Journal of Environmental Sciences - Volume 18, issue 3

Authors: WU, Gen-fu | WU, Xue-chang | XUAN, Xiao-dong | ZHOU, Xue-ping

Article Type: Research Article

Abstract: There has always been a great need for simple and accurate bioassays for evaluating nutrient limitation in aquatic ecosystems. Whereas organic carbon is usually considered to be the limiting nutrient for microbial growth in many aquatic ecosystems, there are, however, many water sources that are limited by phosphorus or nitrogen. A method named "nitrogen fixing bacterial growth potential" (NFBGP) test, which is based on pre-culturing ofautochthonous (target) microorganisms was described. The method was applied to evaluate …phosphorus or nitrogen nutrient limitation in lake and sewage water samples using an isolate of the nitrogen fixing bacterium, Azorhizobium sp. WS6. The results corresponded well to those from the traditional algal growth potential (AGP) test and the bacterial regrowth potential (BRP) test, suggesting that the NFBGP test is a useful supplementary method for evaluating the limiting nutrient, especially phosphorus, in an aquatic environment. Show more

Keywords: environment monitoring, nitrogen fixing bacterium, limiting nutrient, phosphorus, growth potential

Citation: Journal of Environmental Sciences, vol. 18, no. 3, pp. 537-542, 2006

Authors: WANG, You | TANG, Xue-xi | YANG, Zhen | YU, Zhi-ming

Article Type: Research Article

Abstract: We collected the diseased blades of Laminaria japonica from Yantai Sea Farm from October to December 2002, and the alginic acid decomposing bacterium on the diseased blade was isolated and purified, and was identified as Alteromonas espejiana. This bacterium was applied as the causative pathogen to infect the blades of L. japonica under laboratory conditions. The aim of the present study was to identify the effects of the bacterium on the growth of L. japonica, and …to find the possibly effective mechanism. Results showed that: (1) The blades of L. japonica exhibited symptoms of lesion, bleaching and deterioration when infected by the bacterium, and their growth and photosynthesis were dramatically suppressed. At the same time, the reactive oxygen species (ROS) generation enhanced obviously, and the relative membrane permeability increased significantly. The contents of malonaldehyde (MDA) and free fatty acid in the microsomol membrane greatly elevated, but the phospholipid content decreased. Result suggested an obvious peroxidation and deesterrification in the blades of L. japonica when infected by the bacterium. (2) The simultaneous assay on the antioxidant enzyme activities demonstrated that superoxide dismutase (SOD) and catalase (CAT) increased greatly when infected by the bacterium, but glutathione peroxidase (Gpx) and ascorbate peroxidase (APX) did not exhibit active responses to the bacterium throughout the experiment. (3) The histomorphological observations gave a distinctive evidence of the severity of the lesions as well as the relative abundance in the bacterial population on the blades after infection. The bacterium firstly invaded into the endodermis of L. japonica and gathered around there, and then resulted in the membrane damage, cells corruption and ultimately, the death of L. japonica. Show more

Keywords: Laminaria japonica, alginic acid decomposing bacterial, infection, growth, mechanism

Citation: Journal of Environmental Sciences, vol. 18, no. 3, pp. 543-551, 2006

Authors: JIANG, Xiao-dong | WANG, Gui-zhong | LI, Shao-jing

Article Type: Research Article

Abstract: Many estuarine and coastal planktonic copepods depend on the hatching of benthic resting eggs for recruitment of nauplii to the water column population. The potential effects of two organochlorine pesticides, hexchloriobinzene (HCH) and dichlorodiphenyltrichloroethane (DDT), on the recruitment of Acartia pacifica nauplii from benthic resting eggs in the seabed of Xiamen Bay were experimentally investigated. The abundance of A. pacifica nauplii hatched from the sediment significantly decreased with the increase of pesticide …concentration. Trimmed Spearman-Karber analysis gave sediment 96-h LC_{50} values were 84.81 ng/g for HCH, and 157.94 ng/g for DDT. The median AI (AI_{50} ) was −0.77, which suggested that the combined effect of HCH and DDT showed a weak effect than individual effects. There was a positive relationship between mortality and exposure time in DDT treatment, while the relationship was not significant in HCH treatment. The results suggest that organochlorine pesticides can reduce recruitment of A. pacifica nauplii from benthic resting eggs to planktonic population. Show more

