Papers by Author: Ji Wei Hu

Abstract: This paper reports a study on vertical distribution characteristics of phosphorus speciation in samples collected at four sites from Baihua Lake, based on the Standards, Measurements and Testing (SMT) programme. In this study, the total phosphorus (TP) concentrations of these sediments samples varied from 944.86 to 2591.56 mg/kg and inorganic phosphorus (IP) was the main phosphorus fraction. For this heavily contaminated sediment, the IP mainly consisted of the Fe/Al-P. The vertical variation of the phosphorus had a tendency to decrease with the depth at sites JYS and YPZ. Since the concentrations of the TP in sediments were high and the phosphorus release potential and bioavailability were significant, the lake is still facing an ecological risk.

Abstract: Both single pollution index and integrated pollution index methods were employed in the present research to assess the heavy metals pollution of soil in the three Rosa roxburghii Tratt Planting Bases (located in Qianxi County and Qixingguan region in Bijie, Longli County in Qiannan), the baseline values of heavy metals in soils in Guizhou Province, Environmental Quality Standard for Soils (GB15618-1995) and Conditions of Green Food-tech0.nical Environmental Quality for Production Area (NY/T391-2000 and GB/T18407.1-2001) were applied as references. National Food Safety Standard-Contaminants in foods was applied to evaluate Rosa roxburghii Tratt fruits. The results suggest that the studied soil samples conformed to Environmental Quality Second Level Standard for Soils and Green Food-technical Conditions. The overall quality of the soil conditions was uncontaminated, but point source pollution phenomenon existed. Hg, Pb and Cu pollution were the main factors contributing to the rise in comprehensive pollution index from the three Rosa roxburghii Tratt Planting bases. It was found that levels of As and Cu did not exceed the limited standard of the soil，while Hg, Cr, Cd and Pb exceeded the standard in different degrees in studied Rosa roxburghii Tratt planting bases. The rates of excessive quota of Hg, Cr, Cd and Pb in the studied Rosa roxburghii Tratt fruits was 6.67%, 13.33%, 73.33% and 100%, respectively. The mean accumulation coefficient of Cd for Rosa roxburghii Tratt fruits was up to 1.20. The mean accumulation coefficients for concerned heavy metals were in the order of Cd > Cu > Pb > Hg > As> Cr. The relationships between concentrations of heavy metals in soil, leaf and stem samples were weak. However, significant correlations were found between concentrations of As in soil and leaf samples (r = 0.928), and concentrations of Cr between in soil samples and Cr in leaf samples (r = 0.733).

Abstract: The quantitative structure property relationship (QSPR) study was performed in this work to develop models to predict the normalized reaction rate constants for the reductive debromination of polybrominated diphenyl ethers (PBDEs) by zero-valent iron (ZVI). In order to consider the solvent effect, conductor-like polarizable continuum model (CPCM) was applied to optimize the geometries and obtain the molecular descriptors using the pseudopotential basis set. The prediction results with the inclusion of solvent effect are slightly better than that of the corresponding gas-phase calculations. The artificial neural network (ANN) model could be more satisfactory to predict the rate constants than the partial least squares regression (PLSR) and principal component analysis-multiple linear regression analysis (PCA-MLR) models.

Abstract: Neutral PBDEs congeners and their corresponding radical anions were studied with the pseudopotential method of stuttgart group (SDD) effective-core potentials basis set for the bromine atoms and the all-electron basis set for all other atoms. The pseudopotential method can be used for compounds containing heavy elements with relativistic effects and can reduce the computational time. The quantitative structure property relationship (QSPR) study was also performed in this work to develop models to predict the normolized reaction rate constants for the reductive debromination of polybrominated diphenyl ethers (PBDEs) by zero-valent iron (ZVI). The partial least squares regression (PLSR), principal component analysis-multiple linear regression analysis (PCA-MLR), and back propagation artificial neural network (BP-ANN) approaches were employed for the QSPR study between the molecular descriptors and the logarithm of normalized reaction rate constants of fourteen selected BDE congeners. The results show that the ANN models could be more satisfactorily to predict the rate constants than the PLSR and PCA-MLR models.

Abstract: The concentration of ammonia nitrogen in a slaughterhouse wastewater sample was determined using Nessler's reagent spectrophotometry with four different pretreatment approaches. Comparison of the results shows that the concentrations increased in the following order: coagulation sedimentation < boric acid absorption < filtration < acidifying filtration. Boric acid absorption method is more favorable, and standard curve method (SCM) should be considered superior to standard addition method (SAM) in the present research.

