Estimation and characterization of PCDD/Fs and dioxin-like PCBs from Chinese iron foundries

The iron foundry industry is considered to be a potential source of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). This study investigated the emission factors and total emission amounts of PCDD/Fs and dioxin-like polychlorinated biphenyls (DL-PCBs) from iron foundries in China. The concentrations and the World Health Organization toxicity equivalents (WHO-TEQs) are presented and the congener profiles are discussed in this paper.In the present work, 26 fly ash samples were collected and tested to quantify the PCDD/Fs and DL-PCBs generated by 14 plants of different scales, and five stack gas samples were collected from two (named as EFG and LFG) of those plants. The emission levels of PCDD/Fs and DL-PCBs indicated that hot-air cupolas had lower emissions than cold-air cupolas. When iron ore lump and sinter were used as raw material, the emission factors were about 250 ng TEQ t⁻¹ of product. However, if the raw material was scrap, the emission factors varied owing to the different contents of organic materials in the raw materials. It was found that the mean WHO-TEQ values of PCDD/Fs and DL-PCBs were 144 and 34.2 pg Nm⁻³ in stack gas and 20.0 and 1.58 pg g⁻¹ in fly ash. In multiple tests, it was estimated that the mean emission factors of PCDD/Fs and DL-PCBs were 365 and 10.9 ng WHO-TEQ t⁻¹ released to residue and 2719 and 555 ng TEQ t⁻¹ released to air. The total emission amounts of PCDD/Fs and DL-PCBs from Chinese iron foundries with cupola furnaces released to residue and air were 16.8 and 146 g WHO-TEQ in 2008, respectively.     

饮用水除砷技术研究进展

饮用水中的砷对人体健康危害很大。介绍了从饮用水中去除砷的各种方法,总结了目前除砷技术存在的不足,指出混凝微滤工艺具有除砷效率高、能耗低、操作简单等优点,应成为今后饮用水除砷技术的发展方向。     

Altered toxicity of organic pollutants in water originated from simultaneous exposure to UV photolysis and CdSe/ZnS quantum dots

The paper reports unforeseen results of increased toxicity of water, subsequent to interactions between CdSe/ZnS quantum dots (QDs), phenol and toluene under UV irradiation. The consistent pattern of changes in measured toxicity (TU) was observed and correlated with degradation of phenol and/or toluene. Spearman rank coefficients (SRCs) for data pairs sum-parameters vs. TU were calculated. The highest correlation between toxicity and degradation by-products was observed for hydroquinone (0.86) and catechol (0.89). The presence of QDs in tested concentration range in the absence of UV has shown low toxicity and no interactions with phenol and/or toluene. The leak of constituent core and shell metal ions was observed. The minor differences in physical characteristics of tested QDs of the same chemical composition led to rather different degradation patterns of phenol and toluene, and the amount of leak of the metal ions as well.     

Nationwide monitoring of atmospheric PCDD/Fs and dioxin-like PCBs in South Korea

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) were measured in ambient air samples collected from different parts of South Korea in 2008, and the measured levels were used for assessing the spatial and temporal distribution of atmospheric PCDDFs and DL-PCBs in South Korea. The average concentrations of atmospheric PCDD/Fs and DL-PCBs among the 37 sites were 28 fg I-TEQ m⁻³ (ND ∼ 617) and 1 fg WHO-TEQ m⁻³ (ND ∼ 0.016). Elevated atmospheric levels of PCDD/Fs and DL-PCBs observed at residential/industrial sites and in the north-west of Korea, indicated a potential contribution and impacts of anthropogenic sources of PCDD/Fs and DL-PCBs. These levels were similar or lower than those previously reported in other ambient air surveys. Average concentrations of PCDD/Fs showed small seasonal variations (ANOVA analysis, p = 0.144). The highest concentrations of PCDD/Fs were observed during winter, followed by spring, autumn and summer. Atmospheric PCDD/Fs and DL-PCBs in South Korea rapidly decreased during the last 10 years (1998-2008), demonstrating the efficiency of stricter regulations and the application of best available technologies/best environmental practices at emission sources. Comparison of the congener profiles and principal component analysis showed that current atmospheric PCDD/Fs are mostly influenced by industrial sources and PCBs from old commercial PCB uses. Nationwide POPs monitoring will continue and allows an effective evaluation of the implementation of the Stockholm Convention on POPs.     

室内空气中颗粒物污染特征研究

为获得室内空气颗粒物污染特征,2009年8月18～24日在某单位工作及生活区选取4个室内点和1个室外点进行颗粒物采样和成分分析.结果表明,室内粗颗粒(PM10)符合<室内空气质量标准>(GB/T 18883-2002),而细粒子(PM2.5)的浓度水平较高,表明室内PM2.5的污染较重;室内与室外PM2.5比值显示,P...     

