Toxicological characterization of the landfill leachate prior/after chemical and electrochemical treatment: A study on human and plant cells

In this research, toxicological safety of two newly developed methods for the treatment of landfill leachate from the Piškornica (Croatia) sanitary landfill was investigated. Chemical treatment procedure combined chemical precipitation with CaO followed by coagulation with ferric chloride and final adsorption by clinoptilolite. Electrochemical treatment approach included pretreatment with ozone followed by electrooxidation/electrocoagulation and final polishing by microwave irradiation. Cell viability of untreated/treated landfill leachate was examined using fluorescence microscopy. Cytotoxic effect of the original leachate was obtained for both exposure periods (4 and 24 h) while treated samples showed no cytotoxic effect even after prolonged exposure time. The potential DNA damage of the untreated/treated landfill leachate was evaluated by the comet assay and cytokinesis-block micronucleus (CBMN) assay using either human or plant cells. The original leachate exhibited significantly higher comet assay parameters compared to negative control after 24 h exposure. On the contrary, there was no significant difference between negative control and chemically/electrochemically treated leachate for any of the parameters tested. There was also no significant increase in either CBMN assay parameter compared to the negative control following the exposure of the lymphocytes to the chemically or electrochemically treated landfill leachate for both exposure periods while the original sample showed significantly higher number of micronuclei, nucleoplasmic bridges and nuclear buds for both exposure times. Results suggest that both methods are suitable for the treatment of such complex waste effluent due to high removal efficiency of all measured parameters and toxicological safety of the treated effluent.     

Impact of nano-CuO stress on rice (Oryza sativa L.) seedlings

Indiscriminate release of metal oxide nanoparticles (NPs) into the environment due to anthropogenic activities has become a serious threat to the ecological system including plants. The present study assesses the toxicity of nano-CuO on rice (Oryza sativa cv. Swarna) seedlings. Three different levels of stress (0.5 mM, 1.0 mM and 1.5 mM suspensions of copper II oxide, <50 nm particle size) were imposed and seedling growth performance was studied along control at 7 and 14 d of experiment. Modulation of ascorbate–glutathione cycle, membrane damage, in vivo ROS detection, foliar H₂O₂ and proline accumulation under nano-CuO stress were investigated in detail to get an overview of nano-stress response of rice. Seed germination percentage was significantly reduced under stress. Higher uptake of Evans blue by nano-CuO stressed roots over control indicates loss of root cells viability. Presence of dark blue and deep brown spots on leaves evident after histochemical staining with NBT and DAB respectively indicate severe oxidative burst under nano-copper stress. APX activity was found to be significantly increased in 1.0 and 1.5 mM CuO treatments. Nevertheless, elevated APX activity might be insufficient to scavenge all H₂O₂ produced in excess under nano-CuO stress. That may be the reason why stressed leaves accumulated significantly higher H₂O₂ instead of having enhanced APX activity. In addition, increased GR activity coupled with isolated increase in GSH/GSSG ratio does not seem to prevent cells from oxidative damages, as evident from higher MDA level in leaves of nano-CuO stressed seedlings over control. Enhanced proline accumulation also does not give much protection against nano-CuO stress. Decline in carotenoids level might be another determining factor of meager performance of rice seedlings in combating nano-CuO stress induced oxidative damages.     

pH对活化前后废弃铁铝泥吸附不同种磷动力学的影响

实验研究了300℃热活化前后的给水厂废弃铁铝泥（R-FARs和H300-FARs）对正磷酸盐、聚磷酸盐和有机磷酸盐的吸附动力学特性,并考察pH对不同磷吸附动力学的影响。结果表明,pH对不同磷吸附动力学过程的影响趋势相似,即低pH有利于吸附。准二级动力学模型能够更真实地反映不同磷在R-FARs和H300-FARs的吸附动力学行为,由拟合结果可知焦磷酸盐和六肌醇磷酸盐的初始吸附速率相对较大,而甘油磷酸盐最小;且活化作用明显提高了不同磷的初始吸附速率,并减弱了pH对初始吸附速率的影响。不同磷的吸附速率受到液膜扩散、颗粒内扩散和吸附反应三者共同控制,其中吸附反应是主要的控制步骤。     

