An alternative supercritical fluid extraction system for aqueous matrices and its application in pesticides residue analysis

Abstract

Supercritical fluid extraction (SFE) is a rapid and convenient method for the isolation of organic compounds from environmental samples. This paper describes a supercritical carbon dioxide (CO₂) extraction system that uses a newly designed extraction cell to recover organic compounds from an aqueous matrix. Analysis of the extracts by gas chromatography‐electron capture detector (GC‐ECD) indicated that the herbicide trifluralin (2,6‐dinitro‐N,N‐dipropyl‐4‐trifluoromethylaniline) could be quantitatively extracted by using the SFE system proposed with small amounts of sample. The percentage of recovery obtained with the SFE system described was twice as high as the result obtained using a conventional solid‐phase extraction technique. Extraction by SFE was completed in a short period of time using a simple and low‐cost home‐made system that did not require the use of organic solvents.     

Analytical methods for the determination of alachlor,metolachlor, simazine and atrazine mobility in soils

Abstract

A method for the determination of the mobility of the herbicides, alachlor, metolachlor, simazine and atrazine in soil is described . The method is based on the use of soil thin‐layer chromatography (TLC) and does not require the use of radiolabelled compounds. Soil on the TLC plate after development was separated into various bands, the material in each band was extracted with solvents and analyzed by gas chromatography.     

从供应链模式看校企合作的功能与约束条件

将企业供应链管理理论引入到职业教育研究,指出供应链能够降低校企合作的交易成本、机会成本和管理成本,而实现上述功能必须以树立集成化供应链管理观念、构建校企合作的激励与利益协调机制、搭建校企合作的网络信息平台、重组高职院校组织结构与流程为条件。     

基于产品功能的装备环境工程管理思考

首先详细分析了目前装备环境工程实施的现状,指出环境工程管理在其中的核心地位,提出了环境工程管理的三大任务,即保障设计的正确性、保障装备实现过程中各项技术活动与设计的一致性、以及保障后续装备的持续改进完善和升级。在环境适应性设计方面,结合具体工程案例,强调了关注产品顶层环境设计分析、总体与各部分的环境匹配性、全寿命周期环境集合的完备性、环境响应特性调查试验,以及数字仿真的重要性。可为装备环境工程的持续改进和提高提供新思路。     

炼厂"三泥"的生物处理研究

从大港油田筛选和分离出3株以原油为碳源的石油降解菌,初步鉴定为假单胞菌属(Pseudomonas sp.),用这3株菌混合处理某炼厂的"三泥",在适宜的降解条件下,仅需投加混合菌液,无需添加营养物(N,P),可使含油污泥A的残油量从67g/kg降至7.7g/kg,混合油泥试样AB的残油量从19.7g/kg降至3.1g/kg,平均去除率为84%以上,可以实现含油污泥的较为经济的、有效的处理.经生物处理后含油污泥的恶臭味完全消失.     

Construction of MOFs-based nanocomposite membranes for emerging organic contaminants abatement in water

● Application of the MOF-composite membranes in adsorption was discussed. ● Recent application of MOFs-membranes for separation was summarized. ● Separation and degradation for emerging organic contaminants were described. Presence of emerging organic contaminants (EOCs) in water is one of the major threats to water safety. In recent decades, an increasing number of studies have investigated new approaches for their effective removal. Among them, metal-organic frameworks (MOFs) have attracted increasing attention since their first development thanks to their tunable metal nodes and versatile, functional linkers. However, whether or not MOFs have a promising future for practical application in emerging contaminants-containing wastewater is debatable. This review summarizes recent studies about the removal of EOCs using MOFs-related material. The synthesis strategies of both MOF particles and composites, including thin-film nanocomposite and mixed matrix membranes, are critically reviewed, as well as various characterization technologies. The application of the MOF-based composite membranes in adsorption, separation (nanofiltration and ultrafiltration), and catalytic degradation are discussed. Overall, literature survey shows that MOFs-based composite could play a crucial role in eliminating EOCs in the future. In particular, modified membranes that realize separation and degradation might be the most promising materials for such application.     

Unanswered questions on the airborne transmission of COVID-19

Environmental Chemistry Letters - Policies and measures to control pandemics are often failing. While biological factors controlling transmission are usually well explored, little is known about...     

镉对孕鼠胎盘激素合成功能的毒性效应

为探究孕期低剂量镉暴露对胎盘激素合成功能的毒性效应,选择雌三醇和孕酮激素作为研究对象,基于研究的孕期低剂量镉暴露小鼠模型,通过生物化学方法检测镉暴露小鼠的血液和胎盘中的雌三醇和孕酮激素含量及其合成底物浓度,并通过实时定量PCR法对胎盘中相关激素合成基因的表达水平进行检测.结果表明,孕期低剂量镉暴露可导致小鼠血清和胎盘中...     

云南喀斯特关键带植被时空变化特征及气候与人为影响因子解析

受自然环境及人类活动的影响,滇东南喀斯特地区石漠化问题严重,当地生态环境面临巨大压力.基于MODIS-NDVI数据通过像元二分模型提取植被覆盖度FVC,采用回归与残差分析等方法对2000 ～ 2016年植被覆盖时空变化特征和趋势进行了分析,并对影响其变化的气候和人为因子进行了解析.研究结果表明:近17年研究区FVC总体呈波动上升的趋势,增长速率为春季(0.005 0/a)＞冬季(0.004 3/a)＞秋季(0.004 0/a)＞夏季(0.000 3/a),年增长速率0.003 6/a.2000年以来FVC呈增加趋势的区域占研究区总面积比例在85％以上,而在市域、县域中心区以减少为主.研究区分别有56.41％、61.47％的FVC与气温、降水因子的相关系数通过0.05的显著性检验,主要呈正相关关系.2000～2016年研究区受人类活动影响持续增加的面积占总面积80.54％,持续减弱的面积占13％,影响不变的面积占6.46％,人类活动对FVC变化的影响呈持续加强的趋势.研究结果将为定量评估喀斯特区域石漠化综合治理工程和生态修复评估提供科学依据.     

Acidification of lead/zinc mine tailings and its effect on heavy metal mobility

The acid-forming potential of lead/zinc (Pb/Zn) mine tailings at Lechang City of Guangdong Province was studied using both net acid generation (NAG) and acid-base accounting (ABA) methods. The pyritic and total sulfur contents of the tailings were 12.6% and 18.7%, respectively. The mean acid neutralization capacity (ANC) was 63.5 kg H2SO4/t while three oxidized tailings samples had an ANC less than zero. The NAG and net acid production potential (NAPP) values were 220 and 326 kg H2SO4/t, and both the NAG and NAPP results indicated that the tailings had a high acid-forming potential. NAG was more accurate than NAPP in predicting acid-forming potential of the tailings due to uncompleted oxidization of pyritic sulfur. Analysis of samples from two profile tests indicated that acidification mainly occurred at the surface (0-20 cm) and had little effects at deep layer of the tailings. Total concentrations of Pb, Zn, Cu, and Cd were increased greatly with depth at the acidified tailings profile, while heavy metal concentrations at different depths of nonacidified tailings profile were similar. The results indicated that depletion of heavy metals at the acidified surface was due to acidification. The diethylenetetramine pentaacetic acid (DTPA)-extractable Pb, Zn, Cu, and Cd concentrations of acidified tailings surface (0-20 cm) were significantly higher than those of nonacidified tailings, which further revealed that acidification enhanced the mobility of heavy metals in the tailings.