The junk dealer has loads of cargo that he wants me to throw into the lake. The lake was back where there was that big boss battle against the tentacle thing right? I went north of north knot city but there is no way to get back to the lake. I know I can teleport back using Fragile, but I lose all of the cargo so there is no point in using her.
There are multiple lakes in the game where you can dispose of cargo. One of which you will need to use at some stage or other. There is a body of water near enough to the junk yard. Closer to south knot city. You will see it on your map. Load up the cargo and head down there to throw it into the lake.