Dissolved organic matter(DOM)in rivers is a critical regulator of the cycling and toxicity of pollutants and the behavior of DOM is a key indicator for the health of the environment.We investigated the sources and cha...Dissolved organic matter(DOM)in rivers is a critical regulator of the cycling and toxicity of pollutants and the behavior of DOM is a key indicator for the health of the environment.We investigated the sources and characteristics of DOM in surface water and sediment samples of the Wei River,China.Dissolved organic carbon(DOC)concentration and ultraviolet absorbance at 254 nm(UV254)increased in the surface water and were decreased in the sediment downstream,indicating that the source of DOM in the water differed from the sediment.Parallel factor(PARAFAC)analysis of the excitation-emission matrices(EEM)revealed the presence of terrestrial humus-like,microbial humus-like and tryptophan-like proteins in the surface water,whereas the sediment contained UVA humic-like,UVC humic-like and fulvic-like in the sediment.The DOM in the surface water and sediment were mainly derived from microbial metabolic activity and the surrounding soil.Surface water DOM displayed greater photodegradation potential than sediment DOM.PARAFAC analysis indicated that the terrestrial humic-like substance in the water and the fulvic-like component in the sediment decomposed more rapidly.These data describe the characteristics of DOM in the Wei River and are crucial to understanding the fluctuations in environmental patterns.展开更多
Environmentally persistent free radicals(EPFRs)in humic substances play an essential role in soil geochemical processes.Light is known to induce EPFRs formation for dissolved organic matter in aquatic environments;how...Environmentally persistent free radicals(EPFRs)in humic substances play an essential role in soil geochemical processes.Light is known to induce EPFRs formation for dissolved organic matter in aquatic environments;however,the impacts of light irradiation on the variation of EPFRs in soil humic substances remain unclear.In this study,humic acid,fulvic acid,and humin were extracted from peat soil and then in situ irradiated using simulated sunlight.Electron paramagnetic resonance spectroscopy results showed that with the increasing irradiation time,the spin densities and g-factors of humic substances rapidly increased during the initial 20 min and then gradually reached a plateau.After irradiation for 2h,the maximum spin density levels were up to 1.63×10^17,2.06×10^17,and 1.77×10^×10^17 spins/g for the humic acid,fulvic acid,and humin,respectively.And the superoxide radicals increased to 1.05×10^l4-1.46×10^14spins/g while the alkyl radicals increased to 0.47×10^14-1.76×10^14 spins/g.The light-induced EPFRs were relatively unstable and readily returned back to their original state under dark and oxic conditions.Significant positive correlations were observed between the concentrations of EPFRs and reactive radical species(R2=0.65-0.98,/?<0.05),which suggested that the newly produced EPFRs contributed to the formation of reactive radical species.Our findings indicate that under the irradiation humic substances are likely to be more toxic and reactive in soil due to the formation of EPFRs.展开更多
The role of humic substance-associated persistent free radicals(PFRs)in the fate of organic contaminants under various redox conditions remains unknown.This study examined the characterization of original metal-free p...The role of humic substance-associated persistent free radicals(PFRs)in the fate of organic contaminants under various redox conditions remains unknown.This study examined the characterization of original metal-free peat humin(HM),and HM treated with varying concentrations of H2O2 and L-ascorbic acid(VC)(assigned as H2O2-HM and VC-HM).The concentration of PFRs in HM increased with the addition of VC/H2O2 at concentrations less than 0.08 mol/L.The evolution of PFRs in HM under different environmental conditions(e.g.,oxic/anoxic and humidity)was investigated.Two types of PFRs were detected in HM:a relatively stable radical existed in the original sample,and the other type,which was generated by redox treatments,wa s relatively unstable.The spin densities of VC/H2O2-HM readily returned to the original value under relatively high humidity and oxic conditions.During this process,the HM-associated"unstable"free radicals released an electron to O2,inducing the formation of reactive oxygen species(ROS,i.e.,·OH and·O2-).Th e generated ROS promoted the degradation of polycyclic aromatic hydrocarbons based on the radical quenching measurements.The transformation rates followed the order naphthalene>phenanthrene>anthracene>benzo[a]pyrene.Our results provide valuable insight into the HM-induced transformation of organic contaminants under natural conditions.展开更多
基金the National Natural Science Foundation of China(Grant No.41977307).
