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991.
Navarro S Vela N García C Navarro G 《Journal of agricultural and food chemistry》2003,51(25):7359-7365
The persistence of two herbicides, simazine and terbuthylazine, and appearance of their principal dealkylated chloro-s-triazine metabolites have been studied in agricultural soil after the addition of urban sewage sludge as organic amendment. Both herbicides and metabolites were monitored during long-term laboratory incubation (140 days) and analyzed by gas chromatography with a nitrogen-phosphorus detector (GC-NPD). Residues were confirmed by gas chromatography with a mass selective detector (GC-MSD). A sonication microextraction method was used to extract the compounds. The organic amendments used were urban sewage sludge and the humic fraction of this sludge, to increase the organic matter content of the soil from 1% to 2%. For both compounds, simazine and terbuthylazine, the degradation began earlier in the amended soils. Simazine showed a higher dissipation rate than terbuthylazine, the percentage of the former at the end of the experiment being lower than 2% in all cases, while for terbuthylazine the corresponding percentage ranged from 5% to 46%. Organic amendment, mainly its humic fraction, caused a certain stabilization of terbuthylazine in the soil, but did not greatly influence the residual amount of simazine at the end of the experiment. The periodic aeration of the soil caused a greater degradation in the case of terbuthylazine. Only mono-deethylsimazine and deethylterbuthylazine were isolated from the soil during the time the experiment lasted, while the di-deethylated metabolite of simazine was not found. 相似文献
992.
Hong Pan Yong Li Xiongming Guan Jiangye Li Xiaoya Xu Jun Liu Qichun Zhang Jianming Xu Hongjie Di 《Journal of Soils and Sediments》2016,16(3):896-908
Purpose
Nitrification and denitrification, two of the key nitrogen (N) transformation processes in the soil, are carried out by a diverse range of microorganisms and catalyzed by a series of enzymes. Different management practices, such as continuous grazing, mowing, and periodic fencing off from grazing, dramatically influenced grassland ecosystems. This study aimed to examine the effects of management practices on the abundance and community structure of nitrifier and denitrifier communities in grassland ecosystems.Materials and methods
Soil samples were collected from a semiarid grassland ecosystem in Xilingol region, Inner Mongolia, where long-term management practices including free-grazing, different periods of enclosure from grazing, and different frequencies of mowing were conducted. Real-time quantitative polymerase chain reaction (Q-PCR), denaturing gradient gel electrophoresis (DGGE), sequencing, and phylogenetic analysis were applied to estimate the abundance and composition of amoA, nirS, nirK, and nosZ genes.Results and discussion
The ammonia-oxidizing archaea (AOA) amoA copies were in the range 5.99?×?108 to 8.60?×?108, while those of ammonia-oxidizing bacteria (AOB) varied from 3.02?×?107 to 4.61?×?107. The abundance of AOA was substantially higher in the light grazing treatment (LG) than in the mowing treatments. The quantity and intensity of DGGE bands of AOA varied with pasture management. In stark contrast, AOB population abundance and community structure remained largely unchanged in all the soils irrespective of the management practices. All these results suggested that ammonia oxidizers were dominated by AOA. The higher gene abundance and greater intensity of DGGE bands of nirS and nosZ under the enclosure treatments would suggest greater stimulated denitrification. The ratio of nosZ/(nirS?+?nirK) was higher in mowing treatments than in the free-grazing and enclosure treatments, possibly leading to more complete denitrification. Correlation analysis indicated that soil moisture and inorganic nitrogen content were the two main soil environmental variables that influence the community structure of nitrifiers and denitrifiers.Conclusions
In this semiarid neutral to alkaline grassland ecosystem under low temperature conditions, AOA mainly affiliated with Nitrososphaera dominated nitrification. These results clearly demonstrate that grassland management practices can have a major impact on nitrifier and denitrifier communities in this semiarid grassland ecosystem, under low temperature conditions.993.
