榆林沟流域水土资源开发利用研究   总被引：1，自引：1，他引：1       下载免费PDF全文

吴德仓  蒲玉宏  段义字 《水土保持通报》2001,21(1):74-76,80

研究了黄河中游第 4期试点流域——榆林沟流域水土资源与环境优势、水土资源开发利用所存在的问题 ,提出了该流域水土资源开发利用途径 ,并通过措施的对位配置 ,对水土资源开发利用实际效果进行了分析  相似文献   

Method for the detection of synthetic cry3A in transgenic potatoes     

Smith DS  Maxwell PW  De Boer SH 《Journal of agricultural and food chemistry》2004,52(4):809-815

All transgenic cultivars of potatoes registered in Canada and the United States have been modified to express a synthetic cry3A gene as a means of conferring resistance against the Colorado potato beetle, an important economic pest of potatoes. A PCR method was developed to amplify a 499 bp region of the synthetic cry3A gene. Using this method, synthetic cry3A could be detected in six different transgenic cultivars. Positive results could be confirmed with PvuII restriction digestion of the PCR-generated amplicon, which resulted in two fragments that were 283 and 216 bp in size. Of the 52 tuber extracts tested with this method, no false positive or false negative results were obtained, suggesting the method could be used with a high degree of accuracy. The absolute limit of detection was the number of cry3A copies present in one or perhaps two haploid copies of the potato genome. The practical limit of detection in tubers on a fresh weight basis was 0.02% for the NL 10-SUP and 0.01% for the remaining cultivars. Synthetic cry3A could also be detected in processed food products such as potato chips, shoestring potatoes, and frozen French fries. The method was suitable for screening potato tuber lots and some processed foods for the presence of synthetic cry3A.  相似文献   

Comparison of key aroma compounds in cooked brown rice varieties based on aroma extract dilution analyses   总被引：5，自引：0，他引：5  

Jezussek M  Juliano BO  Schieberle P 《Journal of agricultural and food chemistry》2002,50(5):1101-1105

The aroma compounds present in cooked brown rice of the three varieties Improved Malagkit Sungsong (IMS), Basmati 370 (B 370), and Khaskhani (KK), and of the variety Indica (German supermarket sample), were identified on the basis of aroma extract dilution analyses (AEDA). A total of 41 odor-active compounds were identified, of which eleven are reported for the first time as rice constituents. 2-Amino acetophenone (medicinal, phenolic), which was up to now unknown in rice aroma, exhibited the highest flavor dilution (FD) factor among the 30 to 39 odor-active compounds detected in all four varieties. 2-Acetyl-1-pyrroline, exhibiting an intense popcorn-like aroma-note, was confirmed as a further key aroma constituent in IMS, B 370, and KK, but was not important in Indica. Differences in the FD factors between the varieties were found for the previously unknown rice aroma compound 3-hydroxy-4,5-dimethyl-2(5H)-furanone (Sotolon; seasoning-like), which was higher in B 370 than in IMS and KK. In IMS, a yet unknown, spicy smelling component with a very high FD factor could be detected, which contributed with lower FD factors to the overall aromas of B 370 and KK, and was not present in Indica. The latter variety, which was available on the German market, differed most in its overall aroma from the three Asian brown rices.  相似文献   

Heavy‐metal mobilization and uptake by mycorrhizal and nonmycorrhizal willows (Salix × dasyclados)     

Christel Baum  Katarzyna Hrynkiewicz  Peter Leinweber  Ralph Meißner 《植物养料与土壤学杂志》2006,169(4):516-522

Ectomycorrhizal fungi have been shown to affect metal transfer from the soil to the host plant, but the use of these fungi for increased phytoextraction of heavy metals has been scarcely investigated. Therefore, a two‐factorial pot experiment was conducted with Salix × dasyclados and (1) two contaminated soils with different concentrations of NH₄NO₃‐extractable metals and (2) two strains of the ectomycorrhizal fungus Paxillus involutus (one strain originating from a noncontaminated site—Pax1, and another from a contaminated site—Pax2). The inoculation with Pax2 increased the phytoavailability of Cd in the soils. Inoculation with both fungal strains increased the stem and root biomass, but had no effect on metal concentrations in the stems. Decreased Cd and increased Cu concentrations were observed in the roots of inoculated willows. The inoculation with P. involutus increased Cd (up to 22%), Zn (up to 48%), and Cu content in the stems. Decreased Pb content (Cu and Pb content were always <1 mg per plant) occurred in the stems from plants at the soil with the higher concentration of NH₄NO₃‐extractable metals. Contrary to this, in the soil with lower concentrations of NH₄NO₃‐extractable metals, the inoculation had no significant effects on the total uptake of Zn and Cu and even caused decreased Cd (Pax2) and Pb (Pax1) contents in the stems. Strain Pax2 had higher colonization densities, but the plants had lower mycorrhizal dependencies in the contaminated soils than after inoculation with the strain Pax1. Generally, metal extractability in the soils substantially affected the mycorrhizal dependency and heavy‐metal uptake of the willows. We concluded, that the inoculation with P. involutus offers an opportunity to particularly increase the phytoextraction of Zn, but the metal extractability and fungal strain effects have to be tested.  相似文献   

