A wetland CAN be part of a riparian zone, but the term refers to the area around a river or stream, and does not mean it is necessarily a wetland.
In the US, the term wetland has a legal definition:
“those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions.”
In practice, this means soil saturated with water for at least a week or two during the growing season.
Riparian zones often have some wetlands, but few are all wetland.
You should talk about the role of wetlands in maintaining water quality as part of any discussion of the role of properly maintained riparian zones, but be aware that the term wetland and riparian zone are not synonyms.
