To answer your question- a lot of chemistry in the sediment is affected by oxygen. I am interested in iron, and iron can have two forms in the sediment- iron OXIDES which have oxygen attached to the iron molecule, and reduced iron which has no oxygen. This reduced iron would really like to have oxygen attached to it, because it is a more stable molecule in this form- so when it comes in contact with oxygen, it grabs those oxygen molecules and forms iron oxide. I don't want this to happen, because I want to know how much of each type is in the sediment, so I filter my samples under nitrogen gas, because nitrogen gas isn't reactive like oxygen- iron won't bind to nitrogen like it does with oxygen. If I didn't care as much about iron, then I wouldn't need to filter my samples under nitrogen gas.
To answer your question- a lot of chemistry in the sediment is affected by oxygen. I am interested in iron, and iron can have two forms in the sediment- iron OXIDES which have oxygen attached to the iron molecule, and reduced iron which has no oxygen. This reduced iron would really like to have oxygen attached to it, because it is a more stable molecule in this form- so when it comes in contact with oxygen, it grabs those oxygen molecules and forms iron oxide. I don't want this to happen, because I want to know how much of each type is in the sediment, so I filter my samples under nitrogen gas, because nitrogen gas isn't reactive like oxygen- iron won't bind to nitrogen like it does with oxygen. If I didn't care as much about iron, then I wouldn't need to filter my samples under nitrogen gas.
Thanks for your question!