It's not clear from your post if you're getting the requests or the responses?
If you're getting the requests, the source addresses are spoofed and abuse contacts for the source IPs won't help. You need to rate limit your responses so you're not a good reflector and the abuse will stop, mostly. If you have good relations with your transit providers, you can maybe try to get them to try to track the source of the traffic, but if you had that kind of pull, you probably wouldn't ask here.
If you're getting DNS replies for questions you didn't ask, abuse contacts should help... But I wouldn't expect much unless the rates are really high.