Perfluorooctanoic acid （PFOA）, a persistent organic pollutant, receives increasing concerns due to its worldwide occurrence and resistance to most conventional treatment processes. The photochemical decomposition by...Perfluorooctanoic acid （PFOA）, a persistent organic pollutant, receives increasing concerns due to its worldwide occurrence and resistance to most conventional treatment processes. The photochemical decomposition by 185 nm vacuum ultraviolet （VUV） is one of the efficient methods for PFOA decomposition. The effects of pH on PFOA decomposition in nitrogen atmosphere or oxygen atmosphere were investigated. At its original pH （4.5） of PFOA aqueous solution, PFOA decomposed efficiently both in nitrogen and in oxygen atmosphere. However, when the pH increased to 12.0, PFOA decomposition was greatly inhibited in oxygen atmosphere, while it was greatly accelerated in nitrogen atmosphere with a very short half-life time （9 rain）. Furthermore, fluorine atoms originally contained in PFOA molecules were almost completely transformed into fluoride ions. Two decomposi- tion pathways have been proposed to explain the PFOA decomposition under different conditions. In acidic and neutral solutions, PFOA predominantly decomposes via the direct photolysis in both atmospheres; while in the alkaline solution and in the absence of oxygen, the decomposition of PFOA is mainly induced by hydrated electrons.展开更多
Perfluorinated compounds(PFCs)are ubiquitously distributed in the environment mainly as perfluorocarboxylic acids(PFCAs)and perfluoroalkyl sulfonates(PFASs).In this paper,six PFCAs and two PFASs were quantified in sur...Perfluorinated compounds(PFCs)are ubiquitously distributed in the environment mainly as perfluorocarboxylic acids(PFCAs)and perfluoroalkyl sulfonates(PFASs).In this paper,six PFCAs and two PFASs were quantified in surface and tap water samples from 12 sites around Lake Taihu near Shanghai City in East China.Predominant PFCs were perfluorooctanoic acid(PFOA)and perfluorooctane sulfonate(PFOS),of which the concentration ranges were 6.8–206 and 1.2–45 ng·L^(–1),the geometric means were 35.3 and 9.4 ng·L^(–1),and the median(quartile range)values were 31.4(34.4)and 10.4(10.7)ng·L^(–1),respectively.Other PFCs were also detected but in much lower concentrations than PFOA.The sources of the PFCs were expected to be direct industrial discharges in the Lake Taihu area,and this area was also a possible source of PFCs contaminations in Shanghai district in the downstream.PFCs distributions were found different in the upstream,downstream and north part of Lake Taihu.Occurrences of PFCs in the tap water in Lake Taihu area indicated their exposure to the local people.A brief estimation of the environmental risks by PFCs implied no acute or immediate risks from PFCs to local human health,but chronic risks from PFOA in the tap water should be considered in the downstream regions.展开更多
基金supported by the National Basic Research Program (973) of China (No. 2013CB632403)the National Natural Science Foundation (Nos. 21267006, 21221004)+1 种基金the Tsinghua University Initiative Scientific Research Program No. 20131089251the Collaborative Innovation Center for Regional Environmental Quality
文摘Perfluorooctanoic acid （PFOA）, a persistent organic pollutant, receives increasing concerns due to its worldwide occurrence and resistance to most conventional treatment processes. The photochemical decomposition by 185 nm vacuum ultraviolet （VUV） is one of the efficient methods for PFOA decomposition. The effects of pH on PFOA decomposition in nitrogen atmosphere or oxygen atmosphere were investigated. At its original pH （4.5） of PFOA aqueous solution, PFOA decomposed efficiently both in nitrogen and in oxygen atmosphere. However, when the pH increased to 12.0, PFOA decomposition was greatly inhibited in oxygen atmosphere, while it was greatly accelerated in nitrogen atmosphere with a very short half-life time （9 rain）. Furthermore, fluorine atoms originally contained in PFOA molecules were almost completely transformed into fluoride ions. Two decomposi- tion pathways have been proposed to explain the PFOA decomposition under different conditions. In acidic and neutral solutions, PFOA predominantly decomposes via the direct photolysis in both atmospheres; while in the alkaline solution and in the absence of oxygen, the decomposition of PFOA is mainly induced by hydrated electrons.
基金the National Science and Technology Pillar Program of China(Grant No.2006BAC19B06)the Major Projects on Control and Rectification of Water Body Pollution(2009ZX07313-003).
文摘Perfluorinated compounds(PFCs)are ubiquitously distributed in the environment mainly as perfluorocarboxylic acids(PFCAs)and perfluoroalkyl sulfonates(PFASs).In this paper,six PFCAs and two PFASs were quantified in surface and tap water samples from 12 sites around Lake Taihu near Shanghai City in East China.Predominant PFCs were perfluorooctanoic acid(PFOA)and perfluorooctane sulfonate(PFOS),of which the concentration ranges were 6.8–206 and 1.2–45 ng·L^(–1),the geometric means were 35.3 and 9.4 ng·L^(–1),and the median(quartile range)values were 31.4(34.4)and 10.4(10.7)ng·L^(–1),respectively.Other PFCs were also detected but in much lower concentrations than PFOA.The sources of the PFCs were expected to be direct industrial discharges in the Lake Taihu area,and this area was also a possible source of PFCs contaminations in Shanghai district in the downstream.PFCs distributions were found different in the upstream,downstream and north part of Lake Taihu.Occurrences of PFCs in the tap water in Lake Taihu area indicated their exposure to the local people.A brief estimation of the environmental risks by PFCs implied no acute or immediate risks from PFCs to local human health,but chronic risks from PFOA in the tap water should be considered in the downstream regions.