Abstract: Adsorption effects of three kinds of activated carbons and a type of machine-made charcoal on the removal of antimony from acidic aqueous solution were investigated and compared. With an initial antimony solution concentration of 1000 μgL^-1, the antimony adsorption by selected adsorbents were found to descend in the following order: machine-made charcoal (52.4%) > coconut activated carbon (42.6%) > coal based activated carbon (31.1%) > apricot stone based activated carbon (24.6%). The machine-made charcoal has the best adsorption capacity with a maximum adsorption values of 523.76 μgL^-1. Five kinetic models were used for the fitting of the process of antimony adsorption, including Elovich, parabola diffusion, second order, first order and double-constant. Results showed that parabola diffusion and double-constant rate equation were the most suitable models in describing the relationship of antimony adsorption with time in acidic aqueous solution, implying that the adsorption kinetics of the antimony by the selected adsorbents in water might be a surface diffusion. Three adsorptive capacity indicators (iodine number, methylene blue number and phenol number) were determined in this paper. However, machine-made charcoal, which has a relatively high adsorption capacity, is of the lowest levels of the adsorptive capacity indicators. Thus, some complex mechanisms might be involved for the antimony adsorption by the machine-made charcoal, consequently considering the mechanism for the adsorption of antimony by the charcoal has not been verified, a further study still needs to be done.

Abstract: Release kinetics of phosphorus in 17 sediments samples collected from Baihua Lake were determined, and the relationship between the phosphorus release kinetic parameters and the sediment composition was also investigated. The results showed that both the Elovich equation and power function equation were valid models for describing the phosphorus release data in the 17 sediments. Within the beginning 12 h, the rate of phosphorus release was high, and then decreased. Our correlation analysis demonstrates that there were no significant correlations between the maximum capacity of phosphorus release (Qmax) and the content of total nitrogen (TN), organic matter (OM), calcium-bound phosphorus (Ca-P), and organic phosphorus (OP). But the correlation between Qmax and iron/aluminum-bound phosphorus (Fe/Al-P) content was positive (R2 = 0.6064, P < 0.01), suggesting that Fe/Al-P might be the main contributor to the released phosphorus in the sediments.

Abstract: Release kinetics of two selected heavy metals (Cu and Zn) in a sediment sample collected from the inlet of Baihua Lake was determined. The results show that the double-constant equation was considered as the best-fit equations describing the relationship of Cu and Zn release and time in the sediment from the inlet of the lake (R2 = 0.9759, 0.9226, P<0.01). The effects of temperature, acidity, salinity, and the water/soil ratio on the releasing of heavy metals in sediment sample were also investigated. The heavy metals release would increase as the temperature increased. A low pH value could promote the heavy metals release. The heavy metals in the sediment tended to be released under a relatively high salinity condition. The amount of the heavy metals released from the sediment decreased with the increase of the water/soil ratio.

Abstract: This paper reports a study on the distribution characteristics of sulfate-reducing bacteria (SRB) in seventeen sediment samples collected from Baihua Lake (a man-made deep plateau reservoir in Guizhou Province, China), and analyzes the correlations between the SRB content and pH value, organic matter (OM), AVS, Fe, Hg, As, Cu, Ca, Mg in the sediments. The results showed that the sediment collected from the sampling site of Yapengzhai had the highest population of SRB, and the sediment from the sampling site of Longtan SRB presented the lowest population of SRB. Moreover, there were positive correlations between SRB and OM, AVS, Fe, Hg, As, Cu, Ca, Mg whereas the negative correlations existed between the SRB content and pH value.

Abstract: Assessment of the pollution for the selected six heavy metals (Pb, Cu, Zn, Fe, Mn and Ni) in ten surface sediments sampled from Aha Lake in a dry season was made in the present investigation. Principal component analysis (PCA) was used to assess the sources of the heavy metals contamination and two components were extracted. Analysis of the lake characteristics and point source pollution revealed that the discharge of industrial effluent and coal mining wastewater were the possible sources of these heavy metals contamination. Based on the speciation characteristics of heavy metals in sediments, the method ratio of secondary phase to primary phase (RSP) was applied to evaluate the loadings and the bioavailability of these heavy metals. The RSP evaluation exhibited that Pb, Zn, Fe, Mn and Ni were mainly associated with Fe-Mn oxides besides residual phase, while Cu mainly existed in organic phase and residual phase. In summary, the potential risk posed to the lake caused by the heavy metals was high and descended in the order of Mn > Ni > Zn > Pb > Cu > Fe.