Phosphorus dynamics along a river continuum

Changes in phosphorus concentration and form along 110 km of the River Swale in Northern England were examined over a 2-year period during 1998-2000. This study aimed to use these data to identify the importance of within-channel storage on phosphorus dynamics and to determine the changes in longitudinal transport of phosphorus along a river continuum. The catchment was divided into three contrasting zones: the upland, dominated by sheep farming; a transitional zone, and an intensively-farmed lowland, impacted by sewage inputs. Samples, taken at the downstream extent of each zone at approximately 2-day intervals, were analysed for total phosphorus (TP), total dissolved phosphorus (TDP) and soluble reactive phosphorus (SRP), all of which increased in concentration downstream. SRP concentrations were highest in summer and during low flows, although 92% of phosphorus was exported between autumn and spring. The TDP in the upper and transitional zones consisted of both soluble reactive and un-reactive phosphorus, but in marked contrast was almost entirely in soluble reactive form in the lowland. The majority (85%) of phosphorus exported from the catchment was generated within the lowland, due to sewage inputs and losses from intensive agricultural land. It was predominantly particulate-bound, due to interactions of dissolved phosphorus with suspended sediment. The upland contributed less than 5% to the TP annual budget. Intensive river water monitoring highlighted that the lowland dominated phosphorus export during the rising stage of storms (indicating a rapid mobilisation of fine phosphorus-rich sediment), whereas the transitional zone became dominant on the falling stage (due to greater diffuse phosphorus input).     

Phosphorus dynamics in hypereutrophic lake sediments

The sediments of two hypereutrophic lakes (Stone Lake, Michigan and Lake Charles East, Indiana) were studied to determine phosphorus sorption and release tendencies as they vary seasonally. Techniques used were chemical extractions of phosphorus forms from core fractions and the incubation of undisturbed cores in the laboratory under ambient conditions of temperature and dissolved oxygen. The uptake of phosphorus during aerobic periods was found to be in accord with previously observed trends in that the amount sorbed was proportional to overlying phosphorus concentration supporting an adsorption type of model. Phosphorus was given off during anoxic periods, however, the specific release rates could not be correlated with the gradient of interstitial phosphorus to overlying phosphorus concentrations as reported by others. Rather, release rates were closely correlated with average interstitial phosphorus concentrations. A diffusion model is presented, applicable to systems similar to those studied, in which soluble interstitial phosphorus varies from a greatly elevated concentration in close proximity to sediment particle surfaces to levels approaching those of overlying phosphorus.     

Phosphorus cycling through phosphine in paddy fields

Phosphine emission fluxes from paddy fields, phosphine ambient levels in air, and the vertical profile of matrix-bound phosphine in soil have been measured throughout the growing season of rice in Beijing, China. It was found that both the seasonal and diurnal emission fluxes and ambient levels fluctuate significantly. During the drainage period, phosphine released from the soil with the highest diurnal average flux on the first period of drainage (approx. 17.7 ng m(-2) h(-1)), whereas its highest ambient level (approx. 250 ng m(-3)) occurred at 06.00 h. During the flooded period, phosphine emission was low, and the peaks of phosphine emissions occurred at midnight. The average flux of PH3 emission for the whole season was found to be approximately 1.78 ng m(-2) h(-1). The mass fraction of matrix-bound phosphine is approximately 0.18 approximately 1.42 x 10(-7) (m/m) part of organic phosphorus or 3.4 approximately 9.2 x 10(-9) (m/m) part of total phosphorus in paddy soil. The amount of phosphine emitted to the atmosphere was only a small fraction of the phosphine that remained in the soil in the matrix-bound form. Soil serves both as the source and the sink of PH3.     

降雨增加对多年冻土区铁路路基水热影响研究

近50 a青藏高原湿化趋势显著,降雨变化导致地表能量平衡过程、活动层水分状况和水热输运过程改变。以青藏高原北麓河铁路路基试验段水分监测为基础,基于土壤–地表–大气能量平衡的冻土水–汽–热耦合模型研究在未来降雨变化情景下,降雨对冻土路基水热的影响机制与过程。结果表明:近6 a路基水分监测显示,虽然青藏高原年降雨量变化较大,夏季降雨引起土体表层水分短期显著波动,但长期路基含水量并未明显累积,路基蒸发、液态水与水汽运移显著;在未来湿化背景下,年降雨量增大导致地表潜热增大地表土壤热通量减小,降雨增大导致的热传导通量减小量比液态水对流热通量增大更大,人为冻土上限抬升;降雨增加缓解了路基工程对下伏多年冻土的热扰动,但降雨增加导致活动层水分累积,增大路基冻胀和融沉灾害风险。     

Patterns of macrophyte distribution within a Breton brook compared with other study scales

