The evaluation of heavy metal accumulation and application of a comprehensive bio-concentration index for woody species on contaminated sites in Hunan,China

Fast-growing metal-accumulating woody plants are considered potential candidates for phytoextraction of metals. Shuikoushan mining, one of the biggest Pb and Zn production bases in China, presents an important source of the pollution of environment during the last 100 years. Over 150 km² of fertile soil have been contaminated by the dust, slag, and tailings from this mining. The goal of the present work has been to determine the content of Pb, Zn, Cd, and Cu in wild woody plants (18 species) naturally growing in this area. Two hundred five plant and soil samples from 11 contaminated sites were collected and analyzed. In addition, to assess the ability of multi-metal accumulation of these trees, we proposed a predictive comprehensive bio-concentration index (CBCI) based on fuzzy synthetic assessment. Our data suggest some adult trees could also accumulate a large amount of metals. Pb concentrations in leaves of Paulownia fortunei (Seem.) Hemsl. (1,179 mg/kg) exceeded the hyperaccumulation threshold (1,000 mg/kg). Elevated Pb concentrations (973.38 mg/kg) were also found in the leaves of Broussonetia papyrifera (L.) Vent., with a Pb bio-concentration factor of up to 0.701. Endemic species, Zenia insignis Chun exhibited huge potential for Zn and Cd phytoextraction, with the highest concentrations of Zn (1,968 mg/kg) and Cd (44.40 mg/kg), characteristic root nodules, and fast growth rates in poor soils. As for multi-metal accumulation ability, native species B. papyrifera was calculated to have the most exceptional ability to accumulate various metals simultaneously (CBCI 2.93), followed by Amorpha fruticosa L. (CBCI 2.72) and Lagerstroemia indica L. (CBCI 2.53). A trend of increasing metal from trunks to leaves (trunks?<?branches?<?leaves) and towards fine roots has been shown by metal partitioning between tissues. The proposed CBCI would allow for the selection of suitable trees for phytoremediation in the future.     

Neurotoxicological evaluation of microcystin-LR exposure at environmental relevant concentrations on nematode Caenorhabditis elegans

Previous studies have not examined the adverse effects of microcystin-LR (MC-LR) at environmental relevant concentrations on the development and functions of nervous system. The neurotoxic effects of MC-LR exposure on neurotransmitter systems were investigated in Caenorhabditis elegans. After exposing L1 larvae to 0.1, 1, 10, and 100 μg?l^?1 of MC-LR for 8 and 24 h, the adverse effects on GABAergic, cholinergic, serotonergic, dopaminergic, and glutamatergic neurons were examined. The expression levels of genes required for development and functions of GABAergic neurons were further investigated. Body bend frequency and head thrash frequency decreased significantly after MC-LR exposure for 8 h at concentrations more than 1 μg?l^?1 and after MC-LR exposure for 24 h at concentrations more than 0.1 μg?l^?1. Loss of GABAergic neurons increased significantly in a dose-dependent manner after MC-LR exposure at concentrations more than 0.1 μg?l^?1. In contrast, no obvious neuronal losses or morphologic changes were observed in cholinergic, serotonergic, dopaminergic, and glutamatergic neurons in MC-LR-exposed nematodes. Quantitative real-time PCR assay further showed that expression levels of unc-30, unc-46, unc-47, and exp-1 genes required for development and function of GABAergic neurons decreased significantly in nematodes exposed to MC-LR at concentrations more than 0.1 or 1 μg?l^?1. MC-LR at environmental relevant concentrations caused neurobehavioral defects, which may be largely due to the neuronal loss and the alterations of expression level of genes required for GABAergic neurotransmitter system in C. elegans.     

