Migration of ammonium nitrogen in ion-absorbed rare earth soils during and post in situ mining: a column study and numerical simulation analysis

Ion-absorbed rare earth mines,leached in situ,retain a large amount of ammonium nitrogen(NH4–N)that continuously releases into the surrounding environments.However,quantitative descriptions and predictions of the transport of NH4–N across mining area with hill slopes are not fully established.Here,laboratory column experiments were designed with an inclined slope(a sand box)to examine the spatial temporal transport of NH4–N in soils collected from the ionic rare earth elements(REE)mining area.An HYDRUS-2D model simulation of the experimental data over time showed that soils had a strong adsorption capacity toward NH4–N.Chemical non-equilibrium model(CNEM)could well simulate the transport of NH4–N through the soil-packed columns.The simulation of the transport-adsorption processes at three flow rates of leaching agents revealed that low flow rate enabled a longer residence time and an increased NH4-N adsorption,but reduced the extraction efficiency for REE.During the subsequent rainwater washing process,the presence of slope resulted in the leaching of NH4–N on the surface of the slope,while the leaching of NH4–N deep inside the column was inhibited.Furthermore,the high-intensity rainfall significantly increased the leaching,highlighting the importance of considering the impact of extreme weather conditions during the leaching process.Overall,our study advances the understanding of the transport of NH4–N in mining area with hills,the impact of flow rates of leaching agents and precipitation intensities,and presents as a feasible modeling method to evaluate the environmental risks of NH4–N pollution during and post REE in situ mining activities.

The frontier of soil science: Soil health

Soils are a valuable resource with life activity in terrestrial ecosystem,and soil health and its sustainable management are becoming a major focus of global concern.A healthy soil is a“harmonious social system”,which should have good structure,functional state,and buffering performance to maintain the dynamic balance of soil ecosystem.Soil health has become the frontier of soil science.The development of theoretical and practical approaches for soil health evaluation and management is urgently needed.Therefore,further research is needed to develop new techniques and methods for soil health research,construct soil health index and evaluation system,clarify the mechanism and spatial-temporal pattern of soil health conservation,and establish soil health protection and cultivation technology,which would provide scientific and technological support for soil resource protection and sustainable utilization.

A systematic review of the impacts of exposure to micro-and nano-plastics on human tissue accumulation and health

Micro-and nano-plastics(MNPs)pollution has become a pressing global environmental issue,with growing concerns regarding its impact on human health.However,evidence on the effects of MNPs on human health remains limited.This paper reviews the three routes of human exposure to MNPs,which include ingestion,inhalation,and dermal contact.It further discusses the potential routes of translocation of MNPs in human lungs,intestines,and skin,analyses the potential impact of MNPs on the homeostasis of human organ systems,and provides an outlook on future research priorities for MNPs in human health.There is growing evidence that MNPs are present in human tissues or fluids.Lab studies,including in vivo animal models and in vitro human-derived cell cultures,revealed that MNPs exposure could negatively affect human health.MNPs exposure could cause oxidative stress,cytotoxicity,disruption of internal barriers like the intestinal,the air–blood and the placental barrier,tissue damage,as well as immune homeostasis imbalance,endocrine disruption,and reproductive and developmental toxicity.Limitedly available epidemiological studies suggest that disorders like lung nodules,asthma,and blood thrombus might be caused or exacerbated by MNPs exposure.However,direct evidence for the effects of MNPs on human health is still scarce,and future research in this area is needed to provide quantitative support for assessing the risk of MNPs to human health.

Sorption and desorption characteristics of sulfamethazine in three different soils before and after removal of organic matter

Organic matter(OM)is the most critical factor in controlling the sorption-desorption of SMZ in soil,however,few studies have explored the effects of OM removal on these important behaviors among different soils.Batch experiments were conducted to investigate the sorption and desorption characteristics of SMZ in three different soils:fluvo-aquic soil(FS),paddy soil(PS),and red soil(RS).The SMZ sorption in the evaluated soils was dominated by physisorption.The SMZ sorption capacities of FS and PS,which had a relatively higher OM content than RS,were higher than that of RS.The SMZ sorption in FS was dominated by linear partitioning.In contrast,the SMZ sorption in PS and RS was mainly nonlinear surface adsorption.After OM removal,the SMZ sorption capacity was significantly reduced in FS but increased in PS and RS.Furthermore,OM removal restrained the sorption intensity of SMZ in soils.Relatively higher OM and clay contents inhibited the SMZ desorption in FS and PS.The strong negative desorption hysteresis of SMZ in the three soils indicated that SMZ was able to move into the soil solution,thereby posing a risk to humans.Taken together,the findings of this study showed that OM indeed plays an important role during SMZ sorption-desorption in soil.

