Journal of Environmental Sciences - Volume 17, issue 6

Authors: LIN, Kun-de | YUAN, Dong-xing

Article Type: Research Article

Abstract: This work presents laboratory studies on the degradation of triazophos in intertidal sediment. The overall degradations were found to follow the first-order decay model. After being incubated for 6 d, the percentage of degradations of triazophos in unsterilized and sterilized sediments were 94.5% and 20.5%, respectively. Between the temperatures of 15°C and 35°C, the observed degradation rate constant (k_{obsd} ) enhanced as the incubation temperature increased. Triazophos in sediment degraded faster …under aerobic condition than under anaerobic one. The water content of sediment had little influence on the degradation when it was in the range of 50%–100%. The values of k_{obsd} decreased with increasing initial concentration of triazophos in sediment, which could result from the microorganism inhibition by triazophos. Four major degradation products, o, o-diethyl phosphorothioic acid, monoethyl phosphorothioic acid, phosphorothioic acid, and 1-phenyl-3-hydroxy-1,2,4-triazole, were tentatively identified as their corresponding trimethylsilyl derivatives with a gas chromato-graphy-mass spectrometer. The possible degradation pathway of triazophos in intertidal sediment was proposed. The results revealed that triazophos in intertidal sediment was relatively unstable and could be easily degraded. Show more

Keywords: triazophos, degradation, intertidal sediment

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 933-936, 2005

Authors: JIN, Xiang-can | CHU, Zhao-sheng | YI, Wen-li | HU, Xiao-zhen

Article Type: Research Article

Abstract: The growth processes of Microcystis aeruginosa (FACHB-41) in simulated Taihu Lake water with different phosphorus concentrations were investigated using laboratory microcosms. The algal biomass increased with the increase of phosphorus concentration when it was lower than 0.445 mg/L, while the dissolved oxygen (DO) and pH increased, dissolved inorganic nitrogen (DIN) and light intensity underwater(I) decreased. Responding to the changes of the "environmental factors", the cellular carbohydrate and its ratio to cellular protein …decreased generally as phosphorus increased. However, when phosphorus concentration was higher than 1.645 mg/L, the biomass, the "environmental factors", the cellular carbohydrate and its ratio to cellular protein did not change likewise. Since the environmental factors and the physiological and biochemical responses are important factors, the change of environmental factors and cell physiology and biochemistry induced by phosphorus may become the key factors that steer the growth and dominance of Microcystis under certain conditions. To sum up, phosphorus not only stimulate the growth of Microcystis directly by supplying nutrient element, but also has complex interactions with other "environmental factors" and play important roles in the growth processes of Microcystis. Show more

Keywords: Microcystis aeruginosa, microcosm, phosphorus

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 937-941, 2005

Authors: FU, Jian-feng | JI, Min | AN, Ding-nian

Article Type: Research Article

Abstract: The degradation of fulvic acid (FA) by nanoparticle TiO2 in a submerged membrane photocatalysis (SMPC) reactor was studied. In this reactor, photocatalytic oxidation and membrane separation co-occured. The continuous air supplier provided O_2 for the photocatalytical reaction and mixed the solution through an airflow controller. The particle TiO_2 could automatically settle due to gravity without particle agglomeration so it could be easily separated by microfiltration (MF) membrane. It …was efficient to maintain high flux of membranes. The effects of operational parameters on the photocatalytic oxidation rate of FA were investigated. Results indicated that photocatalyst at 0.5 g/L and airflow at 0.06 m^3 /h were the optimum condition for the removal of fulvic acid, the removal efficiency was higher in acid media than that in alkaline media. The effects of different filtration duration on permeate flux rate of MF with P25 powder and with nanoparticle TiO_2 were compared. Experimental results indicated that the permeate flux rate of MF was improved and the membrane fouling phenomenon was reduced with the addition of nanoparticle TiO_2 catalyst compared with conventional P25 powder. Therefore, this submerged membrane photocatalysis reactor can faciliate potential application of photocatalytic oxidation process in drinking water treatment. Show more

Keywords: fulvic acid, microfiltration membrane, nanoparticle TiO_2, photocatalytic oxidation, reactor

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 942-945, 2005

Authors: XU, Min | ZENG, Guang-ming | XU, Xin-yi | HUANG, Guo-he | SUN, Wei | JIANG, Xiao-yun

