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1.
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   

2.
Determination of ochratoxin a with a DNA aptamer   总被引：2，自引：0，他引：2  
This work describes the identification of an aptamer that binds with high affinity and specificity to ochratoxin A (OTA), a mycotoxin that occurs in wheat and other foodstuffs, and a quantitative detection method for OTA based on the use of this aptamer. Aptamers are single-stranded oligonucleotides selected in vitro to bind to molecular targets. The aptamer selected in this work exhibited a dissociation constant in the nanomolar range and did not bind compounds with structures similar to OTA such as N-acetylphenylalanine or warfarin. The aptamer bound with a 100-fold less affinity to ochratoxin B. The selected aptamers could be used for the determination of ppb quantities of OTA in naturally contaminated wheat samples. Further work is ongoing to broaden the application demonstrated here with the development of sensors, affinity columns, and other analytical systems for field and laboratory determination of this toxin in food and agricultural products.  相似文献   

3.
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   

4.
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5.
The input of heavy metals by automobile exhaust pollution associated with the ski basin activities is the primary concern of this paper. Stream, snowpack and lichen samples were collected and analyzed for Pb, Zn, and Cu. Some lichen samples were also analyzed for Ca, Mg, Na, K, Fe, and Mn, as well as Pb, Zn, and Cu. Snowpack samples from roadside areas demonstrated increased levels of Pb and Cu in comparison to areas up to 180 m from the road, but heavy metal levels at more remote areas were comparable to roadside levels. In all snow samples the heavy metals associated with the particulate matter was the major form of all inputs. Heavy metals in streams were also highly correlated with the particulate matter content. Heavy metal inputs to the watershed were greater than stream export, indicating an accumulation of heavy metals by the system. The forest canopy appears to be the major factor in the accumulation of heavy metals, probably due to better interception and impaction of the particulate matter by the canopy.  相似文献   

6.
A molecular technique for the identification of the Gigaspora margarita isolate CK based on the detection of a DNA sequence of 235 bp as its diagnostic marker was evaluated to investigate the survival and establishment of introduced arbuscular mycorrizal fungi (AMF) in a field ecosystem. In March 2001, roots and rhizosphere soil of Eragrostis curvula and Miscanthus sinensis were collected from the Mizunashi River at Mt. Fugendake (Nagasaki Prefecture, Japan), where plant seeds and AMF including G. margarita CK had been introduced for reforestation after the occurrence of repeated pyroclastic flows. We detected the marker sequence from DNA preparations of E. curvula roots and Gigaspora spores in the rhizosphere. This clearly showed that the isolate occurred at both hyphal and sporal stages. It was shown that the isolate survived and developed a life cycle in the revegetation area for 4 years. It was confirmed that the method was effective for tracing the isolate in samples collected from field ecosystems.  相似文献   

7.
The photosynthetic light curves of eight Scots pine (Pinussylvestris L.) shoots, each with a different structure, were measured in a direct radiation field at different positions relative to the radiation beam. Using a model of shoot geometry, the irradiance distributions on the needle surface area of the same shoots were simulated in each position. Using measurements of shoot photosynthesis, the photosynthetic light curve for a needle surface area element (a small area on the needle surface) was estimated indirectly for each shoot. Shoot photosynthesis was then calculated from the estimated photosynthetic light response curve of a needle surface area element and the irradiance distribution on the surface area of needles. Calculated rates for shoot photosynthesis agreed well with the measured rates. The mean irradiance on the needle surface area was the major component causing variation in the light response of a shoot irradiated from different directions, but the shape of the irradiance distribution on the needle surface area had a considerably smaller effect.  相似文献   

8.
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   

9.
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   

10.
Understanding metapopulation dynamics in large carnivores with naturally fragmented populations is difficult because of the large temporal and spatial context of such dynamics. We coupled a long-term database of visitor sighting records with an intensive 3-year telemetry study to describe population dynamics of recolonization by black bears (Ursus americanus) of Big Bend National Park in Texas during 1988-2002. This population, which occurs within a metapopulation in western Texas and northern Mexico, increased from a single pair of known breeding-age animals in 1988 to 29 bears (including 6 females of breeding age) in March 2000 (λ = 1.25/year). A migration and dispersal event in August-December 2000 reduced the population to 2 adult females and as few as 5-7 individuals. One-way movement distances from the study area during this event averaged 76 km for females (n = 7) and 92 km for males (n = 4), and 3 animals conducted migrations of at least 154, 178, and 214 km, respectively. Our observations exemplify the importance of stochastic events on demographics of small populations and highlight the potential scale of bear movement among montane islands of southwestern North America. They also provide insight into the use of dispersal data in parameterizing metapopulation models for large carnivores.  相似文献   

