Research on the ecological risk of heavy metals in the soil around a Pb–Zn mine in the Huize County, China

The soil pollution by heavy metals was characterized in the mine tailings and surrounding soils of an old Pb–Zn mine in Huize County. Three hundred and ninety-six samples of agricultural and non-agricultural soil were analyzed for the total metal concentration by acid digestion and sixty-eight selected soil samples were used to determine the chemical fractionation of heavy metals with the modified BCR sequential extraction method. The pollution index of the heavy metals indices for As, Cd, Cr, Cu,Hg, Pb and Zn of non-agricultural soil and agricultural soils in the study area indicated the spreading of heavy metal pollution. Sequential extraction showed that most of Cd existed in an exchangeable form(31.2 %). The available content of Pb, Cu and Zn was mainly distributed in acid extractable fractions and Fe/Mn oxide fractions(27.9, 30 and 27.2 %), and Hg, As and Cr were mainly associated with residual fractions(90.4, 72.9 and 76.8 %). The risks of heavy metals were also evaluated by the risk assessment code(RAC) and potential ecological risk index, respectively. The results of RAC showed a medium and high risk of Cd(45.6 and 54.4 %), medium risk of Zn(100 %), low and medium risk of Cu(41.2 and 58.8 %), largely no risk of Hg(97.1 %), and mainly low risk of As and Pb(92.6and 91.8 %). The range of the potential ecological risk of soil was 58.2–1839.3, revealing a considerably high ecological risk in the study area, most likely related to acid mine drainage and the mining complexes located in the area. The results can be used during the ecological risk screening stage, in conjunction with the total concentrations and metal fractionation values, to better estimate ecological risk.

Biogeography and diversity patterns of antibiotic resistome in the sediments of global lakes

Lakes act as one of the reservoirs and dispersal routes of antibiotic resistance genes(ARGs)and pathogenic resistant bacteria in aquatic environments.Previous studies reported the occurrence and distribution of ARGs in lakes worldwide;however,few investigated the biogeography and diversity patterns of antibiotic resistome in the environment.To fill this gap,a large-scale data set of sediment metagenomes was collected from globally distributed lakes and characterized comprehensively using metagenomic assembly-based analysis,aiming to shed light on the biogeography and diversity patterns of ARGs in lake ecosystems from a global perspective.Our analyses showed that abundant and diverse ARGs were found in the global lake sediments,including a set of emerging ARGs such as mcr-type and carbapenem-resistant Enterobacteriaceae related genes.Most of the identified ARGs were generally associated with the commonly used antibiotics,suggesting the role of increasing antibiotic consumptions on the resistome prevalence.Spatially,the composition and diversity of ARGs varied across geographical distances and exhibited a scale-dependent distancedecay relationship.Notably,the composition of ARGs was largely shaped by bacterial community structure,and their diversities were co-governed by stochastic process(∼48%)and deterministic process(∼52%).Findings provide a valuable insight to better understand ecological mechanisms of ARGs in lake ecosystems and have important implication for the prevention and control of resistome risk.

Application of percarbonate and peroxymonocarbonate in decontamination technologies

Sodium percarbonate(SPC)and peroxymonocarbonate(PMC)have been widely used in modified Fenton reactions because of their multiple superior features,such as a wide pH range and environmental friendliness.This broad review is intended to provide the fundamental information,status and progress of SPC and PMC based decontamination technologies according to the peer-reviewed papers in the last two decades.Both SPC and PMC can directly decompose various pollutants.The degradation efficiency will be enhanced and the target contaminants will be expanded after the activation of SPC and PMC.The most commonly used catalysts for SPC activation are iron compounds while cobalt composi-tions are applied to activate PMC in homogenous and heterogeneous catalytical systems.The generation and participation of hydroxyl,superoxide and/or carbonate radicals are involved in the activated SPC and PMC system.The reductive radicals,such as carbon dioxide and hydroxyethyl radicals,can be generated when formic acid or methanol is added in the Fe(II)/SPC system,which can reduce target contaminants.SPC can also be activated by energy,tetraacetylethylenediamine,ozone and buffered alkaline to generate different reactive radicals for pollutant decomposition.The SPC and activated SPC have been assessed for application in-situ chemical oxidation and sludge dewatering treatment.The challenges and prospects of SPC and PMC based decontamination technologies are also addressed in the last section.