An empirical approach to target DNA quantification in environmental samples using real-time polymerase chain reactions     

Robert H. Gulden  David Levy-Booth  Jeff R. Powell  Kari E. Dunfield  K. Peter Pauls  Clarence J. Swanton 《Soil biology & biochemistry》2007,39(8):1956-1967

Recent advances in molecular techniques have allowed for the routine examination of nucleic acids in environmental samples. Although current methodologies are very sensitive, accurate target DNA quantification from environmental samples remains challenging. To facilitate high-throughput DNA quantification from environmental samples, we developed a novel DNA quantification method based on a non-linear curve-fitting approach to extract additional information from quantitative PCR amplification curves and used the fitted parameters to develop multiple regression standard equations for target DNA quantification. A 3-parameter sigmoidal function performed superior to a 4-parameter Weibull function for generating the multiple regression standard equations. In a verification experiment, target DNA was quantified in a series of ‘unknown’ samples in three soils using this approach and the results were compared to target DNA values determined using corrected and uncorrected Ct-based (threshold cycle) methods. For each method, the deviations from the expected target DNA content were determined. Results clearly showed that over all DNA concentrations, target DNA content determined by the non-linear curve-fitting method was more accurate and more precise than values predicted by all other methods. Analysis of variance conducted on the predicted DNA contents also revealed fewer statistical artifacts with the non-linear curve fitting method compared to the conventional Ct-based methods. The novel approach described here is accurate, inexpensive, and very amenable for automation and high-throughput applications.  相似文献   

Spatial variation of soil enzyme activities and microbial functional diversity in temperate alley cropping systems   总被引：1，自引：0，他引：1  

Nancy W. Mungai  Peter P. Motavalli  Robert J. Kremer  Kelly A. Nelson 《Biology and Fertility of Soils》2005,42(2):129-136

Spatially dependent patterns in microbial properties may exist in temperate alley cropping systems due to differences in litter quality and microclimate in areas under trees compared to those in the alleys. The effect of tree row location was evaluated for its impact on soil enzyme activities and Biolog substrate use patterns. Soils were sampled to a depth of 30 cm at the tree row and at the middle of the alley at two sites: a 21-year-old pecan (Carya illinoinensis)/bluegrass (Poa trivials) intercrop (Pecan site) and a 12-year-old silver maple (Acer saccharinum)/soybean (Glycine max)–maize (Zea mays) rotation (Maple site). Sampling was done in fall 2001 and summer 2002. β-Glucosidase activities, Biolog patterns expressed as average well color (AWC), substrate richness, and Shannon diversity index, and total Kjeldahl nitrogen (TKN) were significantly higher (P<0.05) in the tree row than at the middle of the alley for surface soils at the Pecan site. Fluorescein diacetate (FDA) hydrolytic activity was also higher at the tree row for soils sampled in the fall, but did not differ significantly for soils sampled in the summer. At the Maple site, AWC and substrate richness were significantly higher at the tree row for soils sampled in 2001. Soil volumetric water content and temperature were generally lower in the tree row at the Maple site. The results of this study suggest that functionally different microbial populations may be present under pecan trees compared to cropped alleys which may promote disparities in nutrient availability necessitating differential long-term nutrient management in such alley cropping systems.  相似文献   

Uncertainties in static closed chamber measurements of the carbon isotopic ratio of soil-respired CO₂     

K.E. Anders Ohlsson  Bhupinderpal Singh  Anders Nordgren  Peter Högberg 《Soil biology & biochemistry》2005,37(12):2273-2276

The δ¹³C of soil-respired CO₂ (δ_r) is frequently determined using static closed chamber methods. δ_r is obtained as the intercept of the least squares linear regression of δ vs 1/C*, where measured δ¹³C-CO₂ (δ) and volume fraction of CO₂ (C*) values of chamber headspace samples are used. Theoretically, we show that the variance of the estimate of δ_r can be reduced by extending the 1/C* interval of the regression towards (i) higher or (ii) lower values, or (iii) distributing the 1/C* values optimally within the pre-selected headspace CO₂ sampling time period. Experimental applications of these approaches indicated that: (1) lowering the initial CO₂ level, thereby increasing 1/C*, yielded a positive bias to the δ_r result. (2) It was feasible to obtain lower variance in the δ_r estimate by lowering 1/C* values through extended CO₂ sampling time. We also recommend that each chamber is sampled only once, mainly because this allows freedom to select the sampling times, in order to optimize the distribution of 1/C* values.  相似文献   

