Journal of Environmental Sciences - Volume 17, issue 3

Authors: FU, Qiang | YIN, Cheng-qing | MA, Yun

Article Type: Research Article

Abstract: Wetland systems in headstream watersheds are important to control the nonpoint source pollutant phosphorus. Experiments were conducted using intact sediment-water columns obtained from the multipond system in Liuchahe watershed of Chaohu Lake to determine its capacity to retain P. It was found that pond sediments had strong P retention ability. For the Hill pond, Village pond and Rice pond, their retention coefficient (A) were 288.3, 279.2 and 260.8 L/m^2 , respectively. The equilibrium P concentration …(EPC_w ) were 0.016, 0.028 and 0.018 mg/L, respectively. The Hill pond indicated the highest P retention ability. P retained in the pond sediments indicated high stable degree. P removal from the overlying water column into the pond sediments followed a first-order kinetic model. Under the experimental hydrological conditions, the retention time had a positive correlation with the P loading. The multipond system could provide enough retention time to retain P in drainage runoffs. At the P levels evaluated, the sediments of the multipond system are effective sinks to retain P from nonpoint source runoffs. Show more

Keywords: phosphorus, pond, sediment, watershed, nonpoint source

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 404-408, 2005

Authors: XI, Bei-dou | LIU, Hong-liang | HUANG, G H | ZHANG, Bai-yu | QIN, Xiao-sheng

Article Type: Research Article

Abstract: Bio-surfactant is a new type of surfactant that is produced in microbial metabolism. Adding bio-surfactant during composting process, especially to those contain some toxic substances, has been proved to be a promising way. In this study, Strains III (2), a bacterial with high activity to produce bio-surfactant, were isolated firstly. Following comparison experiments with and without adding Strains III (2), namely Run 1 and Run R, were conducted, respectively. The experimental results showed that, by adding …Strains III (2), the surface tension could reduce from 46.5 mN/m to 39.8 mN/m and the corresponding time to maintain the surface tension under 50 mN/m could prolong from 60 h to 90 h. The oxygen uptake rate and total accumulated oxygen consumption with Stains III (2) were both higher than those without Strains III (2), while the accumulation of H_2 S in outlet gas was reduced to around 50% of Run R. Moreover, two additional experiments were also carried out to examine the effects of strains coming from different systems. One is adding Strains III (2) with a dose of 0.4% (Run 2), and the other is seedling commercial Strains at the same conditions, the composting experiments showed that: Run 2 was more effective than Run 3, because the commercial Strains can be suppressed significantly in a complex composting system with different pH, high temperature and some of metals. The bio-surfactant was also added into the solid waste, which contained some toxic substances, the corresponding results showed that the remove rate of Hg and sodium pentachlorophenolate (PCP-Na) could be improved highly. Thus, the microenvironment, reactionrate and composting quality could be enhanced effectively by adding bio-surfactant to the composting process. Show more

Keywords: municipal solid waste, composting, bio-surfactant, composting quality

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 409-413, 2005

Authors: WANG, Jun | GUO, Bao-dong | ZHANG, Zhao-hong | ZHANG, Xiang-dong | WU, Jing | LI, Hong

Article Type: Research Article

Abstract: The nanometer and ordinary anatase titanium dioxide (TiO_2 ) powders were adopted as the sonocatalysts for the degradation of methyl orange used as a model compound for the first time. It was found that the sonocatalytic degradation effect of methyl orange in the presence of TiO_2 powder were much better than that without TiO_2 , but the sonocatalytic activity of the nanometer anatase TiO_2 particle was obviously higher than that …of ordinary anatase TiO_2 particle. Although there are many factors influencing sonocatalytic degradation of methyl orange, the experimental results showed that the best degradation ratio of methyl orange could be obtained when the experimental conditions were: initial concentration 15 mg/L, nanometer anatase TiO_2 adding amount 750 mg/L, ultrasonic frequency 40 kHz, output power 50 W, pH = 3.0 and temperature 40°C within 150 min. In addition, the catalytic activity of reused nanometer anatase TiO_2 catalyst was also studied and found to decline gradually comparing with initial nanometer anatase TiO_2 catalyst. All experiments indicated that the method of the sonocatalytic degradation of organic pollutants in the presence of TiO_2 powder was an advisable choice for non- or low-transparent organic wastewaters. Show more

Keywords: titanium dioxide (TiO_2), sonocatalytic degradation, methyl orange, nanometer anatase, ordinary anatase

