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11.
The use of organic matter from compost to promote the catalytic photodegradation of micropollutants by solar light appears to be environmentally promising. However, quantitative evaluation of the photodegradation potential of the compost is needed. Our goal was to measure the formation rate of hydroxyl radicals and singlet oxygen, two strongly oxidant species, from irradiated compost organic matter. These two reactive species were photogenerated in all of our extracts regardless of the origin of the compost or the extraction procedure; however, their formation rates increased with composting time. Two herbicides and a fungicide were successfully photodegraded when irradiated with simulated or natural solar light in the presence of the compost organic matter or compost suspensions. For reasons of simplification and ease, the use of the latter is recommended in practice. 相似文献
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Spatial and temporal distribution of atmospheric mercury species over the Adriatic Sea 总被引:2,自引:0,他引:2
Field measurements of atmospheric mercury and related species were carried out during an intensive cruise campaign performed
over the Adriatic sea from October 26th to November 12th, 2004 on board the R/V Urania. Hg0 ranged between 0.8 and 3.3 ng/m3 with an average of 1.6 ± 0.4 ng/m3 over the entire period. Hg(II) concentrations ranged from 0.1 to 62.8 pg/m3 with an average of 6.7 ± 11.7 pg/m3 whereas Hg-p levels were in a range of 0.04 and 51 pg/m3 with an average of 4.5 ± 8 pg/m3. Higher Hg0 and Hg-p concentrations were observed in the Gulf of Venice and Gulf of Trieste due primarily to air masses transported from
the mainland reflecting the contribution from anthropogenic sources. In contrast, higher Hg(II) concentrations observed during
the first period of the cruise campaign were likely due to the occurrence of photo-oxidants production which are the main
players of the gas phase oxidation of to Hg(II)(g). These findings have been confirmed by the backward trajectories analysis of air masses crossing the studied area during
selected days. 相似文献
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Jan Weber Jana Klánová Crispin J. Halsall 《Environmental pollution (Barking, Essex : 1987)》2009,157(12):3308-3313
Here we investigate the photodegradation of structurally similar organophosphorus pesticides; methyl-parathion and fenitrothion in water (20 °C) and ice (−15 °C) under environmentally-relevant conditions with the aim of comparing these laboratory findings to limited field observations. Both compounds were found to be photolyzed more efficiently in ice than in aqueous solutions, with quantum yields of degradation being higher in ice than in water (fenitrothion > methyl-parathion). This rather surprising observation was attributed to the concentration effect caused by freezing the aqueous solutions. The major phototransformation products included the corresponding oxons (methyl-paraoxon and fenitroxon) and the nitrophenols (3-methyl-nitrophenol and nitrophenol) in both irradiated water and ice samples. The presence of oxons in ice following irradiation, demonstrates an additional formation mechanism of these toxicologically relevant compounds in cold environments, although further photodegradation of oxons in ice indicates that photochemistry of OPs might be an environmentally important sink in cold environments. 相似文献
15.
Criegee intermediates (CIs), also known as carbonyl oxide, are reactive intermediates that play an important role in the atmospheric chemistry. Investigation on the structures and reactivity of CIs is of fundamental importance in understanding the underlying mechanism of their atmospheric reactions. In sharp contrast to the intensively studied parent molecule (CH2OO) and the alkyl-substituted derivatives, the knowledge about the fluorinated analogue CF3C(H)OO is scarce. By carefully heating the triplet carbene CF3CH in an O2-doped Ar-matrix to 35 K, the elusive carbonyl oxide CF3C(H)OO in syn- and anti-conformations has been generated and characterized with infrared (IR) and ultraviolet-visible (UV-vis) spectroscopy. The spectroscopic identification is supported by 18O-labeling experiments and quantum chemical calculations at the B3LYP/6-311++G(3df,3pd) and MP2/6-311++G(2d,2p) levels. Upon the long-wavelength irradiation (λ > 680 nm), both conformers of CF3C(H)OO decompose to give trifluoroacetaldehyde CF3C(H)O and simultaneously rearrange to the isomeric dioxirane, cyclic-CF3CH(OO), which undergoes isomerization to the lowest-energy carboxylic acid CF3C(O)OH upon UV-light excitation at 365 nm. The O2-oxidation of CF3CH via the intermediacy of CF3C(H)OO and cyclic-CF3CH(OO) might provide new insight into the mechanism for the degradation of hydro-chlorofluorocarbon CF3CHCl2 (HCFC-123) in the atmosphere. 相似文献