My question Jow is how exactly are you deriving your conclusion as to the weight needed of whatever substance is attributed to creating these "persistent jet contrails"?
For those things to stay suspended at the altitude they are, would require that whatever they are made of not exceed the density of a cloud. If they were spraying anything heavier, it would fall out of the sky. Yet we never see these things descending to the surface, do we? They just stay up there at the altitude they are created at, and drift along with the prevailing winds.
Have you ever looked in to how much clouds weigh and their density? If not, you should. A half gram per cubic meter is roughly what they weigh. Sometimes it's more, sometimes a bit less, but not by much. Which is why I use .5 grams/CM. Ie: it's at the low end of the range.
...and when you do the math and calculate just how mabny cubic meters of area these things cover, the weight adds up to more than any plane can carry. *
Also, these things have to have a certain density to them, or they would not be visible from so far away. If they were just spraying a light mist of something, how would we even see it from a minimum of 6 or 7 miles away?
Another thing, if they were spraying "gases", as
@arminius tried to say, they would just disperse into the surrounding atmosphere. The same as gases coming from a smokestack do.
So you gotta think in terms of what could they "spray" that would stay together like cloud does, and be light enough to stay suspended for a good period of time without dispersing into the surrounding air.
* that's where ya gotta use a flight tracker to ID the planes and determine the altitude and distance of the plane. Once you know that, you can determine the size of the trail you are seeing. Once you know the size, you can calculate its volume in cubic meters.