17α-Ethynylestradiol（EE2） in natural waters may cause adverse effects on organisms due to its high estrogenic potency. Laboratory studies were performed to study the effects of a local humic acid（LHA）, fulvic aci...17α-Ethynylestradiol（EE2） in natural waters may cause adverse effects on organisms due to its high estrogenic potency. Laboratory studies were performed to study the effects of a local humic acid（LHA）, fulvic acid（LFA） and Aldrich humic acid（AHA） on the photochemical behavior and estrogenic potency of EE2. Here photolytic experiments demonstrated that pure aqueous EE2 could undergo direct and self-sensitized photodegradation at a global rate of 0.0068 hr^-1.Photodegradation rate of EE2 in 5.0 mg/L dissolved humic substances（DHS） was determined to be 0.0274, 0.0296 and 0.0254 hr^-1 for LHA, LFA and AHA, respectively. Reactive oxygen species（ROS） and triplet dissolved humic substances（^3DHS＊） scavenging experiments indicated that the promotion effect of DHS on EE2 photodegradation was mainly aroused by the reactions of HOU（35%–50%）,~1O2（〈10%） andDHS＊（22%–34%）. However, the photodegradation of EE2 could also be inhibited when DHS exceeded the threshold of 10 mg/L. Three hydroxylation products of EE2 were identified using GC–MS and their formation pathways were also proposed. In vitro estrogenicity tests showed that EE2 was transformed into chemicals without estrogenic potency. These findings could extend our knowledge on the photochemical behaviors of steroid estrogens in sunlit natural waters.展开更多
Humic substances constitute the major organic fractions of soils, sediments and natural waters, and play a dominant role in the binding, mobilization, transport and ultimate fate of organic contaminants in subsurface ...Humic substances constitute the major organic fractions of soils, sediments and natural waters, and play a dominant role in the binding, mobilization, transport and ultimate fate of organic contaminants in subsurface systems. In this paper, two humic acid samples, Guanting and Tianjin, with different origin and chemical compositions have been investigated with AFM imaging for their adsorption and aggregation behaviors on mica. While the Tianjin humic sample is found to form small spheres with 250 to 330 nm in diameter at lower concentrations, irregular loop-chain assemblies of hundreds of nanometer in diameter with the chain width of about 40 nm are dominant for the Guanting humic sample, which may attribute to the more polar aliphatic fractions in the chemical composition in the latter. The heterogeneous and polydisperse nature of humic substances with multiple structural features, such as sponge-like structures, perforated sheets, aggregate of spheres, branches and chain-like assemblies etc., is apparent at higher concentrations for both humic samples, showing morphologically new evidence for the dominant view of the humic dual-mode sorption model. With naphthalene introduced, the assemblies of Guanting humic substances clearly become more compact with significantly narrowed branches and less porous the perforated sheet-like structures. It is indica- tive of that smaller nanometer scale rings present along the perforated assemblies could potentially represent hydrophobic domains, which may facilitate the adsorption and aggregation of naphthalene onto the natural particle surfaces and therefore lead to an important role of dissolved humic sub- stances in the sorption of environmental pollutants.展开更多
基金sponsored by the National Natural Science Foundation of China(No.41401558)the Application Fundamental Key Basic Research Foundation of Yunnan Province,China(No.2013FA011)+1 种基金the Education Department Science Research Foundation of Yunnan Province,China(No.2014J022)the China Postdoctoral Science Foundation(No.2014T70887)
文摘17α-Ethynylestradiol（EE2） in natural waters may cause adverse effects on organisms due to its high estrogenic potency. Laboratory studies were performed to study the effects of a local humic acid（LHA）, fulvic acid（LFA） and Aldrich humic acid（AHA） on the photochemical behavior and estrogenic potency of EE2. Here photolytic experiments demonstrated that pure aqueous EE2 could undergo direct and self-sensitized photodegradation at a global rate of 0.0068 hr^-1.Photodegradation rate of EE2 in 5.0 mg/L dissolved humic substances（DHS） was determined to be 0.0274, 0.0296 and 0.0254 hr^-1 for LHA, LFA and AHA, respectively. Reactive oxygen species（ROS） and triplet dissolved humic substances（^3DHS＊） scavenging experiments indicated that the promotion effect of DHS on EE2 photodegradation was mainly aroused by the reactions of HOU（35%–50%）,~1O2（〈10%） andDHS＊（22%–34%）. However, the photodegradation of EE2 could also be inhibited when DHS exceeded the threshold of 10 mg/L. Three hydroxylation products of EE2 were identified using GC–MS and their formation pathways were also proposed. In vitro estrogenicity tests showed that EE2 was transformed into chemicals without estrogenic potency. These findings could extend our knowledge on the photochemical behaviors of steroid estrogens in sunlit natural waters.
基金This research was supported by the National Natural Science Foundation of China (Grant Nos. 20037010 and 20277042).
文摘Humic substances constitute the major organic fractions of soils, sediments and natural waters, and play a dominant role in the binding, mobilization, transport and ultimate fate of organic contaminants in subsurface systems. In this paper, two humic acid samples, Guanting and Tianjin, with different origin and chemical compositions have been investigated with AFM imaging for their adsorption and aggregation behaviors on mica. While the Tianjin humic sample is found to form small spheres with 250 to 330 nm in diameter at lower concentrations, irregular loop-chain assemblies of hundreds of nanometer in diameter with the chain width of about 40 nm are dominant for the Guanting humic sample, which may attribute to the more polar aliphatic fractions in the chemical composition in the latter. The heterogeneous and polydisperse nature of humic substances with multiple structural features, such as sponge-like structures, perforated sheets, aggregate of spheres, branches and chain-like assemblies etc., is apparent at higher concentrations for both humic samples, showing morphologically new evidence for the dominant view of the humic dual-mode sorption model. With naphthalene introduced, the assemblies of Guanting humic substances clearly become more compact with significantly narrowed branches and less porous the perforated sheet-like structures. It is indica- tive of that smaller nanometer scale rings present along the perforated assemblies could potentially represent hydrophobic domains, which may facilitate the adsorption and aggregation of naphthalene onto the natural particle surfaces and therefore lead to an important role of dissolved humic sub- stances in the sorption of environmental pollutants.
