Preheat the oven to 325°F. Grease 9 by 9 glass pan. In a bowl, mix together the flour, sugars, and salt. Measure 1/2 cup of this mixture and reserve. Add buttermilk, oil and egg to the flour mixture. Stir until moistened. Dissolve baking soda in water and add to the flour mixture. Stir gently and fold in the blueberries. Spread evenly in the prepared pan. Add the pecans and cinnamon to the reserved dry ingredients, sprinkle over the top. Bake at 325°F oven for 45 minutes or until inserted wooden pick comes out clean