As open office environments go, they all suck IMO, and I’m backed by numerous scientific studies on this. However, I don’t see them going away either, so we’re stuck having to do the best of a challenging situation.
From your short description, it seems you have a more serious problem though. It kinda sounds like you are a “free resource” available for anyone’s request to do ad-hoc work? How easy is it for you to decline a request or say “Yes, I’ll get that to you by Thursday next week”?
Your field is Marketing. As the sole responsible person, you should set the marketing plan and priorities for the coming period. In collaboration with the business, of course, but you need to know what is in the pipeline and how important things are relative to one another. Campaigns, advertisements, social media posts, mailers, billboards, public or customer events, get it all on the calendar and into the marketing plan. Requests that align with the overall plan should get priority, anything else will be in your “best effort” backlog.
One thing that is (hopefully) understood in financial organizations: money. Another thing to try is to put a price tag on your services. For any work request, be sure to get a project code or cost center to charge your hours to. This should bring clarity to where your efforts are going. If your company is not currently set up for internal charging or time tracking, make up a scheme on your own in Excel or Numbers. Track your time to create a baseline over a couple of weeks. Hard data and facts will come in handy for a discussion with your line manager.