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41.
Exchanges of carbon and nitrogen between the atmosphere and terrestrial ecosystems involve a complex set of interactions affected by both natural and management processes. Understanding these processes is important for managing ecosystem productivity and sustainability. Management processes also affect the net outcome of exchanges of greenhouse gases between terrestrial ecosystems and the atmosphere. In developing a national carbon accounting system (NCAS) for Australia to account for emissions and removal of greenhouse gases to and from the atmosphere, a carbon:nitrogen mass balance ecosystem model (FullCAM) was developed. The FullCAM model is a hybrid of empirical and process modelling. The approach enables application to a wide range of natural resource management issues, because it is at land-management-relevant spatial and temporal resolution
and captures the main process and management drivers. The scenario-prediction capability can be used to determine the emissions consequences of different management activities. Because, in Australia, emissions of greenhouse gases are closely related to the retention of dead organic matter and the availability of nitrogen for plant growth, the carbon and nitrogen cycling as modelled are good indicators of ecosystem productivity and condition. The NCAS also emphasizes the advantages of a comprehensive and integrated approach to developing a continental scale ecosystem-modelling system that has relevance both to estimation of greenhouse gas emissions and sustainable management of natural resources. 相似文献
42.
R.P.O. Schulte A.R. Melland O. Fenton M. Herlihy K. Richards P. Jordan 《Environmental Science & Policy》2010,13(6):472-484
Depletion of plant-available soil phosphorus (P) from excessive to agronomically optimum levels is a measure being implemented in Ireland to reduce the risk of diffuse P transfer from land to water. Within the Nitrates and Water Framework Directive regulations the policy tool is designed to help achieve good status by 2015 in water bodies at risk from eutrophication. To guide expectation, this study used soil plot data from eight common soil associations to develop a model of Soil Test P (STP) (Morgan's extract) decline following periods of zero P amendment. This was used to predict the time required to move from excessive (Index 4) to the upper boundary of the optimum (Index 3) soil P concentration range. The relative P balance (P balance : Total soil P) best described an exponential decline (R2 = 63%) of STP according to a backwards step-wise regression of a range of soil parameters. Using annual field P balance scenarios (?30 kg P ha?1, ?15 kg P ha?1, ?7 kg P ha?1), average time to the optimum soil P boundary condition was estimated from a range of realistic Total P and STP starting points. For worst case scenarios of high Total P and STP starting points, average time to the boundary was estimated at 7–15 years depending on the field P balance. However, uncertainty analysis of the regression parameter showed that variation can be from 3 to >20 years. Combined with variation in how soil P source changes translate to resulting P delivery to water bodies, water policy regulators are advised to note this inherent uncertainty from P source to receptor with regard to expectations of Water Framework Directive water quality targets and deadlines. 相似文献
43.
OBJECTIVES: The present study aimed to investigate the illicit drug use patterns of long-distance truck drivers. This population is considered to be a special interest group in terms of drug-driving research and policy due to high rates of use, involvement of drugs in truck accidents, and the link between drug use and work-related fatigue. METHODS: Qualitative interview data were collected from 35 long-haul truck drivers in Southeast Queensland and analyzed through grounded theory techniques. Interviews were conducted at truck stops and loading facilities in both metropolitan and regional cites throughout Queensland. RESULTS: High rates of licit and illicit drug use (particularly amphetamines) were reported by the majority of the sample. However, unlike previous studies that focus on fatigue, this research found overlapping and changing motivations for drug use during individual lifetimes. Becker's model of a drug use "career" was utilized to reveal that some drivers begin illicit drug use before they commence truck driving. As well as fatigue, powerful motives such as peer pressure, wanting to fit the trucking "image," socialization, relaxation, and addiction were also reported as contributing factors to self-reported drug driving. CONCLUSIONS: The results indicate that these additional social factors may need to be considered and incorporated with fatigue factors when developing effective drug prevention or cessation policies for truck drivers. 相似文献
44.
