Removal mechanism of Microcystis aeruginosa in Fe2+/sodium percarbonate and Fe2+/sodium persulfate advanced oxidation-flocculation system.

Advanced oxidation process (AOPs) can be used for the treatment of harmful algal blooms (HABs). In this study, two systems of Fe2+/sodium percarbonate (Fe2+/SPC system) and Fe2+/sodium persulfate (Fe2+/PS system) were established to explore the removal mechanism of Microcystis aeruginosa (M. aeruginosa). The results indicated that the Fe2+/SPC system catalyzed H2O2 to generate a large amount of [Formula: see text] for oxidation by Fe2+ and formed Fe3+ to promote the flocculation of M. aeruginosa. The persulfate was activated by Fe2+ to generate [Formula: see text] with super-oxidizing properties, and Fe3+ was generated to realize the oxidation and flocculation of M. aeruginosa in the Fe2+/PS system. Compared with the traditional method in which the pre-oxidation and flocculation processes are carried out separately, the method in this study effectively improves the utilization rate of the flocculant and the removal effect of M. aeruginosa. The absolute value of zeta potential of Fe2+/PS system (|ζ|= 0.808 mV) was significantly lower than that of Fe2+/SPC system (|ζ|= 21.4 mV) (P < 0.05), which indicated that Fe2+/PS system was more favorable for the flocculation of M. aeruginosa cells than the Fe2+/SPC system.

Algal-bacterial consortium mediated system offers effective removal of nitrogen nutrients and antibiotic resistance genes.

The sulfonamide antibiotic resistance genes (ARGs) especially sul1 was identified as the dominant in eutrophic water. The performance of Chlorella vulgaris-B. licheniformis consortium toward sul1 removal, total nitrogen (TN) removal, and the mechanism of sul1 removal was investigated. The removal efficiency of exogenous ARGs plasmids carrying sul1 reached (97.2 ± 2.3)%. The TN removal rate reached (98.5 ± 1.2)%. The enhancements of carbon metabolism, nitrogen metabolism, aminoacyl-tRNA biosynthesis, and glycoproteins had significant influences on sul1 and TN removals, under the premise of normal growth of algae and bacteria. The quantitative polymerase chain reaction (qPCR) results suggested that the absolute abundances of sul1 were low in algal-bacterial systems (0 gene copies/mL) compared with individual systems ((1 × 106 ± 15) gene copies/mL). The duplication of sul1 was inhibited in algal cells and bacterial cells. The algal-bacterial consortium seems to be a promising technology for wastewater treatment with a potential to overcome the eutrophication and ARGs challenges.

Mechanism of enhanced production of triterpenoids in algal-fungal consortium.

Chlorella pyrenoidosa-Ganoderma lucidum symbiotic systems were constructed. The mechanism of enhanced production of triterpenoids in algal-fungal consortium by comparing the contents of triterpenoids in individual fungal systems and algal-fungal consortium systems was investigated. The production of triterpenoids in C. pyrenoidosa-G. lucidum consortium increased significantly (P < 0.05). The categories and relative abundances of metabolites in the individual systems and algal-fungal systems were measured and analyzed by metabonomic tests. There were 57 significant different metabolites (VIP > 1 and P < 0.05) including 12 downregulated metabolites and 45 upregulated metabolites were obtained. The significant enriched metabolic pathways (VIP > 1 and P < 0.05) of citrate cycle (TCA cycle), tyrosine metabolism, glycolysis, and terpenoid backbone biosynthesis in algal-fungal consortium were obtained. The relative abundances of important precursors of triterpenoids including mevalonic acid, lanosterol, and hydroquinone were 1.4 times, 1.7 times, and 2 times, respectively, in algal-fungal consortium than that in the individual fungal systems. The presence of C. pyrenoidosa in algal-fungal consortium promoted the biosynthesis of triterpenoids in G. lucidum.

Research progress of advanced oxidation technology for the removal of Microcystis aeruginosa: a review.

