Journal of Environmental Sciences - Volume 17, issue 5

Authors: YANG, Shi-ying | CHEN, Ying-xu | LOU, Li-ping | WU, Xiao-na

Article Type: Research Article

Abstract: The effect of Cl^- on photocatalytic degradation (PCD) of pollutants is an important factor since it is ubiquitous in nature. In general, Cl^- showed an inhibition on photodegradation due to its scavenging HO^{&middot;} radicals. In this paper, experiments were carried out to examine the effects of Cl^- on the PCD of Methylene Blue (MB) and Orange II (Oll) in aqueous TiO_2 suspensions under UV light illumination. …It was found that low concentration of Cl^- (< 0.01 mol/L) showed little influence on both dyes, however, high concentration of Cl^- (> 0.10 mol/L) had a very different influence on the decolorization of dyes: a significant inhibition for MB but a great promotion for Oll. In the presence of 0.50 mol/L Cl^- , the rate decreased by 70% for MB while increased 7.5-fold for Oll. Furthermore, two bands in the ultraviolet region of Oll were rapidly broken down. The proposed mechanism was discussed in detail. Show more

Keywords: photocatalytic degradation, TiO_2, dye pollutants, chloride ion, mechanism

Citation: Journal of Environmental Sciences, vol. 17, no. 5, pp. 761-765, 2005

Authors: WEN, Yue-zhong | LIU, Wen-qi | FANG, Zhao-hua | LIU, Wei-ping

Article Type: Research Article

Abstract: Reactive Red 195, which is an azoic anionic dye characterized by the presence of five sulfonic groups and one azoic group, is efficiently removed using chitosan. The increasing chitosan dose had a dramatic positive impact on the achieved color removal, there was approximately a linear relationship between chitosan dose and color removal of dye before color removal reach maximum. Also, the increase of dye concentration led to the increase of chitosan dosage in order to get …the same color removal. 92 mg/L of chitosan dosage was sufficient to achieve complete remove of dye at initial concentration of dye at 200 mg/L. For the higher concentrations of dye, high dosages were necessary to reach complete color removal. On the other hand, the use of adsorption interferents (Fe^{2+} , Na^+ , HCO_3^- and others) can be interesting, addition of ions had effect on the color removal of Reactive Red 195. Comparing with blank, addition of chemical species approximately decreased the color removal except Na^+ and combination of Fe^{2+} + HCO_3^- . However, comparing with Fe^{2+} alone and HCO_3^- alone, combination of Fe^{2+} + HCO^-_3 increased the color removal. Show more

Keywords: chitosan, Reactive Red 195, dye, coagulation, color removal

Citation: Journal of Environmental Sciences, vol. 17, no. 5, pp. 766-769, 2005

Authors: GONG, Chun-ming | Inoue, Koichi | Inanaga, Shunji | Someya, Takashi

Article Type: Research Article

Abstract: Application of compost in agricultural practice could potentially cause contamination of foodstuffs with pathogenic bacteria such as Escherichia coli O157: H7 (E. Coli O157). We investigated pathogenic bacteria in compost collected from the compost facilities, and evaluated the survival of E. coli K12 and O157 in laboratory experiments. Out of 19 compost product samples, coliform bacteria and salmonella were detected in 7 and 3 samples respectively. The number of coliform bacteria was 1.8 × 10^2 …to 2.5 × 10^6 CFU/g dw and that of salmonella was 4.2 × 10^1 to 6.0 × 10^3 CFU/g dw. Moreover, coliform bacteria, fecal coliform, E. coli and salmonella were detected during composting at 54°C to 67°C. The results indicated that moisture content was a very important factor to the heat sensitivity of pathogenic bacteria in compost, E. coli in compost of high moisture content was more sensitive than that in compost of low moisture content, cells harvested in logarithmic phase was more sensitive than these in stationary phase, and E. coli K12 was more sensitive than E. coli O157. Based on the D values, the lethal time of E. coli K12 and O157 from 10^8 to 10^0 CFU/g dw were 16.3 and 28.8 min, respectively, at 60°C in compost with 40% moisture content. However, some E. coli cells survived in composting process at 54°C to 67°C. Water potential (low moisture content) and physiological aspects of bacteria (stationary phase) could explain only in part of the prolonged survival of E. coli in compost, and there should be some other factors that are conducive to bacterial survival in compost. Show more

