A Laboratory Column Study on the Biodegradation of Toluene and Methyl tert–Butyl Ether: The Effect of Substrate Interactions

Soil vapor extraction (SVE) is one of the most effective remediation technologies for soil and groundwater contamination. Soil particles can be mobilized by air perturbation during SVE, resulting in the differentiation of porous media, which has not been well addressed. This paper developed a numerical method to study the flow pattern and quantify the change of porous media for the first time. Based on the mass equilibrium and Darcy’s law, a two-phase water–air flow model was constructed with integration of saturation, relative permeability, and capillary pressure during SVE. Relationship between porosity and saturation was deduced and coupled with the two-phase flow model for quantifying change of porous media in real time. Results reveal that both porosity and permeability increase sharply in the early stage of SVE then gradually to a quasi-steady state. These increases in vadose zone tapered off with distance from the SVE screen and the steady period occurred later as well. The influence radius of a single SVE well and the change degree in porosity and permeability of media were proportional to the extraction vacuum and the driving coefficient C, which is more sensitive than extraction vacuum according to the simulation results. Knowledge from this modeling exercise provides a useful tool to estimate the change of remediated zone and assess the environmental risk of remedial activities at real-world contamination sites.     

Effects of N sources and methane concentrations on methane uptake potential of a typical coniferous forest and its adjacent orchard soil

After removal of the above-ground plant debris three different soil layers were taken from a typical coniferous forest and its adjacent orchard in Numata City, Japan. The potentials of soil CH₄ uptake at two initial CH₄ concentrations were studied under aerobic conditions in the laboratory, along with inhibition of soil CH₄ oxidation by urea-N or KNO₃-N addition. Due to long-term N inputs, the CH₄ uptake of the upper mineral layer of the orchard soil was 25.4% and 87.7% lower than that of the surface forest soil at 2.4 and 12.6 l l^–1 CH₄, respectively. Methane uptake of the forest soil decreased with increasing soil depths at two CH₄ levels. However, maximal CH₄-consuming activity occurred in the 9- to 23-cm depth of the orchard soil at 12.6 l l^–1 methane. Nitrogen additions in the form of KNO₃ or urea at the rate of 200 g N g^–1 soil substantially reduced soil CH₄ uptake in the upper and sub-surface mineral layers at both sites, except that the addition of KNO₃-N had no apparent inhibitory effect on the CH₄ uptake in the 9- to 23-cm depth of the orchard soil. A strong inhibitory effect of NO₃^– addition on the CH₄ uptake, in contrast to NH₄⁺, occurred in the surface forest soil. The use of KNO₃-N, as compared to urea or urea plus a nitrification inhibitor (dicyandiamide), resulted in a lower potential to cause inhibition of CH₄ oxidation in the 0- to 23-cm depth of the orchard soil.     

Do enchytraeid worms and habitat corridors facilitate the colonisation of habitat patches by soil microbes?

Due to their high abundance and ubiquitous existence, microbes are considered to be efficient colonisers of newly established habitats. To shed light on the dispersal mechanisms of soil microbes, a controlled microcosm experiment was established. In these microcosms, the dispersal of microbes from a source humus patch to originally sterile humus patches (embedded in a mineral soil matrix) was followed for 16 months, applying 16S and 18S ribosomal DNA-based PCR-DGGE molecular methods. Specifically, the role of enchytraeid worms and habitat (humus) corridors as possible facilitators of microbe dispersal was studied. The results showed that enchytraeid worms function efficiently as vectors for horizontal dispersal of saprophytic fungi in soil. Some of the fungi also proved to disperse through the corridors by vegetative growth, although this dispersal was inefficient as compared to dispersal with the enchytraeids. Virtually no saprophytic fungi were able to disperse through the mineral soil matrix in the absence of both enchytraeid worms and corridors. Unlike soil fungi, the dispersal of soil bacteria was not affected by any of the studied factors. The results of the present experiment provide direct evidence of the crucial role of soil fauna in aiding the horizontal dispersal of soil fungi. The role of enchytraeids as a functionally important species in boreal forest soils is further emphasized, since bringing microbes into contact with new resources is likely to enhance the rate of decomposition in soils.     

Evidence of N<Subscript>2</Subscript>O emission and gaseous nitrogen losses through nitrification-denitrification induced by rice plants (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

A greenhouse experiment was conducted with a specially designed apparatus consisting of an upper and lower chamber where the treatment with rice was carried out (treatment 1). The apparatus also had a single chamber where treatment 2, without rice plants, was carried out. The scope of this study was to elucidate the influence of rice plant growth on gaseous N losses as N₂ and N₂O produced by nitrification-denitrification in a flooded soil fertilized with (NH₄)₂SO₄ (with 56.50 atom% ¹⁵N). Gas samples were withdrawn weekly and analyzed for (N₂ + N₂O)-¹⁵N losses by mass spectrometer and for N₂O by gas chromatograph. The gaseous (N₂ + N₂O)-¹⁵N losses of the treatment with rice plants were significantly (P =0.01) higher than those of the treatment without rice plants, as were the amounts of N₂O emitted. Rice plants facilitate the efflux of N₂ and N₂O from soil to atmosphere, as about half of the total gaseous ¹⁵N loss as N₂ and N₂O was found in the upper chamber. The proportion of N₂O-¹⁵N to (N₂ + N₂O)-¹⁵N in the upper chamber was 10.56%, much higher than that of the lower chamber in treatment 1 and the headspace of treatment 2.     