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 414-418, 2005

Authors: GUAN, Bao-hong

Article Type: Research Article

Abstract: Terylene artificial silk printing and dyeing wastewater (TPD wastewater), containing averaged 710 mg/L terephthalic acid (TA) as the main carbon source and the character pollutant, was subjected to expanded granular sludge bed (EGSB) process. The stability of theEGSB process was firstly conducted by laboratory experiment. TA ionization was the predominated factor influencing the acid-base balance of the system. High concentration of TA in wastewater resulted in sufficient buffering capacity to neutralize the volatile …fatty acids (VFA) generated from substrate degradation and provided strong base for anaerobic system to resist the pH decrease below 6.5. VFA and UFA caused almost no inhibition on the anaerobic process and biogas production except that pH was below 6.35 and VFA was at its maximum value. Along with the granulating of the activated sludge, the efficiency of organic removal and production rate of biogas increased gradually and became more stable. After start-up, the efficiency of COD removal increased to 57%–64%, pH stabilized in a range of 7.99–8.04, and production rate of biogas was relatively high and stable. Sludge granulating, suitable influent of pH and loading were responsible for the EGSB stability. The variation of VFA concentration only resulted in neglectable rebound of pH, and the inhibition from VFA could be ignored in EGSB. The EGSB reactor was stable for TPD wastewater treatment. Show more

Keywords: expanded granular sludge bed, stability, anaerobic treatment, dyeing and printing wastewater

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 419-424, 2005

Authors: PENG, Yong-zhen | WANG, Zhi-hui | WANG, Shu-ying

Article Type: Research Article

Abstract: The control strategy and simulation of external carbon addition were specially studied in an anoxic-oxic (A/O) process with low carbon: nitrogen (C/N) domestic wastewater. The control strategy aimed to adjust the flow rate of external carbon dosage to the anoxic zone, thus the concentration of nitrate plus nitrite (NOx^- -N) in the anoxic zone was kept closed to the set point. The relationship was studied between the NOx^- -N concentration in the anoxic zone …(S_{No} ) and the dosage of external carbon, and the results showed that the removal efficiency of the total nitrogen (TN) could not be largely improved by double dosage of carbon source when S_{NO} reached about 2 mg/L. Through keeping S_{NO} at the level of about 2 mg/L, the demand of effluent quality could be met and the carbon dosage could be optimized. Based on the Activated Sludge Model No. 1 (ASM No. 1), a simplified mathematical model of external carbon dosage was developed. Simulation results showed that PI controller and feed-forward PI controller both had good dynamic response and steady precision. And feed-forward PI controller had better control effects due to its consideration of influent disturbances. Show more

Keywords: ASM No. 1, biological nitrogen removal, external carbon addition, feed-forward PI control

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 425-428, 2005

Authors: ZHANG, Chang-bin | SHI, Xiao-yan | GAO, Hong-wei | HE, Hong

Article Type: Research Article

Abstract: Catalytic elimination of formaldehyde (HCHO) was investigated over Cu-Al_2 O_3 catalyst at room temperature. The results indicated that no oxidation of HCHO into CO_2 occurs at room temperature, but the adsorption of HCHO occurs on the catalyst surface. With the increase of gas hourly space velocity (GHSV) and inlet HCHO concentration, the time to reach saturation was shortened proportionally. The results of the in situ DRIFTS, Density functional theory calculations and …temperature programmed desorption (TPD) showed that HCHO was completely oxidized into HCOOH over Cu-Al_2 O_3 at room temperature. With increasing the temperature in a flow of helium, HCOOH was completely decomposed into CO_2 over the catalyst surface, and the deactivated Cu-Al_2 O_3 is regenerated at the same time. In addition, although Cu had no obvious influence on the adsorption of HCHO on Al_2 O_3 , Cu dramatically lowered the decomposition temperature of HCOOH into CO_2 . It was shown that Cu-Al_2 O_3 catalyst had a good ability for the removal of HCHO, and appeared to be promising for its application in destroying HCHO at room temperature. Show more

Keywords: formaldehyde, Cu-Al_2O_3, in situ DRIFTS, TPD

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 429-432, 2005

Authors: ZHANG, Yao-bin | QUAN, Xie | ZHAO, Hui-min | CHEN, Shuo | YANG, Feng-lin

Article Type: Research Article

Abstract: A novel process, microwave assisted catalytic wet air oxidation (MW-CWO), was applied for the degradation of H-acid (1-amino-8-naphthol-3, 6-disulfonic acid) in aqueous solution. Ni-loaded granular activated carbon (GAG), prepared by immersion-calcination method, was used as catalyst. The results showed that the MW-CWO process was very effective for the degradation of H-acid in aqueous solution under atmospheric pressure with 87.4% TOC (total organic carbon) reduction in 20 min. Ni on GAC existed in the form of NiO …as specified by XRD. Loss of Ni was significant in the initial stage, and then remained almost constant after 20 min reaction. BET surface area results showed that the surface property of GAC after MW-CWO process was superior to that of blank GAC. Show more

