The co-transport of Cd(Ⅱ) and nZnO in saturated soil packed column:effects of ionic strength and pH

The rapid development and widespread use of ZnO nanoparticles(nZnO) in various industries have raised concerns about their potential environmental impact.Therefore,understanding the fate and role of nZnO in the natural environment is crucial for mitigating their hazardous effects on the environment and human safety.The purpose of the present study was to provide scientific support for understanding and eliminating the joint risk of nanoparticle and heavy metal pollution in the soil environment by revealing the co-transport characteristics of Cd(Ⅱ) and ZnO nanoparticles(nZnO) in soil under different ionic strength(IS) and pH.The impacts of different IS and pH on the co-transport of Cd(Ⅱ) and nZnO in a20 cm long with an inner diameter of 2.5 cm acrylic column packed with 10 cm high soil samples were investigated in the present study.In the above system,a500 μg L^(-1) Cd(Ⅱ) loaded nZnO suspension pulse with varying IS or pH was introduced into the soil column for leaching over 5 PVs,followed up by 5 PVs background solutions without nZnO.The IS was 1,10,or 50 mM NaCl,with pH6,or the pH was 6,7 or 8 with 1 mM NaCl.Meanwhile,Sedimentation experiments for nZnO,adsorption of Cd(Ⅱ) on soil,and nZnO,DLVO theory calculation for the same background condition were conducted.The presence of nZnO significantly increased the mobility of Cd(Ⅱ) as a result of its strong adsorption capacity for nZnO-associated Cd(Ⅱ).However,with the increase of IS,the co-transport of nZnO and Cd(Ⅱ) was decreased and the retention of nZnO in the soil column due to more nZnO attended to aggregate and sediment during the transport and the decrease in the adsorption capacity of nZnO for Cd(Ⅱ) by competition of Na^(+).When pH was 6,7,and 8,the co-transport of nZnO and Cd(Ⅱ) increased with higher pH due to the lower electrostatic attraction between nZnO and soil under higher pH.Meanwhile,the DLVO theory was fitted to describe the above co-transport process of nZnO and Cd(Ⅱ).More attention should be paid to the presence of nZnO on the migration of Cd(Ⅱ) in the natural soil to control the potential risk of nanoparticles and heavy metals to the environment.The risk of co-transport of nZnO and Cd(Ⅱ) might be controlled by adjusting IS and pH in the soil solution.

Unveiling the performance of a novel alkalizing bacterium Enterobacter sp.LYX-2 in immobilization of available Cd

A novel alkalizing strain Enterobacter sp.LYX-2 that could resist 400 mg/L Cd was isolated from Cd-contaminated soil,which immobilized 96.05%Cd^(2+)from medium.Cd distribution analysis demonstrated that more than half of the Cd^(2+)was converted into extracellular precipitated Cd through mobilization of the alkali-producing mechanism by the strain LYX-2,achieving the high immobilization efficiency of Cd^(2+).Biosorption experiments revealed that strain LYX-2 had superior biosorption capacity of 48.28 mg/g for Cd.Pot experiments with Brassica rapa L.were performed with and without strain LYX-2.Compared to control,15.92%bioavailable Cd was converted to non-bioavailable Cd and Cd content in aboveground vegetables was decreased by 37.10%with addition of strain LYX-2.Available Cd was mainly immobilized through extracellular precipitation,cell-surface biosorption and intracellular accumulation of strain LYX-2,which was investigated through Cd distribution,Scanning Electron Microscope and Energy-Dispersive X-ray Spectroscopy(SEM-EDS),Fourier Transform Infrared Spectroscopy(FT-IR),X-ray Photoelectron Spectroscopy(XPS)and Transmission Electron Microscopy(TEM)analysis.In addition,the application of strain LYX-2 significantly promoted the growth of vegetables about 2.4-fold.Above results indicated that highly Cd-resistant alkalizing strain LYX-2,as a novel microbial passivator,had excellent ability and reuse value to achieve the remediation of Cd-contaminated soil coupled with safe production of vegetables simultaneously.

