焚烧烟气二噁英连续采样的捕集方法与应用

焚烧烟气二噁英监测是环境监管的重要任务。针对焚烧烟气二噁英捕集方法,开展了双柱串联捕集技术研究,并与传统的冷凝吸附方法进行比较评估。研究发现:采用冷凝吸附法进行焚烧烟气二噁英采样,如果冷凝水和烟气同时通过单一XAD2树脂,其捕集效率不能满足二噁英采样的要求;烟气二噁英采样过程中,将采样内标添加于XAD2上无法准确反映XAD2的捕集情况;双柱串联可以解决单柱采样二噁英随冷凝水穿透损失的问题。同时研究了活性炭喷射量对二英排放的影响,发现活性炭的喷射量能够显著影响二噁英的排放浓度,活性炭对不同二噁英同族体的排放影响不同。

11种吸附剂上二噁英的热吸附/脱附性能评价

筛选在低温下高效捕集并在一定的高温下可以快速完全脱附二噁英的吸附/脱附材料是二噁英在线热捕集的关键。该研究以1,2,3,4-四氯代二苯并-对-二噁英(1,2,3,4-TCDD)和1,2,3,8,9-五氯代二苯并呋喃(1,2,3,8,9-PCDF)为二噁英模型物,以电子捕获检测器(ECD)作为检测器,利用填充柱气相色谱系统,测定了这两种二噁英单体在11种吸附剂上4~5个温度点下的保留体积,并建立了相应的范特霍夫方程。结果表明,11种吸附剂的线性方程决定系数(R2)均大于0.96。根据范特霍夫方程,预测了吸附剂在120、150、180℃时的气固分配系数(KSA)。弗洛里硅土在120、150、180℃3个温度点下都具有最强的吸附能力,特别是在120℃时,1,2,3,4-TCDD、1,2,3,8,9-PCDF在弗洛里硅土上的KSA分别高达1.82×10^(8)m^(3)/g、1.46×10^(13)m^(3)/g。碳基吸附剂的高分子多孔微球GDX系列的GDX-101、GDX-102、GDX-103、GDX-105、GDX-203在最高耐受温度270℃下都可以实现二噁英的热脱附,证实了碳基吸附剂作为二噁英热吸附/脱附的吸附剂的可行性。310℃下,在丝光沸石上1,2,3,4-TCDD可实现热脱附,而1,2,3,8,9-PCDF在相同条件下无法实现热脱附,体现了沸石对二噁英同系物的选择性吸附的特性。而硅藻土和蒙脱土对气相中的二噁英几乎没有吸附能力,不适合作为二噁英热捕集的吸附剂。弗洛里硅土、硅胶、氧化铝、GDX-102、GDX-103和GDX-203对1,2,3,4-TCDD、1,2,3,8,9-PCDF都具有很强的吸附能力,因此被初步选为二噁英的候选吸附剂。通过比较120℃下和270℃下二噁英在这6种吸附剂上的ln K_(SA),发现弗洛里硅土在两个温度点下的保留体积都是最大的;在侧重低温下二噁英的热捕集性能时,弗洛里硅土是捕集二噁英的最佳吸附剂;而GDX-102是6种吸附剂中ln K_(SA,270℃)最小的,在侧重高温下二噁英的热脱附性能时,GDX-102是二噁英热脱附的最佳吸附剂。同时,硅胶、GDX-103和GDX-203的ln K_(SA,120℃)和ln K_(SA,270℃)与GDX-102相近,也可以作为快速热吸附/脱附的材料。该文通过系统评价1,2,3,4-TCDD和1,2,3,7,8-PCDF在11种吸附剂的热吸附/脱附性能,对简化二噁英的采样和制备过程提供了新的解决思路,为实现二噁英的热捕集提供了技术支撑。

