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1.
Effect of land use on microbial biomass-C, -N and -P in red soils   总被引：1，自引：0，他引：1  
INTRODUCTIONTheimportanceofmicroorganismstosoilfer tilityandsoilqualityhasbeencommonlyaccept ed (Smithetal.,1 990 ;Brookes,1 995;Da lal,1 998;Wicketal.,1 998) .Soilmicrobialbiomassasanimportantmicrobialpropertyhasbeenextensivelystudiedsinceitisthelivingco…  相似文献   

2.
An incubation study was conducted to investigate the effects of metsulfuron-methyl herbicide on the soil microbial biomass in loamy sand soil. The herbicide was applied to the soil at four concentrations: control, 0.01, 0.10, and 1.00 μg·g−1 soil. Determinations of microbial biomass-C and microbial biomass-N contents were carried out 1, 3, 5, 7, 10, 15, 25, and 45 days after herbicide application. In comparison to untreated soil, the microbial biomass-C and biomass-N decreased significantly in soils treated with herbicide at concentrations of 0.1 and 1.0 μg·g−1 soil within the first 7 days of incubation. The application of metsulfuron-methyl herbicide to the soil reduced the Cmic/Corg and Nmic/Ntotal percentages, which decreased with increasing application rate of metsulfuron-methyl herbicide. Compared to the untreated control, a marked increase in the microbial biomass C: N ratio was observed in the herbicide treated soil. This effect was transitory and was significant only at the higher rates of metsulfuron-methyl. Project supported by NSFC (No. 49871044) and the Laboratory of Materials Cycling in Pedosphere, Academia Sinica.  相似文献   

3.
A series of laboratory and pot experiments carried out to examine the role of soil microbial biomass in red soils' nitrogen availability and productivity showed that soil available N (NA), dry matter yield (DMY) of ryegrass, and plant uptake of nitrogen were each closely correlated with microbial biomass-C (Cmic) or -N (Nmic), suggesting that soil microbial biomass is a very important nitrogen pool available to plants in red soils. After correction for the substrate effect, the computed turnover of the Nmic in three tested soils ranged from 63 to 250 days. Soils with low Nmic or light texture generally had higher Nmic turnover rate than those with high Nmic or heavy texture. These results showed that soils with low Nmic, microbial biomass could also play an important role in the availability of nitrogen to plants due to these soils' high turnover rate.  相似文献   

4.
A laboratory incubation experiment was conducted to study the effect of copper as cupric sulfate (CuSO4.5H2O), and lead as lead acetate (Pb (OAc)2) on the size of the microbial biomass in red soil. The metals were applied, separately at six different levels: Cu at 50, 100, 200, 300, 400, and 600 μg·g−1 soil and Pb at 100, 200, 400, 600, 800, and 1000 μg·g−1 soil. In comparison to uncontaminated soil, the microbial biomass carbon (Cmic) and biomass nitrogen (Nmic) decreased sharply in soils contaminated with Cu and Pb. The microbial biomass C:N ratio in the metal contaminated soil was observed to be considerably higher than that in untreated control. Between the two tested metals, Cu displayed greater biocidal effect on microbial biomass carbon and nitrogen than Pb, showing their relative toxicity in the order: Cu≫Pb. Project (No. 49671050) supported by National Natural Science Foundation of China. Wa’el Mohamad—Former Ph. D. Student of Zhejiang University and is working in Ministry Of Agriculture (P. O. box. 2099), Amman, Jordan.  相似文献   

5.
This study on the effect of land use on soil quality in relation to forms and toxicity of aluminum in red soils (Ultisol) in southeast China showed that in general, the extractable order for soil active aluminum by four extractants was: NaOH 0.5 mol/L > HCl 1 mol/L > NH4Ac 1 mol/L > KCl 1 mol/L . Different uses of the red soils, developed from Quarternary red clay with the similar hydrogeological environment, greatly affected the amount of active aluminum, especially the exchangeable Al3+. The order of exchangeable Al3+ (Al mg/kg) in the red soils with different land uses was: barren land (740) > tea garden (663) > peach garden (432) > citrus garden (234) > paddy soil (127). The content of water soluble aluminum in the red soils was highly sensitive to soil acidity.  相似文献   