文摘Dissolved organic matter(DOM)in rivers is a critical regulator of the cycling and toxicity of pollutants and the behavior of DOM is a key indicator for the health of the environment.We investigated the sources and characteristics of DOM in surface water and sediment samples of the Wei River,China.Dissolved organic carbon(DOC)concentration and ultraviolet absorbance at 254 nm(UV254)increased in the surface water and were decreased in the sediment downstream,indicating that the source of DOM in the water differed from the sediment.Parallel factor(PARAFAC)analysis of the excitation-emission matrices(EEM)revealed the presence of terrestrial humus-like,microbial humus-like and tryptophan-like proteins in the surface water,whereas the sediment contained UVA humic-like,UVC humic-like and fulvic-like in the sediment.The DOM in the surface water and sediment were mainly derived from microbial metabolic activity and the surrounding soil.Surface water DOM displayed greater photodegradation potential than sediment DOM.PARAFAC analysis indicated that the terrestrial humic-like substance in the water and the fulvic-like component in the sediment decomposed more rapidly.These data describe the characteristics of DOM in the Wei River and are crucial to understanding the fluctuations in environmental patterns.
基金This work was supported by the National Natural Science Foundation of China(Grant No.41877126)National Key R&D Program of China(Grant No.2018YFC1802004)+2 种基金China Postdoctoral Science Foundation funded project(No.2019M650278)Shaanxi Key R&D Program of China(No.2019ZDLNY01-02-01)Shaanxi Science Fund for Distinguished Young Scholars(Grant No.2019JC-18).
文摘Environmentally persistent free radicals(EPFRs)in humic substances play an essential role in soil geochemical processes.Light is known to induce EPFRs formation for dissolved organic matter in aquatic environments;however,the impacts of light irradiation on the variation of EPFRs in soil humic substances remain unclear.In this study,humic acid,fulvic acid,and humin were extracted from peat soil and then in situ irradiated using simulated sunlight.Electron paramagnetic resonance spectroscopy results showed that with the increasing irradiation time,the spin densities and g-factors of humic substances rapidly increased during the initial 20 min and then gradually reached a plateau.After irradiation for 2h,the maximum spin density levels were up to 1.63×10^17,2.06×10^17,and 1.77×10^×10^17 spins/g for the humic acid,fulvic acid,and humin,respectively.And the superoxide radicals increased to 1.05×10^l4-1.46×10^14spins/g while the alkyl radicals increased to 0.47×10^14-1.76×10^14 spins/g.The light-induced EPFRs were relatively unstable and readily returned back to their original state under dark and oxic conditions.Significant positive correlations were observed between the concentrations of EPFRs and reactive radical species(R2=0.65-0.98,/?<0.05),which suggested that the newly produced EPFRs contributed to the formation of reactive radical species.Our findings indicate that under the irradiation humic substances are likely to be more toxic and reactive in soil due to the formation of EPFRs.
基金This work is supported by the National Natural Science Foundation of China(Grant Nos.41571446 and 41877126)Shaanxi Science Fund for Distinguished Young Scholars(Grant No.2019JC-18)National Key Technologies R&D Program(Grant No.2018 YFC 1802004)。
文摘The role of humic substance-associated persistent free radicals(PFRs)in the fate of organic contaminants under various redox conditions remains unknown.This study examined the characterization of original metal-free peat humin(HM),and HM treated with varying concentrations of H2O2 and L-ascorbic acid(VC)(assigned as H2O2-HM and VC-HM).The concentration of PFRs in HM increased with the addition of VC/H2O2 at concentrations less than 0.08 mol/L.The evolution of PFRs in HM under different environmental conditions(e.g.,oxic/anoxic and humidity)was investigated.Two types of PFRs were detected in HM:a relatively stable radical existed in the original sample,and the other type,which was generated by redox treatments,wa s relatively unstable.The spin densities of VC/H2O2-HM readily returned to the original value under relatively high humidity and oxic conditions.During this process,the HM-associated"unstable"free radicals released an electron to O2,inducing the formation of reactive oxygen species(ROS,i.e.,·OH and·O2-).Th e generated ROS promoted the degradation of polycyclic aromatic hydrocarbons based on the radical quenching measurements.The transformation rates followed the order naphthalene>phenanthrene>anthracene>benzo[a]pyrene.Our results provide valuable insight into the HM-induced transformation of organic contaminants under natural conditions.
