新疆喀纳斯国家级自然保护区土壤螨类群落特征

为研究喀纳斯自然保护区土壤螨类群落特征,2011年7月和9月对该保护区针叶林、混交林、阔叶林、灌木林、草甸草原、林间草地、沼泽地7种生境进行了取样调查。结果表明:1)共获得土壤螨类7268只,隶属于3亚目51科58属。其中甲螨亚目3819只,38科44属,占总数的93.34%;中气门亚目264只,9科11属,占总数的6.45%;前气门亚目7只3科3属,占总数的0.21%。整个研究区域中奥甲螨属Oppia、盖头甲螨属Tectocepheus、钉棱甲螨属Passalozetes、菌甲螨属Scheloribates为优势类群,占总数的60.05%;阿斯甲螨属、短甲螨属、大翼甲螨属等13属为常见类群,占总数的29.43%;其余的41属为稀有类群,占总数的10.52%。2)在不同生境条件下土壤螨类个体数和类群数均有显著差异(P<0.05),其中个体数依次为阔叶林>针叶林>林间草地>混交林>沼泽地>草甸草原>灌木林;而类群数依次为阔叶林>草甸草原>沼泽地>针叶林>灌木林>混交林>林间草地。3)垂直分布具有明显的表聚性特征,其中0~5cm土层最多,其次为5~10cm,而10~15cm最少。4)在该保护区不同生境土壤螨类的群落组成和结构差异与植被类型、土壤环境因素及人为干扰程度有关。     

<Emphasis Type="Italic">Cucurbit aphid-borne yellows virus</Emphasis> in Egypt

During 2010, yellowing symptoms were frequently observed in cultivated squash fields in Egypt. A total of 717 symptomatic squash leaf samples were collected from four regions where squash cultivation is of economic importance for the country: Kafrelsheikh, El-Behira, El-Sharkia and El-Ismailia. Serological analysis showed that 95.6% of the symptomatic squash samples were infected by Cucurbit aphid-borne yellows virus (CABYV), and visual estimation of the incidence of yellowing symptoms suggested a very high incidence of CABYV in the fields. Twelve CABYV isolates were characterized by sequencing two regions of the viral genome, open reading frame (ORF) 3 and ORFs 4/5. Overall, Egyptian isolates were very similar among them, and had higher similarity values with a French than with a Chinese isolate. The average nucleotide diversity for ORF 3 was significantly higher than for the other two regions, indicating that variability is not evenly distributed along the viral genome. The ratios between nucleotide diversity values in non-synonymous (d _N ) and synonymous (d _S) positions (d _N /d _S) for each ORF showed that the three ORFs are evolving under different pressures, although predominantly under purifying selection. Phylogenetic analyses revealed that these Egyptian isolates, with only one exception, shared the same clade with a French isolate. Moreover, these analyses suggested that Egyptian isolates belong to the Mediterranean group described previously.     

Measurements and estimates of potential evapotranspiration over Egypt

Mehanna (1976) estimated potential evapotranspiration (PE) for a number of stations in Egypt, using Penman's method with adjustment of the constants of the radiation term and the aerodynamic term, such that they would agree with measurements of radiation in Egypt and with estimations by Omar (1971a,b) of PE in a large field at Giza, to the southwest of Cairo. Measurements of PE were made at Bahtim, about 20 km to the north of Cairo, by evapotranspirometers.In the FAO Irrigation and Drainage Paper No. 24 on “Crop Water Requirements” (Doorenbos and Pruitt,1977) four methods were given for the calculation of PE; Blaney—Criddle, radiation, Penman (adjusted) and pan evaporation. It was considered that the Penman method was the most accurate of those given.The main features of comparison of the Mehanna and FAO's estimates of PE with measurements at Bahtim were that Mehanna, and three of the FAO's estimates (Blaney—Criddle, radiation and pan evaporation) are within ±10%0 of the measurements while the Penman estimate was 15% higher. An estimate of PE at Aswan was based on measurements of pan evaporation and estimates of evaporation from a large water surface at both Bahtim and Aswan, together with measurement of PE at Bahtim. The estimates by the methods of Mehanna, Blaney—Criddle, radiation and Penman lie in the limits 0—6% of the estimate based on measurements while the pan evaporation estimate is markedly lower. Comparison of the estimates at eight stations over Egypt shows that the Penman estimate is higher than the other estimates in Northern Egypt. The pan evaporation estimate is lower than the other estimates except at Bahtim where it is generally higher than Mehanna's and Blaney—Criddle's estimates. The low values of the pan evaporation estimates at Assuit and Aswan are remarkable.     