Anushka Upamali Rajapaksha Meththika Vithanage Sang Soo Lee Dong-Cheol Seo Daniel C. W. Tsang Yong Sik Ok 《Journal of Soils and Sediments》2016,16(3):889-895
Purpose
Sulfamethazine (SMT) is increasingly detected in environmental matrices due to its versatile use as antibiotics. We aimed to investigate the benefits and roles of steam activation of biochars with respect to SMT sorption kinetics and equilibrium sorption.Materials and methods
Biochars were produced from burcucumber plant and tea waste using a pyrolyzer at a temperature of 700 °C for 2 h. The biochar samples were treated with 5 mL min?1 of steam for an additional 45 min for post-synthesis steam activation. The SMT sorption on the unmodified and steam activated biochars were compared.Results and discussion
The time taken to reach equilibrium was significantly less for steam activated biochars (~4 h) than non-activated biochars (>24 h). Up to 98 % of SMT could be removed from aqueous solutions by steam activated biochars. The sorption kinetic behaviors were well described by the pseudo-second model and SMT sorption rates of steam activated biochars (k 2?~?1.11–1.57 mg g?1 min?1) were significantly higher than that of the unmodified biochars (k 2?~?0.04–0.11 mg g?1 min?1) because of increased availability of accessible porous structure with averagely larger pore diameters. Moreover, the equilibrium sorption on the unmodified biochars was significantly influenced by increasing solution pH (~30–50 % reduction) because of speciation change of SMT, whereas steam activated biochars manifested much stronger sorption resilience against pH variation (~2–4 % reduction only) because the enhanced porosity offset the effect of unfavorable electrostatic repulsion.Conclusions
The observed features of steam activated biochars would render their applications more versatile and reliable in field throughout changeable environmental conditions.994.
Celia Dias-Ferreira Rosinda L. Pato Jorge B. Varejão Alexandre O. Tavares Antonio J. D. Ferreira 《Journal of Soils and Sediments》2016,16(11):2594-2605
Purpose
This work analyzes polychlorinated biphenyl (PCB) and heavy metal contamination in fluvial sediments and soils in an urban catchment, according to the geo-accumulation index and to soil and sediment quality guidelines. The catchment is located in Coimbra, Portugal, being affected by frequent flooding, and its main stream is a tributary to one of the major rivers in Portugal (Mondego). Given the presence of industrial activities over time, some inputs of pollutants are expected, but so far, the legacy of historic pollution in this catchment has not yet been investigated.Materials and methods
Twenty-five samples were collected from nine sampling sites at the depths of 0–20, 20–40 and 40–60 cm (to provide a historic perspective) along longitudinal profiles (streamlines) and in soils downstream of pollution sources. These samples were analyzed for six heavy metals (Cu, Cr, Pb, Cd, Zn, Ni), organic carbon, pH and ten PCBs (IUPAC numbers 28, 30, 52, 101, 138, 153, 166, 180, 204, 209).Results and discussion
Total PCB concentrations ranged 0.47–5.3 ng g?1 dry weight (dw), and levels increase from the bottom to the top layers, suggesting an increased input over the last 100 years. PCB congener distribution shows the dominance of hexachlorobiphenyls, especially PCB138, suggesting the existence of local sources. PCB levels did not exceed sediment quality levels, placing sediments/soil under class 1 (not contaminated) or class 2 (trace contamination) with respect to PCB. All six metals exceeded the lowest effect level for sediment quality criteria, and three (Cd, Pb and Zn) largely exceeded the clean levels for dredged materials, placing sediments in class 5 (heavily contaminated). Sampling site S1 presented the highest concentrations of Zn, Pb and Cd, and historic vehicle traffic was identified as the most likely source, given the vertical and horizontal profiles.Conclusions
High levels of Pb, Cd and Zn were found in fluvial sediments at some locations of the Loreto catchment, likely from historic traffic sources. This urban area is frequently affected by flooding events and is currently being subject to urban redevelopment. During these events/actions, historic pollutants in the sediments might surface and be redistributed, impacting the downstream ecosystem of the major Mondego River or increasing the risk of exposure of the urban population.995.
Seasonal patterns of root-surface phosphatase activities in a Mediterranean shrubland. Responses to experimental warming and drought 总被引:2,自引:0,他引:2
Mediterranean ecosystems are water limited and the current general circulation Models (GCM) and ecophysiological models forecast
a warming and a further increase of drought in the next decades. A stronger water stress can decrease the capacity for nutrient
absorption by plants. We conducted a field experiment to simulate forecasted drought and warming in a Mediterranean calcareous
shrubland to assess the performance of root-surface phosphatase activities of the dominant shrub Globularia alypum. These enzyme activities were higher in autumn and spring, when the climate conditions were optimal for plant activity, than
in summer or winter, when there was either lack of water or cold temperatures. A decrease in soil moisture in drought plots
decreased root-surface phosphatase activity (29% in summer and 25% in autumn). The decrease in root-surface phosphatase activity
in drought plots coincided with a decrease in P leaf concentrations and P accumulation in aboveground biomass and loss of
photosynthetic capacity of some dominant shrub species of this ecosystem, and with a tendency to increase total soil-P. These
results suggest that the expected drier conditions in this Mediterranean shrubland in the next decades will slow down the
P uptake by plants, thereby, diminishing the P contents in biomass and increasing total P contents in soil in non-available
forms and that this can be, in part, attributable to a result of the decrease in root-surface phosphatase activity. 相似文献
996.
