An eco-balance approach to the evaluation of historical changes in nitrogen loads at a regional scale

Historical changes in nitrogen flows of a municipality from 1912 to 2002 were analyzed to evaluate the relation between production and environmental pollution. The system comprised human, livestock and farmland subsystems. The indicators used in this study were production, surplus nitrogen (N) on farmland and total systems, and flow indices. Flow indices consist of cycling index (CI), export index (EI), and loss index (LI). CI was defined as the proportion of nitrogen cycled in the system to the total system throughflow, EI as nitrogen exported from the system, and LI as nitrogen lost from the system (sum of field surplus nitrogen, nitrogen in non-utilized excreta, and N₂O and NH₃ emissions).     

Elevation of lipid peroxide level and production of hydroxy lipids in cultured Hepa-T1 cells by oxidative stressors

ABSTRACT:   In order to investigate the relationships between levels of lipid peroxides (LPO), hydroxy lipids (L-OH) and of antioxidative enzymes in live fish, cultured cells from tilapia liver (Hepa-T1) were treated with oxidative stressors, 2,2'-azobios(2-amidino-propane) dihydrochloride (AAPH) and H₂O₂. By treating with 5 mM AAPH, LPO and L-OH of the cells significantly increased time-dependently. In particular, L-OH increased from 7.6 ± 0.7 to 23.6 ± 1.8 nmol/mg protein after 2 h of treatment, and synchronously the glutathione peroxidase (GPx) activity of the cells increased from 259 ± 106 to 1970 ± 135 mU/mg protein. In the case of H₂O₂, however, no elevation of L-OH was observed. In this case, catalase (CAT) and superoxide dismutase (SOD) activities increased time-dependently. Especially, after 2 h exposure, the CAT activity increased remarkably from 217 ± 21 to 2510 ± 120 mU/mg protein, though the GPx activity did not change significantly. These results suggest that the elevation of the L-OH level is closely associated with the elevation of GPx activity, but not with that of CAT or SOD. However, when vitamin E-enriched Hepa-T1 cells were treated with AAPH and H₂O₂, the production of LPO and L-OH was suppressed significantly. The findings suggest that vitamin E also plays an important role in the levels of the oxidation products in vivo .     

Greenhouse gas emissions after a prescribed fire in white birch-dwarf bamboo stands in northern Japan,focusing on the role of charcoal

Forest fires affect both carbon (C) and nitrogen (N) cycling in forest ecosystems, and thereby influence the soil–atmosphere exchange of major greenhouse gases (GHGs): carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). To determine changes in the soil GHG fluxes following a forest fire, we arranged a low-intensity surface fire in a white birch forest in northern Japan. We established three treatments, having four replications each: a control plot (CON), a burned plot (BURN), and a plot burned with removal of the resulting charcoal (BURN-CHA). Soil GHG fluxes and various properties of the soil were determined on four or five occasions during a period that spanned two growing seasons. We observed increased concentrations of ammonium-N (NH₄-N) in BURN and BURN-CHA after the fire, while nitrate–N (NO₃-N) concentration was only increased in BURN-CHA after the fire. The soil CO₂ flux was significantly higher in CON than in BURN or BURN-CHA, but there was no difference in soil CH₄ uptake between the three treatments. Moreover, the N₂O flux from BURN-CHA soil was slightly greater than in CON or BURN. In BURN-CHA, the soil N₂O flux peaked in August, but there was no peak in BURN. We found temporal correlations between soil GHG fluxes and soil variables, e.g. soil temperature or NO₃-N. Our results suggest that environmental changes following fire, including the increased availability of N and the disappearance of the litter layer, have the potential to change soil GHG fluxes. Fire-produced charcoal could be significant in reducing soil N₂O flux in temperate forests.