Keywords: organochlorine pesticide, resting egg, recruitment, A cartia pacifica

Citation: Journal of Environmental Sciences, vol. 18, no. 3, pp. 552-556, 2006

Authors: LIU, Shou-xin | SUN, Cheng-lin

Article Type: Research Article

Abstract: Preparation ofphotocatalytic regenerationable activated carbon (AC) is the key step for the practical application of in situ regeneration of exhausted AC. A novel photocatalytic regenerationable AC was prepared by sol-gel TiO_2 in this work. The adsorption and regeneration performance of TiO_2 /AC were evaluated using phenol as model compound. Scanning electron microscope (SEM) and nitrogen (77 K) adsorption isotherm were used to determine the surface area, pore structure and the …distribution of TiO_2 . The results showed that with the increase of TiO_2 loading, adsorption capacity of TiO_2 /AC decreased and the regeneration efficiency increased. The photocatalytic regenerationable AC with suitable TiO_2 loading (2 wt%) exhibited suitable adsorption capacity and regeneration efficiency. TiO_2 located mainly in the entrance of macro-pore of carbon. The prepared TiO_2 /AC exhibited similar surface structure and pore structure with material carbon. Show more

Keywords: photocatalytic regenerationable, activated carbon, titanium dioxide

Citation: Journal of Environmental Sciences, vol. 18, no. 3, pp. 557-561, 2006

Authors: WANG, Yu-ping | WANG, Lian-jun | PENG, Pan-ying

Article Type: Research Article

Abstract: TiO_2 sol was prepared by sol-gel technique with tetrabutyl titanate as precursor. Supported TiO_2 catalysts on activated carbon were prepared by soak and sintering method. The aggregation of nano-TiO_2 particles can be effectively suppressed by added polyethylene glycol (PEG) as a surface modifier. The average particle diameter of TiO_2 , specific surface area and absorbability of catalyst can be modified. Based on characteristics of the …TiO_2 photocatalyst with XRD, specific surface area, adsorption valves of methylene blue and the amount of TiO_2 supported on the activated carbon, the photocatalytic degradation of L-acid was studied. The effect of the factors, such as pH of the solution, the initial concentration of L-acid on the photocatalytic degradation of L-acid, were studied also. It was found that when the pH of the solution is 1.95, the amount ofphotocatalyst is 0.5 g, the concentration of the L-acid solution is 1.34 × 10^{-3} mol/L and the illumination time is 7 h, the photocatalytic degradation efficiency of L-acid can reach 89.88%. The catalyst was reused 6 times and its degradation efficiency hardly changed. Show more

Keywords: L-acid, activated carbon, supported TiO_2, photodegradation

Citation: Journal of Environmental Sciences, vol. 18, no. 3, pp. 562-566, 2006

Authors: ZHOU, Chun-qiong | DENG, Xian-he | PAN, Zhao-qun

Article Type: Research Article

Abstract: Absorption and catalytic oxidation of nitric oxide can be achieved by using cobalt(III) ethylenediamine (Co(en)_3^{3+} ). When simultaneous absorbing SO_2 and NO, the precipitation of CoO_2 (SO_3 )_3 will be yielded and the NO removal will be decreased. A new catalyst system using Co(eh)_3^{3+} coupled with urea has been developed to simultaneous remove NO and SO_2 in the flue gas. NO is …absorbed and catalytically oxidized to nitrite and nitrate by Co(en)_3^{3+} . The dissolved oxygen in scrubbing solution from the feed stream acts as oxidant. Urea restrains the precipitation of CoO_2 (SO_3 )_3 by oxidizing SO_3^{2-} to SO_4^{2-} as CoSO_4 is more soluble in water. The experimental results proved that nearly all SO_3^{2-} can be oxidized to SO_4^{2-} and the high NO and SO_2 removal could be obtained with the new system. The NO removal is influenced by gas flow rate, the concentration of Co(en)_3^{3+} and urea in the absorption solution, the temperature of the scrubbing solution and the content of oxygen in the flue gas. The low gas flow rate is favorable to increase the NO removal. The experiments proved that the NO removal could be maintained at more than 95% by the system of 0.02 mol/L Co(eh)_3^{3+} and 1% urea at 50°C with 10% O_2 in the flue gas. Show more

Keywords: simultaneous removing SO_2 and NO, Co(en)_3^{3+}, urea, SO_3^{2-} oxidation

Citation: Journal of Environmental Sciences, vol. 18, no. 3, pp. 567-571, 2006

Authors: ZHANG, An-ping | LUO, Fan | CHEN, Sheng-wen | LIU, Wei-ping

Article Type: Research Article

Abstract: Cyclodextrins (CDs), with hydrophobic interior cavity and hydrophilic external surface, are capable of accelerating or inhibiting chemical degradation of organophosphorus pesticides through forming inclusion complexes between CDs and pesticides. This work evaluated the effects of CDs on hydrolysis of malathion in an attempt to assess their potential application in environmental approach. β-CD and its two derivatives, randomly methylated β-CD (RAMEB) and hydroxypropyl β-CD (HP-β-CD), were tested. It was found that RAMEB could …inhibit the hydrolysis of malathion, and this was the function of pH and temperature, the inhibitory effects increase with increasing concentration of RAMEB and elevating temperature between 15 and 35°C. On the other hand, β-CD and HP-β-CD have little or no stabilizing effects on malathion at all pH and temperature studied, except that the large concentration of β-CD and HP-β-CD can mildly reduce hydrolysis of malathion. Both 2 mol/L and 5 mol/L urea increase the inhibitory effects of RAMEB on hydrolysis of malathion at 25°C, pH 9.0. Show more