Keywords: survival, pathogenic bacteria, compost, Escherichia coli, moisture

Citation: Journal of Environmental Sciences, vol. 17, no. 5, pp. 770-774, 2005

Authors: CHEN, Fei-zhou | XIE, Ping | TANG, Hui-juan | LIU, Hong

Article Type: Research Article

Abstract: Effects of Microcystis blooms on the crustacean plankton were studied using enclosure experiments during July–September, 2000. Eight enclosures were set in the hypereutrophic Donghu Lake. Different nutrient concentrations through additional nutrient and sediment in enclosures were expected to result in different abundance of Microcystis. From July to early August, the phytoplankton community was dominated by Chlorophyta, Cryptophyta, Bacillariophyta and Cyanophyta other than Microcystis aeruginosa. M. aeruginosa showed a rapid increase during early …August in all enclosures and predominated. Crustacean plankton was dominated by the herbivorous Moina micrura, Diaphanosoma brachyurum and Ceriodaphnia cornuta, and the predaceous Mesocyclops sp. and Thermocyclops taihokuensis. During the pre-bloom period, the dynamics of M. micrura population appeared to be mainly affected by the predaceous cyclopoids. With the development of Microcystis blooms, such interaction between M. micrura and cyclopoids seemed weakened, especially when the Microcystis biomass was high. But there was no apparent influence on the interaction between Leptodora kindti and its zooplanktonic prey. The density of two cyclopoids decreased with the enhancement of Microcystis. The density decline of M. micrura was caused by both predation and inhibition by Microcystis. The low food availability of other edible phytoplankton during the blooms led to low densities of both C. comuta and D. brachyurum by late August. lt appears that dense Microcystis blooms exert strong negative effects on the herbivorous cladocerans and the predaceous cyclopoids. Show more

Keywords: crustacean plankton, cladocerans, cyclopoids, food availability, Microcystis bloom

Citation: Journal of Environmental Sciences, vol. 17, no. 5, pp. 775-781, 2005

Authors: ZHANG, Wei-ming | CHEN, Jin-long | CHEN, Qun | HE, Min-yang-yang | PAN, Bing-cai | ZHANG, Quan-xing

Article Type: Research Article

Abstract: The adsorption behaviors of 1-naphthol, 1-naphthylamine and 1-naphthol/1-naphthylamine mixtures in water over two macroreticular adsorbents were investigated in single or binary batch systems at 293 K, 303 K and 313 K respectively. All the adsorption isotherms in the studied systems can be adequately fitted by Langmuir model. In the case of aminated macroreticular adsorbent NDA103, 1-naphthol is adsorbed to a larger extent than 1-naphthylamine; while, the opposite trend is found for nonpolar macroreticular …adsorbent NDA100. It is noteworthy that at higher temperature (303 K and 313 K), the total uptake amounts of 1-naphthol and 1-naphthylamine in all binary-component systems are obvious larger than the pure uptake amounts in single-component systems, which is presumably due to the cooperative effect primarily arisen from the hydrogen-bonding interaction between the loaded 1-naphthol and 1-naphthylamine molecules. The simultaneous adsorption systems were confirmed to be helpful to the selective adsorption towards 1-naphthol according to the larger selective index. Show more

Keywords: macroreticular adsorbent, adsorption, 1-naphthol, 1-naphthylamine, cooperative effect

Citation: Journal of Environmental Sciences, vol. 17, no. 5, pp. 782-785, 2005

Authors: OUYANG, Bin | FANG, Hao-jie | ZHU, Cheng-zhu | DONG, Wen-bo | HOU, Hui-qi

Article Type: Research Article

Abstract: The rate constants of reactions between the SO^{&middot;-}_4 radical and some common anions in atmospheric aqueous droplets e.g. Cl^- , NO_3^- , HSO_3^- and HCO_3^- were determined using the laser flash photolysis technique. Absorption spectra of SO^{&middot;-}_4 and the product radicals were also reported. The chloride ion was evaluated among all the anions to be the most efficient scavenger of …SO^{&middot;-}_4 . The results may supply useful information for a better understanding of the vigorous radical-initiated reactions in atmospheric aqueous droplets such as clouds, rains or fogs. Show more

Keywords: sulfate radical, common anions, atmospheric aqueous-phase chemistry, radical chemistry

Citation: Journal of Environmental Sciences, vol. 17, no. 5, pp. 786-788, 2005

Authors: ZHU, Ren-bin | SUN, Li-guang | ZHAO, San-ping | XIE, Zhou-qing | LIU, Xiao-dong | YIN, Xue-bin

Article Type: Research Article

Abstract: Methane flux from the omithogenic soils was preliminarily measured by closed chamber method on Xi-sha atoll, South China Sea during March 10 to April 11, 2003 for the first time. The CH_4 flux ranged from −226.7μg/(m^2 ·h) to 226.3μg/(m_2 ·h) at the observation sites on Dong Island. High atmospheric CH_4 consumption was observed from the ornithogenic soils on sunny days. CH_4 uptake rates showed …the highest value after the midday and they had a strong positive correlation with soil temperatures. Under the same weather conditions, the CH_4 fluxes were also observed from the intact and disturbed soils on Yongxing Island. Results showed that the intact soils with natural vegetation also showed high atmospheric CH_4 consumption and the average flux was −141.8μg/(m^2 ·h). However, disturbed soils via anthropogenic reclamation showed CH_4 emissions and the average flux was 441.7μg/(m_2 ·h). Therefore land use changes may have an important effect on the CH_4 fluxes from the tropical ornithogenic soils. In addition, different observation sites show a high spatial variation in CH_4 fluxes. The wetland in salt marsh showed the CH_4 emission on Dong Island, and the dry soil sites all showed high atmospheric CH_4 consumption, suggesting that CH_4 fluxes were predominantly controlled by soil water regime. The effects of soil chemical properties on CH_4 fluxes were also analyzed and discussed in this paper. Show more

