城市空气质量数值预报的不确定性与可预报性

主要综述了数据误差、随机误差和模式物理误差所造成的城市空气质量数值预报的不确定性,简要介绍分析预报不确定性的统计方法。并对由内在随机性和外在误差引起的可预报性问题进行了分析讨论     

合格评定资料介绍

本文介绍关于合格评定的资料。这些资料包括合格评定的组织机构、法律法规及技术法规,以供对实验室认可和质量认证感兴趣的机构参考。     

Consumption,growth and survival of the endemic stream shredder Limnephilus atlanticus (Trichoptera,Limnephilidae) fed with distinct leaf species

Oceanic freshwater communities tend to be species poor but rich in endemism due to their physical isolation. The ecology of endemic freshwater species is, however, poorly known. This study assessed allometric relationships, feeding preferences, growth and survival of larvae of the endemic stream insect Limnephilus atlanticus (Trichoptera, Limnephilidae) exposed to four leaf species differing in their physical and chemical characteristics (Ilex perado, Morella faya, Alnus glutinosa and Clethra arborea), in laboratory trials. All regression models used to estimate L. atlanticus dry mass from body and case dimensions and wet mass were significant, but wet mass and body length were the best predictors. Limnephilus atlanticus consumed all the four leaf species offered, but when given a choice, shredders significantly preferred A. glutinosa over the other three leaf species. Relative larval growth rate was significantly higher when L. atlanticus fed on A. glutinosa and I. perado leaves in comparison with the other leaf species. Survival of 95% was found when individuals fed on A. glutinosa leaves while it decreased to 75% when they fed on the other leaf species. Our results suggest that L. atlanticus can be an active shredder and that it exhibits the same basic patterns of food exploitation as its continental counterparts. The lack of an effect of shredders on litter decomposition in Azorean streams revealed by previous studies may thus be due to low densities or to a preference for food resources other than the low quality native litter species.     

D) UNITED Nations

Synopsis

In areas of accentuated relief, some of the basic assumptions made in the use of standard methods of assessing areal mean rainfall are often untenable. It is shown in this paper, that, not only does topography affect the actual rainfall distribution, but that the areal variability, measured as the correlation between any two points, is also dependent on the relief. Two methods are used to show this. Once method compares the areal variability of a flat area to one of accentuated relief, while the second method relates areal variability to topographic factors using a multiple regression technique.

The conclusions reached are then used for three purposed. The first is to develop a method of ascribing objectively areas or points to a particular raingauge, taking into account the nature of the terrain. The second is to establish a procedure for estimating the rainfall at ungauged points, by taking into account the rainfall at a selected nearby rainguage and the topographic situation of the points, and the third purpose is to provide means of establishing a correction factor to be applied to a raingauge reading in order that the reading may more accurately represent the area ascribed to it.     

Predicting Diel,Diurnal and Nocturnal Dynamics of Dissolved Oxygen and Chlorophyll‐a Using Regression Models and Neural Networks

Human‐induced and natural interruptions with continuous streams of observational data necessitate the development of gap‐filling and prediction strategies towards better understanding, monitoring and management of aquatic systems. This study quantified the efficacy of multiple non‐linear regression (MNLR) versus artificial neural network (ANN) models as well as the temporal partitioning of diurnal versus nocturnal data for the predictions of chlorophyll‐a (chl‐a) and dissolved oxygen (DO) dynamics. The temporal partitioning increased the predictive performances of the best MNLR models of diurnal DO by 45% and nocturnal DO by 4%, relative to the best diel MNLR model of diel DO ($r_{{\rm adj}}^{2} = 68.8\%$ ). The ANN‐based predictions had a higher predictive power than the MNLR‐based predictions for both chl‐a and DO except for diurnal DO dynamics. The best ANNs based on independent validations were multilayer perceptron (MLP) for diel chl‐a, generalized feedforward (GFF) for diurnal and nocturnal chl‐a, MLP for diel DO, GFF for diurnal DO, and MLP for nocturnal DO.     

Conservation of the freshwater pearl mussel (Margaritifera margaritifera) in the river Rede,UK: Identification of instream indicators for catchment-scale issues

The freshwater pearl mussel (Margaritifera margaritifera) is declining throughout its entire range. On the river Rede, North-East England, the population has been equally declining and shows no apparent recruitment. The study presented here aimed at characterizing water quality and habitat conditions for pearl mussels to identify possible indicators of pressures on the population and inform a restoration and conservation strategy. Water quality monitoring revealed levels of turbidity and suspended sediments to be above the limit set for functional pearl mussel rivers. Substrate sampling revealed silt was present at all sites. A loss of redox potential between the water column and the substrate occurred at all sites, indicating non suitable conditions for juvenile pearl mussels. These investigations suggest that fine sediment input in the river could be one of the factors preventing the development and survival of juvenile mussels while adults face water quality largely affected by high turbidity and high phosphate load. Restoration strategy for the Rede pearl mussel population should focus mainly on limiting sediment and nutrient input in the river throughout the catchment in order to improve habitat for juvenile pearl mussels. This work highlights the need for a catchment-based approach in order to succeed in the conservation of a fragile species.     

