Sunlight intensity

The reaction mechanisms by which the VOCs are oxidized are analogous to, but much more complex than, the CH oxidation mechanism. The fastest reacting species are the natural VOCs emitted from vegetation. However, natural VOCs also react rapidly with O, and whether they are a net source or sink is determined by the natural VOC to NO ratio and the sunlight intensity. At high VOC/NO ratios, there is insufficient NO2 formed to offset the O loss. However, when O reacts with the internally bonded olefinic compounds, carbonyls are formed and, the greater the sunshine, the better the chance the carbonyls will photolyze and produce OH which initiates the O.-forming chain reactions. 

Photolysis direct photochemical transformation t,/2(calc) = 21 h, computed near-surface water, latitude 40°N, midday, midsummer and photolysis t,/2 = 160 d and 200 d in 5-m deep inland water body without and with sediment-water partitioning, respectively, to top cm of bottom sediment over full summer day, 40°N (Zepp Schlotzhauer 1979) t,/2 = 21 h, atmospheric and aqueous photolysis half life, based on measured sunlight photolysis rate constant in water adjusted for midday summer sunlight at 40°N latitude and t,/2 = 63 h after adjusting for approximate winter sunlight intensity (Howard et al. 1991) t,/2 = 160 d under summer sunlight in surface water (Mill Mabey 1985) ... 

Sandworm FLUORANTHENE Amphibians embryos and larvae embryos exposed from early development through hatching under artificial ultraviolet light newly hatched larvae were exposed outdoors in varying sunlight intensity levels >1000 LC50 (96 h) 2... 

The diurnal variations in mean hourly average oxidant concentration are illustrated in Figures 4-26 and 4-27. Several factors influence the shapes of these curves. The primaiy influence is that of sunlight intensity, inasmuch as photons in the ultraviolet are responsible for the primary photochemical process that leads to ozone formation. Note that the St. 

Louis curve for June 1966 is broader than that for Los Angeles in August. This is explained by differences in sunlight intensity distribution throughout the day. 

Clearly, the concentrations of pollutants in ambient air, and hence their impacts, are determined not only by their rates of emissions but also by the nature and efficiencies of their chemical and physical sinks, e.g., chemical transformations, as well as wet and dry deposition to the earth s surface. To a large extent, these competing processes are affected not only by direct dispersion and transport but also by such meteorological factors as temperature, sunlight intensity, and the presence of temperature inversions as well as clouds and fogs. 

For example, some may have short lifetimes and/or nonuniform distributions and hence be sensitive to such factors as the location of the emissions, sunlight intensity, season, etc.)... 

When the Arctic polar vortex is not denitrified, more gas-phase HNO, is available as the sunlight intensity increases, and this photolyzes, regenerating N02 ... 

The study was designed to examine the effect of sunlight intensity, the importance of volatilization and the extent of partitioning of fenitrothion and degradation products into sediment, plants and fish under field conditions. 

Finally, note that the rate of photochemical reactions, including those involving photoformed OH, is maximum in the water surface layer and decreases with the water column depth because of decreasing sunlight intensity. Accordingly, the... 

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