6.
Phytoremediation is emerging as a potential cost-effective solution for remediation of contaminated soils, and bioavailability of metal in the soil for plant uptake is an important factor for successful phytoremediation. This study aimed at investigating the ability of EDTA and citric acid for enhancing soil bioavailability of Cu and phytoremediation by Elsholtzia splendens in two types of soils contaminated with heavy metals [i.e. mined soil from copper mining area (MS), and paddy soil (PS) polluted by copper refining]. The results showed that addition of 2.5 mmol/kg EDTA significantly increased the H2O extractable Cu concentration from 1.20 to 15.78 mg/kg in MS and from 0.26 to 15.72 mg/kg in PS, and that shoot Cu concentration increased 4-fold and 8-fold as compared to the control. There was no significant difference between the treatment with 5.0 mmol/kg EDTA and that with 2.5 mmol/kg EDTA, probably because that 2.5 mmol/kg EDTA was enough for elevating Cu bioavailability to the maximum level. As compared with the control, citric acid had no marked effect on both soil extractable Cu and shoot Cu concentration or accumulation. The results indicated that EDTA addition can increase the potential and efficiency of Cu phytoextraction byE. splendens in polluted soils. Project supported by the National Natural Science Foundation of China (No. 29977017) and the Science and Technology Ministry of China (No. 2002CB410804)  相似文献   

7.
Abstract

Purpose: Why do farmers not take better care of their soils? This article aims to give insight into how farmers look at soil quality management.

Design/methodology/approach: It analyses diverse land management practices and visions on soils and soil quality of ten agroecological and 14 conventional smallholder farmers in Araponga, Minas Gerais, Brazil. As agroecological farming (that is, managing soils with minimum use of external inputs) requires more complex knowledge, it is assumed that agroecological farmers would be more knowledgeable on soils compared to conventional farmers. This case study tests the hypothesis that differences in land management practices between agroecological and conventional farmers can be explained by differences in their knowledge on soils.

Findings: The hypothesis turned out to be faulty: agroecological and conventional farmers do not differ in what they know about soils, but how they use their knowledge in their farming strategy. Both groups of farmers have different but rational farming strategies.

Practical implications: Designing policies and measures to make farming more environmentally friendly and more sustainable as two-way knowledge exchange between farmers and science (and not as one-way knowledge transfer from science to farmers), to benefit from vital and context-based farmers’ knowledge and to ensure successful implementation of more sustainable land management practices.

Originality/value: By analysing farmers’ visions on soil quality management and farming strategies, this study shows that farmers’ knowledge is valuable for farmers, for scientific knowledge on soil quality management and for policies which are to be effective and adapted to the local environment.  相似文献   

8.
滨州市不同农业土地利用方式下土壤中铜的累积特征   总被引：2，自引：0，他引：2  
通过对滨州市果园、菜地、棉地、麦地、林地以及自然土壤6种土地利用类型共93个土壤样品的调查分析,探讨了不同农业土地利用方式下土壤中铜的积累特征.结果表明,滨州市农业土壤铜含量均值为22.31 mg/kg,显著高于区域土壤背景值,土壤铜含量表现出明显的累积趋势.不同农业土地利用方式下土壤铜含量由高至低的顺序为:果园、菜地、棉地、麦地、林地.果园土壤中铜的累积问题最为突出,土壤铜平均含量达27.17 mg/kg,极显著高于自然土壤、林地土壤、麦地土壤和棉地土壤.菜地和棉地土壤铜含量极显著地高于自然土壤.所有样品均未超过国家土壤环境质量II级标准.5种农业土地利用类型中,果园和菜地土壤铜含量的变异系数较大,分别为32.17%和30.70%,表明这2种土地利用类型受到人为扰动较大.  相似文献   

