Surface density and total mass of planetesimals with various disc properties. The left panel shows the surface density of the planetesimals (solid lines) and the corresponding approximations by Eq. (30) (dotted lines). The vertical solid and dotted lines represent r_SL and r_PIM, respectively. The vertical lines with different Z_ς,0 and Σ_g,1au overlap with those of the fiducial case. The right panel shows the total planetesimal mass (solid curves) and the corresponding approximations by Eqs. (25) and (30) (dashed curves).