Nonideal transport of contaminants in heterogeneous porous media: 10. Impact of co-solutes on sorption by porous media with low organic-carbon contents

The impact of co-solutes on sorption of tetrachloroethene (PCE) by two porous media with low organic-carbon contents was examined by conducting batch experiments. The two media (Borden and Eustis) have similar physical properties, but significantly different organic-carbon (OC) contents. Sorption of PCE was nonlinear for both media, and well-described by the Freundlich equation. For the Borden aquifer material (OC = 0.03%), the isotherms measured with a suite of co-solutes present (1,2-dichlorobenzene, bromoform, carbon tetrachloride, and hexachloroethane) were identical to the isotherms measured for PCE alone. These results indicate that there was no measurable impact of the co-solutes on PCE sorption for this system. In contrast to the Borden results, there was a measurable reduction in sorption of PCE by the Eustis soil (OC = 0.38%) in the presence of the co-solutes. The organic-carbon fractions of both media contain hard-carbon components, which have been associated with the manifestation of nonideal sorption phenomena. The disparity in results observed for the two media may relate to relative differences in the magnitude and geochemical nature of these hard-carbon components.     

Chlorinated and brominated organic contaminants in fish from Shanghai markets: a case study of human exposure

In the present study were two favorite edible fish species for local residents, i.e., mandarin fish and crawfish, collected from the Shanghai market and analyzed for selected organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), hexabromocyclododecane (HBCDD), polybrominated diphenyl ethers (PBDEs) and methoxylated PBDEs (MeO-PBDEs). Efforts were also made to identify the potential sources of these contaminants. Comparable concentrations of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs) and HBCDD were found in muscle tissue of mandarin fish from Guangdong (GDF), the Pearl River Delta and from Taihu Lake (TLF), the Yangtze River Delta. Levels of chlordanes, PCBs and PBDEs were about one magnitude lower in TLF compared to GDF. The concentrations of OCPs in the butter-like gland of the crawfish (CFB) were 2-5 times of those in the crawfish muscle (CFM) while concentrations of PCBs, PBDEs and MeO-PBDEs were comparable. The different patterns and levels of chlorinated and brominated organohalogen contaminants seen in mandarin fish from GDF and TLF indicates that different types of chemicals might be used in the two delta regions. The present study also shows a good correlation between the concentrations of hexachlorobenzene (HCB) and pentachloroanisol (PCA) in fish for the first time. Fish consumption limits based on chemical contaminants with non-carcinogenic effects were calculated. The estimated maximum daily consumption limit for GDF, TLF, CFM and CFB were 1.5, 2.6, 3.7 and 0.08 kg, respectively, indicating no significant risk regarding the persistent organic pollutants measured in the present study.     

Dioxin-like activity in environmental and human samples from Greenland and Denmark

Dioxins and dioxin-like (DL) compounds are some of the most toxic chemicals being highly persistent in the environment. The toxicological effects of dioxins are mediated via the aryl hydrocarbon receptor (AhR). Compounds of diverse structure and lipophility can bind and activate AhR. The AhR transactivation bioassay is utilized in an array of projects to study the AhR-mediated activities of individual chemicals and mixtures and for epidemiological purposes.This review summarizes a series of studies regarding the DL-activity of single compounds and complex compound mixtures in the environment and humans.We found that some pesticides, plasticizers and phytoestrogens can activate the AhR, and the combined effect of compounds with no or weak AhR potency cannot be ignored.The significant DL-activity in the wastewater effluent indicates the treatment is not sufficient to prevent contamination of surface waters with dioxins. Our results from human studies suggest that the serum DL-activity reflect the complex mixture of persistent organic pollutants (POPs). Greenlandic Inuit had lower serum DL-activity level compared to Europeans, probably due to long distance from the dioxin sources and UV degradation of the high potent dioxin and/or the inhibitory effect of the high level of non-DL POPs. Selective bioaccumulation of PCBs in the food chain may contribute to the negative correlation between serum POPs and DL-activity observed in Greenlandic Inuit.Hence the AhR transactivation bioassay provides a cost-effective and integrated screening tool for measurement of the DL-activity in human, environmental and commercial samples.     

Degradation of paracetamol by advance oxidation processes using modified reticulated vitreous carbon electrodes with TiO2 and CuO/TiO2/Al2O3

The degradation of paracetamol in aqueous solutions in the presence of hydrogen peroxide was carried out by photochemistry, electrolysis and photoelectrolysis using modified 100 pores per inch reticulated vitreous carbon electrodes. The electrodes were coated with catalysts such as TiO₂ and CuO/TiO₂/Al₂O₃ by electrophoresis followed by heat treatment. The results of the electrolysis with bare reticulated vitreous carbon electrodes show that 90% paracetamol degradation occurs in 4 h at 1.3 V vs. SCE, forming intermediates such as benzoquinone and carboxylic acids followed by their complete mineralisation. When the electrolysis was carried out with the modified electrodes such as TiO₂/RVC, 90% degradation was achieved in 2 h while with CuO/TiO₂/Al₂O₃/RVC, 98% degradation took only 1 h. The degradation was also carried out in the presence of UV reaching 95% degradation with TiO₂/RVC/UV and 99% with CuO/TiO₂/Al₂O₃/RVC/UV in 1 h. The reactions were followed by spectroscopy UV-Vis, HPLC and total organic carbon analysis. These studies show that the degradation of paracetamol follows a pseudo-first order reaction kinetics.     