The response of mulberry trees after seedling hardening to summer drought in the hydro-fluctuation belt of Three Gorges Reservoir Areas

Interest has developed in the potential of mulberry (Morus alba), a woody perennial, for revegetating the hydro-fluctuation belt of the Three Gorges Reservoir due to its resistance to water-logging stress. To be useful, the trees must also be able to withstand dry conditions in summer when temperatures can be very high and droughts become severe quickly. Here, we report a study in which mulberry seedlings were grown in a greenhouse under a variety of simulated soil water conditions reflecting potential summer scenarios in the hydro-fluctuation belt of the Three Gorges Reservoir Area. We compared the responses of two pretreatment groups of mulberry seedlings to different levels of drought stress. The pretreatment groups differed with respect to drought hardening: the daily-managed (DM) group had relative soil moisture held constant in the range 70–80 %, while the drought-hardened (DH) group had relative soil moisture held constant at 40–50 %. Following the month-long pretreatment of seedlings, the two groups of young trees (DM and DH) were then respectively subjected to three levels of drought stress for a month: normal watering, moderate drought stress, and severe drought stress. A series of measurements comparing the physiological status of the plants in the two groups were then made, and the following results were obtained: (1) As drought stress increased, the heights, base diameters, root surface areas, photosynthetic rates (Pn), stomatal conductances (Gs), and transpiration rates (Tr) of the mulberry trees in both groups (DM and DH) decreased significantly, while the specific root area and abscisic acid (ABA) contents had increasing trends. Root activity and instantaneous water use efficiency of mulberry trees in both groups (DM and DH) were all raised under drought stress conditions than under normal watering, but the root/shoot ratio and leaf water potential were lowered. (2) At the same level of soil water content, the heights, base diameters, root/shoot ratios, root surface areas, specific root areas, photosynthetic rates (Pn), stomatal conductances (Gs), and transpiration rates (Tr) of the young mulberry trees in the DH were all significantly higher than those of the control group (DM). Leaf water potential, instantaneous water use efficiency, and abscisic acid content of DH were all significantly lower than DM. Under different degrees of drought stress, the growth of mulberry trees will be inhibited, but the trees can respond to the stress by increasing the root absorptive area and enhancing capacity for water retention. Mulberry trees demonstrate strong resistance to drought stress, and furthermore drought resistance can be improved by drought hardening during the seedling stage.     

A^2O工艺中雌激素的行为变化和去除机理

研究了厌氧-缺氧-好氧（A2O）活性污泥工艺对生活污水中天然雌激素雌酮（Estrone,E1）、17β-雌二醇（17β-Estradiol,E2）以及17α-乙炔基雌二醇（17α-Ethynylestradiol,EE2）的去除性能。在对COD、N和P具有良好去除效果的前提下,对E1、E2和EE2的去除率可分别达到92.7%、100%和62.7%。通过对各反应单元内3种雌激素的物料平衡分析,表明A2O工艺对雌激素的去除主要发生在厌氧段和好氧段。以失活污泥作为对照组,好氧硝化过程中雌激素去除的小试实验发现,好氧过程中E1、E2的去除主要依靠生物降解作用,而EE2的去除则主要依赖于活性污泥对其的吸附作用。     

简青霉降解秸秆条件最优化和诱导剂的作用

实验中采用简青霉对稻草秸秆进行降解作用,通过正交实验的极差、三因素三水平作用趋势图和降解选择性分析,对影响简青霉降解稻草秸秆的3种因素进行了优化,得到培养温度40℃、含水率80%、培养pH为8是降解的最佳固态发酵培养条件。并研究了碱木质素对简青霉分泌木质素降解酶的诱导作用,不同浓度的碱木质素对简青霉产酶的诱导作用不同,且对不同酶的诱导效果也不同,最后得到较低浓度0.5和1 g/L是诱导的适宜浓度。对比较适浓度的碱木质素和常用的诱导剂愈创木酚、吐温80的诱导作用,发现在同样的培养条件下,碱木质素的诱导效果比愈创木酚和吐温80效果都好。     

