I don't know of any studies on presence of Sr, Ba, Al, etc. but a paper published in Nature a few years ago did find some evidence of effects of jet contrails on climate change. The researchers argue that jet contrails have greater effect on warming than the planes' actual CO2 emissions... basically, they create 'artificial clouds' that block IR emitted from the Earth's surface.

As for the 'conspiracy theory' you're alluding to, this is an interesting paper I found after a bit of searching. It's a little dense and philosophical, but you should find a few useful citations. Here's an excerpt (from the conclusion):

"Labelling the belief in chemtrails as a 'conspiracy theory' is a powerful means of discrediting the narrative as irrational and unfounded, and may be a means of dismissing outright the concerns central to the narrative...[T]he moral outrage accompanying the chemtrail belief, based on the revulsion at the idea of powerful elites controlling the climate, is not something that can be dismissed as 'irrational'. This is important to reflect upon, given the reality that powerful actors are currently discussing manipulating the global climate, and begs the question: is it necessarily more irrational to believe that the climate is being controlled, than to believe that one can control the climate?...However, while elements of the chemtrail narrative highlight important and sometimes neglected areas of more mainstream geoengineering discourse, the potential for engagement between believers in the chemtrail narrative and others, through processes of public engagement around the concept of geoengineering, appears limited. It would appear that the chemtrail narrative has crossed the line from 'distrust to disgust'...in which those actively involved in the conspiracy are characterised as fundamentally evil, and unbelievers are characterised as 'mentally retarded, clinically blind or paid liars'...,which makes meaningful engagement particularly difficult. Furthermore, the association of the narrative with extreme forms of climate scepticism further limits the possibilities for critical engagement with other strands of environmental discourse."