Study of the biouptake of labeled single-walled carbon nanotubes using fluorescence-based method

Single-wall carbon nanotubes (CNT) are one of the most attractive engineered nanomaterials due to their unique electrical, mechanical and thermal properties, and potential use in a variety of commercial products. Due to their small size, CNT could become easily airborne and reach the various environmental compartments and eventually the food chain and humans. However, the environmental fate processes and health impacts of CNT are not clear. This study investigated a method for the quantitative measurement of carbon nanotube (CNT) in natural media such soil and benthic organism tissues. Fluorescence dye Nile blue was used for noncovalent labeling of CNT to enable their fluorescence detection. Labeled nanotubes were successfully detected in soil samples as well as in worm tissue. We were also able to detect the presence of labeled carbon nanotubes in worms exposed for 1 week to CNT-laden soil, which indicates CNT may transfer through environmental food web. The method allows for laboratory measurements of CNT mass transfer and partitioning into various environmental systems.     

Logistic regression and fuzzy logic as a classification method for feral fish sampling sites

This study presents a classification method combining logistic regression and fuzzy logic in the determination of sampling sites for feral fish, Nile Tilapia (Tilapia rendalli). This method statistically analyzes the variable domains involved in the problem, by using a logistic regression model. This in turn generates the knowledge necessary to construct the rule base and fuzzy clusters of the fuzzy inference system (FIS) variables. The proposed hybrid method was validated using three fish stress indices; the Fulton Condition Factor (FCF) and the gonadossomatic and hepatossomatic indices (GSI and HSI, respectively), from fish sampled at 3 different locations in the Rio de Janeiro State. A multinomial logistic regression allowed for the FIS construction of the proposed method and both statistical approaches, when combined, complemented each other satisfactorily, allowing for the construction of an efficient classification method regarding feral fish sampling sites that, in turn, has great value regarding fish captures and fishery resource management.     

Potential nitrogen constraints on soil carbon sequestration under low and elevated atmospheric CO2

The interaction between nitrogen cycling and carbon sequestration is critical in predicting the consequences of anthropogenic increases in atmospheric CO2 (hereafter, Ca). The progressive N limitation (PNL) theory predicts that carbon sequestration in plants and soils with rising Ca may be constrained by the availability of nitrogen in many ecosystems. Here we report on the interaction between C and N dynamics during a four-year field experiment in which an intact C3/C4 grassland was exposed to a gradient in Ca from 200 to 560 micromol/mol. There were strong species effects on decomposition dynamics, with C loss positively correlated and N mineralization negatively correlated with Ca for litter of the C3 forb Solanum dimidiatum, whereas decomposition of litter from the C4 grass Bothriochloa ischaemum was unresponsive to Ca. Both soil microbial biomass and soil respiration rates exhibited a nonlinear response to Ca, reaching a maximum at approximately 440 micromol/mol Ca. We found a general movement of N out of soil organic matter and into aboveground plant biomass with increased Ca. Within soils we found evidence of C loss from recalcitrant soil C fractions with narrow C:N ratios to more labile soil fractions with broader C:N ratios, potentially due to decreases in N availability. The observed reallocation of N from soil to plants over the last three years of the experiment supports the PNL theory that reductions in N availability with rising Ca could initially be overcome by a transfer of N from low C:N ratio fractions to those with higher C:N ratios. Although the transfer of N allowed plant production to increase with increasing Ca, there was no net soil C sequestration at elevated Ca, presumably because relatively stable C is being decomposed to meet microbial and plant N requirements. Ultimately, if the C gained by increased plant production is rapidly lost through decomposition, the shift in N from older soil organic matter to rapidly decomposing plant tissue may limit net C sequestration with increased plant production.     

