Lifei Zhang

Estimation and characterization of PCDD/Fs and dioxin-like PCBs from secondary copper and aluminum metallurgies in China.

The secondary metallurgy industry is considered as one source of polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs). This study investigated the emission factors and total emissions amounts of PCDD/Fs and dioxin-like polychlorinated biphenyls (dioxin-like PCBs) released from secondary aluminum and copper metallurgy industries in China. The congener patterns are shown and the formation mechanism is also discussed in this paper. The toxic equivalency (TEQ) emission factor of PCDD/Fs is higher for secondary copper production, at 14,802 ng TEQ t(-1) than for secondary aluminum production, at 2650 ng TEQ t(-1). However, the TEQ emission factor of dioxin-like PCBs of secondary aluminum production, with 193 ng TEQ t(-1), is higher than that of secondary copper production with 98.1 ng TEQ t(-1). The total estimated emission amount of PCDD/Fs released to air from the production of 2.75 million tons secondary aluminum and 2 million tons secondary copper in 2007 are 7.3 and 37.5 g TEQ yr(-1), respectively, the corresponding dioxin-like PCBs total emission amounts being 0.53 and 0.2 g TEQ yr(-1) respectively. In general, the emission factors and the total emission amounts of the secondary aluminum and copper metallurgies in China stay in the middle level compared to values reported for other countries. The most abundant congener of PCDD/Fs is 2,3,4,7,8-PeCDF and the most abundant congener of dioxin-like PCBs is CB-126 in samples collected from both secondary aluminum and copper metallurgies. According to the distribution of organochlorocompounds (PCDF>PCDD>PCB, PCDF/PCDD>>1) and the dominant contribution of higher chlorinated congeners, the de novo synthesis is assumed to be the main formation pathway of PCDD/Fs and PCBs in the secondary copper and aluminum metallurgies.

Acid Volatile Sulfides and Simultaneously Extracted Metals in a Metal-Polluted Area of Taihu Lake, China

There were similar distribution characteristics for acid volatile sulfides (AVS) and simultaneously extracted metals (SEM) in surface sediments, and the concentrations of AVS and SEM decreased from the deposition area to the center of the bay (lake). The ratio of AVS to SEM was <1 in the surface sediments, indicating that heavy metals in surface sediments may be bioavailable. The concentration of AVS increased with sediment depth, followed by a decrease with large variation, while the concentration of SEM remained constant. By comparing the concentration of SEM with total metals, it was shown that extracted Cu and Ni decreased with sediment depth, indicating increasing association of Cu and Ni with sulfides in deeper sediment layers. The lower extracted ratios for Pb and Zn compared with sulfidic sediment illustrated that AVS should not have strong control on sediment Pb and Zn. The molar ratio of AVS and reactive iron showed that heavy metals were dynamic and active in sediments in this lake.

Decomposition of hexachlorobenzene over Al2O3 supported metal oxide catalysts

Decomposition of hexachlorobenzene (HCB) was investigated over several metal oxides (i.e., MgO, CaO, BaO, La2O3, CeO2, MnO2, Fe2O3, and Co3O4) supported on Al2O3, which was achieved in closed system at a temperature of 300 degrees C. Catalysts were prepared by incipient wetness impregnation with different metal oxides loading and impregnating solvents. The decomposition efficiency of different catalysts for this reaction depends on the nature of the metal oxide used, and Al2O3 supported La2O3 was found to be the most active one. Pentachlorobenzene (PeCB), and all tetrachlorobenzene (TeCB), trichlorobenzene (TrCB), and dichlorobenzene (DCB) isomers were detected after the decomposition reaction, indicating that the decomposition was mainly a dechlorination process. The detection of all lower chlorinated benzenes suggested the complexity of decomposition and the presence of more than one dechlorination pathway.

Polychlorinated Biphenyls Residues in the Soil in Linfen, China

A total of 10 surface soil samples covering the whole territory of Linfen city were collected for analysis the 144 polychlorinated biphenyls (PCBs). The total PCBs concentration ranged from 0.2 to 3.4xa0ngxa0g−1 in urban soil and 0.5 to 14.8xa0ngxa0g−1 in industrial plant soil. Furthermore, increasing PCBs contamination was observed in northeast Linfen because of the distribution of industrial plants. Principal component analysis (PCA) revealed that the major source of PCBs in Linfen may be potentially associated with commercial #1 PCB through the long-range transmission. In total, PCBs were not a severe contamination in Linfen from current results.

Distribution of DDT in a Typical DDT Waste Contaminated Site

Serious pollution was found in the soil under a historically DDT workshop and the highest level of ∑DDT was 2682.86xa0mg/kg. The vertical distribution of DDT shows that the levels of DDT decreased significantly with increase of depth, which mainly because the infiltration of rainwater was inhibited by the cement or brick surface. The DDT polluted soil area was 6,814xa0m2 and the polluted soil volume 4,398xa0m3 above 10xa0mg/kg. The ratio of (DDExa0+xa0DDD) to DDT showed that part of the p,p′-DDT was degraded to DDD and DDE in the soil.

An Active Sampler for Monitoring Polychlorinated Dibenzo-p-dioxins and Furans in Ambient Air

An active sampler for monitoring polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) in air was developed using an automobile air filter set. The performance of the mobile air sampler was evaluated. Recoveries of PCDD/F congeners ranged from 62.3% to 64.5% with sampling volumes of 500–1,800xa0m3. Air samples were collected between April and June, 2007 in Beijing. The monitoring results of PCDD/F levels by the mobile sampler were comparable to results obtained by a conventional stationary high-volume active sampler. The results suggest this mobile air sampling technology is a promising new strategy for the assessment of air quality in urban areas.

Investigation of the decomposition mechanism of hexachlorobenzene on γ-Al2O3

Decomposition of hexachlorobenzene (HCB) on high surface area γ-alumina was comprehensively studied using in situ Fourier transform infrared spectroscopy, gas chromatography/mass spectrometry (GC-MS) and ion chromatography. Monitoring of the temperature-dependent decomposition by Fourier transform infrared spectroscopy showed that HCB decomposed as the temperature increased and phenolate species and other decomposition products formed. Pentachlorophenol (PeCP) and pentachlorobenzene were identified as the main decomposition products by GC-MS, and the time dependence of the formation of PeCP and pentachlorobenzene suggested that PeCP was the main intermediate. A trace analytical method based on derivatization and GC-MS revealed the presence of 3,4,5,6-tetrachloro-1,2-benzenediol and tetrachloro-hydroquinone. A small amount of inorganic chlorine ions produced by dechlorination of HCB was detected by ion chromatography. PeCP was the main intermediate and was transformed to 3,4,5,6-tetrachloro-1,2-benzenediol and tetrachloro-hydroquinone on the alumina surface. These compounds then decomposed to small molecules via cracking of their aromatic rings.