The Dual Roles of Nano Zero-Valent Iron and Zinc Oxide in Antibiotics Resistance Genes (ARGs) Spread in Sediment.

Nanoparticles (NPs) are widely used and ubiquitous in the environment, but the consequences of their release into the environment on antibiotics resistance genes (ARGs), microbial abundance, and community, are largely unknown. Therefore, this study examined the effect of nano zero-valent iron (nZVI) and zinc oxide (nZnO) on tetracycline resistance genes (tet-ARGs) and class 1 integron (intI1) in sediment under laboratory incubation. The coexistence of NPs and tetracycline (TC) on tet-ARGs/intI1 was also investigated. It was found that nZVI and nZnO promoted tet-ARGs/intI1 abundance in sediment without TC but reduced the inducing effect of TC on tet-ARGs/intI1 in sediment overlaid with TC solution. Without TC, nZVI, intI1, and the bacterial community could directly promote tet-ARGs spread in nZVI sediment, while intI1 and bacterial abundance were the most directly important reasons for tet-ARGs spread in nZnO sediment. With TC, nZVI and bacterial community could reduce tet-ARGs abundance in nZVI sediment, while nZnO and bacterial community could directly promote tet-ARGs in nZnO sediment. Finally, these findings provided valuable information for understanding the role of NPs in promoting and reducing ARGs in the environment.

Factors affecting sorption behaviors of tetracycline to soils: Importance of soil organic carbon, pH and Cd contamination.

The abuse of tetracycline arises the risk of antibiotic resistance genes and has been paid much attention. To understand the potential bioavailability of tetracycline (TC) in soil environments, this study explored the behaviors of TC adsorbing to six types of soils sampled from different regions of China. Moreover, the solution pH and existence of Cd2+ effect on TC sorption to soils were investigated to understand the influential factors affecting TC sorption. The results showed that the soil properties and sorption capacity of TC varied significantly with different soils. The sorption capacity of TC to soils might be largely affected by cation exchange capacity (CEC) and soil organic carbon (SOC), while the sorption rate, interaction strength and equilibrium sorption binding might be affected by soil pH, pHPZC, soil inorganic carbon (SIC) and H content. The result of solution pH effect suggested that the predominant sorption mechanism for acid soils might be hydrophobic interactions between soils and H2TC0, and the cation exchange was possibly proposed as the primary mechanism for TC sorption to alkaline soils. Furthermore, the presence of Cd2+ might increase TC sorption to acid soil, while reduce TC sorption to alkaline soil. It is expected that this study may provide important information for predicting the potential fate of TC (or similar antibiotics) in different soils, and thus helping to assess the bioavailability of TC in soils.