In recent years, cyanobacteria blooms have continued to erupt frequently, seriously jeopardizing the safety of drinking water and human health. The safe, quick, and economical removal of cyanobacteria from water bodies, especially the dominant species of cyanobacteria, Microcystis aeruginosa, has captured a lot of scientists' attention. The application of advanced oxidation technology in water treatment is very promising, but it has not yet been used in production. To further promote the application of the advanced oxidation method in water treatment, this article combines the results of advanced research in China and abroad to review this emergent technology. Briefly, advanced oxidation process methods employ various mechanisms to remove the dominant species of cyanobacteria blooms Microcystis aeruginosa. This provides a theoretical reference and support for the efficient removal of harmful cyanobacteria from water.

The hormetic effect of cadmium on the activity of antioxidant enzymes in the earthworm Eisenia fetida.

The hormetic dose-response relationships induced by environmental toxic agents are often characterized by low-dose stimulation and high-dose inhibition. Confirmation of the general phenomenon of hormesis may have significant implications for ecological risk assessment, although the mechanisms that underlie hormesis remain an enigma. In this study, a model-based approach for describing a dose-response relationship incorporating the hormetic effect was applied to the detection and estimation of the hormetic effect of cadmium (Cd) on the activity of antioxidant enzymes in the earthworm Eisenia fetida. The results showed that Cd at low concentrations induced an increase in the activity of catalase and superoxide dismutase (SOD), but high concentrations inhibited the enzymes, and this was reflected in an inverted U-shaped curve. The maximum hormetic magnitude of SOD activity was higher than that of catalase. The presence of hormesis induced by cadmium in the earthworm may be related to activation of adaptive pathways.

Changes in levels of juvenile hormone and molting hormone in larvae and adult females of Chilo suppressalis (Lepidoptera: Pyralidae) after imidacloprid applications to rice.

Insect hormones regulate growth and development and fecundity of insects. The current study investigated changes in juvenile hormone (JH) and molting hormone (MH) levels in fourth instars and adult females of Chilo suppressalis (Walker) (Lepidoptera: Pyralidae) after imidacloprid application to rice, Oryza sativa L. The results showed that JH level in fourth instars that developed feeding on Fengyouxiangzhan rice plants sprayed with 15, 30, and 60 ppm imidacloprid was significantly higher than that of larvae that developed on control plants, increasing by 5.04, 6.39, and 4.89 times, respectively. The relationships between JH level and imidacloprid concentrations showed a significant negative correlation. In contrast, molting hormone (MH) level in larvae fed on control plants was significantly higher than that on treated plants. JH:MH values in fourth instars developed from larvae feeding on rice plants treated with 15, 30, 60, 80, and 100 ppm imidacloprid increased by 49.17, 39.43, 13.48, 15.80, and 0.2 times, respectively, compared with control. JH and JH:MH ratio in larvae fed on Wujing 15 plants treated with imidacloprid were significantly lower than those fed on Fengyouxiangzhan under the same treatments. JH level in adult females that developed from larvae feeding on rice plants sprayed with imidacloprid significantly decreased with increase in imidacloprid concentration, but it increased compared with control. JH level in adult females was associated with times of imidacloprid application. JH level in adult females developed from larvae feeding on rice plants after double spray with 30 ppm imidacloprid was significantly higher than control, increasing by 61.6 and 116.5%, respectively, compared with a single spray and the control. Moreover, hormone levels in the larvae were related to the application method of imidacloprid. JH level in fourth instars after root application and topical application of imidacloprid was significantly lower than in control. Thus, the dynamics of JH and MH in insects after insecticide applications are an extremely interesting problem, because hormones are related to insect growth and development.

Distribution of imidacloprid residues in different parts of rice plants and its effect on larvae and adult females of Chilo suppressalis (Lepidoptera: Pyralidae).

