A ground level accidental release of 0.5 g/s occurs at a 4 m height in terrain with a roughness length of zo = 0.01m. Assuming a wind speed of 1 m/s what is the maximum ground level concentration 4 km downwind estimated from the gross screening method and from the gaussian plume equation? [Answers: 25 µg/m3 , 0.56 µg/m3 ]