Richards GP 《Food and environmental virology》2012,4(1):6-13
The inability to propagate human norovirus (NoV) or to clearly differentiate infectious from noninfectious virus particles
has led to the use of surrogate viruses, like feline calicivirus (FCV) and murine norovirus-1 (MNV), which are propagatable
in cell culture. The use of surrogates is predicated on the assumption that they generally mimic the viruses they represent;
however, studies are proving this concept invalid. In direct comparisons between FCV and MNV, their susceptibility to temperatures,
environmental and food processing conditions, and disinfectants are dramatically different. Differences have also been noted
between the inactivation of NoV and its surrogates, thus questioning the validity of surrogates. Considerable research funding
is provided globally each year to conduct surrogate studies on NoVs; however, there is little demonstrated benefit derived
from these studies in regard to the development of virus inactivation techniques or food processing strategies. Human challenge
studies are needed to determine which processing techniques are effective in reducing NoVs in foods. A major obstacle to clinical
trials on NoVs is the perception that such trials are too costly and risky, but in reality, there is far more cost and risk
in allowing millions of unsuspecting consumers to contract NoV illness each year, when practical interventions are only a
few volunteer studies away. A number of clinical trials have been conducted, providing important insights into NoV inactivation.
A shift in research priorities from surrogate research to volunteer studies is essential if we are to identify realistic,
practical, and scientifically valid processing approaches to improve food safety. 相似文献
45.
Mechanical-biological treatment of municipal solid waste has become popular throughout the UK and other parts of Europe to enable compliance with the Landfill Directive. Pretreatment will have a major influence on the degradation and settlement characteristics of the waste in landfills owing to the changes in the composition and properties of the wastes. This paper presents and compares the results of long term landfill behaviour of the UK and German MBT wastes pretreated to different standards. The gas generating potential, leachate quality and settlement characteristics are highlighted. The results reveal that it is possible to achieve stabilisation of MBT waste within a year and the biogas yield and leachate strength of German MBT waste was significantly reduced compared with the UK MBT waste. The settlement resulting from mechanical creep is more significant than the biodegradation induced settlement in both cases. 相似文献
46.
Synthetic fibers as an indicator of land application of sludge 总被引:6,自引:0,他引:6
Synthetic fabric fibers have been proposed as indicators of past spreading of wastewater sludge. Synthetic fiber detectability was examined in sludges (dewatered, pelletized, composted, alkaline-stabilized) and in soils from experimental columns and field sites applied with those sludge products. Fibers (isolated by water extraction and examined using polarized light microscopy) were detectable in sludge products and in soil columns over 5 years after application, retaining characteristics observed in the applied sludge. Concentrations mirrored (within a factor of 2) predictions based on soil dilution. Fibers were detectable in field site soils up to 15 years after application, again retaining the characteristics seen in sludge products. Concentrations correlated with residual sludge metal concentration gradients in a well-characterized field site. Fibers found along preferential flow paths and/or in horizons largely below the mixed layer suggest some potential for translocation. Synthetic fibers were shown to be rapid and semi-quantitative indicators of past sludge application. 相似文献
47.
Qureshi S Richards BK Steenhuis TS McBride MB Baveye P Dousset S 《Environmental pollution (Barking, Essex : 1987)》2004,132(1):61-71
Leaching of sludge-borne trace elements has been observed in experimental and field studies. The role of microbial processes in the mobilization of trace elements from wastewater sludge is poorly defined. Our objectives were to determine trace element mobilization from sludge subjected to treatments representing microbial acidification, direct chemical acidification and no acidification, and to determine the readsorption potential of mobilized elements using calcareous sand. Triplicate columns (10-cm diameter) for incubation and leaching of sludge had a top layer of digested dewatered sludge (either untreated, acidified with H2SO4, or limed with CaCO3; all mixed with glass beads to prevent ponding) and a lower glass bead support bed. Glass beads in the sludge layer, support layer or both were replaced by calcareous sand in four treatments used for testing the readsorption potential of mobilized elements. Eight sequential 8-day incubation and leaching cycles were operated, each consisting of 7.6 d of incubation at 28 degrees C followed by 8 h of leaching with synthetic acid rain applied at 0.25 cm/h. Leachates were analyzed for trace elements, nitrate and pH, and sludge layer microbial respiration was measured. The largest trace element, nitrate and S losses occurred in treatments with the greatest pH depression and greatest microbial respiration rates. Cumulative leaching losses from both microbial acidification and direct acidification treatments were > 90% of Zn and 64-80% of Cu and Ni. Preventing acidification with sludge layer lime or sand restricted leaching for all trace elements except Mo. Results suggested that the primary microbial role in the rapid leaching of trace elements was acidification, with results from direct acidification being nearly identical to microbial acidification. Microbial activity in the presence of materials that prevented acidification mobilized far lower concentrations of trace elements, with the exception of Mo. Trace elements mobilized by acidification were readsorbed by calcareous sand when present. 相似文献
48.
