梯度淋洗快速分析水中多环芳香烃

根据流动相极性理论，采用梯度淋洗一检测器编程方法检测多环芳烃，大大缩短了分析时间，并提高了灵敏度和精密度．为进一步定量分析提供了优良的途径。     

中国东、西部工业污染和经济发展的分析比较

从经济发展水平和工业污染排放角度出发,对比分析了东部、中部和西部3个地区的差异。结果表明,90年代以来,中国的经济发展和工业污染在东、西部之间存在着较显著的差异,所表现出的综合效应是形成了明显的工业污染物排放强度梯度。即在空间上,工业污染物排放强度存在从东部、中部到西部逐渐升高的梯度。建议在西部大开发过程中,要充分利用西部环境保护的后发优势,减缓或遏制工业污染的“西迁”,实现环境保护的跨越式发展。     

Machine learning based quantitative consequence prediction models for toxic dispersion casualty

Incidental release of toxic chemicals can pose extreme danger to life in the vicinity. Therefore, it is crucial for emergency responders, plant operators, and safety professionals to have a fast and accurate prediction to evaluate possible toxic dispersion life-threatening consequences. In this work, a toxic chemical dispersion casualty database that contains 450 leak scenarios of 18 toxic chemicals is constructed to develop a machine learning based quantitative property-consequence relationship (QPCR) model to estimate the affected area caused by toxic chemical release within a certain death rate. The results show that the developed QPCR model can predict the toxic dispersion casualty range with root mean square error of maximum distance, minimum distance, and maximum width less than 0.2, 0.4, and 0.3, which indicates that the constructed model has satisfying accuracy in predicting toxic dispersion ranges under different lethal consequences. The model can be further expanded to accommodate more toxic chemicals and leaking scenarios.     

Low cost measurements of nitrogen and sulphur dry deposition velocities at a semi-alpine site: gradient measurements and a comparison with deposition model estimates

The conditional time averaged gradient method was used to measure air-surface exchange of nitrogen and sulphur compounds at a semi-alpine site in Southern Norway. Dry deposition velocities were then obtained from the bi-weekly concentration gradient measurements. Annual deposition velocities were found to be 1.4, 11.8 and 4.0 mm s(-1) for NH3, HNO3 and SO2, respectively, if all data were included, and to be 10.8, 11.8 and 13.0 mm s(-1), respectively, if only positive values were included. Measured deposition velocities were compared to two sets of values estimated from a big-leaf dry deposition module applying to two different land types (short grass and forbs, and tundra), driven by measured micrometeorological parameters. The deposition module gives reasonable values for this site throughout the year, but does not reproduce the large variability as shown in the measured data. No apparent seasonal variations were found from either measurements or module estimates due to the very low productivity of the studied area.     

梯度淋洗离子色谱法测定饮用水中6种阴离子

采用离子色谱法同时测定饮用水中F-、Cl-、Br-、NO3-、SO24-、PO34-等6种阴离子,水样经0.22μm滤膜过滤,自动淋洗发生器产生20 mmol/L～40 mmol/L KOH淋洗液梯度洗脱,在流量0.25 mL/min条件下采用IonPac AG19保护柱和IonPac AS19分离柱分离和定量。方法线性良好,6种阴离子的检出限为0.005 mg/L～0.057 mg/L,标准溶液平行测定6次,测定值的RSD在0.5%～2.2%之间,水样加标回收率在83%～106%之间。     

梯度模式原理及其应用

本文推导梯度模式，引用大气边界层湍流系数进行实际运算，与现场大气环境监测结果对照；同时与高斯模式计算结果比较，得出该模式在城市复杂流场的实用性．     

Improving the extraction of tetrachloroethylene from soil columns using surfactant gradient systems