Ecosystem service bundle index construction,spatiotemporal dynamic display,and driving force analysis

Introduction:Existing studies on ecosystem service relationships are mainly qualitative or semi-quantitative assessments,but lack of quantitative exploration of aggregated ecosystem services and their influencing factors.We mapped the distributions of 12 ecosystem services of Zhejiang Province in 2000 and 2015 at the district and county level,analyzed their relationships using Spearman’s correlation analysis,constructed ecosystem service bundle index(ESBI)for each district and county by structural equation model,and then through multiple linear regression,we explored factors associated with ESBI variations.Outcomes:Our results showed that(1)most ecosystem services were spatially clustered.There were synergies between individual ecosystem services in categories of provisioning and regulating services,respectively;(2)our proposed ESBI index system consists of overall index and sub-indices of provisioning,regulating,and cultural services.The higher the ESBI value,the more important the corresponding place for multiple aggregated ecosystem service provision.Compared to 2000,ESBI in 2015 distributed more unevenly,and the average dropped by 3.10%;and(3)the increase of ESBI was associated with its initial value,and four socioeconomic and natural factors;the decrease of ESBI was influenced by the initial value and six key socioeconomic factors.Discussion and Conclusion:Our proposed ESBI system has several advantages(e.g.,scale free,flexible weighting,quantitative and continuous indices for further analyses,and alternative non-monetary solution)in understanding and managing relationships among multiple ecosystem services.

How silicon fertilizer improves nitrogen and phosphorus nutrient availability in paddy soil?

In order to reveal the mechanism of silicon(Si)fertilizer in improving nitrogen(N)and phosphorus(P)nutrient availability in paddy soil,we designed a series of soil culture experiments by combining application of varying Si fertilizer concentrations with fixed N and P fertilizer concentrations.Following the recommendations of fertilizer manufacturers and local farmers,we applied Si in concentrations of 0,5.2,10.4,15.6,and 20.8μg/kg.At each concentration of added Si,the availability of soil N and P nutrients,soil microbial activity,numbers of ammonia-oxidizing bacteria and P-decomposing bacteria which means that the organic P is decomposed into inorganic nutrients which can be absorbed and utilized by plants,and urease and phosphatase activity first increased,and then decreased,as Si was added to the soil.These indicators reached their highest levels with a Si application rate of 15.6μg/kg,showing values respectively 19.78%,105.09%,8.34%,73.12%,130.36%,28.12%,and 20.15%higher than those of the controls.Appropriate Si application(10.4 to 15.6µg/kg)could significantly increase the richness of the soil microbial community involved in cycling of N and P nutrients in the soil.When the Si application rate was 15.6μg/kg,parameters for characterizing microbial abundance such as sequence numbers,operational taxonomic unit(OTU)number,and correlation indices of microbial community richness such as Chao1 index,the adaptive coherence estimator(ACE)index,Shannon index,and Simpson index all reached maximum values,with amounts increased by 14.46%,10.01%,23.80%,30.54%,0.18%,and 2.64%,respectively,compared with the control group.There is also a good correlation between N and P mineralization and addition of Si fertilizer.The correlation coefficients between the ratio of available P/total P(AP/TP)and the number of ammonia-oxidizing bacteria,AP/TP and acid phosphatase activity(AcPA),AP/TP and the Shannon index,the ratio of available N/total amount of N(AN/TN)and the number of ammoniated bacteria,and AN/TN and AcPA were 0.9290,0.9508,0.9202,0.9140,and 0.9366,respectively.In summary,these results revealed that enhancement of soil microbial community structure diversity and soil microbial activity by appropriate application of Si is the key ecological mechanism by which application of Si fertilizer improves N and P nutrient availability.