Spatial and Temporal Distribution of Dust‐Bound Trace Metal Elements around Kuhdasht Watershed Area in Iran

Dust, as a source of trace metal elements, affects the health of society. The spatial and temporal concentrations of dust‐bound trace metals (Cd, Pb, Ni, Zn, Cu, and Mn) in Kuhdasht watershed (456 km²), Lorestan Province, Iran, is investigated. Dust is collected using glass traps placed in ten research stations in the region. The spatial and temporal distribution of dust trace metals are plotted using ARC‐GIS. The highest and the lowest concentrations of Zn (9751150 mg kg^?1), Pb (46.352.9 mg kg^?1), and Cd (2.443.30 mg kg^?1) are obtained in winter, of Ni (98110 mg kg^?1) and Cu in autumn (16.053.5 mg kg^?1), and of Mn in summer (385505 mg kg^?1). The spatial concentrations of dust‐bound trace metals indicate all, except Cu, show a decreasing trend from the mountains toward the plains, similar to that of soil and of dust, except for Zn, which shows higher concentrations in dust than in soil. The potential sources of dust‐bound trace metals and their rate of contamination are also investigated using the enrichment and contamination factors. The major sources of Cd and Zn in the dust of watershed are due to anthropogenic activities or from activities outside the borders.     

Water quality and presence of pesticides in a tropical coastal wetland in southern Mexico

The water quality of the Pozuelos-Murillo lagoon system in southern Mexico was evaluated during three periods between March and October 2002, with particular emphasis on the detection of organochlorine and organophosphorous pesticide residues in water and sediments. Physicochemical and microbiological parameters of water were also measured and integrated in a water quality index (WQI). Multivariate analysis was used to regionalise the lagoon system as a function of the behaviour of all measured parameters. Solid phase micro-extraction followed by gas chromatography (SPME-GC) was used for pesticide analysis. The concentration of phosphorous was found to be higher than that of nitrogenous compounds. This, besides a deficiency in dissolved oxygen and a high organic matter concentration (as COD), reflects eutrophication processes in some areas of the system. Measured levels of faecal coliforms and oils and greases were above the limits established by Mexican law and comparable to the concentrations reported for other highly polluted systems in Mexico. Residues of DDD (2.0 microg L(-1)) in water and DDE (247 ng g(-1)) and endosulfan I (814 ng g(-1)) sediments were detected by SPME-GC. The spatial distribution of these contaminants implies major potential risks because the most polluted sites were found to be those with the highest fishing activity. Although in general the WQI is on acceptable levels (65-80%), some contamination problems are evident.     

改性粘土辅助沉水植物修复技术维持清水稳态的原位研究

在富营养湖泊治理实践中,修复沉水植被被认为是改善水质的长效措施,而壳聚糖改性粘土是短期快速改善水质的有效手段.本研究利用改性粘土辅助沉水植被修复,旨在探索改善水质的长效方案.2011年5-11月在太湖梅梁湾开展了四组不同处理(对照、水草、水草+粘土、粘土)围隔实验,在水草(盖度13.0%)和水草+粘土(盖度52.3%)围隔中不同程度重建了苦草群落.实验期内每3 d一次的水质监测表明,粘土处理可显著改善水质,水体总氮(TN)、总磷(TP)、正磷酸盐(PO34--P)和叶绿素a(Chl.a)含量分别比对照下降了20.7%、74.6%、31.0%和80.4%,透明度(SD)升高了90.4%;粘土辅助植被修复改善水质效果最长稳,水体TN、TP、PO34--P和Chl.a含量分别比对照下降了36.2%、64.0%、28.6%和71.1%,SD升高了76.4%;低盖度苦草群落单独处理对水质改善效果不显著.在三种处理中,粘土辅助植被修复改善底质效果最好,使间隙水的TN、TP、PO34--P、NH4+-N分别比实验前下降了15.6%、61.7%、55.8%和82.8%.本研究表明改性粘土辅助沉水植被修复可作为重富营养水体中水质改善的整合技术,但其长期生态效应仍需谨慎评估.     

基于LabVIEW的预应力孔道压浆质量检测仪的软件设计

本文提出了一种预应力孔道压浆质量检测仪的硬件方案,在此基础上介绍了基于LabVIEW的仪器软件设计,重点讨论了软件实现的关键技术,实现了参数设置,多通道超声信号采集,文件管理等功能.软件界面友好,操作简单,适应仪器的野外工作,且升级维护方便.