Keywords: microwave, degradation, catalysis, nickel, wet air oxidation

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 433-436, 2005

Authors: ZHENG, Yan-mei | ZHANG, Ying | HUANG, Guo-qiang | JIANG, Bin | LI, Xin-gang

Article Type: Research Article

Abstract: Air sparging (AS) is an emerging method to remove VOCs from saturated soils and groundwater. Air sparging performance highly depends on the air distribution resulting in the aquifer. In order to study gas flow characterization, a two-dimensional experimental chamber was designed and installed. In addition, the method by using acetylene as the tracer to directly image the gas distribution results of AS process has been put forward. Experiments were performed with different injected gas flow rates. …The gas flow patterns were found to depend significantly on the injected gas flow rate, and the characterization of gas flow distributions in porous media was very different from the acetylene tracing study. Lower and higher gas flow rates generally yield more irregular in shape and less effective gas distributions. Show more

Keywords: air sparging, gas flow pattern, groundwater, radius of influence (ROI)

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 437-439, 2005

Authors: LU, Yi-tong | CHEN, Xiao-bin | ZHOU, Pei | LI, Zhen-hong

Article Type: Research Article

Abstract: As an oil-decomposable mixture of two bacteria strains (Bacillus sp. and Pseudomonas sp.), Y3 was isolated after 50 d domestication under the condition that oil was used as the limited carbon source. The decomposing rate by Y3 was higher than that by each separate individual strain, indicating a synergistic effect of the two bacteria. Under the conditions that T = 25–40°C, pH = 6–8, HRT (Hydraulic retention time) = 36 h and the oil concentration at …0.1%, Y3 yielded the highest decomposing rate of 95.7%. Y3 was also applied in an organic waste treatment machine and a certain rate of activated bacteria was put into the stuffing. A series of tests including humidity, pH, temperature, C/N rate and oil percentage of the stuffing were carried out to check the efficacy of oil-decomposition. Results showed that the oil content of the stuffing with inoculums was only half of that of the control. Furthermore, the bacteria were also beneficial to maintain the stability of the machine operating. Therefore, the bacteria mixture as well as the machines in this study could be very useful for waste treatment. Show more

Keywords: oil-decomposing microorganism, screening, application, organic waste treatment machine, decomposing rate

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 440-444, 2005

Authors: YU, Gang | YU, Qi | JIANG, Yan-long | ZENG, Ke-si | GU, Fan

Article Type: Research Article

Abstract: Non-thermal plasma has been proved to be an effective and competitive technology for removing NO in flue gas since 1970. In this paper, the NO reduction mechanism of the non-thermal plasma reaction in NO/N_2 /O_2 system was investigated using the method of spectral analysis and quantum chemistry. By the establishment of NO reduction and gas discharge plasma emission spectrum measuring system, the NO reduction results, gas discharge emission spectra of …NO/N_2 O_2 and pure N_2 were obtained, and then the model of molecular orbit of N_2 either in ground state or its excited state was worked out using the method of molecular orbit Ab initio in Self-Consistent Field (SCF). It was found that NO reduction in NO/N_2 gas discharge plasma was achieved mainly through a series of fast elementary reactions and the N(E6) at excited state was the base for NO reduction. Show more

Keywords: NO reduction, plasma, mechanism, spectral analysis, quantum chemistry

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 445-447, 2005

Authors: YANG, Ye | CHEN, Ying-xu | TIAN, Guang-ming | ZHANG, Zi-jian

Article Type: Research Article

Abstract: A greenhouse experiment was carried out to compare differences in potential activities of ammonification, nitrification and denitrification in rhizosphere and bulk soil in a heavy-metal-stressed system. Exchangeable fractions of Cd, Cu and Cr were all higher in the rhizosphere of maize than in bulk soil. Results showed that the mineralization of N in soil was stimulated by low concentration of Cd. Addition of Cd at low levels stimulated the ammonifying and nitrifying activity in soil, while …inhibitory influences were shown at high levels. Nitrifying bacteria was proved to be the most sensitive one, whilst the effect on denitrifying bacteria was very limited. Comparing Cd, Cu and Cr(VI) at 20 mg/kg soil, Cd was the most effective inhibitor of ammonification and denitrification, while Cr(VI) had the strongest inhibitory influence on nitrifying activity. Root exudates played important roles on the different exchangeable metal fractions and bacterial activities between rhizosphere and non-rhizosphere. Nitrate was the main form of mineral N in soil, as well as the main form of N absorbed by plants, but the formation and relative absorption of ammonium were promoted in response to high Cd exposure. Show more

