediments. Pseudomonas sp. and Bacillus sp., were the dominant strains. Invertebrate populations indicated an effect of the WTP discharge, with increasing of pollution resistant strains (Tubificidae) and disappearance of pollution intolerant strains such as Limnodrilus udekemianus and Quistadrilus multicoetosus. Taken as a whole, biological parameters indicated an environmental changes despite only slight changes in the physicochemistry of water. This experimental microcosm has proven to be a useful tool for studying impact of wastewater discharge on benthic populations.  相似文献   

10.
Although the shrink‐swell phenomenon of clays has been thoroughly studied, the in situ relation of the shrinkage curve to the structure profile is rarely presented from the shrinkage limit to the liquid limit. We studied the consolidated structure of clay‐dominated (<2 μm) soils formed on ‘pseudo‐liquid’ marsh sediments in the ‘Marais de l’Ouest’ (France). The profiles were studied in a grassland field and in a sunflower field from unsaturated surface soils down to deeper, saturated, levels characterized by a very large water content (100% by weight). The consolidation states were quantified recording cone resistance (Qd) profiles using a dynamic penetrometer in successive seasons. These Qd profiles were compared with the associated wet density and gravimetric water‐content profiles. Two consolidation depths were evident, the surface soil and a 130‐cm deep palaeosol. The seasonal Qd profiles demonstrate the partial irreversibility of the consolidation peaks associated with the surface soil and with the palaeosol. The shrinkage properties were established through drying curves of undisturbed test samples. In the void ratio (e)‐water content (W) and water content (W)‐saturation index (Sr) diagrams, the profiles as a whole exhibit only one clay soil behaviour from their pseudo‐liquid to plastic to solid states. Each Qd profile is represented by a hyperbolic curve in the e/Qd diagram. Represented in a (e – W – Qd —Sr) crossed diagram, the vertical evolution of the successive profiles shows the soil structure behaviour from the initial pseudo‐liquid sediment to the consolidated soil. A simple cone resistance recording associated with gravimetric water‐content profiles, characterizes the evolution of structural layers of soils for the seasonal drying‐wetting cycles, for the over‐consolidation associated with the palaeosol, and also for the effect of ploughing.  相似文献   

11.
Chemical and spectroscopic characteristics were determined on the organic matter in two Luvisolic soils from northwestern Alberta, Canada. One of these (the Debolt soil) is known to crust only slightly while the other (the Demmitt soil) exhibits severe crusting after heavy rainfalls. The Debolt top soil is richer in total C, total N, carbohydrates and proteinaceous materials than the Demmitt top soil. Humic acid extracted from the Debolt soil is more aliphatic, and contains fewer CO2H groups than does humic acid extracted from the Demmitt soil. The quality of the organic matter appears to play a role in soil crusting.  相似文献   

12.
The paper presents the results of a study in the region Dübener Heide (Central Germany) testing the suitability of field measurements of magnetic susceptibility for the detection of historical fly-ash deposition. The measurements supported the verification of historically documented deposition zones along an emission gradient. Mean values, standard deviation, and coefficient of variation can be used to characterize the former deposition zones, although the study revealed several problems, which will be the subject of future work: (1) the volume susceptibility measurements used in the study do not allow the calculation of the actual fly-ash amount stored in the soil and thus must be calibrated with correction factors from laboratory measurements; and (2) measurements in regions with similar conditions but without fly-ash deposition are needed to obtain reference values for the natural range of magnetic susceptibility.  相似文献   

13.
Hyperspectral remote sensing for monitoring horticultural production systems requires the understanding of how plant physiology, canopy structure, management and solar elevation affect the retrieved canopy reflectance during different stages of the phenological cycle. Hence, the objective of this study was to set up and to interpret a hyperspectral time series for a mature and healthy citrus orchard in the Western Cape province of South Africa considering these effects. Based on the remotely sensed data, biophysical parameters at the canopy level were derived and related to known observed physiological and phenological changes at the leaf level and to orchard management. Fractions of mature fruit, flowers, and sunburnt leaves were considered, and indices related to canopy structure chlorophyll content and canopy water status were calculated.Results revealed small cover fractions of mature fruit, flowers and sunburnt leaves of respectively 2.1%, 3.1% and 7.0%, but the high spectral contrast between flowers and leaves allowed a successful classification of flowering intensity. Furthermore, it was shown that canopy level time series of vegetation indices were sensitive to changes in solar elevation and soil reflectance which could be reduced by applying an empirical soil line correction for the most affected indices. Most trends in vegetation indices at the canopy level could be explained by a combination of changes at the leaf level (chlorophyll, carotenoids, dry matter), changes in canopy structure (leaf area index and leaf angle distribution) and changes in cover fractions of vegetative flushes, flowers and sunburnt leaves. The transformed chlorophyll absorption ratio index over the optimised soil adjusted vegetation index (MCARI/OSAVI) was best related to leaf level trends in chlorophyll content. Seasonal changes in the photochemical reflectance index (PRI) were linked to inverse changes in the carotenoid-to-chlorophyll ratio. Canopy structure indices (the modified triangular vegetation index or MTVI2 and the standardized leaf area index determining index or sLAIDI) were sensitive to changes in leaf area index, average leaf angle as well to management interactions (pruning and harvest). Canopy water status was highly impacted during the spring flush due to expanding leaves that concealed trends in the underlying mature leaves. Seasonal trends in soil and weeds reflectance were related to changes in volumetric soil water content and to the earlier and reduced growth period of non-irrigated weeds.  相似文献   