9.
Hydroponic experiments conducted to examine the chromiun uptake by C. communis in the presence of different Cr concentrations (Cr6+ 100 and 200 mg/L, respectively) and free histidine supplementation (0.5 and 1.0 mol/L) showed that shoot and root growth of C. communis decreased greatly with increasing Cr concentrations in the medium; and that the species was a typical excluder since it accumulated high concentrations of Cr in roots but comparatively low concentrations in shoots. Chromium in shoots and roots of Cr42?-supplied plants ranged from 329–1880 and 3788–4240 mg/kg DW, respectively, while those of Cr42?-histidine-supplied plants ranged from 478 to 629 mg/kg and 4157–4303 mg/kg DW, respectively. With Cr present in the hydroponic solution, C. communis accumulated more Cr in its tissues. Increasing histidine application to the solution significantly increased chromium accumulation in the plant tissues but could not alter the accumulation pattern of plants although it induced a higher concentration of Cr in its shoots and roots. These features suggested that C. communis may serve as an alternative species in a constructed wetland for phytoextraction treatment of Cr-containing wastewater and for phytostabilization of Cr mining spoils.  相似文献   

10.
INTRODUCTION Hirudin, a naturally occurring polypeptide from salivary glands of medicinal leech (Hirudo Medici-nalis) and an important effective component of tradi-tional Chinese medicine Shui Zhi, has proven to be a highly selective direct thrombin inhibitor (Markwardt, 1994). Currently, in China recombinant-hirudin has been developed by DNA recombination technique and is undergoing extensive preclinical and clinical evaluation. Over the past decade, much effort in our lab was devote…  相似文献   

11.
Luciferase from firefly lantern extract was immobilized on CNBr-activated Sepharose 4B. The kinetic properties of immobilized luciferase were extensively studied. TheK m′ for D-luciferin is 11.9 μmol/L, the optimum pH and temperature for Sepharose-bound enzyme were 7.8 and 25°C respectively. A luminescence fiber optic biosensor, making use of immobilized crude luciferase, was developed for assay of ATP. The peak light intensity was linear with respect to ATP concentration in range of 10−9–10−5 mol/L. A biological application was also demonstrated with the determination of serum ATP from rats bred in low versus normal oxygen environments.  相似文献   

12.
BaFe12O19 powders with nanocrystaUine sizes were produced by sol-gel auto-combustion method. The precursors were prepared under the molar ratios of citric acid to the metal nitrate of 0.5, 1.0 and 1.5. Appropriate ethylene diamine （C2H8N2） was added in order to adjust pH of 7. The ions distribution of citric acid at different pH explains the effect of citric acid in the starting solution. The XRD patterns of the as-burnt powders and annealing powders show different phases for different citric acid content. In addition, the lattice constants （a, c） derived from X-ray diffraction pattern were changed from 0.58881 nm to 0.58997 nm and 2.32057 nm to 2.32296 nm respectively. The data from VSM indicated that the powder with high citric acid content took on good magnetic properties. Pure single BaFe12O19 of the specific maximum magnetization M（1 T）≈ 49.73 Am^2/kg, the specific remanent magnetization Mr ≈ 30.77 Am^2/kg and the coercive force He≈ 467 kA/m was produced when the molar ratios of citric acid to the metal nitrate was 1.5.  相似文献   

