Landfills harbor ideal conditions for microbial mercury methylation. However, the levels and distribution of mercury (Hg) and methylmercury (MeHg), potential microbial Hg methylation, and their linkage within landfills are largely unknown. In the present study, total mercury (THg), MeHg, the Hg methylation gene (hgcA) and mer operon were quantified in 30 waste samples from different depths (0-30 m) at 5 locations within a large-scale landfill in China. The average concentrations of THg and MeHg in the solid waste samples were 1422.91 ng/g and 3.15 ng/g, respectively. THg (up to 14405.29 ng/g) and MeHg (up to 10.42 ng/g) have high concentrations in the middle part (10-15 m) along the depth profiles. The concentration of THg was strongly positively (both p < 0.05) correlated with the MeHg concentration and the relative abundance of hgcA, indicating that the THg concentration can play an important role in microbial Hg methylation. The hgcA genes were detected in most samples and mer operon were detected in all samples. Combined hgcA qPCR and metagenomics data showed that Archaea Methanofollis may mainly account for Hg methylation within landfills. These findings provide funda-mental knowledge on Hg cycles in landfills.

汞(Hg)是一种高毒性的重金属污染物,也被世界卫生组织列为优先控制污染物.甲基汞(MeHg)是毒性最强的Hg化合物,具有高神经毒性、致癌性、生殖毒性和免疫系统毒性.大量含Hg废物随固体废物进入垃圾填埋场并随着固体废物降解进行演化,使垃圾填埋场成为Hg的重要污染源,对Hg和MeHg在填埋场的环境行为研究对于垃圾填埋场Hg污染防治至关重要.目前,Hg和MeHg在水稻土及湿地等环境介质中的转化途径和机制、环境归趋及其相关影响因素等方面是全球研究热点,但其在垃圾填埋场中鲜有研究,而垃圾填埋场具有理想的Hg生物甲基化条件(厌氧环境、多样性的Hg甲基化微生物及富含有机物等).总结了垃圾填埋场中Hg的转化途径和机制,以及MeHg在填埋场的研究现状,讨论了厌氧环境下Hg生物甲基化的微生物群落结构和功能(Hg的甲基化基因hgcAB),前瞻了填埋场Hg生物甲基化的潜力,最后对填埋场中Hg和MeHg的环境行为研究提出了建议.

Landfill are important reservoirs of antibiotics and antibiotic resistance genes (ARGs). They harbor diverse contaminants, such as heavy metals and persistent organic chemicals, complex microbial consortia, and anaerobic degradation processes, which facilitate the occurrence, development, and transfer of ARGs and antibiotic resistant bacteria (ARB). The main concern is that antibiotics and developed ARGs and ARB may transfer to the local environment via leachate and landfill leakage. In this paper, we provide an overview of established studies on antibiotics and ARGs in landfills, summarize the origins and distribution of antibiotics and ARGs, discuss the linkages among various antibiotics, ARGs, and bacterial communities as well as the influencing factors of ARGs, and evaluate the current treatment processes of antibiotics and ARGs. Finally, future research is proposed to fill the current knowledge gaps, which include mechanisms for the development and transmission of antibiotic resistance, as well as efficient treatment approaches for antibiotic resistance.