[Retarding potential of biochar on antibiotic resistance genes in soil and the mechanisms: A review.] / ç”Ÿç‰©ç‚­å¯¹åœŸå£¤ä¸­æŠ—ç”Ÿç´ æŠ—æ€§åŸºå› çš„é˜»æŽ§æ½œåŠ›åŠæœºåˆ¶ç ”ç©¶è¿›å±•.

Antibiotic resistance genes (ARGs) in soil pose a major challenge to global environment and health. The development of effective technologies to reduce their negative effects has implications for maintaining soil health and human health. Biochar would be a suitable control material due to its characteristics of high carbon content, large surface area, excellent adsorption capacity, and economic advantages. There are three mechanisms underlying its negative effects on the abundance of ARGs: 1) adsorption of certain pollutants (e.g., antibiotics and heavy metals) to reduce the co-selective pressure of ARGs; 2) alteration of microbial composition through altering soil physico-chemical properties, and thereby limiting the ability of bacteria to undergo horizontal transfer of ARGs; 3) direct impairment of horizontal gene transfer by the adsorption of horizontal transfer vectors such as plasmids, transposons, and integrons. However, the negative effect of biochar depends on the source of material, pyrolysis process, and its amount added. Furthermore, field aging of biochar may reduce its ability to block ARGs. Endogenous contaminants of biochar, such as polycyclic aromatic hydrocarbons and heavy metals, may cause the enrichment of specific antibiotic-resistant bacteria in the environment or induce horizontal gene transfer. In further studies, suitable biochar should be selected according to soil environments, and biochar aging control measures should be taken to improve its retarding effect on ARGs.

Controls on rare-earth element transport in a river impacted by ion-adsorption rare-earth mining.

Rare-earth elements (REEs) are known to be a group of emerging pollutants, but the geochemistry of REEs in river waters in ion-adsorption rare-earth mining areas has attracted little attention. In this study, samples of the <0.45 µm and 0.22-0.45 µm (large colloids) water fractions and acid-soluble particles (ASPs) were collected from a river impacted by ion-adsorption rare-earth mining activities. The roles of ligand complexation, colloid binding, and particle adsorption in REE transport and distribution were also investigated. Results showed higher concentrations of REEs in the <0.45 µm fraction of all sampling sites (3.30 × 10-2-9.42 µM) compared with that in the control site (1.21 × 10-3 µM); this fraction was also characterized by middle REE enrichment at upstream sites, where REEs are mainly controlled by the <0.22 µm fraction (55%-94% of the species found in the <0.45 µm fraction) and ligand complexation (REE3+, REE(SO4)+, and REE(CO3)+). At downstream sites, heavy REE enrichment was observed, which was largely determined by binding to large colloids (68%-83% of the species found in the <0.45 µm fraction) and adsorption to particles (>90% of the acidified bulk water). Furthermore, REE patterns indicated that the REE-associated large colloids were mineral or mixed mineral-organic matter (OM) at upstream sites and OM-dominated or functionalized at downstream sites. The particles were mainly coated by inorganic matter substances (e.g., Fe/Al oxyhydroxides). In summary, our results reveal that REE patterns provide a useful tool to study the fate of REEs in ion-adsorption rare-earth mining catchments.