13.
In order to comply with the requirements for a drug listed in China, the study was developed to compare the pharmacokinetics and relative bioavailability of two different enteric formulations of omeprazole (OPZ) in healthy Chinese subjects. A total of 32 volunteers participated in the study. Plasma concentrations were analyzed by nonstereospecific liquid chromatography/tandem mass spectrometric (LC-MS/MS) method. After administration of a single 40-mg dose of the two OPZ formulations, the comparative bioavailability was assessed by calculating individual AUC0−t (the area under the concentration-time curve from time zero to the last measurable concentration), AUC0−∞ (the area under the concentration-time curve extrapolated to infinity), C max (the maximum observed concentration), and T peak (the time to C max) values of OPZ, 5-hydroxyomeprazole (OH-OPZ), and omeprazole sulfone (OPZ-SFN), respectively. The 90% confidence intervals (CIs) of AUC0−t , AUC0−∞, and C max were 85.4%–99.0%/88.8%–98.6%/87.6%–99.4%, 85.5%–99.2%/89.0%–98.6%/88.5%–101.3%, and 72.3%–87.6%/79.6%–91.1%/88.4%–99.1% for OPZ/OH-OPZ/OPZ-SFN, respectively, and T peak values did not differ significantly. In this study, the test formulation of OPZ in fasting healthy Chinese male volunteers met the Chinese bioequivalance standard to the reference formulation based on AUC, C max, and T peak.  相似文献   

14.
研究目的：腐殖酸（HA）对富勒烯（C60）粉末的悬浮作用以及pH、离子强度对HA-C60悬浮性能的影响。创新要点：研究水质条件对C60悬浮性能的影响。研究方法：测定C60粉末在HA溶液中的zeta电位,水力学粒径和悬浮浓度;HA存在下,C60悬浮体系的zeta电位与水力学粒径随pH的变化及C60悬浮体系团聚动力学随离子强度的变化。重要结论：HA对C60粉末起到一定的分散作用,但不能使其长时间稳定悬浮于水中。当pH〈4时,C60水悬液开始沉淀;而当HA存在时,C60水悬液在pH 3-11范围内都保持稳定,这是由于HA吸附于C60表面,通过静电排斥和空间位阻作用,促进C60分散悬浮。C60水悬液的稳定性随盐离子价位和浓度升高而降低。HA会抑制Na＋对C60水悬液的脱稳作用;但高价离子Ca2＋和La3＋存在时,HA与C60之间会发生桥联从而促进C60水悬液脱稳沉淀。  相似文献   

15.
Paracetamol (PCM) overdose can cause nephrotoxicity with oxidative stress as one of the possible mechanisms mediating the event. In this study, the effects of ethyl acetate extract of Zingiber zerumbet rhizome [200 mg per kg of body weight (mg/kg) and 400 mg/kg] on PCM-induced nephrotoxicity were examined. Rats were divided into five groups containing 10 rats each. The control group received distilled water while other groups were treated with extract alone (400 mg/kg), PCM alone (750 mg/kg), 750 mg/kg PCM+200 mg/kg extract (PCM+ 200-extract), and 750 mg/kg PCM+400 mg/kg extract (PCM+400-extract), respectively, for seven consecutive days. The Z. zerumbet extract was given intraperitoneally concurrent with oral administration of PCM. Treatment with Z. zerumbet extract at doses of 200 and 400 mg/kg prevented the PCM-induced nephrotoxicity and oxidative impairments of the kidney, as evidenced by a significantly reduced (P<0.05) level of plasma creatinine, plasma and renal malondialdehyde (MDA), plasma protein carbonyl, and renal advanced oxidation protein product (AOPP). Furthermore, both doses were also able to induce a significant increment (P<0.05) of plasma and renal levels of glutathione (GSH) and plasma superoxide dismutase (SOD) activity. The nephroprotective effects of Z. zerumbet extract were confirmed by a reduced intensity of renal cellular damage, as evidenced by histological findings. Moreover, Z. zerumbet extract administered at 400 mg/kg was found to show greater protective effects than that at 200 mg/kg. In conclusion, ethyl acetate extract of Z. zerumbet rhizome has a protective role against PCM-induced nephrotoxicity and the process is probably mediated through its antioxidant properties.  相似文献   

