You can disable the jobs by executing the following SQL from Management studio:
UPDATE SCHEDULE SET enabled = 0 WHERE TypeFullName Like '%Purge%'
subsequently, you should examine which of the tabled exaggerate size, e.g by running (separately) the following commands in Host :: SQL text box:
SELECT Count(*) FROM {databaseOwner}{objectQualifier}SiteLog
SELECT Count(*) FROM {databaseOwner}{objectQualifier}EventLog
SELECT Count(*) FROM {databaseOwner}{objectQualifier}ScheduleHistory
SELECT Count(*) FROM {databaseOwner}{objectQualifier}SearchItemWords
Also make sure, the database gets backed up frequently with truncating the transaction log, if using full recovery scheme.