A simple ligandless microextraction method based on ionic liquid for the determination of trace cadmium in water and biological samples

A simple and efficient ionic liquid-based ligandless microextraction method has been developed for preconcentration of cadmium ions (Cd²⁺) as a step prior to its determination by flame atomic absorption spectrometry (FAAS) with a micro-sample introduction system. In this approach, the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate [C₄mim][PF₆] and ethanol were used as extractant and dispersive solvents to preconcentrate the Cd²⁺ in different waters, acid digested scalp hair, and nail samples. Some analytical parameters influencing the extraction efficiency of Cd²⁺ and its subsequent determination, including pH, IL volume, dispersant solvent volume, sample volume, temperature, incubation time, and matrix effect, were optimized. Under optimal conditions, the limit of detection (LOD), limit of quantification (LOQ), and enhancement factor (EF) were 0.4 μg L^?1, 1.3 μg L^?1, and 50, respectively. The relative standard deviation (RSD) of 100 μgL^?1 Cd²⁺ was 4.3% (n = 6). The validity of the proposed method was checked by determining Cd²⁺ in certified reference material (TM-25.3 fortified water) and standard addition; the results showed sufficient recovery (>98%) of Cd²⁺ within the certified value. The method was applied for preconcentration and determination of cadmium in waters and biological samples.     

离子液体对三种农作物发芽和生长的毒性研究

为了考察离子液体的生态毒性,研究了5种离子液体及其浓度变化对3种农作物发芽及生长状况的影响。结果表明：就种子发芽这一生态毒理指标而言,不同作物对离子液体毒性的敏感程度不同,其次序为黄瓜>玉米>白菜;在一定浓度下,离子液体对白菜、黄瓜和玉米均具有一定的毒害作用;对于所考察的5种离子液体,阴离子为卤素的［EMIM］Br和［BMIM］Cl对植物发芽和生长的抑制作用远大于阴离子为烷基硫酸酯和烷基磷酸酯的同类离子液体 ［EMIM］［ES］、［EMIM］［DEP］和［MMIM］［DMP］。这种毒性顺序可能与卤素离子对细胞膜较强的穿透能力和由于离子液体的稳定性所造成的阴阳“离子对”的共迁移有关。     

A Native Species with Invasive Behaviour in Coastal Dunes: Evidence for Progressing Decay and Homogenization of Habitat Types

A new species has recently invaded coastal dune ecosystems in North West Europe. The native and expansive inland grass, Deschampsia flexuosa, progressively dominating inland heaths, has recently invaded coastal dunes in Denmark, occasionally even as a dominant species. A total of 222 coastal locations with 5,000 random sample plots have been investigated. These findings are in contrast to historical records, and D. flexuosa has never been considered belonging to coastal dune ecosystems. The occurrence of the typical inland grass in the coastal dunes is a strong indication of increase in nutrient level and that human influences may cause a native species to be invasive in new ecosystems. This could be a radical example of change in species composition due to a long lasting exceedance of critical load of nitrogen. The investigation also showed a general increase in cover of the most dominant species.     

Synthesis and anti-microbial activity of hydroxylammonium ionic liquids

Eight hydroxylammonium-based room temperature ionic liquids (ILs) have been synthesized by acid-base neutralization of ethanolamines with organic acids. The ILs were characterized by infrared and nuclear magnetic resonance spectroscopies and elemental analysis. Their anti-microbial activities were determined using the well-diffusion method. All eight ILs were toxic to Staphylococcus aureus, while 2-hydroxyethylammonium lactate and 2-hydroxy-N-(2-hydroxyethyl)-N-methylethanaminium acetate showed high anti-microbial activity against a wide range of human pathogens.     

不同地貌类型区城镇扩展对土地利用景观格局的影响

基于RS和GIS的支持,以名山县为研究案例,分析与探讨西部经济以农业为主地区城镇扩展的时空特征和不同地貌类型下土地利用景观格局,以期为城镇规划及区域城镇可持续发展提供决策支持。结果显示：1975 ~ 1999 年土地利用类型在不同地貌区的分布格局变化显著。林地面积大幅减少,分布区域向海拔较高地区收缩。居民及建设用地在低丘区增长较快,城镇用地大幅增加,成为影响研究区景观格局的重要要素。农业生产活动向地势较高的区域扩展,中丘区成为农业生产的主要场所,水田和旱地成其主要土地利用方式。高丘区旱地分布面积占首位;园地在低山区分布面积有所增加。1999~2005 年基本维持1999年景观格局,居民及建设用地继续增长,尤其在低丘区表现明显;低丘和中丘区斑块总数减少,各景观要素平均斑块面积增加,形状指数和分维数降低;高丘、低山区水田、旱地减少,园地面积增加.     

Using conditional inference forests to identify the factors affecting crash severity on arterial corridors

Introduction

The study aims at identifying traffic/highway design/driver-vehicle information significantly related with fatal/severe crashes on urban arterials for different crash types. Since the data used in this study are observational (i.e., collected outside the purview of a designed experiment), an information discovery approach is adopted for this study.

Method

Random Forests, which are ensembles of individual trees grown by CART (Classification and Regression Tree) algorithm, are applied in numerous applications for this purpose. Specifically, conditional inference forests have been implemented. In each tree of the conditional inference forest, splits are based on how good the association is. Chi-square test statistics are used to measure the association. Apart from identifying the variables that improve classification accuracy, the methodology also clearly identifies the variables that are neutral to accuracy, and also those that decrease it.