高碱度水库水混凝过程中残留铝控制

针对高碱度水库水源的某水厂残留铝超标问题,选取碱化度(B)与Alb含量不同的3种铝盐絮凝剂,研究不同投量与pH值下混凝效果与残留铝浓度水平。结果表明,碱化度和Alb含量显著影响混凝效果。DOC和浊度的去除率随着3种絮凝剂AlCl3(B=0)、PACl-1(B=1.2)、PACl-2(B=2.2)投量增大而升高。3种絮凝剂投量在1.5～2.0 mg/L(以铝计)范围内,总铝和溶解铝含量最低。对于该水厂自制的絮凝剂PACl-2,可通过降低絮凝剂碱化度,或将水的pH值降低至7～7.5之间,以此可以提高PACl-2混凝效果,而且可以降低出厂水残留铝浓度。考虑工程应用可行性,可优先考虑调整絮凝剂生产工艺。     

Hydroxytyrosol, the phenolic compound of olive oil protects human PBMC against oxidative stress and DNA damage mediated by 2,3,7,8-TCDD

The protective effect of hydroxytyrosol (HT), a strong antioxidant compound from extra virgin olive oil, against TCDD induced toxicity was investigated in human peripheral blood mononuclear cells (PBMC). PBMC (1 × 10⁶ cells mL⁻¹) were divided into four groups and were incubated in a CO₂ incubator (5% CO₂) for 12 h with vehicle, TCDD (10 nM), TCDD + HT (10 nM + 100 μM) and HT alone (100 μM) respectively. To clarify the role of HT against TCDD induced cytotoxicity, oxidative stress and the levels of antioxidant enzymes were assessed. Incubation of PBMC with TCDD significantly decreased cell viability, catalase (CAT) and glutathione peroxidase (GPx) and increased the levels of superoxide dismutase (SOD), glutathione reductase (GR) and oxidative stress markers such as lipid peroxidation products (LPO), protein carbonyl content (PCC) and reactive oxygen species (ROS). Whereas, HT had an effective antioxidant property as observed by the increased cell viability, normalization of antioxidant enzymes and decreased levels of LPO, PCC and ROS in PBMC co-treated with HT and TCDD. Apoptosis detection and comet assay results shows that HT, by acting as an antioxidant, prevents the damage to DNA induced by TCDD. In addition light microscopic and histopathological observations revealed that the cells are apoptotic and degenerated during TCDD treatment, whereas cells showed intact morphology during co-treatment with HT. On the whole, the results reveal that HT exerts a promising antioxidant potential in protecting the PBMC against TCDD induced oxidative stress, which might be due to the presence of catechol moiety in its structure.     

Integrated biological responses of zebrafish (Danio rerio) to analyze water quality in regions under anthropogenic influence

This study analyzed water quality in regions around Patos lagoon (Southern Brazil) that are under anthropogenic pressure. Water samples were collected from five different sites, including one used as a source for human consumption (COR) and others known to be influenced by human activities (IP). Danio rerio (Teleostei, Cyprinidae) organisms were exposed for 24 h to these water samples, plus a control group. It was observed that: (1) reactive oxygen species levels were lower in COR and IP than in the control group; (2) glutamate-cysteine ligase (catalytic subunit) expression was higher in COR than in other sites; (3) exposure to all water samples affected long-term memory (LTM) when compared to control group. Thus, some water samples possess the ability to modulate the antioxidant system and to induce a decline in cognitive functions, as measured by LTM. The obtained results indicate that a combination of variables of different organization level (molecular, biochemical and behavioral) can be employed to analyze water quality in impacted regions.     

Acetylcholinesterase activity in the terrestrial snail Xeropicta derbentina transplanted in apple orchards with different pesticide management strategies

Apple orchards are highly manipulated crops in which large amounts of pesticides are used. Some of these pesticides lack target specificity and can cause adverse effects in non-target organisms. In order to evaluate the environmental risk of these products, the use of transplanted sentinel organisms avoids side-effects from past events and facilitate comparison of multiple sites in a short time. We released specimens of the terrestrial snail Xeropicta derbentina in each 5 of two kinds of apple orchards with either conventional or organic management strategies plus in a single abandoned orchard. After one month, individuals were retrieved in order to measure acetylcholinesterase (AChE) activity. Mean values of AChE activity were significantly reduced in all conventional apple orchards compared to the others. Results show that the measurement of biomarkers such as AChE inhibition in transplated X. derbentina could be useful in the environmental risk assessment of post-authorized pesticides.