Sorption of organic compounds to activated carbons. Evaluation of isotherm models

Sorption to ‘hard carbon’ (black carbon, coal, kerogen) in soils and sediments is of major importance for risk assessment of organic pollutants. We argue that activated carbon (AC) may be considered a model sorbent for hard carbon. Here, we evaluate six sorption models on a literature dataset for sorption of 12 compounds onto 12 ACs and one charcoal, at different temperatures (79 isotherms in total). A statistical analysis, accounting for differences in the number of fitting parameters, demonstrates that the dual Langmuir equation is in general superior and/or preferable to the single and triple Langmuir equation, the Freundlich equation, a Polanyi–Dubinin–Manes equation, and the Toth equation. Consequently, the analysis suggests the presence of two types of adsorption sites: a high-energy (HE) type of site and a low-energy (LE) type of site. Maximum adsorption capacities for the HE domain decreased with temperature while those for the LE domain increased. Average Gibbs free energies for adsorption from the hypothetical pure liquid state at 298 K were fairly constant at −15 ± 4 and −5 ± 4 kJ mol⁻¹ for the HE and LE domain, respectively.     

Marine Eutrophication: A Proposed Data Analysis Procedure For Assessing Spatial Trends

A methodology for the discrimination of the different trophic levels at a spatial scale in the marine environment is proposedusing spatial analysis methods and non-parametric statistics. Phytoplankton cell number, being a representative parameter to express trophic trends in the marine ecosystem is selected forthe methodology development; Saronicos Gulf, Greece is used for the case study. The proposed stepwise methodology includes interpolation for assessing the spatial distribution of phytoplankton cell number, division of the Gulf into a number of quadrates, development of a scale characterising trophic levels and finally characterisation of the trophic state ofeach quadrate using non-parametric statistics. The advantages of this methodology and the potential applications in coastal management studies are also discussed.     

Location and Characterization of Emission Sources for Airborne Volatile Organic Compounds Inside a Refinery in Taiwan

This study aimed to locate VOC emission sources and characterized their emitted VOCs. To avoid interferences from vehicle exhaust, all sampling sites were positioned inside the refinery. Samples, taken with canisters, were analyzed by GC–MS according to TO-14 method. The survey period extended from Febrary 2004 to December 2004, sampling twice per season. To interpret a large number of VOC data was a rather difficult task. This study featured using ordinary application software, Excel and Surfer, instead of expensive one like GIS, to overcome it. Consolidating data into a database on Excel facilitated retrieval, statistical analysis and presentation in the form of either table or graph. The cross analysis of the data suggested that the abundant VOCs were alkanes, alkenes, aromatics and cyclic HCs. Emission sources were located by mapping the concentration distribution of these four types of VOCs in terms of contour maps on Surfer. During eight surveys, five emission sources were located and their VOCs were characterized.     

基于文献计量学的“十三五”生态环境监测研究热点分析

利用科学计量与可视化相关工具,以《中文核心期刊要目总览(2017年版)》27种环境科学类核心期刊发表的2016—2020年生态环境监测论文数据为基础,从载文量分布、高被引论文、高产机构分布和技术主题分布等方面分析了\"十三五\"期间我国生态环境监测研究热点。结果表明:\"十三五\"期间生态环境监测论文数量有所增加,主要载文期刊分布于《环境科学》《中国环境监测》《环境科学与技术》;主要发文机构是中国环境科学研究院、中国环境监测总站、中国科学院大学;排名前10位的技术主题词分别是PM_(2.5)、重金属、土壤、污染特征、颗粒物、挥发性有机物、生态风险、臭氧、沉积物、多环芳烃,结合\"十三五\"前期和中后期热点主题词变化分析了生态环境监测研究关注点的变化趋势。     

Spatio-temporal patterns in county-level incidence and reporting of Lyme disease in the northeastern United States, 1990–2000

We present an exploratory analysis of reported county-specific incidence of Lyme disease in the northeastern United States for the years 1990–2000. We briefly review the disease ecology of Lyme disease and the use of risk maps to describe local incidence as estimates of local risk of disease. We place the relevant elements of local environmental and ecological variables, local disease incidence, and (importantly) local disease reporting in a conceptual context to frame our analysis. We then apply hierarchical linear models of increasing complexity to summarize observed patterns in reported incidence, borrowing information across counties to improve local precision. We find areas of increasing incidence in the central northeastern Atlantic coast counties, increasing incidence branching to the north and west, and an area of fairly stable and slightly decreasing reported incidence in western New York.     