11.
A chitosanolytic enzyme was purified from a commercial ficin preparation by affinity chromatographic removal of cysteine protease on pHMB-Sepharose 4B and cystatin-Sepharose 4B and gel filtration on Superdex 75 HR. The purified enzyme exhibited both chitinase and chitosanase activities, as determined by SDS-PAGE and gel activity staining. The optimal pH for chitosan hydrolysis was 4.5, whereas the optimal temperature was 65 degrees C. The enzyme was thermostable, as it retained almost all of its activity after incubation at 70 degrees C for 30 min. A protein oxidizing agent, N-bromosuccinimide (0.25 mM), significantly inhibited the enzyme's activity. The molecular mass of the enzyme was 16.6 kDa, as estimated by gel filtration. The enzyme showed activity toward chitosan polymers exhibiting various degrees of deacetylation (22-94%), most effectively hydrolyzing chitosan polymers that were 52-70% deacetylated. The end products of the hydrolysis catalyzed by this enzyme were low molecular weight chitosan polymers and oligomers (11.2-0.7 kDa).  相似文献   

12.
Abstract. We investigated whether a polyacrylate polymer could be used to remediate a soil which had been contaminated with copper for many years. Perennial ryegrass was grown in a loamy sand containing 230 mg ammonium-acetate-EDTA extractable Cu kg−1 and amended with 0, 0.1 and 0.2% of polymer. Growth of perennial ryegrass was stimulated in the polymer-amended soil, especially in the soil with 0.1% of polymer. After plant growth for 177 days, the amount of water extractable copper present in the unamended soil was 17 times that of the original soil. In the soil amended with 0.1% of polymer the level of copper after plant growth was only 0.11 times the amount present in the unamended soil. When the soil was incubated with polymer in the absence of plants, the level of water extractable copper was not reduced. The polymer seems to compete with plants for copper, and to prevent the increase of copper in soil solution brought about by root exudates.  相似文献   

13.
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   

14.
Several authors have pointed out the need to improve the design procedure of conventional oil-water separator. In this work, a batch test and various continuous runs based on a Plackett-Burman statistical plan were performed, in order to optimize a small (10 L/min) gravity oil-water separator technology intended to pre-treat wastewaters from vehicle service facilities. The results from the tracer tests realized did not show a coherent relationship between the performance of the separator (E) and the mixing regime qualified by means of the variable ε (ratio between the actual and nominal mean residence times). The statistical analysis showed that the oil removal efficiency variations (69-82%) were mainly dictated by the way the separator is configured. A two-step design procedure alternative of small gravity separators was suggested.  相似文献   

15.
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   

16.
There is a need to develop a rapid and sensitive method to detect spectinomycin residues in animal tissues. A latex fluorescent immunoassay was designed using reagents developed for this assay. The spectinomycin antibody was produced in sheep, and the immunoglobulin (IgG) was purified through a Protein G affinity column and was immobilized onto latex particles. Spectinomycin was labeled with 5-([4,6-dichlorotriazin-2-yl]amino)fluorescein (DTAF). The optimum assay conditions consisted of preincubating the latex-IgG with spectinomycin in buffer solutions or in bovine kidney extracts. DTAF-spectinomycin was added and was further incubated. The bound spectinomycin-DTAF/IgG-latex complex was separated by centrifugation at 4000 g for 10 min. The fluorescence signals of the unbound spectinomycin-DTAF in the supernatant were measured at 485/535 nm excitation/emission. The measured signals were directly proportional to the concentration of spectinomycin in the samples, and spectinomycin was detected at 0-100 ppb with minimum detectability of 5 ppb. The mean regression correlation of four trials in buffer was 0.936 when the % bound complex vs spectinomycin concentration was plotted. Analysis of the kidney extract spiked with 0-100 ppb spectinomycin had a regression correlation of 0.959. This assay provides a rapid screening method for low ppb detection of spectinomycin.  相似文献   