Research on low emission MSW gasification and melting system

In order to eliminate secondary pollution caused by municipal solid waste (MSW) incineration, a MSW gasification and melting process is proposed. The process is expected to reduce the emission of pollutants, especially heavy-metals and dioxins. In this paper, the combustible components of MSW and simulated MSW were gasified in a lab-scale fluidized bed at 400°C–700°C when the excess air ratio (ER) was between 0.2 and 0.8. The experimental results indicated that the MSW could be gasified effectively in a fluidized bed at approximately 600°C–700°C when excess air ratio was 0.2–0.4. The melting characteristics of two typical fly ash samples from MSW incinerators were investigated. The results indicated that fly ash of pure MSW incineration could be melted at approximately 1,300°C and that of MSW and coal co-combustion could be melted at approximately 1,400°C. When temperature was over 1,100°C, more than 99.9% of the dioxins could be decomposed and most of the heavy-metals could be solidified in the slag. Based on the above experiments, two feasible MSW gasification and melting processes were proposed for low calorific value MSW: (1) sieved MSW gasification and melting system, which was based on an idea of multi-recycle; (2) gasification and melting scheme of MSW adding coal as assistant fuel.     

Estimation of the density of a clustered point pattern using a distance method

Distance-based methods use point-to-point distances or random-location-to-point distances in a cloud of points to estimate characteristics of the point pattern. One such characteristics is the density of points. The difficulty with distance-based density estimators is that their distribution depends on the spatial pattern of points. In particular, the distribution of distances is untractable for usual clustered patterns, that are often observed in natural systems. Here, we propose a density estimator for clustered patterns, based on the random-location-to-pth-point distance X _p . An approximate expression for the distribution function, F _p , of X _p was obtained by identifying the first two moments of the count of individuals in disks for a given point process with the first two moments of a negative binomial distribution. The approximate expression of F _p was then used to derive a maximum-likelihood estimator of the intensity of the point process. The quality of the approximation of F _p was assessed for homogeneous Poisson processes (for which the expression of F _p is exact) and for Matérn processes. The intensity estimator based on Matérn processes was then used to estimate tree density in a tree savanna in Mali, and it compared favorably with six robust estimators found in the literature.     

刍议医疗设备管理的方法与实践应用

针对现代医疗仪器设备管理的新形势,从医疗器械的购置、验收、使用、维修保养、报废及计量检测六个方面阐述了完善医疗设备管理的方法与实践,以达到医疗设备科学化管理的目的.     

基于环境管理的河流健康评价体系的研究进展

随着河流环境的逐渐退化,其自然功能和社会功能都受到了严重的威胁,河流健康评价的研究也逐渐成为河流生态研究的热点之一。河流健康评价体系能够明确河流的健康状态,为环境管理和生态修复提高理论基础,同时提高环境管理和生态修复的针对性和有效性。然而,环境管理也是河流健康评价体系的制定基准和目标。文章从国内外研究对河流健康的内涵和河流健康评价的指标体系两个方面进行了综述和分析。目前,国际上对于河流健康的内涵逐渐由仅关注自然功能,向与社会功能等方面结合的方向扩充。河流健康评价指标体系主要有两种：一是指示物种评价法,二是指标综合体系评价法。通过比较这两种方法的发展和优劣,我国更适宜于指标综合体系评价方法,有助于环境管理措施的制定。最后,通过结合和借鉴国内外已有的研究成果,构建了针对我国国情的、基于环境管理的河流健康评价理论框架。     

