Migration and fate of polycyclic aromatic hydrocarbons in bioretention systems with different media:experiments and simulations

Polycyclic aromatic hydrocarbons(PAHs)present significant risks to human health owing to their carcinogenic,teratogenic,and mutagenic properties.The contamination of surface water with PAHs via runoff has become a prominent source of water pollution.While the capacity of bioretention systems to remove PAHs from runoff is recognized,the dynamics of PAH migration and degradation in these systems are not well-understood.This study aims to explain the migration and fate of PAHs in bioretention systems through a series of experiments and model simulations.This study constructed bioretention systems with three different media types and found that these systems achieved PAH load reductions exceeding 92%.Notably,naphthalene(NAP),fluoranthene(FLT),and pyrene(PYR)tended to accumulate in the media’s upper layer,at depths of 10 to 40 cm.To further analyze the migration and fate of PAHs during multi-site rainfall events and across prolonged operation,we applied the HYDRUS-1D model under three distinct scenarios.The findings of this study indicated that NAP degraded in 40 d,whereas FLT and PYR showed incomplete degradation after 120 d.During continuous rainfall events,there was no clear pattern of PAH accumulation;however,FLT and PYR persisted in the bioretention systems.The combination of experimental and simulation findings highlights the inevitable accumulation of PAHs during extended use of bioretention systems.This research provides a theoretical basis for improving operational efficiency,advancing PAH degradation in bioretention systems,and reducing their toxicity.

Effect of different degumming methods on the chemical composition and physicochemical properties of tiger nut (Cyperus esculentus L.)oil

Objectives:Tiger nut(Cyperus esculentus L.)oil is a promising edible oil that is rich in oleic acid.This study aimed to clarify the impact of different degumming methods on the chemical composition and physicochemical properties of crude tiger nut oil(CTO).Materials and Methods:Five degummed tiger nut oils were prepared by high-temperature water(HWDO),medium-temperature water(MWDO),sodium chloride solution(SDO),acidic solution(ADO),and enzymatic method(EDO),respectively.Results:Compared to that of CTO,the phospholipid contents of HWDO,MWDO,SDO,ADO,and EDO were reduced by 99.39%,97.18%,69.95%,63.77%,and 65.60%,respectively.For CTO and all degummed oils,the fatty acid and endogenous antioxidant(i.e.tocopherols,sterols,flavonoids,total phenolics,and carotenoids)contents showed only small differences,but showed significant differences in quality parameters.Both the oxidative stability index and ferric ion-reducing antioxidant power decreased significantly after degumming;the former decreased from 52.26 to 15.55-19.80 h,and the latter decreased from 5818.91 to 4348.73-4524.34μmol Trolox(TE)/kg.Conclusions:These changes are highly related to the removal of hydratable phospholipids.In short,EDO exhibited the lowest turbidity,whereas MWDO showed the best oxidative stability(19.80 h)and highest smoke point(230.0℃).This information can be utilized to improve the industrial production of tigernutoil.