ALLEVIATING THE INFERTILITY OF AN ACID SULPHATE SOIL BY USING GROUND BASALT WITH OR WITHOUT LIME AND ORGANIC FERTILIZER UNDER SUBMERGED CONDITIONS

A study was conducted into the alleviation of the infertility of an acid sulphate by using ground basalt with or without ground magnesium limestone (GML) and organic fertilizer. Fresh soils were treated with the amendments and subjected to two cycles of submergence and drying. The soil was dominated by kaolinite, mica and smectite. The untreated soil pH was <3·5 and solution Al was high. GML application at 4 t ha⁻¹ was able to increase pH and subsequently reduced Al toxicity sufficiently to allow for rice growth. After 4 months of submergence, the pH of the sample treated with 4 t ground basalt ha⁻¹ had increased from 3·61 to 3·94, with concomitant decrease of Al. In the same cycle, the soil pH increase was much higher (reaching 5·22). Ground basalt is thus comparable with GML as an acid soil ameliorant. Within the experimental period, the ground basalt had mostly disintegrated and dissolved. The solution pH had further increased (to 5·94) in the second cycle because of dissolution of more ground basalt. This means that it takes time for ground basalt to completely dissolve and consequently supply Ca, Mg, K and P to the growing crop in the field. Applying 0·25 t organic fertilizer ha⁻¹ into the soil had no significant effect on either pH or Al. This form of organic matter (compost) contains essential nutrients. It is recommended that 4 t ground basalt should be applied in combination with 0·25 t organic fertilizer ha⁻¹ a few months ahead of the growing season for maximal benefit. This study showed that ground basalt can be effectively used to ameliorate highly acidic soils. Copyright © 2011 John Wiley & Sons, Ltd.     

Influence of organic and inorganic passivators on Cd and Pb stabilization and microbial biomass in a contaminated paddy soil

Purpose

Soil contamination with heavy metals, such as Cd and Pb, has caused severe health and environmental risks all over the world. Possible eco-friendly solutions for Cd and Pb immobilization were required to reduce its mobility through various cost-effective amendments.

Materials and methods

A laboratory incubation study was conducted to assess the efficiency of biochar (BC), zeolite (ZE), and rock phosphate (RP) as passivators for the stabilization of Cd and Pb in paddy soil as well as soil microbial biomass. Various extraction techniques were carried out: a sequential extraction procedure, the European Community Bureau of Reference (BCR), toxicity characteristic leaching procedure (TCLP) test, and single extraction with CaCl₂. The impact of passivators on soil pH, dissolved organic carbon (DOC), and microbial biomass (carbon, nitrogen, and phosphorus) was examined in the metal contaminated soil.

Results and discussion

The results showed that the exchangeable portion of Cd in soil was significantly reduced by 34.8, 21.6, and 18.8% with ZE, RP, and BC at a 3% application rate, respectively. A similar tendency of reduction in Pb soluble portion was observed by ZE (9.6%), RP (20%), and BC (21.4%) at a 3% application rate. Moreover, the TCLP leachate of Cd and Pb was apparently reduced by 17 and 30.3% with BC at a 3% application dose, respectively, when compared to the control. Soil pH, nutrients, and microbial biomass C, N, and P were significantly increased with the addition of BC, RP, and ZE passivators.

Conclusions

The results showed that the incorporation of BC, ZE, and RP significantly reduced the Cd and Pb mobility in paddy soil as well as enhanced soil nutrients and microbial biomass. Overall, among all the amendments, rice straw derived-BC performed better for Cd and Pb immobilization in paddy soil.

     

ELLA: A Rapid Technique to Estimate Chromium Stress-Induced Modification of E. coli EI19

An enzyme-linked lectin assay (ELLA) was used to differentiatebetween chromium-stressed and unstressed cells of Escherichia coli EI19. The assay is a modification of the enzyme-linked immunosorbent assay (ELISA) that uses Concanavalin A (Con A) conjugated with peroxidase to detect the carbohydrate moiety of the cell envelope glycoconjugates. The ELLA test shows that Con A binds to stressed bacteria much moreefficiently than it does to unstressed bacteria. Effects of heat,phenol and papain treatments on Con A-binding to chromium-stressed bacteria were also studied. Con A-binding to bacteria was sensitive to heat and phenol treatment, but not to treatment with papain. A potential analytical method for estimating the concentration of certain environmental pollutants is outlined.     