大气CO2升高对土壤碳循环影响的研究进展

土壤有机碳是陆地碳库的重要组成部分,其积累和分解的变化直接影响全球的碳平衡。据估计,全球土壤（表层1m）有机碳积累总量相当于大气中碳总量的2～3倍。土壤是温室气体的源或汇,土壤碳库的变化将影响大气C02的浓度,因此,土壤碳库对人类活动的响应也是全球碳循环和全球变化研究的热点。在全球变化的大背景下,大气CO2升高导致植被生态系统碳平衡的改变进而对土壤碳循环产生影响。总结了陆地生态系统碳循环对大气C02浓度升高响应的主要生物学机制及过程,简述了大气C02浓度升高对影响土壤碳输入和输出的各因素的研究进展,并指出未来研究的主要方向。在大气C02浓度升高条件下,陆地生态系统碳循环的变化主要反映在以下几个方面：1）不同类型植物群落的净初级生产力（NPP）显著增加,但湿地植物的净初级生产力也有可能降低;2）光合产物向根系分配的数量增加,地上／地下生物量降低,根系形态发生变化,根系周转速率和根系分泌等过程的碳流量提高;3）植物含氮量降低,C／N提高,次生代谢产物增加,微生物生长受到抑制,植物残体分解速率降低;4）土壤呼吸速率显著增加,提高幅度受植物类型与土壤状况的影响;5）进入土壤的植物残体及分泌物的数量和性质影响土壤酶的活性,脱氢酶和转化酶活性增加,酚氧化酶和纤维素酶受植物类型与环境条件的影响;6）土壤中真菌的数量的增加幅度要高于细菌;7）CH4释放量增加,在植物的生长期表现更为明显。由于陆地生态系统碳循环的复杂性,研究结果仍有很大的不确定性。大气C02浓度升高与全球变化的其它表现间的交互作用将是今后研究的重点,同时由于土壤碳循环是一个由微生物介导的生物地球化学循环过程,因此,加强陆地生态系统碳循环的微生物机制研究也将为全面理解碳循环的过程提供更加准确的研究理论基础。     

土地利用对湿地土壤活性有机碳的影响研究进展

湿地生态系统土壤碳库的周转及碳源/汇过程对全球气候变化起着极其重要的作用,而土壤碳库中的活性碳组分对环境因子变化响应最为敏感,湿地土壤活性有机碳在湿地土壤碳、氮、磷等养分元素的生物地球化学循环方面起着十分重要的作用。不同的土地利用方式对湿地土壤活性有机碳组分的特征分布影响显著,综述了土壤活性有机碳内涵、组分及土地利用方式变化对湿地土壤活性有机碳多种组分的影响研究进展,展望不同土地利用方式下湿地土壤活性碳库的未来研究方向,并提出今后应加强不同土地利用方式下湿地生态系统土壤活性碳库与土壤微生物及土壤酶活性的关系研究,以期为评估湿地生态系统碳源/汇功能提供理论基础。     

论土壤肥力评价指标和方法

阐述了土壤肥力的概念,分析了土壤肥力评价的指标选取和方法选择,提出了科学合理的综合性评价指标体系和评价方法。     

Modelling soil carbon development in Swedish coniferous forest soils—An uncertainty analysis of parameters and model estimates using the GLUE method

Boreal forest soils such as those in Sweden contain a large active carbon stock. Hence, a relatively small change in this stock can have a major impact on the Swedish national CO₂ balance. Understanding of the uncertainties in the estimations of soil carbon pools is critical for accurately assessing changes in carbon stocks in the national reports to UNFCCC and the Kyoto Protocol. Our objective was to analyse the parameter uncertainties of simulated estimates of the soil organic carbon (SOC) development between 1994 and 2002 in Swedish coniferous forests with the Q model. Both the sensitivity of model parameters and the uncertainties in simulations were assessed. Data of forests with Norway spruce, Scots pine and Lodgepole pine, from the Swedish Forest Soil Inventory (SFSI) were used. Data of 12 Swedish counties were used to calibrate parameter settings; and data from another 11 counties to validate. The “limits of acceptability” within GLUE were set at the 95% confidence interval for the annual, mean measured SOC at county scale. The calibration procedure reduced the parameter uncertainties and reshaped the distributions of the parameters county-specific. The average measured and simulated SOC amounts varied from 60 t C ha⁻¹ in northern to 140 t C ha⁻¹ in the southern Sweden. The calibrated model simulated the soil carbon pool within the limits of acceptability for all calibration counties except for one county during one year. The efficiency of the calibrated model varied strongly; for five out of 12 counties the model estimates agreed well with measurements, for two counties agreement was moderate and for five counties the agreement was poor. The lack of agreement can be explained with the high inter-annual variability of the down-scaled measured SOC estimates and changes in forest areas over time. We conclude that, although we succeed in reducing the uncertainty in the model estimates, calibrating of a regional scale process-oriented model using a national scale dataset is a sensitive balance between introducing and reducing uncertainties. Parameter distributions showed to be scale sensitive and county specific. Further analysis of uncertainties in the methods used for reporting SOC changes to the UNFCCC and Kyoto protocol is recommended.     

