What is the fine-grained topic of the following text: The relative abundance is doubtless influenced by high concentrations in Winnipeg (clusters in other towns such as The Pas likewise influence these calculations), but there is a suggested peak of abundance in the agricultural belt from Winnipeg south to Morden, as well as from Manitou west to the southwest corner. Only return the topic.
Relative abundance of a certain element in different regions of Winnipeg.