Mercury speciation in contaminated soils by thermal release analysis   总被引：1，自引：0，他引：1  

Cláudia Carvalhinho Windmöller  Rolf-Dieter Wilken  Wilson De Figueiredo Jardim 《Water, air, and soil pollution》1996,89(3-4):399-416

Thermal release analysis of mercury species in contaminated soils was performed by temperature controlled continuous heating of the samples in a furnace coupled to an Atomic Absorption Spectrophotometer (AAS). It was shown that this method allows the identification of different redox states of Hg-species through their characteristic releasing temperature ranges. The method was applied to Hg-contaminated samples from an inactive chlor-alkali production plant in former East Germany (GER), and from a gold mining area in Poconé, Mato Grosso, Brazil (BRA), as well as synthetic soil samples obtained by spiking pre-heated soil matrices (GER and BRA) with the following mercury species: Hg⁰, Hg₂Cl₂, HgCl₂, HgO and HgS. The samples GER, in general, frequently showed the presence of Hg²⁺ probably bound to humic substances, in the case of samples with higher total carbon content. Only in highly contaminated samples (>3000 ppm of mercury) was Hg⁰ the predominant species. The samples BRA more frequently showed the presence of mercury species in the lower oxidation states, i.e. Hg¹⁺ in combination with Hg⁰. The method allows observing changes in Hg-speciation in the samples with time, mainly changes among the oxidation states Hg⁰, Hg¹⁺ and Hg²⁺. The treated GER matrix showed a stronger tendency to oxidise Hf-species than the BRA treated matrix, in which only added Hg⁰ is partially oxidised to Hg²⁺ and Hg¹⁺. In contrast, the BRA matrix showed a pronounced tendency to reduce spiked Hg²⁺ to Hg¹⁺. This may be the reason for the presence of Hg¹⁺ in the majority of original BRA samples. The method appears to be very useful to study speciation of mercury and its dynamics. It can be used as a tool for monitoring mercury oxidation states and/or reactions of mercury in soils.  相似文献   

Geochemical fluxes in forested acidified catchments     

Jörg Matschullat  Peter Kritzer  Willy Maenhaut 《Water, air, and soil pollution》1995,85(2):859-864

The atmospheric deposition of some major components (e.g., NO₃-N 6.6 and 14.5; SO₄-S 17.8 and 42.4 kg ha^–1 a^–1) and trace elements (e.g., Cd 0.4 and 1.1, Cu < 1.9=" and=" 15,=" pb=" 43=" and=" 48=" g=">^–1 a^–1) in bulk and throughfall deposition respectively, shows a pronounced decline in recent measurements of total deposition in the eastern Erzgebirge (Germany). This is true for both bulk and throughfall deposition in 1992–1994 as compared to similar data from 1985–1989. The decline is a result of successful emission control strategies in central Europe and the shut down of plants and factories in the former GDR.The dry deposition at the highest (influenced by long-range transport) and the lowest station (local influences) shows distinct differences (e.g., Cd 0.6 and 0.3; Cu 17.4 and 7.3; Pb 13 and 31 ng m^–3). A comparison between total and dry deposition exhibits the different behavior of elements in respect to atmospheric concentrations and solubility in (rain)water. Anthropogenically released elements are mainly immited via wet deposition.  相似文献   

Ozone sensitivity of Phaseolus vulgaris in relation to cultivar differences,growth stage and growing conditions     

K. Vandermeiren  L. De Temmerman  N. Hookham 《Water, air, and soil pollution》1995,85(3):1455-1460

Exposure of Phaseolus vulgaris cv. Lit to ambient ozone caused a 14% pod yield reduction in 1994. This yield loss was assessed by comparing plants that were protected against ozone by treatment with EDU (ethylenediurea) with unprotected plants, both cultivated in pots with a continuous water supply. The plants had experienced an AOT40 of 8135 ppb.h during their growth. However, plant response to ozone depends on a large number of environmental and plant-specific conditions. Visible injury increased mainly after flowering and was much less severe on soil-grown bean cultivars (Lit, Stella and Groffy) not receiving additional water. Ozone fumigations in closed chambers before or after flowering proved that the growth stage during which the plants are exposed also plays a very important role with regard to injury development. Plants seem to be more susceptible during the generative growth stage and the relative cultivar sensitivity was related to the developmental stage during fumigation. However with regard to yield effects the timing of the ozone exposure seems to be less important.  相似文献