Freshwater systems act as reservoirs storing ancient dissolved carbonates lacking radiocarbon; fish absorb this old carbon, artificially aging human bones.
Yes. Most of the research on C14 dating since its inception has concentrated on quantifying this for different environments, sample types, and dates, or quantifying other effects that give results other than a smooth exponential decay. I'm not clear why this was published. Any C14 lab is aware of this sort of issue. There are also non-C14 techniques available for human remains, e.g. ESR (electron spin resonance) dating.
I remember reading about it as a kid, in 1990s creationist books that were attempting to argue that carbon dating couldn't be trusted and the world was actually only 6,000 years old.
Yeah I grew up in a religious household. A reoccurring theme was about how scientists didn't have a clue about most things. Carbon dating was high up on the list of stuff "scientists were wrong about".
Yes, but for their young earth creationist beliefs to be valid, the errors from carbon dating would need to be far larger than the errors caused by effects described in this article, and other means of dating would need to be ignored.
It is not purporting to show it as 'new'.