In this work, we extend the recently developed gradient approach for surfactant-enhanced remediation of dense non-aqueous phase liquid (DNAPL)-impacted sites. The goal of the gradient approach is to maximize the DNAPL solubilization capacity in swollen micelles (Type I aqueous microemulsions) while at the same time minimizing the potential for DNAPL mobilization. In this work, we introduce a modified version of the capillary/trapping curve that we refer to as the gradient curve to help interpret and/or design the gradient approach. The gradient curve presents the residual DNAPL saturation as a function of interfacial tension and microemulsion viscosity. This approach demonstrates that keeping a low viscosity of the microemulsion phase is not only important for keeping a low head loss during surfactant flooding but also to prevent oil mobilization. Eight microemulsion systems were evaluated in this research; these systems were evaluated based on their tetrachloroethylene (PCE) solubilization capacity, interfacial tension (IFT), viscosity, density, and coalescence kinetics. Two of these systems were chosen for evaluation in site-specific column tests using an increasing electrolyte gradient to produce a decreasing IFT/increasing solubilization gradient system. The column studies were conducted with media from Dover Air Force Base in Dover, DE. Both solubilized and mobilized DNAPL were quantified. During the column studies, we observed that substantial PCE was mobilized when the residual level of PCE in the column was significantly higher than the steady-state residual saturation level being approach (as predicted from the gradient curve). Four column studies were performed, three of which were used to asses the validity of the gradient curve in predicting the residual saturation after each gradient step. From these tests we observed that starting IFTs of less than 1 mN/m all produced the same mobilization potential. In the last column, we used an additional gradient step with an initial IFT above 1 mN/m to dramatically reduce the amount of PCE mobilize. Based on the good agreement between column results and projections based on the gradient curve, we propose this as a preferred method for designing gradient surfactant flushing systems.     

A wave change analysis (WCA) method for pipeline leak detection using Gaussian mixture model

This paper presents a novel pipeline leak detection scheme based on gradient and slope turns rejection (GSTR). Instead of monitoring the pipeline under constant working pressure, GSTR introduces a new testing method which obtains data during the transient periods of different working pressures. A novel pipeline leak detection method based on those transient data without failure history is proposed. Wavelet packet analysis (WPA) is applied to extract features which capture the dynamic characteristics from the non-stationary pressure data. Principal component analysis (PCA) is used to reduce the dimension of the feature space. Gaussian mixture model (GMM) is utilized to approximate the density distribution of the lower-dimensional feature space which consists of the major principal components. Bayesian information criterion (BIC) is used to determine the number of mixtures for the GMM and a density boosting method is applied to achieve better accuracy of the distribution estimation. An experimental case study for oil pipeline system is used as an example to validate the effectiveness of the proposed method.     

白洋淀两种生境中芦苇地上生物量及其影响因子分析

文章在野外调查的基础上,在白洋淀台田和沼泽中各选择6个样区,统计分析了2种生境芦苇地上生物量;运用冗余分析方法(RDA),分析了芦苇生长季(4~9月)平均水深、土壤/底泥有机质、全氮和全磷等对两类生境中芦苇地上生物量的影响。结果表明,台田、沼泽中芦苇地上生物量分别为1408.2±527.5 g DW/m^2、723.2±109.1 g DW/m^2,两类生境中的芦苇地上生物量沿水深梯度均呈先增加后减小的变化趋势。台田芦苇在水深为?77.3 cm时地上生物量最大,为2065 g DW/m^2,沼泽芦苇在水深为59.7 cm时地上生物量最大,为869.2 g DW/m^2。台地芦苇地上生物量与水深的相关系数为?0.813(P<0.05),与其他3个环境因子的相关性不显著;沼泽芦苇地上生物量与4个环境因子的相关性均不显著,表明沼泽芦苇地上生物量的影响因素较为复杂。     

Altitude dependence of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in surface soil from Tibetan Plateau, China

Remote mountain areas besides high latitude regions are beginning to receive increased attention in studying the transport and behavior of persistent organic pollutants (POPs). In the present work, surface soil samples were collected from the Tibetan Plateau, the highest plateau in the world which includes the northern slope of Mt. Qomolangma, to investigate the levels and trends of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) along the altitudinal gradient. The average PCB and PBDE concentrations were 185.6 ng kg⁻¹ dry weight (dw) (range 47.1–422.6 ng kg⁻¹ dw) and 11.1 ng kg⁻¹ dw (range 4.3–34.9 ng kg⁻¹ dw), respectively. Regression analysis between the log-transformed TOC-normalized concentrations and the altitudes of the sampling sites showed two opposite trends with regard to altitude dependence: negative relationship with altitude below about 4500 m followed by a positive altitude dependence above this point. Considering minimum anthropogenic activities and very sparse precipitation in the north of Himalayas, the trends above 4500 m imply that the significant altitude dependence of these two groups of POPs were irrespective of pollution sources, but could be predicted by the global distillation effect involving cold condensation in high altitude mountain areas. Increasing levels of heavier congeners were found in higher altitude sites, although the lighter congeners were the main contributors to the total amount, suggesting that less volatile congeners seem to become enriched easier than those more volatile at higher altitudes in this region.