Background, Aim and Scope
Contamination of soils does not only occur on their surface over large areas, but also in depth. Therefore a characterization
of soil state after pollution demands a three-dimensional soil sampling, by what a large number of samples has to be analyzed.
Analytical results could be evaluated by multivariate statistical methods, which have already been used for the evaluation
of data sets containing results from soil sampling of two dimensions like areas or single profiles. In this case study, multivariate
statistical methods were applied to investigate structure and interactions between features in a data set containing results
of three-dimensional soil sampling. The investigated soil profiles were contaminated by emissions of a former cement and phosphate
fertilizer plant. The aim of this study was to determine the remaining extent of contamination and to analyze whether pollutants
are mobilized and vertically transported within the profiles.
Materials and Methods:
Three soil profiles were sampled in the surroundings of the plant. Grain size, organic and carbonatic bonded carbon, pH value,
and the total contents of Ca, Cd, Co, Cu, F, Fe, K, Mn, Mg, Na, Ni, P, Pb, and Zn were determined. The resulting data set
was evaluated by cluster analysis, linear discriminant analysis, and principal components analysis. The sequential extraction
procedure according to Zeien and Brümmer was applied to analyze the binding properties of Ca, Cd, Cu, Na, Pb, and Zn from
selected samples.
Results:
Cd was identified as contaminant of the top soils. The pH values of the bottom soils were determined to be in alkaline range,
which is unnaturally high. Variables were clustered according to enrichment of variables in top soils. The samples were classified
regarding their pollution state and their substrate by cluster analysis, which was confirmed by linear discriminant analysis.
Geogenic and anthropogenic sources of variables as well as relationships between variables like the binding of heavy metals
at organic matter were detected by using principal components analysis. The binding of heavy metals at organic matter in the
top soils was confirmed by the results of the applied sequential extraction. A vertically altered distribution of Na binding
was determined.
Discussion:
According to the current soil conditions, the uptake of heavy metals had probably occurred by the over ground part of plants
during the deposition. The distribution of Na should likely result from the vertical transport of Na, which would also explain
the high pH values of the bottom soils by ion exchange. Altogether, the main amount of deposited Ca, F, Na, P, and heavy metals
is likely nearly insoluble bound in the top soils.
Conclusions:
Ten years after the end of production, the pollution of top soils in the surroundings of the former plant is still high. However,
regarding the ecotoxicological relevance the now explored interactions between several soil features and elements strongly
indicate that there is no short-term to medium-term risk of a mobilization of the deposited elements with the exception of
Na.
Recommendations and Perspectives:
The results of this case study prove that multivariate statistical methods are powerful tools to explore interactions of variables
and relationships in a data set derived from three dimensional soil sampling. The methods applied in this work can be highly
recommended for evaluations of large data sets resulting from two- or three-dimensional samplings. Multivariate statistical
methods enable the characterization of soils and their pollution state in a simple and economic way. 相似文献
997.
Xiao-Hua Qi Ming-Fang Zhang Jing-Hua Yang 《Genetic Resources and Crop Evolution》2007,54(8):1709-1716
Sequence variation of nuclear internal transcribed spacer regions of ribosomal DNA (ITS1, 5.8S rRNA and ITS2) from Chinese
vegetable mustards (AB-genome) and its putative parents Brassica rapa (the A-genome) and Brassica nigra (the B-genome) were used to investigate the molecular phylogeny and the probable evolutional pattern of this amphidiploid
species that uniquely formed in China. Totally, 16 accessions of Chinese vegetable mustard those covering nearly all the diverse
variations were included in this study, and together with three accessions of B. rapa and one accession of B. nigra. The results disclosed two strongly supported clades, one containing four accessions of vegetable mustard which have closer
relationship with B-genome species “B.nigra” lineage and the other containing 12 accessions of B. juncea and three A-genome accessions. This classification was in disagreement with the evidence from chloroplast DNA, mitochondrial
DNA, nuclear DNA restriction fragment length polymorphism (RFLP), which suggested that B. juncea was closely related to the A-genome type. For the incongruence, we speculated that the B. juncea crops derived from Chinese have evolved through different recombined events of the diploid morphutypes and evolved unidirectional
concerted evolution. The traditional phenotypic classification of B. juncea was not wholly supported by ITS results, and hence the phylogenetic relationships among these subspecies need to be reconsidered
on molecular level. 相似文献
998.
