Ozone is a crucial air pollutant that damages human health and vegetation. As it related to the photo-oxidation of nitrogen oxides volatile organic compounds, summertime reduction these precursors primary focus current ozone mitigation strategies. During pollution episodes in eastern China, an observed accumulation daily total oxidants (Ox=NO2+O3</sub...

[1] We evaluate the sensitivity of tropospheric OH, O3, and O3 precursors to photochemical effects of aerosols not usually included in global models: (1) aerosol scattering and absorption of ultraviolet radiation and (2) reactive uptake of HO2, NO2, and NO3. Our approach is to couple a global 3-D model of tropospheric chemistry (GEOSCHEM) with aerosol fields from a global 3-D aerosol model (GOC...

In 1939, Hill (1) reported the fundamental discovery that isolated chloroplasts possess the ability to affect a portion of the over-all reaction of photosynthesis; namely, the photolysis of water. In the original experiments of Hill, ferric oxalate was used as the hydrogen acceptor. During the past 20 years, a variety of substances has been found to function as oxidant for the Hill reaction (2)...

Aromatic hydrocarbons are rated amongst the most important classes of compounds with regard to the formation of photo-oxidants in the lower atmosphere. A recent theoretical study [1] using a trajectory model approach estimated the aromatic hydrocarbons to be responsible for about 40 % of the anthropogenic ozone formation in north-western Europe, their contribution to the total nonmethane hydroc...

Polyoxometalates (POM) have a rich and promising photochemical behavior. Upon illumination at the O M CT band (i.e., in UV and near-visible area) become powerful oxidizing reagents able to oxidize various organic compounds. In the process POM undergo stepwise reduction accumulating electrons that can be subsequently delivered, via thermal reactions to a variety of oxidants. This way a great var...

Experiments to determine the concentration of photochemically available Fe in ambient aerosol samples were carried out using a novel photochemical extraction procedure. Ambient aerosol samples, which were collected on Teflon filters, were suspended in an aqueous solution within a photochemical reactor and irradiated. Under these conditions, which were favorable to the photochemical weathering o...

Volatile organic compounds (VOCs) have been determined to be human risk factors in urban environments, as well as primary contributors to the formation of photochemical oxidants. Ambient air quality measurements of 54 VOCs including hydrocarbons, halogenated hydrocarbons and carbonyls were conducted in or near 13 urban locations in the United States during September 1996 to August 1997. Air sam...

Short-time exposure to air pollutants and in particular to sulfur dioxide, nitrogen oxides and photochemical oxidants may cause respiratory symptoms similar to acute bronchial asthma. In healthy adults however the concentrations required to evoke significant bronchial obstruction lie still above the level of atmospheric air pollution usually observed in our country. In contrast patients with pr...

Abstract. Volatile organic compounds (VOCs) tend to be consumed by atmospheric oxidants, resulting in substantial photochemical loss during transport. An observation-based model was used evaluate the influence of VOCs on sensitivity regime and mechanisms ozone formation. Our results showed that a VOC-limited based observed VOC concentrations shifted transition with initial concentration (PIC-VO...

The heat, ultraviolet and rihoflavin-sensitized visible inactivations of taka-amylase A are strongly inhibited by the presence of its substrate. The stabilization of the secondary structure of enzyme protein by the conformation change due to the formation of enzyme-substrate and -product complexes is responsible for the protection of enzyme from the heat inactivation. The photoinactivations are...