COVID-19 fear and volatility index movements: empirical insights from ASEAN stock markets

Environmental Science and Pollution Research - This research aims to look into the effect of COVID-19 on emerging stock markets in seven of the Association of Southeast Asian Nations’...     

固相萃取-气相色谱-质谱-选择离子法检测污水中壬基酚

壬基酚是城市污水和再生水中的1种痕量污染物,具有内分泌干扰作用.由于壬基分支程度的不同,有多种同分异构体存在,基体背景复杂,定量检测困难.采用固相萃取-气相色谱-质谱和选择性离子定量分析方法,对70多个污水和再生水样品中壬基酚同分异构体总量进行了定量检测.结果表明,亲水-亲脂平衡固相萃取柱对壬基酚有良好选择吸附能力,不同水样的浓缩倍数在50～200倍之间.在壬基酚各异构体质谱图中,107、121、135、149、163这5种离子的丰度较高,特异性较强,其响应值总和(∑SIM)占总离子流(TIC)的54.4%～73%,以∑SIM(107、121、135、149、163)色谱图的积分面积作为定量检测的依据,既准确地反映各种异构体的组成,又排除了背景离子的干扰,确保了方法的选择性、准确度和精密度.     

Assessment of heavy metal bioavailability in contaminated sediments and soils using green fluorescent protein-based bacterial biosensors

A green fluorescent protein (GFP)-based bacterial biosensor Escherichia coli DH5alpha (pVLCD1) was developed based on the expression of gfp under the control of the cad promoter and the cadC gene of Staphylococcus aureus plasmid pI258. DH5alpha (pVLCD1) mainly responded to Cd(II), Pb(II), and Sb(III), the lowest detectable concentrations being 0.1 nmol L(-1), 10 nmol L(-1), and 0.1 nmol L(-1), respectively, with 2h exposure. The biosensor was field-tested to measure the relative bioavailability of the heavy metals in contaminated sediments and soil samples. The results showed that the majority of heavy metals remained adsorbed to soil particles: Cd(II)/Pb(II) was only partially available to the biosensor in soil-water extracts. Our results demonstrate that the GFP-based bacterial biosensor is useful and applicable in determining the bioavailability of heavy metals with high sensitivity in contaminated sediment and soil samples and suggests a potential for its inexpensive application in environmentally relevant sample tests.