The distribution of imidacloprid residue in different parts of rice, Oryza sativa L. (Graminales: Poaceae), plants was investigated for three rice varieties. Changes in larval hormones in Chilo suppressalis (Walker) (Lepidoptera: Pyralidae) that fed on imidacloprid-treated plant sources and the fecundity of resultant adult females (moths) also were determined. No significant differences in imidacloprid residue were detected in rice stem, leaves, and the unexpanded new leaf 7 d after treatment except in the rice variety Fengyouxiangzhan, in which residue content in leaves and the unexpanded new leaf was significantly lower than that in the stem. The percentage of reduction of imidacloprid residue after treatment varied with rice variety and plant parts. The greatest reduction in the three plant parts was shown in Wujing 15 compared with the other two varieties. The decomposition rate of imidacloprid residue in Wujing 15 was greater in leaves and unexpanded new leaf than in the stem, whereas in Wuyunjing 7 it was lower in leaves than in the unexpanded new leaf and stem. In Fengyouxiangzhan, the decomposition rate of imidacloprid in the stem increased 14 d after treatment. Juvenile hormone III and molting hormone titers in fourth instar larvae that had fed on rice plants treated with imidacloprid since the neonate stage were significantly higher than those in larvae fed on untreated plants (control). Juvenile hormone titer in larvae that had fed on Zizamia lalifolia Turcz galls treated with imidacloprid and the fecundity of the female moths that developed from such larvae were also significantly higher than that on the control counterparts. These results are discussed in relation to the impact of imidacloprid on nontarget insects and pest management.

Selective insecticide-induced stimulation on fecundity and biochemical changes in Tryporyza incertulas (Lepidoptera: Pyralidae).

The use of selective insecticides in rice, Oryza sativa L., fields often causes resurgence of nontarget pest insects. This study was conducted to investigate the effect of two selective insecticides, buprofezin and imidacloprid, on Tryporyza incertulas (Walker), a nontarget pest. After larval feeding on rice plants treated with each insecticide, fecundity, ovary protein content, and titer of juvenile hormone III (JHIII) in the resulting female moths were determined with 'Xiushui 63' rice susceptible to T. incertulas and 'Zhendao 2' moderately resistant to T. incertulas. The fecundity of females developed from larvae that fed on the insecticide-treated Xiushui 63 plants was stimulated compared with that of moths from larvae that fed on rice plants that were not treated with either insecticide. There was no stimulating effect in females from larvae that fed on insecticide-treated Zhendao 2 plants. The weight of fourth instars (final instars) that fed on the insecticide-treated Xiushui 63 rice plants was significantly greater than that of control, increasing by 50.3 and 46.7% for 60 and 112.5 g (AI) ha(-1) buprofezin, and by 23.7 and 19.5% for 15 and 37.5 g (AI) ha(-1) imidacloprid treatments, respectively. Ovary protein content in adult females developed from larvae that fed on the rice treated with the high dose of buprofezin was significantly higher than that in control. For the high and low doses of imidacloprid during the second instar, and the low dose of imidacloprid during the fourth instar, JHIII titers in female adults were also significantly higher than that in control, increasing by 152.81, 90.52, and 114.19%, respectively.

[Response of parasitic wasps of cotton bollworm to different cotton varieties with transgenic Bacillus thringienthsis genes].

The relationship between the parasitic wasp population number of cotton bollworm (Helicoverpa armigera) and the varieties of cotton was studied by releasing and collecting the eggs and larvae of cotton bollworm on transgenic and non-transgenic cottons. The research results from 2000 to 2003 showed that the parasitic rates of the eggs and larvae of cotton bollworm were notably lower in transgenic cotton field than in non-transgenic cotton field. At the same time, the effect of transgenic and non-transgenic cottons on the selection behavior of the parasitic wasp Microplitis mediatar of the larvae of cotton bollworm was studied by using "Y" olfactometer. The results showed that the selection response about the parasitic wasp Microplitis mediatar of cotton bollworm on non-transgenic cotton was prior to the transgenic cotton.