Experimental verification of anomalous chloride enrichment related to methane hydrate formation in deep‐sea sediments

Abstract

Anomalous chloride concentration enrichment has been detected in marine sediments comprising methane hydrates (MHs). In this study, we designed an electric circuit system linked to the high-pressure resistance cell in which the chloride ion concentration can be directly measured within reliable accuracy under in situ conditions of the deep-sea floor pressure and temperature. Chloride concentration increased under a fast MH formation rate, but no noticeable concentration change was detected under a relatively low-rate. Furthermore, we suggested that the MH formation rate must be maintained at least $10 2 mol m À2 yr À1 so as to efficiently enrich chlorides and retain the acquired chlorinity. The present experimental system dose not fully reflect the relatively minor effective variables such as vertical advections in real system, but the results seem to be sufficient for revealing chloride enrichment phenomena induced by fast MH formation rate with free methane gas.

Spectroscopic Observation of Na Cations Entrapped in Small Cages of sII Propane Hydrate

“…However, Figure again confirms that the salting-out exclusion cannot cause a chemical shift change. As mentioned in many studies, the ions that do not participate in hydrate formation should be excluded to the outside of the hydrate phase. , Because the ions remained in the ice (Ih) phase even after the hydrate formation, the surroundings of these excluded ions might not be changed. Thus, the chemical shifts of 23 Na in NaCl (NaOH) + H 2 O + C 3 H 8 and NaCl (NaOH) + H 2 O are expected to be same.…”

Molecular Dynamics of Carbon Sequestration via Forming CO2 Hydrate in a Marine Environment

“…During hydrate formation, salt ions compete with guest molecules for water molecules, and when salt ions are dissolved by water, the number of hydrogen bonds between water molecules decreases. Therefore, it is difficult for water molecules to form cage clusters through hydrogen bonding interactions and the cage stability is reduced …”

“…Therefore, it is difficult for water molecules to form cage clusters through hydrogen bonding interactions and the cage stability is reduced. 26 Even though numerous experimental studies have demonstrated that electrolytes inhibit hydrate formation, the microscopic mechanisms are still not fully understood because of the time and space constraints of monitoring methods. Many scientists have used MD simulations to investigate hydrate formation because they are an effective tool for revealing the microscopic nature of hydrates at the molecular scale.…”