$sth_detections = $dbh->prepare("$QUERY2") || die $DBI::errstr;
for ...
my $city = $city[$i];
my $station = $station[$i]; 

$sth_detections->bind_param(":city", $city);
$sth_detections->bind_param(":station", $station);
$sth_detections->execute;
@row = $sth_detections->fetchrow;