Higher hydrogen production by photocatalytic water splitting using a hollow tubular graphitic carbon nitride-zinc telluride composite

Environmental Chemistry Letters - Energy demand and pollution due to urbanization and industrialization are calling for clean energies such as dihydrogen (H2) obtained by water splitting. For that,...     

一种基于三维指标因子的流域多年径流丰枯k-means聚类法

径流丰枯聚类研究的传统方法多建立在年径流量的单一指标之上,容易导致分析的片面化。针对这个问题,提出了衡量流域多年径流丰枯状态的三维指标因子及权重,将其耦合到k-means聚类法的相似度计算与收敛分析中,在此基础上对对多年径流进行丰枯聚类,构建了一种基于三维指标因子的流域多年径流丰枯k-means聚类法。以该方法对广东省鉴江流域下游化州站1956—2006年的径流系列进行聚类分析,并与基于年径流量单一指标的k-means聚类方法进行对比,结果表明该方法是较全面且符合实际的。     

Uncertainty analysis of climate change mitigation options in the forestry sector using a generic carbon budget model

Industrialized countries agreed on a reduction of greenhouse gas emissions under the Kyoto Protocol. Many countries elected forest management activities and the resulting net balance of carbon emissions and removals of non-CO₂ greenhouse gases by forest management in their climate change mitigation measures. In this paper a generic dynamic forestry model (FORMICA) is presented. It has an empirical basis. Several modules trace C pools relevant for the Kyoto Protocol and beyond: biomass, litter, deadwood and soil, and harvested wood products. The model also accounts for the substitution of fossil fuels by wood products and bioenergy.     

Modeling seasonal course of carbon fluxes and evapotranspiration in response to low temperature and moisture in a boreal Scots pine ecosystem

Environmental conditions act above and below ground, and regulate carbon fluxes and evapotranspiration. The productivity of boreal forest ecosystems is strongly governed by low temperature and moisture conditions, but the understanding of various feedbacks between vegetation and environmental conditions is still unclear. In order to quantify the seasonal responses of vegetation to environmental factors, the seasonality of carbon and heat fluxes and the corresponding responses for temperature and moisture in air and soil were simulated by merging a process-based model (CoupModel) with detailed measurements representing various components of a forest ecosystem in Hyytiälä, southern Finland. The uncertainties in parameters, model assumptions, and measurements were identified by generalized likelihood uncertainty estimation (GLUE). Seasonal and diurnal courses of sensible and latent heat fluxes and net ecosystem exchange (NEE) of CO₂ were successfully simulated for two contrasting years. Moreover, systematic increases in efficiency of photosynthesis, water uptake, and decomposition occurred from spring to summer, demonstrating the strong coupling between processes. Evapotranspiration and NEE flux both showed a strong response to soil temperature conditions via different direct and indirect ecosystem mechanisms. The rate of photosynthesis was strongly correlated with the corresponding water uptake response and the light use efficiency. With the present data and model assumptions, it was not possible to precisely distinguish the various regulating ecosystem mechanisms. Our approach proved robust for modeling the seasonal course of carbon fluxes and evapotranspiration by combining different independent measurements. It will be highly interesting to continue using long-term series data and to make additional tests of optional stomatal conductance models in order to improve our understanding of the boreal forest ecosystem in response to climate variability and environmental conditions.     

Alkaline phosphatase activity in subtropical Central North Pacific waters using a sensitive fluorometric method

This paper describes a fluorometric method for assaying low levels of the enzyme alkaline phosphatase in seawater. The assay is based on the hydrolysis of the monophosphate ester bond of 3-0-methylfluorescein phosphate. This enzyme is synthesized by many microorganisms when phosphate becomes limiting. Alkaline phosphatase activity was detected in phytoplankton from the nutrient-impoverished surface waters of the subtropical Central North Pacific Ocean. The presence of naturally occurring phosphatase suggests that phosphorus may be limiting to phytoplankton growth in these waters. The phytoplankton in water samples lacking enzyme activity at the time of collection produced phosphatase within 1 to 2 days of incubation at in situ temperatures.     

