Don't blame the copper! Pegasus sinks are imported and it is very difficult to know if there are impurities in the copper that might be leaching out and causing the smell. The imported sinks often tell you to dry the sink after each use and wax it periodically. Your sink in the bathroom is also imported and likely lacquered, hence no smell. You might try using a paste wax on the kitchen sink to see if that helps. I have made copper sinks using pure US virgin copper for 14 years - no smell.
This is a quote from the Pegasus use and care: It is recommended that cutting, preparing, or otherwise allowing acidic foods to come into contact with the copper sink be kept to a minimum. This is because acidic substances chemically react to the copper if left in contact with it over a period of time. Such acidic foods include tomatoes, citrus fruits, and citrus juices. The solution to safely handling these foods in a copper sink is to run warm water while cutting, cleaning, or preparing them. Applying a gentle car or brass wax will maintain the natural, gleaming color of the copper sink.