A proposal of an indicator for quantifying model robustness based on the relationship between variability of errors and of explored conditions

The evaluation of biophysical models is usually carried out by estimating the agreement between measured and simulated data and, more rarely, by using indices for other aspects, like model complexity and overparameterization. In spite of the importance of model robustness, especially for large area applications, no proposals for its quantification are available. In this paper, we would like to open a discussion on this issue, proposing a first approach for a quantification of robustness based on the variability of model error to variability of explored conditions ratio. We used modelling efficiency (EF) for quantifying error in model predictions and a normalized agrometeorological index (SAM) based on cumulated rainfall and reference evapotranspiration to characterize the conditions of application. Population standard deviations of EF and SAM were used to quantify their variability. The indicator was tested for models estimating meteorological variables and crop state variables. The values provided by the robustness indicator (I_R) were discussed according to the models’ features and to the typology and number of processes simulated. I_R increased with the number of processes simulated and, within the same typology of model, with the degree of overparameterization. No correlation were found between I_R and two of the most used indices of model error (RRMSE, EF). This supports its inclusion in integrated systems for model evaluation.     

Techno-economic analysis for the electrocoagulation of fluoride-contaminated drinking water

Electrocoagulation (EC) technique was adopted for the treatment of fluoride-containing drinking water in a 3?L capacity batch reactor. Experimental investigation was carried out to observe the effect of different operating parameters, such as initial fluoride concentration, current density, inter-electrode distance, on the removal of fluoride from the fluoride-rich drinking water. Aluminum flat sheet was used as the electrode material. It was observed that with an increase in current density, percentage removal of fluoride increased. It was seen that at electrode distance of 0.005?m, removal of fluoride attained its maximum compared to the other performances obtained at different inter-electrode distances. Life time of the aluminum electrodes was estimated from the electrode corrosion observed during the experiment. Total operating cost was estimated as a combination of energy cost and electrode cost. The total operating cost was evaluated as 0.38?US$?m^?3 to remove fluoride from the solution with an initial fluoride concentration 10?mg?L^?1. Characterizations of the electrochemically generated by-products were carried out by powder X-ray diffraction, Fourier transform infra-red Raman spectroscopy, scanning electron microscopy image and corresponding elemental analysis.     

DOW CORNING 1-2577 Conformal Coating as an efficient diffusion material for cathode in the microbial fuel cell

In this study, DOW CORNING 1-2577 Conformal Coating was proposed for the cathode diffusion layer of the microbial fuel cell (MFC). In MFCs, stainless steel mesh cathodes using DOW CORNING 1-2577 Conformal Coating/carbon as the diffusion layer and two poly (dimethylsiloxane) (PDMS)/carbon diffusion layers and carbon cloth cathode with four poly (tetrafluoroethylene) (PTFE) diffusion layers were constructed for comparison. Under the same operational condition, the MFCs with the DOW CORNING 1-2577 Conformal Coating/carbon diffusion layer produced the maximum power density of 1585±52 mW·m^-2, compared with those using poly (tetrafluoroethylene) (PTFE) diffusion layers (1421±45 mW·m^-2) and poly (dimethylsiloxane) (PDMS)/carbon diffusion layers (1353±49 mW·m^-2). The DOW CORNING 1-2577 Conformal Coating could be an alternative for the diffusion layer construction in the MFC due to its remarkable performance and much simple construction procedure.     

吕梁山南段森林碳密度及其空间分布格局研究

基于2000年和2005年两期森林资源清查资料,利用双向指示种分析（ two-way indicator species analysis, TWINSPAN）方法,对森林植被进行群系划分;采用生物量换算因子法,对森林样地碳密度进行估算,对碳密度及其动态变化特征进行研究;基于地统计学原理对森林碳密度的空间分布格局进行分析,并对其影响因子进行探讨。结果表明,（1）吕梁山南段森林植被可分为9个群系,即臭椿群系、柳树群系、辽东栎-油松混交群系、辽东栎群系、辽东栎-枫树混交群系、辽东栎-白桦-山杨混交群系、白皮松-辽东栎混交群系、白皮松-侧柏混交群系和槐树群系。2000年各群系的碳密度值介于23.53 Mg·hm^-2和75.65 Mg·hm^-2之间,平均值为54.90 Mg·hm^-2;2005年的碳密度值介于24.16 Mg·hm^-2和78.91 Mg·hm^-2之间,平均值为57.20 Mg·hm^-2,5年间9个森林群系的碳密度增加了2.30 Mg·hm^-2。（2）森林碳密度呈现出自南向北、自西向东增加的趋势;球状模型能很好地反映森林植被碳密度的空间结构特征;碳密度分布主要受结构性因子影响,空间依赖性较强,在小尺度上没有明显规律,而在中尺度上有群团状分布的特点。（3）随着海拔的升高,森林碳密度先增后降,1600～1800 m最大;坡上部森林碳密度最高,其次为坡下部,山脊部最低;阴坡半阴坡森林碳密度一般高于阳坡和半阳坡,无坡向处最低;斜坡和平坡碳密度值明显高于其他坡地,急坡地最小。     

Organochlorine pesticides (HCHs and DDTs) in soils along the north coastal areas of the Bohai Sea,China