Keywords: heavy metal, nitrogen cycle, rhizosphere, root exudates

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 448-451, 2005

Authors: NI, Cai-ying | CHEN, Ying-xv | LIN, Qi | TIAN, Guang-ming

Article Type: Research Article

Abstract: The ability of Elsholtzia splendens Naki (E. splendens) to accumulate copper appears to be governed by its high degree of copper tolerance. However, the tolerance mechanism on the physiological basis is unknown. Using transmission electron microscope (TEM) and energy dispersive analysis of X-rays (EDX), the likely location of copper within the cells of the tolerant and non-tolerant was determined. Here the role of vacuolar and cell wall compartmentalization in this copper tolerant plant were investigated. A …direct comparison of copper locations of E. splendens and the non-tolerant Astragalus sinicus L. (A. sinicus) showed that the majority of copper in the tolerant was localized primarily in the vacuolar, cell wall, on the plasmamembrane, beside lipid grains induced by copper pollution, in the chloroplasts and amyloids; but in the non-tolerant, copper precipitates only be observed on the plasmamembrane, in the chloroplasts and cytoplasm under copper exposure conditions that were toxic to both species. This revealed that the tolerant accumulates more copper in the vacuole and cell wall than the non-tolerant, where was regarded as the storage compartment of tolerant plant or hyperaccumulator for heavy metals. Show more

Keywords: A. sinicus, copper (Cu), E. splendens, localization, subcellular

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 452-456, 2005

Authors: ZHU, Gui-bing | PENG, Yong-zhen | WU, Shu-yun | WANG, Shu-ying

Article Type: Research Article

Abstract: Control of sludge age and mixed liquid suspended solids concentration in the activated sludge process is critical for ensuring effective wastewater treatment. A nonlinear dynamic model for a step-feed activated sludge process was developed in this study. The system is based on the control of the sludge age and mixed liquor suspended solids in the aerator of last stage by adjusting the sludge recycle and wastage flow rates respectively. The simulation results showed that the sludge …age remained nearly constant at a value of 16 d in the variation of the influent characteristics. The mixed liquor suspended solids in the aerator of last stage were also maintained to a desired value of 2500 g/m^3 by adjusting wastage flow rates. Show more

Keywords: wastewater treatment, sludge age, control, modeling and simulation, step-feed process

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 457-459, 2005

Authors: MASKAOUI, Khalid | ZHOU, Jun-liang | HAN, Ya-li | HU, Zhong | ZHENG, Tian-ling | HONG, Hua-sheng

Article Type: Research Article

Abstract: The paper aimed to identify the primary of polychlorinated biphenyls (PCBs) in the diulong River Estuary, investigate the spatial distribution of PCBs contamination in the environment, localize the atmospheric source and evaluate ongoing PCBs emissions by analyzing soil samples collected along the Jiulong River region. In addition, the accumulation of PCBs in the human food chain was quantified by analyzing leaf of orange trees and vegetable samples collected along a gradient of soil/atmospheric contamination moving …away from the source. Consequently, the impact on the human health and the ecosystem was quantified, different management options were proposedto reduce this impact and to carry out research on organic contaminants along the Jiulong River and Xiamen region. Show more

Keywords: Jiulong River, PCBs, soil, vegetable, contamination

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 460-464, 2005

Authors: SHEN, Ying-jie | WU, Guang-xia | XU, Shu-guang | ZHONG, Hui | ZHANG, Shao-lai | ZHANG, Xue-zhu | ZHAO, Xian-hong | WU, Tong | ZHANG, Wei-jun

Article Type: Research Article

Abstract: Using the inner-surface of polysulfone hollow fiber ultrafiltration membranes as grafted layer, the method of gas-initiation and liquid-polymerization has been studied, which aimed to adjust the diameter of the pores in the membranes. The degree of polymerization varied with the changes of the parameters, such as irradiation time, monomer concentration, temperature and time of polymerization and soon. The results indicated that using benzophenone (BP) which is in a gaseous condition as photo-initiator, …acrylamide as graft monomer, the polyacrylamide chain was grafted on the surface of membranes. After the surface membrane being modified, the water flux and retention altered, and thus it can be seen that the diameter of the pores in the membrane was altered. These experiments contribute to finding a new way to produce the hollow fiber membrane with the small pore size and are extraordinarily worth developing and studying. Show more