Keywords: cyclodextrin, malathion, hydrolysis, urea

Citation: Journal of Environmental Sciences, vol. 18, no. 3, pp. 572-576, 2006

Authors: YAN, Jian-hua | TAN, Zhong-xin | JIANG, Xue-guang | CHI, Yong | CEN, Ke-fa

Article Type: Research Article

Abstract: Dyestuff residue, a type of hazardous waste, is incinerated in the tubular furnace, and thermodynamic equilibrium model is used to calculate and analyze the chlorine behavior. The HCl emission and its effects on the behaviors of heavy metals are studied. Meanwhile, the effects of three dechlorine reagents are predicted at a high temperature. Results show that HCl emission is dependent on incineration temperature. The HCl evaporated mainly derives from the organic chlorine. Under the working condition …of 500–900°C, the main products of Hg, Pb, Cu, Ni, Zn, and Mn in reaction with HCl are HgCl_2 (g), PbCl_4 (g), PbCl_2 (g), (CuCl)_3 (g), NiCl_2 (s), NiCl_2 (g), ZnCl_2 (s), ZnCl_2 (g), Zn(g), MnCl_2 (s), and MnCl_2 (g), respectively. Among the three dechlorine reagents, CaCO_3 is optimal to remove chlorine at high temperature, little of HCl is released below 800°C, whereas Fe_3 O_4 is unstable at high temperature. Show more

Keywords: hazardous waste, thermodynamic equilibrium model, HCl, heavy metals, dechlorine reagents

Citation: Journal of Environmental Sciences, vol. 18, no. 3, pp. 577-582, 2006

Authors: ZHANG, Hua | HE, Pin-jing | SHAO, Li-ming | FENG, Jun-hui | CAO, Qun-ke

Article Type: Research Article

Abstract: Increasing attention has been paid to air pollution control (APC) residues in China recently due to the rising proportion of waste incineration and the hazardous characteristics of the residues, among which heavy metal leaching toxicity plays an important role. Leaching behavior and potential risk of Pb and Zn in the APC residues from a Shanghai municipal solid waste (MSW) incinerator was studied, based on the leaching tests under different conditions and theoretical calculation using a geochemical …thermodynamic equilibrium model MINTEQA2. Results showed that, extractant species and liquid to solid (L/S) ratio predominantly controlled the leaching toxicity of Pb and Zn, while ionic strength, vibration method and leaching time had less effect on the metals release. Leachate/final pH determined the metal leaching behavior, which changed the speciation of heavy metals in the extraction system. The equilibrium aqueous speciation, precipitation-dissolution of Pb and Zn was investigated according to the model computation, which was well in agreement with the experimental results. Show more

Keywords: leaching behavior, air pollution control residues, MINTEQA2, incineration plant, heavy metals

Citation: Journal of Environmental Sciences, vol. 18, no. 3, pp. 583-586, 2006

Authors: LI, Yu-ying | ZHENG, Xi-lai | LI, Bing

Article Type: Research Article

Abstract: There were six high diesel oil degrading bacteria strains isolated from the oil contaminated soil that collected from Linzi City. The strain Y1 was able to produce biosurfactant rhamnolipid when cultivated on diesel oil as carbon source. The critical micelle concentrations (CMC) of rhamnolipid in water and in the soil were measured respectively according to the correlation between the surface tension of the medium and the added rhamnolipid concentration. The results showed that the CMC of …rhamnolipid in water was 65 mg/L, and was 185 mg/L in soil. The tests on diesel oil biodegradation were conducted with the addition of different concentrations of rharnnolipid in water and in soil respectively. When 0.01% rhamnolipid was added to water, the diesel oil degradation was enhanced. On the contrary, when the same concentration of rhamnolipid was added to the soil, the degradation of diesel oil was inhibited. The results suggested that the rhamnolipid could enhance the diesel oil biodegradation, indicating that the concentration of rhamnolipid was higher than the corresponding CMC in the medium. Kinetics parameters for the diesel oil biodegradation parameters such as biodegradation constant (λ), coefficient of correlation (r) and half life (t_{1/2} ) in both tests were numerically analyzed in this paper, indicating that the moderate concentration of rhamnolipid in the medium could not only enhance the extent of diesel oil biodegradation but also shorten the time for oil remediation. Show more

Keywords: biosurfactant, diesel oil, remediation, bacteria

Citation: Journal of Environmental Sciences, vol. 18, no. 3, pp. 587-590, 2006