A systematic survey of organochlorine pesticides (OCPs) including hexachlorocyclohexane isomers (α-HCH, β-HCH, γ-HCH, δ-HCH and ΣHCH) and dichlorodiphenyltrichloroethane metabolites (p,p′-DDT, p,p′-DDE, o,p′-DDT, p,p′-DDD and ∑DDT) in soils along the north coastal areas of the Bohai Sea, China, has been lacking. In this study, 31 representative surface soil samples were collected along the north coastal and riverine areas of the Bohai Sea to characterise the potential for adverse effects of ∑HCH, ∑DDT and their individual isomers and transformation products. Concentrations of ΣHCH and ΣDDT in soils ranged from less than the limit of detection (1 ng · g^?1 dw (mean: 3.5 ng · g^?1 dw) and2 ng · g^?1 dw (mean: 1.7 × 10¹ ng · g^?1 dw), respectively. Compared with studies of OCPs in soils from other locations, concentrations of HCHs and DDTs observed in this study were moderate. Concentrations of OCPs observed in soils were generally less than proposed reference values. HCH residues were a mixture of historical technical HCH and current lindane sources. The pattern of DDTs was consistent with historical releases of technical DDTs. Selected soil physicochemical properties did not explain the sorption and/or partitioning of HCHs or DDTs.     

城市固体废弃物持水率的室内实验研究

垃圾土持水率是估算填埋场淋沥液高度和分析填埋体稳定性的重要参数。通过对高压固结仪的改造,研制垃圾土持水率的室内实验仪器,并在该仪器上对取自我国南方某填埋场3个不同深度的大直径垃圾土试样进行各级荷载下的持水率实验。研究结果表明,随填埋深度增大,垃圾年份增加,垃圾土可降解度降低,腐殖质含量增大,垃圾土的持水率减小;随上覆压力增大,干重和湿重持水率减小,当上覆压力增大到一定程度,减小趋势变缓;随上覆压力的增大,体积持水率一般呈减小的趋势,但对于疏松垃圾土,在较小的压力下,体积持水率有增大的趋势,当压力增大到一定程度,则随压力的增大而减小;随干密度的增大,垃圾土干重和湿重持水率均减小。提出的垃圾土持水率的室内实验方法和研制的仪器合理可行。     

温湿度对PM2.5质量浓度监测的影响

探讨了在不同环境条件和污染状况下,带膜动态测量的微振荡天平法的自动监测方法能否准确监测空气中的PM_(2.5)质量浓度。通过自动方法与手工重量法的比对,针对2015年8月—2016年7月的监测结果进行讨论,尤其是不同温度和相对湿度对监测数据的影响,在平均相对湿度为60%~90%时夏季2种方法绝对偏差均值大于10μg/m3,并对该结果进行了原因分析,提出了自动监测的质量控制和比对溯源的建议,为PM_(2.5)的质量浓度监测工作提供了参考依据。     

中俄跨界水体水质联合监测数据可比性研究

中俄跨界水体水质联合监测已经连续开展了11 a,积累了大量的监测数据。笔者针对双方实际监测数据,选用相关性分析和t检验等统计学方法,分析了中俄双方联合监测数据可比性。研究结果表明:p H、溶解氧、高锰酸盐指数和化学需氧量的相对偏差统计容许限基本满足中国标准建议值;氨氮和铁2个指标高于中国标准建议值;锰的数据差异最大。建议中俄双方针对溶解氧使用便携式溶解氧仪进行原位监测;重点对氨氮、铁和锰开展技术交流,设计相关实验,从样品采集、保存、运输、前处理和实验室分析等各环节查找双方差异。     

不同供电方式ESP极板电流密度分布研究

介绍了电除尘器极板电泳密度测试方法和装置，测定了不同极距下脉冲供电和直流供电时，沿电晕极线垂直方向、水平方向及整个极板上电流密度的分布结果，得出在同等条件下，脉冲供电的极析电流密度分布比直流供电的更加均匀，有利于改善电除尘器运行。     

RESOLUTION OF IMPACTS OF RUNOFF EVENTS ON A WATER SUPPLY RESERVOIR WITH A ROBOTIC MONITORING NETWORK1

A robotic water quality monitoring network is used to resolve the coupled patterns of a natural tracer, specific conductance (SC), and metrics of light scattering and turbidity for Schoharie Creek and downstream Schoharie Reservoir, with particular emphasis on the impacts of runoff events. Strong relationships between these parameters and streamflow, and the propensity for this tributary to plunge in the reservoir in summer and fall based on its lower temperature, are reported. The entry of this stream, the primary tributary, into the reservoir as a turbid density current during runoff events is depicted as distinct and vertically coincident subsurface SC minima and peaks in measures of light scattering. The magnitudes of these signatures imparted to the reservoir's water column are demonstrated to be strongly dependent on the magnitude of the runoff event. The time course of the diminishment of these signatures and longitudinal differences in turbidity within the reservoir are described. The documented patterns of SC and metrics of light scattering provided by the robotic monitoring network offer a rare opportunity to support development and testing of a turbidity model with the necessary attributes of fine temporal and spatial resolution.