Journal of Environmental Sciences - Volume 17, issue 6

Authors: LI, Jing | XIE, Zheng-miao | ZHU, Yong-guan | Naidu, Ravi

Article Type: Research Article

Abstract: Heavy metal contamination of soils through anthropogenic activities is a widespread and serious problem confronting scientists and regulators throughout the world. In this study we investigated the distribution, chemical species and availability of lead, zinc, cadmium and copper in nine surface (0 to 20 cm) soils from near an abandoned lead/zinc mine tailings located in Shaoxing, Zhejiang, China. Total heavy metal contents ranged from 5271 to 16369 mg/kg for Pb, 387 to 1221 mg/kg for Zn, …3.0 to 9.3 mg/kg for Cd and 65 to 206 mg/kg for Cu. In general, all heavy metals exceeded China National Standards for Soil Environmental Quality of Heavy Metals by a factor of 3–65 times. Comparison of the heavy metal concentrations (Pb, Zn, Cd and Cu) with clay content revealed a strongly significant relationship while significant relationship (P<0.001 ) was also obtained between Cd + Zn and Pb + Cu. Solid phase speciation of the soils using Tessier procedure showed that the heavy metals were distributed in the order: residual > organically complexed-Fe-Mn oxides occluded > carbonate bound > exchangeable > water soluble. In the organic matter fraction, the ratio of Pb(29.1%) to its total concentration in the soils was higher than those of Zn(4.70%), Cd(3.16%) and Cu(9.50%). The percentages of the water soluble and the exchangeable fractions of Pb(1.80%) and Cd(2.74%) were markedly greater than those of Zn(0.10%) and Cu(0.15%), suggesting that Pb and Cd are relatively more mobile and hence more toxic in the contaminated soils. Strongly significant relationships between H_2 O-Pb, H_2 O-Zn and H_2 O-Cu, strong positive correlations between H_2 O-Pb, H_2 O-Zn, H_2 O-Cu and organic matter in soil were found. The content of H_2 O-Pb, H_2 O-Zn, H_2 O-Cu was negatively correlated with pH values. The similar negative relationships between pH values and exchangeable heavy metals were also recorded. It is suggested that increasing soil pH or liming the soil could decrease bioavailability of heavy metals in the soil. Show more

Keywords: fractionation, heavy metal, mining tailings, risk assessment, soil pollution

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 881-885, 2005

Authors: CHEN, Bing | YANG, Chun | GOH, Ngoh Khang

Article Type: Research Article

Abstract: Photodegradation of nitrobenzene and nitrophenols in aqueous solutions by means of UV/H_2 O_2 process was studied in the Rayox batch reactors. Three nitrophenol isomers were identified as main photoproducts in the irradiated NB aqueous solutions. The distribution of nitrophenol isomers follows the order p-> m-> o-nitrophenol. Other intermediates detected include nitrohydroquinone, nitrocatechol, catechol, benzoquinone, phenol, nitrate/nitrite ions, formic acid, glyoxylic acid, maleic acid, oxalic acid and some aliphatic ketones …and aldehydes. The degradation of nitrobenzene and nitrophenols at initial stages follows the first-order kinetics and the decay rate constants for nitrobenzene(NB) are around 10^{-3} –10^{-2} s^{-1} and for nitrophenols are around 10^{-2} s^{-1} . The decomposition of H_2 O_2 in the presence of NB and each nitrophenol isomers follows zero-order kinetics. The quantum yields at initial stages for NB decay were estimated around 0.30 to 0.36, and for NPs decay is around 0.31–0.54. Show more

Keywords: photodegradation, nitrobenzene, nitrophenols, UV/H_2O_2 process

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 886-893, 2005

Authors: WANG, Shu-mei | LIU, Jun-xin

Article Type: Research Article

Abstract: Compared to conventional oxidation ditches, an integrated oxidation ditch with vertical circle (IODVC) has the characters of concise configuration, simple operation and maintenance, land saving and automatical sludge returning. By the utilization of vertical circulation, an aerobic zone and an anoxic zone can be unaffectedly formed in the IODVC. Therefore, COD and nitrogen can be efficiently removed. However, the removal efficiency of phosphorus was Iow in the IODVC. In the experiment described, a laboratory scale system …to add an anaerobic column to the IODVC has been tested to investigate the removal of phosphorus from wastewater. The experimental results showed that the removal efficiency of TP with the anaerobic column was increased to 54.0% from 22.3% without the anaerobic column. After the acetic sodium was added into the influent as carbon sources, the mean TP removal efficency of 77.5% was obtained. At the same time, the mean removal efficiencies of COD, TN and NH_3 -N were 92.2%, 81.6% and 98.1%, respectively, at 12 h of HRT and 21–25 d of SRT. The optimal operational conditions in this study were as follows: recycle rate=1.5–2.0, COD/TN > 6, COD/TP > 40, COD loading rate=0.26–0.32 kgCOD/(kgSS·d), TN loading rate =0.028–0.034 kgTN/(kgSS·d) and TP loading rate=0.003–0.005kgTP/(kgSS·d), respectively. Show more