Keywords: polysulfone hollow fiber membrane, photografting, gas-initiation, surface-modification

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 465-468, 2005

Authors: CHENG, Jin-ping | YANG, Yi-chen | HU, Wei-xuan | YANG, Liu | WANG, Wen-hua | JIA, Jin-ping | LIN, Xue-yu

Article Type: Research Article

Abstract: In order to study the molecular mechanism of injury in rat organs induced by methylmercury, and the relationship between neurotransmitter and oxidative damage in the toxicity process of rat injury by methylmercury was studied. The control group was physiological saline of 0.9%, the concentration of exposure groups were 5 mg/(kg˙d) and 10 mg/(kg·d) respectively. The content of AChE, ACh, NOS, NO, MDA, SOD, GSH-Px and GSH in different organs of rats were determined with conventional methods. …The results showed that after exposure to methylmercury for 7 d, the mercury content in brain of exposure groups increased clearly and had significant difference compared with the control group (P < 0.01). In rat's brain, serum, liver and kidney, the content of ACh and AChE were all decreased; the content of NOS and NO were all increased; the content of MDA was increased compared with the control group, the exposure groups had significant difference (P < 0.01); the content of SOD, GSH and GSH-Px was decreased compared with the control group, the exposure groups had significant difference (P < 0.01). It could be concluded that methylmercury did effect the change of neurotransmitter and free radical. They participated in the toxicity process of injury by methylmercury. The damage of neurotransmitter maybe cause the chaos of free radical and the chaos of free radical may also do more damage to neurotransmitter vice versa. Show more

Keywords: methylmercury, neurotransmitter, oxidative damage

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 469-473, 2005

Authors: ZHANG, Peng | WU, Zhi-chao

Article Type: Research Article

Abstract: The aim of this research is to find substitute barrier materials for natural clay from two kinds of municipal sludge: waterworks sludge (S_w ) and dredging sludge (S_d ). Laboratory tests were performed firstly to determine their Atterberg limits and hydraulic conductivity. Based on the results, the use of waterworks sludge was recommended. Then, shear strength tests were performed and it was found the shear resistance property of waterworks sludge is strong enough to …maintain slope stability. In order to evaluate the possibility of secondary pollution, the heavy metal contents of waterworks sludge was determined and the results indicated that secondary pollution is unlikely happened. Finally, economic analysis proves that reusing waterworks sludge as barrier will reduce the lost a great for both landfill and waterworks. Based on the results, waterworks sludge was proposed to use and a further long-term simulated landfill test was suggested. Show more

Keywords: waterworks sludge, dredging sludge, barrier material, Atterberg limits, hydraulic conductivity, shear strength

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 474-477, 2005

Authors: LING, Wan-ting | WANG, Hai-zhen | XU, Jian-ming | GAO, Yan-zheng

Article Type: Research Article

Abstract: The dissolved organic matter (DOM), water soluble organic matter derived from sewage sludge was separated into hydrophobic fraction (Ho) and hydrophilic fraction (Hi). The sorption of DOM and its fractions on soils and the effects of DOM sorption on a nonionic pesticide (atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-trazine)) distribution between soil and water were investigated using a batch equilibrium technique. The total DOM sorption on soils described by the Langmuir equation reached saturation as the DOMconcentration …increased. The sorption of Ho fit the Freundlich model. In contrast, a negative retention evidently occurred as adding Hi at higher level in tested soils. The sorption of Ho dominated the total DOM sorption and the release of soil organic matter (SOM). Effects of DOM on the atrazine sorption by soils were DOM-concentration dependent and dominated by the interaction of atrazine, DOM, and soil solids. Generally, the presence of DOM with lower concentration promoted atrazine sorption on soils, namely the apparent partitioning constant (K^*_d ) for atrazine sorption in the presence of DOM was larger than the distribution constant (K_d ) without DOM; whereas the presence of DOM with higher concentration inhibited atrazine sorption (i. e., K^*_d <K_d ). The overall effects of DOM on atrazine sorption in soils might be related to the DOM sorption and the release of soil intrinsic organic matter into aqueous solution. The sorption of Ho on soils promoted the atrazine sorption on soil, while the release of SOM by Hi and the competitive sorption between Hi and atrazine on soil surface led to a decrease of atrazine sorption. Information provided in this work may contribute to a better understanding of the DOM sorption and its impacts on the contaminant soil-water distribution. Show more

Keywords: dissolved organic matter (DOM), atrazine, sorption, soil

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 478-482, 2005

Authors: ZHAO, Yi | WANG, Li-dong | WANG, Xiao-ming | LI, Qiang-wei | XU, Pei-yao