14.
The environmental conditions of plants grown in a glasshouse were controlled by a minicomputer (IBM-Series 1). The simulation model thus developed provides better analyses of the relationship between yield increase and control of environmental factors.The glasshouse used was in several sections, with all the necessary devices for controlling environmental conditions. Two different climatic regimes were stimulated in order to find a better agreement of simulated values with experimental data.The computer used can be applied to a system comprising several glasshouses where different crops are grown.  相似文献   

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16.
Soils and housedusts were collected from three areas of Pribram,an historic metal mining and smelting town in the Czech Republic. The main objectives of the study were: (i) to assessthe influence of physico-chemical form, particle size, soilproperties and contaminant source on Pb bioavailability andexposure risk; (ii) compare the Pb bioavailability data obtainedfrom the mining and smelting areas and assess whether anydifferences observed could be attributed to the factors thoughtto exert an influence. Lead concentrations were highest in thesmelter area. Mining area garden soils also contained elevatedPb concentrations. Solubility of housedust Pb in 0.12 M HCl (asurrogate for stomach acid) was similar in all study areas andwas similar to values reported in the literature. However, 0.12M HCl solubility of garden soil Pb was low in the mining areacompared to the other study areas and compared to other urbanareas. Blood Pb concentrations were also relatively low in themining area compared to the other study areas and the reducedsoil Pb solubility observed in this area was suspected as aninfluencing factor. However, exposure pathways may also beimportant in explaining the differences observed.  相似文献   

17.
Machine Vision for a Micro Weeding Robot in a Paddy Field   总被引：3，自引：0，他引：3  
The study developed an image processing method to determine the travel directrix for a micro weeding robot in a paddy field. The processing samples, which included 24 images in each sample, were selected from the videotapes which were obtained on a weekly basis, when the camera manually revolved 360° eight times at each height and angle position in the space between the rice rows from the third day after transplanting to 7 weeks. The target image was abstracted from the 24 images by analysing the distribution of blue pixels in the colour image and the distribution of black pixels in its binary image. The candidate points for the directrix line in the target image were obtained by analysing each horizontal line profile of its binary image or the blue image according to the level of growth in the paddy field. The travel directrix line was detected by passing a known-point Hough transform. The directrix lines of all 69 samples used in the study were correctly detected. The processing times required to draw the directrix line after reading the 24 images were about 0·4–0·8 s.  相似文献   

18.
Anion retention is important in highly weathered soils that contain large amounts of iron and aluminium oxides with surfaces of variable charge. Sorption mechanisms retard anionic solute transfer through these soils. We determined the retardation factor for nitrate in highly weathered Ferralsols from New Caledonia from dynamic experiments using a transient‐flow method, and we evaluated the effect of soil solution concentration and organic matter content. A simple method with sectionable tubes was used to determine the nitrate isotherm during non‐steady‐state water flow under unsaturated conditions. The topsoil retarded the movement of nitrate, and the sorption followed a linear isotherm. In subsoils, retardation factors were larger and increased from 1.15 to 2.05 at soil pH as the NO3–‐N concentration of the input solution decreased from 71.43 to 0.35 mm , indicative of a non‐linear isotherm. Positive surface charge sites were considered to be of two types: one with strong affinity for nitrate at small concentrations and one with weak affinity for adsorption of nitrate at larger concentrations. This type of isotherm with high‐ and low‐energy sites is similar to those found for oxyanions and heavy metals. The related anion exchange capacity was larger than that usually observed in soils of variable charge. Not all exchange sites were detected with our method, and some sites were obviously not available for nitrate retention.  相似文献   

19.
A fieldwork was carried out in Caesarea sand dunes, Israel, to determine the influence of fine-scale landscape-patch abiotic-factor heterogeneity on microbial activity in a Mediterranean region. Soil organisms in terrestrial systems are unevenly distributed in time and space, and are often aggregated. Spatio-temporal patchiness in the soil environment is thought to be crucial for the maintenance of soil biodiversity, providing diverse microhabitats that are tightly interwoven with resource partitioning. Determination of a ‘scale unit’ to help understand ecological processes has become one of the important and most debatable problems in recent years. To better understand the distribution of soil microbial communities at multiple spatial scales, a survey was conducted to examine the spatial organization of the community structure in two sandy soil ecosystems. One-hundred forty-four soil samples were collected from two patches 4000 m apart from each other. Basal respiration (CO2 evolution without the addition of any external substrate), microbial biomass, functional diversity, and community-level physiological profile (CLPP) in soil were measured with a MicroResp? system. Soil abiotic analysis was performed by soil standard analytical methods. The results demonstrated that bacterial distributions can be highly structured, even within a habitat that appears to be relatively homogeneous at the plot and field scale. Different subsets of the microbial community were distributed differently across the plot. This is due to spatial heterogeneity associated with soil physical, chemical, and biological properties. Although spatial variability in the distribution of soil microorganisms is generally regarded as random, this variability often has a predictable spatial structure. This study provided evidence that a spatially explicit approach to soil ecology can enable the identification of factors that drive the spatial heterogeneity of populations and activities of soil organisms, at scales ranging from meters to hundreds of meters. Furthermore, there is increasing evidence that spatial soil ecology can yield new insights into the factors that maintain and regulate soil biodiversity, as well as on how the spatial distribution of soil organisms influences plant growth and plant community structure.  相似文献   

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