Emission characterization of unintentionally produced persistent organic pollutants from iron ore sintering process in China

Emission of unintentionally produced persistent organic pollutants (Unintentional POPs), including polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychorinated biphenyls (PCBs), hexachlorobenzene (HxCBz) and pentachlorobenzene (PeCBz), were investigated in four typical iron ore sintering plants in China. The emission factors and annual mass releases of the Unintentional POPs were calculated. The results indicated that PCDFs contributed more than 60% to the overall toxic equivalent quantity (TEQ) values, while the contribution of the dl-PCBs is relatively low, and only in the range of 8-9%. The dominant congeners of PCDD/Fs and dl-PCBs contributing most to the total TEQ were 1,2,3,7,8-PeCDD, 2,3,4,7,8-PeCDF and PCB-126. With regard to the TEQ contributions, the most abundant homologues were PeCDFs and HxCDD/Fs, followed by PeCDDs and non-ortho dl-PCB, whereas HpCDD/Fs, OCDD/Fs and mono-ortho dl-PCBs almost made no contributions. Due to the massive use of recycled waste in the feeding materials, the average emission factor of PCDD/Fs and dl-PCBs of the four plants was 3.95 μg WHO-TEQ ton⁻¹. Based on the results, the annual release of PCDD/Fs and dl-PCBs in 2007-2009 were estimated to be 2070 g, 2212 g, and 2307 g WHO-TEQ, respectively.     

可溶性有机质对芘在泥炭和高岭土上吸附和解吸的影响

为掌握可溶性有机质(DOM)对憎水性有机污染物吸附和解吸行为的影响,本研究选取四环多环芳烃——芘作为目标污染物,通过批平衡实验研究了不同分子量组分DOM对芘在泥炭和高岭土上吸附和解吸的影响.结果表明,吸附和解吸数据均可以用Freundlich模型很好地拟合(R2＞0.93).DOM的添加抑制了泥炭对芘的吸附,并且分子量...     

进水C/N对A~2/O-BCO工艺反硝化除磷特性的影响

采用厌氧/缺氧/好氧与生物接触氧化工艺组成的双污泥系统(A~2/O-BCO)处理实际生活污水.通过投加乙酸钠调节进水碳氮比(C/N=2.44~8.85),考察了系统的反硝化除磷特性.试验结果表明:进水有机物主要是通过改变硝化性能(即缺氧段反硝化负荷)以及聚-β-羟基链烷酸脂(PHA)的贮存和利用,进而影响系统的脱氮除磷效果.当进水C/N为4~5时,COD、TN和PO_4~(3-)-P去除率分别达到88%,80%和96%,实现了有机物、氮和磷的同步高效去除.碳平衡分析表明,A~2/O反应器去除的COD占去除总量的71.86%~77.28%,BCO反应器去除的COD仅占2%~12%,碳源的高效利用是A~2/O-BCO工艺在低C/N条件下实现深度脱氮除磷的重要原因.此外,通过进水C/N与曝气量、硝化液回流比、厌/缺氧反应时间等相关性的分析,提出了系统的优化运行策略.     

Pd/g-C3N4对水中2,4-二氯酚的催化加氢脱氯研究

分别采用光沉积法和浸渍法制备了载钯石墨相氮化碳催化剂(Pd/g-C3N4-PD和Pd/g-C3N4-IMP),并对其进行了电感耦合等离子体发射光谱(ICP-AES)、X射线衍射(XRD)、透射电镜(TEM)和Zeta电位的表征.结果表明,不同载钯量Pd/g-C3N4-PD的等电点均在pH 2.3左右;Pd/g-C3N4-PD表面Pd粒子分散均匀,且Pd粒径小于Pd/g-C3N4-IMP.分别将Pd/g-C3N4-PD和Pd/g-C3N4-IMP用于2,4-二氯酚的催化加氢脱氯研究,Pd/g-C3N4-PD的催化脱氯效果明显优于Pd/g-C3N4-IMP.低pH值利于2,4-二氯酚的催化加氢脱氯过程,但不利于保持催化剂的稳定性.     

厨余发酵液作为中试A/O-MBR外增碳源的脱氮特性

利用厨余发酵液作为A/O-MBR的外增碳源,考察在不同发酵液投加量和水力停留时间(HRT)条件下的脱氮性能以及膜污染特点.结果表明,发酵液的反硝化速率和COD利用率与乙酸钠接近,比葡萄糖高.通过A/O-MBR的运行发现,厨余发酵液作为碳源能够增强微生物活性,强化反硝化过程,从而提高脱氮效率.TN的去除效率随着发酵液投加量的增加而增大.发酵液投加前后,反应器内的EPS并没有积累,膜污染速率变化较小.化学清洗可以有效地去除膜污染物质,恢复膜通量.同时,延长HRT有助于提高脱氮效率和缓解膜污染.