That's zinc oxide.
Thanks everyone for your replies. In the end I am happy with the image and it has turned out very close to how I felt about it at the time. Rather than pre-visualisation I prefer to go to a location and see what emotions it evokes in me rather than go with preconceived ideas especially as in this instance I had never been to this location before. I did know that I would be dealing with backlit Autumn foliage and chose a time to promote this. If I revisit a location I may pre-visualise how I wish an image to turn out but on many occasions this leads to disappointment Producing images in the manner of various well known landscape photographers is not something I am interested in no matter how much I may admire their images but looking at how they may handle aspects of photography like luminosity in water or portraying movement in an image has made me question and sometimes change my practice. Knowing that their is another approach usually starts me experimenting. My present infatuation with moving water has taken 15 months of experimentation.It would appear that contemporary landscape photography does not exist in this context UNLESS SOMEONE WANTS TO ENLIGHTEN ME and that the judges in this competition were just a little sloppy.Ken