There isn't a way to do this by URL, but you can have a different set of columns for each folder.  These are also stored in the user's attributes, with the key "[SETTINGS]ColumnDisplayxxx" (where xxx is the entry id for the folder).  This settings is read recursively up the tree, so you don't have to set it on every folder.  I believe Web Access and the desktop client both write to this attribute when you change your folders, so you should be able to make your changes that way.  You can turn on the per-folder columns in WebLink with the attribute "[SETTINGS]UniqueFolderColumns" set to "Yes".

WebLink does cache user settings, so you'll need to recycle the app pool to see changes take effect.

Also, be aware that for version 9.1, Web Access and the desktop client write column settings to a new user attribute (to add support for multi-column sort) and the data is not in a backwards-compatible format.  Until we upgrade WebLink to read and understand this new data, you'll need to set the attributes with a pre-9.1 client.

Update: I've been informed that although this is how it is supposed to work, there is an active bug report that WebLink doesn't in fact read these settings.  It's SCR 106990 for your reference.