Structural investigations on the mucus from six species of coral 总被引:4,自引:0,他引:4
The chemical composition of the mucus from three hard corals (Acropora formosa, Pachyseris speciosa and Fungia fungites) and three soft corals (Sarcophyton sp., Lemnalia sp., and Cespitularia sp.) collected on the Great Barrier Reef (1982–1985) was determined. Significant variation exists in the composition and structure of the six mucus samples, indicating the absence of a common structure for coral mucus. In all cases protein and/or carbohydrate polymers are the major components of the mucus, and lipids are present only in small amounts. The glycose composition varied between species, with fucose (F. fungites and Lemnalia sp.), arabinose (A. formosa), galactose (P. speciosa) and N-acetyl glucosamine (Sarcophyton sp.) being present in high concentrations. With the exception of Sarcophyton sp. and Lemnalia sp., all mucus samples were acidic and contained significant sulphate but no uronic or sialic acids. The amino acid composition of the mucus samples was not unusual, apart from A. formosa, which contained a high percentage of serine and threonine, and F. fungites, which had high levels of glutamic acid present. 相似文献
49.
Metal mobility at an old, heavily loaded sludge application site 总被引:8,自引:0,他引:8
Richards BK Steenhuis TS Peverly JH McBride MB 《Environmental pollution (Barking, Essex : 1987)》1998,99(3):365-377
This study was undertaken to determine the present distribution and mobility of sludge-applied metals at an old land application site. Trace metals concentrations were determined for soils (using 4 M HNO3 extracts), soil leachates (collected with passive wick lysimeters over a 2.5-year period), and plant tissue from a field site which received a heavy loading of wastewater sludge in 1978 and an adjacent control plot. Blue dye was used to indicate preferential percolate flowpaths in the sludge plot soil for sampling and comparison with bulk soil metals concentrations. After nearly 20 years, metals in the sludge plot leachate were found at significantly greater concentrations than in the control plot, exceeding drinking water standards for Cd, Ni, Zn, and B. Annual metals fluxes were only a fraction of the current soil metal contents, and do not account for the apparent substantial past metals losses determined in a related study. Elevated Cd, Cu, and Ni levels were found in grass growing on the sludge plot. Despite heavy loadings, fine soil texture (silty clay loam) and evidence of past and ongoing metals leaching, examination of the bulk subsoil indicated no statistically significant increases in metals concentrations (even in a calcareous subsoil horizon with elevated pH) when comparing pooled sludge plot soil profiles with controls. Sampling of dyed preferential flow paths in the sludge plot detected only slight increases in several metals. Preferential flow and metal complexation with soluble organics apparently allow leaching without easily detectable readsorption in the subsoil. The lack of significant metal deposition in subsoil may not be reliable evidence for immobility of sludge-applied metals. 相似文献
50.
北京市西北城区取暖期环境大气中PM10的物理化学特征 总被引:5,自引:0,他引:5
根据监测资料探讨了北京市西北城区取暖期PM10 的逐日变化规律和日变化规律 .分别使用X射线衍射仪(XRD)和扫描电镜 (SEM)研究PM10 中的矿物成分及其微观形貌特征 .结果表明夜间PM10 浓度普遍高于白天 .XRD分析显示颗粒物粒度越细 ,其中所含的矿物种类越少 .SEM研究得出 ,单个PM10 颗粒类型可初步分为有链状集合体、簇状集合体、圆球状、片状和不规则形状等 5类 .从数量上看 ,PM10 主要来自燃煤和汽车尾气 相似文献