Spawn particles once every second whilst holding an item.

[edgy socket]

you can use something like https://maven.fabricmc.net/docs/fabric-api-0.129.0+1.21.8/net/fabricmc/fabric/api/event/lifecycle/v1/ServerEntityEvents.html#EQUIPMENT_CHANGE to detect item holding

but you'll need to count the ticks yourself and spawn particles

[real bison]

have a counter. every tick it increases counter. if counter is 20 (game runs at 20 ticks/second) do the particle spawning. then reset counter back to 0