which ND filter used in these photos?

which ND filter used for these photos? i am sure a polarizer used and most probably ND too.

i am intending to buy ND filter(s) but i have read that there are soft and hard and split type, is there any guide that explain the use of each and usualy what is the most used one? also looking to buy the one that can attach it to the lens and the CIP on it.

i dont care alot for vignetting, i can crop or fix it, so slight vigentting is not a big deal.

thanks for your help

here is the gallery

http://www.pbase.com/ricardoalves/iceland

--
http://www.pbase.com/shg2