Cadmium found in peanut (Arachis hypogaea L.) kernels mainly originates from root uptake rather than shell absorption from soil

Roots and shells are two potential organs through which peanut plants absorb cadium(Cd)from soils;however,the relative contributions of the two uptake pathways(root uptake and shell absorption)to kernel Cd accumulation and their translocation characteristics are poorly understood.In this study,the relative contributions of the two pathways to Cd accumulation in two peanut cultivars,Xianghua2008(XH)and Yueyou43(YY),were accurately assessed by labeling rooting and podding zone soils with 113Cd and 111Cd isotopes(0.3 mg kg^(-1) dry soil),respectively,in a split-pot design.The results showed that approximately 96%of the Cd accumulated in the peanut kernels was derived from root uptake,while only 4%originated from shell absorption.Only 1%of the Cd accumulated in whole peanut plants was attributed to shell absorption,of which 41%–44%was retained in shells and 56%–59%was translocated to kernels.In contrast,the Cd absorbed by roots was efficiently translocated into all plant organs,of which 80%–84%was distributed in shoots.Although YY accumulated 1.3 times more Cd in whole plants than XH,the relative contributions of the two pathways to Cd accumulation in each plant organ were barely affected by peanut cultivars.Due to the strong retention effect of shells,shell-derived Cd was approximately 2 times higher than root-derived Cd in shells.These results would improve the understanding of Cd accumulation processes in peanut plants,revealing that the root uptake pathway contributes predominantly to the Cd concentration in peanut kernels,based on which strategies and technology for the reduction of Cd in peanut plants could be designed and developed.

Perspectives on ecological risks of microplastics and phthalate acid esters in crop production systems

Microplastics(MPs)and phthalate acid esters(PAEs)co-occur as emerging contaminants of global importance.Their abundance in soil is of increasing concern as plastic-intensive practices continue.Mulching with plastic films,inclusion in fertilizers,composts,sludge application,and wastewater irrigation are all major and common sources of MPs and PAEs in soil.Here,we review studies on the concentration and effects of MPs and PAEs in soil.While there is limited research on the interactions between MPs and PAEs in agroecosystems,there is evidence to suggest they could mutually affect soil ecology and plant growth.Therefore,we propose new research into 1)establishing an efficient,accurate,and simple method to quantify different types of microplastics in soils and plants;2)exploring the behavior and understanding the mechanisms of co-transfer,transformation,and interactions with soil biota(especially in vegetable production systems);3)assessing the risk and consequences of combined and discreet impacts of MPs and PAEs on plants and soil biota,and 4)preventing or reducing the transfer of MPs and PAEs into-and within-the food chain.

Biological transfer of silver under silver nanoparticle exposure and nitrogen transfer via a collembolan- predatory mite food-chain and ecotoxicity of silver sulfide

The development of nanotechnology has accelerated the use of silver nanoparticles(AgNPs)in household chemicals and the accumulation of Ag in sewage treatment systems.The application of sewage sludge products to soils raises concerns over the safety of Ag in the function and biogeochemical cycles of the soil belowground ecosystem.Here,we assess the potential risk of the accumulation and transfer of Ag under AgNPs exposure and its effects on the trophic transfer of nitrogen(N)through a soil animal food chain(Folsomia candida–Hypoaspis aculeifer).The formation of stable silver sulfide(Ag_(2)S)was also studied via a single species test using F.candida.Concentrations of Ag in F.candida increased with increasing AgNPs concentration,as did those in the predator H.aculeifer,but the Ag bioaccumulation factors of both animals were<1.Folsomia candida body tissue 15 N abundance declined markedly compared with that of H.aculeifer.Silver sulfide did have adverse effects on the survival and reproduction of F.candida.The Ag concentrations of F.candida increased with increasing Ag_(2)S concentration in sludge-treated soils.Silver sulfide showed ecotoxicity to the collembolan,therefore ecotoxicity resulting from the transformation and fate of AgNPs in soils needs to be considered before biosolid products are applied to agricultural soils.

Biochar for future and futuristic biochar

Biochar,a close-to-natural product derived from renewable biomass resources,has proven to be a promising carbon-negative material for achieving sustainable development goals and improving the future well-being of ecosystems and human life.Over the past thousands of years,advances in biochar research could generally be divided into three stages:the historical application stage,the recognition and investigation stage,and the rapid engineered development and advancement stage.In this perspective,we describe the development history of biochar,discuss the features of futuristic biochar,and propose new research directions for biochar in the future.

Rhizosphere microbes influence wogonoside accumulation in perennial Scutellaria baicalensis

Dried roots of Scutellaria baicalensis Georgi are an acclaimed traditional Chinese medicine,and wogonoside content is a key indicator used to evaluate S.baicalensis quality.Rather than rising linearly with cultivation years,S.baicalensis quality initially increases and then declines.However,little is known regarding the dynamic variations in S.baicalensis rhizosphere microorganisms under long-term cultivation and underlying mechanisms of their effects on wogonoside formation and accumulation.The aim of this study was to investigate the roles of soil nutrients and rhizosphere microbes on S.baicalensis quality across different cultivation years(1-4 years).The wogonoside content(25.14 mg g^(-1))was highest in the biennial S.baicalensis and then decreased following long-term cultivation.Most soil nutrients(available nitrogen,available phosphorus,available iron,available manganese,and available zinc)were reduced significantly as cultivation years increased.Time also affected rhizosphere bacterial community structure significantly,driving it toward deterministic process(i.e.,β-nearest taxon index<-2).Available manganese and exchangeable calcium indirectly affected wogonoside formation and accumulation.Wogonoside inhibition was driven by the reduction in rhizosphere bacterial diversity,which significantly increased the relative abundance of beta-glucosidase and decreased the relative abundance of phenylalanine ammonialyase.The rhizosphere microenvironment was altered under long-term cultivation,thereby shaping rhizosphere bacterial community,reducing the community diversity,and ultimately inhibiting wogonoside formation and accumulation.Our findings may aid in understanding of the mechanisms and reasons for the reduction in S.baicalensis quality under long-term cultivation from the perspective of soil nutrients and microorganisms,which may theoretically support the future artificial cultivation and management of Chinese medicinal plants.