17.
Owliaie  H. R.  Adhami  E.  Ghiri  M. Najafi  Shakeri  S. 《Eurasian Soil Science》2018,51(12):1447-1461
Eurasian Soil Science - A litho-toposequence of soils in a semi-arid region in southwestern Iran was investigated for their pedological properties. Nine representative pedons on different...  相似文献   

18.
The dependency of experimental microbial growth data on the concentration of a major substrate component in phase space follows the law of a deformed bell curve and, until now, has not had a widely accepted rational. In the present work, a theoretical equation of this dependency at a fixed time was derived from the equation of the dependency of growth on time for a single concentration of a major component, which was previously obtained using a non-stationary non-equilibrium approach. The validity of the equation was established by comparison to experimental data from an independent source. The equation allows one to find intervals in the phase space of the dependency of growth on the initial concentration of the major component of the substrate that qualitatively vary by sign (plus or minus) and direction (increasing or decreasing) of the change of: a) growth, b) rates, and c) acceleration of its change in response to the change in the concentration of a major component of the substrate.  相似文献   

19.
Disposition kinetic behavior and metabolism studies of metamitron and its metabolite in terms of the parent compound were carried out in black Bengal goats after a single oral administration of a nontoxic oral dose at 30 mg kg(-1) of body weight. Metamitron was detected in the blood sample at 5 min (2.23 +/- 0.04 microg mL(-1)), maximum at 1 h (3.43 +/- 0.02 microg mL(-1)) and minimum at 12 h (0.41 +/- 0.01 microg mL(-1)), after a single oral administration. Metabolite [3-methyl-6-phenyl-1,2,4-triazin-5(4H)-one] in terms of the parent compound was detected in the blood sample at 5 min (0.47 +/- 0.006 microg mL(-1)), maximum at 6 h (5.12 +/- 0.02 microg mL(-1)) and minimum at 96 h (1.06 +/- 0.016 microg mL(-1)), after a single oral administration. The t(1/2 K) and Cl(B) values of metamitron were 3.63 +/- 0.05 h and 1.36 +/- 0.016 L kg(-1) h(-1), respectively, whereas the t(1/2K)(m) and Cl(B)(m) values of the metabolite were 38.15 +/- 0.37 h and 0.091 +/- 0.001 L kg(-1) h(-1), respectively, which suggested long persistence of the metabolite in blood and tissues of goat. Metamitron was excreted through feces and urine for up to 48 and 72 h, whereas the metabolite was excreted for up to 168 and 144 h, respectively. Metabolite alone contributed to 96 and 67% of combined recovery percentage of metamitron and metabolite against the administered dose in feces and urine of goat, respectively. All of the goat tissues except lung, adrenal gland, ovary, testis, and mammary gland retained the metabolite residue for up to 6 days after administration.  相似文献   

20.
In China, great efforts are being made to remediate farmlands polluted by heavy metals. In this study, a soil pot experiment was conducted to examine the effects of a new-type cleaning agent, methylglycinediacetic acid(MGDA), and a plant growth regulator(PGR), diethl aminoethyl hexanoate(DA-6), on plant growth and extraction and detoxification of cadmium(Cd) by ryegrass. The results showed that foliar spray of DA-6 alone improved plant growth, with root length and shoot dry biomass increased by 38.5%–58.6% and 71.1%–89.3%, respectively, whereas addition of MGDA alone decreased root length and shoot dry biomass by 10.3%–18.6%and 9.1%–21.8%, respectively. Diethl aminoethyl hexanoate promoted the binding of Cd to cell walls and thus alleviated the toxicity of Cd and/or MGDA to plants. Applications of DA-6 and/or MGDA resulted in a significant increase in Cd extraction efficiency(P 0.05), and the efficiency decreased in the order of MGDA + DA-6 DA-6 MGDA. The treatment of MGDA + DA-6 achieved 2.2%, 1.7%, and 0.8% Cd extraction efficiency by ryegrass in soils spiked with 25, 50, 100 mg Cd kg~(-1), respectively. Therefore,treatment of MGDA + DA-6 could be an efficient method for enhancing phytoremediation of Cd-contaminated soil by ryegrass.  相似文献   

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