Search

Antibiotic resistance genes (ARGs) in municipal wastewater pose a potential threat to the environment. In this study, the change in absolute and relative abundance of ARGs, metal resistance genes (MRGs), and mobile genetic elements (MGTs) were investigated during an emergent municipal wastewater treatment by the magnetic separation process. Results indicate that all the concentrations of targeted ARGs, MRGs, and MGTs decreased significantly in the primary and secondary stirring tank. However, the absolute abundance of some ARGs and MRGs increased in the effluent, which is likely caused by the presence of ample MGTs, in the order of int1 (2.00×10 10 copies·mL -1 ) > int2 (1.91×10 8 copies·mL -1 ) > Tn 916/1545 e (5.38×10 8 copies·mL -1 ). The results obtained from network and PCA analysis showed that the removal of ARGs and MRGs were significantly associated with variations in the microbial community and common pollutants in urban wastewater, such as suspended solids, phosphorus, and COD, which are important factors for affecting the removal efficiency of antibiotic resistance genes and metal heavy resistance genes. These results show that magnetic separation can effectively reduce common pollutants in urban wastewater and might further restrict the transmission and transfer of ARGs. Moreover, it is necessary to strengthen the subsequent management of magnetic separation effluent and dehydrated sludge by disinfection technologies to lessen the risk of antimicrobial contamination.

Soil samples were collected from 18 sites at a relocated lead accumulator factory in the Southwest region, China. Among the 15 sample sites, profile soil samples at 0-20 cm, 20-40 cm and 40-60 cm were taken. Soil lead contents were analyzed by inductively coupled plasma-optical emission spectroscopy (ICP-OES). Characteristics of Pb in topsoil and soil profiles collected from different sampling sites were discussed. Results showed that: (1) The total Pb contents in topsoil (0-20 cm) ranged from 18.18 to 52,332.50 mg x kg(-1). The maximum content greatly exceeded the national standard (HJ 350-2007). The Pb concentration in different workshops followed a decreasing order: the fourth workshop > the second workshop > waste lead storage pit > sewage works > the third workshop > the fifth workshop > the first workshop > the original fourth workshop > the packing workshop > the office area. (2) Results of profile distribution showed that soil depth had no significant effect on Pb content. Lead can be highly accumulated at different depths of the soil, which was quite different from natural soils. (3) Hakanson's potential ecological risk index evaluation showed that there was widespread ecological risk in the soil of the plant, and serious ecological risk existed in some workshops where a large number of lead was enriched. Therefore, the site must be restored in order to reuse it.