Nitrogen Runoff from Tunnel Blasted Rocks- a Large-Scale Test

摘要

Eight tunnel blasted rock samples were washed five times in 10 m~3 containers to calculate the runoff potential of nitrogen from unexploded remains of the ammonium nitrate slurry explosive in rock piles. During the first wash, 65% of total nitrogen was washed off. The average concentrations of NH_4~+ and NO_3~- in the first wash water were 46 mg N/L and 58 mg N/L, respectively, being reduced to 2.5 and 1.2 mg N/L after the last wash. The average runoff of total nitrogen from the blasted rocks was 24.2 g N/ton, being 14.7% of nitrogen in the loaded explosives. pH was high (range 8.1 to 11.8) resulting from shotcrete spill, pushing the NH_4~+/NH+3 equilibrium toward the toxic NH_3. The consequences of runoff from blasted rock piles may be damaging for water quality and biology in small recipients, and abatement measures should be assessed.