Results

The methodology is quite insightful in identifying the variables of interest in the database (e.g., alcohol/ drug use and higher posted speed limits contribute to severe crashes). Failure to use safety equipment by all passengers and presence of driver/passenger in the vulnerable age group (more than 55 years or less than 3 years) increased the severity of injuries given a crash had occurred. A new variable, ‘element’ has been used in this study, which assigns crashes to segments, intersections, or access points based on the information from site location, traffic control, and presence of signals.

Impact

The authors were able to identify roadway locations where severe crashes tend to occur. For example, segments and access points were found to be riskier for single vehicle crashes. Higher skid resistance and k-factor also contributed toward increased severity of injuries in crashes.     

Lead sorption by a Mexican,clinoptilolite-rich tuff

Goal, Scope and Background The retention of lead by a Mexican, clinoptilolite-rich tuff from Oaxaca (Mexico) at different pH values was evaluated and the lead sorption mechanisms on the zeolitic material in this work were discussed. Methods Isotherms were determined using lead nitrate solutions (initial pH values between 2 and 5) at 303 K. After the equilibrium was reached, the content of lead in the liquid phases was determined by atomic absorption spectrometry. The elemental composition of the clinoptilolite-rich tuff before and after the lead sorption process was evaluated by electron microscopy. Results The maximum ion exchange capacity of the Mexican, clinoptilolite-rich tuff for lead was 1.4 meq/g at pH 3, considering an ion exchange mechanism in the absence of any precipitated or hydrolyzed lead species in the sorption process or any change in the zeolite network. Langmuir and Freundlich isotherms were also considered in this work for comparison purposes. Discussion It is important to consider the nature of the sorption processes before choosing a model to describe the interaction between the metal ions and the sorbent. Conclusions The chemical lead speciation, the pH, as well as the characteristics of the clinoptilolite-rich tuff are important factors to be considered on the lead sorption process by natural zeolites. The chemical species involved in that process are Na⁺ from the zeolite and Pb²⁺ from the aqueous solution at pH 2 and 3, so that the ion exchange mechanism explains the lead sorption processes by the clinoptilolite-rich tuff through the ion exchange isotherms. The sodium, Mexican, clinoptilolite-rich tuff is a potential adsorbent for lead from aqueous solutions. Recommendations and Perspectives The natural zeolite-rich tuffs are very important as ion exchangers for the treatment of polluted water due to their sorption properties and low cost. The sorption behavior of each natural material depends on their composition. Mexican, clinoptilolite-rich tuff from Oaxaca (Mexico) could be used for the treatment of waste water contaminated with lead. It would be important to propose this material as an alternative as waste water treatment, because it shows good selectivity for the removal of heavy metals from water.     

离子强度对恒电荷土壤胶体吸附Cu2+和Pb2+的影响

采用平衡法研究了离子强度、表面电位对恒电荷土壤胶体吸附Ｃｕ２＋和Ｐｂ２＋的影响．结果表明,离子强度越小,表面电位越高,土壤胶体对Ｃｕ２＋和Ｐｂ２＋的吸附量越大．在离子强度小于１．０ｍｏｌ·ｋｇ－１范围内,土壤胶体对Ｃｕ２＋和Ｐｂ２＋的吸附包括静电吸附和专性吸附;离子强度大于１．０ｍｏｌ·ｋｇ－１以后,土壤胶体对Ｃｕ２＋和Ｐｂ２＋的吸附受专性吸附控制．     

粉末凹凸棒石对水溶性阳离子染料废水的脱色研究

本文研究了凹凸棒石粘土处理阳离子染料废水的吸附脱色规律。结果表明,粉末凹凸棒石对水溶性阳离子染料具有优良的脱色效果。例如,染料初始浓度１００ｍｇ·ｌ＾－１（色度相当于２２００￣４０００倍）,粘土投加量０．５％,七种被研究的阳离子染料废水平均脱色率近９９％,吸附机理主要是离子交换。     

武汉市春季大气PM2.5中水溶性离子特征

运用大气PM_(2.5)水溶性组分及其气态前体物在线监测系统(GAC-IC)于2017年3月5—12日对武汉市大气PM_(2.5)中水溶性组分进行了在线监测,分析了PM_(2.5)中主要水溶性离子的化学特征和作用机制。结果表明:实验期间武汉市大气PM_(2.5)中水溶性组分与气态前体物间存在明显的二次转化过程,二次反应是PM_(2.5)的重要来源。监测期间,PM_(2.5)中NO_3~-、SO_4~(2-)和NH_4~+的平均质量浓度分别为24.3、16.9、15.0μg/m~3,是PM_(2.5)中重要的水溶性无机离子,占PM_(2.5)质量浓度的40%~70%。硫氧化率(SOR)和氮氧化率(NOR)平均值分别为0.52和0.27,表现出较为明显的二次污染特征。通过相关性分析发现:监测点位周边大气PM_(2.5)中NH_4~+与NO_3~-、SO_4~(2-)有良好的相关性,且表现为富氨状态,大气中铵能较好地中和SO_4~(2-)和NO_3~-。