Keywords: integrative oxidation ditch with vertical circle, wastewater treatment, biological nutrient removal

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 894-898, 2005

Authors: SUN, Li-guang | YIN, Xue-bin | PAN, Can-ping | WANG, Yu-hong

Article Type: Research Article

Abstract: Since the ban on the use of organochlorine pesticides (OCPs) such as dichloro-diphenyl-trichloroethane (DDT) and hexachlorocyclohexane (HCH) in agriculture, their levels have generally dropped. In a number of cases, however, the levels of these OCPs were found to be unchanging or even increasing after the ban. With the aim to unveil the possible causes of these exceptions, we collected two lake cores from King George Island, West Antarctica, and determined their accumulation flux profiles and temporal …trends of these OCPs. In the lake core sediments with glacier meltwater input, the accumulation flux of DDT shows an abnormal peak around 1980s in addition to the expected one in 1960s. In the lake core sediments without glacier meltwater input, the accumulation flux of DDT shows a gradual decline trend after the peak in 1960s. This striking difference in the DDT flux profiles between the two lake cores is most likely caused by the regional climate warming and the resulted discharge of the DDT stored in the Antarctic ice cap into the lakes in the Antarctic glacier frontier. Furthermore, to investigate the change of OCPs loadings in the Antarctic coastal ecosystem, we reconstructed the HCH and DDT concentration profiles in penguin droppings and observed a gradual increase for the former and a continuous decrease for the latter during the past 50 years. The increase of HCH seems to be due to the regional warming from the early 1970s and the resulted HCH discharge to the coastal ecosystem by glaciers, meltwater and the illegal use of HCH in the Southern Hemisphere in the recent decade. The different temporal trends of HCH and DDT accumulation rate in the lake core with glacier meltwater input and the aged penguin droppings can be explained by their different water-soluble property. Show more

Keywords: organochlorine pesticides (OCPs), DDT and HCH, lake sediments, penguin droppings, temporal trend, climate warming

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 899-905, 2005

Authors: LIN, Jian-zhong | WANG, Ye-long | ZHANG, Wei-feng

Article Type: Research Article

Abstract: Lattice Boltzmann method and elastic particle collision model were used to investigate the sedimentation of short cylindrical pollutant particles with mechanical contacts for varying bulk number density ε and terminal Reynolds number Re_T . The corresponding experiments were performed as a comparison. The clusters of pollutant particles with an inverted "T" structure were observed, the pollutant particles for high ε and large Re_T scattered wider than that for low ε and small …Re_T . The sedimentation velocities increased suddenly at the initial stage, then decreased drastically, after that swayed around and approached to a steady value. The time to steady state did not depend on ε and Re_T . The effect of particle interactions was to hinder the average sedimentation velocity, and hindrance was directly proportional to ε. The orientation distributions of pollutant particles depended on Re_T and ε, especially on the former. Both the standard deviations of vertical and horizontal velocity, the former was larger than the latter, were nearly independent on ε and Re_T . Show more

Keywords: cylindrical pollutant particles, sedimentation, lattice-Boltzmann simulation, experiment, mechanical contact

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 906-911, 2005

Authors: HAO, Li-qing | WANG, Zhen-ya | HUANG, Ming-qiang | PEI, Shi-xin | YANG, Yong | ZHANG, Wei-jun

Article Type: Research Article

Abstract: In a smog chamber, the photooxidation of toluene was initiated by hydroxyl radical (OH·) under different experimental conditions. The size distribution of secondary organic aerosol (SOA) particles from the above reaction was measured using aerodynamic particle sizer spectrometer. It was found from our experimental results that the number of SOA particles increased with increasing the concentration of toluene. As the reaction time prolonged, the sum of SOA particles was also increased. After a reaction time of …130 min, the concentration of secondary organic aerosol particles would be kept constant at 2300 particles/cm^3 . Increasing illumination power of blacklamps could significantly induce a higher concentration of secondary organic aerosol particle. The density of SOA particles would also be increased with increasing concentration of CH_3 ONO, however, it would be decreased as soon as the concentration of CH_3 ONO was larger than 225.2 ppm. Nitrogen oxide with initial concentration higher than 30.1 ppm was also found to have little effect on the formation of secondary organic aerosol. Show more