Article Type: Research Article

Abstract: Bayesian regularized BP neural network (BRBPNN) technique was applied in the chlorophyll-a prediction of Nanzui water area in Dongting Lake. Through BP network interpolation method, the input and output samples of the network were obtained. After the selection of input variables using stepwise/multiple linear regression method in SPSS 11.0 software, the BRBPNN model was established between chlorophyll-a and environmental parameters, biological parameters. The achieved optimal network structure was 3-11-1 with the correlation …coefficients and the mean square errors for the training set and the test set as 0.999 and 0.00078426, 0.981 and 0.0216 respectively. The sum of square weights between each input neuron and the hidden layer of optimal BRBPNN models of different structures indicated that the effect of individual input parameter on chlorophyll-a declined in the order of alga amount > secchi disc depth (SD) > electrical conductivity (EC). Additionally, it also demonstrated that the contributions of these three factors were the maximal for the change of chlorophyll-a concentration, total phosphorus (TP) and total nitrogen (TN) were the minimal. All the results showed that BRBPNN model was capable of automated regularization parameter selection and thus it may ensure the excellent generation ability and robustness. Thus, this study laid the foundation for the application of BRBPNN model in the analysis of aquatic ecological data (chlorophyll-a prediction) and the explanation about the effective eutrophication treatment measures for Nanzui water area in Dongting Lake. Show more

Keywords: Dongting Lake, chlorophyll-a, Bayesian regularized BP neural network model, sum of square weights

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 946-952, 2005

Authors: WEI, Zi-min | XI, Bei-dou | WANG, Shi-ping | XU, Jing-gang | ZHOU, Yu-yan | LIU, Hong-liang

Article Type: Research Article

Abstract: Dissolved organic matter (DOM) of municipal solid waste (MSW) consists of minerals, water, ash and humic substances, and is known to enhance plant growth. In this study, inoculating microbes (ZJ, MS) were used in municipal solid wastes composting, and composting implemented a industrialized technology. During composting, dissolved organic matter was extracted from the compost and purified. The spectral characteristics of dissolved organic matter was determined by fluorescence emission, excitation, and synchronous spectroscopy. …Fluorescence emission, excitation, and synchronous spectra characterized by different relative fluorescent intensities and peaks over time. Fluorescence spectra were similar to that of fulvic acid in sewage sludge, indicating the presence of dissolved organic matter with aromatic structures and a high degree of molecular polymerization. Compared with the controls with no microbial inoculation, the microbe-inoculated treatments exhibited the increase of aromatic polycondensation, in the following order: MS + ZJ > ZJ > MS > CK. Show more

Keywords: MSW composting, dissolved organic matter (DOM), inoculating microbes, fluorescence spectra

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 953-956, 2005

Authors: GAO, Ding | ZHENG, Guo-di | CHEN, Tong-bin | LUO, Wei | GAO, Wei | ZHANG, Yi-an | LI, Yan-xia

Article Type: Research Article

Abstract: The potential toxicity risks from heavy metals depend on their chemical speciation. The four stages of the Tessier sequential extraction method were employed to investigate changes in heavy metal speciation (Cu, Zn, and Cd) of sewage sludge during forced aeration composting, and then to identify whether the composting process would reduce or enhance their toxicities. Throughout the composting process, the exchangeable, carbonate-bound, Fe-Mn oxide-bound, and organic matter-bound fractions of Cu were converted …to the residual Cu fraction. The organic matter-bound Cu fraction greatly contributed to this transformation. Residual Zn fraction was transformed to the Fe-Mn oxide-bound and organic matter-bound fractions after composting. The residual Zn fraction was a major contributor to the organic matter-bound Zn fraction. The availability of Cu and Zn was reduced by composting such that the risk of heavy metal toxicity decreased with prolonged treatment times. Additionally, attention should be paid to the increased availability of Cd in sewage sludge after composting treatment. Show more

Keywords: composting, distribution, heavy metal, sewage sludge, speciation

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 957-961, 2005

Authors: LI, Jiu-hai | PAN, Gen-xing

Article Type: Research Article

Abstract: In the present study, the sorption of pyrene on two kinds of bulk paddy soils, Gleyic Stagnic Anthrosols, and Ferric accumulic Stagnic Anthrosols as well as their particle-size fractions was investigated. The sorption isotherms fitted well with Freundlich equation. For both soils, the clay fraction (<2μm) and coarse sand fraction (2000–250μm) had higher sorption capacity than fine sand fraction (250–20μm) and silt fraction (20–2μm). The logK_{oc} values obtained of each …soil and its particle-size fractions were similar, proving that SOM content was a key factor affecting pyrene sorption. The Km_d values showed a significant correlation with contents of dithionite-extractable Fe in both paddy soils and a good relationship with CEC in Gleyic Stagnic Anthrosols, indicating possible effects of surface properties of particle-size fractions on the sorption of pyrene. Show more