In order to assess macrophyte organisation processes and patterns, with particular reference to corridor effects and connectivity, macrophyte distributions and floristic assemblages were studied within a whole brook system divided into 208 consecutive 50-m-long units in summer. The results were compared with four 5-m-long plots of the downstream part of the brook, and with 196 stations located on the river basin.Four main types of longitudinal distribution were emphasised: macrophytes could be upstream-specific ortolerant, downstream-specific, -tolerant or mainly downstream, ubiquitous or confined to one tributary. The ecological tendencies of some macrophytes were pointed out from ecological profiles. Vegetational groups were determined by correspondence analysis: sunny upstream areas were dominated by heliophilous vascular spring hydrophytes while shaded upstream areas were characterised by aquatic bryophytes; in the larger downstream brooks, three layers were observed: helophytes, vascular rheophytes and aquatic bryophytes.The comparison with the two other levels showed how mapping was useful to emphasise species distribution. A possible misinterpretation of macrophyte ecology was pointed out when studying ecological profiles in a particular brook versus a stratified sampling on the river basin. The intermediate position of the brook in regard to the general typology of the river watercourse, and also its particularities due to general eutrophication of main course were shown. Then the relationships between the species distribution and the levels of organisation or human management were discussed and placed within the topics of fluvial corridor functioning, connectedness and connectivity. The use of other concepts such as ecotones, river continuum concept or functional sectors in hydrosystems was then attempted to understand some distribution and organisation features, and to forecast further research.     

Phosphorus sources,speciation and dynamics in the lowland eutrophic River Kennet,UK

This paper examines the behaviour of phosphorus (P) in a lowland chalk (Cretaceous-age) stream, the upper River Kennet in southern England, which has been subject to P remediation by tertiary treatment at the major sewage treatment works in the area. The effects of treatment are examined in relation to boron, a conservative tracer of sewage effluent and in terms of the relative contributions of soluble reactive phosphorus (SRP) loads from point and diffuse sources, and in-stream SRP loads. These results indicate a baseline reduction in in-stream SRP concentrations immediately following P-treatment of approximately 72%. Subsequent high flows result in a greater contribution of diffuse inputs and increases in SRP levels relative to the initial post-treatment period. The dynamics of SRP and particulate phosphorus (PP) are examined under a wide range of river flow conditions. Given the flashy nature of near-surface runoff in the River Kennet, sub-weekly (daily automated) sampling was used to examine the dynamics in SRP and PP concentrations in response to storm events. Simple empirical models linking weekly SRP concentrations with flow were developed. The empirical models were successfully applied to the daily data, to partition TP measurements and provide an estimate of daily SRP and PP concentrations. Mass balance studies were used to examine net gains and losses along the experimental river reach and indicate large net losses (up to 60%) during the extreme low flows and high SRP concentrations prior to P-treatment, which may be linked to extensive epiphytic growth. Phosphorus dynamics and response to P-treatment are discussed in relation to hydrological controls in permeable chalk catchments and wider implications for eutrophication management are examined.     

Experimental study on debris-flow velocity control mechanism with baffles in a drainage channel

Bulletin of Engineering Geology and the Environment - Debris-flow deceleration baffles can be used to reduce flow velocity in a large gradient drainage channel and the scouring rate of concrete at...     

Performance analysis of vortex flow through a swirler by computational fluid dynamics technique

ABSTRACT

In the recent era, it is preferred for energy to be produced from renewable energy resources rather than from non-renewable resources. That’s why the non-renewable sources gradually become obsolete due to its main drawback of creating pollution. On the other hand, the set-up cost for renewable energy resources is very high, so it is difficult to afford financially. Therefore, researchers started their research on pollution control from the non-renewable resources. In this work, the emission level of diesel engine has been successfully planned to control by inducing a variable geometry swirler in the inlet manifold, which will enhance the turbulence inside the cylinder, hence increasing homogeneity between air–fuel composition and low emission. In this paper, it has been shown numerically and justified how the designed geometry of the swirler will increase the efficiency of combustion to control the emission from an I.C. engine.     

Mapping seepage in the tailrace channel,Bhama-Askhed dam: a case study

The Bhama-Askhed irrigation dam, with a side spillway, is located on the Bhama river, Maharashtra, India where the bedrock is chlorophacitic porphyritic basalt. During the monsoon of 2005, thirteen reinforced concrete panels in the tailrace channel area were raised and displaced, exposing the underlying rock. Continuous oozing of water was observed in the tailrace channel at RD 83 m. Nuclear logging and tracer studies were conducted in boreholes drilled 6 m below the foundation level, to identify weak and porous zones and ascertain the seepage path. The nuclear logging identified weak zones at about 34 m depth corresponding to a red breccia zone. The tracer studies established the interconnection between the red breccia in the dam foundation and the oozing water at RD 83 m in the tailrace channel. The studies assisted in the determination of suitable remedial measures for the treatment of the red breccia zone and the recommendation of proper drainage holes in the tailrace channel area to release uplift pressures.     