Mode of inheritance of zinc accumulation in maize

The present study was undertaken to investigate the genetic nature of zinc (Zn) accumulation in the ear‐leaves of maize (Zea mays L.) plants. Fourteen inbred lines were evaluated. Out of which, five inbreds were chosen, two high Zn accumulators (Rg‐5 and Rd‐2), two low Zn accumulators (Rg‐8 and G‐307) and a moderate one (K‐64). These five parental inbreds were utilized to obtain all possible ten F1 hybrids (in one direction), 10 F2, 10 Bl, and 10 B2. All genotypes were planted and Zn was estimated at 50% tasseling stage. Zinc accumulation in the present genotypes was found to be genetically controlled and affected by additive genes. Significant values were obtained for the General Combining Abilities (GCA) but not for the Specific Combining Abilities (SCA) and the high Zn accumulating parents were the best general combiners. Four genes were found to be the minimum segregating factors in the (high x low) crosses for Zn accumulation.     

Identification of proanthocyanidin dimers and trimers, flavone C-Glycosides, and antioxidants in Ficus deltoidea , a malaysian herbal tea

Phenolic compounds in an aqueous infusion of leaves of Ficus deltoidea (Moraceae), a well-known herbal tea in Malaysia, were analyzed by HPLC coupled to photodiode array and fluorescence detectors and an electrospray ionization tandem mass spectrometer. Following chromatography of extracts on a reversed phase C(12) column, 25 flavonoids were characterized and/or tentatively identified with the main constituents being flavan-3-ol monomers, proanthocyanidins, and C-linked flavone glycosides. The proanthocyanidins were dimers and trimers comprising (epi)catechin and (epi)afzelechin units. No higher molecular weight proanthocyanidin polymers were detected. The antioxidant activity of F. deltoidea extract was analyzed using HPLC with online antioxidant detection. This revealed that 85% of the total antioxidant activity of the aqueous F. deltoidea infusion was attributable to the flavan-3-ol monomers and the proanthocyanidins.     

Spatial Distribution and Temporal Trends of Polycyclic Aromatic Hydrocarbons (PAHs) in Sediments from Lake Maryut, Alexandria, Egypt

Surface and core sediments from Lake Maryut, Egypt, one of the most polluted lakes in Egypt, were analyzed for polycyclic aromatic hydrocarbons (PAHs) using gas chromatography?Cmass spectrometry. This investigation represents the first extensive study of the distribution and sources of PAHs in sediments from Lake Maryut. The total PAHs concentrations (sum of 39 PAH compounds) in surface sediments varied greatly depending on the sampling location and ranged from 106 to 57,800 ng/g dry weight with a mean concentration of 6,950 ng/g. The most polluted areas are distributed in areas which are mainly influenced by municipal sewage and industrial effluent discharges, suggesting a direct influence of these sources on the pollutant distribution patterns. PAH concentrations were one to two orders of magnitude higher in comparison with those reported for riverine/estuaries systems around the world. Molecular indices, such as pyrogenic index (PI), methylphenanthrenes to phenanthrene ratio, HMW_PAH/LMW_PAH, A-PAHs/P-PAHs, FL/FL?+?PY, BaP/BaP?+?C, IP/IP?+?BgP, and Per/??(penta-aromatics) were calculated to evaluate different hydrocarbon origins and their relative importance. In general, sediments from the main basin and northwest basin of Lake Maryut showed the highest PAH concentrations with petrogenic signatures, indicating major sources of petrogenic PAHs in the city. On the other hand, lower levels of PAHs with a pyrogenic signature were widely recorded in areas that are distant from anthropogenic sources. At other locations, both petrogenic and pyrogenic inputs were significant. The concentrations of perylene relative to the penta-aromatic isomers are dominant especially in locations associated with terrestrial inputs and in the deepest core sediments, indicating diagenetic origin for the presence of perylene. Temporal trends of PAH concentrations in both cores sediments were influenced by input pathways and followed the economic development and the environmental policies of the Egyptian Government in the last 15 years. Finally, PAH levels in sediments were compared with Sediments Quality Guidelines (effects range median?Ceffects range low) for evaluation probable toxic effects on organism. Results suggest an ecotoxicological risk for benthic organisms mainly in the main basin area, where high concentrations of PAHs were found in sediments influenced by anthropogenic activities.