Respiration and assimilation processes reflected in the carbon isotopic composition of atmospheric carbon dioxide

This paper presents diurnal variations of concentration and carbon isotopic composition of atmospheric carbon dioxide caused by respiration and assimilation processes. Air samples were collected during early and late summer in 1998 in unpolluted area (village Guciow located near the Roztocze National Park, SE Poland) in three different environments: uncultivated field on a hill, a meadow in the Wieprz river valley and a forest. The effect is very strong during intensive vegetation growth on a sunny day and clear night. The largest diurnal variations in atmospheric CO2 concentration and its carbon isotopic composition in June above the meadow were about 480 ppm and 10‰, respectively

Diurnal variations and vertical distribution of δ13C, and concentration of atmospheric and soil CO2 in a meadow site, SE Poland

We provide the results of 24-hour observations made in a meadow site located in a small river valley in Central Europe. Samples of atmospheric air were taken from three horizons: near the soil (0.05 m), in the grass (0.5 m) and above the meadow (2 m) at two-hour intervals. At the same time, samples of soil air were collected from two horizons: -0.1 and -0.5 m. We have found a variation of δ13C above the ground from -6‰ during the day to -20‰ late at night accompanied by variations in CO2 concentration from 270 ppm during the day, to various levels late at night at different heights above the ground. The maximum concentration was 1430 ppm at the ground level. The correlation coefficient between δ 13C and reciprocal of concentration was the highest (R2 = 0.984) for the samples collected 2 m above the ground, the regression line clearly indicating CO2 mixing from the two sources: atmospheric and biogenic reservoirs. The intercept of the mixing line yields δC = -23.0‰ for the biogenic CO2. In contrast, the diurnal variations in the soil were relatively small, δ13C varied from -21.6 to -23.4‰, while CO2 concentration from 4300 to 8200 and from 24 700 to 34 500 ppm at depths of 0.1 m and 0.5 m respectively, which is less than 2-fold. Small diurnal variations are characteristic of dry soils, where δ13C is weakly correlated with CO2 concentration (in our case R2 was 0.30 and 0.54, respectively)

O caráter religioso e profano das festas populares: Corumbá, passagem do século XIX para o XX

Neste artigo, analisamos as características das festas populares de São João e do Carnaval em Corumbá (MS, antigo MT), na passagem do século XIX para o XX. A população pobre vivia a cidade à sua moda, produzindo lazer e festas, espaços de intensa sociabilidade. Os rituais que as constituíam situavam-se entre os universos religioso e profano, o que conferia maior autonomia para a população operar nesses espaços. Assim, elementos simbólicos, como a água e o fogo, sofreram re-atualizações (re-significações), consideradas supersticiosas pela Igreja Católica.<br>This article analyses the characteristics of popular feasts of Saint John and the Carnival in the city of Corumbá, in the state of Mato Grosso do Sul, formerly state of Mato Grosso (Brazil), during the turn of the 20th century. The poor population lived in the city in its own way, producing leisure and feasts, spheres of intense sociability. The constituting rituals fall within religious and secular universes, conferring greater autonomy to the population to act in these spheres. Thus, symbolic elements such as water and fire undergo resignifications considered superstitions by Catholic Church

Degassing of metamorphic carbon dioxide from the Nepal Himalaya

International audienceGeothermal activity is common at the foot of the Higher Himalaya near the Main Central Thrust (MCT), Nepal Himalaya. We have sampled hot springs along a 150 km stretch of the Himalayan front and find that they carry large fluxes of CO2 derived from metamorphic reactions. Hot spring fluids are saturated with CO2, have [DIC] from 1.3 to >100 mmol kg-1 and have δ13CDIC values from -13‰ to +13‰(PDB). Analysis of CO2 released by decrepitation of fluid inclusions from syn- and postdeformational quartz veins indicate that crustal fluids had δ13C from -15‰ to +2‰(PDB), consistent with production of CO2 from both thermal decomposition of organic matter and decarbonation at depth. Modeling of the hot spring fluid compositions indicates that they are strongly degassed. Combining our degassing calculations with estimates of the fraction of hydrothermal alkalinity in local rivers shows that the metamorphic degassing flux of CO2 in the 32,000 km2 Narayani basin of the central Himalaya is >1.3 × 1010 mol a-1, exceeding the calculated consumption of CO2 by chemical weathering for the Narayani River basin by a factor of four. Our study implies that the net impact of Himalayan orogenesis on the carbonate-silicate geochemical cycle is not large-scale drawdown of CO2 because the weathering sink is substantially offset or even exceeded by the metamorphic source