Plasma organochlorine levels and subsequent risk of breast cancer among Japanese women: a nested case-control study

To our knowledge, no prospective study has examined the association between blood levels of organochlorines and breast cancer risk in Asian countries. Here, we tested the hypothesis that higher blood levels of organochlorines are associated with an increased risk of breast cancer in Japanese women. A total of 24,226 women subjects of the Japan Public Health Center-based Prospective Study aged 40 to 69 years who responded to the baseline questionnaire and provided blood in 1990-1995 were followed to December 2002. During 10.7 years follow-up, 144 cases of breast cancer were newly diagnosed. Two matched-controls for each case were selected from the cohort. Plasma levels of p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT), p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE), hexachlorobenzene (HCB), and beta-hexachlorocyclohexane (beta-HCH) were measured. A conditional logistic regression was used to estimate the odds ratio (OR) of breast cancer according to cholesterol-adjusted organochlorine levels based on 139 matched pairs. We found no statistically significant positive association between plasma organochlorine level and breast cancer risk. Adjusted ORs for p,p'-DDT, HCB, and beta-HCH were less than 1. For p,p'-DDE, adjusted OR for the highest versus lowest quartile was 1.48 (95% confidence interval 0.70-3.13; p for trend=0.25). A stratified analysis by menopausal status showed positive associations for p,p'-DDT and p,p'-DDE in premenopausal but not postmenopausal women, although without statistical significance. Our data do not support the hypothesis that plasma levels of p,p'-DDT, p,p'-DDE, HCB, and beta-HCH are associated with an overall increased risk of breast cancer among Japanese women.     

Effect of personal and microclimatic variables on observed thermal sensation from a field study in southern Brazil

Urban climate, which is influenced by land use patterns, heat-generating activities, and the physical texture of urban fabric, has a great impact on outdoor comfort as well as on a building’s energy consumption. A climate-responsive urban planning can provide optimal, comfortable thermal conditions not only for the permanence of humans in outdoor spaces but also reducing the need of air conditioning systems in buildings. The purpose of this article is to present results of an outdoor comfort research with passers-by in downtown Curitiba, Brazil (25°31′S, 917m elevation). Urban locations have been monitored regarding standard comfort variables: air temperature and humidity, wind speed and globe temperature. Alongside the quantitative assessment of comfort conditions, a survey of pedestrian’s thermal comfort perception according to ISO 10551 was carried out on each monitoring campaign by means of questionnaires with the local population. As a whole, from fourteen monitoring campaigns using a couple of weather stations, beginning on January 9 through August 12, 1654 valid comfort votes were obtained. In this paper, we perform a data consistency check, evaluating the relationship between personal (gender and age of respondents) and objective, microclimatic (comfort variables) factors on observed thermal sensation.     

Laboratory study on the open channel flow reaeration: a dimensional approach

Results of laboratory experiments on open channel flow reaeration are presented and commented on. The tests were designed on the basis of the classical dimensional analysis. They were carried out using three 15 m long channels with different cross-sections: 1) 0.5 m wide semi-circular cross-section; 2) 0.4 m wide rectangular cross section; 3) 0.2 m wide rectangular cross-section. The longitudinal bottom slope, the roughness and the flow discharge were varied independently. The disturbed equilibrium approach was adopted within an innovative experimental procedure, i.e. comparing the dissolved oxygen measures acquired in tests without de-oxygenation agent (hereinafter ‘white tests’) with those performed in runs with de-oxygenation agent (‘reaeration tests’). A new relationship between the reaeration coefficient and the hydrodynamic characteristics of an open channel is proposed. The relationship is applicable to a wide range of values of hydraulic characteristics not previously analysed in the literature and typical of small rivers.     

Changes in arsenic speciation through a contaminated soil profile: a XAS based study

