The groundrot item flag would do this, but you'd have to do some tweaking to get the object to have a timer value. Would be a fairly simple addition to the do_drop code to have it set the object timer to something like 10 when the person drops it if the item meets your limit setting. Once that's done, any item dropped with that flag will decay until destroyed. The shorter the timer value, the sooner it happens. But a timer value of 0 won't decay, so if you want it to be virtually instant, set the timer to 1.
Alternately, you could tweak do_drop to vaporize a groundrot item immediately. A bit easier to do, and would be a truly vicious shock to the player doing it
Either way, this is going to require some sort of code tweakage since it's not normal for any object to get a timer value by default, at least not that I recall.