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991.
The dissipation of carbendazim and chloramphenicol alone and in combination and their effects on soil fungal:bacterial ratios and soil enzyme activities were investigated. The results revealed that carbendazim dissipation was little affected by chloramphenicol, whereas chloramphenicol dissipation was found to be retarded significantly by the presence of carbendazim. The inhibitory effect of carbendazim on the fungal:bacterial ratios was increased by the presence of chloramphenicol, and the inhibitory effect of chloramphenicol on neutral phosphatase was increased by the presence of carbendazim. Carbendazim increased soil catalase and urease activities, but this increase was partially diminished by the presence of chloramphenicol. Little interaction was observed between carbendazim and chloramphenicol with regard to their influence on soil invertase. The results obtained in this study suggest that combinations of fungicides and antibiotics may alter the compounds’ individual behaviors in soil and their effects on soil enzymes. 相似文献
992.
Wang C Xi JY Hu HY Kang IS 《Journal of the Air & Waste Management Association (1995)》2011,61(3):295-301
A new type of a combined ultraviolet (UV)-biofilter system for air pollution control is developed. In this paper, two conceptual mathematical submodels of the UV reactor and standalone biofilter are developed. All model parameters have been determined by independent experiments or have been taken from literature. Results from UV and the standalone biofilter submodels are in a good agreement with experimental data. However, the performance of the combined system has significantly deviated from those of the UV or standalone submodels because of the stimulating effects of UV irradiation products on the subsequent biofilter performance. A modified model that considers the stimulating effects has agreed well with experimental data over a wide range of operating conditions. Further analysis of the primary parametric sensitivity of the model has shown that inlet chlorobenzene concentrations, gas empty-bed residence time in the UV reactor, and light intensity are important operating conditions. 相似文献
993.
994.
青霉菌HHE-P7利用酱油废水产生微生物絮凝剂的研究 总被引:16,自引:0,他引:16
研究了微生物絮凝剂产生菌HHE-P7在酱油废水中产生微生物絮凝剂的絮凝特性。实验表明,酱油废水由于碳源丰富,是一种良好的培养基。HHE-P7菌最佳培养条件为:COD20000mg/L,K2HP041.0g/L,培养3d。最佳絮凝条件为在1L高岭土水中投加10~15mL微生物絮凝剂(MBF7),pH调至9,则絮凝率为90%以上;微生物絮凝荆在水系中主要起吸附架桥的作用。 相似文献
995.
低温等离子体治理H2S污染的实验研究 总被引:3,自引:0,他引:3
低温等离子体技术是一种高效、快速的污染消除技术,国内外都在对其进行广泛而深入的研究。采用脉冲电晕放电等离子体对空气中的硫化氢进行降解研究,探索了、脉冲峰压、脉冲频率、气体流量以及气体初始浓度对净化效果的影响,气体浓度由气相色谱仪测定。结果表明,脉冲电晕放电可以有效消除硫化氢污染,净化率随脉冲峰压和脉冲频率的增加而提高,随气体初始浓度和流量的增加而下降,且在初始浓度360mg/m^2、流量1200mL/min、脉冲峰压30kV、脉冲频率80Hz的条件下,处理后的气体中已检测不到H2S,根据色谱检测限(0.29mg/m^3)计算出的净化率≥99.92%。采用离子色谱对产物进行了定性分析,发现H2S经放电处理后主要产物为SO2和SO3。 相似文献
996.
Say Leong Ong Suhash Kumar Sarkar Lai Yoke Lee Jiang Yong Hu How Yong Ng Mark van Loosdrecht 《Water environment research》2006,78(4):372-380
The effects of formaldehyde on biofilm morphology and biomass activity were investigated in an ultracompact biofilm reactor (UCBR) for carbonaceous wastewater treatment. The wastewater contained a fixed amount of glucose (with a chemical oxygen demand concentration of 600 mg/L) and an increasing concentration of formaldehyde (ranging from 21.4 to 271.1 mg/L). An influent formaldehyde concentration higher than 75 mg/L could facilitate filamentous growth (on biofilm) control and lead to a higher biofilm density, which is desirable as it enhanced the UCBR performance stability. However, at an influent formaldehyde concentration higher than 214.4 mg/L, biomass production was inhibited and deteriorations of biofilm morphology and biomass activity were observed. This study showed that it was desirable to maintain an influent formaldehyde concentration lower than 202.2 mg/L, as this concentration could achieve a good biofilm morphology while not inhibiting its microbial activity. 相似文献
997.