改性多壁碳纳米管对水中Cd~（2＋）的去除

为了增加多壁碳纳米管（multiwall carbon nanotubers,MWNTs）对水中Cd2＋的吸附量,使用混酸对多壁碳纳米管进行氧化处理,采用红外光谱进行结果表征,并探讨了吸附时间、pH值和MWNTs的使用量、Cd2＋的浓度及干扰离子对镉离子吸附的影响。结果表明,吸附时间为1.5 h、pH为5.3、吸附效果最佳,随MWNTs量的增加Cd2＋去除量增加,共存的阳离子会降低对Cd2＋的吸附效果,对Cd2＋的吸附符合Longmuir吸附定律。研究同时表明,pH小于2时Cd2＋能容易从碳纳米管上解吸。初步探讨了Cd2＋吸附机制。     

松树锯末对亚甲基蓝（MB）的吸附研究

采用松树锯末以及改性松树锯末对模拟废水中的亚甲基蓝进行吸附实验研究。研究结果表明,当亚甲基蓝的初始浓度为50 mg/L、pH为6、锯末投加量为1 g/L时,改性前后的锯末对亚甲基蓝的吸附量最大,分别为29.9 mg/g和60.6 mg/g。同时,对改性前后的锯末做了吸附等温线拟合及动力学研究。结果表明,吸附等温线均能很好地符合Langmuir吸附模式,吸附过程符合拟二级动力学方程。     

几种不同处理方法对活性炭表面化学性质的影响

活性炭表面官能团的种类和数量决定了活性炭的表面化学性质,而化学性质决定了活性炭的表面吸附特性。使用5种常见的处理方法处理活性炭,采用Boehm滴定法,XPS对活性炭进行表征,通过单因素实验系统地考察了活性炭表面含氧官能团及碱度随处理条件的变化,同时通过碱度变化讨论了部分处理方法对于原活性炭表面灰分的去除。结果表明:在处理液150 mL、20℃、200 r/min条件下:50 g活性炭经0.01～5 mol/L HCl处理4 h,活性炭表面碱度降低范围63.2%～76.5%,灰分去除效果好,低浓度的盐酸就能达到较好的灰分去除效果,活性炭表面没有形成大量的含氧官能团;在HNO3浓度1～12 mol/L、处理时间1～8 h、活性炭量25～75 g条件下处理后总碱度降低显著,灰分去除效果优于HCl处理,HNO3氧化作用使活性炭表面形成了大量含氧官能团,总酸度、羧基、内酯基、酚羟基含量均相对于原活性炭增加明显;在H2O2质量浓度5%～20%、处理时间0.5～4 h、活性炭量25～75 g条件下处理后碱性灰分去除不好,活性炭表面没有形成大量含氧官能团,H2O2处理引起活性炭表面化学性质变化较小;在NaOH浓度0.1～2 mol/L、处理时间1～8 h、活性炭量25～75 g条件下处理后碱度增加明显,酸度减小明显,羧基、酚羟基含量降低。50 g活性炭在微波功率100～500 W、处理时间2～10 min、载气流量600～1 400 mL/min条件下经微波处理后,微波热效应导致含氧官能团分解,总碱度增加,总酸度下降,羧基含量、内酯基含量降低,酚羟基含量因条件的不同而变现出不同的变化。     

基于人工蜂群算法与BP神经网络的水质评价模型

针对BP网络水质评价模型的不足,引入人工蜂群(ABC)算法,将求解BP神经网络各层权值、阀值的过程转化为蜜蜂寻找最佳蜜源的过程,提出了一种新的结合人工蜂群算法的BP网络水质评价方法(ABC-BP)。并以2000—2006年渭河监测断面的10组实测数据作为测试样本对其水质进行了评价,实验结果表明该方法得到的水质评价结果准确,并具有很强的稳定性和鲁棒性。     

西安市城市主干道路面径流初期冲刷效应

以西安市城市主干道南二环太白路高架桥为路面径流采样区域,采用人工等时间间隔采样方法,在桥梁排水立管对2010年9—11月的3场径流事件进行全程采样,测试径流过程SS、COD、溶解性COD、NH3-N、Pb、溶解性Pb、Zn和溶解性Zn的浓度变化,研究路面径流的初期冲刷效应及其影响因素。结果表明,西安市城市主干道路面径流污染严重,降雨数小时后的末期径流仍具有较高的污染水平;径流过程污染物浓度变化规律与其赋存形态有关,SS、COD、Pb等以颗粒态为主的污染物的浓度随雨强变化剧烈波动,NH3-N、溶解态COD、溶解态Zn等以溶解态为主的污染物浓度变化受雨强影响较小,随径流过程呈逐渐减小趋势;路面径流初期冲刷现象并非普遍存在,与污染物的赋存状态和场次降雨特征密切相关,溶解态污染物易于出现初期冲刷现象,颗粒态污染物是否出现初期冲刷与场次降雨特征有关;测试的3场径流事件初期30%的径流携带的SS、COD、溶解性COD、NH3-N、Pb、Zn和溶解性Zn的负荷占场次径流总负荷的比例分别为21.8%～50.0%、25.5%～49.3%、36.3%～52.6%、52.6%～66.7%、26.8%～45.0%、27.2%～63.4%和36.2%～62.6%,表明仅对初期径流进行治理无法实现对西安市路面径流污染的有效控制。     

椰壳活性炭吸附消除VOCs

对一种椰壳活性炭对甲基丙烯酸甲酯的吸附消除行为进行了研究,重点考察了甲基丙烯酸甲酯的浓度、流速和吸附温度等条件以及水汽存在时对活性炭吸附行为的影响。结果表明,该颗粒活性炭对甲基丙烯酸甲酯有良好的吸附效果,甲基丙烯酸甲酯进口浓度和进气量的改变均会影响吸附饱和时间,导致其增加或减少。通过变温吸附实验确定降低环境温度对其吸附有促进作用。湿度为50%时吸附量相对干气饱和吸附量影响较小,说明该活性炭抗水汽能力较好。经多次重复再生实验,其饱和吸附量未见明显下降。