Keywords: methane, flux, South China Sea, omithogenic soil, Xi-sha atoll

Citation: Journal of Environmental Sciences, vol. 17, no. 5, pp. 789-793, 2005

Authors: CUI, You-wei | PENG, Yong-zhen | GAN, Xiang-qing | YE, Liu | WANG, Ya-yi

Article Type: Research Article

Abstract: The principal aim of this paper is to develop an approach to realize stable biological nitrogen removal via nitrite under normal conditions. Validation of the new method was established on laboratory-scale experiments applying the sequencing batch reactor (SBR) activated sludge process to domestic wastewater with low C/N ratio. The addition of sodium chloride (NaCl) to influent was established to achieve nitrite build-up. The high nitrite accumulation, depending on the salinity in influent and the application …duration of salt, was obtained in SBRs treating saline wastewater. The maintenance results indicated that the real-time SBRs can maintain stable nitrite accumulation, but conversion from shorter nitrification-denitrification to full nitrification-denitrification was observed after some operation cycles in the other SBR with fixed-time control. The presented method is valuable to offer a solution to realize and to maintain nitrogen removal via nitrite under normal conditions. Show more

Keywords: nitrite accumulation, salt selective inhibition, real-time control of nitrification, biological nitrogen removal via nitrite, nitrite-oxidizers, ammonium-oxidizers

Citation: Journal of Environmental Sciences, vol. 17, no. 5, pp. 794-797, 2005

Authors: TIAN, Bing-hui | FAN, Bin | PENG, Xian-jia | LUAN, Zhao-kun

Article Type: Research Article

Abstract: In order to improve the flocculation efficiency of polydiallyldimethylammonium chloride (PDADMAC), high molecular weight PDADMAC should be prepared from high purity diallyldimethylammonium chloride (DADMAC) monomers. In this paper, a cleaner method with microwave irradiation and alkali solidification was proposed for preparing high pure DADMAC by selective heating under low temperature, and the prepared high purity DADMAC is characterized using FTIR and atomic absorption spectrometry. The new method provides a solution to the …key technical problem of PDADMAC synthesis. Comparing with the conventional methods, the results showed that the advantages of the novel synthesis include: (a) high purity DADMAC is improved from 57% to 71%; (b) reaction time of tertiary amine preparation is shortened from 6 h to 7 min; (c) water instead of acetone was used as reaction medium; (d) toxic by-products, wastewater and waste gas are eliminated. Flocculant made from the synthesized high purity DADMAC monomers was proved more efficient in flocculation tests. Show more

Keywords: diallyldimethylammonium chloride, microwave irradiation, flocculant, cleaner process

Citation: Journal of Environmental Sciences, vol. 17, no. 5, pp. 798-801, 2005

Authors: Akmal, Muhammad | WANG, Hai-zhen | WU, Jian-jun | XU, Jian-ming | XU, De-fu

Article Type: Research Article

Abstract: Heavy metal pollution has received increasing attention in recent years mainly because of the public awareness of environmental issues. In this study we have evaluated the effect of cadmium (Cd) on enzymes activity, substrate utilization pattern and diversity of microbial communities in soil spiked with 0, 20, 40, 60, 80, and 100 mg/kg Cd, during 60 d of incubation at 25°C. Enzyme activities determined at 0, 15, 30, 45, and 60 d after heavy metal application …(DAA) showed marked declines for various Cd treatments, and up to 60 DAA, 100 mg/kg Cd resulted in 50.1%, 47.4%, and 39.8% decreases in soil urease, acid phosphatase and dehydrogenase activities, respectively to control. At 60 DAA, substrate utilization pattern of soil microbial communities determined by inoculating Biolog ECO plates indicated that Cd addition had markedly inhibited the functional activity of soil microbial communities and multivariate analysis of sole carbon source utilization showed significantly different utilization patterns for 80 and 100 mg/kg Cd treatments. The structural diversity of soil microbial communities assessed by PCR-DGGE method at 60 DAA, illustrated that DGGE patterns in soil simplified with increasing Cd concentration, and clustering of DGGE profiles for various Cd treatments revealed that they had more than 50% difference with that of control. Show more

Keywords: enzyme activity, microbial community, soil, cadmium

Citation: Journal of Environmental Sciences, vol. 17, no. 5, pp. 802-807, 2005