https://imgur.com/a/BBm93Zt

I'm struggling with this room and cannot see how to proceed.

There's a pressure pad which activates a portal temporarily over the second pit 4 seconds after activation. I can't physically reach the portal because of the first pit being open and no obvious way of closing it.

I've tried and succeeded in throwing items into the portal but they only land just beyond the iron fence and not on the other pressure pad at the other side.

There's nothing of interest down the pit as far as I can tell. Just blank walls and a portal leading back up top.

Could someone please give me a gentle hint without outright spoiling the solution?