Chlorine substitution-dependent toxicities of polychlorinated biphenyls to the earthworm Eisenia fetida in soil

Polychlorinated biphenyls(PCBs)with different chlorine substitution patterns often coexist in e-waste-processing sites.However,the single and combined toxicity of PCBs to soil organisms and the influence of chlorine substitution patterns remain largely unknown.Herein,we evaluated the distinct in vivo toxicity of PCB28(a trichlorinated PCB),PCB52(a tetrachlorinated PCB),PCB101(a pentachlorinated PCB),and their mixture to earthworm Eisenia fetida in soil,and looked into the underlining mechanisms in an in vitro test using coelomocytes.After a 28-days exposure,all PCBs(up to 10 mg/kg)were not fatal to earthworms,but could induce intestinal histopathological changes and microbial community alterations in the drilosphere system,along with a significant weight loss.Notably,pentachlorinated PCBs with a low bioaccumulation ability showed greater inhibitory effects on the growth of earthworm than lowly chlorinated PCBs,suggesting that bioaccumulation was not the main determinant of chlorine substitution-dependent toxicity.Furthermore,in vitro assays showed that the highly chlorinated PCBs induced a high-percentage apoptosis of eleocytes in the coelomocytes and significantly activated antioxidant enzymes,indicating that the distinct cellular vulnerability to lowly/highly chlorinated PCBs was the main contributor to the PCBs toxicity.These findings emphasize the specific advantage of using earthworms in the control of lowly chlorinated PCBs in soil due to their high tolerance and accumulation ability.

Compounded chelating agent derived from fruit residue extracts effectively enhances Cd phytoextraction by Sedum alfredii

Chelating agent is known as the enhancer for metal phytoextraction;however,there is still a lack of efficient and environmentally sustainable chelators.Here,lemon residue extraction(LRE),prepared from 11 kinds of fruit wastes,was combined with N,N-bis(carboxymethyl)glutamic acid(GLDA),and tea saponin(T.S.)for the compounded plant-derived chelator(CPC),and their influences on Cd phytoextraction by the hyperaccumulator Sedum alfredii was evaluated.Among these fruits,the lemon residue extracted the most significant amount of Cd from the soil.The most effective CPC was at the volume ratio of three agents being 15:4:1(LRE:GLDA:T.S.).Compared with the deionized water,the solubility of three Cd minerals was increased by 85–256 times,and Cd speciation was substantially altered after CPC application.In the pot experiment,CPC addition caused evident increases in plant shoot biomass,Cd phytoextraction efficiency,and organic matter content compared with EDTA and nitrilotriacetic acid(NTA)application.CPC induced fewer changes in bacterial community composition compared with EDTA and had no pronounced influence on microbial biomass carbon and bacterialα-diversity,suggesting CPC had a subtle impact on the microbiological environments.Our study provides a theoretical base for the reutilization of fruit wastes and the development of environmental-friendly chelator that assists Cd phytoextraction.

Elevated carbon dioxide stimulates nitrous oxide emission in agricultural soils: A global meta-analysis

Elevated carbon dioxide (CO_(2))(e CO_(2)) has been shown to affect the nitrous oxide (N_(2)O) emission from terrestrial ecosystems by altering the interaction of plants,soils,and microorganisms.However,the impact of e CO_(2) on the N_(2)O emission from agricultural soils remains poorly understood.This meta-analysis summarizes the effect of e CO_(2) on N_(2)O emission in agricultural ecosystems and soil physiochemical and biological characteristics using 50 publications selected.The e CO_(2) effect values,which equal to the percentage changes of N_(2)O emission under e CO_(2),were calculated based on the natural logarithm of the response ratio to e CO_(2).We found that e CO_(2) significantly increased N_(2)O emission (by 44%),which varied depending on experimental conditions,agricultural practices,and soil properties.In addition,e CO_(2) significantly increased soil water-filled pore space (by 6%),dissolved organic carbon content (by11%),and nitrate nitrogen content (by 13%),but significantly reduced soil p H (by 1%).Moreover,e CO_(2) significantly increased soil microbial biomass carbon(by 28%) and soil microbial biomass nitrogen (by 7%) contents.Additionally,e CO_(2) significantly increased the abundances of ammonia-oxidizing bacteria(AOB) amo A (by 21%),nir K (by 15%),and nir S (by 15%),but did not affect the abundances of ammonia-oxidizing archaea (AOA) amo A and nos Z.Our findings indicate that e CO_(2) substantially stimulates N_(2)O emission in agroecosystems and highlight that optimization of nitrogen management and agronomic options might suppress this stimulation and aid in reducing greenhouse effect.