Solution of fully-coupled shallow water equations and contaminant transport using a primitive-variable Riemann method

A Riemann-solver scheme, using primitive variables rather than conserved variables, is configured and tuned for the solution of the fully-coupled two-dimensional shallow water and contaminant transport equations. This scheme is based on the unstructured finite volume discretization using primitive-variable Roe-flux approximation with an entropy fix. The primitive-variable flux associated with the exact source-term balancing is well-behaved and well-balanced for both still-water and dry regions with arbitrary bed topography. Second-order accuracy is used in space and time. The present study uses a nonlinear implicit scheme based on Newton-iterative algorithm for the time integration. In order to show the accuracy of the scheme, numerical results are verified by different test cases for contaminant advection and diffusion. A scenario of contaminant transport in a complex geometry with wet and dry elements is also simulated to demonstrate that the present work can be implemented on practical applications involving flooding and contaminant transport.     

Temperature effects on the metabolism of larvae of the Antarctic starfish Odontaster validus, using a novel micro-respirometry method

Oxygen consumption of individual larvae of the Antarctic sea-star Odontaster validus was measured during the 50-day period following fertilisation. Values ranged from 0.76 pmol O₂ h^-1 for one specimen at the coeloblastula stage to 77.6 pmol O₂ h^-1 for one bipinnaria larva. At 0°C the mean oxygen consumption rate of an individual larva increased from 10.9 pmol O₂ h^-1 (standard error of the mean, SEM, 0.13) for a gastrula larva, 13 days post-fertilisation, to 25.4 pmol O₂ h^-1 (SEM 3.5) at the bipinnaria stage (50 days post-fertilisation). Gastrulae reared at -0.5°C did not have significantly different oxygen consumption rates between days 13 and 45 post-fertilisation (mean=11.4 pmol O₂ h^-1). Individual metabolic rates were highly variable, covering more than a 40-fold range. At 2°C gastrula oxygen consumption was on average 45% higher (17.35 pmol O₂ h^-1), giving a Q₁₀ temperature effect of 4.4. For bipinnaria, mean oxygen consumption in 2°C larvae (31.4 pmol O₂ h^-1) was not significantly different from that in larvae at -0.5°C, suggesting bipinnaria metabolism may be less sensitive to temperature change than earlier stages. At 2°C the bipinnaria stage was reached at 30-35 days compared with 45-50 days at 0°C, giving a Q₁₀ of 4.5 for temperature effects on development. The method here used a new, highly sensitive micro-respirometry method that is inexpensive and straightforward in design. Individual larvae of O. validus were held in 35- to 50-µl respirometers. These larvae have very low metabolic rates, and published work on such organisms have utilised at least 25 individuals per chamber. The oxygen content of the respirometers was measured using a 25-µl sample injected into a couloximeter. Oxygen consumption rates down to -1 pmol h^-1 can be detected. Under optimum conditions oxygen consumption of a single larva of -4 pmol O₂ h^-1 was measured with an accuracy of ᆨ%. Values of ~15 pmol h^-1 could routinely be measured with this accuracy. This method would allow oxygen consumption to be evaluated in individual field-caught larvae of most marine ectotherms.     

Treatment of methylene blue-containing wastewater using microorganisms supported on granular activated carbon under packed column operation

We studied the feasibility of using biological granular activated carbon-packed column in treating methylene blue-containing wastewater. The granular activated carbon with immobilized microbes was packed into a column and fed with 3 liter methylene blue-containing wastewater daily. With initial 1350 mg/l of methylene blue and 1550 mg/l of chemical oxygen demand, it was observed that the colour and chemical oxygen demand removal efficiencies were 99 and 78%, respectively. The high treatment performance of the system could be due to the simultaneous adsorption and biodegradation processes and advantages of immobilized microbes compare to suspended cell system.