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941.
Carmen G. Méndez-García Mayra Y. Luna-Porres Maria E. Montero-Cabrera Marusia Renteria-Villalobos Bernardo Pérez-Cázares Rafael García-Tenorio 《Journal of Soils and Sediments》2016,16(7):1970-1985
Purpose
The El Granero reservoir is the last reservoir of the Rio Conchos before it joins the Rio Grande at the Mexico–USA border. This reservoir, together with the San Marcos reservoir, is located in the arid region of Chihuahua, Mexico. High, naturally occurring radioactivity levels, as well as high arsenic (As) concentrations, have been found in both reservoirs. The main goal of this research was to establish the spatial and temporal distribution of trace and radioactive elements in surface sediments and cores collected from these reservoirs.Materials and methods
Sediment cores were dated using 210Pb and 137Cs measurements and applying the constant rate of supply (CRS) model. Major, trace, and radioactive elements were determined in surface samples and three sediment cores. Radioactive elements were determined by both alpha and gamma spectrometry. Major and trace elements were determined by inductively coupled plasma optical emission spectrometry (ICP-OES) using the EPA 3051a method. Enrichment factors (EF), contamination factors (CF), and pollution load indexes (PLI) were calculated in order to identify the human impact in both reservoirs, whereas the chemical index weathering (CIW) was used to assess differences in the degree of weathering.Results and discussion
High uranium (U) enrichment (EFs?=?24.9–54.7) was observed in core layers at the San Marcos reservoir, while in surface sediments, this enrichment was lower. The high variability of lead (Pb) and As in sediment cores from the Granero reservoir was attributed to human influence. Arsenic and Pb enrichment differences between entry and exit sediment cores were explained by the filtering capabilities of the elongated shape, the topography, and the presence of plants on the reservoir’s bed. The highest PLI was found at the entrance core of the Granero reservoir.Conclusions
The natural element concentration levels of As, Pb, and U were established at the Granero reservoir. High EFs for As and Pb suggest an anthropogenic origin of these pollutants at specific time intervals. High U concentrations in the San Marcos area are explained as naturally occurring. The concentrations of As in most of the studied sediments could pose a risk to human health by As ingestion, since they are above the probable effect level (PEL).942.
Purpose
The potential heat load and stormwater reduction of the anthropogenic, lightweight soil systems, such as green roofs, are valuable to heat island effect mitigation and to urban water management. Benefits of extensive green roofs, as widely used vegetated roof system with very thin soil layer, could be threatened by temporal changes of the soil structure.Materials and methods
Green roof raised beds filled with two different anthropogenic soils (artificially constructed stripped topsoil with admixed crushed bricks and a commercial mixture of a technogenic substrate) were built to investigate the benefits of such systems in a temperate climate. These two soils were chosen with the intent to compare their thermal and water regime. One soil is expected to be favorable for hydrological functioning, whereas the other one for the thermal performance. Temperature and water balance measurements complemented with meteorological observations and knowledge of physical properties of the soil substrates provide the basis for detailed analysis of a thermal and hydrological regime in green roof raised beds. Moreover, the state of pedogenesis was studied on undisturbed soil samples by means of X-ray computed tomography.Results and discussion
The water balance of green roof raised beds was calculated for a whole vegetation season and individual rainfall events. Runoff from raised beds was 38 and 63 % of received rainfall. On the basis of a detailed analysis of individual rainfall events, rainfall-runoff dependency was found for both raised beds. The difference between measured actual evapotranspiration and calculated potential evapotranspiration was discussed on the period with contrasting conditions in terms of moisture stress. Thermal characteristics of soil substrates result in a highly contrasting diurnal variation of soil temperatures. Analysis of X-ray computed tomography-derived macroporosity profiles reveals significant temporal changes in the soil comprised of the stripped topsoil with admixed crushed bricks.Conclusions
Both green roof systems were able to reduce heat load of roof construction when comparing with the concrete roof construction. Similarly, received rainfall was significantly reduced. The extent of rainfall reduction mainly depends on soil, vegetation status, and experienced weather patterns. Methods used for non-invasive imaging proved to be beneficial for studying of soil structure changes.943.