Arbuscular mycorrhizae enhance metal lead uptake and growth of host plants under a sand culture experiment 总被引:2,自引:0,他引:2
A sand culture experiment was conducted to investigate whether mycorrhizal colonization and mycorrhizal fungal vesicular numbers were influenced by metal lead, and whether mycorrhizae enhance host plants tolerance to metal lead. Metal lead was applied as Pb(NO3)2 in solution at three levels (0, 300 and 600 mg kg(-1) sand). Five mycorrhizal host plant species, Kummerowia striata (Thunb.) Schindl, Ixeris denticulate L., Lolium perenne L., Trifolium repens L. and Echinochloa crusgalli var. mitis were used to examine Pb-mycorrhizal interactions. The arbuscular mycorrhizal inoculum consisted of mixed spores of mycorrhizal fungal species directly isolated from orchard soil. Compared to the untreated control, both Pb concentrations reduced mycorrhizal colonization by 3.8-70.4%. Numbers of AM fungal vesicles increased by 13.2-51.5% in 300 mg Pb kg(-1) sand but decreased by 9.4-50.9% in 600 mg Pb kg(-1) sand. Mycorrhizae significantly enhanced Pb accumulation both in shoot by 10.2-85.5% and in root by 9.3-118.4%. Mycorrhizae also enhanced shoot biomass and shoot P concentration under both Pb concentrations. Root/shoot ratios of Pb concentration were higher in highly mycorrhizal plant species (K.striata, I. denticulate, and E. crusgalli var. mitis) than that in poorly mycorrhizal ones (L. perenne and T. repens,). Mycorrhizal inoculation increased the root/shoot ratio of Pb concentration of highly mycorrhizal plant species by 7.6-57.2% but did not affect the poorly mycorrhizal ones. In the treatments with 300 Pb mg kg(-1) sand, plant species with higher vesicular numbers tended to show higher root/shoot ratios of the Pb concentration. We suggest that under an elevated Pb condition, mycorrhizae could promote plant growth by increasing P uptake and mitigate Pb toxicity by sequestrating more Pb in roots. 相似文献
998.
999.
The effect of methanol of low concentration on adsorption and leaching of atrazine and tebuconazole was studied in this paper. The adsorption coefficients and the retardation factors (Rm) of pesticides on EUROSOIL 3# log-linearly decreased as volumetric fraction of methanol (fc) was increased in the binary solvent mixtures of methanol and water. These data are consistent with solvophobic theory formerly outlined for describing the adsorption and transport of hydrophobic organic chemicals from mixed solvents. Nevertheless, the adsorption of these pesticides in soil–water system slightly increased when the soil was pre-washed with methanol in comparison with that pre-washed with water (pure water system). Furthermore, their adsorption coefficients were still higher in binary solvent systems with methanol of very low concentrations, i.e. fc<0.03 for atrazine and fc<0.01 for tebuconazole, than those in pure water system. The adsorption coefficients (logKw) of atrazine and tebuconazole predicted by solvophobic theory were 0.5792 and 1.6525, respectively, and their experimental logKw were 0.3701 and 1.6275 in pure water system. Obviously, the predicted logKw of the two pesticides was higher than the experimental log Kw in pure water system. The predicted Kw and the retardation factor (Rw) in pure water system by solvophobic theory are thus possibly inaccurate. 相似文献
1000.
Pan B Liu WX Shi Z Cao J Shen WR Qing BP Sun R Tao S 《Journal of environmental science and health. Part. B》2004,39(3):353-365
The methods of sample purification for determinations of organochlorine pesticides (OCPs) in sediment and fish muscle were investigated in this study. A two-step procedure with preliminary cleanup and florisil column fraction was adopted. The working conditions of florisil column were firstly optimized. As to preliminary cleanup, liquid-liquid extraction by mixture of dimethyl formamide (DMF) and hexane and sulphonation by concentrated sulfuric acid were applied respectively and compared for the studied samples. The results indicated that liquid-liquid distribution could effectively separate lipids from fish muscle extracts, while failed in elimination of chlorophyll extracted from the relicts of hydrophytes in the sediment sample. In view of the sample appearance and clarity of gas chromatogram, sulphonation was more suitable to purify the sediment sample, however, the recoveries of the spiked standards were poor. The use of eluting solvent with stronger polarity could improve the corresponding recoveries significantly. Due to complete loss of Dieldrin, Endrin, and Endrin aldehyde after sulphonation, this pretreatment was improper to the three components. Sulfur, as the particular disturbing element in sediment, could be removed sufficiently by addition of activated copper powder. The relevant detection limits of the selected methods for OCPs in the studied substrates were also provided. 相似文献