That is a good question.
It is probably true in some cases. The impact of climate change on groundwater is felt mainly when it comes to replenishment. We are having shorter winters, less snow melt in the spring and lower levels the following summer. That can all have effects on water chemistry. When water levels are lower, the aerated zones are different and the microorganism populations that transform pollutants may therefore also be different.
To date, very little research has been done on this. In general, little research is being done on groundwater. So we still don't know a lot about how groundwater quality and pollutant content will change in the coming decades.