whoops, sorry i found this post a little late, hopefully i'm not too late
With a sandbed of around an inch, you aren't going to have any anaerobic spots in your sandbed. It takes a depth of 4" or more to create a significant anaerobic zone in the very bottom.
Adding some live sand to your sandbed "could" disrupt the bacteria population, but it's not necessarily a fatal move to your tank. Besides, since you're adding live sand, the disruption might be minimal. I think the worst that would happen is your tank might go through a mini-cycle, should the bacteria in the sand that gets buried under the new sand dies. But again if you've got a decent amount of liverock, and you're adding live sand, then this cycle should be minimal if it happens at all.
One question this raises though, is why add some sand to a 1" sand bed? Or, I should ask how much are you adding? There are basically two desirable sand bed depths, 0.5-1", or 4"-5". If you're anywhere in between, it's too shallow to create anaerobic zones, but deep enough to trap all kinds of detritus and other wastes (not letting them be removed by your protein skimmer), and polluting your tank. So if you're adding a bunch of sand, enough to make the leap from your current 1" to the 4"-5" level, then that's cool, you'll have yourself a nice deep sand bed and natural nitrate removal after a while. But if you're only adding a little bit, tread carefully, as it sounds like your approaching that undesirable sand bed depth. Hope this helped!