the ppm scale is defined as the ration ratio between a variation of resonance frequency and a reference resonance frequency. The ppm range of 13C is bigger than ppm range of 1H because little perturbation of electronic environment of 13C is bigger compared to the major the contribution of Larmor frequency. The gyromagnetic ratio is 4 times lower for 13C. So if the perturbation is identical for 1H and 13C, the range have to be 4 times bigger. We see that is 10 times bigger, so an other contribution exist, likely a more susceptibility of electronic density to be disturbed...
