Primary production, effect radiation

A month-long study of the effects of ultraviolet radiation (UV) on phytoplankton and ice-algae collected from Arthur Harbor, Anvers Island, Antarctica, was carried out during November-December 1987. The parameters studied included primary production rates, photosynthetic... 

Potential Effects of UV on Primary Production. The results of the study carried out at Palmer Station during Novcmbcr-Dccembcr 1987 provided insight into the potential deleterious effects of enhanced UV radiation. These results showed an enhancement of the photosynthctic rates in the tanks where UV-A and UV-B were excluded. Conversely, rates of production were much lower under ambient and enhanced UV... 

Comparison with other Studies. How do the results of our investigation compare with similar studies Our results corroborate the data provided in a similar study of the effect of UV-B on primary productivity in the southeastern Pacific Ocean (35). In the latter study, it was noted that enhanced UV-B radiation caused significant decreases in the productivity of surface and deep samples. Compared to ambient, primary productivity decreased with increasing doses of UV-B. In another study in which in situ experiments using natural Antarctic phytoplankton populations, it was noted that incident solar radiation significantly depressed photosynthetic rates in the upper 10-15 meters of the water column (36). It was also found that the spectral region between 305 and 350 nm was responsible for approximately 75 percent of the overall inhibitory effect. 

In the direct effect of ionizing radiation on DNA, radical cations are the primary products (Chap. 12). For this reason, their reactions are of considerable interest. Obviously, photoionization (e.g., at 193 nm) and laser multi-photon excitation leads to such species (e.g., Candeias and Steenken 1992b Malone et al. 1995 Chap. 2.2). Base radical cation electron pairs have been proposed to be the first observable intermediates with a lifetime of 10 ps for Ade and four times longer for the other nucleobases (Reuther et al. 2000). Radical cations are also assumed to be intermediates in the reactions of photosensitization reactions with qui-nones, benzophenone, phthalocyanine and riboflavin (Cadet et al. 1983a Decar-roz et al. 1987 Krishna et al. 1987 Ravanat et al. 1991, 1992 Buchko et al. 1993 Douki and Cadet 1999 Ma et al. 2000). Nucleobase radical cations may be produced by electrochemical oxidation (Nishimoto et al. 1992 Hatta et al. 2001) or with strongly oxidizing radicals (for a compilation of their reduction potentials see Chap. 5.3). Rate constants are compiled in Table 10.3. 

Plant productivity is determined by factors such as plant species composition, moisture, soil fertility, growing season length, and solar radiation—many of which are affected by human activities. All else equal, increases in primary productivity and production of plant tissues will lead to increases in soil C stock, while decreases will lead to decreases in soil C stock. The rate of change in soil C stock is determined by the difference between C inputs and outputs, as well as the turnover times of the soil C, which are often not known. Here we review briefly how some environmental factors are expected to alter productivity and explore how the effects on stock depend on the number of soil carbon pools and their turnover times. 

Ionizing radiation arises from the photoelectric effect, the Compton effect, or ion pair production. Gamma radiation causes local and intense damage and may break chemical bonds. The primary target is the deoxyribonucleic acid (DNA) of the micro-organism. In addition, free radicals may be formed, such as peroxides that result in intracellular and extracellular peroxides by a chain reaction that causes damage. 

The indirect action of radiation on aqueous alcohol leads to changes which are broadly similar in pattern to the direct-action effects described for pure alcohols. Hydrogen, aldehydes, glycols, and acids are formed in general, although it has not been established that acids are primary products. ... 

R.A. Kinzie III, A.T. Banaszak, M.P. Lesser (1998). Effects of ultraviolet radiation on primary productivity in a high altitude tropical lake. Hydrobiologia, 385,23-32. 

M.J. Behrenfeld, J. Hardy, H. Gucinski, A. Hanneman, H. Lee, A. Wones (1993). Effects of ultraviolet-B radiation on primary production along latitudinal transects in the South Pacific Ocean. Mar. Environm. Res., 35, 349-363. 

E.W. Helbling, V.E. Villafane (2001). UVR effects on phytoplankton primary production A comparison between Arctic and Antarctic marine ecosystems. In D.O Hessen (Ed.), UV-Radiation and Arctic Ecosystems (pp. 203-226). Springer-Verlag. M. Blumthaler, W. Rehwald (1992). Solar UV-A and UV-B fluxes at two alpine stations at different altitudes. Theor. Appl. Climatol, 46,39-44. 

Experimental studies have shown that vinylene concentration is constant with sample thickness (Costa et al. 1998). Alkyl macroradicals produced by gamma radiation are homogeneously distributed within the UHMWPE component because vinylene are the primary product of interaction between polyethylene and high-energy radiation. In e-beam irradiation, the radical distribution is a function of depth because of the cascade effect, which leads to a subsurface maximum in the absorbed dosage. 

When a substance burns it gives rise to four primary products smoke, products of combustion, light and heat. Although smoke is one of the products of combustion because of its particular effects it is convenient to consider it separately. Light and heat are both electromagnetic radiations differing only in their wavelength, but their roles in a fire are such that they are best dealt with separately. 

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