16.
利用SCS降雨模型,选取COD、氨氮两个常规评价指标以及铬、锰、铜、镍四个重金属指标,研究一次典型降雨在内江城区不同土地利用类型下产生的地面径流重金属污染负荷．结果表明：一次典型降雨在内江城区工矿、商业、交通、住宅和建筑五种土地利用方式下产生的COD、氨氮、锰、铬、铜、镍污染负荷浓度分别为37．20mg／L、0．67mg／L、0．12mg／L、0．01mg／L、0．03mg／L、0．03mg／L;产生的污染负荷总量分别是2361．08kg、35．20kg、7．41kg、1．47kg、1．28kg、7．44kg;商业用地产生的COD、氨氮污染负荷比例最大,负荷比例分别为66．56％、41．25％;交通用地产生的重金属污染负荷比例最大,锰、铬、铜、镍污染负荷比例分别为66．13％、7．75％、39．84％、45．30％;降雨径流将对研究区河道、湖泊以及河口产生短期或中长期污染．  相似文献   

17.
β-glucanase was purified from a solid-state culture ofTrichoderma reesei on wheat bran in three steps which comprised ammonium sulfate precipitation, Sephadex G-100 chromatography, and DEAE-Sephadex A-50 chromatography. The molecular mass was determined to be 35.21 kilodaltons by sodium dodecyl sulfate-12.5% polyacrylamide gel electrophoresis. The β-glucanase at low pHs was more stable than that at high pHs, and optimum pH was 5.0. The optimum temperature was 60°C, and β-glucanase was relatively stable at below 40°C for 60 min. TheK m of the enzyme on β-glucan was 10.86 mg/ml, and theV max on β-glucan was 14286 μmol of glucose equivalents per mg of the pure enzyme per min. The β-glucanase activity was significantly inhibited by Fe3+ ions, and was reduced in the presence of Cu2+ ions, Mn2+ ions and Mg2+ ions at 5 mmol/L and 10 mmol/L, respectively. The β-glucanase activity was stimulated by Co2+ ions, Ca2+ ions, Zn2+ ions, and Fe2+ ions at 1 mmol/L and 5 mmol/L, respectively. Project supported by Foundation for University Key Teacher of the State Ministry of Education, the National Natural Science Foundation of China (No. 30000118) and Zhejiang Provincial Natural Science Foundation of China (No. 399409).  相似文献   

18.
黄河三角洲盐碱地不同利用方式下土壤无机磷组分特征   总被引：1，自引：0，他引：1  
采用蒋柏藩-顾益初无机磷形态分级方法对黄河三角洲盐碱地试验田、藤柳林、芦苇地和石榴林4种不同利用方式下土壤无机磷组分特征进行了研究.结果表明,4种不同利用方式下盐碱地土壤无机磷各形态以Ca8-P、Ca10-P和Al-P为主,约占无机磷总量的77.41%,其中以钙结合态磷所占的比例最大,即盐碱地不同利用方式下土壤无机磷含量是以钙磷为主.石榴林由于在土壤中加入了石灰质,改变了土壤的特性且对土壤中Al-P含量影响较大,Al-P含量高达205.0 mg/kg,显著高于其他土地利用方式.盐碱地4种不同利用方式下土壤中O-P和Ca8-P含量相差不大,土地利用方式对土壤中O-P和Ca8-P含量影响较小.  相似文献   

19.
Selecting a subset of predictors from a pool of potential predictors continues to be a common problem encountered by applied researchers in education. Because of several limitations associated with stepwise variable selection procedures, the examination of all possible regression solutions has been recommended. The authors evaluated the use of Mallow's Cp and Wherry's adjusted R 2 statistics to select a final model from a pool of model solutions. Neither the Cp nor the adjusted R 2 statistic correctly identified the underlying regression model any better and was generally worse than the stepwise selection method, which itself was poor. Using any of the model selection procedures studied here resulted in biased estimates of the authentic regression coefficients and underestimation of their standard errors. The use of theory and professional judgment is recommended for the selection of variables in a prediction equation.  相似文献   

20.
The ecosystem characteristics of soil microorganism and the nutrient uptake of irrigated rice were investigated in a split-block experiment with different fertilization treatments, including control (no fertilizer application), PK, NK, NP, NPK fertilization, in the main block, and conventional rice and hybrid rice comparison, in the sub block. Average data of five treatments in five years indicated that the indigenous N supply (INS) capacity  相似文献   

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