Hernández-Castro R Martínez-Chavarría L Díaz-Avelar A Romero-Osorio A Godínez-Reyes C Zavala-González A Verdugo-Rodríguez A 《Veterinary journal (London, England : 1997)》2005,170(3):359-363
Nasal swab samples from clinically healthy California sea lions pups (Zalophus californianus) from six different reproductive rookeries in the Gulf of California were collected to determine the type and frequency of the representative aerobic bacterial microflora of their nasal mucosa. A total of 114 samples were examined and 100 bacterial isolates were identified and typified by microbiological and biochemical standard tests. Fifty four isolates corresponded to Gram positive bacteria (54%) and 46 isolates to Gram negative bacteria (46%). Fifteen bacterial genera were identified, including Micrococcus, Arcanobacterium, Corynebacterium, Moraxella, Neisseria, Escherichia, Kurthia, Acinetobacter, Staphylococcus, Brevibacillus, Bacillus, Klebsiella, Stenotrophomonas, Pseudomonas and Aeromonas. The most frequently isolated genera were Moraxella (24%), Micrococcus (18%), and Corynebacterium (15%). These results show the presence in the nasal cavity of sea lions of several microorganisms. Although considered part of the normal microflora, they may also be opportunistic pathogens for their hosts and may act as a potential natural sentinel of environmental changes. 相似文献
999.
Mukesh Bhakat Tushar K. Mohanty Ashok K. Gupta Virendra S. Raina Biswajit Brahma R. K. Mahapatra M. Sarkar 《Tropical animal health and production》2010,42(7):1363-1366
Effect of Foot and Mouth disease (FMD) vaccination was studied on semen quality parameters of 19 Karan Fries (KF) and eight
Murrah (MU) breeding bulls during the period 2002 to 2004 at Artificial Breeding Complex, NDRI, Karnal. A total of non-vaccinated
155 KF and 72 MU bulls' ejaculates were taken as control, while 169 KF and 51 MU bulls' ejaculates, collected after vaccination,
were used to study the effect of vaccination stress. The results showed that FMD vaccination had no significant (P > 0.05) effect on ejaculate volume and total volume per day of semen in both KF and MU bulls. Volume of semen increased slightly
during post-vaccination period in both the breeds. After FMD vaccination, there was significant (P < 0.01) decrease in mass activity (2.27 ± 0.06 vs. 1.67 ± 0.07 and 2.49 ± 0.09. vs. 1.75 ± 0.10, for KF and MU, respectively),
initial motility (56.89 ± 0.03% vs. 44.62 ± 0.02% and 62.26 ± 0.04% vs. 47.08 ± 0.05%, for KF and MU, respectively), sperm
concentration (754.19 ± 23.96 vs. 554.14 ± 22.95 × 106/ml and 848.61 ± 33.65 vs. 571.57 ± 39.99 × 106/ml, for KF and MU, respectively), and total sperm output per ejaculate (3,685.94 ± 158.40 vs. 2,781.54 ± 151.70 × 106 and 2,218.75 ± 133.14 vs. 1,582.84 ± 158.20 × 106, for KF and MU, respectively). Application of FMD vaccine had significantly (P < 0.05) adverse effect on most of the seminal attributes during post-vaccination in KF and MU buffalo bulls. So, the spermiograms
affected following vaccination suggest that in bovines, the semen collection and preservation should be suspended till normal
fertility of sperm is restored to avoid the failure of conception from artificial insemination using such semen. 相似文献
1000.
Ba A Lesnoff M Poccard-Chapuis R Moulin CH 《Tropical animal health and production》2011,43(6):1101-1109
The herds of 95 families were monitored for 1 year in eight villages in the cotton-growing region of southern Mali. In 2006–2007,
reproduction performances were average, with 0.54 calvings/year per cow, and mortality was low. Herd numerical productivity
is not very high, less than 0.13/year, because of the high proportion of males kept for animal draught. Depending on the herd
size, the behaviour of the families differs, in terms of off-take and in-take of animals. Families that only have one or two
draught animals seek to increase their animal draught capacity, with a negative net off-take (−0.13/year). Families with two
to three cows have a very low net off-take (0.02/year), with culling of adult animals compensated by purchase. They therefore
capitalised this year, with an annual herd growth of 8%. Families with a very large herd (20 to 50 cows) take off more of
their stock, with a net off-take of 0.08/year (very few animal purchases) and make a stock growth of 5%. And finally, families
with an average-sized herd (6 to 19 cows) take off the whole of the year’s production, with a net off-take of 0.11/year and
a nil stock growth rate. The use of a demographic model made it possible to measure the sensitivity of the productivity rate
to the different demographic parameters. 相似文献