Article Type: Research Article

Abstract: In the presence of inhibitors, the macroscopical oxidation kinetics of calcium sulfite, the main byproduct in wet limestone scrubbing, was studied for the first time by adding different inhibitors and varying pH, concentration of calcium sulfite, oxygen partial pressure, concentration of inhibitors and temperature. The mathematical model about the general oxidation reaction was established, which was controlled by three steps involving dissolution of calcium sulfite, mass transfer of oxygen and chemical reaction in the solution. …It was concluded that the general reaction was controlled by mass transfer of oxygen under uncatalyzed conditions, while it was controlled by dissolution of calcium sulfite after adding three kinds of inhibitors. Thus, the theory was provided for investigating the mechanism and oxidation kinetics of sulfite. The beneficial references were also supplied for design of oxidation technics in the wet limestone scrubbing. Show more

Keywords: calcium sulfite, macroscopical, oxidation, kinetics, inhibitor

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 483-487, 2005

Authors: XIA, Ji-yang | LEUNG, Dennis Y.C.

Article Type: Research Article

Abstract: A stable finite element method for the time dependent Navier-Stokes equations was used for studying the wind flow and pollutant dispersion within street canyons. A three-step fractional method was used to solve the velocity field and the pressure field separately from the governing equations. The Streamline Upwind Petrov-Galerkin (SUPG) method was used to get stable numerical results. Numerical oscillation was minimized and satisfactory results can be obtained for flows at high Reynolds numbers. Simulating the flow …over a square cylinder within a wide range of Reynolds numbers validates the wind field model. The Strouhal numbers obtained from the numerical simulation had a good agreement with those obtained from experiment. The wind field model developed in the present study is applied to simulate more complex flow phenomena in street canyons with two different building configurations. The results indicated that the flow at rooftop of buildings might not be assumed parallel to the ground as some numerical modelers did. A counter-clockwise rotating vortex may be found in street canyons with an inflow from the left to right. In addition, increasing building height can increase velocity fluctuations in the street canyon under certain circumstances, which facilitate pollutant dispersion. At high Reynolds numbers, the flow regimes in street canyons do not change with inflow velocity. Show more

Keywords: finite element method, Streamline Upwind Petrov-Galerkin method, three-step fractional method

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 488-490, 2005

Authors: HU, Ji-ye | ZHANG, Wen-ji | LI, Jian-zhong

Article Type: Research Article

Abstract: The method of residue analysis of a new synthesized fungicide 2-allylphenol was studied by simulating the active compound structure in Gingko tree (Gingko biloba L.) and its dissipation rate and terminal residue levels in tomato under field condition. Residues of 2-allylphenol were extracted from tomato matrix with acetone, purified by liquid-liquid extraction and Florisil cartrieges, and then determined by HPLC with UV-detector. The minimum detectable amount of 2-allylphenol was 3 × 10^{-9} g, …the minimum detectable concentration of 2-allylphenol in the samples of tomato were 0.01 mg/kg. The ranges of average recoveries and coefficient variation of the method were 87.7%–90.2% and 1.25%–2.06%, respectively. The dissipation rate and terminal residue levels in tomato were determined with the method described above. The results showed that the half-life of 2-allylphenol in tomato was 6.37 d, and 2-allylphenol declined with 82.6% of the initial deposit remaining in tomato at harvest. The terminal residue levels in tomato were 0.15 mg/kg and 0.20 mg/kg following the recommended doses and time intervals. Show more

Keywords: fungicide, 2-allylphenol, residue analysis, dissipation

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 491-493, 2005

Authors: HUANG, Xiao-wu | CHENG, Wen | HU, Yong-you

Article Type: Research Article

Abstract: Screening of new microorganism being able to produce efficiently flocculants was carried out. A new model for screening efficient flocculant-producing strains was designed and tested. The results showed that this model for screening efficient flocculant-producing strains is very reliable and can greatly shorten the screening period. 13 flocculant-producing strains were isolated from activated sludge by conventional method. A strain, designated as HHE6, produced the bioflocculant with the turbidity removal 98% for kaolin …suspension. Six of 13 strains selected as the original strains were treated with NTG as mutagen, and five mutant strains (HHE-P7, HHE-A8, HHE-P21, HHE-P24, HHE-A26) with high flocculation efficiency was obtained by selection, which exhibited the flocculation rate for kaolin suspension above 90%. Strains HHE6, HHE-P7, and HHE-P24 were classified as Penicillium purpurogenum, HHE-P21 as Penicillium cyclopium, HHE-A26 as Aspergillus versicolor and HHE-A8 as Aspergillus fumigatus, and it is hitherto unreported for biofloccutant-producing strains of Penicillium. The growth of the six strains (HHE6, HHE-P7, HHE-A8, HHE-P21, HHE-P24, HHE-A26) had similar curves, i.e. firstly increasing rapidly, keeping relatively constant then and finally decreasing gradually with cultivation time. The production of bioflocculants by strains showed the similar pattern to strain growth. Show more

