Correlation between Cr^(6+) and Mn^(2+) Adsorption in Rock-soil Medium with Combined Pollution

[Objective] The aim was to study the correlation between Cr6+ and Mn2+ adsorption in rock-soil medium with combined pollution. [Method] Combining single Cr6+ and Mn2+ adsorption test with combined pollution test, the adsorption laws of Cr6+ and Mn2+ were studied, and the correlation between Cr6+ and Mn2+ adsorption was analysed by using correlation analysis and regression analysis. [Result] According to the comparative analysis on adsorption tests, the adsorption time, adsorption amount and adsorption speed of Cr6+ and Mn2+ were obviously distinct in single adsorption test and combined adsorption test. Correlation analysis revealed that there was a significantly positive correlation between Cr6+ and Mn2+, and there existed addition effects between Cr6+ and Mn2+ in regression analysis, that is, the adsorption of Cr6+ by the soil tested would be enhanced by Mn2+. [Conclusion] The research could provide scientific references for environmental control and environmental management.

Effect of Zn^(2+)-Cu^(2+)combined heavy metal on mechanical properties and microstructure of clayey soil

The strength deterioration mechanism of soil polluted by heavy metals plays a crucial role in the research of mine site pollution.In this study,an unconfined compressive strength(UCS)test,a pH test,a scanning electron microscopy(SEM)test,a low filed nuclear magnetic resonance(NMR)test,and an X-ray diffraction(XRD)test were conducted on Zn^(2+),Cu^(2+) and the combination of Zn^(2+) and Cu^(2+) polluted soil to investigate the strength deterioration mechanism.The results show that both the UCS and pH value of soil decrease with increasing heavy metal concentration.The UCS of Zn^(2+)-Cu^(2+) combined polluted soil is between Zn^(2+) and Cu^(2+) polluted soil at the same total concentration.However,the deterioration rate of combined heavy metal polluted soil is less than the sum of deterioration rate of the two single polluted soils at the same total concentration.In addition,heavy metal cations in polluted soil cause flocculent gels of cosmids to shrink,the micropores to become smaller and the macropores to become larger.The porosity increases slightly with the increase of heavy metal concentration due to decreased pH value.The results from SEM,low field NMR,and pH could explain the dynamic evolution process of soil structure with different heavy metals and concentrations,which provides an experimental basis for mine-site polluted heavy metal treatment technology and the prediction of clayey soil strength deterioration.

Feasibility of Isolation Remediation Technology for Heavy Metal Contaminated Soil

This paper discussed current situations of researches about the isolation remediation technology " soil barrier and landfill technology" and " physical isolation remediation technology" for heavy metal contaminated soil in mining areas.In view of defects of current technologies,it introduced a new isolation remediation technology,of which the new isolation materials were mixed by slaked lime,soil,find sand,and clay mineral in certain proportion.The new isolation remediation technology is expected to realize isolation remediation of heavy metal combined pollution of soil through chemical passivation of slaked lime and physical adsorption function of clay minerals or activated carbons.

Effects of combined antibiotics on nitrification, bacteria and antibiotic resistance genes in activated sludge: Insights from legacy effect of antibiotics

The effect of combined antibiotics exposure on nitrogen removal,microbial community assembly and proliferation of antibiotics resistance genes(ARGs)is a hotspot in activated sludge system.However,it is unclear that how the historical antibiotic stress affects the subsequent responses of microbes and ARGs to combined antibiotics.In this study,the effects of combined sulfamethoxazole(SMX)and trimethoprim(TMP)pollution on activated sludge under legacy of SMX or TMP stress with different doses(0.005-30 mg/L)were investigated to clarify antibiotic legacy effects.Nitrification activity was inhibited under higher level of combined exposure but a high total nitrogen removal(∼70%)occurred.Based on the full-scale classification,the legacy effect of past antibiotic stress had a marked effect on community composition of conditionally abundant taxa(CAT)and conditionally rare or abundant taxa(CRAT).Rare taxa(RT)were the keystone taxa in the microbial network,and the responses of hub genera were also affected by the legacy of antibiotic stress.Nitrifying bacteria and genes were inhibited by the antibiotics and aerobic denitrifying bacteria(Pseudomonas,Thaurea and Hydrogenophaga)were enriched under legacy of high dose,as were the key denitrifying genes(napA,nirK and norB).Furthermore,the occurrences and co-selection relationship of 94 ARGs were affected by legacy effect.While,some shared hosts(eg.,Citrobacter)and hub ARGs(eg.,mdtD,mdtE and acrD)were identified.Overall,antibiotic legacy could affect responses of activated sludge to combined antibiotic and the legacy effect was stronger at higher exposure levels.

