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.

Enhanced degradation of organic contaminants by Fe(Ⅲ)/peroxymonosulfate process with L-cysteine

The difficulty in Fe(Ⅲ)/Fe(Ⅱ) conversion in the Fe(Ⅲ)/peroxymonosulfate(PMS) process limits its efficiency and application.Herein,L-cysteine(Cys),a green natural organic ligand with reducing capability,was innovatively introduced into Fe(Ⅲ)/PMS to construct an excellent Cys/Fe(Ⅲ)/PMS process.The Cys/Fe(Ⅲ)/PMS process,at room temperature,can degrade a variety of organic contaminants,including dyes,phenolic compounds,and pharmaceuticals.In subsequent experiments with acid orange 7(A07),the AO7 degradation efficiency followed pseudo-first-order kinetic which exhibited an initial "fast stage" and a second "slow stage".The rate constant values ranged depending on the initial Cys,Fe(Ⅲ),PMS,and AO7 concentrations,reaction temperature,and pH values.In addition,the presence of Cl^(-),NO_(3)^(-),and SO_(4)^(2-) had negligible impact while HCO_(3)^(-) and humic acid inhibited the degradation of AO7.Furthermore,radical scavenger experiments and methyl phenyl sulfoxide(PMSO) transformation assay indicated that sulfate radical,hydroxyl radical,and ferryl ion(Fe(Ⅳ)) were the dominant reactive species involved in the Cys/Fe(Ⅲ)/PMS process.Finally,based on the results of gas chromatography-mass spectrometry,several AO7 degradation pathways,including N=N cleavage,hydroxylation,and ring opening were proposed.This study provided a new insight to improve the efficiency of Fe(Ⅲ)/PMS process by accelerating Fe(Ⅲ)/Fe(Ⅱ)cycle with Cys.