Keywords: bioflocculant, mutation breeding, bioflocculant-producing strains, Penicillium, Aspergillus

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 494-498, 2005

Authors: LI, Hao | MIAO, Jin-lai | CUI, Feng-xia | LIU, Xiao-guang | LI, Guang-you

Article Type: Research Article

Abstract: The effect of Ca^{2+} on the removal of Alexandrium sp. LC3 under HDTMAB stress was investigated. The results showed that the toxic effect of HDTMAB on Alexandrium sp. LC3 was significantly reduced in the presence of Ca^{2+} , especially under 4 mmol/L of Ca^{2+} . To understand the underlying mechanism, the SH group and MDA content of the cell membrane and membrane permeability were measured. It was found that the SH content …of cell member increased, the MDA content and membrane permeability decreased when Alexandrium sp. was treated with Ca^{2+} and HDTMAB complex, compared with using HDTMAB only. The data suggested that Ca^{2+} might promote HDTMAB stress resistance of Alexandrium sp. LC3 by reducing the permeability and increasing the stability of cell membrane. Show more

Keywords: Ca^{2+}, surfactant, Alexandrium sp. LC3, cell membrane permeability

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 499-502, 2005

Authors: YU, Yun-long | FANG, Hua | WANG, Xiao | YU, Jing-quan | FAN, De-fang

Article Type: Research Article

Abstract: The dissipation of chlorpyrifos on pakchoi inside and outside greenhouse was studied. The decline curve of chlorpyrifos on pakchoi could be described as first-order kinetic. The experimental data showed that both the hermetic environment of greenhouse and season affected dissipation rates of chlorpyrifos on pakchoi. Chlorpyrifos declined faster outside greenhouse than inside greenhouse. Chlorpyrifos residues at pre-harvest time were below the maximum residue limits (MRLs) fixed in China, whereas the values inside …greenhouse were higher than those outside greenhouse by almost 50%. The recommended pre-harvest time established under conditions of open field might not always fit to greenhouse production. Show more

Keywords: chlorpyrifos, residue, dissipation, pakchoi, greenhouse

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 503-505, 2005

Authors: LAN, Hui-xia | CHEN, Yuan-cai | CHEN, Zhong-hao | CHEN, Rong

Article Type: Research Article

Abstract: Cultivation of aerobic granular sludge for pentachlorophenol (PCP) degradation under microaerobic condition (DO concentration was controlled at 0.2–0.7 mg/L) was studied in this paper. Anaerobic granules were selected as inoculum. The changes of appearance were observed and the variations of SVI, VSS/TSS, PN/PS and the size of sludge were measured during cultivating. The capabilities for degradation of PCP, AOX and CODcr were also studied. Observations on mature granules were carried out by scanning electron …microscope, and the results indicated bacillus was dominant on the surface of granules while in the inner of granules both bacillus and coccus were the dominant microorganisms. K, Na, Fe, Ca, Mg, Ni, Co, Mn, Cu and Zn were detected in the granules by element analysis. Show more

Keywords: aerobic granular sludge, pentachlorophenol, microaerobic condition

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 506-510, 2005

Authors: OPARA, K.N. | FAGBEMI, B.O.

Article Type: Research Article

Abstract: To determine the factor influencing the abundance development and distribution of Simulium damnosum (S. I) immature stages in the lower Cross River Basin, Nigeria, the physico-chemical characteristics of water at breeding sites were analysed longitudinally over a 12 month period. Analysis of the water samples showed that water current correlated positively and significantly (p < 0.05), with dissolved oxygen (r = 0.95 vs 0.10); conductivity (r = 0.95 vs 0.81); hydrogen ion concentration (r = …0.03 vs 0.46); and biochemical oxygen demand (r = 0. 80 vs 0.64); from Agbokim Waterfalls and Afi River respectively. The result indicates that these parameters and Iow ionic concentration are the most essential requirement for the development of S. damnosum pre-imaginal stages. Amplitudes of annual variability as measured by co-efficient of variation varied between the parameters. From the trends in hydrological variables it was deduced that the integrated impact of precipitation, input of surface runoff and municipal effluents played an overriding role in determining the absolute levels and temporal pattern in the water quality attributes. Of the 3578 pre-imaginal stages of S. damnosum collected, 52.52% and 47.4% were collected from Agbokim Waterfall and Afl River respectively. There was a significant difference (p < 0.05) in the number of pre-imaginal stages collected from both sites. The highest number of pre-imaginal stages of S. damnosum collected were at the peak of rain (July-September) indicating that S. damnosum in the River Basin is a wet season breeder. The need for long term laboratory colonization of blackfly immature stages becomes imperative especially how these parameters could be exploited in control programme through the testing of larvicides without adverse ecological damage to the aquatic habitat. Show more