A passive sampler for synchronously measuring inorganic and organic pollutants in sediment porewater:Configuration and field application

In situ measurement of multiple pollutants coexisting in sediment porewater is an essential step in comprehensively assessing the bioavailability and risk of pollutants,but to date,this needs to be better developed.In this study,a passive sampler,consisting of an“I-shaped”supporting frame and inorganic/organic sampling units,incorporating equilibrium dialysis theory and kinetic/equilibrium sorption principle,was developed for the synchronous measurement of inorganic(e.g.,phosphorus and metal(loid)s)and organic pollutants(e.g.,parent and substituted PAHs).The equilibrium time and sampling rates were explored in laboratory tests to support in situ application.Profiles of pollutants in porewater within a vertical resolution of centimeters,i.e.,1 cm and 2 cm for inorganic and organic pollutants,respectively,were obtained by field deployment of the sampler for further estimation of diffusive fluxes across the sediment-water interface.The results suggested that the role of sediments for a specific pollutant may change(e.g.,from“sink”to“source”)during the sampling time.This study demonstrated the feasibility of synchronous measurement of inorganic and organic pollutants in sediment porewater by the passive sampler.In addition,it provided new insight for further investigation into the combined pollution effects of various pollutants in sediments.

Remediation performance and mechanisms of Cu and Cd contaminated water and soil using Mn/Al-layered double oxide-loaded biochar

The combined pollution of heavy metals is ubiquitous worldwide.Mn/Al-layered double oxide-loaded crab shells biochar (LDO/BC) was prepared,so as to remediate the combined pollution of Cd and Cu in soil and water.The pristine and used LDO/BC were characterized and the results revealed that the layered double oxide was successfully loaded on crab shells biochar (BC) and metal element Ca in crab shells was beneficial to the formation of more regular layered and flake structure.The maximal adsorption capacity (Qm) of LDO/BC for aqueous Cu^(2+)and Cd^(2+)was 66.23 and 73.47 mg/g,respectively.LDO/BC and BC were used to remediate e-waste-contaminated soil for the first time and exhibited highly efficient performance.The extraction amount of Cu and Cd in the contaminated soil by diethylene triamine penta-acetic acid (DTPA) after treating with 5% LDO/BC was significantly reduced from 819.84 to 205.95 mg/kg (with passivation rate 74.8%) and 8.46 to 4.16 mg/kg(with passivation rate 50.8%),respectively,inferring that the bioavailability of heavy metals declined remarkably.The experimental result also suggested that after remediation by LDO/BC the exchangeable and weak acid soluble Cu and Cd in soil translated to reducible,residual and oxidizable fraction which are more stable state.Precipitation,complexation and ion exchange were proposed as the possible mechanisms for Cd and Cu removal.In general,these experiment results indicate that LDO/BC can be a potentially effective reagent for remediation of heavy metal contaminated water and soil.