Bayesian model-based cluster analysis for predicting macrofaunal communities

To predict macrofaunal community composition from environmental data a two-step approach is often followed: (1) the water samples are clustered into groups on the basis of the macrofauna data and (2) the groups are related to the environmental data, e.g. by discriminant analysis. For the cluster analysis in step 1 many hard, seemingly arbitrary choices have to be made that nevertheless influence the solution (similarity measure, clustering strategy, number of clusters). The stability of the solution is often of concern, e.g. in clustering by the program. In the discriminant analysis of step 2 it can occur that a water sample is misclassified on the basis of the environmental data but on further inspection happens to be a borderline case in the cluster analysis. One would then rather reclassify such a sample and iterate the two steps. Bayesian latent class analysis is a flexible, extendable model-based cluster analysis approach that recently has gained popularity in the statistical literature and that has the potential to address these problems. It allows the macrofauna and environmental data to be modelled and analyzed in a single integrated analysis. An exciting extension is to incorporate in the analysis prior information on the habitat preferences of the macrofauna taxa such as is available in lists of indicator values. The output of the analysis is not a hard assignment of water samples to clusters but a probabilistic (fuzzy) assignment. The number of clusters is determined on the basis of the Bayes factor. A standard feature of the Bayesian method is to make predictions and to assess their uncertainty. We applied this approach to a data set consisting of 70 water samples, 484 macrofauna taxa and four environmental variables for which previously a five cluster solution had been proposed. The standard for Bayesian estimation, the Gibbs sampler, worked fine on a subset with only 12 selected taxa but did not converge on the full set with 484 taxa. This is due to many configurations in which the assignment probabilities are all very close to either 0 or 1. This convergence problem is comparable with the local optima problem in classical cluster optimization algorithms, including the EM algorithm used in Latent Gold, a Windows program for latent class analysis. The convergence problem needs to be solved before the benefits of Bayesian latent class analysis can come to fruition in this application. We discuss possible solutions.     

内蒙古达里诺尔湖湖泊水体与入湖河水水化学特征及控制因素

为摸清内蒙古达里诺尔湖湖泊水体与入湖河水的水化学主要离子组成特征及其控制因素,于2013年6-9月对湖水、河水进行采样.采用水化学类型三角图分析不同湖水与河水的主要离子组成,利用Gibbs图分析水体化学成分主要驱动因素,在此基础上,运用河水主要离子比例关系图进一步分析入湖河水离子主要来源.结果显示,达里诺尔湖湖水总溶解固体（TDS）含量范围为5800-6170 mg·L-1,平均值为5990 mg·L-1,入湖河水TDS含量范围为140-310 mg·L-1,平均值为200 mg·L-1,远低于湖水的TDS值.入湖的河水属于淡水,而湖水则已演变为中度咸水.湖水、河水主离子组成以及水化学类型具有一定的差异,其中,湖水离子含量特征为HCO3-（2564.60 mg·L-1） >Cl-（2025.29 mg·L-1） >SO42-（424.02 mg·L-1）,Na+（2070.68 mg·L-1） >K+（159.24 mg·L-1） >Mg2+（20.04 mg·L-1） >Ca2+（5.09 mg·L-1）;河水离子含量特征为HCO3-（118.93 mg·L-1） >Cl-（24.99 mg·L-1） >SO42-（11.77 mg·L-1）,Na+（49.84 mg·L-1） >Ca2+（27.83 mg·L-1） >Mg2+（14.55 mg·L-1 ） >K+（6.56 mg·L-1）;依据阴、阳离子所占比例进行分类,湖水的水化学类型为Cl-HCO3-Na型,贡格尔河为Cl-HCO3-SO4-Na-Ca型,浩来河为Cl-HCO3-Na-Ca-Mg型,沙里河为HCO3-Na-Mg型,亮子河为HCO3-Ca-Na型.从水化学驱动因素上看,其水化学组成自然起源主要受自身蒸发-结晶作用的影响,部分区域受到农业活动、放牧及旅游业等人类活动影响,而贡格尔河、浩来河、亮子河及沙里河4条入湖河水的水化学组成落在Gibbs模型的中部,则主要受岩石风化作用控制,4条河流主要受碳酸岩风化影响,钠硅酸岩风化对河水中阳离子的贡献也较大.结合入湖河水水质、水化学驱动因素分析,近年来湖水水体盐化主要是受湖区蒸发量增大、入湖流量减少、湖区面积萎缩的影响,入湖盐分的贡献及人类活动的影响则相对较小.     

雨季冲击条件下活性污泥呼吸图谱的变化

通过模型实验考察了雨季合流污水水量冲击以及冲击过后恢复初始状态过程中活性污泥的呼吸图谱变化规律。结果表明：雨季冲击下好氧池污泥浓度降幅较自、异养菌呼吸速率大;异养菌呼吸速率降幅较自养菌大。而COD去除率降幅小,NH4+-N去除率降幅大,与自养菌、异养菌呼吸速率的降幅不一致。表明异养菌虽受冲击影响较大,但因其所占污泥比例仍较大,COD处理的缓冲能力大;自养菌占污泥比例较小,虽受冲击的影响较小,但对NH4+-N处理的缓冲能力较小;另一方面,大雨冲击下自养菌呼吸比例上升10%,异养菌呼吸比例下降6%,表明在冲击过程中污泥中微生物结构有小幅变化。