An impacted soil located near an industrial waste site in the Massif Central near Auzon, France, where arsenical pesticides were manufactured, has been studied in order to determine the speciation (chemical forms) of arsenic as a function of soil depth. Bulk As concentrations range from 8780 mg kg(-1) in the topsoil horizon to 150 mg kg(-1) at 60 cm depth. As ores (orpiment As2S3, realgar AsS, arsenopyrite FeAsS) and former Pb- and Al-arsenate pesticides have been identified by XRD at the site and are suspected to be the sources of As contamination for this soil. As speciation was found to vary with depth, based on XRD, SEM-EDS, EPMA measurements and selective chemical extractions. Based on oxalate extraction, As is mainly associated with amorphous Fe oxides through the soil profile, except in the topsoil horizons where As is hosted by another phase. SEM-EDS and EPMA analyses led to the identification of arseniosiderite (Ca2Fe3+3(AsVO4)3O2.3H2O), a secondary mineral that forms upon oxidation of primary As-bearing minerals like arsenopyrite, in these topsoil horizons. These mineralogical and chemical results were confirmed by synchrotron-based X-ray absorption spectroscopy. XANES spectra of soil samples indicate that As occurs exclusively as As(V), and EXAFS results yield direct evidence of changes in As speciation with depth. Linear combination fits of EXAFS spectra of soil samples with those of various model compounds indicate that As occurs mainly As-bearing Fe(III)-(hydr)oxides (65%) and arseniosiderite (35%) in the topsoil horizon (0-5 cm depth). Similar analyses also revealed that there is very little arseniosiderite below 15 cm depth and that As(V) is associated primarily with amorphous Fe oxides below this depth. This vertical change of As speciation likely reflects a series of chemical reactions downward in the soil profile. Arseniosiderite, formed most likely by oxidation of arsenopyrite, is progressively dissolved and replaced by less soluble As-bearing poorly ordered Fe oxides, which are the main hosts for As in well aerated soils.     

双污泥脱氮除磷系统中聚磷菌的特性研究

采用平板分离技术、生理生化及吸磷试验,对连续流双污泥系统缺氧池内的聚磷茵特性进行了研究.结果表明:反硝化聚磷污泥和普通好氧聚磷污泥在性状上极为相似,其内源物质PHB及聚磷有着相同的变化规律;在缺氧池内同时存在着以氧和硝酸盐氮为电子受体的聚磷菌,并且二者存在着交叉.试验中得到5株(PAl-PA5)同时具有好氧和缺氧吸磷能力的聚磷茵,其中PA2、PA4(产碱菌属)和PA3(假单胞菌属)在两种环境下均表现出良好的吸磷效果;同时发现好氧吸磷能力很强的聚磷茵可能由于没有反硝化能力或反硝化能力很弱而在缺氧条件下未表现出吸磷作用;PA5(肠杆菌科)是一种很特殊的聚磷菌,其在好氧条件下有很好的吸磷效果,反硝化能力也很强,但缺氧吸磷效果却很差.     

Phosphorus retention in a coastal salt marsh in SE Spain

Total and inorganic soil P were extracted from a coastal salt marsh in SE Spain receiving eutrophicated water of urban and agricultural origin. The greatest P contents were obtained within the upper 10 cm of soil of those sectors of the salt marsh most affected by urban waste water effluents. Most of the P was extracted using HCl, indicating that it is mainly bonded to Ca compounds. Only in sites with low CaCO(3) content was the quantity of P associated with Fe and Al oxides and hydroxides (extracted with NaOH) noticeable.     

Experimental study of reinforced concrete beams strengthened with a GFRP channel and CFRP sheets

Glass–fibre‐reinforced polymer (GFRP) jackets were used in several different ways to improve the flexural and shear performance of reinforced concrete (RC) beams. The GFRP jacket increased both the ductility and the strength of the concrete beam. An experimental and analytical study was conducted to investigate the use of the GFRP channel in improving the flexural capacity of a RC wide beam. The parameters investigated in this study were stiffness, ductility and failure mode. The test results showed that using the GFRP channel significantly improved the flexural capacity of the RC wide beams. The tensile stresses due to the inclined cracks in the concrete can be transferred to the concrete on each side of the crack when interfacial bond activities are maintained. Copyright © 2008 John Wiley & Sons, Ltd.     

沥青混凝土摊铺机压实机构非线性动力学仿真

文中提出在一个 3自由度沥青混凝土摊铺机压实机构的一种非线性动力学模型基础上 ,通过计算机仿真 ,研究了该压实机构中的前后压实梁、振捣器和熨平板平台自身的振动规律 ,并讨论了构成这些振动信号的有关成分随激振油缸脉冲频率、振捣器振捣频率等变化的规律。     

煤制烯烃企业生产装置提高负荷浅析

简要介绍了中煤陕西榆林能源化工有限公司煤制烯烃项目一期的基本情况。分析了影响煤制烯烃企业各主生产装置高负荷运行的因素及提高运行负荷的方法。结合实际生产经验,总结了煤制烯烃企业延长运行周期的措施,确定了煤制烯烃企业最佳的生产负荷,可供同类企业借鉴参考。     

Experimental and analytical study on channel shear connectors in fiber-reinforced concrete

This paper investigates, experimentally and analytically, the capacity of channel shear connectors embedded in normal and polypropylene (PP) concrete. Limited testing is used to assess the accuracy of a proposed nonlinear finite element model for typical push-out test specimens. Using this model, an extensive parametric study is performed to arrive at a prediction for shear capacity of channel connectors in PP concrete. An equation, for inclusion in design codes, is suggested for the shear capacity of these connectors when used in PP concrete.