Effects of soil metal(loid)s pollution on microbial activities and environmental risks in an abandoned chemical smelting site

Abandoned chemical smelting sites containing toxic substances can seriously threaten and pose a risk to the surrounding ecological environment.Soil samples were collected from different depths(0 to 13 m)and analyzed for metal(loid)s content and fractionation,as well as microbial activities.The potential ecological risk indices for the different soil depths(ordered from high to low)were:1 m(D-1)>surface(S-0)>5 m(D-5)>13 m(D-13)>9 m(D-9),ranging between 1840.65-13,089.62,and representing extremely high environmental risks,of which Cd(and probably not arsenic)contributed to the highest environmental risk.A modified combined pollution risk index(MCR)combining total content and mobile proportion of metal(loid)s,and relative toxicities,was used to evaluate the degree of contamination and potential environmental risks.For the near-surface samples(S-0 and D-1 layers),the MCR considered that As,Cd,Pb,Sb,and Zn achieved high and alarming degrees of contamination,whereas Fe,Mn,and Ti were negligible or low to moderate pollution degrees.Combined microcalorimetry and enzymatic activity measurements of contaminated soil samples were used to assess the microbial metabolic activity characteristics.Correlation analysis elucidated the relationship between metal(loid)s exchangeable fraction or content and microbial activity characteristics(p<0.05).The microbial metabolic activity in the D-1 layer was low presumably due to heavy metal stress.Enzyme activity indicators and microcalorimetric growth rate(k)measurements were considered sensitive indicators to reflect the soil microbial activities in abandoned chemical smelting sites.

Growth responses of the newly-discovered Cd-hyperaccumulator Rorippa globosa and its accumulation characteristics of Cd and As under joint stress of Cd and As

Rorippa globosa has been identified as a newly-found Cd-hyperaccumulating species.In the present study,growth responses of Rorippa globosa and its accumulation characteristics of Cd and As were examined under joint stress of Cd and As.The results showed that Cd and As had an antagonistic effect on enhancing the growth of Rorippa globosa plants and Cd uptake and accumulation under the low concentration Cd and As treatments.When the concentra-tion of Cd in the soil was 10 mg/kg and the concentration of As was 50 mg/kg,the highest growing height of the plant was up to 35.9 cm and the dry weight of the shoots was up to 2.2 g/pot,respectively.Meanwhile,the accumulation of Cd in the leaves under the joint stress was higher than that at the same level under single Cd pollution.However,there were synergic adverse effects on plant growth and Cd uptake under the combined pollution from a high concentration of Cd and As.Meanwhile,the accumulation of As in the roots was greater than that in the shoots,the translocation factor(TF)was h0.3 and the bioaccumulation factor(BF)was h0.6,thus showing that Rorippa globosa had an excluding effect on As uptake.These results confirmed that Rorippa globosa had a strong tolerant ability to the joint stress of Cd and As,and the potential for phytoremediation of soils contaminated by Cd and As.

Preparation of hollow-fiber nanofiltration membranes of high performance for effective removal of PFOA and high resistance to BSA fouling

Nanofiltration(NF)process has become one of the most promising technologies to remove micro-organic combined water pollution.Developing a NF membrane material with efficient separation for perfluorooctanoic acid(PFOA)combined pollution is highly desired,this manuscript targets this unmet need specifically.In this work,hydrophilic SiO_(2)nanoparticles with various contents blended with carboxylic multiwalled carbon nanotube were used to modify poly(m-phenylene isophthal amide)(SiO_(2)/CMWCNT/PMIA)hollow fiber NF membrane.The modified membrane with 0.1 wt%SiO_(2)doping exhibits way better fouling resistance with irreversible fouling ratio decreased dramatically from 18.7%to 2.3%,and the recovery rate of water flux increases significantly from 81.2%to 97.7%.The separation experiment results had confirmed that the modified membrane could improve the rejection from 97.2%to 98.6%for perfluorooctanoic acid(PFOA)and its combined pollution with bovine serum albumin(BSA).It is clear that this reported SiO_(2)/CMWCNT/PMIA hollow fiber NF membrane potentially could be applied in water treatment.This research also provides a theoretical basis for efficiently removal of PFOA and its combined pollution by NF membrane.