"How was it possible, I asked myself, to walk for an hour through the woods and see nothing worthy of note? I, who cannot see, find hundreds of things to interest me through mere touch. I feel the delicate symmetry of a leaf. I pass my hands lovingly above/about the smooth skin of a silver birch."
Nicely written by the way.
Ok, I'm assuming that in your story you don't actually touch the bark of the tree. If that's the case, I would definitely use "above". If you do touch the bark however, I think I would use "about". Which one is it?
As for your first question:
"Also, the water in the lakes is now contaminated. This not only has affected people’s drinking water, but also has caused plenty of fish in the lake to die. Though the factories have been spending a large quantity of money to improve this situation, the residents there are still complaining."
to improve: the factories are spending money and are trying to improve the situation, but are not necessarily succeeding.
improving: the factories are spending money and have managed to improve the situation somewhat.
That's my take on it.
Student or Learner