Genetic diversity of winter wheat in Shaanxi province, China, and other common wheat germplasm pools

Cultivated Chinese wheat germplasm has been a valuable genetic resourcein international plant breeding. Landraces endemic to China are a geneticresource that is distinct from other wheat germplasm. Patterns of geneticdiversity among cultivated Chinese accessions and relationship to othergermplasm pools are unknown, despite the proven value and potential novelty. Theobjective of this work was to determine the level of genetic diversity withinimproved Chinese germplasm in the context of several other wheat germplasmpools. We analyzed a set of improved accessions cultivated from the 1940s to the1990s in Shaanxi province, China, using six simple sequence repeat (SSR) primerpairs and 30 restriction fragment length polymorphism - probe enzymecombinations (RFLP-PEC) previously used to characterize 21 geographically basedgermplasm pools. Shaanxi germplasm consists of three groups based on foreignintroductions from Italy, Australia, Denmark, and Russia. There was a decreasein genetic diversity among Shaanxi accessions cultivated in the 1970s and 1980sto the 1990s, and accession classifications based on primary decade ofcultivation were found to be significantly undifferentiated. The analysis of themean genetic distance among 22 geographically based pools of germplasm suggestsseveral regions are significantly undifferentiated. A vast majority of the totalamount of variation was found within pools; therefore, pools appear to belargely differentiated based on small differences in band relative frequency andfew if any unique bands. Previous studies have identified some Chinese landracepools as morphologically and genetically unique. The Shaanxi pool does not havethe same unique morphological or genetic features, nor is it more similar to thelandrace pools than other improved germplasm pools.     

Lepidium latifolium: plant nutrient competition-soil interactions

Exotic weeds are invading rangelands of the western United States at unprecedented rates. Understanding plant-soil relationships and competitive interactions of invasive weeds is crucial in long-term control strategies. In a greenhouse experiment, we investigated the influence of soil nutrient depletion on plant growth and plant competition between the exotic invasive weeds, Lepidium latifolium (invading wetlands) and Bromus tectorum (invading a multitude of habitats). Plants were grown individually and in combination until L. latifolium flowered, then roots and aboveground mass were harvested. Soil in individual pots was homogenized, subsamples collected for nutrient analyses, and the soil was re-planted to the same species, grown, and harvested twice more for a total of three growth cycles. As nutrient supplying capacity of the soil declined through growth cycles, aboveground mass of L. latifolium decreased significantly (PА.05) and growth potential of B. tectorum surpassed that of L. latifolium. Only bicarbonate-extractable soil ortho-P positively correlated with plant mass of L. latifolium. A separate experiment demonstrated that L. latifolium has a narrow window of soil water potentials for optimal growth; greatest growth at -20 kPa with significantly declining growth at saturation and -400 kPa. Our data suggest that L. latifolium primarily invades wetlands because the high soil water content reduces tortuosity and allows efficient transport of nutrients to this sparsely rooted species. When soil moisture and/or the nutrient supplying capacity of the soil declines, plants with greater root density can out-compete L. latifolium. Monocultural stands of L. latifolium may be self-limiting in time as available nutrients, particularly P, are biocycled to drier upper soil layers.     

遗传标记及其在家禽育种中的应用

1 SNP SNP是染色体中遗传变异的最普通形式,如在人体已经检测基因组DNA中每1,000到2,000个单位有1个SNP,在某些区域估计每300个单位有一个SNP.基于SNP的高分辨率,遗传图谱在一些人的染色体上通常没有得到发展.正如其名称所指,SNP是发生在基因(启动子、外显子、或内含子)或基因之间(基因间隔区)的单个碱基改变或核苷酸变异.编码序列中的SNP以同义(不会导致氨基酸改变)或非同义(导致氨基酸改变)来分类.非同义SNP由于对蛋白质表达及最终对表现型的潜在影响而受到重视.相反,同义SNP可能对基因表达有微小的影响(除那些在启动子和其它基因组区域中,对DNA-蛋白质作重要的核苷酸或与RNA稳定性有关的核苷酸).同义和非同义SNP在基因图谱研究中均是很好的遗传标记.     

Virtual Studio System Technology

Virtual studio system (VSS), a new technology based on virtual reality, develops fast in recent years. Virtual studio concept replaces real background sets with computer generated 3D synthetic and combines real foreground action, with computer generated backgrounds. As VSS need not construct real background sets and has little limitness of time and space, it is regarded as a revolution in TV programs. This paper mainly discusses about the background, technology feature, application and future.     

Genetic analysis of ORF5 of recent Korean porcine reproductive and respiratory syndrome viruses (PRRSVs) in viremic sera collected from MLV-vaccinating or non-vaccinating farms

The 23 open reading frame (ORF) 5 sequences of Korean type II porcine reproductive and respiratory syndrome virus (PRRSV) were collected from viremic sera from the (modified live vaccine) MLV-vaccinating and non-vaccinating farms from 2007 to 2008. The samples were phylogenetically analyzed with previous ORF5 sequences, including type I Korean PRRSV, and previously reported or collected sequences from 1997 to 2008. A MN184-like subgroup of type II Korean PRRSV was newly identified in the viremic sera collected from 2007 to 2008. And of the type I PRRSVs, one subgroup had 87.2~88.9% similarity with the Lelystad virus, showing a close relationship with the 27~2003 strain of Spain. The maximum parsimony tree of type II PRRSV from 1997 to 2008 showed that they had evolved to four lineages, subgroups 1, 2, 3 and 4. Most of the recently collected type II PRRSVs belonged to subgroup 4 (48%). The region of three B-cell epitopes and two T-cell epitopes of ORF5 amino acids sequences was considerably different from the MLV in subgroups 3 and 4. In conclusion, the existence of type I PRRSV, which was genetically different from Lelystad virus (Prototype of type I PRRSV), and heterologous type II PRRSVs of viremic pigs detected even in the MLV-vaccinating farms indicated the need for new vaccine approaches for the control of PRRSV in Korea.