土壤中石油烃检测的前处理新方法:硅胶脱水-环己烷提取

石油作为全球主要能源之一,所带来的环境污染越来越严重。土壤中的石油烃是环保监测的重要组成部分。现有土壤中石油烃检测的主流方法是以丙酮与正己烷的混合溶剂进行提取,旋蒸后利用无水硫酸钠去除残余水分,再用硅镁型吸附剂净化后进行下一步检测。现有方法步骤繁琐,耗时长,需消耗大量有机溶剂,且旋蒸设备不具便携性,难以应用于现场分析。土壤中石油烃提取的关键在于有效去除土壤中的水分。本工作通过对现有标准方法和文献方法的优化和改进,建立了一种新的土壤中石油烃(C10~C40)的前处理方法:硅胶脱水-环己烷提取。其具体步骤是在土壤样品中加入硅胶,经过混合研磨脱除土壤中的水分,然后采用环己烷浸泡提取、Florisil固相小柱净化,即可进行测试。以气相色谱对该方法进行了系统测评,实验结果表明当加入土壤实际含水质量10倍的硅胶、以40 mL环己烷浸泡提取15 min时,能够获得较满意的提取效果。本方法的回收率为74.1%~103.8%,相对标准偏差(RSD)为1.7%~10.1%。本方法简化了样品前处理步骤,减少了有毒溶剂的使用,降低了对环境的污染,提高了工作效率,不仅可用于石油烃的实验室分析,也为石油烃现场快速分析奠定了良好基础。

青蒿素类药物缓解自身免疫病及其机制的研究现状

近年来研究发现青蒿素类抗疟药物具有免疫抑制及免疫调节活性,可以抑制CD4^+炎性T细胞如Th1、Th17,提高免疫抑制细胞Treg比例,治疗自身免疫病,但其具体作用机制尚不十分清楚。自身免疫病大多为慢性或进行性疾病,需要长期用药。激素类药物及免疫抑制剂作为治疗自身免疫病的传统药物,长期使用存在免疫抑制、继发感染、代谢紊乱等严重的副作用,因此临床上迫切需要高效低毒的替代药物。本文就青蒿素类药物缓解类风湿关节炎、系统性红斑狼疮、多发性硬化、自身免疫肝炎、IgA肾病和炎症性肠病等自身免疫病的作用及相关机制进行综述。

Thermal Degradation of PCDD/Fs Promoted by Alcohol Amines in Different Types of Incinerator Ashes

The low-temperature thermal treatment to degrade PCDD/Fs contained in fly ash was promoted by alcohol amines in a closed system. Three types of fly ash collected separately from municipal solid waste incinerator, medical waste incinerator and hazardous waste incinerator, were compared. Experimental design was used to investigate the homologue patterns of PCDD/Fs and distribution of the toxic congeners in fly ash from incinerator after thermal treatment promoted by alcohol amines. The effect of ethanolamine (MEA) on the hydrodechlorination reaction of polychlorinated aromatics pollutants on fly ash from solid waste incinerator was carried out, and the three ashes clearly showed different degradation potentials for PCDD/F during thermal treatment. Results from the present study indicate that (1) the concentration of alkaline species and metals strongly influenced the degradation of PCDD/F; (2) after addition of 8% MEA, the toxicity equivalent (TEQ) values of PCDD/Fs in fly ash were significantly lower than those obtained without MEA. 49%–71% of PCDD/Fs in TEQ was removed from different types of ash at 250℃ with 8% MEA; (3) the destruction and dechlorination are major mechanism for PCDD/Fs degradation.

Concentrations and gas-particle partitioning of PCDD/Fs in the urban air of Dalian,China

PCDD/Fs in the urban air of Dalian,China were monitored with high-volume active sampler from November 2009 to October 2010.The concentration of Cl 4-8 DD/Fs ranged from 3065 to 49538 fg m-3,with an average of 10249 fg m-3.The international toxic equivalents(I-TEQ) value of that was 61.8 1182 fg m-3,with an average of 235 fg m-3,which was comparable to those in the other urban locations around the world.It was found that the Cl 4 8 DD/Fs appeared to be present mainly in the particle phase during winter,spring and autumn,while during summer which were dominantly in gas phase.The ratio of Cl 4-8 DD/Fs present in particle phase increased with the increasing level of chlorination.The concentrations of PCDFs and PCDDs decreased with the increase of chlorinated level,while the concentrations of 2,3,7,8-PCDDs congeners increased with the increase of chlorination level.The homolog profiles of the concentrations of PCDFs presented were higher than those of the PCDDs,which indicated the PCDD/Fs pollution source of the air in Dalian was characteristic for thermal source pollution.The correlation analysis of meteorological parameters with the concentrations of Cl 4-8 CDD/Fs was conducted using SPSS packages,and it was found that the ambient temperature and atmospheric pressure were important factors influence the concentration of PCDD/Fs in the air.The respiratory risk and intake dioxins of the residents around the sampling sites were studied in the paper.It was found that Junge-Pankow model was much more accurate in predicting the gas-particle partitioning behavior of PCDD/Fs homologues during winter,while the Harner-Bidleman model shows better agreement with the measured data during winter and summer.