Keywords: toluene, hydroxyl radical, secondary organic aerosol, smog chamber

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 912-916, 2005

Authors: YIN, Yun-feng | CAI, Zu-cong | LU, Jia-long

Article Type: Research Article

Abstract: Although numerous studies about the nature and turnover of soil organic matter (SOM) in light and heavy fractions (LFOM and HFOM, respectively) have been made, little information is available in relation to the relationship between LFOM and HFOM, and no attempts have been made to quantify a general relationship between LFOM and HFOM for agricultural soils under field condition. Our hypothesis is there may be an inherent relationship between LFOM and HFOM for agricultural soils under …certain unaltered management practices for a long period, to this end, we therefore studied typically soils taken from different parts in China by using a simple density fractionation procedure. The results indicated that LFOM was positively correlated with LFOM/HFOM ratio for three typical soils. This information will be of particular use not only in deepening our understanding of the dynamics of SOM fractions but also in evaluating the potential of agricultural soils to sequestrate C under different management practices in a long term. Show more

Keywords: soil organic matter, light fraction, heavy fraction, agricultural soils

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 917-920, 2005

Authors: WANG, Yan | GAO, Bao-yu | YUE, Qin-yan | ZHOU, Wei-zhi | CHU, Yong-bao

Article Type: Research Article

Abstract: This study investigated the floc aggregation, average floc size, floc size variance and floc growth velocity when ferric chloride (FeCl_3 ) and polyferric chloride (PFC) were used to treat the simulated water samples. The factors including coagulant dose, ionic strength and solution pH, which affect the floc aggregation, were studied. Experiments were carried out in a bench-scale reactor using photometric dispersion analyzer (PDA). Results showed that there were great differences between …the floc aggregation of PFC and FeCl_3 . The average floc size and floc growth velocity of PFC were much larger than those of FeCl_3 . Compared with FeCl_3 , PFC gave a better coagulation performance in wider range of pH, dosage and ionic strength. It was also found that the coagulation efficiency of PFC did not depend on average floc size but on floc growth velocity. Show more

Keywords: coagulants, photometric dispersion analyzer (PDA), floc aggregation, water treatment

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 921-925, 2005

Authors: SHI, Hui-xiang | XU, Xian-wen | XU, Xin-hua | WANG, Da-hui | WANG, Qi-da

Article Type: Research Article

Abstract: Ozonlysis in the treatment of p-nitrophenol solution was studied in this paper. The results indicated that the decomposition of p-nitrophenol was accelerated as the gas flow rate or pH value increased. When gaseous ozone concentration was 20.11 mg/L and pH was 3, after 24 min reaction, the removal rate of p-nitrophenol reached 73.04%, 86.11%, 91.71 % and 95% at the gas flow rate of 32, 40, 48 and 56 ml/min respectively. And when pH was 3, 4, 5, 6, the …decomposition rate was 66.38%, 82.09%, 90.46%, 97.50% after a 20 min reaction respectively. It was mainly O_3 molecule that took part in the decomposition when pH was 3. The main intermediates during the decomposition include catechol, o-benzoquinone, hydroquinone, p-benzoquinone, phenol, fumaric acid, maleic acid, oxalic acid and formic acid. The decomposition mechanism of p-nitrophenol was also discussed. Show more

Keywords: ozonation, p-nitrophenol, decomposition, mechanism

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 926-929, 2005

Authors: HUANG, Min-jia | JIANG, Gui-bin | ZHAO, Zong-shan | LIU, Ji-yan

Article Type: Research Article

Abstract: Base on the previous work in laboratory, a novel polyaniline doped with polydimethylsiloxane coating was developed on a stainless steel wire for solid phase microextraction (SPME) by electroplating method. This electroplating method not only has advantages of ease preparation and simple equipments required, but also increases the lifetime of the SPME fiber. The composite fiber (polyaniline/polydimethylsiloxane (PANI/PDMS)) was evaluated by analyzing n-tridecane, n-tetradecane and n-pentadecane in aqueous sample. The new fiber coating …showed comprehensive abilities to extract alkanes compounds. The relative standard deviations were found to be 6.8%–10.33%. Show more

Keywords: solid phase microextraction, stainless steel wires, electroplating fiber preparation, polyaniline/polydimethylsiloxane, alkanes

Citation: Journal of Environmental Sciences, vol. 17, no. 6, pp. 930-932, 2005