Contaminants of emerging concern in landfill leachate in China:A review

This review paper summarizes the occurrence,removal and ecological risk of contaminants of emerging concern(CEC)reported in landfill leachate in China since 1996(43 studies in 10 regions).Results show that many more studies are conducted in developed southeastern China than in developing western and northeastern regions in China.Phthalate esters(PAEs,with 15 studies)and pharmaceuticals and personal care products(PPCPs,with 13 studies)are the two most frequently studied CEC classes.Concentrations of nine CECs classes were in a wide range from 0.03(organochlorine pesticides)to approximately 4500 mg/L(alkylphenol polyethoxylates/bisphenol analog).Meanwhile,concentrations of CEC compounds range from below detection limit(e.g.doxycycline)to approximately 4500 mg/L(bisphenol A).Several PAEs(diethyl phthalate,di-n-butyl phthalate,and di(2-ethylhexyl)phthalate)and PPCPs(diclofenac and gemfibrizol)have significant variation between sampling sites.Typically,advanced treatment processes can achieve higher removal efficiencies of CEC compounds from landfill leachate compared with conventional treatment processes.Furthermore,environmental risk assessments of CEC compounds in treated landfill leachate using a risk quotient method show that 2(substituted)polycyclic aromatic hydrocarbons(sPAHs)(benzo(a)anthracene and benzo(b)fluoranthene),2 PPCPs(bezafibrate and sulfapyridine),g-hexachlorocyclohexane,and bisphenol A pose high risk.The importance of monitoring and potential risks of CECs in the leachate to vicinity aquatic environment cross China is addressed.

Guidelines for rational design of high-performance absorbents:A case study of zeolite adsorbents for emerging pollutants in water

Rational design is important to achieve high-performance sorbents used to remove the contaminants of emerging concern(CECs) from water.However, it is hard to propose effective design guidelines due to the lack of a clear understanding of the interaction mechanisms. By means of systematic quantum chemical computations, as a case study, we investigated the interactions between zeolite X/M^(n+)-zeolite X(Si/Al=1,M^(n+)=Cu^(2+) and Ni^(2+)) and three commonly used CECs(namely salicylic acid, carbamazepine and ciprofloxacin) in water to clarify the adsorption mechanisms. Our computations found that anionic salicylic acid cannot be adsorbed by neither zeolite X nor M^(n+)-zeolite X in neutral water due to the high electrostatic repulsion. In comparison, carbamazepine and ciprofloxacin have favorable binding energies with both zeolite X and M^(n+)-zeolite X, and their interactions with M^(n+)-zeolite X are stronger due to the joint effects of H-bond, metal complexation and electrostatic interaction. The adsorption loading of ciprofloxacin, which has a large molecular size, on M^(n+)-zeolite X is limited due to the steric hindrance. In general, steric hindrance, electrostatic interaction, H-bond and metal complexation are dominant factors for the examined systems in this study. Thus, for the design of high-performance absorbing materials, we should fully consider the molecular properties of pollutants(molecular size, surface electrostatic potential and atomic type, etc.), and properly enhance the favorable effects and avoid the unfavorable factors as much as possible under the guidance of the interaction mechanisms.

Zeolite-templated carbons as effective sorbents to remove methylsiloxanes and derivatives:A computational screening

Though widely used in our daily lives,volatile methylsiloxanes and derivatives are emerging contaminants and becoming a high-priority environment and public health concern.Developing effective sorbent materials can remove siloxanes in a cost-effective manner.Herein,by means of Grand Canonical Monte Carlo(GCMC)simulations,we evaluated the potentials of the recently proposed 68 stable zeolite-templated carbons(ZTCs)(PNAS 2018,115,E8116-E8124)for the removal of four linear methylsiloxanes and derivatives as well as two cyclic methylsiloxanes by the calculated average loading and average adsorption energy values.Four ZTCs,namely ISV,FAU1,FAU3,and H8326836,were identified with the top 50%adsorption performance toward all the six targeted contaminants,which outperform activated carbons.Further first principles computations revealed that steric hindrance,electrostatic interactions(further enhanced by charge transfer),and CH-p interactions account for the outstanding adsorption performance of these ZTCs.This work provides a quick procedure to computationally screen promising ZTCs for siloxane removal,and help guide future experimental and theoretical investigations.

Co-contaminants of microplastics in two seabird species from the Canadian Arctic

Through ingestion and subsequent egestion,Arctic seabirds can bioaccumulate microplastics at and around their colony breeding sites.While microplastics in Arctic seabirds have been well documented,it is not yet understood to what extent these particles can act as transport vehicles for plastic-associated contaminants,including legacy persistent organic pollutants(POPs),trace metals,and organic additives.We investigated the occurrence and pattern of organic and inorganic co-contaminants of microplastics in two seabird species from the Canadian Arctic-northern fulmar(Fulmarus glacialis)and black-legged kittiwake(Rissa tridactyla).We found that fulmars had higher levels of plastic contamination and emerging organic compounds(known to be plastic additives)than kittiwakes,whereas higher concentrations of legacy POPs were found in kittiwakes than the fulmars.Furthermore,fulmars,the species with the much larger foraging range(~200 km),had higher plastic pollution and overall contaminant burdens,indicating that birds may be acting as long-range transport vectors for plasticassociated pollution.Our results suggest a potential connection between plastic additive contamination and plastic pollution burdens in the bird stomachs,highlighting the importance of treating plastic particles and plastic-associated organic additives as co-contaminants rather than separate pollution issues.