Maria Durban Christine A. Hackett James W. McNicol Adrian C. Newton William T. B. Thomas Iain D. Currie 《Journal of Agricultural, Biological & Environmental Statistics》2003,8(1):48-66
This article examines the practical use of semiparametric models in the analysis of field trials—that is, models with parameterized treatment effects and additive terms derived by a data-driven approach using a locally weighted running line smoother (loess). We discuss graphical methods to identify spatial structure in the data and model selection procedures to choose the degree of smoothing. Once the spatial part of the model has been chosen, hypotheses about the treatment effects may be tested. Semiparametric models are used to analyze two barley field trials exhibiting spatial trends. The first has a single experimental treatment and a row-column design. The second has a split-plot design, and we use a semiparametric model which accounts for the randomization at the different strata of this design. We compare the semiparametric analyses with classical analyses of variance and with alternative spatial models. We find that semiparametric models give a good insight into spatial variation in the field and can improve the precision of parameter estimates. 相似文献
944.
Paola Bortot Carlo Gaetan 《Journal of Agricultural, Biological & Environmental Statistics》2016,21(3):531-547
Two features are often observed in analyses of both daily and hourly rainfall series. One is the tendency for the strength of temporal dependence to decrease when looking at the series above increasing thresholds. The other is the empirical evidence for rainfall extremes to approach independence at high enough levels. To account for these features, Bortot and Gaetan (Scand J Stat 41:606–621, 2014) focus on rainfall exceedances above a fixed high threshold and model their dynamics through a hierarchical approach that allows for changes in the temporal dependence properties when moving further into the right tail. It is found that this modelling procedure performs generally well in analyses of daily rainfalls, but has some inherent theoretical limitations that affect its goodness of fit in the context of hourly data. In order to overcome this drawback, we develop here a modification of the Bortot and Gaetan model derived from a copula-type technique. Application of both model versions to rainfall series recorded in Camborne, England, shows that they provide similar results when studying daily data, but in the analysis of hourly data the modified version is superior. 相似文献
945.
Mario A. Pagnotta Alfredo Impiglia Oronzo A. Tanzarella Miloudi M. Nachit Enrico Porceddu 《Genetic Resources and Crop Evolution》2005,51(8):863-869
The durum wheat landrace Haurani (Triticum durum Desf.) is grown under contrasting climatic regions of Syria from Deir Ezzor, in the North-East (230 m altitude, 150 mm mean annual rainfall), to Qunaytra, in the South-West (1060 m altitude, 825 mm mean annual rainfall). In order to assess the genetic variation between and within Haurani populations, samples from eight provinces of Syria (Daraa, Damascus, Qunaytra, Deir Ezzor, Hassakeh, Aleppo, Homs and Hama) were analysed by RFLPs and seed storage proteins of glutenin subunits as markers. The analyses showed the presence of genetic polymorphisms in all populations with the highest values in those from Homs and Hassakeh. Moreover, the results point out differences in genetic distances between populations; some populations were further apart, such as Damascus and Aleppo, whereas others were closer to each other, for instance Homs and Hama. Cluster analysis identified two distinct groups of populations, characterized by geographical proximity, with similar rainfall and altitude. It is suggested that the similarity of landraces at locations close to each other might be the result of more frequent seed exchanges between farmers or of gene flow due to 5% estimated outcross rate of Haurani. 相似文献
946.
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.947.
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.948.
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.949.
Vinod Kumar Yadav Sandeep Kumar Ravindra K. Panwar 《Genetic Resources and Crop Evolution》2007,54(6):1285-1289
The present investigation was carried out on fifteen germplasm lines of Pisum sativum L. were used for characterization using Randomly Amplified Polymorphic DNA (RAPD) markers. While 12 random primers were taken,
out of them 11 primers gave amplification. These primers gave a total of 133 bands out of which 106 were polymorphic. Genetic
similarities of the RAPD profiles were estimated by using Jaccard’s coefficient with NTSYSpc 2.0 software. The similarity
index values ranged from 0.263 to 0.793 indicating the presence of enormous genetic diversity at molecular level. A dendrogram
generated by cluster analysis divided fifteen fieldpea genotypes into two Groups A and B. Major Group A have five genotypes
and major Group B have nine genotypes. 相似文献
950.
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