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Resolving CO2 and methane hydrate formation kinetics 总被引:1,自引:0,他引:1
Michael Golombok Erik Ineke Juan-Carlos Rojas Luzardo Yuan Yuan He Pacelli Zitha 《Environmental Chemistry Letters》2009,7(4):325-330
We analyse the kinetics of CO2 and methane hydrate formation. The characteristic formation times are associated with different steps of the formation process.
Conditions for minimising these rate times are identified while maintaining a regime where CO2 hydrate is formed and methane remains predominantly gaseous. This involves a rapid pressurisation routine and accesses points
well above the phase boundary in order to enable faster kinetics. Conditions for optimising rates and times, to obtain maximum
CO2 uptake with respect to CH4, were identified as (1) stirring faster than 1,000 rpm, (2) rapid pressurisation to a partial pressure of around 50 bar for
CO2 and (3) re-use of contaminated as opposed to fresh water. 相似文献
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Luzardo OP Almeida-González M Henríquez-Hernández LA Zumbado M Alvarez-León EE Boada LD 《Chemosphere》2012,88(3):307-315
The population of the Spanish archipelago of the Canary Islands has been studied in depth regarding its levels of contamination by organochlorine pesticides (OCs) and polychlorinated biphenyls (PCBs). Foodstuffs of animal origin, such as milk, are prominent contributors to the body burden of these contaminants. As this population presents one of the highest milk-intake in Spain and Europe, we evaluated the level of OCs and PCBs in 26 commercially available brands of milk (16 conventional and 10 organic brands) present in the market of these Islands, in order to estimate the relevance of milk as a source of these chemicals for the Canary population. Our findings showed that hexachlorobenzene, trans-chlordane, and PCB153 were present in almost all the samples with independence of the type of milk. For both types of milks, the concentration of OCs was very low, showing organic milks lower levels than conventional ones. As a consequence, the estimated daily intake for OCs was lower than the tolerable daily intake (TDI) established by International Agencies. The levels of PCBs in milk were also found to be very low, but, in this case, the situation was the opposite: there were higher levels of PCBs in organic than in conventional brands of milk. Unexpectedly, levels of dioxin-like PCBs (DL-PCBs) reached values higher than 25 pg WHO-TEQ g−1 fat in percentile 75 for both types of milk indicating the existence of a number of brands of milk highly contaminated by these toxicants. Consequently, the population who consume the most contaminated milk brands could have estimated daily intakes well above the recommended TDI (2 pg WHO-TEQ kg−1 b.w. d−1) established by European Union Authorities. These results are of concern if we consider the well known adverse health effects exerted by dioxin-like compounds. 相似文献
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