Keywords: paddy soil, particle-size fraction, PAHs, sorption

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 962-965, 2005

Authors: DOU, Jun-xia | ZHANG, Yi-ping | FENG, Zong-wei | LIU, Wen-jie

Article Type: Research Article

Abstract: The effects of canopy development, solar angle, and weather conditions on temporal variation in photosynthetic photon flux density (PPFD) at three heights within a tropical rain forest canopy in Xishuangbanna, China, were examined. PPFD was measured every second and stored as 10-min averages from 1 December 2002 to 30 November 2003. PPFD variability was examined at three different tempcral scales. Specific days in March, September, and December with clear and overcast sky conditions were selected to …separate the effects of leaf area index (LAI) and solar angle on diumal variability. On both clear and overcast days, mean daily average PPFD was significantly different between March and September at all heights, except 10 m on clear days, suggesting that LAI directly influences PPFD. In contrast, the differences in daily average PPFD among three heights between September and December were likely due to variation in solar angle. In addition, daily average PPFD at all locations were significantly lower under overcast than clear sky conditions in March, September and December. Over the year-long study, the mean daily total PPFD at 21 m, 10 m and 4 m was 2.8, 2.7 and 0.7 mol/(m^2 ·d), which accounted for 9.7%, 9.4% and 2.4% of the daily PPFD above the canopy, respectively. Significant differences in mean daily total PPFD occurred at the same heights among different seasons, and diurnal, day-to-day and seasonal PPFD varied at different heights within the canopy. The possible effects of light variability on physiological and morphological responses of plants are discussed. Show more

Keywords: photosynthetic photon flux density, temporal light variability, tropical seasonal rain forest canopy, Xishuangbanna

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 966-969, 2005

Authors: LI, Zhi-an | ZOU, Bi | XIA, Han-ping | DING, Yong-zhen | TAN, Wan-neng | MA, Zhen-rong

Article Type: Research Article

Abstract: The effects of fertilizers and water content on N_2 O emission were studied using the three most typical plantation soils. Soil incubations were performed and fertilization and water content treatments were designed. At 25% of saturated water content (SWC), N_2 O emissions from the soil treated with urea, KNO_3 , (NH_4 )_2 SO_4 and KH_2 PO_4 were compared at application …rates of 0, 100, 200, 300 and 500 kg/hm^2 . At 80% of SWC, similar experiments were carried out but at only one application rate (500 kg/hm^2 ). N_2 O emissions at various water contents (20%, 35%, 50%, 65%, 80% and 100% of SWC) were studied. At low water content (25% of SWC), neither nitrogen nor phosphorus (or potassium) fertilizers led to a high level of N_2 O emission, which generally ranged from 2.03 to 29.02μg/(m^2 ·h). However, at high water content (80% SWC), the fertilizers resulted in much greater N_2 O emission irregardless of soil tested. The highest NO_2 emission rates after 24 h of water addition were 1233μg/(m^2 ·h) for S. superba soil, 1507μg/(m^2 ·h) for P. elliottii soil and 1869μg/(m^2 ·h) for A. mangium soil restively. N_2 O emission from soils treated with urea, (NH_4 )_2 SO_4 and KH_2 PO_4 immediately dropped to a low level but steadily increased to a very high level for the soil treated with KNO_3 . High NO_3^- content was a basis of high level of N_2 O emission. N_2 O emission rates from soils peaked shortly after flooding, rapidly dropping to a very low level in soil from non-legume plantations, but lasting for a relatively long period in soil from legume plantations. When soil water content increased equaling to or higher than 65%, the accumulated N_2 O emission over a period of 13 d ranged from 20.21–29.78 mg/m^2 for S. superba, 30.57–70.12 mg/m^2 for P. elliottii and 300.89–430.51 mg/m^2 for A. mangium. The critical water content was 50% of SWC, above which a high level of N_2 O emission could be expected, and below which very little N_2 O emissions were detected. The results suggest that, at low water content (<50% of SWC), the fertilization practice is safe with regard to N2O emissions, but at high water content (>50% of SWC), nitrogen fertilizer in the form of nitrate could yield a 100-fold increase in N_2 O emissions. Legume plantations like A. mangium should be avoided in low lands which could easily suffer from flooding or poor drainage. Show more

Keywords: N_2O, plantation, south China, Acacia mangium, Pinus elliottii, Schima superba

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 970-976, 2005

Authors: ZHOU, Zhen-feng | LIU, Kang | WANG, Xiao-rong | HUANG, Shi-hong

Article Type: Research Article

Abstract: To understand pollution level and possible sources ofatmospheric fine particulates in rural areas of southern Jiangsu Province of China, samples of PM_{2.5} were collected and analyzed in Xueyan Town and Taihu Lake Station over three seasons from July 2002 to January 2003. The mass concentrations of PM_{2.5} and 14 principal component elements were obtained. The results showed that pollution of PM_{2.5} was serious and the concentration levels of S, Zn, …Pb and As were similar to city. There are different seasonal distribution laws of pollutant elements in PM_{2.5} between two sampling sites, probably due to contribution of local sources, medium or long distance transportation of fine particulates and complicated meteorological conditions. The enrichment levels of S, Zn, Pb, As, K were high, reflecting the influence of anthropogenic activities. Particularly enrichment level of S was much higher in summer, which was probably related to meteorological condition. The result of principal components analysis showed major sources of PM_{2.5} included crustal resuspension, coal burning, metal processing industry or waste incineration, vehicular emission, which suggests anthropogenic activities is of important influence on PM_{2.5} in rural areas of southem Jiangsu Province. Show more

Keywords: rural areas, PM_{2.5}, sources, enrichment factor, principal components analysis

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 977-980, 2005