烟气脱硫新型催化剂水洗再生工艺研究

对脱硫失活后的新型催化剂进行水洗再生研究,着重探讨了再生时间、洗涤水温度和喷淋密度对脱硫后的新型催化剂活性恢复能力的影响,并对3种影响因素进行了正交实验研究。结果表明,洗涤水温度、再生时间和喷淋密度是影响催化剂活性恢复的主要因素;在洗涤水温度为60℃、再生时间为30min、喷淋密度为47．9m^3／（m·h）时,催化剂活性恢复的最好;催化剂经过水洗再生后,其比表面积比未再生时的有所增加,说明在脱硫过程中堵塞催化剂活性位的硫酸物种被洗出,催化剂活性位得到了部分恢复。     

还原焙烧电镀污泥中的金属形态和浸出性

分别以煤粉和稻杆为还原剂对电镀污泥进行还原焙烧,并通过酸浸回收焙烧渣中的金属。研究了焙烧温度、焙烧时间和还原剂投加量对目标金属Cu浸出率的影响以及主要杂质金属的浸出性,并采用BCR逐级提取法分析了焙烧前后污泥中的金属形态分布。结果表明,当在电镀污泥中投加30％的煤粉在600℃下焙烧1h后Cu的浸出率达到97．78％,当投加50％的稻杆时浸出率为89．47％,而氧化焙烧后浸出率仅为37．71％;并且还原焙烧渣中多数杂质金属的浸出率较低,从而可以实现Cu与杂质金属的初步分离。氧化焙烧容易导致金属从易浸出的非残渣态向难浸出的残渣态转化,而还原焙烧则能抑制这种转化过程,金属形态是决定其浸出性的重要因素。     

微波辅助疏水膜的清洗

针对膜蒸馏过程中膜表面常见的CaSO4垢和腐殖酸混合垢,对微波强化疏水膜清洗的效果进行了研究。结果表明,对于膜表面的CaSO4垢,微波辅助清洗效率高于常规清洗,且在清洗液的温度和流速较低时,微波的强化清洗效果更为明显;对于膜表面的腐殖酸混合垢,微波辅助清洗后的初始通量恢复率为88.4%,比常规清洗高出10.8%,同时可以相对缓解疏水膜的亲水化。     

污泥活性炭对次甲基蓝废水的吸附

立足于污泥的资源化,利用化学活化法制得的污泥基活性炭,处理次甲基蓝染料废水.考察了污泥活性炭的粒径以及染料废水的pH值对染料脱色效果以及活性炭的吸附量的影响,并对吸附过程进行等温吸附线和吸附动力学分析.结果表明,在本研究的范围内,污泥活性炭的粒径越小、染料废水的pH值越高,则污泥活性炭对染料废水的吸附效果越好.当粒径在200目以上时,去除率及吸附量分别为88.2％和136.7 mg/g;当pH值为11时,去除率和吸附量分别为90.4％和91.9 mg/g.污泥活性炭对次甲基蓝染料的吸附脱除符合Langmuir吸附等温线和Lagergren准二级动力学方程.     

生物降解实验中的接种物标准化研究

针对降解实验中接种物采集困难、活性差异大、实验可重复性及结果可比性差的问题展开接种物标准化研究。对多来源的接种物在实验室可控条件下进行驯养,驯养后生长状态良好的活性污泥分别固定于灭菌麸皮和藻酸钙凝胶等2种微生物载体上,形成2种固定化接种物(分别简称为Bran及Ball)。对上述固定化接种物进行微生物活性、适应性、降解能力以及稳定性研究:通过2种固定化接种物与商品化接种物Polyseed对葡萄糖-谷氨酸(GGA)五日生化需氧量(BOD5)的结果与活菌细胞数的关系,确认3种接种物在降解实验中的用量可控制在相同数量级;比较不同批次及保存时间的2种固定化接种物、相同批次不同保存时间的Polyseed以及污水处理厂曝气池污泥为接种物对苯胺及二甘醇的快速生物降解实验(OECD301F)结果,发现Ball及Bran较Polyseed及新鲜采集活性污泥的微生物适应性及降解能力更佳。此外,在较长保存期内2种固定化接种物活性相对稳定。2种固定化接种物初具成为标准化接种物的必要条件。