Methane and sulfide fluxes in permanent anoxia: in situ studies at the Dvurechenskii mud volcano (Sorokin Trough, Black Sea)

The Dvurechenskii mud volcano (DMV), located in permanently anoxic waters at 2060 m depth (Sorokin Trough, Black Sea), was visited during the M72/2 cruise with the RV Meteor to investigate the methane and sulfide release from mud volcanoes into the Black Sea hydrosphere. We studied benthic fluxes of methane and sulfide, and the factors controlling transport, consumption and production of both compounds within the sediment. The pie shaped mud volcano showed temperature anomalies as well as solute and gas fluxes indicating high fluid flow at a small elevation north of the geographical center. The anaerobic oxidation of methane (AOM) coupled to sulfate reduction (SR) was excluded from this zone due to fluid-flow induced sulfate limitation and a fresh mud flow and consequently methane escaped into the water column with a rate of 0.46 mol/m**2/d. In the outer center of the mud volcano fluid flow and total methane flux were decreased, correlating with an increase in sulfate penetration into the sediment, and with higher SR and AOM rates. Here between 50-70% of the methane flux (0.07-0.1 mol/m**2/d) was consumed within the upper 10 cm of the sediment. Also at the edge of the mud volcano fluid flow and rates of methane and sulfate turnover were substantial. The overall amount of dissolved methane released from the mud volcano into the water column was significant with a discharge of 1.4x10**7 mol/yr. The DMV maintains also high areal rates of methane-fueled sulfide production of on average 0.05 mol/m**2/d. However, we concluded that sulfide and methane emission into the hydrosphere from deep water mud volcanoes does not significantly contribute to the sulfide and methane inventory of the Black Sea.

The informal labour market in India : transitory or permanent employment for migrants?

The informal economy is a very important sector of the Indian economy. The National Council of Applied Economic Research estimates that the informal sector - "unorganised sector" - generates about 62% of GDP and provides for about 55% of total employment (ILO 2002, p. 14). This paper studies the characteristics of the workers in the informal economy and whether internal migrants treat this sector as a temporary location before moving on to the organised or formal sector to improve their lifetime income and living conditions. We limit our study to the Indian urban (non-agricultural) sector and study the characteristics of the household heads that belong to the informal sector (self-employed and informal wage workers) and the formal sector. We find that household heads that are less educated, come from poorer households, and/or are in lower social groups (castes and religions) are more likely to be in the informal sector. In addition, our results show strong evidence that the longer a rural migrant household head has been working in the urban sector, ceteris paribus, the more likely that individual has moved out of the informal wage sector. These results support the hypothesis that, for internal migrants, the informal wage labour market is a stepping stone to a better and more certain life in the formal sector.