Search

The welded joint is the critical area in the structure integrity investigation. To understand the influence of the mechanical heterogeneous on the fracture parameters in welded joint, the represented way of the welded mechanical heterogeneity and its effect on the mechanical parameters at the crack tip are analyzed by using an elastic-plastic finite element analysis software in this paper. The investigated results indicate that continuous change of material mechanical properties could express the effect of the actual welded mechanical heterogeneity on the fracture mechanical parameters change in the welded joint more accurately, which provide a new approach on the fracture problem investigation in welded joints.

To understand the effect of a single overload on the fracture behavior in welded joints, the stress and strain field at the crack tip in a safe-end dissimilar metal welded joint in nuclear pressure vessel is simulated and analyzed by using the elastic-plastic finite element method in the paper, in which the mechanical heterogeneity in welded joint is emphatically considered. The investigating results indicate that the tensile plastic strain at crack tip increases, but the tensile stress decreases as a single overload increases, and the influence of a single overload on tensile strain is larger than one on tensile stress, which provide a theoretical basis for quantitatively estimating the crack growth rate of environmentally assisted cracking in the welded structural material of pressure vessel and piping in the nuclear power plant.

The responses of antioxidant systems after exposing Eisenia fetida to actual soil contaminated with PCBs were investigated. Among antioxidant enzymes, the primary response to early PCBs exposure can be attributed to catalase (CAT) and peroxidase (POD). These two enzymes could have a combined effect on fighting damage by reactive oxygen species. An obvious increase in the activity of CAT was recorded at 4 mg kg-1 compared to the control throughout the whole test days. PCBs exposure caused changes in POD activity in 2d and 4d. However, the activity of POD in E. fetida tissues changed little with PCBs concentrations in day 8 and 16d. Superoxide dismutase (SOD) changed little with PCBs in different time. The results suggest that the variations in CAT and POD of E. fetida could be used as early responsive biomarkers for oxidative stress caused by PCBs in a soil environment.

To investigate the concentrations of oxytetracycline (OTC), tetracycline (TTC), chlortetracycline (CTC) in pig feeds and manures, 30 samples of pig manures and 30 samples of pig feeds in different growth periods of pigs were sampled in Zhejiang Province in China. The results showed that the means of the concentrations of OTC, TTC and CTC in pig feeds were 8.76, 6.62 and 23.26 mg kg-1, respectively. The concentrations of OTC, TTC and CTC in manures were 2.98, 3.00 and 4.62 mg kg-1, respectively. The concentration of CTC in pig feeds were 2~4 times higher than that of OTC and TTC. The concentrations of OTC, TTC and CTC in manures from piglets were positively correlated to those in their feeds, with the correlation coefficients of 0.64, 0.61 and 0.58, respectively. It suggested that less amount of antibiotics should be added in piglet feeds than in other pig feeds.

Ash from incinerated e-waste dismantling residues (EDR) may cause significant health risks to people through ingestion, inhalation, and dermal contact exposure pathways. Ashes of four classified e-waste types generated by an incineration plant in Zhejiang, China were collected. Total contents and the bioaccessibilities of Cd, Cu, Ni, Pb, and Zn in ashes were measured to provide crucial information to evaluate the health risks for incinerator workers and children living in vicinity. Compared to raw e-waste in mixture, ash was metal-enriched by category incinerated. However, the physiologically based extraction test (PBET) indicates the bioaccessibilities of Ni, Pb, and Zn were less than 50 %. Obviously, bioaccessibilities need to be considered in noncancer risk estimate. Total and PBET-extractable contents of metal, except for Pb, were significantly correlated with the pH of the ash. Noncancer risks of ash from different incinerator parts decreased in the order bag filter ash (BFA) > cyclone separator ash (CFA) > bottom ash (BA). The hazard quotient for exposure to ash were decreased as ingestion > dermal contact > inhalation. Pb in ingested ash dominated (>80 %) noncancer risks, and children had high chronic risks from Pb (hazard index >10). Carcinogenic risks from exposure to ash were under the acceptable level (

Anaerobic dechlorination is an effective degradation pathway for higher chlorinated polychlorinated biphenyls (PCBs). The enhanced reductive dechlorination of PCB-contaminated soil by anaerobic composting with zero-valent iron (ZVI) was studied, and preliminary reasons for the enhanced reductive dechlorination with ZVI were investigated. The results show that the addition of nanoscale ZVI can enhance dechlorination during in-vessel anaerobic composting. After 140 days, the average number of removed Cl per biphenyl with 10 mg g(-1) of added nanoscale ZVI was 0.63, enhancing the dechlorination by 34 % and improving the initial dechlorination speed. The ZVI enhances dechlorination by providing a suitable acid base environment, reducing volatile fatty acid inhibition and stimulating the microorganisms. The C/N ratios for treatments with the highest rate of ZVI addition were smaller than for the control, indicating that ZVI addition can promote compost maturity.

Anaerobic dechlorination is an effective degradation pathway of higher chlorinated polychlorinated biphenyls (PCBs). The efficiency of anaerobic composting remediation of PCB-contaminated soil using pig manure was determined. The results show that the dechlorination of PCB-contaminated soil via anaerobic composting with pig manure is feasible. PCB concentration is the most critical factor. Elevated PCB concentrations can inhibit dechlorination but does not disrupt the anaerobic fermentation process. At 1 mg kg −1 PCBs, the degradation rate of five or more chlorinated biphenyls is 43.8%. The highest dechlorination performance in this experiment was obtained when the soil-to-organic waste ratio, carbon-to-nitrogen ratio, moisture content, and PCB concentration were 2:3, 20, 60%, and 1 mg kg −1 , respectively.