Added nitrate (or nitrite, or ammonia, for that matter) is something to be avoided in storm-water runoff, NOx is something to be avoided in the air. How do we judge this concrete based on these mutually exclusive goals?

I'm helping a local park get started with an outdoor classroom (no computers outside), but we are hoping to have a "rainy-day room" with a few computer games. Since we expect younger children we were going to have the donated computers (i.e. older) running on ubuntu with Google Earth; the plan is to have prepared a KML of natural areas within and near the park with lots of things for the children to click. We also wanted to have a television with the auto-focus 'microscope' at http://www.eyeclops.com/. The possibility of Sketchup or Scratch has been discussed.