Source-specific risk assessment for cadmium in wheat and maize: Towards an enrichment model for China

•Cadmium soil pollution and crop accumulation are detectable on national level in China.•Mining activities and sewage irrigation dominate to Cd pollution in China.•Cd pollution in Southwest of China, Middle Yellow River region and North China plain should be taken more seriously.•Cd enrichment models differ with investigated sites and are influenced by pollution sources.