Keywords: blackflies, Simulium damnosum physico-chemical parameters, lower Cross River Basin, Nigeria

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 511-517, 2005

Authors: WANG, Li-gang | CHEN, Chang-he | Kolker, Kruse H.

Article Type: Research Article

Abstract: The adsorption capacity for vapor-phase elemental mercury (Hg^0 ) of residual carbon separated from fly ash was studied in an attempt for the control of elemental mercury emissions from combustion processes. At Iow mercury concentrations (< 200 μg/m^3 ), unburned carbon had higher adsorption capacity than commercial activated carbon. The adsorbality of unburned carbon was also found to be source dependent. Isotherms of FS carbon (separated from fly ash of …a power plant of Shishi in Fujian Province) were similar to those classified as type II. Isotherms of XJ carbon (separated from fly ash of a power plant of Jingcheng in Shanxi Province) were more like those classified as type III. Due to the relatively Iow production costs, these residual carbons would likely be considerably more costeffective for the full-scale removal of mercury from combustion flue gases than other technology. Show more

Keywords: mercury, adsorption, residual carbon, fly ash, activated carbon

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 518-520, 2005

Authors: LIU, Jing-shuang | YU, Jun-bao

Article Type: Research Article

Abstract: Element cycling in the dominant plant communities including Rh. aureum, Rh. redowskianum and Vaccinium uliginosum in the Alpine tundra zone of Changbai Mountains in northeast China was studied. The results indicate that the amount of elements from litter decomposition was less than that of the plant uptake from soil, but that from plant uptake was higher than that in soil with mineralization process released. On the other hand, in the open system including precipitation input and …soil leaching output, because of great number of elements from precipitation into the open system, the element cycling (except N, P) in the Alpine tundra ecosystem was in a dynamic balance. In this study, it was also found that different organ of plants had significant difference in accumulating elements. Ca, Mg, P and N were accumulated more obviously in leaves, while Fe was in roots. The degree of concentration of elements in different tissues of the same organ of the plants also was different, a higher concentration of Ca, Mg, P and N in mesophyll than in nerve but Fe was in a reversed order. The phenomenon indicates (1) a variety of biochemical functions of different elements, (2) the elements in mesophyll were with a shorter turnover period than those in nerve or fibre, but higher utilization rate for plant. Therefore, this study implies the significance of keeping element dynamic balance in the alpine tundra ecosystem of Changbai Mountains. Show more

Keywords: element cycling, ecosystem, dominant plant community, alpine tundra zone, Changbai Mountains

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 521-525, 2005

Authors: LI, Pei-jun | YIN, Pei-jie | ZHOU, Qi-xing | SHI, Xing-qun | XIONG, Xian-zhe

Article Type: Research Article

Abstract: The phytotoxicity of chlorobenzoic acids (CBAs) was studied and the biochemical endpoints' suitability and sensibility was evaluated. Two terrestrial plant species in the same family were exposed to different concentrations of CBAS and tested their germination according to the guideline of Organization for Economic Cooperation and Development (OECP, 1984). The results showed that CBA dose-inhibition rate of classical endpoint had the distinct linear relationship in the range of 10%–50% inhibition rate for …root elongation (p < 0.01), and the dose variances of CBAs had the greater influence on the inhibition rate of germination than on inhibition rate of root elongation. The CBA dose half effect concentration-inhibition rate of two antioxidant enzyme activity superoxide dismutase (SOD) and catalase (CAT) had the quadratic relationship, and CBA dose-inhibition rate of the peroxides (POD) activity had the linear relationship (p <0.05). Comparing the half effect concentration (EC_{50} ) of two kinds of endpoints, the POD activity was more sensitive than classical endpoint, however, SOD and CAT activity were not sensitive in the experiment. Show more

Keywords: inhibition rate, antioxidant enzyme, half effect concentration (EC_{50}), sensibility

Citation: Journal of Environmental Sciences, vol. 17, no. 3, pp. 526-528, 2005